Current practice for determining pulmonary capillary wedge pressure predisposes to serious errors in the classification of patients with pulmonary hypertension

Background Accurate measurement of left ventricular filling pressure is important to distinguish between category 1 pulmonary arterial hypertension (PAH) and category 2 pulmonary hypertension (PH) from left heart diseases (PH-HFpEF). We hypothesized that the common practice of relying on the digitized mean pulmonary capillary wedge pressure (PCWP-digital) results in erroneous recordings, whereas end-expiratory PCWP measurements (PCWP-end Exp) provide a reliable surrogate measurement for end-expiratory left ventricular end-diastolic pressure (LVEDP-end Exp-end Exp). Methods We prospectively performed left and right cardiac catheterization on 61 patients referred for evaluation of PH and compared the LVEDP-end Exp to end-expiration to the (a) PCWP-end Exp and (b) PCWP-digital. Results The PCWP-end Exp was a more reliable reflection of LVEDP-end Exp (mean 13.2 mm Hg vs 12.4 mm Hg; P, nonsignificant) than PCWP-digital (mean 8.0 mm Hg vs 12.4 mm Hg, P < .05). Bland-Altman analysis of PCWP-digital and LVEDP-end Exp revealed a mean bias of -4.4 mm Hg with 95% limits of agreement of -11.3 to 2.5 mm Hg. Bland-Altman analysis of PCWP-end Exp and LVEDP-end Exp revealed a mean bias of 0.9 mm Hg with 95% limits of agreement of -5.2 to 6.9 mm Hg. If PCWP-digital were used to define LVEDP-end Exp, 14 (27%) of 52 patients would have been misclassified as having PAH rather than PH-HFpEF. Patients with obesity and hypoxia were particularly more likely to be misclassified as PAH instead of PH-HFpEF if PCWP-digital was used to define LVEDP-end Exp (odds ratio 8.1, 95% CI 1.644-40.04, P = .01). Conclusions The common practice of using PCWP-digital instead of PCWP-end Exp results in a significant underestimation of LVEDP-end Exp. In our study, this translated to nearly 30% of patients being misclassified as having PAH rather than PH from HFpEF. (Am Heart J 2012; 163:589-94.)