MECHANISM OF ALTERED PATTERNS OF LEFT-VENTRICULAR FILLING DURING THE DEVELOPMENT OF CONGESTIVE-HEART-FAILURE

Background The mechanism of the alterations in the pattern of left ven tricular (LV) filling during the development of congestive heart failu re (CHF) is not fully understood. Methods and Results We studied six c onscious dogs instrumented to measure LV and left atrial (LA) pressure s and LV volume as CHF was induced by rapid pacing. Diastolic filling dynamics were serially measured over 4 weeks during normal sinus rhyth m. Four days after we initiated pacing, the peak early diastolic filli ng rate decreased from 108+/-24 to 88+/-27 mL/s (P<.05) as the maximal early diastolic LA-LV pressure gradient decreased associated with a s lowing of the rate of LV relaxation. Subsequently, the peak early fill ing rate progressively increased, returning to control at 1 week, and by the fourth week, it had increased to 168+/-39 mL/s (P<.05). These c hanges in early filling rates occurred as the maximal early diastolic LA-LV pressure gradient increased in association with a progressive in crease in LA pressure despite further progressive slowing of the rate of LV relaxation. Throughout the development of CHF, peak early fillin g rate and the maximal LA-LV pressure gradient correlated (r=.99, P<.0 01). The early filling deceleration rate increased and deceleration ti me progressively decreased over the 4 weeks as LV stiffness and net LA plus LV stiffness increased (P<.05). As predicted by a theoretical an alysis, the deceleration time was linearly related to the reciprocal o f the square root of LV stiffness (r=.94, P<.01). Conclusions Early in CHF, slowing of LV relaxation reduces the maximal early diastolic LA- LV pressure gradient, decreasing the peak early filling rate. As CHF p rogresses, this is overcome by an increase in LA pressure that augment s the early diastolic LA-LV pressure gradient, increasing peak early f illing rate. Increasing LV stiffness during the development of CHF pro gressively shortens the early filling deceleration time and augments t he early filling deceleration rate. These observations suggest that th e early filling deceleration time reflects LV stiffness.