Distribution of normalized pulmonary transit time per pathology in a population of routine CMR examinations

Pulmonary transit time (PTT), defined as the time taken for a contrast agent bolus to pass from the right ventricle to the left ventricle, is a surrogate for non-invasive assessment of preload. It is used in several imaging modalities: pulmonary angiography, echocardiography and cardiac magnetic resonance (CMR). Many recent studies have highlighted the prognostic value of PTT. Therefore, we sought to evaluate PTT in a consecutive cohort of patients undergoing CMR. We retrospectively evaluated PTT normalised for heart rate in 278 patients (66% male, mean age 58 ± 11 years) who underwent CMR between August 2017 and November 2021 with a diagnosis of dilated cardiomyopathy, infarct, hypertrophy, valvular, myocarditis, other pathology or no pathology ("normal"). Normalised pulmonary transit time (nPTT) was higher in men than in women (8.4 ± 1.3 beats vs 7.5 ± 1.1 beats, p = 0.002) in the "normal" group. nPTT was moderately correlated with left ventricular end-diastolic volume (LVEDV) (r² = 0.19; p < 0.001), left ventricular end-systolic volume (LVESV) (r² = 0.34; p < 0.001) and left ventricular ejection fraction (LVEF) (r² = 0.29; p < 0.001). nPTT was significantly higher in patients with dilated cardiomyopathy (11.3 ± 5.4 beats; p < 0.001), infarct (9.5 ± 2.9 beats; p < 0.001) or valvular heart disease (9.5 ± 3.1 beats; p = 0.006) than in patients included in the "normal" group (7.9 ± 1.3 beats). The nPTT is an important marker of pathology. Its value depends on sex and type of pathology, but it is not specific for any type of pathology.