We read the article by Shariff et al, suggesting a higher failure rate of single-coil compared with dual-coil Sprint Quattro implantable cardioverter defibrillator (ICD) leads. However, we have concerns regarding the investigators’ conclusions and the level of confidence with which they are expressed.

The investigators present a single-center study relying on retrospective analysis of data collected in the course of routine clinical care in which they found a higher rate of ICD lead failure in single-coil compared with dual-coil Sprint Quattro models. A major limitation of the analysis is the short mean follow-up of only 3.4 years for dual-coil leads and 1.3 years for single-coil leads, despite a study period of almost 14 years. This limitation is illustrated by inspection of the Kaplan-Meier survival curve, which shows that only 7 single-coil leads remained at risk at 4 years. In contrast, an analysis of the Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-CRT) trial, which, although post hoc, enjoyed the benefit of using prospectively collected clinical trial data found no difference between single- and dual-coil models in the crude or adjusted incidence of RV lead–related complications. Although the proportion of single-coil leads in this analysis was small (162/1,783 vs 631/1,651 in the present study), potentially limiting power, mean follow-up duration was substantially longer (40 vs 25.9 months).

Although the single- and dual-coil groups were similar with respect to age and gender, the single-coil group had a higher mean ejection fraction, a known association with ICD lead failure. Other patient variables known to be associated with an increased risk of ICD lead failure in other models, such as previous lead failure, hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia and channelopathies, right-sided implant, and subpectoral position, may also confound results. Implant technique has an important influence on long-term lead survival, and certain approaches, such as cephalic vein access, have been associated with lower failure rates in some ICD leads. These preferences likely co-segregate with selection of single- or dual-coil leads in a single center with a limited number of operators.

Last, the analysis the investigators quote in support of the assertion that single-coil Riata leads have worse survival than dual-coil leads included only 30 single-coil leads and as such is vulnerable to a type I error. Although conductor externalization has been found to be more common in single-coil 8Fr models, we are not aware of any other reports that single coil are more likely than dual-coil Riata leads to display “electrical” abnormalities: many analyses have been limited by the small number of single-coil leads implanted.

Although the conclusion drawn in the abstract is appropriately circumspect, in the text the association is said to have been “demonstrated” and “documented.” It must be emphasized that observational data such as those presented are hypotheses generating and that such definite statements are inappropriate. Given the limitations described earlier, the increased complexity and complication rate seen with extraction of dual-coil ICD leads (as acknowledged by the investigators), the increased risk of venous obstruction, similarity in defibrillation threshold with modern waveforms, and the lack of clinical benefit in several studies including a prespecified analysis of the landmark Sudden Cardiac Death in Heart Failure trial, the weight of evidence is in favor of single-coil ICD leads remaining the appropriate choice for the great majority of patients.