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

The Role of Exercise Stress Echocardiography for Determination of Subclinical Cardiac Involvement in β-Thalassemia Major

β-Thalassemia major (β-TM) patients are at increased risk for cardiovascular diseases. Determination of subclinical cardiac involvement is essential for preventive measures. Thus, we aimed to evaluate the role of stress echocardiography for identification of subclinical cardiac dysfunction in β-TM patients. In this prospective study, 45 β-TM patients who were referred for cardiac evaluation, were enrolled. Exclusion criteria included non sinus rhythm and overt cardiac disease. Stress echocardiography levels and cardiac magnetic resonance imaging (MRI) results were obtained from β-TM patients. Patients were divided into two groups of normal vs. iron overload from cardiac T2* greater or less than 20 msec, respectively. Resting and peak exercise right ventricular stroke volume (RVSV) and left ventricular SV (LVSV) were significantly lower in iron overload vs. normal β-TM patients, respectively (p value <0.05). At peak LV global longitudinal strain (GLS) and myocardial performance index (MPI) were significantly decreased and increased compared with resting in iron overload vs. normal β-TM patients, respectively (p value <0.05). There was a significant relationship between inappropriate hemodynamic response to exercise and lower age (p value = 0.032). Resting LVSV and RVSV seemed better prognosticators for iron overload than LV ejection fraction (LVEF). Decreased GLS and increased MPI at peak exercise could also predict the presence of cardiac iron overload. These measurements by stress echocardiography could be evaluated when cardiac T2* could not be determined.

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.

Increased cardiac adenylyl cyclase expression is associated with increased survival after myocardial infarction

BACKGROUND

Cardiac-directed expression of adenylyl cyclase type VI (AC(VI)) in mice results in structurally normal hearts with normal basal heart rate and function but increased responses to catecholamine stimulation. We tested the hypothesis that increased left ventricular (LV) AC(VI) content would increase mortality after acute myocardial infarction (MI).

METHODS AND RESULTS

Transgenic mice with cardiac-directed AC(VI) expression and their transgene-negative littermates (control) underwent coronary ligation, and survival, infarct size, and LV size and function were assessed 1 to 7 days after MI. Mice with increased AC(VI) expression had increased survival (control 41%, AC(VI) 74%; P = 0.004). Infarct size and myocardial apoptotic rates were similar in AC(VI) and control mice; however, AC(VI) mice had less LV dilation (P < 0.001) and increased ejection fractions (P < 0.03). Three days after MI, studies in isolated perfused hearts showed that basal LV +dP/dt was similar, but graded dobutamine infusion was associated with a more robust LV contractile response in AC(VI) mice (P < 0.05). Increased LV function was associated with increases in cAMP generation (P = 0.0002), phospholamban phosphorylation (P < 0.04), sarcoplasmic reticulum Ca2+-ATPase (SERCA2a) affinity for calcium (P < 0.015), and reduced AV block (P = 0.04).

CONCLUSIONS

In acute MI, increased cardiac AC(VI) content attenuates adverse LV remodeling, preserves LV contractile function, and reduces mortality.