Identifying Risk Factors for Massive Right Ventricular Dilation in Patients With Repaired Tetralogy of Fallot

Identifying Risk Factors for Massive Right Ventricular Dilation in Patients With Repaired Tetralogy of Fallot

Cochran CD, Yu S, Gakenheimer-Smith L, Lowery R, Lu JC, Mahani MG, Agarwal PP, Dorfman AL.

Am J Cardiol. 2020 Mar 15;125(6):970-976. doi: 10.1016/j.amjcard.2019.12.016. Epub 2019 Dec 28.

PMID: 31964501

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Take Home Points:

  • In patients with rTOF, age at complete repair >6 months, longer QRS duration > 160 milliseconds, and non-Caucasian race were significantly associated with massive RV dilation by CMR.
  • An age cutoff of 6 months is clinically relevant, proposed explanations include prolonged cyanosis or elevated RV pressure load leading to myocardial damage and subsequent dilation
  • Non-Caucasian race was an unexpected and strong predictor of massive dilation. This finding could potentially contribute to an evolving understanding of inequality in outcomes and merits further investigation
  • Earlier referral for CMR in the presence of these risk factors may be indicated.


 
Commentary from Dr. Soha Romeih (Aswan, Egypt), section editor of ACHD Journal Watch:
 
Introduction: Surgical relief of RVOTO in TOF surgical repair results in pulmonary valve insufficiency and related long-term sequelae; therefore, pulmonary valve replacement (PVR) has been widely utilized to reduce RV volume overload, but optimal timing is unknown. Indexed right ventricular end-diastolic volume (RVEDVi) by CMR is a widely used predictor of poor outcomes and a subset of patients seem to have a propensity for rapid progression to severe RV dilation before initial CMR evaluation. This study aims to identify risk factors for massive RV dilation among rTOF patients presenting for their first CMR at a tertiary US institution.
 
Patients and Methods: A retrospective study, identified patients with a diagnosis of TOF who underwent their first CMR imaging study between October 2007 and March 2015. Inclusion criteria for the study were a diagnosis of TOF following complete surgical repair and first CMR performed post repair at their center. Exclusion criteria included PVR before first CMR, unknown date or type of initial repair, or lack of ventricular size measurements on CMR. Cases of massive RV dilation were defined as patients with an RVEDVi ≥200 ml/m2 measured by CMR. Controls consisted of patients within the same cohort with RVEDVi <200 ml/m2 on first CMR.
 
Results: A total of 387 patients with TOF were identified. A total of 39 cases were identified and matched to 73 controls. A flowchart depicting patient identification is shown in figure 1

 
Figure 1. Patient identification using CMR database. CMR = cardiac magnetic resonance; PVR = pulmonary valve replacement; RV = right ventricle; RVEDVi = indexed right ventricular end-diastolic volume; TOF = tetralogy of Fallot; rTOF = repaired tetralogy of Fallot
 
Median age at complete repair was 0.6 years (IQR 0.3 to 3.0 years). Transannular patch repair, a known risk for RV dilation was the most common type of repair followed by RV to pulmonary artery conduit placements, and finally, other repairs which included transatrial muscle bundle resection and ventricular septal defect closure without pulmonary artery patch. No non-transannular or “limited” transannular patches were identified as having a massive RV by our criteria. Less than half of our study cohort (46 patients, 41.1%) had total bypass time and/or cross-clamp times (45 patients, 40.2%) recorded in their surgical reports.
 
Three clinical factors were significant from univariate analysis: Non-Caucasian race, age at complete repair >6 months, and QRS duration. In multivariable analysis, all 3 factors, non-Caucasian race (AOR 7.84, p = 0.01), age at repair >6 months (AOR 2.90, p = 0.03), and QRS duration (AOR 1.03, p = 0.005) remained significant (Table 1).
 
Table 1:
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Discussion: In patients with rTOF, age at complete repair >6 months, longer QRS duration, and non-Caucasian race were significantly associated with massive RV dilation at first CMR. In this population, 10% is unlikely to have their RV return to normal size after PVR. To our knowledge, this is the first study reporting these risk factors.
 
An age cutoff of 6 months is clinically relevant, as it is at the latter end of the typical range for primary repair of TOF. An exact mechanism for this risk factor is unclear. Proposed explanations include prolonged cyanosis or elevated RV pressure load leading to myocardial damage and subsequent dilation. RV dysfunction in the setting of chronic hypoxia has not been widely investigated. Furthermore, reoxygenation of chronically hypoxic hearts during and after cardiopulmonary bypass leads to myocardial reperfusion injury.
 
The QRS interval is a clinical measurement used in some guidelines as an indication for PVR. Preoperative QRS duration has previously been shown to be an indicator of postoperative RV size and functional recovery following valve replacement. Severe QRS prolongation (≥180 milliseconds) has been linked with ventricular tachycardia and sudden death. RV ejection fraction by CMR has been shown to negatively correlate with QRS duration. The mean QRS duration in this study (160 milliseconds) matches the cutoff used as a criterion for PVR in one highly-referenced publication.
 
Non-Caucasian race was an unexpected and strong predictor of massive dilation. Additional exploration into the causes of this finding was beyond the scope of this study. However, there is a small body of literature looking at racial and ethnic disparity in mortality following congenital heart surgery. This finding could potentially contribute to an evolving understanding of inequality in outcomes and merits further investigation.
 
Conclusion: Age > 6 months at complete repair, prolonged QRS duration, and non-Caucasian race are independently associated with a massively dilated RV (RVEDVi ≥200 ml/m2) at first CMR in our rTOF patients. Earlier referral for CMR in the presence of these risk factors may be indicated. The potential role of healthcare disparities in these findings requires further investigation.
 
 

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