Effect of pericardiotomy on exercise-induced pulmonary hypertension in the horse

Abstract

AbstractThe role of cardiac function or dysfunction in the pathogenesis of exercise-induced pulmonary hypertension and haemorrhage in horses has been minimally investigated. We hypothesize that pericardiotomy would enhance diastolic function and attenuate pulmonary vascular pressures in maximally exercising horses. Our objective was to evaluate diastolic function and cardiopulmonary pressures before and after pericardiotomy, at rest and at maximal exercise. Study design was both self- and externally controlled. Five horses underwent pericardiotomy after a baseline exercise test. They subsequently performed the same exercise protocol at 1 week and 13 weeks post-operatively. An external, unoperated control group of five horses performed the same experimental protocol. Pulmonary arterial pressure (PAP), pulmonary artery wedge pressure (PWP), right ventricular pressure, heart rate (HR) and oesophageal pressure were measured continuously at rest and at maximal exercise; maximum rates of ventricular pressure decrease (−dP/dtmax), relaxation half-time (t1/2), time constant of isovolumic relaxation (τ) and pulmonary capillary pressures (PcapP) were derived. Statistical analysis was performed using two-tailed Wilcoxon's signed-rank and rank-sum tests, with significance set at P<0.05. No significant differences were found in any variable after pericardiotomy was performed or between the experimental and external control groups. We conclude that during a 13-week study period, pericardiotomy does not alter pulmonary or ventricular pressures or rate of ventricular relaxation in the resting or maximally exercising horse. Results indicate that, in past and future studies requiring an open pericardium in normal horses, the cardiopulmonary parameters measured here are not affected by reduced pericardial pressure.