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Progressive right ventricular failure is not explained by myocardial ischemia in a pig model of right ventricular pressure overload

^a Department of Thoracic-, Cardiac- and Vascular Surgery, Universitätsmedizin Goettingen, Georg-August-Universität Goettingen, Germany
^b Department of Cardiology, University of Graz, Austria

Received 5 March 2008; received in revised form 1 September 2008; accepted 8 September 2008.

^_* Corresponding author. Address: Department of Thoracic-, Cardiac- and Vascular Surgery, University Hospital of Goettingen, Robert-Koch Straße 40, 37099 Goettingen, Germany. Tel.: +49 551 39 6001; fax: +49 551 39 6002. (Email: schmitto{at}med.uni-goettingen.de).

Background: Current concepts of acute pulmonary embolism suggest that right ventricular (RV) dilatation and failure are the consequence of pressure overload-induced RV hypoperfusion and ischemia. Methods: Sixteen human-sized hybrid pigs were instrumented for the measurement of RV and aortic pressure, aortic and right coronary artery blood flow (RCA BF), RV oxygen consumption (RV MVO₂) and RV free wall segment length. The pulmonary artery was constricted (PAC) to increase RV peak pressure acutely 2.5-fold (from 27 ± 2 to 64 ± 3 mmHg, n = 9), and the constriction was maintained for 6 h. Results: At 10 min after PAC, a RV work index (RVWI, RV pressure-segment length loops) was increased 2.3-fold, indicating an initial RV adaptation to increased afterload. At 1 h, 3 h and 6 h after PAC, however, RVWI decreased progressively towards control levels, while RCA BF and RV MVO₂ continued to increase. The arterial-coronary venous pH difference did not increase throughout the protocol. Arterial troponin T concentration increased from 0.08 ± 0.03 to 0.80 ± 0.20 ng/ml at 6 h after PAC. None of the parameters changed in control animals (n = 7). Conclusion: We conclude that in our model RV failure during PAC develops in spite of increased coronary blood flow and MVO₂. Thus, mechanisms different from ischemia may contribute to progressive RV failure after pulmonary embolism.

Abbreviations: AOP_mean = mean aortic pressure • BG = banding group • CG = control group • CVP = central venous pressure • HR = heart rate • LV = left ventricle • n.a. = not assessed • PAC = constricted pulmonary artery • pH art = arterial pH • pH ven = RV coronary venous pH • RCA BF = right coronary artery blood flow • RV = right ventricle • RV dP/dt _max = maximum first derivative of RV pressure • RV dP/dt _min = minimum first derivative of RV pressure • RV edP = end-diastolic RV pressure • RV MVO₂ = right ventricular oxygen consumption • RV pP = RV peak pressure • RVWI = RV work index • SLed = end-diastolic RV segment length • SLes = end-systolic RV segment length • SL = percent segment shortening • Trop T = serum troponin T concentration

Key Words: Right ventricular function • Pressure overload • Ischemia • Pulmonary embolism