Considering the high incidence of heart failure and degenerative aortic stenosis (AS) in the elderly, they often coexist. Aortic stenosis progresses gradually over time, and the aortic valvular area (AVA) decreases by 0.1 cm2 every year,1 contributing to left ventricular systolic dysfunction (LVSD) by increasing afterload.2 Aortic valve replacement is recommended in patients with severe AS when they experience symptoms and/or LVSD. According to this model, patients with moderate AS are a stable group, at intermediate risk, not requiring, yet, valve replacement. Nonetheless, patients affected with both conditions are subject to two different mechanisms for the increasing afterload: on one hand, the increased sympathetic activities typical of heart failure, and on the other the high transvalvular gradient of the aortic valve disease. In patients in whom AS occurs over a pre-existent left ventricular dysfunction, the added afterload increases, further magnifying the LVSD. In this situation, correction of the AS, albeit moderate, could improve the long-term survival. The theoretical benefit of the afterload reduction should be confronted with the high surgical risk of these patients.3
The key questions in the decision-making are
(1) Diagnosis: is it really a moderate AS?
The first point to consider is the degree of AS. Transthoracic echocardiography is the diagnostic mainstay for the diagnosis of AS.
- According to the results, patients are categorized as follow:
- Patients with increased flow but without increase in the mean gradient, and AVA which becomes larger than 1 cm2, thus with moderate AS, also defined as ‘pseudo-severe’.
- Patients with increased flow and mean gradient, fulfilling the definition of severe AS.
- Patients without flow increment, indicating lack of ventricular reserve, and unchanged parameters.
The echo-dobutamine test distinguishes severe from ‘pseudo-severe’ AS.
(2) Are the symptoms due to AS?
A recent observational study in patients with moderate AS and heart failure,4 revealed that 76% of the patients had symptoms, 32% were New York Heart Association Class III or IV, and many were admitted to the hospital for heart failure.
(3) Is the LVSD caused by AS?
Left ventricular systolic dysfunction could be secondary to the AS or be due to other causes, such as coronary artery disease. When the two conditions coexist, it is difficult to weight the impact of each disorder on the left ventricular function.5
- Treatment of patients with moderate AS and LVSD is complex and dependent from several variables:
- The rate of progression of the AS.
- The presence of coronary artery disease, aortic incompetence, or aortic dilation.
- The biological and vascular age of the patients.
- The presence of comorbidities such as sub-AS, multi-district atherosclerosis, chronic renal disease, chronic obstructive pulmonary disease, and cognitive disorders.
All patients with severe symptomatic AS should have prompt valve replacement procedure, the only contraindication is the presence of severe comorbidities or advanced age with an otherwise estimated survival less than a year.6 As a general rule, when the mean gradient is high, valve replacement is always recommended. On the other hand, when the mean gradient is low treatment is controversial. In patients with low-flow, low-gradient, and reduced ejection fraction (EF) AS, the reduced EF is mostly due to the increased afterload, and the left ventricle systolic function improves after valve replacement. When the reduced left ventricular systolic function is secondary to cardiomyopathy or extensive myocardial infarction, post-intervention improvement is less certain.
In general, patients with moderate AS, with or without decreased EF, including the ‘pseudo-severe’ form, should receive medical treatment.
The introduction of transcatheter aortic valve implantation, with its lower surgical risk, has been consider useful particularly for patients with severe AS and high or intermediate surgical risk.7,8 The same treatment could be attractive also for patients with moderate AS and left ventricular dysfunction. Reducing the afterload could improve the prognosis. This hypothesis will be tested in the TAVR UNLOAD (Transcatheter Aortic Valve Replacement to Unload the Left Ventricle in Patients with Advanced Heart Failure)9 study.
Conflict of interest: none declared.
References
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