Abstract 3071: Relationship Between Ventricular Afterload and Early Diastolic Ventricular Relaxation: The Asklepios Study
Background: Experimental studies demonstrated a high dependency of myocardial and ventricular relaxation on afterload. Ventricular afterload (arterial load) is time-varying, complex, and not fully described by any single parameter.
Methods: We studied central pressure-flow relations in a population-based sample of 2365 adults enrolled in the Asklepios study using carotid applanation tonometry and Doppler echocardiography. We used multiple regression to determine the independent contribution of various components of arterial load on ventricular relaxation (annular early diastolic velocity, Em) and the mitral inflow/mitral annular early diastolic peak velocity ratio (E/Em), a correlate of left atrial pressure. Left ventricular mass (LVM) and indices of arterial load were indexed for body surface area using appropriate allometric powers.
Results: Age was the strongest predictor of Em, whereas LVM was the strongest predictor of E/Em. After adjustment for age, gender, LVM and relative wall thickness, lower total arterial compliance (TAC; Standardized β= 0.16; P<0.0001) and increasing systemic vascular resistance (SVR; Std β=−0.14; P<0.0001) were independent predictors of lower Em. Furthermore, after adjustment for TAC and SVR, an earlier arrival of the reflected wave, a determinant of mid-to-late systolic pulsatile load (Std β=0.07; P<0.0001) independently predicted a lower Em. In contrast, for all other components of afterload held constant, a higher aortic characteristic impedance, a determinant of very early systolic pulsatile load (Std β=0.16; P<0.0001) predicted a higher Em. Independent predictors of a higher E/Em ratio were very similar to independent predictors of a lower Em. In contrast to the timing of wave reflections, reflection magnitude did not predict Em or E/Em.
Conclusions: Arterial load is an independent determinant of early relaxation, independently of age, gender and ventricular geometry. The pulsatile loading sequence, in addition to absolute load, is an independent determinant of ventricular relaxation, with worsening relaxation seen with earlier wave reflections. Our findings indicate that wave reflection timing is more important than reflection magnitude as a determinant of ventricular relaxation.