When Is Aortic Stenosis Severe Enough to Warrant Surgical Intervention?

Gregory W. Rutecki, MD

Volume 56 - Issue 9 - September 2016

Aortic stenosis (AS) is not a problem that is unknown to primary care providers. Besides being the most common valvular abnormality in the developed world, 3 of 100 individuals between the ages of 75 and 85 years harbor this sinister valvular lesion.1 

Because surgery is the only treatment modality that has been documented to reduce mortality in cases of AS, the decision about when to operate on a patient is critical.1 Answering “when” can be easy in some circumstances but not in others. If a patient with AS also has exertional angina, syncope, or dyspnea, surgery is indicated.

But what if you are managing a patient with high-gradient AS who is asymptomatic? Now things get a little tougher. The authors of this month’s Top Paper1 attempted to answer this question with a review of the guidelines for valve replacement to help determine which patients with AS should be considered for early intervention, even if they have no symptoms.

Some of the cardiac alterations accompanying this clinical scenario have been proven to decrease longevity.2 After the history and physical examination (looking for the presence of a systolic murmur suggesting AS, the time of peaking of the murmur [later is worse], pulsus parvus et tardus, and a decreased or absent left ventricular S2), echocardiography and other noninvasive studies are most helpful. Older and newer echocardiographic and other findings suggesting increasing severity are reviewed.1

To begin with, echocardiographic findings suggestive of severe AS include a mean pressure gradient across the valve of greater than 40 mm Hg, a peak aortic jet velocity of greater than 4 m/s, and an aortic valve area less than 1 cm2. What other findings suggest a heightened severity?

Treadmill Exercise Testing

“Careful” treadmill exercise testing (using a supervised modified Bruce protocol) is helpful. When the authors of one prospective study3 used treadmill testing in patients with severe asymptomatic AS, 22 of the 66 patients developed symptoms (complex ventricular arrhythmias, decreased blood pressure, and/or ST segment changes) and had a worse prognosis; the 2-year event-free survival rate was 19% for patients with positive treadmill exercise test results compared with 85% for patients with negative results!

Echocardiography

From the perspective of echocardiography, left ventricular hypertrophy, an increased left atrial size, and global left ventricular longitudinal strain (GLVS) may be used to assess patients with AS.1 Strain may be defined as measuring the deformation of a solid object—in this case, the myocardium.1 Specialized techniques (tissue Doppler and “speckle-tracking” echocardiography techniques) are applied. In one study4 of 146 patients with AS, all with preserved ejection fractions, GLVS was an independent predictor of all-cause mortality (hazard ratio, 1.38; 95% confidence interval, 1.20-1.60; P < .001).

BNP Testing

Finally, assessing levels of B-type natriuretic peptide (BNP) is one test that is ordered and interpreted by primary care providers and that also benefits the population with AS. There is evidence demonstrating a correlation between BNP levels and the severity of AS.1 In one study, patients with asymptomatic AS and BNP levels below 130 pg/mL had a 1-year symptom-free survival rate of 66% compared with a rate of 34% in matched patients with BNP values of 130 pg/mL and above.5

Even if they cannot perform the echocardiography themselves or interpret the GLVS study results, primary care providers can play a key role in the treatment of patients with AS and help determine when valve replacement is necessary.

Gregory W. Rutecki, MD, is a physician at the National Consult Service at the Cleveland Clinic. He is also a member of the Consultant editorial board.

References:

  1. McCarthy CP, Phelan D, Griffin B. When does asymptomatic aortic stenosis warrant surgery? Assessment techniques. Cleve Clin J Med. 2016;83(4):271-280.
  2. Mihaljevic T, Nowicki ER, Rajeswaran J, et al. Survival after valve replacement for aortic stenosis: implications for decision making. J Thorac Cardiovasc Surg. 2008;135(6):1270-1279.e12.
  3. Amato MCM, Moffa PJ, Werner KE, Ramires JAF. Treatment decision in asymptomatic aortic valve stenosis: role of exercise testing. Heart. 2001;​86(4):​381-386.
  4. Kearney LG, Lu K, Ord M, et al. Global longitudinal strain is a strong independent predictor of all-cause mortality in patients with aortic stenosis. Eur Heart J Cardiovasc Imaging. 2012;13(10):827-833.
  5. Bergler-Klein J, Klaar U, Heger M, et al. Natriuretic peptides predict symptom-free survival and postoperative outcome in severe aortic stenosis. Circulation. 2004;109(19):2302-2308.