Accuracy of Estimated versus Calculated Mean Pulmonary Arterial Pressure

Abstract

<h3>Purpose</h3> Less than half of heart failure physicians calculate mean pulmonary arterial pressures (mPAP). Rather, they are reported from approximation between the systolic and diastolic pulmonary pressures. Imprecise assessment of mPAP will result in inaccurate calculation of the pulmonary vascular resistance (PVR), which can alter perceived eligibility for heart transplantation (HT). We sought to assess for differences between reported and calculated mPAP and associated PVR. <h3>Methods</h3> We retrospectively analyzed consecutive patients undergoing right heart catheterization with milrinone drug study at our institution (2/2013-11/2019). Hemodynamics were measured at baseline and again after a 50 mcg/kg milrinone load. We retrospectively calculated the mPAP as (2/3)*(diastolic PA) + (1/3)*(systolic PA), as well as the corresponding PVR. We compared the median reported and calculated mPAPs at baseline and following milrinone study. Finally, we assessed the number of patients in which calculation of mPAP reclassified the PVR across the cut-off of 3.5 WU, which is often used to determine eligibility for HT. <h3>Results</h3> A total of 224 patients were included - median age 57 (IQR 48-66) years, 34% women, and 31% ischemic cardiomyopathy. At baseline, median mPAP remained the same when comparing the calculated (40 mmHg, IQR 31-47) versus the reported mPAP (40 mmHg, IQR 32-48), though calculation resulted in significantly less variation in measurements (<i>p<</i>0.001). Calculated PVR, 3.5 WU (IQR 2.3-4.6), was significantly lower than reported PVR, 3.8 WU (IQR 2.5-5.1), <i>p<</i> 0.001. After milrinone study, final calculated mPAP, 33 mmHg (IQR 26-41), again had significantly less variability compared to reported, 33 mmHg (IQR 25-42), <i>p</i><0.001, and subsequent PVR was significantly lower with calculated mPAP, PVR 2.65 WU (IQR 1.88-3.70), compared to reported mPAP, PVR 2.78 WU (IQR 1.93-3.78), <i>p</i><0.001. There were 46 patients (21%) in which the PVR transitioned across the PVR cutoff of 3.5 WU after calculation of mPAP - 40 (18%) had PVR decrease to ≤ 3.5 from > 3.5, and 6 (3%) had PVR increase to > 3.5 from ≤ 3.5. <h3>Conclusion</h3> Calculation of mPAP resulted in less variation in measurement, affecting downstream calculation of PVR. More than one in five patients had PVR values transition across the cut-off of 3.5 WU following calculation of mPAP, which could alter subsequent eligibility for HT.