Importance of Relative Pulmonary Hypertension in Cardiac Surgery: The Mean Systemic-to-Pulmonary Artery Pressure Ratio

Objective: To determine the importance of the mean arterial pressure-to-mean pulmonary artery pressure ratio (MAP/MPAP) in cardiac surgical patients.Design: Retrospective and prospective studies (3 groups).Setting: Tertiary care hospital.Participants: Cardiac surgical patients (1,557).Intervention: Retrospective analysis (group 1), induction of general anesthesia (group 2), and transesophageal Doppler echocardiography (group 3).Measurements and Main Results: In group 1 (n = 1,439), demographic, hemodynamic, and other perioperative variables were collected with follow-up until hospital discharge. The primary outcome was a composite index of hemodynamic complications that included death, resuscitated cardiac arrest, use of vasopressive drugs for >24 hours postoperatively, or the use of an intra-aortic balloon pump that was not present preoperatively. In group 2 (n = 34), the effect of general anesthesia on the MAP/MPAP ratio was studied, and Doppler echocardiography was used to evaluate diastolic profiles in group 3 (n = 74). In group 1, a total of 302 patients experienced hemodynamic complications (21%). The MAP/MPAP ratio was significantly lower in the patients who developed complications (3.3 ± 1.3 v 4.0 ± 1.4, p < 0.0001). Multiple stepwise logistic regression analysis showed the MAP/MPAP ratio to be an independent predictor of hemodynamic complications (p < 0.0001). In group 2, the induction of anesthesia decreased both MAP and MPAP, but the ratio remain unchanged (p = 0.242). In group 3, patients with moderate-to-severe diastolic dysfunction (DD) had a lower ratio (3.5 ± 0.9 v 4.0 ± 1.1 compared with those with normal-to-mild DD, p = 0.07).Conclusion: The MAP/MPAP ratio is a useful hemodynamic variable in cardiac surgery. It can be used to predict hemodynamic complications after cardiac surgery, is not influenced by the induction of anesthesia, and tends to correlate with the severity of left ventricular diastolic profiles.