Feasibility and Diagnostic Potential of Pulmonary Transit Time Measurement by Contrast Echocardiography: A Pilot Study.

AIMS: Pulmonary transit time (PTT; the time for ultrasound contrast to travel from the right ventricle [RV] to the left atrium) may provide a single metric that reports on cardiopulmonary function while overcoming some of the challenges of standard echocardiographic measures. We conducted a pilot study to test the feasibility and reproducibility of echocardiographically derived PTT and to determine its association with established measures of cardiopulmonary function. METHODS AND RESULTS: A total of 39 patients receiving clinically indicated ultrasound contrast were prospectively enrolled. PTT was measured in the apical four-chamber view using commercially available software. Reproducibility and inter-observer agreement were assessed in 9 patients. PTT was correlated with established measures of left ventricular systolic and diastolic function, RV function, and pulmonary vascular status. PTT could be measured in 89% (33/37) of patients without a contraindication to ultrasound contrast; all measurements from the last 20 patients were interpretable and obtained independently by a sonographer. Reproducibility and inter-observer agreement were excellent. PTT correlated well with standard echocardiographic indicators of cardiac status. A PTT >4.5 seconds accurately identified all but 1 patient with cardiopulmonary dysfunction. CONCLUSIONS: This pilot study demonstrates that measurement of PTT using ultrasound contrast is highly reproducible, accurately reflects global cardiopulmonary function across a range of cardiopulmonary disease, and can be readily obtained by an independent sonographer. Further studies are needed to determine whether PTT has incremental value in diagnosis and prognosis compared to conventional echocardiographic parameters.

Features Associated With Discordance Between Pulmonary Arterial Wedge Pressure and Left Ventricular End Diastolic Pressure in Clinical Practice: Implications for Pulmonary Hypertension Classification.

BACKGROUND: The measurements used to define pulmonary hypertension (PH) etiology, pulmonary arterial wedge pressure (PAWP), and left ventricular end-diastolic pressure (LVEDP) vary in clinical practice. We aimed to identify clinical features associated with measurement discrepancy between PAWP and LVEDP in patients with PH. METHODS: We extracted clinical data and invasive hemodynamics from consecutive patients undergoing concurrent right and left heart catheterization at Vanderbilt University between 1998 and 2014. The primary outcome was discordance between PAWP and LVEDP in patients with PH in a logistic regression model. RESULTS: We identified 2,270 study subjects (median age, 63 years; 53% men). The mean difference between PAWP and LVEDP was -1.6 mm Hg (interquartile range, -15 to 12 mm Hg). The two measurements were moderately correlated by linear regression (R = 0.6, P < .001). Results were similar when restricted to patients with PH. Among patients with PH (n = 1,331), older age (OR, 1.77; 95% CI, 1.23-2.45) was associated with PAWP underestimation in multivariate models, whereas atrial fibrillation (OR, 1.75; 95% CI, 1.08-2.84), a history of rheumatic valve disease (OR, 2.2; 95% CI, 1.36-3.52), and larger left atrial diameter (OR, 1.70; 95% CI, 1.24-2.32) were associated with PAWP overestimation of LVEDP. Results were similar in sensitivity analyses. CONCLUSIONS: Clinically meaningful disagreement between PAWP and LVEDP is common. Atrial fibrillation, rheumatic valve disease, and larger left atrial diameter are associated with misclassification of PH etiology when relying on PAWP alone. These findings are important because of the fundamental differences in the treatment of precapillary and postcapillary PH.

Hemodynamic evidence of vascular remodeling in combined post- and precapillary pulmonary hypertension.

Although commonly encountered, patients with combined postcapillary and precapillary pulmonary hypertension (Cpc-PH) have poorly understood pulmonary vascular properties. The product of pulmonary vascular resistance and compliance, resistance-compliance (RC) time, is a measure of pulmonary vascular physiology. While RC time is lower in postcapillary PH than in precapillary PH, the RC time in Cpc-PH and the effect of pulmonary wedge pressure (PWP) on RC time are unknown. We tested the hypothesis that Cpc-PH has an RC time that resembles that in pulmonary arterial hypertension (PAH) more than that in isolated postcapillary PH (Ipc-PH). We analyzed the hemodynamics of 282 consecutive patients with PH referred for right heart catheterization (RHC) with a fluid challenge from 2004 to 2013 (cohort A) and 4,382 patients who underwent RHC between 1998 and 2014 for validation (cohort B). Baseline RC time in Cpc-PH was higher than that in Ipc-PH and lower than that in PAH in both cohorts (P < 0.001). In cohort A, RC time decreased after fluid challenge in patients with Ipc-PH but not in those with PAH or Cpc-PH (P < 0.001). In cohort B, the inverse relationship of pulmonary vascular compliance and resistance, as well as that of RC time and PWP, in Cpc-PH was similar to that in PAH and distinct from that in Ipc-PH. Our findings demonstrate that patients with Cpc-PH have pulmonary vascular physiology that resembles that of patients with PAH more than that of Ipc-PH patients. Further study is warranted to identify determinants of vascular remodeling and assess therapeutic response in this subset of PH.