Clinical epidemiology of atrial fibrillation in heart failure in Abeokuta, Nigeria

Abstract

Background

Atrial fibrillation (AF) is the most common sustained cardiac dysrhythmia seen in clinical practice that requires treatment. Data on the burden of AF in patients with heart failure (HF) are generally lacking in Nigeria and Africa.

Objective

This study aimed to characterize the clinical and echocardiographic profiles of patients with AF in our clinical practice.

Methods

An observational hospital-based study was conducted on patients with AF in the setting of HF seen at an urban tertiary hospital in Nigeria over 9 months. All patients had both clinical and echocardiographic evaluations.

Results

A total of 100 cases of AF in HF were recruited for the study. Of these, 54 were men and 46 women. The mean age of the participants was 55.7 (13.3) years (male: 58.8 [10.5], female: 52.1 [15.4] years). The age range was 18 to 86 years for the cohort (male: 32–86 years, female: 18–79 years). Most participants were older than 40 years (88%). Hypertensive heart disease was the most common risk factor, although rheumatic heart disease and thyroid heart disease played a major role in women and most required anticoagulation.

Conclusion

AF in HF in our setting occurred at a younger age compared with data from Western Europe and North America. Women were diagnosed at a younger age because of the risk factors. Hypertensive heart disease was the most common risk factor, and most patients required anticoagulation. Studies are needed to determine the impact of AF on the outcome of HF in our setting.

Key Findings.

• ▪Atrial fibrillation (AT) is present in approximately 12% of patients with chronic and stable heart failure in the study population.
• ▪The mean age of the cohort was 55.7 years, which is lower than the mean age in high-income countries.
• ▪More than 80% of the patients with AF were older than 40 years.
• ▪Hypertensive heart failure is the most common risk factor; however, rheumatic heart disease and thyroid heart disease played a major role in women.
• ▪Most of the patients required anticoagulation.

Introduction

Heart failure (HF) is now a global public health issue.¹ It affects approximately 64 million people worldwide.² The rising prevalence of HF has been linked with increasing life expectancy in many parts of the world and improvement in the management of risk factors for HF, such as hypertension, obesity, and diabetes mellitus.³ Low- and middle-income countries (including Nigeria) bear a large proportion of the burden of HF.² The condition is associated with high morbidity and mortality, high economic cost, high rehospitalization rates, and poor quality of life.^4,5 The in-hospital mortality following admission for HF in sub-Saharan Africa (SSA) ranges between 15% and 35%, whereas approximately 17% and 34% of patients discharged after treatment for acute HF die within 6 months and 12 months, respectively.^6,7 These are higher than statistics from other regions such as the Middle East, South America, and Southeast Asia.⁷ Furthermore, the clinical and social impact of HF is worse in Africa where >80% of patients pay out of pocket.⁸

Atrial fibrillation (AF) is the most common sustained arrhythmia seen in clinical practice worldwide.⁹ In 2017, it was estimated to affect 37.6 million persons globally, including 3.1 million incidental cases.⁹ AF is associated with a higher risk of stroke and other thromboembolic phenomena, HF, renal dysfunction, and dementia.⁹ It is also associated with poor quality of life and increased health care costs.⁹

In SSA, hospital-based studies put the prevalence of AF at approximately 5%.10, 11, 12, 13, 14, 15 It worsens and accelerates the natural history of HF, resulting in increased frequency of hospital admissions or readmissions, longer stays, and mortality.16, 17, 18 The sociodemographic and clinical characteristics of AF in HF have been sparsely characterized in Nigeria. The objective of this study was to describe the clinical epidemiology of AF in patients with HF at the Federal Medical Center, Abeokuta, Nigeria.

Materials and methods

Study design

This was a hospital-based cross-sectional study carried out in the Cardiology unit of the Department of Internal Medicine of Federal Medical Centre, Abeokuta, over 9 months. The Cardiology unit provides medical care for both new and old patients with cardiac disease who are residents of Ogun state, Nigeria, and adjoining states.

Sampling method

Consecutive consenting adult patients (aged ≥18 years) with HF and AF who fulfilled the inclusion criteria were recruited into the study.

Study population

A total of 100 consenting patients with chronic and stable HF with AF (aged ≥18 years) attending outpatient clinics were recruited after satisfying the inclusion criteria. Diagnosis of HF was based on the European Society of Cardiology criteria.¹⁹ Duration of HF was self-reported from the first time the diagnosis was made. Because it was difficult to know the onset of AF in our environment, this was not used as an inclusion criterion. Exclusion criteria were as follows: patients with psychiatric illness, patients with pacemakers, and those with poor echocardiographic window and other arrhythmias such as atrial flutter, atrial tachycardia, multifocal atrial tachycardia, premature ventricular complex, junctional rhythms, and ventricular tachycardia.

Sample size

Using the prevalence of AF of 5.6% in the study by Ajayi and colleagues,¹⁵ a sample of ≥80 was needed to have a confidence level of 95% that the real value is within ±5% of the measured or surveyed value.

Clinical evaluation and data collection procedure

Data were collected using an interviewer-administered questionnaire and a clinical assessment of the study participants. Baseline blood investigations were also carried out on all participants. Blood investigations (fasting blood glucose, electrolyte, urea, and creatinine packed cell volume), lipid profile, and thyroid function tests were performed using standard methods.

Electrocardiography

A resting 12-lead electrocardiogram was done for each participant using a potable Schiller AT-102 model (Schiller AG, Baar, Switzerland) electrocardiograph, and standard calibration was used according to the American Heart Association recommendation. Diagnosis of AF was made if the following features were present on electrocardiogram (ECG): absence of distinct P waves, presence of fibrillatory or “f” waves that are low in amplitude, baseline oscillations, and an irregularly irregular ventricular rhythm. The atrial cycle length (when visible), that is, the interval between 2 atrial activations, is usually variable and >300 bpm.²⁰

Echocardiography

This was performed using the General Electric VIVID T8 machine interfaced with a 3.5 MHz transducer (GE Medical System Co, Ltd, China). Echocardiographic studies were performed per the American Society of Echocardiography recommendations in the left lateral decubitus position.²¹ An average of 3 measurements was taken with simultaneous ECG recording for patients. Measurements of wall thickness, dimensions, volumes, and left ventricle systolic and diastolic functions were obtained according to the American Society of Echocardiography guidelines.22, 23, 24

Ethical considerations

The study observed international ethical principles: voluntary participation, confidentiality of data, beneficence, and nonmaleficence. Adequate information about the purpose of the study and what their participation entailed, including benefits and risks, was given to potential participants.²⁵

Data management and statistics

Data were entered into an Excel worksheet for cleaning before being imported to IBM for social sciences version 22 statistical software for analysis. Categorical variables were presented as proportions and percentages using frequency tables and bar charts as appropriate, whereas continuous variables were summarized as means and standard deviation. Discrete variables, such as number of hospitalization, were represented with frequency (mode) and median. Kolmogorov-Smirnov test was conducted to check for normality. Skewed data were analyzed using median and interquartile range, whereas unskewed data were analyzed using mean.

All statistical analyses were carried out at a level of significance of P < .05.

Results

A total of 100 men and women with AF were enrolled over 9 months. There were 54 men and 46 women. The mean age of the all participants was 55.7 (13.3) years (58.8 [10.5] years for men and 52.1 [15.4] years for women) (Table 1). The age range was 18 to 86 years for the cohort (32–86 years for men and 18–79 years for women). Most participants were older than 40 years (88%). Men were older, and more women were seen in the 18- to 39-year age group (P = .021) (Figure 1). Men attained higher education more than women (P = .003) (Figure 2). There was no statistical difference in their occupation status (when compared according to unemployed, employed, and retired status) (P = .105) (Figure 3).

Table 1.

Baseline characteristics of the participants

Variables	All (N = 100)	Male (n = 54)	Female (n = 46)	P value
Age (y)	55.7 (13.3)	58.8 (10.5)	52.1 (15.4)	.011
Duration of heart failure (mo)	27.04 ± 14.99	24.41 ± 12.88	26.11 ± 14.13	.080
At least 1 hospital admission, n (%)	6 (6.0)	2 (23.7)	4 (8.7)	.127
Body mass index (kg/m2)	27.64 ± 6.47	27.24 ± 4.31	28.16 ± 8.21	.963
CV risk factors and comorbidities
Alcohol use, n (%)	43 (43.0)	345 (63.0)	9 (19.6)	<.001
Cigarette smoking, n (%)	5 (5.0)	3 (5.6)	2 (4.3)	.076
Systemic hypertension, n (%)	72 (72.0)	42 (77.8)	30 (65.2)	.163
Diabetes mellitus, n (%)	10 (10.0)	6 (11.1)	4 (8.7)	.688
Dyslipidaemia, n (%)	20 (20.0)	11 (20.4)	9 (19.6)	.010
Kidney disease, n (%)	31 (31.0)	19 (35.2)	12 (26.1)	.327
Ischemic heart disease, n (%)	2 (2.0)	0 (0.0)	2 (4.3)	.122
Stroke or TIA, n (%)	16 (16.0)	5 (9.3)	11 (23.9)	.046
Symptoms and signs, n (%)
Systolic blood pressure (mm Hg)	124.54 ± 22.72	120.22 ± 18.69	126.72 ± 25.61	.411
Diastolic blood pressure (mm Hg)	78.12 ± 14.89	75.33 ± 13.70	78.52 ± 16.02	.211
Dyspnea, n (%)	98 (98.0)	52 (96.3)	46 (100.0)	.187
Nocturnal cough, n (%)	52 (52.0)	33 (61.1)	19 (41.3)	.048
Orthopnea, n (%)	63 (63.0)	37 (68.5)	26 (56.5)	.216
Paroxysmal nocturnal dyspnea, n (%)	45 (45.0)	30 (55.6)	15 (32.6)	.022
Bilateral ankle edema, n (%)	56 (56.0)	33 (61.1)	23 (50.0)	.265
Palpitation, n (%)	65 (65.0)	32 (59.3)	33 (71.7)	.192
Neck distension, n (%)	55 (55.0)	34 (63.0)	21 (45.7)	.083
NYHA classification, n (%)				.127
I	34 (34.0)	14 (25.9)	20 (43.5)
II	53 (53.0)	31 (57.4)	22 (47.8)
III	13 (13.0)	9 (16.7)	4 (8.7)
Packed cell volume (%)	38.44 ± 4.15	37.80 ± 4.85	37.89 ± 4.60	.040
Fasting blood glucose (mg/dL)	92.83 ± 20.69	91.54 ± 14.38	89.96 ± 14.09	.169
Serum sodium (mmol/L)	138.34 ± 5.46	137.69 ± 5.36	137.30 ± 7.23	.031
Serum potassium (mmol/L)	5.12 ± 6.32	3.67 ± 0.43	6.59 ± 8.82	.818
Serum chloride (mmol/L)	101.73 ± 8.79	102.33 ± 4.76	98.57 ± 15.81	.069
Serum bicarbonate (mmol/L)	22.56 ± 6.27	23.13 ± 10.65	23.00 ± 5.06	.246
Serum urea (mg/dL)	38.12 ± 18.54	40.91 ± 18.31	33.70 ± 13.97	.690
Serum creatinine (mg/dL)	1.17 ± 0.41	1.25 ± 0.45	1.01 ± 0.32	.351
eGFR (mL/min per 1.73 m2)	84.09 ± 38.99	92.41 ± 56.15	86.87 ± 37.65	.036
TSH (μIU/mL)	2.25 ± 0.89	2.23 ± 0.83	2.29 ± 0.98	.468
FT3 (pmol)	2.22 ± 0.91	2.22 ± 0.53	2.24 ± 1.23	.693
FT4 (pmol)	1.33 ± 0.41	1.29 ± 0.34	1.41 ± 0.46	.004
ECG LVH, n (%)	62 (62.0)	30 (55.6)	32 (69.6)	.150
LBBB, n (%)	4 (4.0)	4 (7.4)	0 (0.0)	.060
Indexed LA volume (mL/m2)	69.80 ± 51.89	64.54 ± 35.86	75.74 ± 65.13	.213
LVIDD (cm)	6.09 ± 0.97	6.14 ± 0.89	6.04 ± 1.05	.053
LV ejection fraction (%)	44.45 ± 14.85	45.83 ± 15.38	42.90 ± 14.14	.689
Medications
Loop diuretics	84 (84.0)	46 (85.2)	38 (84.0)	.726
Thiazide	11 (11.0)	7 (15.2)	4 (7.4)	.213
Spironolactone	73 (73.0)	41 (75.9)	32 (69.5)	.475
ACE inhibitors	40 (40.0)	24 (44.4)	16 (34.8)	.326
Angiotensin receptor blockers	53 (53.0)	28 (51.9)	25 (54.3)	.803
Angiotensin receptor-neprilysin inhibitor	3 (3.0)	2 (3.7)	1 (2.2)	.655
Beta-blockers	91 (91.0)	48 (86.9)	43 (93.5)	.424
Digoxin	54 (54.0)	31 (57.4)	23 (50.0)	.459
Calcium channel blockers	12 (12.0)	8 (14.8)	4 (8.7)	.348
Anticoagulants	97 (97.0)	51 (94.4)	46 (100.0)	.105
Amiodarone	13 (13.0)	6 (11.1)	7 (15.2)	.543

BMI = body mass index; ECG = electrocardiography; eGFR = estimated glomerular filtration rate; FT3 = free triiodothyronine; FT4 = free thyroxine; LA = left atrium; LBBB = left bundle branch block; LV = left ventricle; LVH = left ventricular hypertrophy; LVIDD = left ventricular internal dimension in diastole; PCV = packed cell volume; TSH = thyroxine stimulating hormone.

Figure 1.

Bar chart showing the age group distribution of the participants by sex.

Figure 2.

Bar chart showing the educational background of the participants by sex.

Figure 3.

Bar chart showing the employment status of the participants by sex.

Table 1 shows the symptoms and signs documented in the patients. Paroxysmal nocturnal dyspnea, basal crackles, and nocturnal cough were statistically more common in men.

Stroke or transient ischemic attack was reported more in women than men (P = .046). In terms of etiologic risk factors, hypertensive heart disease was more likely to be diagnosed in men, whereas thyroid heart disease and rheumatic heart disease were more common in women. Table 1 further shows the biophysical profile and the laboratory parameters in the participants. Men had higher packed cell volume, serum sodium, and estimated glomerular filtration rate (P < .05). Free T4 was higher in women. The medications that the participants were placed on are also shown in Table 1. Figure 4 shows the etiologic risk factors of AF in the participants by sex. Hypertensive HF is more likely to occur in men, whereas rheumatic heart disease and thyroid heart disease are more common in women. Figure 5 shows the Congestive heart failure, Hypertension, Age ≥75 years, Diabetes mellitus, Stroke, transient ischemic attack (TIA), or thromboembolism history, Vascular disease (e.g., prior myocardial infarction, peripheral artery disease, aortic plaque), Age 65–74 years, Sex category (female sex) (CHA₂DS₂-VASc) score of the participants by sex. Most had a score between 3 and 4.

Figure 4.

Bar chart showing the etiologic risk factors of AF in the participants by sex. AF = atrial fibrillation; DCM = dilated cardiomyopathy; HHD = hypertensive heart disease; RHD = rheumatic heart disease.

Figure 5.

Bar chart showing the CHA₂DS₂-VASc score of the participants by sex. CHA₂DS₂-VASc = Congestive heart failure, Hypertension, Age ≥75 years, Diabetes mellitus, Stroke, transient ischemic attack (TIA), or thromboembolism history, Vascular disease (e.g., prior myocardial infarction, peripheral artery disease, aortic plaque), Age 65–74 years, Sex category (female sex).

Discussion

AF, a prevalent sustained cardiac arrhythmia with significant public health implications, has witnessed a noteworthy surge in prevalence within SSA in recent decades.²⁶ This trend can be attributed to the aging population and rising rates of chronic noncommunicable diseases. AF and HF are known to share cardiometabolic risk factors.^27,28 However, there is mounting evidence that the existence of one may exacerbate the other.²⁹ The presence of comorbid AF in individuals with HF is associated with heightened rates of hospitalization and all-cause mortality compared with those in sinus rhythm.³⁰

This study shows the clinical and sociodemographic characteristics of AF in patients with HF in Abeokuta, Nigeria. Most participants were older than 40 years (88%), and their mean age was 55.7 years. This is similar to a study involving multiple countries from SSA in which the mean age of participants was 57 years.¹⁷ The mean age was significantly lower than in high-income countries where most AF cases are usually seen after the eighth decade of life.¹⁸ These differences may be due to the differences in etiology and lower life expectancy in countries in SSA.¹⁸

The study showed that women were on average younger than the men, with more women in the cohort falling in the 18–39 age group. The plausible reason is that risk factors for AF seem to be different in the 2 sexes. Women are more likely to have rheumatic heart disease and thyroid heart disease, which manifest at a younger age. Hypertensive heart disease was more likely to be diagnosed in the men. Notably, hypertensive heart disease was prevalent in more than half of the study population, different from findings in East Africa,³¹ where a study identified high blood pressure as associated with a lower AF incidence. This may be due to a larger sample size in their study, resulting in a more diverse participant pool.

ECG findings in our study, including left ventricular hypertrophy, mirror patterns observed in European populations according to a 2015 study.³² The consistent discovery of left ventricular hypertrophy implies that cardiac remodeling in patients with AF and HF shares common features regardless of location. Most patients in this study had a CHA₂D₂-VASc score of ≥2 and required oral anticoagulants, with anticoagulants being the most commonly used drugs by the study participants. The burden of previous stroke in participants (16%) was similar to that in other studies done in SSA (17%).³³

Strengths and limitations

The strength of the study lies in the attempt to recruit all patients with AF occurring in the setting of HF in our center over a 9-month study period, which, in the medium term, provides a picture of the rate of AF in our patients with HF. AF was found to occur at a rate of 12% of the HF population. The lower rate compared with reports in high-income countries may be due to differences in the age structure, burden of cardiovascular disease risk factors, and genetics. The rate of AF is generally lower in African Americans compared with white individuals of European origin.34, 35, 36

One of the limitations of the study is that long-term or remote ECG monitoring was not used. We could have missed cases of paroxysmal AF. We also did not compare our findings with HF cases in sinus rhythm.

Conclusion

AF in HF in our setting occurs in a younger age group compared with data from high-income countries. Women were younger than men because of rheumatic heart disease and thyroid heart disease, which occur more often in women. Generally, hypertension is the most common risk factor, and most patients will require anticoagulation. Further studies are needed to determine the impact of AF on outcome of HF in our setting.