Severe Aortic Stenosis: Timing of Intervention
Presenter: Catherine M. Otto, MD
Catherine M. Otto, MD, University of Washington, Seattle, said it is well recognized that aortic valve disease is a spectrum of disease that spans from the patient at risk to the patient with valve obstruction, but that the focus of this talk would be the new implications for timing of intervention for those with severe aortic stenosis (AS).
She said this is established in the updated ACC/AHA Valvular Heart Disease Guidelines as patients with severe calcification or fibrosis of the valve leaflets and reduced leaflet motion, with hemodynamics showing an aortic velocity of 4 meters per second or higher, or a mean gradient of over 40 mmHg. Valve area typically is less than 1 cm2 but that is not a required criterion. That definition was based on natural history studies.
The key factor driving the timing of valve replacement, even in patients with severe AS, is symptoms due to AS—classically, angina, heart failure and syncope. But increasingly as we follow patients prospectively and recognize early symptoms, patients with dyspnea on exertion or a decrease in exercise capacity would be defined as symptomatic patients with AS. If echocardiogram in those patients shows a calcified valve that does not move normally with a high velocity, they have severe stenosis, and aortic valve replacement is recommended.
Some patients with severe AS say they don’t have symptoms, and they may not recognize that they do. Elderly patients may attribute them to age, symptoms may be attributed to comorbid conditions, or the symptoms may have come on insidiously so the patient just adapted their lifestyle to match their exercise capacity. When that’s a concern, exercise testing can be helpful, looking for provoked symptoms, and considering them as equivalent to spontaneous symptoms in terms of intervention. Lack of an increase in BP with exercise should also be looked for, or decreased exercise capacity, as these can be markers of early symptom onset.
Another factor that can be used in an asymptomatic patient to ensure they are not symptomatic is to measure BNP levels. One study has shown asymptomatic patients with severe AS have higher BNP levels, showing it is a marker of symptom onset.
Because it affects the vasculature, Dr. Otto says it is important to measure the severity of AS when the patient is normotensive. Patients who are hypertensive may have a little gradient, but when the blood pressure is reduced a significant gradient can be seen across the aortic valve.
“Another caveat,” Dr. Otto said, “is we may miss severe AS on echocardiography because measures of calcification are qualitative.” She said in these patients measuring by CT can be helpful, with different thresholds for women vs men.
For three categories of patients identified as having symptomatic severe AS (D1, D2, and D3), the guidelines now recommend aortic valve replacement as a class 1 recommendation, and Dr. Otto said these are the patients in whom the decision of surgery vs transcatheter valve implantation is most important.
For asymptomatic patients, a decision needs to be made whether to intervene now for the possibility of longer life, prevention of LV fibrosis and dysfunction, and improved quality of life, vs waiting, because when the patient gets a prosthetic valve there is a risk of that valve deteriorating as well as complications.
Dr. Otto and the researchers also looked at the evidence in the literature, with a goal of identifying markers of adverse outcomes in asymptomatic AS that are severe enough to justify early valve replacement before the onset of symptoms.
In addition to patients with severe symptomatic AS, the guideline in patients without symptoms that have a low ejection fraction is still a class 1 recommendation for valve replacement―also other cardiac surgery in a patient with severe AS.
For other indications, including exercise, tests showing a drop in BP or decreased exercise capacity, very severe AS, a high BNP, or rapid disease progression and low surgical risk, surgical aortic valve replacement is reasonable, but transcatheter is not recommended in these patients.
The final category where replacement may be considered is patients with a drop in ejection fraction to less than 60 but still over 50, or patients undergoing other cardiac surgery.
Catherine M. Otto, MD, reports no relevant disclosures.