Is sudden death a threat in aortic stenosis?

Sudden death : definition

Sudden cardiac death is defined as “Natural death due to cardiac causes, heralded by abrupt loss of consciousness within one hour of the onset of symptoms; preexisting heart disease may have been known to be present, but the time and mode of death are unexpected.”(1).

Sudden death in aortic stenosis : assumed mechanism

In patients with aortic stenosis (AS), sudden death remains a particular concern. The following hypothesis have been proposed to explain the mechanism of sudden death in aortic stenosis:

1. An abnormal Betzold-Jarisch reflex (stimulation of left ventricular baroreceptors may lead to arterial hypotension, a fall in venous return and consequent bradycardia)
2. Ventricular tachyarrhythmias (inappropriate hypotension and a low cardiac output provoke coronary hypoperfusion, in patients who already have a predisposition through left ventricular hypertrophy)
3. Atrioventricular conduction disturbances (there is a contiguity between valvular-perivalvular calcification and the His-Purkinje system [there is also a high prevalence of conduction abnormalities in patients with AS])

Sudden death in aortic stenosis :  is a prediction possible?

A prediction of the risk of sudden death in these patients would be desirable.

QT-dispersion, which has been shown to be predictive of cardiac death in other pathologies (long QT syndrome, heart failure, hypertrophic cardiomyopathy, after myocardial infarction) has been shown to correlate with left ventricular mass in AS and a reduction in QT dispersion was also observed after aortic valve replacement (2).

Also, late potentials (which have a high prevalence in patients with coronary artery disease or inducible ventricular tachyarrhythmias) are found in up to 25% of the patients with moderate-to-severe AS (3).
However the predictive value for sudden death in AS of QT dispersion, of late potentials and even of a programmed ventricular stimulation remains unclear.
While there are no means of accurately predicting sudden death in patients with aortic stenosis, the major question is to know how frequent sudden death occurs in AS.

Sudden death in aortic stenosis : epidemiology

Only 2 studies have reported the occurrence of sudden death in truly asymptomatic patients.
In a recently published study, which is the largest to date, 11 sudden deaths were observed among 622 patients have been followed for a mean of 5.4 years (4). 
In another study 1 sudden death was observed among 104 patients followed for a mean of 27 months (5).

Thus, sudden death is rare in asymptomatic patients with AS and occurs at a rate of less than 1% per year.

However in a study assessing the causes of death in 387 young athletes, aortic valve stenosis was identified as the reason of death in 10 athletes (6).

The incidence of sudden death in symptomatic patients with AS is very high, with a reported range of up to 34% (7).

Sudden death in aortic stenosis : risks

While symptomatic patients are currently being referred to surgery, the problem of sudden death among symptomatic patients is still encountered when the waiting time for aortic valve surgery is long (8).
Finally, a low risk of sudden cardiac death remains after aortic valve replacement surgery with an incidence of about 0.3% (9).

A significantly higher risk of sudden death after valve replacement is encountered, when patients with concomitant coronary artery disease are not revascularised at the time of surgery (10).

To conclude, asymptomatic patients with AS are at a low risk of sudden death. To avoid unnecessary risk however, strenuous exercise is contraindicated.
Symptomatic patients on the other hand are at a high risk for sudden death and should be promptly identified and referred to surgery. Attempts should be made to reduce waiting time for surgery. 
In the presence of coronary artery disease, revascularisation should be performed at the time of surgery.
Finally, as the incidence of sudden death after valve replacement and in asymptomatic patients is similar, the prevention of sudden death is not an argument for early elective surgery in asymptomatic patients.

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.