Assessing left ventricular systolic dysfunction after myocardial infarction: are ejection fraction and dP/dt(max) complementary or redundant?

Abstract

Among the various cardiac contractility parameters, left ventricular (LV) ejection fraction (EF) and maximum dP/dt (dP/dt(max)) are the simplest and most used. However, these parameters are often reported together, and it is not clear if they are complementary or redundant. We sought to compare the discriminative value of EF and dP/dt(max) in assessing systolic dysfunction after myocardial infarction (MI) in swine. A total of 220 measurements were obtained. All measurements included LV volumes and EF analysis by left ventriculography, invasive ventricular pressure tracings, and echocardiography. Baseline measurements were performed in 132 pigs, and 88 measurements were obtained at different time points after MI creation. Receiver operator characteristic (ROC) curves to distinguish the presence or absence of an MI revealed a good predictive value for EF [area under the curve (AUC): 0.998] but not by dP/dt(max) (AUC: 0.69, P < 0.001 vs. EF). Dividing dP/dt(max) by LV end-diastolic pressure and heart rate (HR) significantly increased the AUC to 0.87 (P < 0.001 vs. dP/dt(max) and P < 0.001 vs. EF). In naïve pigs, the coefficient of variation of dP/dt(max) was twice than that of EF (22.5% vs. 9.5%, respectively). Furthermore, in n = 19 pigs, dP/dt(max) increased after MI. However, echocardiographic strain analysis of 23 pigs with EF ranging only from 36% to 40% after MI revealed significant correlations between dP/dt(max) and strain parameters in the noninfarcted area (circumferential strain: r = 0.42, P = 0.05; radial strain: r = 0.71, P < 0.001). In conclusion, EF is a more accurate measure of systolic dysfunction than dP/dt(max) in a swine model of MI. Despite the variability of dP/dt(max) both in naïve pigs and after MI, it may sensitively reflect the small changes of myocardial contractility.

Fig. 1.

Receover operator characteristic (ROC) curves of various parameters to predict myocardial infarction (MI), with areas under the curves (AUCs). A: ejection fraction (EF) and maximum dP/dt (dP/dt_max). B: left ventricular (LV) volumes adjusted with body surface area. While EF, the end-systolic volume index (ESVI), and the end-diastolic volume index (EDVI) were excellent predictors, dP/dt_max and the stroke volume index (SVI) were less useful to predict MI.

Fig. 2.

ROC curves, including AUCs, for dP/dt_max and its adjusted values to predict MI. Adjustment of dP/dt_max with end-diastolic pressure (EDP) significantly improved the predictive accuracy. Further adjustment with heart rate (HR) showed an additional increase in AUC.

Fig. 3.

A: correlation between EF and dP/dt_max. B: correlation between EF and (dP/dt_max)/EDP/HR. Division of dP/dt_max by EDP and HR improved the correlation to EF.

Fig. 4.

Comparative variability of EF and dP/dt_max in naïve pigs (n = 132). Values are means ± SD. The coefficient of variation of EF was 9.4%, and that of dP/dt_max was 22.5%.

Fig. 5.

A: scatterplot of relative changes of EF and dP/dt_max before and after MI. No significant correlation was found between the relative changes of EF and dP/dt_max. Note that while EF decreased after MI in all animals, the relative change of dP/dt_max was not always negative. B: Bland-Altman analysis comparing relative EF change and relative dP/dt_max change after MI. A modest linear correlation was found among the plots, indicating more correlation between EF and dP/dt_max when the relative decrease was large.

Fig. 6.

Scatterplot of dP/dt_max and echocardiographic strain parameters in 23 pigs with similar EFs after MI. Whereas circumferential strain showed weak correlation with dP/dt_max, radial strain showed a moderate correlation with dP/dt_max.