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Management of Asymptomatic Severe Aortic Stenosis
Abstract & Commentary
By Jonathan Abrams, MD, Professor of Medicine, Division of Cardiology, University of New Mexico, Albuquerque. Dr. Abrams reports no financial relationships relevant to this field of study.
Source: Rosenhek R, et al. Natural history of very severe aortic stenosis. Circulation. 2010;121:151-156.
Calcific aortic stenosis (AS) in older subjects is an important problem, but should the aortic valve be replaced? It is widely accepted that severe symptomatic AS patients should be seriously, even urgently, considered for AV replacement, particularly if there is evidence of early heart failure. This report from the Medical University of Vienna and Vienna Medical General Hospital provides guidelines for potential aortic valve surgical intervention by examining the assessment of such subjects with a careful clinical history. Clues include early LV decompensation, overt CHF, decreased effort tolerance, a severely narrowed and/or heavily calcified aortic valve annulus, and a high jet velocity.
The ACC/AHA guidelines in the United States consider peak aortic valve velocity very important in subjects who have a peak aortic jet velocity of > 5.0 m/s, a mean gradient of > 60 mm Hg, or an aortic valve area of < 0.6 cm2. This has been used as a class IIb indication, with an operative mortality rate projected as < 1%. This study prospectively addresses AS subjects from 1995–2008, who have severe AS and an AV peak velocity greater than or equal to 5.0 m/s. The 116 patients studied had a mean age of 67 ± 15 years and an average peak aortic velocity of 5.37 m/s. No other significant cardiac problems were allowed in the study. Echocardiographic data was used to measure all important parameters, including the degree of valve calcification (although the article does not appear to include mandatory serial echo examinations).
Patients were followed every six months. Exercise testing was performed in select subjects who may have had angina, incipient CHF, or other suggestive symptoms. This is a prospective natural history report of a large number of asymptomatic patients with very severe aortic stenosis, with assessment of patient outcomes. It should be recognized that advances in echo technique/quality over the past 15 years of follow up may affect the data.
Many experts have used a watchful waiting approach (for symptoms) for aortic valve replacement in asymptomatic patients with significant gradients. Others have used a semi-urgent waiting approach to aortic surgery in the presence of a large aortic gradient and presumed need for AV replacement without waiting for symptoms. Rosenhek et al believe that an early consideration for AV replacement may be preferred in many asymptomatic patients with severe aortic disease.
Results: There were 96 events that occurred during follow-up. Event-free survival was 64% at one year, 36% at two years, 25% at three years, 12% at four years, 3% at six years. Six cardiac deaths occurred. All patients were asymptomatic at their last examination. Aortic valve surgery occurred in 90 patients: 73 developing symptoms, 10 with severe calcification (rapid progression), four positive exercise tests, two reduced function of the left ventricle, and one elective surgery. Prognostic factors included peak aortic jet velocity, which was correlated with event-free survival. With a peak aortic jet velocity between 4.0 and 5.0 m/s, 82% survived at one year, 70% at two years; 49% at three years. Event-free survival rates were even worse in patients with severe AS, aortic velocity greater than or equal to 5.5 m/s: 44% at one year, 25% at two years, 11% at three years (p < 0.0001). Patients with a higher jet velocity had more pronounced symptoms in addition to a shorter time to symptom onset. Of interest, aortic valve area did not provide additional prognostic information in this high-risk group. The outcome of patients with an aortic valve area < 0.6 cm2 was not significantly different from the outcome of those with a valve area greater than or equal to 0.6 cm2. Valve areas were not significantly different between patients presenting with a peak jet velocity of 5.0 and 5.5 m/s. All but seven patients had moderately to severely calcified aortic valve. However, valve calcification was not associated with event-free survival. Coronary artery disease was present in 26 patients. A prior study done by the same investigators reported an even worse prognosis in patients with CAD and aortic valve stenosis. The authors concluded that, in asymptomatic AS, surgery can wait, presumably safely, if monitored very closely.
This study shows that the outcomes of a specific group of patients with very severe aortic stenosis can help guide management of severe AS patients without symptoms. The recommendations regarding severe AS may have shifted a bit with this publication, in that there is a reasonable amount of room for severe AS and no other abnormalities as long as none of the high-risk factors defined in this study are encountered. This is good news, but AV surgery still requires careful planning for the management of these patients' care.
The major finding in this study is that patients with asymptotic, but very severe, aortic valve stenosis with calcification should be carefully observed, with a low threshold for surgery if dense calcification, angina, or any degree of congestive heart failure occur. Patients with severe AS, but no symptoms, should be watched carefully with an echocardiogram yearly. The emphasis on the degree of calcification may not be a useful guide, although it is emphasized by the authors and has been reported in other studies. Severe AS with no symptoms can be followed carefully, and is felt to be less dangerous according to the authors, but this seems questionable. These patients should be followed every six months to a year. Following these guidelines should ensure safety for severe AS patients, but the onset of symptoms demands rapid evaluation.