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).

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.

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).

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.