Right ventricular dysfunction in chronic thromboembolic obstruction of the pulmonary artery: a pressure-volume study using the conductance catheter

Abstract

Pressure-volume loops describe dynamic ventricular performance, relevant to patients with and at risk of pulmonary hypertension. We used conductance catheter-derived pressure-volume loops to measure right ventricular (RV) mechanics in patients with chronic thromboembolic pulmonary arterial obstruction at different stages of pathological adaptation. Resting conductance catheterization was performed in 24 patients: 10 with chronic thromboembolic pulmonary hypertension (CTEPH), 7 with chronic thromboembolic disease without pulmonary hypertension (CTED), and 7 controls. To assess the validity of conductance measurements, RV volumes were compared in a subset of 8 patients with contemporaneous cardiac magnetic resonance (CMR). Control, CTED, and CTEPH groups showed different pressure-volume loop morphology, most notable during systolic ejection. Prolonged diastolic relaxation was seen in patients with CTED and CTEPH [tau = 56.2 ± 6.7 (controls) vs. 69.7 ± 10.0 (CTED) vs. 67.9 ± 6.2 ms (CTEPH), P = 0.02]. Control and CTED groups had lower afterload (Ea) and contractility (Ees) compared with the CTEPH group (Ea = 0.30 ± 0.10 vs. 0.52 ± 0.24 vs. 1.92 ± 0.70 mmHg/ml, respectively, P < 0.001) (Ees = 0.44 ± 0.20 vs. 0.59 ± 0.15 vs. 1.13 ± 0.43 mmHg/ml, P < 0.01) with more efficient ventriculoarterial coupling (Ees/Ea = 1.46 ± 0.30 vs. 1.27 ± 0.36 vs. 0.60 ± 0.18, respectively, P < 0.001). Stroke volume assessed by CMR and conductance showed closest agreement (mean bias +9 ml, 95% CI -1 to +19 ml) compared with end-diastolic volume (+48 ml, -16 to 111 ml) and end-systolic volume (+37 ml, -21 to 94 ml). RV conductance catheterization detects novel alteration in pressure-volume loop morphology and delayed RV relaxation in CTED, which distinguish this group from controls. The observed agreement in stroke volume assessed by CMR and conductance suggests RV mechanics are usefully measured by conductance catheter in chronic thromboembolic obstruction.

Keywords: chronic thromboembolism; diastolic dysfunction; pulmonary hypertension; right ventricle.

Fig. 1.

Cardiac magnetic resonance (CMR) images in chronic thromboembolic disease without pulmonary hypertension (CTED) and chronic thromboembolic pulmonary hypertension (CTEPH). A: four-chamber still images from a gradient echo sequence in a patient with CTED (left) and CTEPH (right). The lefthand image displays a normal-sized right ventricle (RV) compared with the righthand image showing dilated right heart chambers, right ventricular hypertrophy, and septal straightening. B: maximum intensity projection images from a MR pulmonary angiogram from the same patients with CTED and CTEPH. Lefthand image shows proximal occlusion of left lower lobe and segmental middle lobe disease on the right. Righthand image shows proximal web in right upper lobe, complex web in right lower lobe, and complex web in proximal left lower lobe with attenuated anterior segment (block arrow).

Fig. 2.

Single beat estimation of ventricular end-systolic elastance (Ees) using isovolumic maximum pressure. Ees is a gradient extrapolated from theoretical maximum pressure to end-systole. Pmax is derived from the amplitude of the sinusoid (left). Effective pulmonary arterial elastance (Ea) is the gradient between end systole and end diastole.

Fig. 3.

Typical pressure-volume loops generated by conductance catheter in the RV during end-expiratory breathhold. Control patients (left) demonstrate triangular RV loop morphology compared with CTED (middle) and CTEPH (right) groups. Pressure differential (δP) during systolic ejection from pulmonary valve (PV) opening to end systole (ES) discriminates disease groups. PV, pulmonary valve; ES, end-systole. Absolute volumes in CTEPH patient (right hand image) unrepresentative, therefore not shown (see discussion).

Fig. 4.

Bland-Altman plots of CMR RV volume measurements vs. conductance (C) measurements. Top, stroke volume; middle, end-diastolic volume; bottom, end-systolic volume. Dark solid line indicates bias; dashed lines indicate 95% confidence interval. Conductance underestimated EDV and ESV compared with CMR whereas stroke volume showed better agreement.

Fig. 5.

Jugular insertion (left) results in closer apposition of the conductance catheter to the RV free wall compared with use of the femoral approach (right).