Boston, MA: Study on Repaired Tetralogy of Fallot

A recent study has revealed that adults with repaired tetralogy of Fallot (rTOF) and no more than mild right ventricular (RV) dysfunction combined with no significant RV hypertrophy are likely to be free from serious adverse clinical events into their sixth decade of life. Further, they may require less frequent cardiac testing.

"Normal or mildly decreased RV systolic function and lack of significant RV hypertrophy were associated with aborted sudden death, freedom from death, sustained and non-sustained ventricular tachycardia, atrial tachyarrhythmias, and NYHA class >II at age 50 years," Amara Majeed, Department of Pediatrics, Harvard Medical School, Boston, MA, and the team wrote in their study.

In patients with rTOF, risk stratification has focused on poor clinical outcomes while there has been no characterization of the predictors of a benign clinical course. Considering this, Dr. Majeed and colleagues aimed to identify cardiac magnetic resonance (CMR) markers of a good clinical course late after TOF repair in the study published in the American Heart Journal.

For this purpose, the researchers analyzed clinical and CMR data from the International Multicenter TOF Registry (INDICATOR). Time to the earliest occurrence of a composite of death, aborted sudden death, and sustained ventricular tachycardia was the primary outcome. The secondary outcome was time to the earliest occurrence of atrial arrhythmia, nonsustained VT, and NYHA class >II.

The researchers then identified predictors of the 3-category outcome:

• Good outcome - defined as freedom from the primary AND secondary outcomes at age 50 years
• Poor outcome - defined as the presence of the primary outcome before age 50 years
• Intermediate outcome - defined as not fulfilling criteria for good or poor outcomes

Key Findings

• Among 1088 eligible patients, 96 had good outcomes, 60 experienced poor outcomes, and 932 had an intermediate outcome.
• By univariate analysis, smaller right ventricular (RV) end-systolic and end-diastolic volume index, smaller left ventricular end-systolic volume index, higher right and left ventricular ejection fraction, lower right and left ventricular mass index, and lower left ventricular mass/volume ratio were associated with a good outcome.
• Higher RV ejection fraction (OR 2.38 per 10% increase) and lower RV mass index (OR 1.72, per 10 g/m² decrease) were identified as independently associated with good outcomes after adjusting for age at CMR.
• Classification and regression tree analysis identified important thresholds associated with a good outcome that were specific to patients age ≥37 years at the time of CMR; these were RV ejection fraction ≥42% and RV mass index <39 g/m².

Study Limitations

The study had several limitations: the cohort was restricted to patients who have undergone CMR. So, patients with pacemakers or defibrillators implanted before CMR were excluded. Additionally, the researchers did not explore other covariates such as comorbid conditions, type of original surgery, and lifestyle patterns. Also, the CMR timings could have been influenced by clinical course and impacted by era.

"In this study of patients with rTOF, a favorable RV profile characterized by no more than mild dysfunction and absence of significant hypertrophy at age 37 years and older were identified as independent predictors of good clinical outcome into the 6th decade of life," the authors wrote. "In this study, the identified thresholds of RV EF and RV mass can refine risk stratification and resource utilization in adults with rTOF."

Reference

The study titled, "Cardiac MRI predictors of good long-term outcomes in patients with repaired TOF," was published in the American Heart Journal.

DOI: https://doi.org/10.1016/j.ahj.2021.11.015