Natural History of the Disease – Aortic Stenosis
The severity of aortic valve obstruction gradually increases over 10 to 15 years, so that there is a long latency period with a valve area compatible with mild to moderate severity. Only 2.5% of patients with valve sclerosis progress to severe aortic valve stenosis in 8-10 years.
While the patients are asymptomatic, the prognosis is very similar to that of the general population, but several severity criteria must be closely monitored from the moment the patient has an average gradient above 40mmHg and valve area below 1cm2, that is, when is classified as having a major injury.
The strongest predictor of symptom progression is the aortic flow velocity at echocardiogram doppler. As we well know, the echocardiogram measures flow velocity and the flow velocity measurement is the one that suffers the least interference from other calculation errors throughout the evaluation. When we find a flow rate below 3m/s (maximum gradient of 36mmHg), almost 90% remains asymptomatic over 2 years, while only 20% remains asymptomatic in the same period when the speed exceeds 4m/s (maximum gradient of 64mmHg).
Similarly, asymptomatic patients may have predicted outcomes according to the intensity of aortic valve calcification. Patients with low calcification are event-free by up to 80% for 5 years.
At this point, we must be attentive to those cases that end up being limited. Patients, often elderly, who change their lifestyle and for this reason are unable to point to the emergence of physical activity limitations caused by the disease. It is up to the doctor to properly explore the anamnesis and, if applicable, request a stress test in a hospital environment to verify the absence or not of symptoms.
The rate of hemodynamic progression of aortic stenosis can also signal an unfavorable outcome. The average of aortic valve reduction is 0.12 cm2/year with an increase in peak velocity of 0.32 cm/s/year and an average gradient of 7 mmHg/year. Individuals who show an increase in these values should be closely watched, even if asymptomatic. Along with this assessment, it is recommended to carry out stress testing in a hospital environment and serial BNP measurements.
Once symptoms appear, even if they are mild, survival begins to be compromised unless there is intervention (read here). The prospects are even worse when we find systolic dysfunction of the left ventricle and we are faced with low-flow low-gradient aortic stenosis. Therefore, these cases should be promptly referred for surgical correction, whether conventional or percutaneous, depending on an appropriate indication.
1 – Otto CM, Bonow RO. A Valvular Heart Disease – A companion to Braunwald’s Heart Disease. Fourth Edition, 2014.