Letter by Book et al Regarding Article, “Pulmonary Valve Replacement in Tetralogy of Fallot: Impact on Survival and Ventricular Tachycardia”
To the Editor:
Although we applaud the efforts of Harrild et al1 in a recent issue of Circulation to address the important issue of the timing and benefits of pulmonary valve replacement (PVR) in patients with tetralogy of Fallot who have had previous pulmonary valve disruption, we do not feel the data support the conclusion that “compared with a group of similar control subjects, PVR did not result in improved survival.” The authors acknowledge a critical baseline difference between the PVR and control group, a significant difference in mean baseline magnetic resonance imaging right ventricular end-diastolic volume index (196 mL/m2 versus 132 mL/m2). Previous studies2 have shown that right ventricular recovery is compromised in patients with a preoperative right ventricular end-diastolic volume index >175 mL/m2, suggesting the need for earlier intervention.
Harrild et al retrospectively compared 2 cohorts of patients: one with clinical indicators for PVR and significant enlargement of the right ventricle to a cohort without clinical indicators for PVR who had significantly smaller right ventricles. Matching was done both by age and QRS duration; however, permitting up to a 30 ms difference in QRS duration allows potential for a significant difference in baseline risk of sudden cardiac death and ventricular arrhythmias. Perhaps the authors could comment on the baseline sudden death/ventricular tachycardia risk score in both groups, as previously described by Khairy et al,3 to assess baseline risk.
The data does support the previously published observation that prolonged QRS duration is associated with a higher incidence of VT4 in both groups (with and without PVR) and challenges a previous publication that PVR decreases the arrhythmic risk.5 In our opinion, the data support a different conclusion: Patients with a prolonged QRS duration and/or other risk factors for sudden death warrant further risk stratification for sudden death regardless of the decision to proceed with PVR. Although the authors mention that 18 of 98 PVR patients had QRS durations >180 ms, a predictor of sudden-death risk, the number of control patients with a QRS duration >180 ms is not clear.
We feel the study findings do not support the lack of mortality benefit of PVR late after tetralogy of Fallot in comparison to a strategy of observation. In our opinion, further study is needed before concluding that patients with pulmonary valve disruption do not derive mortality or arrhythmic benefit from PVR.
Harrild DM, Berul CI, Cecchin F, Geva T, Gauvreau K, Pigula F, Walsh EP. Pulmonary valve replacement in tetralogy of Fallot: impact on survival and ventricular tachycardia. Circulation. 2009; 119: 445–451.
Khairy P, Harris L, Landzberg MJ, Viswanathan S, Barlow A, Gatzoulis MA, Fernandes SM, Beauchesne L, Therrien J, Chetaille P, Gordon E, Vonder Muhll I, Cecchin F. Implantable cardioverter-defibrillators in tetralogy of Fallot. Circulation. 2008; 117: 363–370.
Gatzoulis MA, Till JA, Somerville J, Redington AN. Mechanoelectrical interaction in tetralogy of Fallot: QRS prolongation relates to right ventricular size and predicts malignant ventricular arrhythmias and sudden death. Circulation. 1995; 92: 231–237.
Therrien J, Siu SC, Harris L, Dore A, Niwa K, Janousek J, Williams WG, Webb G, Gatzoulis MA. Impact of pulmonary valve replacement on arrhythmia propensity late after repair of tetralogy of Fallot. Circulation. 2001; 22: 2489–2494.