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Outcome predictors identified in mitral regurgitation patients undergoing exercise echocardiography
In patients with significant myxomatous mitral regurgitation who underwent exercise echocardiography for symptom evaluation and risk stratification, lower exercise capacity, lower heart rate recovery, lower left ventricular ejection fraction, high resting right ventricular systolic pressure and atrial fibrillation have been identified as predictors of worse outcomes.
The findings are from an observational study of 884 asymptomatic patients with significant myxomatous mitral regurgitation (mean age, 58 years; 67% men). All patients underwent treadmill exercise echocardiography between January 2000 and December 2011.
“In asymptomatic patients with severe mitral regurgitation due to mitral valve prolapse, multiple findings on exercise echocardiography help predict long-term outcomes,” researcher Milind Y. Desai, MD, Heart and Vascular Institute, Cleveland Clinic, told Healio.com. “The longer you are able to exercise, the better your long-term outcomes. … Those patients with an abnormal heart rate recovery post-stress do poorly in the long run. Also, similar to prior reports, those with AF and high pressures in the right heart have worse outcomes.”
Milind Y. Desai
The primary endpoint was a composite of MI, stroke, all-cause mortality and progression to congestive HF during an average of 6.4 years of follow-up. The composite endpoint occurred in 10% of patients, including 44 deaths (5%), 36 cases of progression to congestive HF (4%), 13 strokes (1%), 13 transient ischemic attacks (1%) and six MIs (0.7%). These events occurred with similar frequency between patients who did and did not require mitral valve surgery (9% vs. 11%, respectively; P=.2).
Sixty-five percent of patients underwent mitral valve surgery during follow-up, including 520 patients who underwent valve repair and 56 who underwent valve replacement. New-onset AF developed in 13% of patients, and 4% and 1% of the cohort required implantation of pacemakers and implantable cardioverter defibrillators, respectively.
During exercise echocardiography, 70% of participants achieved a ratio of achieved-to-predicted metabolic equivalents (METs) of more than 100%, with 18% achieving 86% to 100% and 12% achieving less than 85%. Exercise capacity was determined according to the number of METs achieved during testing compared with a calculated number of expected equivalents according to patient age and sex.
The researchers identified a significant association between poor outcomes and exercise capacity (HR=0.9865; 95% CI, 0.9804-0.9887), heart rate recovery (HR=0.29; 95% CI, 0.17-0.5 for normal vs. abnormal recovery), resting right ventricular systolic pressure (HR=1.03; 95% CI, 1.004-1.05), AF (HR=1.91; 95% CI, 1.07-3.41) and resting LVEF (HR=0.96; 95% CI, 0.92-0.99), according to stepwise multivariate analysis.
Analysis of patient outcomes according to the ratio of achieved-to-expected METs indicated significantly more events with poorer exercise performance (7% for those with a ratio higher than 100%, 14% for 85%-100% and 20% for ratio lower than 85%; P<.001). Further division according to need for mitral valve surgery indicated the greatest frequency of events among patients who achieved less than 85% of expected METs and did not undergo surgery (23%), and the lowest frequency of events among patients with a ratio of 85% or higher and did not undergo surgery (6%; P<.001).
In the study, mean LVEF was 58%, indexed LV end-systolic dimension was 1.6 mm/m2, rest right ventricular systolic pressure was 31 mm Hg, peak-stress right ventricular systolic pressure was 46 mm Hg, METs achieved was 9.6 and heart rate recovery was 33 beats.
“To the best of our knowledge, this is one of the largest studies to investigate the significance of clinical, echocardiographic and exercise variables in predicting outcomes of such patients. We demonstrate that reduced age-gender predicted exercise capacity and improved [heart rate recovery] after exercise were independently associated with adverse long-term clinical outcomes, in addition to known factors like AF, pulmonary hypertension and reduced [LVEF].
“Exercise stress testing offers effective risk stratification in this population, where there is existing controversy regarding optimal timing of surgery. Additional prospective studies are needed to ascertain our observational results,” the researchers concluded.
Disclosure: The researchers report no relevant financial disclosures.