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Stress testing and strain echocardiography yielded novel predictors of mortality among asymptomatic patients with mitral regurgitation and preserved ejection fraction, a single-center study showed.

On multivariable analysis, patients were more likely to die during 8.3-year follow-up if they had:

• Higher Society of Thoracic Surgeons score (HR 1.14, 95% CI 1.04-1.25)
• More abnormal resting left ventricular (LV) global longitudinal strain (HR 1.60, 95% CI 1.47-1.73)
• Higher baseline right ventricular systolic pressure (HR 1.35, 95% CI 1.10-2.32)
• Lower exercise capacity, or a lower percentage of expected metabolic equivalents (HR 1.13, 95% CI 1.04-1.22)

For a model for long-term mortality -- consisting of STS score, resting right ventricular systolic pressure, LV end-systolic dimension, and mitral effective regurgitant orifice -- adding the variable of predicted metabolic equivalents yielded an improvement in C-statistic from 0.61 to 0.69 (P<0.01). Resting LV global longitudinal strain raised the C-statistic even further, to 0.78 (P<0.01), according to , of the Cleveland Clinic, and colleagues in the .

"We found that worsening baseline resting LV global longitudinal strain and reduced exercise capacity were independently associated with mortality, providing additive (rather than duplicative) prognostic utility to previously known predictors," the authors concluded.

Mitral valve surgery, on the other hand, was linked to improved survival (HR 0.82, 95% CI 0.70-0.96).

"By demonstrating worse outcome in the subgroup of patients with subclinical myocardial impairment despite normal LV ejection fraction and dimensions, the data ... challenge the current definitions of the watchful waiting strategy and offer clarification for failure of this strategy in some patients," according to , and , both of Belgium's Ziekenhuis Oost-Limburg.

"Incorporation of an LV global longitudinal strain threshold in the clinical decision algorithm will fine-tune the decision toward anticipated surgery, particularly in the subset of patients at highest risk. Conversely, in patients with optimal LV global longitudinal strain, surgery might be safely delayed for many years," the duo wrote in an accompanying editorial.

Desai's observational study included 737 consecutive asymptomatic patients with normal LV dimensions and LV ejection fractions of 60% or more. Each individual visited the Cleveland Clinic from 2000 to 2011 and had echocardiograms recorded. Two-thirds (65%) of patients got subsequent mitral valve surgery after a median of 3 months.

More than 8 years later, 9% had died (no deaths within 30 days of surgery)

Median LV global longitudinal strain was -21.7% at baseline. Desai and colleagues determined that LV global longitudinal strain better than -21% was a reasonable cutoff for good 5-year survival.

Similarly, metabolic equivalents at 100% were associated with enhanced survival to 5 years.

Bertrand and Vandervoort noted the remaining need for prospective multicenter data, as Cleveland Clinic is a "highly experienced valve center with extremely low operative morbidity and mortality."