Feasibility of Myocardial Performance Index for Evaluation of Left Ventricular Function during Dobutamine Stress Echocardiography before and after Coronary Artery Bypass Grafting

Interval Changes in Myocardial Performance Index Predict Outcome in Severe Sepsis

OBJECTIVES

Septic cardiomyopathy is a well-described consequence of septic shock and is associated with increased sepsis-related mortality. The myocardial performance index (MPI), a parameter derived from echocardiographic tissue Doppler measurements, allows for a more sensitive assessment of global cardiac function than do traditional metrics for cardiac function. The authors hypothesized that changes in left ventricular MPI in patients with severe sepsis would be associated with a higher 90-day mortality.

DESIGN

Prospective, observational study.

SETTING

Intensive care units of a tertiary medical center.

PARTICIPANTS

The study comprised 47 patients admitted with new diagnoses of severe sepsis or septic shock.

INTERVENTIONS

All patients underwent transthoracic echocardiograms with assessment of MPI at enrollment and 24 hours later. Hemodynamic data and information on sepsis-related mortality were collected. In the primary analysis, the association between change in MPI from enrollment to 24 hours and sepsis-related 90-day mortality was assessed.

MEASUREMENTS AND MAIN RESULTS

Of the 47 patients enrolled, 30 demonstrated an improvement in MPI from 0 to 24 hours ("improved" group), and MPI worsened in the remaining 17 patients ("worsened" group). Despite no significant differences in ejection fraction or severity of illness, the median MPI at enrollment in the "improved" group was higher than baseline values in the "worsened" group (p = 0.005). A worsening MPI over the 24-hour study interval was associated with increased mortality at 90 days (p = 0.04), which remained significant (hazard ratio 3.72; 95% confidence interval 1.12-12.41; p = 0.03) after adjusting for severity of illness (Acute Physiology and Chronic Health Evaluation II score), intravenous fluids, and vasopressor use.

CONCLUSIONS

In patients admitted to the intensive care unit with a diagnosis of severe sepsis or septic shock, a worsening MPI during the first 24 hours after intensive care unit admission was associated with higher 90-day mortality.

Cardiac function assessed by exercise echocardiography on the first morning after coronary artery bypass grafting

Cardiac surgery patients are urged to resume light physical activity on the first postoperative day, even if cardiac function may not have recovered fully after the operation. To elucidate the postoperative recovery process, we examined cardiac surgery patients with exercise echocardiography before and on the first day after the operation. Patients undergoing on-pump coronary artery bypass grafting were examined with echocardiography during semirecumbent cycle exercise. Patients exercised for five minutes at 10 W intensity and five minutes at 30 W intensity in bed with the upper body supported to approximately 30°. Fourteen patients were studied. Mitral annulus excursion and pulsed wave Doppler from the left ventricular outflow tract indicated postoperatively reduced cardiac stroke volume. Early diastolic tissue velocities of the mitral annulus were reduced, and early trans-mitral flow velocity was increased. The ratio between early mitral flow velocity and early diastolic mitral tissue velocity was increased postoperatively, indicating impaired left ventricular relaxation and increased left atrial pressure. Postoperative systolic mitral annulus tissue velocities were similar to preoperative velocities, indicating maintained systolic function. Postoperative exercise was associated with improvements in myocardial function indices and cardiac stroke volume similar to preoperative improvements. There were no signs of further deterioration in myocardial function during 30 W exercise. In summary, reduced left ventricular diastolic function after surgery resulted in reduced cardiac stroke volume, increased left atrial pressure and a higher rate of perceived exertion on the first postoperative day.