Color Doppler assessment of mitral regurgitation induced by supine exercise in patients with coronary artery disease

Echocardiographic quantitation of mitral regurgitation

Mitral valve regurgitation is a common valvular problem, particularly in developing nations. It causes significant morbidity and mortality, especially if the severity of valve regurgitation is underestimated. Echocardiography plays a significant role in the diagnoses, serial follow-up and management of patients with valvular heart disease. However, precise quantitation of the severity of mitral regurgitation is a crucial element in the therapeutic decisions for managing mitral regurgitation. An accurate assessment of the severity of mitral regurgitation allows for optimal timing of surgical intervention, culminating in improved patient outcomes. This review provides a systematic approach to the quantitation of mitral regurgitation using the echocardiography and Doppler methodologies that are available in the modern noninvasive imaging and hemodynamic laboratory. Additional, novel and evolving noninvasive imaging modalities are reviewed briefly.

The Use of Stress Echocardiography in the Assessment of Mitral Valvular Disease

Stress echocardiography plays an important role in evaluating asymptomatic patients with significant mitral stenosis and symptomatic patients with only mild disease at rest, as it correlates the exercise-induced symptoms with changes in transmitral gradients, pulmonary pressures, and mitral valve area. In patients with mitral regurgitation (MR), exercise or dobutamine protocols assess for the change in the degree of regurgitation and the pulmonary artery pressure (PAP) in response to high flow states, and detect underlying left ventricular (LV) dysfunction prior to valvular surgery. Exercise echocardiography also helps in the prognostic assessment of patients with mitral valve prolapse as new MR, or latent LV dysfunction may be provoked to identify a group of high risk individuals with normal resting echocardiographic parameters. Finally, it evaluates the proper functioning of prosthetic mitral valves and helps on the monitoring of transmitral gradients and PAPs after mitral valve surgery.

The effect of exercise on ischemic mitral regurgitation

This study investigated the effect of dynamic exercise on mitral regurgitation (MR) as assessed by color flow Doppler imaging and tested the hypothesis that MR increases in patients with left ventricular (LV) function worsening during exercise. We studied 513 patients (390 men, 123 women:mean age [+/-1 SD] 58+/-11 years) referred for treadmill exercise echocardiography (EE) to evaluate known or suspected coronary artery disease. Normal EE was seen in 182 (36%), necrosis in 131 (25%), and ischemic response (with or without necrosis) in 200 (39%). MR assessment was performed at rest and immediately postexercise, on the basis of the mosaic area. At rest, mild MR (<3 cm2) was seen in 138; moderate (3 to 6 cm2) was seen in 21; and severe (>6 cm2) was seen in 5. Forty-two patients developed new, mild (n=35), moderate (n=6), or severe (n=1) MR during exercise. Patients were assigned to three groups: group 1--new or increased MR from rest to exercise (n=70); group 2--MR at rest unchanged or decreased (n=136); and group 3--no MR at rest and exercise (n=307). At rest, LV ejection fraction (EF) and wall motion score index (WMSI) were similar in group 1 and group 2 but improved in group 3 (EF: group 1, 51+/-11%; group 2, 53+/-10%; group 3, 56+/-8%, p<0.001 vs group 1 and group 2. WMSI: group 1, 1.3+/-0.3; group 2, 1.3+/-0.4; group 3, 1.1+/-0.2, p<0.01 vs group 1, p<0.001 vs group 2). At exercise, EF and WMSI were impaired in group 1 (EF: group 1, 52+/-14%; group 2, 58+/-15%; group 3, 64+/-11%, p<0.001 vs group 1 and group 2; p<0.05 between group 1 and group 2. WMSI: group 1, 1.5+/-0.4; group 2, 1.4+/-0.4; group 3, 1.2+/-0.3, p<0.001 vs group 1 and group 2, p<0.05 between group 1 and group 2). An ischemic response was common in group 1 (67% vs 35% in group 2 and 34% in group 3, p<0.001 between group 1 and group 3 and between group 1 and group 2). Accordingly, in group 1 patients, exercise time was diminished (7.3+/-2.7 vs 8.4+/-2.7 in group 2 and 9.3+/-2.4 in group 3, p<0.01, between group 1 and group 2, p<0.001 between group 1 and group 3, p<0.001 between group 2 and group 3) and the number of severely narrowed coronary vessels greater (2.4+/-0.9 vs 1.7+/-1.0 in group 2 and 1.7+/-1.0 in group 3). In conclusion, MR does not increase in most patients submitted to dynamic exercise echocardiography. However, if MR develops, severe LV function worsening should be suspected.

Exercise-induced mitral regurgitation is a predictor of morbid events in subjects with mitral valve prolapse

OBJECTIVES

This study attempted to determine whether a subset of patients with mitral valve prolapse and no mitral regurgitation at rest will develop mitral regurgitation during exercise and have a higher than anticipated risk of morbid cardiovascular events.

BACKGROUND

Mitral regurgitation in patients with mitral valve prolapse identifies a subset of patients at higher risk for morbid events. However, mitral regurgitation in patients with mitral valve prolapse may be intermittent and could go unrecognized. A provocative test to unmask mitral regurgitation in these patients would be useful.

METHODS

Ninety-four adult patients with mitral valve prolapse and no mitral regurgitation at rest were studied during supine bicycle ergometry using color flow Doppler echocardiography in the apical four-chamber and long-axis views. Patients were prospectively followed up for morbid events.

RESULTS

Thirty (32%) of 94 patients had exercise-induced mitral regurgitation. Prospective follow-up (mean 38 months) showed more morbid events in the group with than without mitral regurgitation and included, respectively, syncope (43% vs. 5%, p < 0.0001), congestive heart failure (17% vs. 0%, p < 0.005) and progressive mitral regurgitation requiring mitral valve replacement surgery (10% vs. 0%, p < 0.05). Cerebral embolic events, endocarditis or sudden death were rare and not different between groups.

CONCLUSIONS

In patients with mitral valve prolapse without mitral regurgitation at rest, exercise provokes mitral regurgitation in 32% of patients and predicts a higher risk for morbid events.

Influence of pacing-induced myocardial ischemia on left atrial regurgitant jet: a transesophageal echocardiographic study

OBJECTIVES

We investigated the influence of pacing-induced myocardial ischemia on systolic regurgitant jet in the left atrium, using simultaneous transesophageal echocardiography and transesophageal atrial pacing.

BACKGROUND

In vitro studies have shown that ischemia-induced mitral regurgitation may occur as a result of mitral leaflet malcoaptation or (global) left ventricular dysfunction. However, no transesophageal echocardiographic study has thus far been performed to demonstrate the mechanism and extent of mitral regurgitation during myocardial ischemia in patients.

METHODS

In 24 patients (mean [+/- SD] age 57 +/- 10 years) with (15 patients) and without (9 control subjects) coronary artery disease, heart rate, blood pressure and systolic regurgitant jet were assessed before and immediately after pacing. Pacing was increased stepwise up to 160 beats/min to provoke wall motion abnormalities while the left ventricular short axis was monitored at the midpapillary muscle level. Other variables obtained before and at peak pacing included left ventricular end-diastolic and end-systolic areas and left ventricular end-diastolic and end-systolic endocardial segmental lengths.

RESULTS

Heart rate and blood pressure before and after pacing were not significantly different in control subjects or in patients. At baseline, a jet was present in all but three control subjects. New or increased anterior or posterior wall motion abnormalities were observed during pacing in seven and eight patients, respectively. End-systolic left ventricular areas and segment lengths were significantly reduced in control subjects compared with patients with coronary artery disease at peak pacing (p < 0.05). The increase in systolic regurgitant jet was significantly greater in patients (2.0 +/- 1.1 to 3.1 +/- 1.8 cm2 vs. 0.7 +/- 0.7 to 0.9 +/- 0.9 cm2 [after pacing], p < 0.01). This effect was greater in patients with posterior than with anterior wall motion abnormalities (3.5 +/- 1.6 vs. 2.1 +/- 1.2 cm2 [after pacing], p < 0.05).

CONCLUSIONS

Quantitative changes in geometry and function of the left ventricle caused by pacing-induced myocardial ischemia augments systolic regurgitant jet size. An increase in the jet during atrial pacing is associated with new or increased wall motion abnormalities, especially of the posterior wall. Pacing-induced anterior wall motion abnormalities appear not to be related directly to an increase in the jet.

Exercise echocardiography in combined mild mitral valve stenosis and regurgitation

Dynamic mitral regurgitation (MR) is typically associated with either severe systolic left ventricular dysfunction or episodes of acute myocardial ischemia. We report three patients with mild combined mitral stenosis and regurgitation and normal global left ventricular systolic function who presented with severe exertional dyspnea. Upright bicycle exercise echocardiography revealed development of severe dynamic MR in all three cases with Doppler evidence of severe pulmonary hypertension. There was no echocardiographic or electrocardiographic evidence of ischemia. Exercise echocardiography is an established tool for assessing dynamic changes in transvalvar pressure gradients. These results suggest that exercise echocardiography may also be useful for evaluating changes in severity of MR and for the assessment of dynamic changes in pulmonary artery systolic pressures.

Prognostic value of dobutamine echocardiography in patients with high pretest likelihood of coronary artery disease

To examine the value of transient regional asynergy on dobutamine stress echocardiography as a noninvasive predictor of future cardiac events, 51 symptomatic patients (aged 54 +/- 9 years) with suspected coronary artery disease (CAD) were studied using an incremental regimen of 5, 10, 15 and 20 micrograms/kg/min. Pretest likelihood of CAD was (mean +/- standard error of the percentage) 79.7 +/- 5.6% before and 83.4 +/- 5.2% after exercise electrocardiography using probability analysis based on age, sex and symptoms. Two-dimensional images were analyzed with reference to an 11-segment model and gave good interrater agreement. During 24 +/- 4 months (range 19 to 32) of follow-up, 23 patients had events (1 myocardial infarction, 9 unstable angina, 10 coronary bypass surgery, 3 coronary angioplasty) and 28 were event free. Age, proportion with baseline asynergy and both pretest echocardiographic ejection fraction and its response to dobutamine were similar in these 2 groups (all p = not significant). Transient asynergy was seen in 17 of 23 patients (74%) with and 8 of 28 patients (29%) without events (p < 0.01); 5 of 6 patients (83%) with involvement of 3 segments had events. Myocardial infarction or unstable angina occurred in 8 of 25 (32%) with a positive and 2 of 26 (8%) with a negative stress echocardiogram (p < 0.05). Both exercise duration (389 +/- 195 vs 517 +/- 237 seconds, p < 0.05) and time to diagnostic ST-segment shift (291 +/- 192 vs 447 +/- 212 seconds, p = 0.05) were shorter in those with inducible asynergy.(ABSTRACT TRUNCATED AT 250 WORDS)

Dobutamine stress echocardiography for detection and assessment of coronary artery disease

Stress echocardiography with dobutamine infusion for detection of coronary artery disease is a potential alternative to exercise stress testing with some theoretic advantages. Fifty patients who were not receiving cardioactive medication were prospectively studied with two-dimensional echocardiography and 12-lead electrocardiography (ECG) during incremental dobutamine infusion (5, 10, 15 and 20 micrograms/kg body weight per min, each dose for 8 min). Images were analyzed by using an 11-segment left ventricular model. All patients underwent correlative exercise ECG and coronary angiography, which revealed normal coronary arteries in 14 and significant disease (greater than or equal to 70% diameter stenosis) in 36. Peak rate-pressure product during dobutamine infusion was 18,845 +/- 4,156 versus 23,740 +/- 6,158 mm Hg/min on exercise (p less than 0.01). Interobserver concordance for wall motion analysis was good (kappa coefficient = 0.77). The use of baseline (n = 14) or reversible (n = 24) regional asynergy to define an abnormal dobutamine echocardiogram resulted in a sensitivity for detecting coronary artery disease of 78% and a specificity of 93%. Corresponding data for the dobutamine ECG were 47% and 71% and for the exercise ECG were 72% and 71%, respectively. The development of new mitral regurgitation on Doppler color flow imaging (n = 4) improved sensitivity to 81% without loss of specificity. Inducible asynergy or new mitral regurgitation was observed in 6 (50%) of 12 patients with single-, 6 (60%) of 10 with double- and 12 (86%) of 14 with triple-vessel disease. The site of transient asynergy provided additional localizing information. Exercise duration and time to diagnostic ST segment shift were shorter in patients with coronary artery disease with versus those without echocardiographic evidence of ischemia (both p less than 0.05). Side effects during dobutamine infusion were mild and short-lived. Dobutamine stress echocardiography is well tolerated, is useful for detection and assessment of coronary artery disease and is applicable to patients unable to exercise.

Exercise Doppler: functional evaluation of right heart dynamics

Exercise echocardiography is a versatile technique that includes not only two-dimensional imaging, but also Doppler of aortic, mitral, and tricuspid valves. Doppler echocardiography can be useful in the evaluation of global left ventricular systolic and diastolic function, valvular function, transvalvular gradients, and pulmonary artery pressure. The technique lends itself to the study of the cardiac response to exercise in a variety of disease states, including pulmonary, coronary artery, valvular, and congenital heart disease. We review our experience using agitated saline-enhanced Doppler of tricuspid insufficiency to determine pulmonary artery pressure throughout exercise in chronic lung disease.

Influence of exercise-induced myocardial ischemia on the pattern of left ventricular diastolic filling: a Doppler echocardiographic study

Previous studies using Doppler echocardiography to evaluate left ventricular diastolic filling have shown that myocardial ischemia induced by coronary balloon angioplasty or atrial pacing results in a decrease in the left ventricular inflow peak early (E) to peak atrial (A) velocity ratio. To investigate the effects of exercise-induced ischemia on Doppler-derived filling variables, 20 patients with coronary artery disease and exercise-induced electrocardiographic changes and regional wall motion abnormalities determined by two-dimensional echocardiography were evaluated and compared with 20 patients without evidence of exercise-induced ischemia. Doppler echocardiography was performed at rest and immediately after exercise before the resolution of exercise-induced wall motion abnormalities. Peak E and A velocities increased from rest to postexercise in both the ischemic and nonischemic groups, although the ischemic group demonstrated a greater increase in peak E velocity (from 68 +/- 15 cm/s at rest to 88 +/- 22 cm/s after exercise) than the nonischemic group (70 +/- 13 to 77 +/- 18 cm/s) (p less than 0.05 for the difference in response between groups). Accompanying these changes was a slight increase in the peak E/A velocity ratio in the ischemic group (1.04 +/- 0.28 at rest to 1.13 +/- 0.42 after exercise) versus a decrease in the nonischemic group (1.07 +/- 0.30 to 0.90 +/- 0.28) (p less than 0.05 intergroup difference).(ABSTRACT TRUNCATED AT 250 WORDS)