Purpose Index of myocardial performance (IMP) is a systolic-diastolic derived index used to evaluate cardiac function and is a prognostic indicator in patients with myocardial infarction and dilated cardiomyopathy. In an experimental canine model with normal and reduced LV function, volume loading affects (reduces) the IMP by prolonging the left ventricular ejection time (ET). Our objective in this study was to examine IMP in patients with a volume overloaded left ventricle with normal and reduced LV function.
Methods The study groups consisted of 157 subjects: 41 normals, 61 with congestive heart failure (CHF) (ejection fraction: 30-50%), and 55 with aortic regurgitation (AR). Of those patients with AR, 13 had CHF. 2D Doppler echocardiography, transmitral, and transaortic spectral Doppler was used to obtain LV size and function.
Results When compared to normal subjects (0.37 ± 0.18), IMP was increased in CHF (0.46 ± 0.13, p < .01) and was not significantly decreased in AR (0.33 ± 0.15). ET (319 ± 37) was decreased in CHF (284 ± 52, p < .001) and increased in AR (345 ± 49, p < .01). Ejection fraction (EF) was similar in normals (63 ± 7) and in AR (63 ± 8). Deceleration time (DCT) was increased in AR (285 ± 71) compared to the normals (205 ± 38, p < .001). However, EF was higher in AR + CHF (45 ± 5) than in CHF (30 ± 11, p < .001). IMP was lower in AR + CHF (0.29 + 0.16, p < .001) as compared to CHF due to a prolonged ET (348 ± 49, p < .001) and a reduced ISovolumetric contraction time (ICT) (50 ± 33 vs. 71 ± 25 msec, p < .05). DCT increased in AR + CHF (262 ± 49) compared to CHF (163 ± 62, p < .001). Using forward stepwise linear regression, IMP could be predicted from the posterior wall thickness in normals (r = .490, p < .001). In CHF, IMP could be predicted (r = .5315, p < .001) from peak rapid filling velocity (p = .0179) and EF (p = .0226). In AR, IMP could be predicted (r = .515, p < .001) from DCT (p < .0001) and the end diastolic dimension (p = .007) but not the EF.
Conclusions ET is prolonged in AR, a volume overloaded state. Consequently, IMP was insignificantly shortened as compared to normals despite a markedly abnormal DCT suggesting diastolic dysfunction. With CHF, IMP may be falsely low due to a prolonged ET and shortened ICT. IMP should be carefully used as a prognostic indicator. Its application should be cautiously used in states that affect the components of IMP.
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