Left ventricular diastolic function during positive end-expiratory pressure: Impact of right ventricular ischemia and ventricular interaction

Abstract

The individual and additive effects of positive end-expiratory pressure (PEEP) and right coronary artery (RCA) occlusion on left ventricular end- diastolic pressure-volume relations (LVEDPVR) were examined in six anesthetized dogs. Right ventricular (RV) and left ventricular (LV) ejection fractions (EF), end-diastolic volume (EDV) and end-systolic volumes (ESV) were measured by thermodilution as PEEP was added before and after RCA occlusion. PEEP alone caused a decline in cardiac output, transmural left atrial pressure (LAP) (6.0 ± 0.6 to 3.2 ± 1.4 mm Hg, p < 0.05), and LVEDV (49 ± 3 to 36 ± 4 ml, p < 0.05). RVEDV, the mean slope (± SD) of the LVEDPVR (0.37 ± 0.16 to 0.30 ± 0.19) and LAP at a common LV volume (35 ml, V35) did not change with PEEP. RCA occlusion caused cardiac output and RVEF (38 ± 5 to 27 ± 5%, p < 0.05) to decline and RVESV (25 ± 4 to 33 ± 6 ml, p < 0.05) to increase. RVEDV, the slope of the LVEDPVR, and LAP at V35 were unchanged from baseline. The addition of PEEP after RCA occlusion caused cardiac output to decline further. However, unlike before occlusion, there was no change in LAP (6.5 ± 1.3 to 5.0 ± 1.4 mm Hg) despite a decline in LVEDV (47 ± 3 to 29 ± 6 ml, p < 0.05). RVESV and RVEDV increased with PEEP after RCA occlusion as did LAP at V35. The slope of the mean LVEDPVR tended to increase (0.98 ± 1.03). Thus, in this model, neither PEEP nor RCA occlusion alone alters the LVEDPVR. The combination of PEEP and RCA occlusion caused a significant alteration in LV diastolic function as assessed by a shift in the LVEDPVR and constant LAP despite a decline in LVEDV. These changes are most likely related to ventricular interaction.