Fluid loading during the hemodynamic evaluation of pulmonary hypertension: a cross-sectional study

Background

Compensated pulmonary hypertension due to left heart disease (PH-LHD) may be difficult to identify based on resting hemodynamics. Fluid challenge is commonly used to unmask occult PH-LHD. We sought to determine the hemodynamic effect of fluid loading and its association with the clinical pretest probability of PH-LHD.

Methods

We included consecutive patients evaluated for PH who underwent right heart catheterization (RHC) with fluid challenge at Cleveland Clinic between April 2013 and January 2019. We obtained hemodynamic measurements at rest and after intravenous rapid fluid challenge (500 mL of normal saline). We calculated the pretest probability of PH-LHD based on the 6th World Symposium on PH proceedings. For statistical analyses we used t-test, analysis of variance (ANOVA), Chi-square, paired t-test, Wilcoxon signed-rank test and linear regression as indicated.

Results

We included 174 patients with mean ± standard deviation (SD) age of 63.7±13.0 years and 123 (71%) of female sex. Baseline pulmonary artery wedge pressure (PAWP) was 11±5 mmHg, with a PAWP/cardiac output (CO) ratio of 2.1±1.1 Wood units (WU). The absolute increase in PAWP and PAWP/CO was 6.9±3.6 mmHg and 1.06±0.91 WU, respectively. The change in PAWP was inversely associated with baseline PAWP (P<0.001). The PAWP with fluids was >18 mmHg in 81% of the patients with baseline PAWP 13-15 mmHg. We found no strong associations between the change in PAWP, PAWP/CO or right atrial pressure to pulmonary arterial wedge pressure ratio (RAP/PAWP) and the pretest probability of PH-LHD.

Conclusions

The absolute change in PAWP, PAWP/CO, or achieving a PAWP >18 mmHg with rapid fluid loading was not robustly associated with the pretest probability of PH-LHD. Patients with PAWP between 13-15 mmHg commonly had a positive fluid challenge, questioning the utility of this intervention in these patients.

Pulmonary hypertension due to high cardiac output

Pulmonary hypertension (PH) is usually associated with a normal or decreased cardiac output (CO). Less commonly, PH can occur in the context of a hyperdynamic circulation, characterized by high CO (>8 L/min) and/or cardiac index ≥4 L/min/m² in the setting of a decreased systemic vascular resistance. PH due to high CO can occur due to multiple conditions and in general remains understudied. In this review article we describe the pathophysiology, etiology, diagnosis, hemodynamic characteristics, and management of PH in the setting of high CO. It is important to recognize this distinct entity as PH tends to improve with treatment of the underlying etiology and PH specific therapies may worsen the hemodynamic state.

Novel Treatment Pathways in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe and progressive vascular disease characterized by pulmonary vascular remodeling, proliferation, and inflammation. Despite the availability of effective treatments, PAH may culminate in right ventricular failure and death. Currently approved medications act through three well-characterized pathways: the nitric oxide, endothelin, and prostacyclin pathways. Ongoing research efforts continue to expand our understanding of the molecular pathogenesis of this complex and multifactorial disease. Based on recent discoveries in the pathobiology of PAH, several new treatments are being developed and tested with the goal of modifying the disease process and ultimately improving the long-term prognosis.

Right heart catheterization for pulmonary hypertension during the coronavirus disease 2019 pandemic

Right heart catheterization is an essential diagnostic modality in the evaluation of pulmonary hypertension. The coronavirus disease 2019 pandemic has resulted in deferral of elective procedures including right heart catheterization. The benefits of proceeding with right heart catheterization, such as further characterization of hemodynamic subtype and severity of pulmonary hypertension, initiation of targeted pulmonary arterial hypertension therapy, as well as further hemodynamic testing, need to be carefully balanced with the risk of potentially exposing both patients and health care personnel to coronavirus disease 2019 infection. This review article aims to provide best clinical practices for safely performing right heart catheterization in pulmonary hypertension patients during the coronavirus disease 2019 pandemic.