Effect of pericardiotomy on exercise-induced pulmonary hypertension in the horse
Authors: Textor JA, Ducharme NG, Gleed RD, Hackett RP, Erb HN, Mitchell L, Soderholm LV
Journal: Equine and Comparative Exercise Physiology
Summary
# Editorial Summary Researchers investigating whether removing or opening the pericardium (the fibrous sac surrounding the heart) could reduce exercise-induced pulmonary hypertension hypothesised that relieving pericardial constraint would improve diastolic function and lower pulmonary vascular pressures during maximal work. Five horses underwent pericardiotomy and were exercised to maximum capacity before surgery and again at one and thirteen weeks post-operatively, with continuous monitoring of pulmonary arterial pressure, right ventricular pressures, heart rate and derived measures of ventricular relaxation; an unoperated control group of five horses performed identical exercise protocols for comparison. Contrary to expectations, pericardiotomy produced no significant changes in any measured parameter—pulmonary arterial pressure, pulmonary capillary wedge pressure, ventricular relaxation indices (−dP/dtmax, t₁/₂, τ) or heart rate—either at rest or during maximal exercise, with results remaining consistent between the surgical and control groups throughout the thirteen-week study period. For equine practitioners and researchers, this finding suggests that the pericardium does not substantially constrain cardiac function during exercise in normal horses, and that reduced pericardial pressure is unlikely to be a therapeutic target for exercise-induced pulmonary hypertension; furthermore, it validates the use of pericardiotomy in experimental protocols where cardiac monitoring is required, confirming that the surgical intervention itself does not confound cardiopulmonary measurements.
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Practical Takeaways
- •Pericardial constraint is not a primary mechanism driving exercise-induced pulmonary hypertension in horses; other factors should be investigated
- •If open pericardial access is required in equine surgery, measured cardiopulmonary function will not be compromised by the pericardiotomy itself
- •Exercise-induced pulmonary hemorrhage and hypertension likely involve factors beyond cardiac diastolic dysfunction and pericardial pressure
Key Findings
- •Pericardiotomy did not significantly alter pulmonary arterial pressure, pulmonary artery wedge pressure, or right ventricular pressure at rest or maximal exercise over 13 weeks
- •No significant differences were found in ventricular relaxation parameters (−dP/dtmax, t1/2, τ) between pre- and post-pericardiotomy measurements
- •Experimental group (n=5) showed no differences compared to unoperated control group (n=5) across all cardiopulmonary variables measured
- •Results indicate that reduced pericardial pressure does not affect measured cardiopulmonary parameters in normal horses during exercise