Asymptomatic Aortic Stenosis - Prognosis, Risk Stratification and Follow-Up

Due to an aging population and improved non-invasive cardiac imaging (mainly the wide use of transthoracic echocardiography), the number of patients with asymptomatic aortic stenosis (AS) is continuously increasing. Aortic stenosis is a progressive active disease which can be treated effectively by aortic valve implantation. Therefore, optimal timing of surgery is crucial demanding precise risk stratification to identify high-risk but still asymptomatic patients. Such patients should undergo close clinical follow-up examination or even elective aortic valve replacement. Whereas severe symptomatic aortic stenosis is a class I indication for valve replacement, the decision to operate on asymptomatic patients remains controversial. Accepted indications for aortic valve replacement for asymptomatic patients with severe aortic stenosis are (a) the need of cardiac surgery for any other reason such as coronary bypass grafting or surgery of the aorta ascendens and (b) if left ventricular systolic dysfunction defined by an ejection fraction below 50% occurs. The risk of sudden death in asymptomatic severe aortic stenosis without preceding symptoms is a matter of concern, although it is regarded as low (around 1% per year) and below the perioperative mortality of aortic valve replacement. Otherwise, there is a risk of irreversible myocardial damage due to left ventricular hypertrophy and myocardial fibrosis if surgery is performed too late. The strategy to wait for occurrence of symptoms before indicating aortic valve implantation is further challenged by an increased mortality in patients awaiting surgery after onset of symptoms, by late symptom reporting by many patients and a higher operative risk for more symptomatic patients. On the other hand, the immediate operative risk, the long-term morbidity and mortality related to the prosthetic aortic valve, and the potential need for re-operation have to be taken into account. Several risk factors for worse clinical outcome in patients with asymptomatic aortic stenosis have been established in the last years. Hemodynamic parameters such as a peak aortic jet velocity > 5m/s or a mean gradient > 60 mmHg are used to define very severe aortic stenosis, and an increase in peak aortic jet velocity > 0.3 m/s/year define a fast hemodynamic progression rate. Whether such highrisk patients should undergo elective aortic valve implantation even in the asymptomatic state is still a matter of debate and handled differently between European and American Guidelines. Furthermore, interest has