Response to Letter Regarding Article, “Pulmonary Valve Replacement in Tetralogy of Fallot: Impact on Survival and Ventricular Tachycardia”
We would like to thank Dr Book and colleagues for their thoughtful appraisal of our recent article describing long-term outcomes in patients with tetralogy of Fallot after pulmonary valve replacement (PVR).1 In designing this study, our intent was to catalog the clinical outcomes of patients at our institution following this procedure, and to contextualize our observations by providing a comparison to a similar group of patients that had not undergone PVR. That at least a subset of the control cohort was imperfectly matched to the PVR patients was inherent in the study design, as an analysis of retrospective data. Book et al take specific issue with the reported differences in magnetic resonance imaging–derived indexed right ventricular end-diastolic volume. From their letter, however, it is not clear if they were aware that these data were available only for a relatively small subset of the entire cohort (35/77 patients). What is known for the entire cohort, however, is QRS duration, for which there was no statistically significant difference. Book et al highlight the use of 180 ms as a cutoff dividing high- from low-risk groups. Among the 2 cohorts in our article, the presence of “high-risk” QRS duration was no different between the 2 groups (14 versus 13 out of 77 for controls and PVR patients, respectively). Moreover, the historical controls that we identified shared a great number of other known risk factors for poor outcomes with the PVR patients (eg, left ventricular dysfunction, type of repair, age at repair, era of repair, presence of ventricular tachycardia, and chronological age). The first of these risk factors, left ventricular dysfunction, had the highest odds ratio for adverse long-term outcomes (defined as death, ventricular tachycardia, and increase in New York Heart Association class to III to IV) in a recent publication by Knauth et al.2 Given these many commonalities, we do not think that it is unreasonable for us to refer to the 2 groups of patients as “similar.” The request by Book et al for us to apply the baseline ventricular tachycardia risk score formulated by Khairy et al3 is unfortunately thwarted by this model’s fundamental reliance on left ventricular end-diastolic pressure, a measure nearly uniformly unavailable in these patients around the time of PVR.
Against the background of the experience of the controls, we were surprised to find that not only did the PVR group not enjoy improved outcomes, for the survival outcome their trajectory was in fact nearly statistically worse. We interpret this finding to mean that the magnitude of the benefit provided by PVR vis-à-vis survival and protection from ventricular tachycardia, if there is one, is unlikely to be very large. We acknowledge wholeheartedly that our work may serve to raise more questions than it provides answers. Our findings, however, add to a growing number of recent reports in the literature that have failed to document a long-term survival or arrhythmia benefit from late PVR in repaired tetralogy of Fallot.4,5
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.
Knauth AL, Gauvreau K, Powell AJ, Landzberg MJ, Walsh EP, Lock JE, del Nido PJ, Geva T. Ventricular size and function assessed by cardiac MRI predict major adverse clinical outcomes late after tetralogy of Fallot repair. Heart. 2008; 94: 211–216.
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.
Gengsakul A, Harris L, Bradley TJ, Webb GD, Williams WG, Siu SC, Merchant N, McCrindle BW. The impact of pulmonary valve replacement after tetralogy of Fallot repair: a matched comparison. Eur J Cardiothorac Surg. 2007; 32: 462–468.