The ECG findings during sudden collapse (syncope or sudden death) in severe aortic stenosis (AS) are not well defined. We conducted a comprehensive review of the literature for ECG data during sudden collapse in patients with AS and provided a case report of our own. There were 37 published cases of syncope or sudden death in patients with severe AS which were documented by ECG. Brady- or ventricular arrhythmias were documented in 34 cases (92%). Bradyarrhythmia (n = 24; 71%) was more common at the time of collapse than ventricular tachyarrhythmia (n = 10; 29%). There was slowing of the sinus rate before bradyarrhythmia in the vast majority of patients with bradyarrhythmia but not in those presenting with ventricular tachyarrhythmia (75% vs 0%; p <0.001). ECG evidence of ischemia (ST-segment depression or elevation) was present in most patients with bradyarrhythmia but not in those with ventricular tachyarrhythmia (75% vs 0%; p = 0.011). In conclusion, our findings suggest that left ventricular baroreceptor activation plays a dominant role in the pathophysiology of sudden collapse in patients with severe AS and suggest that ischemia may play a role as well.
Sudden collapse is an ominous finding in a patient with severe aortic stenosis (AS). The most feared outcome is sudden cardiac death. Despite the many advances in the evaluation and treatment of AS over the last century, sudden death remains a significant cause of mortality in these patients. Here we present the case of a patient who experienced sudden cardiac arrest during a treadmill exercise test and was found to have severe AS. We reviewed the literature for ECG data to gain potential insight into the mechanisms of sudden collapse in patients with AS. While cases of sudden collapse during ECG recording are rare, several have been observed in patients with AS over the years. ECG findings at the time of collapse include normal sinus rhythm, sinus bradycardia, varying degrees of A-V block, asystole, idioventricular rhythm, and ventricular arrhythmias.
Case Presentation
A 65-year-old man with known hypertension, hyperlipidemia, and exertional chest “tightness” for 3 months presented with witnessed syncope while carrying groceries up one flight of stairs. Cyanosis was noted by a witness during this event. Afterward the patient experienced nausea and lightheadedness for 5 to 10 minutes. His symptoms completely resolved after receiving intravenous fluids in the emergency department. Electrocardiogram (ECG) in the emergency department demonstrated normal sinus rhythm with minimal 0.5 mm ST depression in the inferior leads (II, III, aVF).
Prior to work-up for a valvular etiology, he was referred for stress testing with myocardial perfusion imaging for evaluation of angina pectoris and underwent exercise testing using a standard Bruce protocol. He had appropriate heart rate response in Stage 1 and developed diffuse ST depression along with ST elevation in lead AVR. In stage 2, he developed a gradual decline in heart rate, resulting in sinus bradycardia. At that time, the patient complained of lightheadedness and the test was aborted. He lost consciousness shortly after he was lowered to a stretcher. ECG revealed asystole ( Figure 1 . Panels A and B ). Chest compressions were immediately started and the patient received 2 doses of epinephrine (1 mg each) and 2 cycles of cardiopulmonary resuscitation (CPR, 2 minutes each). The patent regained full consciousness and was neurologically intact. Echocardiogram revealed a bicuspid aortic valve with severe stenosis (peak velocity 5 m/sec, peak gradient 101 mm Hg, mean gradient 66 mm Hg, and calculated aortic valve area of 0.56 cm 2 ). Coronary angiography revealed no coronary artery disease (CAD). He underwent uncomplicated surgical aortic valve replacement and was asymptomatic 20 months later.
Methods
We reviewed the literature using the PubMed database with the search terms “aortic stenosis + syncope” and “aortic stenosis + sudden death.” For the purposes of our review, we considered syncope and sudden cardiac death on a spectrum of “sudden collapse” related to severe aortic stenosis, with similar underlying mechanisms. Abstracts were reviewed for relevance. References from included publications were also reviewed for relevance and considered for inclusion. Cases were included in our analysis if there was documentation of the event (syncope or sudden death) by ECG.
Two review authors independently examined the titles and abstracts of all the potential studies to be included, identified by the search strategy. Inconsistencies were resolved by a third author. Then, the complete text of the relevant primary studies was evaluated and data were extracted. The information about the authors, name of the article, journal, year, issue, and volume was included. The following data were retrieved from each case: age, sex, presenting symptoms, history of coronary artery disease, and ECG data including: rhythm at the time of collapse and presence or absence of preceding ST segment changes and/or slowing of the sinus rate prior to collapse.
The baseline characteristics for each case were extracted from the original manuscripts. The data from all cases reports were pooled. In this pooled cohort baseline characteristics were reported as frequency with percentage (%) for categorical variables and median with interquartile ranges for continuous variables. We used chi-square and Wilcoxon rank sum tests to evaluate for differences in categorical and continuous baseline characteristics, respectively. Analysis was performed in Stata software version 14.2 (StataCorp, College Station, Texas).
Results
Our search revealed 2,639 results for possible inclusion. We identified 37 cases which had either a published ECG at the time of collapse (30/37) or a clear description of the ECG at the time of collapse (7/37). The median age of the cohort was 64 years and 57 percent were men. In cases in which they were documented, classically taught cardinal symptoms of aortic stenosis were common with 86% (31/36), 36% (8/22), and 19% (4/21) percent of patients having documented symptoms of syncope, angina, or heart failure, respectively. 34 of 37 cases (92%) had clear documentation of either bradyarrhythmia or ventricular arrhythmia at the time of collapse and were further analyzed. Of 3 cases which were excluded, normal sinus rhythm was present in 2 and both “ventricular standstill” and “ventricular arrhythmia” were documented in 1. Individual case details including the presence of published EKG can be found in Supplemental Table 1 .
In this series, bradyarrhythmia (24/34; 71%) was more common at the time of collapse than ventricular tachyarrhythmia (10/34; 29%). Patients presenting with bradyarrhythmia were more likely to have a history of syncope than those presenting with ventricular tachyarrhythmia (96% vs 67%; p = 0.02). Preceding slowing of the sinus rate was also present in the vast majority of patients presenting with bradyarrhythmia and absent in those presenting with ventricular tachyarrhythmia (75% vs 0%; p <0.001). Signs of ischemia defined as preceding ST-segment deviation (i.e., ST-segment depression or elevation) were present in the vast majority of patients presenting with bradyarrhythmia and absent in those presenting with ventricular tachyarrhythmia (75% vs 0%; p = 0.01). Our results are summarized in Table 1 .
| Variable | Level | Bradyarrhythmia | Ventricular arrhythmia | p value |
|---|---|---|---|---|
| N = 24 | N = 10 | |||
| Age, median (IQR) | 65 (60, 68) | 62 (51, 67) | 0.49 | |
| Women/men | 13 (54%) | 5 (56%) | 0.94 | |
| 11 (46%) | 4 (44%) | |||
| Prior syncope | Absent | 1 (4%) | 3 (33%) | 0.022 |
| Present | 23 (96%) | 6 (67%) | ||
| Angina pectoris | Absent | 10 (59%) | 4 (80%) | 0.39 |
| Present | 7 (41%) | 1 (20%) | ||
| Prior congestive heart failure | Not available | 9 (38%) | 3 (33%) | 0.067 |
| Absent | 14 (58%) | 3 (33%) | ||
| Present | 1 (4%) | 3 (33%) | ||
| Presentation | Sudden death | 5 (21%) | 4 (40%) | 0.25 |
| Syncope | 19 (79%) | 6 (60%) | ||
| Prior myocardial infarction/presence of obstructive coronary artery disease | Not available | 11 (46%) | 5 (50%) | 0.52 |
| Absent | 9 (38%) | 2 (20%) | ||
| Present | 4 (17%) | 3 (30%) | ||
| Angina pectoris (before or after event) | Not available | 8 (33%) | 5 (50%) | 0.62 |
| Absent | 8 (33%) | 3 (30%) | ||
| Present | 8 (33%) | 2 (20%) | ||
| Slowing of sinus rate preceding collapse | Not available | 4 (17%) | 8 (80%) | <0.001 |
| Absent | 2 (8%) | 2 (20%) | ||
| Present | 18 (75%) | 0 (0%) | ||
| ST segment deviation * | Absent | 5 (25%) | 3 (100%) | 0.011 |
| Present | 15 (75%) | 0 (0%) |
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