Cardiac Magnetic Resonance Evaluation of Pulmonary Transit Time and Blood Volume in Adult Congenital Heart disease.

Background: Management of adults with repaired congenital heart disease (CHD) is still challenging. Heart failure secondary to residual anatomical sequels or arrhythmic events is not rare in this population. MRI has emerged as an accurate tool to quantify pulmonary transit time (PTT) of intravenous contrast agents and pulmonary blood volume (PBV).

Purpose: To determine the relationship between PTT, and conventional indexes of ventricular dysfunction and heart failure in a cohort of adults with CHD and to assess its association with adverse outcomes.

Study Type: Retrospective.

Subjects: 89 adult CHD patients (56 males, age 34 ± 11 years) and 14 age- and sex-matched healthy subjects.

Field Strength/sequence: First-pass perfusion and standard sequences for ventricular volumes and function and flow analysis at 1.5T.

Assessment: PTT was calculated as the time required for a bolus of contrast agent to pass from the right ventricle to the left atrium, expressed both in seconds (PTTS) and number of heartbeats (PTTB). The pulmonary blood volume index (PBVI) was measured by the product of PTTB and the pulmonary artery stroke volumes.

Statistical Tests: Student's independent t-test analysis of variance (ANOVA) and Mann-Whitney nonparametric; Pearson's or Spearman's correlation; Kaplan-Meier method.

Results: PTTS and PTTB were significantly higher in patients than in controls (7.6 ± 3 vs. 5.6 ± 1.2 sec, P = 0.01 and 8 ± 3 vs. 6 ± 1 bpm, P = 0.01, respectively). PTTS showed negative correlation with left ventricle ejection fraction (LVEF) and cardiac index (CI) (r = -0.3, P = 0.004, and r = -0.4, P < 0.001, respectively) as well as with left ventricle and atrial volumes. By Kaplan-Meier survival analysis, PTTB >8 bpm was associated with significant increased risk of adverse outcome at mid-term follow-up. Moreover, patients with both increased PTTB and PBV have higher amino-terminal portion of the prohormone brain natriuretic peptide (NT-proBNP) and lower LVEF.

Data Conclusion: PTT is prolonged in adult CHD in comparison with healthy subjects, likely reflecting reduced CI and ventricular dysfunction.

Level Of Evidence: 3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;50:779-786.