Instantaneous Right Ventricular to Pulmonary Artery Systolic Pressure Difference in Cardiac Surgery: A Retrospective and Prospective Cohort Study.

ABSTRACT

BACKGROUND: During cardiac surgery, right ventricular outflow tract obstruction (RVOTO) is defined as an instantaneous pressure difference ≥6 mmHg between right ventricular systolic pressure (RVSP) and pulmonary artery systolic pressure (PASP), for ≥5 minutes. Risk factors for RVOTO remain poorly understood. This cohort study is designed to evaluate the incidence, characteristics and outcomes of the patients who experienced RVOTO. METHODS: Instantaneous pressure difference between RVSP and PASP was measured using a pulmonary artery catheter with a right ventricular port during cardiac surgery from a retrospective (n=295) and a prospective (n=105) cohort. RESULTS: From the retrospective and prospective cohort, incidence of RVOTO was 30.2 and 36.2% before cardiopulmonary bypass (CPB) initiation and 43.7 and 47.6% after CPB separation. Before CPB initiation, patients with RVOTO had higher cardiac output (4.2±1.5 vs 3.8±1.1L⋅min-1, P=0.033), received more inhaled epoprostenol (79 vs 61%, P=0.005) and inotropes (66 vs 51%, P=0.016) compared to those without RVOTO. After CPB separation, patients with RVOTO had higher heart rate (62±15 vs 58±13 beats⋅min-1, P=0.011), cardiac output (4.1±1.4 vs 3.7±1.1L⋅min-1, P=0.003), CPB duration (90±45 vs 77±30mins, P=0.014), lower fluid balance (758±1123 vs 1063±1089mL, P=0.021) and were more exposed to intratracheal milrinone (12 vs 4%, P=0.015) compared to those without RVOTO. The time with persistent organ dysfunction (TPOD) at 28 days after surgery was similar among patients who had a RVOTO event, before CPB initiation or after CPB separation, compared to those who did not. CONCLUSION: RVOTO is common in cardiac surgery. However, it is not associated with longer TPOD.