Assessment of left ventricular preload by cardiac magnetic resonance imaging predicts exercise capacity in adult operated tetralogy of Fallot: a retrospective study.

Jonathan Yap,Ju Le Tan,Thu Thao Le,Swee Yaw Tan,Fei Gao,Ru San Tan,Liang Zhong,Reginald Liew

doi:10.1186/1471-2261-14-122

Abstract

BackgroundThe optimal timing of pulmonary homograft valve replacement (PVR) is uncertain. Cardiopulmonary exercise testing (CPET) and cardiac magnetic resonance (CMR) are often used to guide the clinical decision for PVR in operated tetralogy of Fallot (TOF) patients with significant pulmonary regurgitation (PR). We aim to study the relationship between exercise capacity and CMR in these patients.MethodsThe study is a single-centre retrospective analysis of 36 operated TOF patients [median 21.4 (interquartile range 16.4, 26.4) years post-repair; 30 NYHA I, 6 NYHA II; median age 25.2 (interquartile range 19.5-31.7) years, 29 males] with significant PR on CMR who underwent CPET within 15 [median 2.0 (interquartile range 0.8-7.2)] months from CMR. CPET parameters were compared with 30 age- and sex-matched healthy controls [median age 27.8 (interquartile range 21.0-32.8) years; 24 males].ResultsPeak systolic blood pressure (177 versus 192 mmHg, p = 0.007), Mets (7.3 versus 9.9, p < 0.001), peak oxygen consumption (VO2max) (29.2 versus 34.5 ml/kg/min, p < 0.001) and peak oxygen pulse (11.0 versus 13.7 ml/beat, p = 0.003) were significantly lower in TOF group versus control. Univariate analyses showed negative correlation between PR fraction and anaerobic threshold. There was a positive correlation between indexed left (LV) and right (RV) ventricular end-diastolic volumes, as well as indexed LV and effective RV stroke volumes, on CMR and VO2max and Mets achieved on CPET. These remained significant after adjustment for age and sex.ConclusionsTOF subjects have near normal exercise capacity but significantly lower Mets, VO2max and peak oygen pulse achieved compared to controls. Increased PR fraction in TOF subjects was associated with lower anaerobic threshold. Higher indexed effective RV stroke volume, a measure of LV preload, was associated with higher VO2max and Mets achieved, and may potentially be used as a predictor of exercise capacity.

Highlights

The optimal timing of pulmonary homograft valve replacement (PVR) is uncertain
Cardiopulmonary exercise testing (CPET) parameters Compared to controls, tetralogy of Fallot (TOF) patients achieved significantly lower maximum systolic blood pressure (177 versus 192 mmHg, p = 0.007), Mets (7.3 versus 9.9, p < 0.001), peak oxygen consumption (29.2 versus 34.5 ml/kg/min, p < 0.001) and peak oxygen pulse pressure (11.0 versus 13.7 ml/beat, p = 0.003)
There were no significant difference in the rest of the CPET parameters (Table 1). 7 TOF patients experienced arrhythmia during CPET, all consisting of occasional isolated premature ventricular complexes

Summary

Introduction

Cardiopulmonary exercise testing (CPET) and cardiac magnetic resonance (CMR) are often used to guide the clinical decision for PVR in operated tetralogy of Fallot (TOF) patients with significant pulmonary regurgitation (PR). Pulmonary regurgitation (PR) resulting from repair to the right ventricular outflow tract is a common consequence of the primary surgery. This is usually well tolerated initially, but leads to increased right ventricular (RV) dilatation, dysfunction and worsening exercise intolerance over time, and may result in arrhythmia and sudden cardiac death [2,3,4]. The optimal timing of pulmonary homograft valve replacement (PVR) in operated TOF patients with significant PR is unclear. Cardiopulmonary exercise testing (CPET) and cardiac magnetic resonance (CMR) are two important tools often used by clinicians to help guide this difficult management decision [5,6]

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