EXERCISE HEMODYNAMICS TO REVEAL LATENT PULMONARY VASCULAR ABNORMALITIES AMONG CHRONIC THROMBOEMBOLIC DISEASE PATIENTS

BACKGROUND Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by persistent and organized pulmonary thrombi and pulmonary hypertension (PH). Right heart catheterization (RHC) is the gold standard for diagnosis of PH, defined by a resting mean pulmonary artery pressure (mPAP) > 20 mmHg. Chronic organized thrombi, in the absence of PH at rest is termed chronic thromboembolic disease (CTED). Pulmonary endarterectomy (PEA) is indicated for CTEPH, however PEA is not routinely endorsed for CTED. Exercise is increasingly employed as a provocative maneuver during RHC to elicit abnormalities of pulmonary vascular and cardiac physiology in patients without PH at rest who are at risk of pulmonary vascular disease. Exercise RHC may expose abnormalities of pulsatile or resistive pulmonary vascular afterload in CTED patients and may potentially identify a subset of CTED patients who benefit from PEA surgery. We describe the proportion of CTED patients with latent pulmonary vascular hemodynamic abnormalities and their hemodynamic characteristics. METHODS AND RESULTS Consecutive patients with a resting mPAP ≤ 20 mmHg and CTED who completed an exercise hemodynamic study between November 2016 and September 2020 were included. We defined exercise abnormalities of pulmonary resistive load as mPAP/CO > 3 WU and exercise abnormalities of pulsatile load as the ratio of pulmonary pulse pressure to pulmonary artery wedge pressure (PP/PAWP) > 2.5. Thirty-seven CTED patients (32% female, 55±15 years) were analyzed. Resting hemodynamics for the entire cohort and exercise hemodynamics for patients with and without latent pulmonary vascular abnormalities are shown (Table 1). Twenty-two patients (59%) demonstrated latent pulmonary vascular abnormalities; 12 had an elevated pulsatile load (PP/PAWP 5.3±4.5), 5 had an elevated resistive load (mPAP/CO 3.7±0.7 WU) and 5 had both (mPAP/CO 3.7±0.5 WU, PP/PAWP 7.3±3.6). Patients with latent pulmonary vascular abnormalities exercised to lower work-rates (P=0.03) and had lower exercise PAWP (P=0.02). They were also characterized by higher pulmonary vascular resistance (P CONCLUSION Patients with CTED and resting mPAP ≤ 20mmHg, exercise demonstrated latent abnormal pulmonary vascular responses in over 50% of patients. These patients predominantly demonstrated abnormalities of pulsatile afterload relative to resistive afterload. Further study is required to understand if these patients benefit from PEA surgery.