What is the clinical evidence from this study?

Study design: Cross-Sectional. Population: Tetralogy of Fallot (n=46). Intervention: Repaired Tetralogy of Fallot vs. Healthy controls. Primary outcome: Extracellular volume fraction (ECV) in the entire left ventricle mid short axis (p=0.84).

January 1, 2016Open Access

Increased left ventricular myocardial extracellular volume is associated with longer cardiopulmonary bypass times, biventricular enlargement and reduced exercise tolerance in children after repair of Tetralogy of Fallot

Key Result

Children after Tetralogy of Fallot repair did not have significantly higher left ventricular extracellular volume fraction compared to healthy controls (23.6% vs 23.4%, p=0.84).

Study Design

Type

Cross-Sectional (n=46)

Multicenter

Structured PICO

Are left ventricular myocardial extracellular volume and native T1 times increased in children after Tetralogy of Fallot repair compared to controls, and are they associated with surgical factors or exercise tolerance?

Population

46 children and adolescents, comprising 31 patients after Tetralogy of Fallot (TOF) repair (mean age 13.9 ± 2.4 years, 61% male) and 15 controls (mean age 13.4 ± 2.6 years, 44% male). Single-center study.

Intervention

Cardiovascular magnetic resonance (CMR) with T1 mapping to quantify native T1 times and extracellular volume fraction (ECV)

Comparator

15 controls who underwent CMR for screening purposes (palpitations, non-specific chest pain, or family history of arrhythmogenic right ventricular cardiomyopathy) with normal CMR and tests

Outcome

Native T1 times and extracellular volume fraction (ECV) in the left ventricular myocardiumsurrogate

In children after Tetralogy of Fallot repair, diffuse left ventricular myocardial fibrosis is not increased compared to controls, but higher fibrosis markers correlate with longer surgical bypass times, biventricular enlargement, and reduced exercise tolerance.

Main Result

Absolute Event Rate: 23.6% vs 23.4%

p-value: p=0.84

Limitations

Limited sample size
Unclear whether ECV offers a diagnostic advantage over non-contrast native T1
Motion-correction algorithm remains inferior to acquisitions during breathholding
Quantification of post-contrast T1 in the right ventricle of children without myocardial hypertrophy often fails, precluding RV ECV analysis

Abstract

BACKGROUND: Unfavorable left ventricular (LV) remodelling may be associated with adverse outcomes after Tetralogy of Fallot (TOF) repair. We sought to assess T1 cardiovascular magnetic resonance (CMR) markers of diffuse LV myocardial fibrosis in children after TOF repair, and associated factors. METHODS: In this prospective, cross-sectional study, native (=non-contrast) T1 times and extracellular volume fraction (ECV) were quantified in the LV myocardium using CMR. Results were related to ventricular volumes and function, degree of pulmonary regurgitation, as well as surgical characteristics, and exercise capacity. RESULTS: There was no difference in native T1 times or ECV between 31 TOF patients (age at CMR 13.9 ± 2.4 years, 19 male) and 15 controls (age at CMR 13.4 ± 2.6 years, 7 male). Female TOF patients had higher ECVs than males (25.2 ± 2.9 % versus 22.7 ± 3.3 %, p < 0.05). In the patient group, higher native T1 and ECV correlated with higher Z-Scores of right and left ventricular end-diastolic volumes, but not with reduced left and right ventricular ejection fraction or higher pulmonary regurgitation fraction. Longer cardiopulmonary bypass and aortic cross clamp times at surgery correlated with increased native T1 times and ECVs (r = 0.48, p < 0.05 and r = 0.65, p < 0.01, respectively). Maximum workload (percent of predicted for normal) correlated inversely with ECV (r = -0.62, p < 0.05). Higher native T1 times correlated with worse LV longitudinal (r = 0.50, p < 0.05) and mid short axis circumferential strain (r = 0.38, p < 0.05). CONCLUSIONS: As compared to controls, TOF patients did not express higher markers of diffuse fibrosis. Longer cardiopulmonary bypass and aortic cross clamp times at surgery as well as biventricular enlargement and reduced exercise tolerance are associated with markers of diffuse myocardial fibrosis after TOF repair. Female patients have higher markers of diffuse myocardial fibrosis than males.

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