Abstract 772: Restrictive Left Ventricular Filling Pattern Does Not Result from Increased Left Atrial Pressure Alone
Background. The restrictive filling pattern seen with severe heart failure (HF) has been attributed to increased left atrial (LA) pressure (P). In contrast, we hypothesized that the restrictive filling pattern results from abnormal left ventricular (LV) diastolic function and is different from the filling pattern in normals with similar increased LAP due to acute volume loading.
Methods. We studied 8 conscious chronically-instrumented dogs. Under normal conditions, mean LAP increased from 8.1±3.7 mmHg to 24.7±6.4 mmHg following rapid intravenous infusion of 500 ml of dextran after autonomic blockade. HF was then induced by 4 weeks of rapid pacing. After HF, LAP increased to 24.5±4.6 mmHg. Heart rate was similar in those two settings (124±17 bpm in normal volume loading and 124±19 bpm in HF). Peak early filling rates (E) and early diastolic mitral annular velocity (EM) were calculated by differentiation of LV volume and LV long axis dimension, respectively. To compare relaxation and diastolic properties between those two settings, the time constant of LV relaxation (τ) and the effective LV chamber stiffness (KLV) were calculated.
Results. Compared to normal volume loading, during HF, E was significantly (p < 0.05) lower (140±30 vs 190±43 ml/s); the E deceleration time was shorter (47.5±7.8 vs 66.5±8.5 ms); and EM was reduced (28.9±9.0 vs 48.4±14.4 mm/s). Peak EM was delayed relative to E after HF (14.6±6.7 ms), but not with normal volume loading (−7.1±9.4 ms, p<0.05). Compared to normal volume loading, τ (41.0±9.4 vs 32.1±2.4 ms) and KLV (2.5±0.98 vs 1.6±0.63 mmHg/ml) were also significantly increased with HF.
Conclusion. Even with similarly elevated LAP, LV filling dynamics with severe HF differ from acute volume loading of a normal in that restricted filling has a smaller E, a shorter E deceleration time, and reduced and delayed EM, reflecting slow relaxation and increased LV chamber stiffness. Thus, the restrictive filling pattern does not result merely from increased LAP, but is related to diastolic dysfunction.