Right Ventricular Isovolumetric Relaxation Time is Associated with Pulmonary Vascular Load and Functional Limitation in Chronic Obstructive Pulmonary Disease.
Dong F, Tanaka Y, et al. • International journal of chronic obstructive pulmonary disease • 2026
Right ventricular isovolumetric relaxation time (IRT) showed a moderate correlation with pulmonary vascular resistance and functional limitation in COPD, whereas conventional right ventricular systolic indices showed no significant associations with pulmonary vascular resistance.
Key Findings
Results
Patients with COPD meeting hemodynamic criteria for pulmonary hypertension had lower diffusing capacity, more severe dyspnea, and reduced exercise capacity despite similar airflow limitation.
Study design: single-center retrospective observational study of 58 patients with stable COPD
All patients underwent right heart catheterization and comprehensive transthoracic echocardiography during the same hospitalization
Pulmonary vascular resistance was significantly higher in the pulmonary hypertension group
Cardiac index remained preserved in patients with pulmonary hypertension despite increased pulmonary vascular load
Similarity in airflow limitation between groups suggests pulmonary vascular involvement contributed independently to functional differences
Results
Right ventricular isovolumetric relaxation time (IRT) was significantly prolonged in COPD patients with pulmonary hypertension compared to those without.
IRT is a Doppler-derived index of diastolic timing
Prolongation of IRT occurred in the setting of pulmonary hypertension defined by hemodynamic criteria on right heart catheterization
Total study population: 58 patients with stable COPD
IRT was evaluated as a noninvasive echocardiographic parameter reflecting right ventricular diastolic response to pulmonary vascular load
Results
IRT showed a moderate positive correlation with invasively measured pulmonary vascular resistance.
Spearman correlation coefficient ρ = 0.56, p < 0.001
Pulmonary vascular resistance was measured via right heart catheterization
This correlation was characterized as 'moderate' by the authors
The relationship supports IRT as a noninvasive marker of pulmonary vascular load
Results
IRT showed a moderate negative correlation with six-minute walk distance in COPD patients.
Spearman correlation coefficient ρ = -0.46, p < 0.001
Six-minute walk distance was used as a measure of exercise capacity
A longer (more prolonged) IRT was associated with shorter walk distance, indicating worse exercise capacity
n = 58 patients
Results
IRT showed a significant positive correlation with dyspnea severity in COPD patients.
Spearman correlation coefficient ρ = 0.36, p = 0.006
A longer IRT was associated with more severe dyspnea
Dyspnea severity was evaluated as a distinct functional outcome measure
n = 58 patients
Results
Conventional right ventricular systolic indices showed no significant associations with pulmonary vascular resistance.
Comprehensive transthoracic echocardiography was performed including conventional right ventricular systolic indices
In contrast to IRT, standard RV systolic measures did not correlate significantly with invasively measured pulmonary vascular resistance
The authors note that systolic indices 'may remain preserved despite increased pulmonary vascular load'
This finding highlights a potential limitation of relying solely on RV systolic assessment in COPD
Background
Increases in pulmonary vascular resistance in COPD often precede overt elevation of pulmonary arterial pressure, making early noninvasive detection difficult.
Pulmonary hypertension is described as 'a frequent complication of COPD and an independent determinant of prognosis'
Conventional echocardiographic assessment in COPD focuses mainly on right ventricular systolic indices
The authors frame early pulmonary vascular involvement as 'difficult to detect noninvasively'
IRT is proposed as a physiologically grounded parameter that may capture this early phase
What This Means
This research suggests that a specific heart ultrasound measurement called right ventricular isovolumetric relaxation time (IRT) — which reflects how the right side of the heart relaxes between beats — can provide useful information about lung blood vessel disease in people with COPD. In a study of 58 stable COPD patients who all underwent both an invasive lung pressure test (right heart catheterization) and a heart ultrasound (echocardiography), patients with elevated lung blood vessel resistance had longer IRT values. Longer IRT was also associated with greater breathlessness and shorter distances walked in six minutes, suggesting a link between this heart measurement and real-world functional limitations.
Importantly, the standard measurements doctors typically use to assess right heart function — which focus on how well the heart pumps — did not show the same relationship with lung vascular resistance. This suggests that these traditional measures may miss early or important changes in the lung blood vessels of COPD patients, while IRT might capture something they do not. The correlation between IRT and invasively measured pulmonary vascular resistance was moderate (ρ = 0.56), meaning it is not a perfect substitute for the invasive test, but may add meaningful information.
This research suggests that measuring IRT during a routine heart ultrasound could help clinicians better understand why some COPD patients experience more breathlessness and reduced activity than their airway disease alone would explain. The findings point to lung blood vessel involvement as an underrecognized contributor to symptoms in COPD, and IRT as a potential noninvasive window into that process. Further research in larger groups would be needed to confirm these findings and determine how IRT might be used in clinical practice.
Dong F, Tanaka Y, Okamura K, Higa K, Kaburaki S, Sato Y, et al.. (2026). Right Ventricular Isovolumetric Relaxation Time is Associated with Pulmonary Vascular Load and Functional Limitation in Chronic Obstructive Pulmonary Disease.. International journal of chronic obstructive pulmonary disease. https://doi.org/10.2147/COPD.S628505