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

Introduction : Pulmonary Transit Time (PTT), defined as the time required for a contrast bolus to pass from the right ventricle to the left ventricle, is a surrogate for noninvasive preload assessment. It is used in different imaging modalities: pulmonary angiography, echocardiography and cardiac magnetic resonance (CMR). Purpose : Many recent studies have highlighted the prognostic value of PTT. Therefore, we sought to evaluate PTT in a consecutive cohort of patients undergoing CMR. Methods: We retrospectively evaluated PTT normalized 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”). Results : Normalized 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 suffering from dilated cardiomyopathy (11.3 ± 5.4 beats ; p < 0.001), infarct (9.5 ± 2.9 beats ; p < 0.001) or valvular disease (9.5 ± 3.1 beats ; p = 0.006) than in patients included in the “normal” group (7.9 ± 1.3 beats). Conclusion : nPTT is a novel major surrogate for the preload status of the patient. Its value depends on gender and type of pathology.