Left Ventricular Global Function Index and the Impact of its Companion Metric

Figure 1. Scatter plot of data obtained by CMRI in 96 cardiac patients, showing SV (multiplied by 100 for scaling purposes) vs. the denominator in equation (1). Regression line (blue) and equation are included. The slope of the red broken line corresponds with the ratio formulated in equation (1), for the case that the ratio LVGFI is 30%. All (yellow marked) points on or very close to this line share the same value of the ratio, illustrating that the ratio itself is not unique. Further characterization of individual points requires specification of the corresponding hypotenuse (such as the length of the green line with arrow head for the lower-left point).

Figure 2. Scatter plot for dimensionless LVGFI vs. its companion metric LVGFIC (mL). The green rectangular area illustrates that e.g., for the narrow range 20<LVGFI<25 % this metric is not unique, as for the interval the individual data points are rather characterized by the prevailing LVGFIC (mL), with values between 193 and 384 mL. Correlations are not significant for the diagnostic subgroups, with the exception of acute myocardial infarction (MI), where R = −0.46 for N = 69.

Figure 3. Scatter plot of LVGFI (%) vs. GLS (%). Overall correlation R = −0.51 (P < 0.0001), but after stratification for diagnostic group only a significant correlation (R = −0.81, P = 0.005) results for the takotsubo group (N = 11) and R = −0.45 (P < 0.001) for acute MI (N = 69). For acute myocarditis (N = 16) R = −0.23 (ns).

Figure 4. Scatter plot of EF (%) vs. LVGFI (%), yielding R = 0.86. The high correlation clearly demonstrates that the new metric LVGFI and the traditional EF are more or less equivalent, mainly due to the fact that they share the same components in their mathematical definitions.

Figure 5. Scatter plot of VAC vs. LVGFI (%), yielding R = 0.87. The high correlation clearly demonstrates that the new metric LVGFI and the traditional VAC (assuming the intercept Vo of the systolic elastance vanishes) are more or less equivalent, mainly due to the fact that they share the same components in their mathematical definitions.

Figure 6. Scatter plot of ejection fraction (EF, %) vs. average volume i.e., (ESV+EDV)/2 shows that a major component of the definition formula for LVGFI is actually highly correlated (R = −0.66) with EF.

Figure 7. Simulation of LVGFI vs. LV mass (expressed as mL after inclusion of myocardial density), using average values for SV and (EDV+ESV)/2 as obtained in our patients (Table 1), stratified for sex.

Figure 8. Average values found for LVGFI on the basis of actual patient data for SV, ESV and EDV, but with fixed values for LV mass assumed for all patients (N = 96), and set at 100, 120, 140, 160, and 180 grams. This theoretical curve shows a monotonous decline as LV mass increases.

Figure 9. (A,B) Histograms for LVGFI and LVGFIC, respectively. Compare with Figure 1 in Nwabuo et al. (2).

Figure 10. Scatter plot of stroke volume (SV) vs. LVmass. The slope of any line refers to myocardial contraction fraction (MCF), with data points stratified for men and women, as exemplified by the yellow line referring to the case of MCF = 50%. Average MCF in women is not different compared to men, despite their smaller (P < 0.0001) LVmass (see yellow marked area).