The myocardial performance index during low-dose dobutamine echocardiography in control subjects and patients with a recent myocardial infarction: a new index of left ventricular functional reserve?

The Assessment and Potential Implications of the Myocardial Performance Index Post Exercise in an at Risk Population

BACKGROUND

The myocardial performance index (MPI) first described by Chuwa Tei in 1995 is a relatively new echocardiographic variable used for assessment of overall cardiac function. Previous studies have demonstrated the MPI to be a sum representation of both left ventricular systolic and diastolic function with prognostic value in patients with coronary artery disease as well as symptomatic heart failure.

METHODS

Ninety patients with either established coronary artery disease (CAD) or CAD risk factors underwent routine treadmill exercise stress testing with two-dimensional Doppler echocardiography using the standard Bruce protocol. Both resting and stress MPI values were measured for all 90 of the patients.

RESULTS

Using a normal MPI cut off of ≤ 0.47, the prevalence of an abnormal resting MPI in our 90 subjects was 72/90 or 80% and the prevalence of an abnormal stress MPI in our 90 subjects was 48/90 or 53.33%. The average MPI observed in the resting portion of the stress test for the cohort was: 0.636 with a standard deviation of 0.182. The average MPI in the stress portion of the stress test for the cohort was 0.530 with a standard deviation of 0.250. The P value with the use of a one-tailed dependent T test was calculated to be < 0.05.

CONCLUSION

We postulate that these findings reflect that the MPI (Tei) index assessed during exercise may be a sensitive indicator of occult coronary disease in an at risk group independent of wall motion assessment.

Doppler-derived myocardial performance index in patients with impaired left ventricular relaxation and preserved systolic function

BACKGROUND

The Doppler-derived myocardial performance index (MPI) has been used in the evaluation of left ventricular (LV) function in several diseases. In patients with isolated diastolic dysfunction, the diagnostic utility of this index remains unclear. The aim of this study was to determine the diagnostic utility of MPI in patients with systemic hypertension, impaired LV relaxation, and normal ejection fraction.

METHODS

Thirty hypertensive patients with impaired LV relaxation were compared to 30 control subjects. MPI and its components, isovolumetric relaxation time (IRT), isovolumetric contraction time (ICT), and the ejection time (ET), were measured from LV outflow and mitral inflow Doppler velocity profiles.

RESULTS

MPI was higher in patients than in control subjects (0.45 +/- 0.13 vs 0.37 +/- 0.07 P < 0.0029). The increase in MPI was due to the prolongation of IRT without significant change of ICT and ET. MPI cutoff value of > or =0.40 identified impaired LV relaxation with a sensitivity of 63% and specificity of 70% while an IRT >94 ms had a sensitivity of 67% and specificity of 80%. Multivariate analysis identified relative wall thickness, mitral early filling wave velocity (E), and systolic myocardial velocity (Sm) as independent predictors of MPI in patients with hypertension.

CONCLUSIONS

MPI was increase in patients with hypertension, diastolic dysfunction, and normal ejection fraction but was not superior to IRT to detect impaired LV relaxation.

Effect of changes in contractility on the index of myocardial performance in the dysfunctional left ventricle

BACKGROUND

The index of myocardial performance has prognostic power in patients with cardiomyopathy and following myocardial infarction. As the index of myocardial performance has been shown to be preload and afterload dependent, the effect of altering contractility on IMP and its components with left ventricular dysfunction has been incompletely delineated.

METHODS

Chronic left ventricular dysfunction was induced in 10 canines using coronary microsphere embolization. Each dog was instrumented and imaged with 2D echo and Doppler. At the same atrially paced rate, contractility was increased with a dobutamine infusion and then following 4 weeks of oral digoxin.

RESULTS

With chronic left ventricular dysfunction, a reduced left ventricular ejection fraction (42 +/- 3%, p < 0.001) and increased index of myocardial performance (0.58 +/- 0.17, p < 0.01) due to isovolumic contraction time lengthening and shortened left ventricular ejection time were noted. Dobutamine increased ejection fraction (p < 0.001), reduced left ventricular end diastolic pressure (p < 0.01), and reduced the index of myocardial performance (0.33 +/- 0.17, p < 0.001) due to isovolumic contraction time, isovolumic relaxation time, and left ventricular ejection time shortening. Digoxin increased ejection fraction (p < 0.05), reduced left ventricular end diastolic pressure (p < 0.05), and reduced the index of myocardial performance (0.42 +/- 0.13, p < 0.01) due to isovolumic contraction time shortening (p < 0.001). Both dobutamine and digoxin lengthened the diastolic filling period (p < 0.01).

CONCLUSION

Increased inotropy with digoxin and dobutamine reduced the index of myocardial performance in dogs with left ventricular dysfunction. Shortened isovolumic contraction time, increased diastolic filling period, and reduced left ventricular end diastolic pressure with digoxin may provide insight into its efficacy in heart failure.

Traditional and Color M-Mode Parameters of Left Ventricular Diastolic Function During Low-dose Dobutamine Stress Echocardiography: Relations to Contractility Reserve

BACKGROUND

Cross-sectional studies reported that left ventricular (LV) systolic and diastolic functions are correlated. However, whether changes in wall-motion score index (WMSI) or 2-dimensional ejection fraction (EF) predict changes of Doppler parameters of LV diastolic function is unclear.

METHODS

Patients with known or suspected history of coronary artery disease underwent assessment of LV systolic function (WMSI, EF) and diastolic function at baseline and during stress echocardiography by low-dose dobutamine (LDD) (peak infusion 10 microg/kg/min). Peak velocities of early (E) and late (A) LV filling waves and E wave deceleration time were measured according to standard protocol. E wave propagation rate (EVp) was assessed by color Doppler M-mode across the mitral valve. Tei index was calculated as: (A wave to E wave time - ejection time)/ejection time. Changes at LDD were calculated as: 100 x (value at LDD - value at baseline)/baseline.

RESULTS

The study group comprised 66 patients, mean age 61 +/- 10 years, 80% men. Worse LV systolic function was associated with more severely impaired LV diastolic function both at baseline and at LDD. However, percent change of WMSI and change in EF did not correlate with percent change of EVp and E/E wave propagation rate, but with percent change of Tei index. At LDD, patients with myocardial viability did not show greater percent change of LV diastolic function parameters but significantly lower Tei index.

CONCLUSIONS

In patients with suspected or known coronary artery disease, assessment of diastolic function reserve by LDD stress echocardiography using traditional and color M-mode Doppler may add quantitative information on myocardial function beyond traditional assessment of contractility reserve by WMSI or EF.

Changes in the Doppler myocardial performance index during dobutamine echocardiography: association with neurohormonal activation and prognosis after acute myocardial infarction

OBJECTIVES

To test whether an increase in Doppler myocardial performance index (MPI) during dobutamine stress echocardiography, reflecting deterioration of overall left ventricular function, is associated with increased N-terminal pro-brain natriuretic peptide (NT-pro-BNP) concentration and provides prognostic information beyond conventional systolic wall motion analysis after acute myocardial infarction (AMI).

DESIGN

Prospective, observational study.

METHODS

Dobutamine-atropine stress echocardiography (DASE) and NT-pro-BNP were assessed five days after AMI in 109 consecutive patients. MPI was measured at rest and at low-dose (10 microg/kg/min) and peak dobutamine infusion (<or= 40 microg/kg/min with or without atropine).

MAIN OUTCOME MEASURES

End point was a composite of cardiac death or readmission for heart failure or reinfarction.

RESULTS

In 35 patients (32%), MPI increased at low-dose DASE. This was associated with higher NT-pro-BNP concentrations (beta = 0.30, p = 0.004). During a mean follow up of 27 (SD 7) months, 8 patients died of cardiac causes and 15 patients were readmitted for heart failure or reinfarction. On Cox regression analysis, an increase in MPI at low-dose DASE (p = 0.02) was an independent predictor of cardiac events. In contrast, traditional wall motion analysis during DASE provided no additional prognostic information.

CONCLUSIONS

An increase in MPI at low-dose DASE, reflecting early deterioration of overall left ventricular function, is associated with raised NT-pro-BNP concentration and provides prognostic information beyond conventional stress echocardiographic data after AMI.

The Doppler myocardial performance index during low-dose dobutamine echocardiography predicts mortality and left ventricular dilation after a first acute myocardial infarction

BACKGROUND

Myocardial viability can be detected by wall motion analysis during low-dose dobutamine echocardiography (LDDE) after acute myocardial infarction (AMI). However, wall motion analysis describes only left ventricular (LV) systolic reserve. The Doppler myocardial performance index (MPI) is a quantitative measure of combined LV systolic and diastolic function. We hypothesized that an increase (deterioration) in MPI during LDDE, reflecting reduced systolic and diastolic LV reserve, could provide prognostic information beyond conventional systolic wall motion analysis on mortality, morbidity, and LV remodeling after AMI.

METHODS

Low-dose dobutamine echocardiography (10 microg/kg per minute) was performed within 24 hours and echocardiography was repeated 5 days and 1, 3, and 6 months after a first AMI in 162 consecutive patients. Patients were followed for 25 +/- 11 months. End points were all-cause mortality and cardiac events (cardiac death or readmission for heart failure or reinfarction).

RESULTS

In 72 (44%) patients, MPI increased during LDDE. This was independently associated with subsequent LV dilation at 6 months of follow-up (beta = .73, P < .0001). An increase in MPI during LDDE was a powerful prognostic indicator and remained a predictor of mortality (HR 1.92, 95% CI 1.36-2.71, P < .0001) and cardiac events (HR 2.45, 95% CI 1.83-3.27, P < .0001) after adjustment for clinical data, indices of LV function at rest, and wall motion analysis during LDDE.

CONCLUSIONS

Early after AMI, deterioration in MPI during LDDE predicts subsequent LV dilation and provides prognostic information incremental to clinical data, indices of LV function at rest, and conventional stress echocardiographic data.