Abstract 2240: How Does Load Affect Diastolic Mitral Annular (E’) Velocity in Humans?
Background: Increased afterload prolongs relaxation in invasive studies, but the effects of altered load and loading sequence on commonly-measured indexes of diastolic function, such early diastolic mitral annular velocity (E’), remains unresolved.
Methods: 48 healthy volunteers (age 19 – 84, 48% female, 54% hypertensive) underwent comprehensive echo-Doppler and 2-D tissue Doppler exam with noninvasive BP measurement and carotid tonometry at rest, during sympathetic stimulation (isometric handgrip, HG; cold pressor test, CPT), and with pharmacologic preload reduction (sublingual nitroglycerin, GTN).
Results: At rest, there was an inverse relationship between E’ and afterload, whether measured as mean resistance (SVRI, r=0.44, p=0.003), effective arterial elastance (Ea, r=0.44, p=0.003), characteristic impedance (Z0, r=0.47, p=0.001), or by the amplitude of late-systolic reflected waves (augmentation index, AI, r=0.64, p<0.00001). The E/E’ ratio, an estimate of LV filling pressures, also varied inversely with afterload (Ea, r=0.52, p=0.0004; Z0, r=0.53, p=0.0002; AI, r=0.57, p<0.0001). These relationships were maintained in the pooled data from all states (p<0.001 for all), and a direct relationship was found between E’ and preload (EDVI, r=0.3, p=0.0002). HG and CPT increased BP, preload volume and afterload (p≤0.0001, Table⇓), with no net change in E’ or E/E’ ratio. Conversely, BP and AI dropped with GTN, in concert with a decrease in EDV and thus cardiac output, with no net effect on SVRI or Ea, and this was associated with a drop in E’ velocity (p<0.00001). The E’ response to load was not influenced by age or history of hypertension.
Conclusions: Early diastolic mitral annular velocity (E’) is diminished with increasing afterload, but varies directly with preload volume. Acute, balanced increases in afterload and preload (as with CPT and HG) are thus associated with neutral effects on E’, whereas isolated preload reduction (GTN) reduces E’.