Figure 11

The Suga (SP/ESV) index instead of end-systolic elastance for FFR measurement. Since End-systolic elastance (Ees), expressing the slope of the in-vivo, end-systolic ventricular pressure vs. chamber volume relation, is the most "foolproof' window into in vivo myocardial contractility, Ees should be measured at each heart rate step increase. A simpler approach was utilized by Feldman and co-workers by measuring SP/ESV ratio at baseline, and for pacing induced heart rate increase to 25 and 50 bpm beyond basal heart rate. Feldman showed that 7 patients with dilated cardiomyopathy (DCM) demonstrated little or no significant enhancement in SP/ESV ratio during atrial pacing tachycardia. The lack of improvement in cardiomyopathy patients has been contrasted to patients with normal ventricular function (Control) who demonstrated significant increase in SP/ESV ratio. SP/ESV ratio is simpler than Ees measurement, and equally provides knowledge of up-sloping vs flat-biphasic force-frequency relationship. (Modified from: Feldman MD, Alderman JD, Aroesty JM, Royal HD, Ferguson JJ, Owen RM, et al. Depression of systolic and diastolic myocardial reserve during atrial pacing tachycardia in patients with dilated cardiomyopathy. J Clin Invest 1988; 11:1661–9)