Surgical specimens, haemodynamics and long-term outcomes after pulmonary endarterectomy

Abstract

Background: Chronic thromboembolic pulmonary hypertension is surgically curable by pulmonary endarterectomy (PEA). It is unclear whether PEA impacts primarily steady state right ventricular afterload (ie, pulmonary vascular resistance (PVR)) or pulsatile right ventricular afterload (ie, pulmonary arterial compliance (C(PA))). Our objectives were to (1) quantify PEA specimens and measure the impact of PEA on PVR and C(PA) in a structure/function study and (2) analyse the effects of haemodynamic changes on long-term survival/freedom of lung transplantation in an outcome study.

Methods: Thrombi were laid out, weighed, photographed and measured. PVR, C(PA) and resistance times compliance (RC-time) were assessed at baseline, within 4 days after PEA ('immediately postoperative') and 1 year after PEA, in 110 consecutive patients who were followed for 34.5 (11.9; 78.3) months.

Results: Lengths and numbers of PEA specimen tails were inversely correlated with immediate postoperative PVR (p<0.0001, r=-0.566; p<0.0001, r=-0.580). PVR and C(PA) normalised immediately postoperatively while RC-time remained unchanged. Immediate postoperative PVR was the only predictor of long-term survival/freedom of lung transplantation (p<0.0001). Patients with immediate postoperative PVR<590 dynes.s.cm(-5) had better long-term outcomes than patients with PVR≥590 dynes.s.cm(-5) (p<0.0001, respectively).

Conclusions: PEA immediately decreased PVR and increased C(PA) under a constant RC-time. However, immediate postoperative PVR was the only predictor of long-term survival/freedom of lung transplantation. Our study confirms the importance of a complete, bilateral surgical endarterectomy. Low PVR measured immediately postoperative predicts excellent long-term outcome.

Keywords: Primary Pulmonary Hypertension; Pulmonary Embolism.

Figure 1

Illustration of how numbers and lengths of tails were accounted for. Tails were defined as dissectates not exceeding 2 mm in thickness and at least 2 mm in length (measured tails in this specimen are pointed out by white double-headed arrows). For the analysis, thrombus tails were counted and their total length was expressed in centimetres. The following two examples represent a ‘good’ (A) and a ‘poor’ (B) surgical specimen. (A) Surgical specimen of patient #101 with an immediate postoperative pulmonary vascular resistance (PVR) of 190 dynes.s.cm⁻⁵ and 19 thrombus tails (total tail length 24.5 cm). (B) Surgical specimen of patient #14 with an immediate postoperative PVR of 640 dynes.s.cm⁻⁵ and only four thrombus tails (total tail length 8.1 cm).

Figure 2

Scatter plots of immediate postoperative pulmonary vascular resistance (PVR) against the cumulative length of surgically extracted thrombus tails in centimetres (p<0.0001, r=−0.566 (A)) and against the cumulative number of surgically extracted thrombus tails (p<0.0001, r=−0.580 (B)).

Figure 3

Box plots of steady and pulsatile flow parameters at baseline, immediately postoperative and at 1-year follow-up (FU). (A) Pulmonary vascular resistance (PVR) decreased from preoperative 770.4 (583.2; 1011) to 368.5 (250.5; 516) immediately postoperative, and to 280 (186.3; 472) dynes.s.cm⁻⁵ at 1-year FU (p<0.001, p<0.001, ie, respective changes from baseline). (B) Pulmonary arterial compliance (C_PA) changed from 1.0 (0.8; 1.4) to 2.1 (1.5; 3.2) immediately postoperative, and to 2.7 (1.4; 3.8) mL/mm Hg at 1-year FU (p<0.001 and p<0.001). (C) Resistance times compliance (RC-time) did not change significantly during the observation period: RC-time=0.72+0.71 s (baseline), RC-time=0.60+0.3 s (immediately postoperatively) and RC-time=0.59+0.34 s (1-year FU; p=0.13 and p=0.32). (D) Stroke volume (SV) increased from preoperative 58.4±16.8 to 61.1±20.9 immediately postoperative and to 71.6±18.6 mL at 1-year FU (p=NS and p<0.001).

Figure 4

Δ Pulmonary vascular resistance (PVR) and Δ pulmonary arterial compliance (C_PA) represented as vectors from the origin, indicating changes in both PVR and C_PA between catheterisations at baseline and immediately postoperative. All patients’ vectors with persistent/recurrent pulmonary hypertension (PH) in the left-upper quadrant are localised within the circled area (representing cases with only a minor improvement in C_PA and PVR).

Figure 5

Receiver operator characteristics curve identifying an immediate postoperative pulmonary vascular resistance (PVR) of 590 dynes.s.cm⁻⁵ as the PVR threshold with greatest areas under the curve for likelihood of survival at 1, 3 and 5-year follow-ups.

Figure 6

(A) Kaplan–Meier survival curves in patients with operated chronic thromboembolic pulmonary hypertension (CTEPH) and immediate postoperative pulmonary vascular resistance (PVR)≥590 dynes.s.cm⁻⁵ compared with patients with immediate postoperative PVR<590 dynes.s.cm⁻⁵. Patients with immediate postoperative PVR<590 dynes.s.cm⁻⁵ had a better long-term outcome than patients with PVR≥590 dynes.s.cm⁻⁵ (p<0.0001). (B) Kaplan–Meier survival curves in patients with operated CTEPH by tertiles of immediate PVR (p<0.001, respectively).