Abstract
Direct current (DC) cardioversion is used to convert persistent atrial fibrillation (AF) to sinus rhythm (SR), but there is limited knowledge about how blood pressure (BP) is affected by conversion to SR. We sought to evaluate how BP changed in AF patients who converted to SR, compared to patients still in AF. In this retrospective registry analysis, we included a total of 487 patients, treated with DC cardioversion for persistent AF. We obtained data regarding medical history, medication, BP, and electrocardiogram the day before and 7 days after cardioversion. Systolic BP increased by 9 (±16) mm Hg (P < 0.01) and diastolic BP decreased by 3 (±9) mm Hg (P < 0.01) after conversion to SR. In the group of patients with restored SR, there was a 40% increase in the proportion of patients with a hypertensive BP level (≥140/90 mm Hg) after DC cardioversion compared to before. Patients still in AF had no significant change in BP. Systolic BP increases and diastolic BP slightly decreases when persistent AF is converted to SR. The underlying mechanisms explaining these findings are not known, but may involve either hemodynamic changes that occur when SR is restored, an underestimation of systolic BP in AF, or a combination of both. Our findings suggest that an increased attention to BP levels after a successful cardioversion is warranted.
1. INTRODUCTION
Atrial fibrillation (AF) is the most common arrhythmia of clinical significance and is associated with increased mortality.1, 2 This increased mortality risk cannot solely be explained by an increased risk of thromboembolism or by the presence of concomitant cardiovascular disease.3, 4 Due to the irregular heart rhythm in AF, there is a significant beat‐to‐beat variation in ventricular filling, stroke volume, and blood pressure (BP).5 Since conventional BP measuring equipment is normally validated in patients with sinus rhythm (SR),6 the accuracy in patients with AF is less certain. In symptomatic AF patients, attempts to restore SR, including direct current (DC) cardioversion, are part of standard clinical regimen/practice.7 Studies have shown hemodynamic improvements in stroke volume and filling pressures when SR is restored.8, 9 However, there is limited knowledge about how BP is affected by heart rhythm and no large‐scale studies have specifically investigated if BP is affected in patients converting from AF to SR.
Since hypertension and elevated systolic BP, in particular, are important predictors of cardiovascular morbidity and mortality, also in AF patients,10, 11 increased knowledge about how BP is affected by restoring SR is of clinical interest. Accordingly, we conducted a retrospective study on patients with persistent AF undergoing DC cardioversion, to evaluate how BP is affected when SR is restored, compared to patients remaining in AF.
2. METHODS
The study was conducted at Södersjukhuset, a university hospital in Stockholm, Sweden. From electronic medical records, 487 unique patients who underwent DC cardioversion for persistent AF between January 1, 2013, and December 31, 2014, were identified and included in the study. A flowchart of the screening and inclusion process is presented in Figure 1.
Figure 1.
Flowchart of inclusion process. DC, direct current
The day before elective DC cardioversion (day −1) patients had an appointment with a nurse to have a 12‐lead ECG recorded, BP measured, and adherence to anti‐coagulant treatment validated. Local guidelines recommended an echocardiography to be performed before cardioversion. One week after DC cardioversion (day 7), patients had a follow‐up visit where an additional ECG recording and BP measurement were performed. All BP measurements and ECG recordings were performed by nurses at the cardiology outpatient clinic. The same staff and the same methods were used before as well as after the DC cardioversion. Local clinical routine stipulated that BP was measured after at least 5 minutes of rest, with an aneroid sphygmomanometer using the auscultatory method and with the patient in the supine position. A single BP measurement was registered in the medical record at each visit.
2.1. Data collection
Data were collected from electronic medical records. Heart rate and rhythm were obtained from the ECG recordings. Data obtained included age, sex, and BMI. Heart failure was considered present if documented in the medical records or if the left ventricular ejection fraction was <40%. ECG and BP registered from up to 2 days prior to the day of DC cardioversion were accepted as day −1 data. According to clinical routine, the 1‐week follow‐up was 7 days after cardioversion but ECG and BP registered between 5 and 12 days were accepted. Information about antihypertensive and antiarrhythmic medication was obtained from medical records.
2.2. Statistical analysis
According to their distribution, descriptive data are presented as mean and standard deviation or median and interquartile range. Comparison of categorical variables was made using the Fisher's exact test. For continuous variables, the Shapiro‐Wilk test was used to test for normality. For data following a normal distribution, a Student's t test was used to test for differences between groups. For non‐normally distributed data, the Mann‐Whitney U test and the Wilcoxon signed‐rank test were used. A P‐value <0.01 was considered significant. Statistical analyses were performed using SPSS Statistics version 22 (IBM Corp., Armonk, NY, USA).
2.3. Ethical considerations
The data used in the study were anonymized and the patients could only be identified with access to the study code corresponding number. The study protocol was approved by the regional ethics committee (DNR 2014/2199‐31/4), and the procedures followed were in accordance with institutional guidelines.
3. RESULTS
Clinical characteristics of the patients are presented in Table 1. There were missing data regarding heart rate on day 7 in four patients. Sixty patients had no weight or height registered and BMI could therefore not be calculated. In seven patients, we could not elucidate if heart failure was present and 20 patients had no echocardiographic examination performed.
Table 1.
Clinical characteristics
|
All n = 487 (%) |
AF‐AF group n = 198 (%) |
AF‐SR group n = 289 (%) |
P‐value | |
|---|---|---|---|---|
| Age, years (±SD) | 67 (±10) | 67 (±9) | 67 (±10) | 0.509 |
| Sex | ||||
| Male | 344 (71) | 131 (66) | 213 (74) | 0.085 |
| Female | 143 (29) | 67 (34) | 76 (26) | |
| BMI >25 | 306 (72) | 127 (73) | 179 (71) | 0.585 |
| Medical history | ||||
| Diabetes mellitus | 79 (16) | 31 (16) | 48 (17) | 0.803 |
| Hypertension | 313 (64) | 121 (61) | 192 (67) | 0.212 |
| Previous TIA/stroke | 39 (8) | 21 (11) | 18 (6) | 0.090 |
| MI/Peripheral ischemia | 50 (10) | 15 (8) | 35 (12) | 0.128 |
| OSAS | 30 (6) | 14 (7) | 16 (6) | 0.566 |
| Heart failure | 108 (23) | 55 (28) | 53 (19) | 0.015 |
| Medication at DC cardioversion day | ||||
| Antihypertensive drugs | ||||
| Beta‐blockers | 413 (85) | 174 (88) | 239 (83) | 0.125 |
| ACE inhibitors | 187 (38) | 87 (44) | 100 (35) | 0.046 |
| ARBs | 108 (22) | 32 (16) | 76 (26) | 0.010 |
| Thiazide diuretics | 48 (10) | 21 (11) | 27 (9) | 0.646 |
| Calcium inhibitors | 106 (22) | 40 (20) | 66 (23) | 0.505 |
| Aldosterone antagonists | 29 (6) | 10 (5) | 19 (7) | 0.562 |
| Loop diuretics | 135 (28) | 58 (29) | 77 (27) | 0.538 |
| Antiarrhythmic drugsa | 77 (16) | 27 (14) | 50 (17) | 0.313 |
| No medication changeb | 371 (76) | 138 (70) | 233 (81) | 0.007* |
| Echocardiography | ||||
| Left ventricular hypertrophy | 49 (11) | 18 (10) | 31 (12) | 0.644 |
| Left atrial enlargement | 410 (88) | 169 (91) | 241 (86) | 0.187 |
| LVEF (mean ±SD, %) | 48.2 ± 10.5 | 47.8 ± 11.1 | 48.5 ± 10.1 | 0.526 |
All patients and divided into AF or SR post‐DC cardioversion.
If not otherwise stated, table refers to number of patients (percentage).
ACE inhibitors, angiotensin‐converting enzyme; AF, atrial fibrillation; ARBs, angiotensin II receptor blockers; DC, direct current; LVEF, left ventricular ejection fraction; MI, myocardial infarction; OSAS, obstructive sleep apnea syndrome; SR, sinus rhythm; TIA, transient ischemic attack.
Antiarrhythmic drugs included were as follows: dronedarone, flecainide, amiodarone, disopyramide, and sotalol.
Between the day before DC cardioversion and day 7 after DC cardioversion.
A P‐value <0.01 was considered significant.
At 1‐week follow‐up, 41% of the patients had AF (AF‐AF group) and 59% were in SR (AF‐SR group). Baseline clinical characteristics were similar between these groups except for heart failure which was slightly more common in the AF‐AF group. Change of medication after cardioversion was more common in the AF‐AF group. Heart rate did not differ significantly between the AF‐AF and AF‐SR groups before cardioversion. However, at 1‐week follow‐up a significant decrease in heart rate was observed for patients in SR (Table 2).
Table 2.
Heart rate before (day −1) and after (day 7) DC cardioversion, divided according to AF or SR on day 7
|
AF‐AF group n = 195 |
AF‐SR group n = 288 |
Difference between groups | |||
|---|---|---|---|---|---|
| BPM (±SD) | P‐valuea | BPM (±SD) | P‐valuea | P‐valueb | |
| Heart rate day −1 | 85 (±17) | 82 (±16) | 0.176 | ||
| Heart rate day 7 | 88 (±18) | 58 (±11) | <0.001 | ||
| Mean change | 3 (±14) | 0.004 | −24 (±17) | <0.001 | <0.001 |
AF, atrial fibrillation; BPM, beats‐per‐minute; DC, direct current; SR, sinus rhythm.
P‐value for change within group, calculated with Wilcoxon signed‐rank test.
P‐value for difference between the groups, calculated with Mann‐Whitney U test.
3.1. Blood pressure difference
In the AF‐SR group, there was a statistically significant increase in systolic BP of 9 ± 16 mm Hg, from 129 ± 17 to 137 ± 18 mm Hg, and a slight but statistically significant decrease in diastolic BP of 3 ± 9 mm Hg after cardioversion. In contrast, there was no significant change in systolic or diastolic BP in the AF‐AF group (Table 3A).
Table 3.
Mean systolic and diastolic BP before (day −1) and after (day 7) DC cardioversion, divided according to AF or SR on day 7
| (A) All 487 patients | |||||
|---|---|---|---|---|---|
|
AF‐AF group n = 198 |
AF‐SR group n = 289 |
Difference between groups | |||
| mm Hg (±SD) | P‐valuea | mm Hg (±SD) | P‐valuea | P‐valueb | |
| Mean systolic BP | |||||
| Day −1 | 133 (±17) | 129 (±17) | <0.001 | ||
| Day 7 | 133 (±17) | 137 (±18) | 0.008 | ||
| Mean change | 0 (±14) | 0.439 | 9 (±16) | <0.001 | <0.001 |
| Mean diastolic BP | |||||
| Day −1 | 84 (±10) | 82 (±9) | 0.018 | ||
| Day 7 | 84 (±11) | 79 (±10) | <0.001 | ||
| Mean change | 0 (±10) | 0.319 | −3 (±9) | <0.001 | <0.001 |
| (B) 371 patients without changes in medication | |||||
|---|---|---|---|---|---|
|
AF‐AF group n = 138 |
AF‐SR group n = 233 |
Difference between groups | |||
| mm Hg (±SD) | P‐valuea | mm Hg (±SD) | P‐valuea | P‐valueb | |
| Mean systolic BP | |||||
| Day −1 | 136 (±21) | 131 (±19) | 0.134 | ||
| Day 7 | 133 (±18) | 139 (±18) | 0.117 | ||
| Mean change | −3 (±15) | 0.132 | 9 (±18) | <0.001 | <0.001 |
| Mean diastolic BP | |||||
| Day −1 | 85 (±11) | 83 (±8) | 0.240 | ||
| Day 7 | 86 (±13) | 81 (±9) | 0.008 | ||
| Mean change | 1 (±11) | 0.312 | −2 (±11) | 0.103 | 0.071 |
AF, atrial fibrillation; BP, blood pressure; DC, direct current; SR, sinus rhythm.
P‐value for difference within group, calculated with Wilcoxon signed‐rank test.
P‐value for difference between groups, calculated with Mann‐Whitney U test.
In 76% (n = 371) of all patients, no changes in antihypertensive or antiarrhythmic medication were made between day −1 and day 7. In order to test if the observed change in BP was independent of change in antihypertensive or antiarrhythmic drug use, a subgroup analysis that only included patients without drug changes was conducted. The result regarding increase in systolic BP was similar to the overall result; however, the decrease in diastolic BP in the AF‐SR group did not remain significant in patients without changes in their medication (Table 3B).
The number of patients with a systolic BP ≥140 mm Hg or diastolic BP ≥90 mm Hg before and after cardioversion is presented in Table 4. In the AF‐SR group, there was a significant 40% increase in the number of patients with a hypertensive BP level after cardioversion. In contrast, for the AF‐AF group no significant change in the number of hypertensive patients was observed after cardioversion. In a subgroup analysis comparing patients with and without a preexisting diagnosis of hypertension in the AF‐SR group, there was no difference in the proportion of patients that developed a hypertensive BP level after DC cardioversion.
Table 4.
Number (percentage) of hypertensive patients before (day −1) and after (day 7) DC cardioversion, divided according to AF or SR on day 7
|
AF‐AF group n = 198 |
AF‐SR group n = 289 |
|
|---|---|---|
| n (%) | n (%) | |
| BP ≥140/90a day −1 | 101 (51) | 115 (40) |
| BP ≥140/90a day 7 | 107 (54) | 161 (56) |
AF, atrial fibrillation; BP, blood pressure; DC, direct current; SR, sinus rhythm.
Systolic BP ≥140 and/or diastolic BP ≥90 mm Hg.
4. DISCUSSION
In this retrospective study, systolic BP significantly increased and diastolic BP slightly decreased in patients remaining in SR 1 week after cardioversion. Furthermore, in this group the proportion of patients with a hypertensive BP level markedly increased after cardioversion. The increase in systolic BP after restoration of SR was consistent also in the subgroup of patients that did not undergo any changes in medication. In contrast, there were no significant changes in either systolic or diastolic BP in patients remaining in AF. To our knowledge, this is the largest study to date investigating BP in patients with persistent AF undergoing DC cardioversion. Previously published data on BP changes after cardioversion are to some extent divergent. Sanders et al12 reported a significant decrease in diastolic BP (from 74 to 70 mm Hg) but an unchanged systolic BP in 18 AF patients evaluated with 24‐hour ambulatory BP measurement after cardioversion. A similar study by Olsen et al13 included 12 AF patients converted to SR and evaluated with 24‐hour ambulatory BP measurements before and after cardioversion. The authors report a significant decrease in diastolic BP (from 81.7 to 75.2 mm Hg) and an unchanged systolic BP.
A larger and more recent study by Maselli et al,14 which included 100 patients undergoing DC cardioversion (of whom 63 patients had restored SR at follow‐up), investigated the reliability of oscillometric BP monitoring in AF. A decrease in diastolic BP of 5 mm Hg and, in line with our results, an increase in systolic BP of 4‐5 mm Hg following cardioversion were observed. Another study by Maselli et al15 included 54 hypertensive patients with persistent AF undergoing DC cardioversion. BP was evaluated with ambulatory BP on the day before and about a month after cardioversion. In the 34 patients with restored SR at follow‐up, mean 24‐hour systolic BP was significantly increased and mean 24‐hour diastolic BP significantly decreased (by 5.1 and 2.4 mm Hg, respectively), thus largely resembling the findings in our study. The most striking finding in our current study is that we observed a clear increase in systolic BP when SR was restored. The entry characteristics in the studies mentioned above were quite similar to our current study and it is unclear why our findings to some extent diverge from some of the previously reported data. It should be noted though that in the previous studies, fewer patients were included and BP was mainly evaluated with oscillometric BP measurement, as opposed to in our study where conventional sphygmomanometry was used. Furthermore, in terms of average pulse pressure (PP), our results are very similar to those in the first study by Maselli et al,14 with an increase of PP in the AF‐SR group of 11 mm Hg in our study as compared to 10.1 and 9.2 mm Hg for oscillometric and sphygmomanometric BP measurement, respectively.
It is beyond the scope of this study to elucidate the underlying mechanisms explaining why systolic BP increases and diastolic BP tends to decrease when restoring SR by DC cardioversion. However, we suggest two possible explanations, or a combination of the two, for these findings.
First, hemodynamic changes occurring when AF is converted to SR may affect BP. These changes in hemodynamics are complex and depend on many different variables. As mentioned, previous studies have found a decrease in diastolic BP when restoring SR. Irregular heart rhythm, endothelial dysfunction, increased sympathetic nervous tone as well as an increased renin‐angiotensin‐aldosterone system activity in AF have been discussed as possible mechanisms explaining a higher diastolic BP in AF compared to when SR is restored.12, 16, 17 Hence, these mechanisms support our observation of a lower diastolic BP in SR but it does not explain why systolic BP increases after conversion to SR.
Blood pressure is also affected by stroke volume, which has been reported to increase in AF patients regaining SR and thereby atrial contraction,9, 18 and could constitute a mechanism for an increased systolic BP after restoration of SR. Furthermore, heart rate decreased in patients with restored SR after cardioversion. During normal physiological conditions, when heart rate increases, BP increases as well.19 In one study, the impact of heart rate on BP parameters was investigated. When heart rate was increased by incremental right atrial pacing, neither systolic nor diastolic brachial BP significantly changed.20 Hence, it is unlikely that our finding of increased systolic BP in patients with restored SR is related to the decrease in heart rate.
Another possible mechanism that could explain an increased systolic BP when SR is restored is if systolic BP is systematically underestimated when measured with conventional sphygmomanometry in patients with AF. BP measuring techniques are mainly validated in individuals with SR, and the accuracy is less certain in patients with AF.6 Previous studies have reported that systolic BP tends to be underestimated using non‐invasive compared to invasive measuring techniques,5 both in SR and AF. In a study by Pagonas et al,5 the accuracy of oscillometric BP monitoring compared to invasive BP measurement, in patients with AF, was evaluated. They concluded that AF did not significantly affect the accuracy of oscillometric measurements if three repeated measurements were performed. However, systolic oscillometric BP, in comparison with invasive systolic BP, was numerically more underestimated in patients with AF than in patients with SR (7.4 and 3.9 mm Hg, respectively), although this difference was not statistically significant.
Regardless of the cause of our findings, a better attention to BP in this group of patients is most probably warranted. According to the results of our study, there was a 40% increase in patients with a hypertensive BP level (≥140/90 mm Hg) in the AF‐SR group that could be identified when SR was restored (Table 4). These findings need to be confirmed in prospective studies.
4.1. Strengths and limitations
This is a retrospective study with its inherent limitations. Because of the fairly large number of patients, imprecise BP measurements or missing data in a few patients were unlikely to have a great impact on the main results. However, 57 subjects could not be included in the study due to missing data regarding heart rhythm and BP on day 7. Patients with an immediate AF‐relapse after cardioversion were in some cases directly scheduled for a new cardioversion attempt with a changed antiarrhythmic treatment. Hence, it is probable that more patients in the AF‐AF than the AF‐SR group did not attend their 1‐week follow‐up visits, which accordingly may have led to an overestimation of the proportion of patients maintaining SR. Local guidelines recommended conventional manual sphygmomanometer BP measurement with the patient in a supine position and after resting for at least 5 minutes. We have no exact information regarding the adherence to these routines. However, the methods, the setting, and staff were the same prior to and post cardioversion as well as in both groups of patients which should make the measurements comparable. Even though current international clinical guidelines recommend BP measurement to be performed in the sitting position, BP was measured in the supine position in this study, which is the most common way to measure BP in hospitals in Sweden.
5. CONCLUSIONS
In our cohort of patients with persistent AF, restoration of SR with DC cardioversion led to an increase in systolic BP and, to a lesser degree, a decrease in diastolic BP when measured with conventional sphygmomanometry in a routine clinical setting. Patients relapsing into AF had an unchanged BP. These findings may be explained by hemodynamic changes occurring when SR is restored, by an underestimation of systolic BP when measured with conventional sphygmomanometry in AF or by a combination of both. Our findings suggest a need for an increased awareness of BP levels after successful DC cardioversion.
DISCLOSURES
The authors report no conflicts of interest.
Olbers J, Jacobson E, Viberg F, et al. Systolic blood pressure increases in patients with atrial fibrillation regaining sinus rhythm after electrical cardioversion. J Clin Hypertens. 2019;21:363–368. 10.1111/jch.13496
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