Author + information
- Marc A. Miller, MD,
- Chandrasekar Palaniswamy, MD,
- Srinivas R. Dukkipati, MD,
- Sujata Balulad, MD,
- Jeffrey Smietana, MD,
- Aaron Vigdor, MD,
- Jacob S. Koruth, MD,
- Subbarao Choudry, MD,
- William Whang, MD and
- Vivek Y. Reddy, MD∗ ()
- ↵∗Helmsley Cardiac Arrhythmia Service, Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Place, Box 1030, New York, New York 10029
Defibrillation testing (DT) does not improve shock efficacy or reduce the risk for arrhythmic death in patients undergoing routine transvenous implantable cardioverter-defibrillator (ICD) placement and is no longer compulsory for left pectoral transvenous ICDs (1). The subcutaneous ICD (S-ICD) is increasingly being used for the prevention of sudden death, and studies have demonstrated high rates of successful defibrillation for both induced and spontaneous ventricular arrhythmias. However, because of an absence of outcome data on the safety and efficacy of not performing DT, a recent consensus statement recommended that intraprocedural DT should be performed following S-ICD implantation (Class I, Level of Evidence: C) (1). Given the increasing adoption of S-ICDs for the prevention of sudden death, the decision whether to perform routine DT is clinically relevant. We sought to assess the outcomes of patients who did not undergo DT following S-ICD implantation.
The study cohort included consecutive patients (n = 110) who underwent S-ICD implantation between December 2012 and October 2016. The implantation technique has been previously described. Leads were implanted in the left parasternal position, and pulse generators were implanted in either a subcutaneous, submuscular, or subfascial pocket (2). Brief fluoroscopy was used to determine anatomic landmarks. Physician preference and patient characteristics determined whether DT was performed. Patients were followed at 1 month post-implantation and then routinely with either in-office or home monitoring every 3 months. For patients who underwent DT, the first shock energy was 65 J in standard polarity. For patients who did not undergo DT, the reason was recorded. ICD shocks for spontaneous ventricular arrhythmias were recorded and retrospectively analyzed.
The characteristics of the patients are shown in Table 1. Of the 110 consecutive patients, 50% (n = 55) did not undergo DT. These patients were older (mean age 57 ± 13.7 years vs. 49 ± 16.4 years; p < 0.05) and had lower left ventricular ejection fractions (mean 30.0 ± 12.7% vs. 41.0 ± 16.6%; p < 0.05) compared with patients who underwent DT. There was no significant difference in body mass index or prevalence of ischemic cardiomyopathy. The most common reason for not performing DT was physician preference (93% [n = 51]); additional reasons included atrial fibrillation with subtherapeutic anticoagulation (6% [n = 3]) and systemic pulmonary pressures (2% [n = 1]). In the no-DT group, 6 patients (11%) developed sustained spontaneous ventricular tachycardia or fibrillation and received ICD shocks; 100% of these patients (n = 6) were successfully converted with the first shock (80 J). The appropriate shocks were for monomorphic ventricular tachycardia in 3 patients and ventricular fibrillation in the other 3 patients. The substrates of the patients who received appropriate shocks included arrhythmogenic right ventricular dysplasia (n = 1), tetralogy of Fallot (n = 1), ischemic cardiomyopathy (n = 1), and nonischemic cardiomyopathy (n = 3). The time to therapy (mean 22.6 ± 12.4 s) and shock impedance (mean 63.6 ± 11.6 Ω) were within expected ranges.
To our knowledge, this is the largest series of patients who did not undergo DT following S-ICD implantation, and we demonstrated that the conversion rate for spontaneous ventricular arrhythmias was high. In this cohort, 11% (n = 6) developed spontaneous sustained ventricular arrhythmias during follow-up, of whom 100% (n = 6) were successfully converted with a single shock at 80 J. This high rate of successful shocks in patients who did not undergo prior DT suggests that perhaps not all patients who undergo S-ICD implantation require DT. Given that DT is not benign, and an increasing number of patients are undergoing implantation, it would be appropriate to perform a randomized trial to determine whether DT improves shock efficacy or reduces arrhythmic death following S-ICD implantation (1,3).
This was a nonrandomized, single-center analysis, and physician preference was the predominant reason for not performing DT at implantation. There was heterogeneity between the 2 groups, and selection bias was evident with the significant differences in baseline demographics. The patients in the no-DT group were older and had lower ejection fractions, while those in the DT group were followed for a longer period of time. Most patients who did not undergo DT were in the second one-half of the study period, and operator experience could have played a role in improved system positioning. Also, the majority of patients who did not undergo DT underwent either submuscular (subserratus) or subfascial implantation of the pulse generator, which minimizes fat underlying the pulse generator and likely favors lower defibrillation energy requirements. Thus, these results may not be similar for purely subcutaneous implants. Although we report the largest group of patients who did not undergo DT, the overall number of patients was smaller compared with larger registries and prospective trials.
Please note: Dr. Miller has received honoraria from Boston Scientific. Dr. Reddy is a consultant for and has received grant support from Boston Scientific. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. Mike Shehata, MD, served as Guest Editor for this paper.
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