Right Ventricular Isovolumetric Relaxation Time is Associated with Pulmonary Vascular Load and Functional Limitation in Chronic Obstructive Pulmonary Disease

Fushi Dong,1,2 Yosuke Tanaka,1 Ken Okamura,1 Katsuyuki Higa,1 Shota Kaburaki,1 Yozo Sato,1 Toru Tanaka,1 Ayumi Shimizu,1,3 Susumu Takeuchi,1 Yoshiaki Kubota,4 Namiko Taniuchi,1 Koichiro Kamio,1 Kazuo Kasahara,1 Lina Wu,5 Masahiro Seike,1 Mitsunori Hino,1,3 Hiroshi Kimura1,61Department of Respiratory Medicine, Nippon Medical School Hospital, Tokyo, Japan; 2Department of Respiratory Medicine, the First Affiliated Hospital of Harbin Medical University, Harbin, People’s Republic of China; 3Respiratory Care Clinic, Nippon Medical School, Tokyo, Japan; 4Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan; 5Molecular Imaging Research Center, the Fourth Affiliated Hospital of Harbin Medical University, Harbin, People’s Republic of China; 6Respiratory Diseases Center, Fukujuji Hospital, Japan Anti-Tuberculosis Association, Tokyo, JapanCorrespondence: Yosuke Tanaka, Department of Respiratory Medicine, Nippon Medical School Hospital, Tokyo, Japan, Tel +81 3 3822 2131, Fax +81 3 5685 3075, Email yosuke-t@nms.ac.jpBackground: Pulmonary hypertension is a frequent complication of chronic obstructive pulmonary disease (COPD) and an independent determinant of prognosis. Increases in pulmonary vascular resistance often precede overt elevation of pulmonary arterial pressure, but early pulmonary vascular involvement remains difficult to detect noninvasively. Conventional echocardiographic assessment in COPD focuses mainly on right ventricular systolic indices, which may remain preserved despite increased pulmonary vascular load.Methods: We conducted a single-center retrospective observational study of 58 patients with stable COPD who underwent right heart catheterization and comprehensive transthoracic echocardiography during the same hospitalization. Right ventricular isovolumetric relaxation time (IRT), a Doppler-derived index of diastolic timing, was evaluated in relation to invasively measured pulmonary vascular resistance, dyspnea severity, exercise capacity, and pulmonary function.Results: A total of 58 patients were included. Patients meeting hemodynamic criteria for pulmonary hypertension exhibited lower diffusing capacity, more severe dyspnea, and reduced exercise capacity despite similar airflow limitation. Pulmonary vascular resistance was significantly higher, while cardiac index remained preserved. IRT was significantly prolonged in patients with pulmonary hypertension and showed a moderate correlation with pulmonary vascular resistance (ρ = 0.56, p < 0.001), six-minute walk distance (ρ = − 0.46, p < 0.001), and dyspnea severity (ρ = 0.36, p = 0.006). In contrast, conventional right ventricular systolic indices showed no significant associations with pulmonary vascular resistance.Conclusion: Echocardiographic assessment of IRT may provide a physiologically grounded, noninvasive parameter associated with early right ventricular diastolic response to pulmonary vascular load.Keywords: COPD, pulmonary hypertension, pulmonary vascular resistance, echocardiography, right ventricular function, exercise capacity