Contributor: Elise Vo
We’re talking Group 2 PAH here. Diastolic pressure difference (DPD) [diastolic pulmonary artery pressure (dPAP) minus pulmonary capillary wedge pressure (PCWP)] identifies isolated post capillary pulmonary hypertension (Ipc-PH) (DPD ≤ 7 mmHg) in group 2 patients. A diastolic pressure difference of > 7 mmHg defines combined pre-post capillary pulmonary hypertension (Cpc-PH)). Prior to heart transplantation, classification of pulmonary hypertension as Ipc-PH or Cpc-PH is important. Unlike Ipc-PH, Cpc-PH is associated with increased morbidity and mortality related to right ventricular graft failure post heart transplant. Even in the hands of seasoned invasive hemodynamic practitioners, measurement of DPD may not be as straightforward as it seems. Those tracings move, and these pressure differences are small!
Accurate DPD calculation depends on accurate dPAP and PCWP measurements. Measurement of PCWP may be particularly challenging in the presence of the large v-waves of mitral regurgitation. Authors publishing in Circulation: Heart Failure suggest that use of QRS-gating mitigates the systolic v-wave influence on mean PAWP measurements.
Using digital calipers and QRS-gating, Wright et al averaged mean diastolic PCWP over 8-10 cardiac cycles [Figure 1]. This method was compared to PCWP acquired during end expiratory breath hold. The authors found that the usual method may overestimate PCWP, and therefore underestimate DPD and fail to accurately identify patients with true Cpc-PH.
The study included 141 advanced HFrEF patients (mean EF 25%, 49% ICM, mean age 49 years old). The QRS-gated DPD (3 mmHg) was higher compared to standard method (0 mmHg) (p<0.01). QRS-gated classification led to 17 (24%) patients with Cpc-PH as compared to 6 (8%) by standard method (p<0.002). Cpc-PH patients (calculated by both methods) were found to have higher PA pressures and PVR compared to Ipc-PH patients. Worth mentioning: one-year mortality was similar between 2 groups, but the QRS-gated Cpc-PH group had a lower rate of cardiac transplantation.
In a heartbeat… QRS-gated PAWP measurements may be more accurate than breath-hold average of PCWP, and more accurately classify HFrEF patients with either Ipc-PH or Cpc-PH.