Preload reduction in HCM patients caused a marked downward shift in diastolic pressure-volume relations with a net pressure decline of -10+/-4 mm Hg, compared to -2+/-2 mm Hg in other groups (P<.001).
Observational (n=42)
Does the dynamic diastolic pressure-volume relation differ from the passive end-diastolic pressure-volume relation in patients with idiopathic hypertrophic cardiomyopathy compared to other cardiac conditions?
Elevated LV filling pressures in HCM are uniquely characterized by a large disparity between flat pressure-volume relations during filling and steep end-diastolic relations, indicating offset pressures that vary with chamber loading rather than just a stiff cavity.
Absolute Event Rate: -10% vs -2%
p-value: p=<.001
BACKGROUND: Dynamic diastolic pressure-volume curves measured during filling (PVR fill) in patients with idiopathic hypertrophic cardiomyopathy (HCM) are often considerably shallower than would be anticipated if one assumed high chamber stiffness. We hypothesized that these curves deviate markedly from the passive end-diastolic pressure-volume relation (EDPVR) and explored the mechanisms for such a discordance. METHODS AND RESULTS: We used invasive pressure-volume analysis and conductance catheter methodology to study 42 patients. Nine had HCM, and the remaining patients comprised three comparison groups: 11 with normal left ventricular (LV) function, 13 with LV hypertrophy secondary to chronic hypertension (LVH-HTN), and 9 with idiopathic dilated cardiomyopathy (DCM). EDPVRs were recorded during balloon catheter obstruction of inferior vena cava inflow. In normal subjects, LVH-HTN patients, and DCM patients, PVR fill curves deviated only slightly from the passive EDPVR. In striking contrast, HCM patients displayed a flat PVR fill that was very different from the steep EDPVR. On reduction of preload, PVR fill relations in HCM shifted downward in parallel, with a net pressure decline at the same chamber volume of -10+/-4 mm Hg. This staircaselike shift was much less in the other patient groups (-2+/-2 mm Hg; P<.001). The unusual behavior in HCM could not be attributed directly to increased viscosity, enhanced pericardial constraint, or preload dependence of isovolumic relaxation. Regional heterogeneity of relaxation may play a role; however, we speculate that the major mechanism relates to the unique fiber and chamber architecture seen with HCM and possibly to enhanced ventricular interaction. CONCLUSIONS: Elevated LV filling pressures in HCM are not due simply to a stiff cavity but also reflect a major influence of offset pressures that vary with chamber loading. The large disparity between flat pressure-volume relations during filling and steep end-diastolic relations appears unique to HCM. This indicates that caution should be used in the interpretation of stiffness results derived from steady-state data and suggests that therapies that alter cavity geometry and/or reduce interaction may markedly influence LV diastolic pressures in HCM.
Pak et al. (1996) conducted an observational in Idiopathic Hypertrophic Cardiomyopathy (n=42). Preload reduction via inferior vena cava balloon occlusion vs. Normal LV function, LVH-HTN, and DCM patients was evaluated on Net pressure decline at the same chamber volume on reduction of preload (p=<.001). Preload reduction in HCM patients caused a marked downward shift in diastolic pressure-volume relations with a net pressure decline of -10+/-4 mm Hg, compared to -2+/-2 mm Hg in other groups (P<.001).