Mechanisms in cardiovascular diseases: how useful are medical textbooks, eMedicine, and YouTube?

Abstract

The aim of this study was to assess the contents of medical textbooks, eMedicine (Medscape) topics, and YouTube videos on cardiovascular mechanisms. Medical textbooks, eMedicine articles, and YouTube were searched for cardiovascular mechanisms. Using appraisal forms, copies of these resources and videos were evaluated independently by three assessors. Most textbooks were brief in explaining mechanisms. Although the overall average percentage committed to cardiovascular mechanisms in physiology textbooks (n = 7) was 16.1% and pathology textbooks (n = 4) was 17.5%, there was less emphasis on mechanisms in most internal medicine textbooks (n = 6), with a total average of 6.9%. In addition, flow diagrams explaining mechanisms were lacking. However, eMedicine topics (n = 48) discussed mechanisms adequately in 22.9% (11 of 48) topics, and the percentage of content allocated to cardiovascular mechanisms was higher (15.8%, 46.2 of 292) compared with that of any internal medicine textbooks. Only 29 YouTube videos fulfilled the inclusion criteria. Of these, 16 YouTube were educationally useful, scoring 14.1 ± 0.5 (mean ± SD). The remaining 13 videos were not educationally useful, scoring 6.1 ± 1.7. The concordance between the assessors on applying the criteria measured by κ score was in the range of 0.55–0.96. In conclusion, despite the importance of mechanisms, most textbooks and YouTube videos were deficient in cardiovascular mechanisms. eMedicine topics discussed cardiovascular mechanisms for some diseases, but there were no flow diagrams or multimedia explaining mechanisms. These deficiencies in learning resources could add to the challenges faced by students in understanding cardiovascular mechanisms.

cardiovascular mechanisms are integral components in understanding pathophysiological changes of diseases and in linking basic and clinical sciences in a meaningful way (20). They also enable learners to examine the etiology and contributing factors of cardiovascular diseases as well as the chain of changes caused by the disease processes at molecular, cellular, organ, and body system levels (7, 36). Cardiovascular mechanisms can also provide an explanation for the patient's presenting symptoms and elicited clinical signs. Therefore, mechanisms represent a system of casualty outlining processes caused by a disease at its different stages and providing an explanation for the changes. Mechanisms could also accommodate not just basic sciences but also biopsychosocial and behavioral aspects related to cardiovascular diseases (7, 5, 30).

Considering the educational outcomes obtained from learning mechanisms of diseases, most medical curricula are enforcing mechanisms in their teaching/learning approaches. For example, in problem-based learning (PBL), case-based learning, task-based learning, and related activities, many schools have adopted mechanisms in their case template (22, 39). The educational outcomes that can be obtained from mechanisms include 1) enabling students to explain their hypotheses for the patient's problems identified; 2) encouraging students to integrated knowledge from basic and clinical sciences as well as biopsychosocial issues in mechanisms; 3) stimulating students to explore pathophysiological changes at molecular, cellular, organ, and body system levels; and 4) using basic sciences to interpret patient's symptoms, clinical signs, and the results of clinical investigations (5, 20, 36).

With the introduction of integrated and self-regulated learning to most medical schools such as PBL and case-based learning, medical students tend to use a range of learning resources such as Google, YouTube, and eMedicine (1, 2, 4, 6, 9, 22, 37). This does not necessarily mean a shift from using recommended or prescribed textbooks. Despite some limitations, textbooks remain one of the key learning resources, but most student rely, in addition, on online resources such as eMedicine and YouTube to enhance their understanding and consolidate the knowledge they need for their learning issues (14). eMedicine is one of the largest online clinical resources available to medical professionals, medical students, and the public. It comprises >6,800 articles, each of which is associated with 1 of 62 clinical subspecialty textbooks (41). Also, eMedicine topics are authored by board-certified consultants, and the articles are peer reviewed by several experts to which the article belongs. YouTube is the largest internet video-sharing site and is a useful tool in social communication, advertising, and promoting learning resources to the public and students (19). Although a few studies have shown that YouTube videos could be educationally useful, other studies have reported concerns about misleading information included in YouTube videos (4, 6, 25, 26).

The aim of this research was to evaluate the usefulness of the learning resources commonly used by students including medical textbooks, eMedicine, and YouTube videos on cardiovascular mechanisms, with particular emphasis on the clarity, quality, and percentage of contents committed to cardiovascular mechanisms. These resources were selected because they represent common resources used by medical students to prepare their learning issues. The research question for the study was as follows: how useful are medical textbooks, eMedicine (Medscape) topics, and YouTube videos in learning cardiovascular mechanisms? The focus was on the clarity, quality, and adequacy of contents of mechanisms provided in these resources.

METHODS

Medical Textbooks

Searching for textbooks.

The aim of this search was to obtain a representative sample of textbooks in physiology, pathology, and internal medicine to describe the clarity and adequacy and if there were any deficiencies in the contents on mechanisms of cardiovascular diseases. The Google Book search engine was used to search for textbooks covering human physiology, pathology, and internal medicine. The terms used in the search were “physiology” and “human physiology,” “pathology,” and “internal medicine”. Textbooks in English published from 2007 onward were selected. Only textbooks intended for undergraduate medical students were included; textbooks written for specialties in physiology, pathology, internal medicine, or other health professionals were not included. Study guides or companion books were excluded. Additionally, the same search terms were used to search Amazon (http://www.amazon.com) and Barnes & Noble (http://www.barnesandnoble.com/) websites. Medical textbooks on human physiology, pathology, and internal medicine were used in this study. These textbooks embodied a representative sample of undergraduate medical textbooks prescribed in these programs and comprise the following: 1) they are prescribed in most medical schools worldwide, 2) they are regularly updated and several editions have been produced over the years, 3) they are among the bestseller medical textbooks as per Amazon and the publishers' websites, and 4) they are reviewed in prestigious medical journals such as the British Medical Journal, Journal of the American Medical Association, and New England Journal of Medicine.

Evaluation tool.

To standardize the evaluation of the information on mechanisms, quantity was calculated from the actual page content and percentage of content devoted to mechanisms, reflecting the commitment of the authors to provide learners with an adequate understanding of the topic (12). The percentages were calculated by dividing the actual page count by the total number of pages committed to cardiovascular diseases/topics and multiplying by 100. The total number of images and tables in each chapter were identified and counted. Images and tables explaining mechanisms/pathogenesis were counted, and the percentages were calculated by dividing the actual images or tables by the total number of images or tables in the chapter and multiplied by 100. The clarity, quality, and adequacy of mechanism contents were ranked using a scale of 1–3 (where 1 = poor, 2 = average, and 3 = adequate/optimum level).

Piloting the evaluation.

The aim of piloting was to introduce the evaluators to the tool, ensure that they were able to use it, and identify any inconsistencies among the evaluators that might necessitate improvement of the tool (44). Before the tool was applied, three chapters (other than those included in the study) were evaluated by the three evaluators for their content on mechanisms. The results from the three evaluators were placed on Excel sheets and were discussed in a meeting. Inconsistencies and areas that were difficult to assess were resolved through discussion until a final agreement was reached. The process was repeated by evaluating three other chapters, and the agreement between the evaluators was calculated again.

Assessing the textbooks.

A total of 65 chapters from 17 textbooks (7 textbooks on human physiology, 4 textbooks on pathology, and 6 textbooks on internal medicine) were committed to cardiovascular diseases/system and blood vessels. These chapters were evaluated by the three evaluators independently. The results from each evaluator were placed on Excel sheets. The findings were discussed among the evaluators. The agreement between the three evaluators was calculated using Cohen's κ interrater correlation.

eMedicine Cardiovascular Topics

Selection of topics.

eMedicine (www.emedicine.com) was searched on October 12, 2013 for cardiorespiratory topics. The aim of this search was to obtain a representation of the cardiovascular topics commonly used by undergraduate medical students. The medical textbooks searched in this study were used in identifying these topics. A list showing these cardiovascular topics and mechanisms was created and used in guiding the search of the eMedicine website. Advanced topics and those required at the postgraduate level were not included. To ensure that all evaluators were criticizing the same content, PDF copies for each article (n = 48) were printed out from the eMedicine (Medscape) website on that day.

Evaluation tool.

To ensure consistency among evaluators, appraisal forms were constructed for this purpose. The forms used in evaluation were similar to those discussed for medical textbooks. Due to the continuous changes and updating/editing of eMedicine articles, the evaluators were informed to use only the material given to them and not to consult articles on the website.

Piloting the evaluation.

Before the scoring system was applied to the eMedicine topics, the study was piloted. A total of 10 topics (other than those included in the study) were randomly selected and used for this purpose. The assessors applied the scoring system independently. None of the assessors discussed their findings or the outcomes of their work. An Excel sheet was then produced, summarizing the three assessor's work, and the findings were discussed in a meeting. In this discussion, reasons for inconsistencies were identified and discussed. This process helped in improving the form as well as training the assessors on how to critically evaluate each article. The three assessors independently applied the scoring system for another 10 articles. The number of medical diagrams used in these topics to explain mechanisms were also identified and counted. Thus, contents of mechanisms were examined for content congruent with current needs in integrated undergraduate medical curricula.

Assessing the articles.

The three assessors then evaluated the topics from eMedicine (Medscape) independently. Topics that were difficult to evaluate and/or when there were disagreements among assessors were discussed in a meeting. Consistency among the three assessors was measured using Cohen's κ interrater correlation (21, 43).

YouTube Videos on Cardiovascular Mechanisms

Selection of videos.

From October 1 to October 15, 2013, the YouTube website (www.youtube.com) was searched using the following key words: “cardiovascular mechanisms,” “cardiovascular pathogenesis,” “concept map cardiovascular,” “physiology mechanisms,” “heart diseases mechanisms,” “heart diseases pathogenesis,” and “concept maps heart diseases.” In the YouTube search, quotation marks were used with these terms to specify that these terms must be present. Only videos in the English language were identified, and the related URL was recorded. The three assessors independently using the search key words conducted the search, and the search results were evaluated and used to compile a common pool that was used in further analysis. The inclusion criteria were videos covering mechanisms or pathogenesis of the cardiovascular diseases in adults. Videos were excluded if they were 1) not in the English language, 2) an advertisement or news, 3) discussing signs or symptoms of diseases affecting the cardiovascular system, 4) about patients with cardiovascular diseases reflecting on their experiences or roles, 5) a lecture on a cardiovascular disease, 6) about drugs used in the treatment of cardiovascular diseases, or 7) about a clinical examination of the cardiovascular system. Duplicated videos were excluded, and repeats were treated as a single file for analysis. The repeat file with the greatest number of hits was used for the analysis. For each video, the following data were collected: title, duration of the video, number of days on YouTube, total number of viewers, and name of the uploader/creator (organization, group of people, one person). Because the number of days on YouTube varied widely among videos, it was decided to calculate viewership per day as a more accurate parameter compared with total number of viewers. The viewership per day is the ratio of number of viewers to the number of days a video is on YouTube. The number of days was calculated from the day of uploading on YouTube up to October 7, 2013. This calculation of viewership per day was conducted for each video.

Evaluation tool.

The criteria used for the evaluation of videos have been described in detail in an earlier work (4, 6) with some modification to suit this study. In summary, the design of the criteria was based on four main domains: video content, technical aspects, authority/creator, and pedagogy used. The items in the criteria were grouped under two categories: major and minor. Major criteria comprised the following: 1) the video uses vibrant animations or a flow diagram to demonstrate the mechanism, 2) the contents about the mechanism are scientifically correct, 3) the images are clear, 4) the topic is clearly presented and is engaging, and 5) sounds are clear and the background is free from noise. Minor criteria comprised the following: 1) the video covers the topic identified in the title, 2) the video is designed at the level of undergraduate medical students, 3) the time to download is reasonable (∼5–10 min at the maximum, not uninterrupted, or there was no challenge to download as reported by the three evaluators), 4) the educational objectives are stated, and 5) the creator/or the organization providing the video is mentioned. These criteria were used to categorize videos into educationally useful and noneducationally useful videos. “Educationally useful” means that the video provides scientifically correct and up-to-date knowledge and its contents are accepted by educators in other teaching institutes and match with current information in the literature. As per the basis of the evaluation criteria, educationally useful videos should fulfill the four domains: scientific content, technical aspects, authority/creator, and pedagogy used. Two scores were allocated for each item in major criteria, and one score was allocated to each item under minor criteria. If an item was fulfilled, an allocated score was given; if an item was not fulfilled, a zero was given. No half scores were used. As per our previous research work, educationally useful videos should fulfill all major criteria items as the minimum requirements plus at least three items from minor criteria (4, 6).

Piloting the evaluation.

Before the tool was applied, the criteria were piloted. A total of 20 videos (other than those identified) were randomly selected and used for this purpose. The criteria were applied independently by the three assessors. None of the assessors shared their findings or discussed the outcome of their evaluation. An Excel sheet covering the results from the three evaluations was then discussed in a meeting. Agreement among the assessors was >95%. The findings were discussed among the researchers. The criteria items were tested again independently by the three assessors using another 20 videos. The videos were then rated independently by the three assessors. If videos were difficult to classify or when there was a disagreement that arose among assessors, evaluators reviewed such videos in a meeting and reached a final agreement.

Assessing the videos.

The three evaluators independently evaluated the videos covering the cardiovascular mechanisms. Only 29 videos fulfilled the inclusion criteria. The data were entered using Microsoft Excel 2010 (Microsoft, Redmond, WA) and were checked before any analysis was conducted. Agreement between the evaluators was calculated using Cohen's κ interrater correlation (21, 43).

Statistical Analysis

Analysis was conducted using SPSS software (version 18.0 for Microsoft Windows, SPSS, Chicago, IL), and results were reported as means, SDs, percentages, and minimums and maximums. t-Tests and ANOVA were conducted to determine significant differences (32, 40). To assess the degree to which different raters agreed in their assessment decisions, Cohen's κ for interrater reliability was used to assess interrater reliability (21, 43).

RESULTS

Medical Textbooks

The search ended with the identification of seven textbooks on human physiology, four textbooks on pathology, and six textbooks on internal medicine commonly used in teaching in undergraduate medical courses (Table 1). The 17 textbooks met the search criteria and were obtained for further assessment. The number of chapters on cardiovascular diseases/system and blood vessels in the 17 textbooks was 65. The percentage of cardiovascular mechanism content in physiology textbooks ranged from 5.4% [4 of 74, Preston and Wilson (31)] to 28% [14 of 50, Mulroney and Myers (29)], in pathology textbooks from 7.6% [4.5 of 59, Underwood and Cross (38)] to 24.0% [24.5 of 102, Rubin et al. (34)], and in internal medicine from 0.9% [1.5 of 152, McPhee et al. (28)] to 10.1% [29 of 285, Longo et al. (27); Table 1]. The overall average for cardiovascular mechanisms was 16.1% (99.5 of 618) in the seven textbooks on physiology, 17.5% (64 of 364) in the four textbooks on pathology, and only 6.9% (79.7 of 1,150) in the six textbooks on internal medicine. The percentage of figures committed to explain cardiovascular mechanisms in the physiology textbooks ranged from 7.2% [7 of 97, Preston and Wilson (31)] to 30% [9 of 30, Mulroney and Myers (29)]. In the pathology textbooks, the percentage of figures committed to cardiovascular mechanisms ranged from 5.2% [3 of 57, Underwood and Cross (38)] to 24% [12 of 50, Rubin and Reisner (33)]. In the internal medicine textbooks, the percentage of figures committed to cardiovascular mechanisms ranged from 0.0% [0 of 3, McPhee et al. (28)] to 9.7% [17 of 179, Longo et al. (27)].

Table 1.

Summary of cardiovascular mechanisms in medical textbooks

Authors	Reference	Discipline	Chapter	Pages on Mechanisms	Total Pages	Percentage of Mechanisms	Figures and Tables on Mechanisms	Total Figures and Tables	Percentage of Mechanism	Content Clarity	Quality	Adequacy	Comments
Widmaier et al.	42	Physiology	Cardiovascular physiology	19	81	23.4	21 figures and 0 tables	79 figures and 15 tables	26.5 and 0	3	2	2	Key mechanisms are provided with several flow diagrams. However, mechanisms are not integrated with pathology and clinical aspects.
Sherwood	35	Physiology	Cardiac physiology	23	86	26.7	16 figures and 2 tables	70 figures and 9 tables	22.8 and 22.2	3	3	2	Excellent resource for physiological mechanisms. However, mechanisms are not integrated with pathological and clinical aspects.
Barrett et al.	8	Physiology	Cardiovascular physiology (2 chapters)	8.5	95	8.9	14 figures and 0 tables	93 figures and 27 tables	15.0 and 0	1	1	1	Less focus has been given to mechanisms.
Mulroney and Myers	29	Physiology	Cardiovascular physiology (2 chapters)	14	50	28	9 figures and 0 tables	30 figures and 0 tables	30 and 0	3	3	2	Excellent resource for mechanisms, but there are no integration with pathological and clinical aspects.
Costanzo	15	Physiology	Cardiovascular physiology	10	51	19.6	4 figures and 2 tables	21 figures and 6 tables	19.0 and 33.3	3	2	2	Despite the small size of the book, mechanisms were covered and flow diagrams were used.
Preston and Wilson	31	Physiology	Cardiovascular system (5 chapters)	4	74	5.4	7 figures and 0 tables	97 figures and 0 tables	7.2 and 0	1	1	1	Mechanisms were not adequately discussed.
Born and Boulpaep	10	Physiology	Cardiovascular system	21	181	11.6	12 figures and 4 tables	120 figures and 34 tables	10 and 11.7	2	2	2	One of the chapters was committed to mechanisms.
Rubin and Reisner	33	Pathology	Blood vessels and the heart (2 chapters)	16.5	122	13.5	12 figures and 2 tables	50 figures and 10 tables	24 and 20	2	2	2	A well-illustrated resource for learning pathology. However, mechanisms need to be strengthened.
Rubin et al.	34	Pathology	Blood vessels and the heart (2 chapters)	24.5	102	24.0	20 figures and 4 tables	101 figures and 17 tables	19.8 and 23.5	2	2	2	A well-illustrated resource on pathology. However, mechanisms need to be strengthened.
Underwood and Cross	38	Pathology	Cardiovascular system (2 chapters)	4.5	59	7.6	3 figures and 0 tables	57 figures and 8 tables	5.2 and 0	1	1	1	The focus is on clinic-pathological features. Pathogenesis and mechanisms are briefly discussed.
Kumar et al.	24	Pathology	Blood vessels and the heart (2 chapters)	18.5	81	22.8	10 figures and 2 tables	69 figures and 11 tables	14.4 and 18.1	2	2	2	A well-illustrated and comprehensive textbook. The pathogenesis of diseases is clearly provided, but this varied from disease to disease. Flow diagrams are needed.
Kumar and Clark	13	Medicine	Cardiovascular disease	9.25	130	7.1	10 figures and 2 tables	129 figures and 49 tables	7.7 and 4.0	3	2	2	Mechanisms for arrhythmias, heart failure, valvular heart diseases, and systemic hypertension are briefly given.
McPhee et al.	28	Medicine	Heart disease, systemic hypertension, and blood vessels and lymphatic disorders (3 chapters)	1.5	152	0.9	0 figures and 0 tables	3 figures and 27 tables	0 and 0	1	1	1	Although etiology is provided, no pathophysiology or mechanisms are given.
Colledge et al.	23	Medicine	Cardiovascular disease	10	120	8.3	4 figures and 0 tables	105 figures and 130 tables	3.8 and 0	2	2	1	A good textbook for undergraduate students. However, mechanisms are limited to a few diseases.
Longo et al.	27	Medicine	Disorders of the cardiovascular system (27 chapters)	29	285	10.1	17 figures and 3 tables	179 figures and 86 tables	9.4 and 3.4	3	3	2	An excellent resource for clinical medicine. However, mechanisms are limited to certain diseases.
Andreoli et al.	3	Medicine	Cardiovascular disease (11 chapters)	9	166	5.4	2 figures and 1 table	79 figures and 60 tables	2.5 and 1.6	1	1	1	An excellent resource for clinical medicine. However, mechanisms are limited to certain diseases.
Goldman and Ausiello	18	Medicine	Cardiovascular disease	21	297	7.0	9 figures and 2 tables	195 figures and 124 tables	4.6 and 1.6	2	2	1	Mechanisms were clearly outlined for a number of diseases but were brief. No flow diagrams used.

All internal medicine textbooks except Longo et al. (27) contained little information about cardiovascular mechanisms. For example, the textbook by McPhee et al. (28) focused mainly on clinical findings such as symptoms, clinical signs, investigations, differential diagnosis, treatment, and prognosis. Although the etiology of diseases was provided, no pathophysiology or mechanisms were given. Furthermore, no flow diagrams outlining mechanisms or the pathogenesis of diseases were given. The textbook by Andereoli et al. (3) is a good textbook for undergraduate medical students, but mechanisms were limited to certain diseases. No flow diagrams outlining mechanisms or the pathogenesis of diseases were given. The textbook by Longo et al. (27) scored highest (10.1%) in relation to the percentage of cardiovascular mechanisms. However, more attention to pathophysiology and mechanisms should be considered in future editions. The three textbooks by Colledge et al. (13), Kumar and Clark (23), and Goldman and Ausiello (18) provided cardiovascular mechanisms at relatively reasonable percentages: 8.3%, 7.1%, and 7.0, respectively. Apart from the textbooks by Mulroney and Myers (29), Sherwood (35), Rubin and Reisner (33), and Widmaier et al. (42), none of the remaining textbooks used flow diagrams to outline mechanisms and explain the pathogenesis/pathophysiology of cardiovascular diseases. These textbooks also limited the mechanisms at physiological or pathological aspects with no links to clinical symptoms, signs, or investigation results.

eMedicine Topics

A total of 48 topics from eMedicine (Medscape) on cardiovascular diseases were identified and evaluated for mechanisms (Table 2). The percentage of cardiovascular mechanism content varied from 0% in several topics, such as alcoholic cardiomyopathy, acute coronary syndrome, and hypertensive heart disease, to 41.6% (2.5 of 6) for the topic on renovascular hypertension. The overall average for the cardiovascular mechanisms in the 48 topics was 15.8% (46.2 of 292). Cardiovascular mechanisms were adequately outlined in 22.9% (11 of 48) topics, for example, atrioventricular dissociation, paroxysmal supraventricular tachycardia, premature ventricular contraction, cardiogenic pulmonary oedema, cardiogenic shock, dilated cardiomyopathy, coronary artery atherosclerosis, heart failure, long QT syndrome, pulmonary edema, and infective endocarditis. In the majority of these diseases, no flow diagrams outlining the mechanisms at the body system, organ, cellular, and molecular levels were provided. Table 2 summarizes examples of the limitations/deficiencies observed in some of the mechanisms given.

Table 2.

Summary of cardiovascular mechanisms in Medscape (eMedicine) topics

Topic*	Pages on Mechanisms/Pathophysiology	Total Pages†	Percentage of Mechanism	Number of Diagrams/Tables Covering Mechanisms	Content Clarity	Quality	Adequacy	Comments (Reference)
Atrial fibrillation	1	9	11.1	0	2	2	2
Atrial flutter	1	6	16.6	2 images and 1 ECG tracing	2	2	2	The mechanism given should be updated in light of current publications/research.
Atrial tachycardia	1.5	7	24.2	0	3	3	2
Atrioventricular block	0.5	5	10.0	0	2	2	2
Atrioventricular dissociation	0.5	2	25	0	3	3	3
First-degree atrioventricular block	0.5	4	12.5	0	2	2	2
Long QT syndrome	2	7	28.5	1 table	3	3	3
Paroxysmal supraventricular tachycardia	3	8		2 diagrams plus 11 ECG tracings	2	3	3
Premature ventricular contraction	0.5	2	25	0	3	3	3
Second-degree atrioventricular block	0.5	6	8.3	0	2	2	2
Sinus bradycardia	0.5	2	25.0	0	2	2	2
Sudden cardiac death	1	5	20.0	2 diagrams	2	2	2
Third-degree atrioventricular block	1.5	4	37.5	0	2	2	2
Ventricular fibrillation	0.5	7	7.1	0	2	2	2
Atrial tachycardia	0.5	10	5	0	2	2	2
Wolff-Parkinson-White syndrome	1.5	8	18.7	0	2	2	2
Coronary artery atherosclerosis	2	11	18.1	1 diagram	3	3	3	The mechanism was clearly explained.
Hypertensive heart disease	0	16	0.0	0	1	1	1	The chapter focused on clinical issues and did not address mechanisms.
Noncoronary atherosclerosis	1	7	14.2	0	1	1	1	Mentioned risk factors and did not address mechanisms.
Renovascular hypertension	2.5	6	41.6	3 images	3	2	3	A diagram summarizing the mechanism would be much better.
Risk factors for coronary artery disease	0	7	0.0	1 flow diagram	1	1	1	The discussion focused on risk factors. The author did not explain the underlying mechanisms.
Acute coronary syndrome	0	5	0.0	0				No mention of mechanisms.
Angina pectoris	0.5	5	10	0	2	2	2
Coronary artery vasospasm	0.5	2	25	0	2	2	2
Myocardial infarction	1.5	10	15	0				A diagram linking risk factors with the mechanism of myocardial infarction is needed.
Unstable angina	2	8	25	0	2	2	2	A diagram summarizing mechanisms is needed.
Alcoholic cardiomyopathy	0	7	0.0	0				No mechanism or pathophysiology is provided.
Cardiogenic pulmonary edema	1	3	33.3	0	3	3	3
Cardiogenic shock	2	9	22.2	0	3	3	3
Cor pulmonale	1	8	12.5	0	2	2	2
Dilated cardiomyopathy	1	7	14.2	0	3	3	3	The mechanism is explained, but a diagram is needed to summarize the mechanism.
Heart failure	3	11	27.2	0	3	3	3	The mechanism is well explained, but a diagram is needed to summarize the mechanism.
Hypertrophic cardiomyopathy	0.5	5	10.0	0	1	1	1	The mechanism did not consider the genetic basis for hypertrophic cardiomyopathy. The mechanism did not discuss the molecular pathogenesis of hypertrophic cardiomyopathy and microvascular dysfunction.
Restrictive cardiomyopathy	1	4	25	0	2	2	2
Acute pericarditis	1	9	11.1	0	2	2	2
Constrictive pericarditis	1	4	25	1 diagram	2	2	2
Pericardial effusion	0.5	6	8.3	0	2	2	2
Peripheral vascular disease	1	7	14.2	0	2	2	2
Aortic regurgitation	1	4	25	0	2	2	2	Incomplete. The mechanism given should be updated in light of current publications/research.
Aortic stenosis	0.5	5	10	0	2	2	2
Infective endocarditis	2.5	11	22.7	0	3	3	3	The mechanism is well explained, but a diagram is needed to summarize the mechanism.
Mitral regurgitation	0.5	4	12.5	0	1	1	1
Mitral stenosis	0.5	2	25	0	2	1	1	The underlying mechanism for pulmonary arteriolar constriction is not explained, nor is that hypoxic pulmonary vasoconstriction resides in pulmonary arterial smooth muscle cells. The pathogenesis of right-sided heart failure as the diseases progresses is not explained.
Mitral valve prolapse	0.25	3	8.3	0	1	1	1	No mechanism was given. The authors discussed the natural history of mitral valve prolapse and myxomatous degeneration of collagen fibrils, etc.
Primary pulmonary hypertension	1	4	25	0	2	2	2	Incomplete. The mechanism given should be updated in light of current publications/research.
Pulmonary regurgitation	0.1	1	10	0	1	1	1	No mechanism given. The authors briefly discussed the causes of pulmonary regurgitation.
Pulmonary stenosis	10.5	2	25	0	2	2	2	Incomplete. The mechanism given should be updated in light of current publications/research.
Rheumatic fever	0.4	7	5.7	0	1	1	1	The mechanism did not discuss the pathogenic mechanisms of cross-reactive autoantibodies that target cells, cardiac valves in rheumatic heart disease, and neural cells in Sydenham chorea.

^*Not all cardiovascular topics shown on eMedicine were included in this evaluation. Topics that were too specialized and not needed at undergraduate level were not included.

^†Because of variability in the number of pages allocated to references, the list of references and information about the authors were not counted in the total number of pages.

YouTube Videos

A total of 1,150 YouTube videos were found on the initial search and on applying the inclusion criteria and visual examination of the videos; only 29 videos were found relevant to cardiovascular mechanisms (Table 3). The total duration of these video clips was 414 min and 14 s. The application of the criteria by the three evaluators independently revealed that there were 16 educationally useful videos, scoring 14.1 ± 0.5 (mean ± SD), and the remaining 13 videos were not educationally useful, scoring 6.1 ± 1.72. The difference between the two groups was significant (P < 0.001).

Table 3.

Details about YouTube videos discussing cardiovascular mechanisms identified in the study

Number	Title	URL	Duration	Viewers	Days on YouTube	Viewership per Day	Total score*
1	Pathophysiology of Diastolic and Systolic CHF	http://www.youtube.com/watch?v=OwvrBVw_J4Y	21 min 18 s	38,594	465	82.9	13.67 ± 1.52 (12–15)
2	Congestive Heart Failure - Epidemiology and Pathophysiology (Part 1 of 3)	http://youtu.be/t4e8ucPzRjQ	55 min 7 s	7,723	414	18.6	14.67 ± 0.57 (14–15)
3	Recent insight into the pathophysiology of heart failure	http://www.youtube.com/watch?v=FfPUaoyARtk	30 min 50 s	57	302	0.2	13.33 ± 1.15 (12–14)
4	Pathophysiology of Coronary Artery Disease	http://www.youtube.com/watch?v=pXluagz53kc	20 min 10 s	22,019	465	47.3	14.33 ± 0.57 (14–15)
5	Pathophysiology of Atherosclerosis	http://www.youtube.com/watch?v=rktoF7BHRiQ&list=PL4C480876D0558842	23 min 50 s	22,021	465	47.3	13.67 ± 0.58 (13–14)
6	Pathophysiology of Wolff-Parkinson White Syndrome	http://www.youtube.com/watch?v=_cYThiC-0uk	12 min 37 s	5,052	465	10.8	13.67 ± 0.57 (13–14)
7	Pathophysiology of Cardiac Arrhythmias	http://www.youtube.com/watch?v=_50jV3DKryQ&list=PL4C480876D0558842	20 min 48 s	15,000	464	32.3	13.67 ± 0.57 (13–14)
8	Pathophysiology of Hypertensive Nephropathy	http://www.youtube.com/watch?v=UTLCPpM2vZ8	16 min 41 s	6,421	448	14.3	14.33 ± 0.57 (14–15)
9	Pathophysiology cardiovascular 1 of 5 Risk factors	http://www.youtube.com/watch?v=XPzYkTjN4t4	46 min 22 s	44	60	0.7	14.00 ± 1.00 (13–15)
10	Pathophysiology Cardiovascular 2 of 5 Peripheral artery disease	http://www.youtube.com/watch?v=l3Pcoc3rzR4	28 min 56 s	56	183	0.3	14.33 ± 0.57 (14–15)
11	Pathophysiology cardiovascular 3 of 5 heart disease	http://www.youtube.com/watch?v=F35dTjjGy_Y	38 min 42 s	63	60	1.0	14.67 ± 0.57 (14–15)
12	Pathophysiology of Pulmonary Arterial Hypertension (PAH)	http://www.youtube.com/watch?v=9a4untSzLzg	7 min 19 s	2,305	178	12.9	14.33 ± 0.57 (14–15)
13	Pathogenesis of the Atherosclerotic Plaque and Acute Coronary Syn	http://www.youtube.com/watch?v=upb37rbS1dE	3 min 45 s	26,614	536	49.6	14.33 ± 0.57 (14–15)
14	Shotgun USMLE Renal Cardiac Pathophysiology 1	http://www.youtube.com/watch?v=08QUa6_zRUs	8 min 57 s	155	690	0.22	12.33 ± 1.15 (11–13)
15	Overview of Coronary Artery Disease	http://youtu.be/NZ14XjOQoFY	2 min 58 s	22,242	840	26.4	14.33 ± 0.58 (14–15)
16	Congestive Heart Failure Medical Animation	http://www.youtube.com/watch?v=JJAMYHAwCMs	2 min 23 s	41,231	887	46.4	13.67 ± 0.57 (13–14)
17	Coronary Artery Disease: Cause of Heart Attack - One Minute Medic	http://www.youtube.com/watch?v=LmzfiA1FA-E	1 min 33 s	1,439	155	9.2	8.33 ± 0.57 (8–9)
18	Pathophysiology of CAD/MI Dr. Milind Hanchate	http://www.youtube.com/watch?v=_pOeefZN-Wc	24 min 22 s	26	107	0.24	6.67 ± 1.52 (5–8)
19	“Pathophysiology”, Hypertension	http://www.youtube.com/watch?v=9FuSdiFRK3Y	5 min 4 s	106	19	5.5	6.67 ± 1.15 (6–8)
20	Pathophysiology", Mitral Valve Stenosis	http://www.youtube.com/watch?v=VVlJX-Fd_hI	4 min 18 s	43	49	08	5.33 ± 1.15 (4–6)
21	Atherosclerosis (Understanding Disease: Cardiovascular Medicine)	http://www.youtube.com/watch?v=7JihvMpEP4w	2 min 48 s	36,288	628	57.7	8.67 ± 0.57 (8–9)
22	How Hypertension Affects Cardiac Risk	http://www.youtube.com/watch?v=jSrtyeXM59w	2 min 47 s	102	271	0.37	7.00 ± 0.00 (7–7)
23	“Pathophysiology”, Myocardial Infarction	http://www.youtube.com/watch?v=AquIpZVNc7w	2 min 36 s	340	193	1.7	5.67 ± 1.15 (5–7)
24	Pathophysiology of heart failure	http://www.youtube.com/watch?v=BmkARWsZJAk	3 min 14 s	158	43	3.6	3.33 ± 0.58 (3–4)
25	“Pathophysiology”, Heart Failure	http://www.youtube.com/watch?v=_IPuJvxtwqo	7 min 12 s	27	28	0.9	6.00 ± 1.00 (5–7)
26	Congestive Heart Failure	http://www.youtube.com/watch?v=b2q672lG3Nk	6 min 12 s	20,073	1605	12.5	7.67 ± 1.15 (7–9)
27	Pathophysiology", Valvular Heart Disease	http://www.youtube.com/watch?v=7r4LQtACr-s	1 min 45 s	411	190	2.1	5.67 ± 1.15 (5–7)
28	Pathophysiology of Heart Failure	http://www.youtube.com/watch?v=ECpGxkinwXs	11 min 22 s	4,028	213	18.9	4.33 ± 0.57 (4–5)
29	Hypertension and the Mechanism of Blood Pressure	http://www.youtube.com/watch?v=sJop3D4YSr4	1 min 33 s	1,439	155	9.2	6.33 ± 1.15 (5–7)

Numbers 1–16 comprise educationally useful videos on cardiovascular mechanisms (n = 16). Numbers 17–29 comprise noneducationally useful videos on cardiovascular mechanisms (n = 13).

^*Total score [in means ± SD (minimum–maximum)] was calculated from the scores given by the three evaluators to each video.

CHF, congestive heart failure; USMLE, United States Medical Licensing Examination; CAD, coronary artery disease; MI, myocardial infarction.

The total duration of useful videos was 340 min and 07 s. The total number of viewers of all videos was 274,077. The useful videos attracted 209,597 (76.4%) of all viewers. Table 3 summarizes key information about the 29 videos included in the study.

Except for two videos produced by a pharmaceutical company for educational purposes, all other educationally useful videos were created by physicians and professional bodies/institutions and were linked to organizations such as East Carolina University, Harvard Medical School, and Brigham and Women's Hospital, Boston, Massachusetts. The videos addressed mechanisms of several cardiovascular diseases, including mechanisms and the pathogenesis of systolic and diastolic heart failure, coronary artery disease, atherosclerosis, hypertensive nephropathy, cardiac arrhythmias, and pulmonary arterial hypertension.

The majority of noneducationally useful videos failed two of the major criteria items (23%, 3 of 13), three items from the major criteria (30.7%, 4 of 13), and four or more items from the major criteria (46.1, 6 of 13). Minor criteria items were also not fulfilled in these videos, ranging from one to three items not fulfilled. In other words, these videos failed to provide clear animations or flow diagrams to demonstrate the mechanism, the topic was not clearly presented and was not engaging, and sounds were not clear and there was noise in the background. These videos also failed to address one or two items from the minor criteria items.

Agreement Between Assessors

Agreement between the three assessors was calculated using Cohen's κ interrater correlation. The score was in the range of 0.55–0.95 for cardiovascular mechanisms in textbooks and Medscape. The overall score was in the range of 0.78–0.96.

DISCUSSION

The aim of this study was to evaluate the usefulness of learning resources commonly used by students, including medical textbooks, eMedicine, and YouTube videos, on cardiovascular mechanisms, with particular emphasis on clarity, quality, and percentage of content committed to cardiovascular mechanisms. The author is not aware of any research in the literature addressing this area. A total of 65 chapters from 17 textbooks and 48 topics from eMedicine and 29 YouTube videos were included in this study. Most textbooks were brief in explaining mechanisms of cardiovascular diseases. Although the overall average committed to cardiovascular mechanisms in physiology textbooks (n = 7) was 16.1% (99.5 of 618) and pathology textbooks (n = 4) was 17.5% (64 of 364), there was less emphasis on mechanisms in most internal medicine textbooks (n = 6), with a total average of 6.9% (79.7 of 1,150). Flow diagrams explaining mechanisms were also lacking. Although physiology textbooks allocated a higher percentage of content to mechanisms, the mechanisms in physiology books lacked details about pathological changes at organ and cellular levels. Furthermore, mechanisms in both physiology and pathology textbooks lacked integration of knowledge in relation to patient symptoms, clinical signs, and interpretation of investigation results. Such information will add a meaningful dimension to mechanisms. Unfortunately, internal medicine textbooks did not resolve this area of need and did not give mechanisms priority. Taking these findings together with the lack of flow diagrams explain mechanisms in these textbooks into consideration, it may be necessary, as per these results, that editors and publishers add flow diagrams explaining mechanisms and summarizing the pathophysiology of cardiovascular diseases. The percentage of figures committed to explaining cardiovascular mechanisms in physiology textbooks ranged from 7.2% (7 of 97) to 30% (9 of 30), in pathology textbooks from 5.2% (3 of 57) to 24% (12 of 50), and in internal medicine textbooks from 0.0% (0 of 3) to 9.7% (17 of 179). All internal medicine textbooks except Longo et al. (27) contained little information about cardiovascular mechanisms.

Building mechanisms is a challenging process. For example, there is no definition on what constitutes an ideal mechanism, students usually find building mechanisms not an easy job, PBL tutors are usually not experts in the cases discussed, feel unable to facilitate the discussion of mechanisms, or provide feedback to students on what they have created in the tutorials, and both students and tutors do not know which learning resources they could turn to in regard to identifying and clarifying mechanisms (5).

eMedicine topics discussed cardiovascular mechanisms adequately in 22.9% (11 of 48) of the topics, and the percentage of contents allocated to mechanisms in eMedicine topics was higher 15.8% (46.2 of 292) compared with that of any internal medicine textbook. Cardiovascular mechanisms were clearly outlined for a number of topics, including paroxysmal supraventricular tachycardia, premature ventricular contraction, cardiogenic pulmonary edema, cardiogenic shock, dilated cardiomyopathy, heart failure, long QT syndrome, and infective endocarditis. However, several topics lacked or had poorly provided mechanisms, such as hypertensive heart disease, noncoronary atherosclerosis, risk factors for coronary artery disease, hypertrophic cardiomyopathy, mitral regurgitation, mitral stenosis, mitral valve prolapse, pulmonary regurgitation, and rheumatic fever. More importantly, no flow diagrams or videos explaining mechanisms were included, and the topics were presented in a way similar to that of textbooks. As an online resource, eMedicine should effectively use the technical advantages available to online resource and include videos, educational multimedia programs, or interactive electronic tasks that can deepen the understanding of mechanisms at the body system, organ, cellular, and molecular levels, therefore adding new dimensions to the understanding of mechanisms (16).

Vosky et al. (41), in an innovative study, examined the quality of internet information on pediatrics otolaryngology mainly in Wikipedia, eMedicine, and Medline Plus (41). They found that the content accuracy of eMedicine scored highest (84%, P <0.05) over Medline Plus (49%) and Wikipedia (46%). They concluded that eMedicine has the most accurate comprehensive contents and fewest errors but that the topics were challenging to read and navigate. The results from this study demonstrated that eMedicine cardiovascular topics allocated more contents to mechanisms than any of the internal medicine textbooks. However, topics varied in regard to adequacy of mechanisms, and the contents of several topics lacked clarity and quality of information.

Despite the smaller number of educationally useful YouTube videos identified (16 videos) and the fact that these videos focused on certain cardiovascular diseases, there is no doubt that the animations and use of diagrams in these videos added a unique feature to the understanding of mechanisms that can add to what is learned from textbooks and eMedicine articles. Videos are a medium that can transfer the motion through animations that can help learners to understand complex events (17) and the sequence of changes at the cellular and molecular levels. Being available free on the internet and easily accessible, YouTube videos have become a popular resource used by students (4, 11). The results from this study show that the total duration of useful videos was 340 min and 07 s and that the total number of viewers was 274,077, attracting 209,597 (76.4%) of all viewers, which indicates the interest of viewers in learning about cardiovascular mechanisms from YouTube videos. Reading textbooks and other resources such as eMedicine and review articles along with watching online videos has become a valuable learning strategy among medical students. Therefore, identifying educationally useful resources is essential to ensure quality learning from up to date and scientifically correct resources.

The methods used in this study to assess the textbooks and eMedicine topics aimed at providing a critique of the clarity, quality, adequacy, and percentage of content committed to mechanisms. Three evaluators conducted the assessment of each of these learning resources independently, and the tools used were piloted before their implementation. The interrater agreement among the three evaluators was in the range of 0.55–0.95 for the textbooks and eMedicine and in the range of 0.78–0.96 for the YouTube videos, indicating the reliability of the measures used (21, 32, 40, 43).

The system used in the assessment of the YouTube videos is simple, easy to apply, and covers four key elements, namely, scientific content, technicality, authority, and pedagogy parameters. The criteria system used in this study has shown its capacity to accommodate these four parameters, and the interrater agreement among assessors had κ scores in the range of 0.78–0.96. Piloting the use of the criteria before their implementation to this project has helped in preparing the evaluators on applying the criterion system and, hence, the achievement of the high interrater scores of agreement.

The small number of videos covering cardiovascular mechanisms is a limitation to this study. However, the study was limited to videos in the English language and only those covering cardiovascular mechanisms or pathophysiology. These two factors could have possibly contributed to the small number of videos identified. The study was also limited to YouTube videos, and it is possible that there are other educationally useful videos on other websites, such as those of medical professional societies and medical journals, that were not included.

Based on this study, it is recommended that publishers and editors of undergraduate medical textbooks include mechanisms and flow diagrams outlining mechanisms and showing changes at the body system, organ, cellular, and molecular levels. In addition, authors and producers of digital resources should give more attention to mechanisms and pathophysiological changes of cardiovascular diseases. Innovative ideas that could enable learners to build mechanisms and integrate knowledge in an engaging and interactive way are recommended. Further research is needed to assess the impact of using learning resources demonstrating well-presented cardiovascular mechanisms on students' learning and the impact of using multimedia on cardiovascular mechanisms on students' learning processes and the ability to integrate basic and clinical sciences as well as their clinical reasoning and decision-making skills.

In conclusion, despite the importance of mechanisms in understanding cardiovascular diseases and in explaining the pathophysiological changes, integrating basic and clinical sciences as well as explaining symptoms and clinical signs and results of investigations, there was less emphasis on mechanisms in most internal medicine textbooks, and none of the textbooks used flow diagrams to outline mechanisms or explained the pathogenesis/pathophysiology of cardiovascular diseases. Although the overall average percentage committed to cardiovascular mechanisms in physiology and pathology textbooks was higher than that in internal medicine textbooks, these textbooks limited the mechanisms at physiological or pathological aspects with no links to clinical symptoms, signs, or investigation results. eMedicine topics on cardiovascular diseases described mechanisms adequately for 22.9% (11 of 48) of the topics, and the percentage of content committed to mechanisms was higher than that of any internal medicine textbook. However, some topics did not have mechanisms. Educationally useful YouTube videos on cardiovascular mechanisms, despite their small number, could add useful dimensions to the understanding of mechanisms at cellular and molecular levels. However, these videos focused on a few diseases. Such deficiencies in learning resources may add to the challenges faced by students enrolled in integrated and student self-regulated learning programs.

GRANTS

This work was funded by the College of Medicine Research Center, Deanship of Scientific Research, King Saud University, Riyadh, Saudi Arabia.

DISCLOSURES

No conflicts of interest, financial or otherwise, are declared by the author(s).

AUTHOR CONTRIBUTIONS

Author contributions: S.A.A. conception and design of research; S.A.A. performed experiments; S.A.A. analyzed data; S.A.A. interpreted results of experiments; S.A.A. prepared figures; S.A.A. drafted manuscript; S.A.A. edited and revised manuscript; S.A.A. approved final version of manuscript.