Potential Predictors of Sudden Cardiac Death in Aortic Valve Disease

Al-Riyami, Abdullah Amer Sultan (1991) Potential Predictors of Sudden Cardiac Death in Aortic Valve Disease. PhD thesis, University of Glasgow.

Abstract

Although sudden death continues to claim 15 to 20% of patients with aortic valve disease, the exact cause still remains speculative. It has been the assumption of many workers that these deaths result from ventricular tachyarrhythmias. The major aim of this thesis was therefore to assess the prevalence of ventricular arrhythmias in patients with aortic valve disease and to evaluate their significance by signal-averaged electrocardiography (SAECG). A total of 100 patients, 55 with predominant aortic stenosis (AS) with a mean transaortic gradient of 81+/-27 mmHg, 16 with predominant aortic regurgitation (AR) and 29 with combined AS and AR were studied prior to aortic valve replacement (AVR). Substantial left ventricular hypertrophy was present with a mean echocardiographic left ventricular mass index of 210+/-72 g/m2. Left ventricular systolic and diastolic function were normal in 94% and 61% of patients respectively. Coronary angiography was performed in 89 patients of whom 50 (56%) had chest pain typical of angina pectoris and 21 (24%) had significant coronary artery disease. Angina was present in 20 of these 21 patients (95%). Thus angina could predict the presence of significant coronary artery disease with 95% sensitivity and 54% specificity. In agreement with previous work, this study has shown a high prevalence of complex ventricular arrhythmias. Nonsustained ventricular tachycardia (NSVT) was detected by ambulatory electrocardiographic monitoring in 9 (9%) patients of whom only one had late potentials on SAECG. The frequency of ventricular arrhythmias was not related to the degree of left ventricular hypertrophy or the severity of aortic valve disease. Left ventricular function did not have any effect on ventricular arrhythmias. A high prevalence of complex ventricular arrhythmias was also seen in the early (5 to 7 days post AVR) and late (121+/-24 days post AVR) post-operative periods. The frequency of ventricular arrhythmias was not affected by AVR. In the late post-operative period, 4 patients had NSVT, but none of them had late potentials on SAECG. As with the pre-operative results, there was little to suggest the presence of an arrhythmogenic substrate in these patients in view of the absence of late potentials on SAECG. Furthermore, no sustained ventricular arrhythmias were detected in the 3 study periods. Aortic valve replacement was accompanied by a significant regression in echocardiographic left ventricular hypertrophy in patients with predominant AS and those with combined AS and AR. Of the total 100 patients in this study, 75 were on the cardiac surgical waiting list of whom 60 have already undergone operation. There have been 7 deaths (7%) during the study period, 3 of them occurring suddenly in patients awaiting surgery. Thus, the incidence of sudden death while awaiting operation was 4%. It has been suggested that patients with decreased heart-rate variability have decreased vagal tone, increased sympathetic activity or both and hence are at a higher risk of developing ventricular fibrillation and sudden death. Cardiovascular autonomic function was assessed in 47 patients prior to AVR and repeated in 10 patients 3 months following AVR. Abnormal heart-rate variation during deep breathing was detected in 18 (38%) patients. AVR was not accompanied by any improvement in cardiovascular autonomic function at least in the shortterm . Thus, despite a high prevalence of ventricular arrhythmias in aortic valve disease patients with substantial left ventricular hypertrophy, there was little to suggest the presence of an arrhythmogenic substrate. The potential mechanism of sudden death in these patients could be speculated on the basis of impaired cardiovascular autonomic function.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Medicine
• Date of Award: 1991
• Depositing User: Enlighten Team
• Unique ID: glathesis:1991-78253
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 30 Jan 2020 15:35
• Last Modified: 30 Jan 2020 15:35
• URI: https://theses.gla.ac.uk/id/eprint/78253