Role of Exercise Stress Testing in Mitral Regurgitation

Exercise Stress Echocardiography Protocol

Images should be acquired at baseline and immediately postexercise when using a treadmill, or at baseline, low workload and peak exercise when using a semisupine bicycle ergometer. Exercise imaging allows quantification of changes in valvular regurgitation severity, left ventricular (LV) function, and pulmonary arterial pressure. A symptom-limited graded exercise test is recommended (patients should be encouraged to exercise until exhaustion), and at least 80% of the age-predicted upper heart rate should be reached in absence of symptoms. The test should be performed under the supervision of an experienced physician. Typically, the initial workload of 25 W is maintained for 2 minutes, and the workload is increased every 2 minutes by 25 W ( Fig. 100.1 ). An increase in steps of 10 W seems more appropriate in patients with a low level of physical activity (i.e., secondary MR in heart failure). In practice, image recordings are obtained in a stepwise fashion at baseline; at low, medium, and high levels of exercise; and at peak test (see Fig. 100.1 ). Images and loops are stored and analyzed offline after the test; often no measurements are done during image acquisition. Usually the following imaging sequence is used:

• 1.

  Two-dimensional (2D) grayscale loops (frame rate >50–70/s) of the left ventricle in four-, two-, and three-chamber views for global and regional LV systolic function assessment

• 2.

  Mitral annulus tissue Doppler velocities (∼95–105 beats/min, before e′- and a′-wave fusion) and mitral inflow with pulsed-wave Doppler (close to e′ recording) to evaluate LV filling pressures

• 3.

  Color-flow Doppler of the MR for quantification of severity by the proximal isovelocity surface area (PISA) method and vena contracta and continuous-wave Doppler on the MR for quantification of severity by the PISA method

• 4.

  Continuous-wave (CW) Doppler of the tricuspid regurgitant jet to assess the transtricuspid pressure gradient and estimate the systolic pulmonary artery pressure (sPAP). To better identify patients with a rapid increase in pulmonary artery pressure at first stages of the exercise, CW Doppler of the tricuspid regurgitant jet should be the first parameter to be acquired before each level of exercise.

• 5.

  Dobutamine stress echocardiography is rarely used to assess MR dynamic behavior because of its nonphysiologic effect on the severity of regurgitation; the only exception is when ischemia is the suspected mechanism of MR.

Primary Mitral Regurgitation

Indications For Stress Echocardiography

In patients with severe MR, symptoms predict poor outcome after valve repair or replacement. Reduced LV ejection fraction (LVEF) and LV dilatation are also important predictors of postoperative LV dysfunction and subsequent cardiac morbidity and mortality. Therefore, when patients with severe MR become symptomatic or develop LV dysfunction or dilatation (decrease in LVEF or increase in LV end-systolic diameter), mitral valve (MV) surgery, especially repair, is mandatory ^{, ,} ( Fig. 100.2 ). American and European guidelines consider reasonable to perform an exercise Doppler echocardiography in symptomatic patients when there is a discrepancy between symptoms and severity of MR at rest or when LV and left atrial (LA) enlargement seem out of proportion to the severity of resting MR. ^, In such cases, the increase of MR severity or sPAP during exercise and the absence of LV contractile reserve may explain symptoms and justify mitral surgery. Moreover, stress echocardiography is recommended in patients who claim to be asymptomatic to objectively evaluate exercise tolerance and symptoms because symptoms may be unrecognized by the patient (e.g., progressive disease, patient who unconsciously limit physical activity to avoid symptoms).