Subcutaneous ICD successfully detected, converted ventricular fibrillation episodes
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An entirely subcutaneous implantable cardioverter defibrillator system was found to successfully and consistently detect and convert episodes of ventricular fibrillation in a group of small, non-randomized trials.
The researchers conducted two short-term clinical trials to determine an appropriate device configuration and assess energy requirements. They evaluated four subcutaneous ICD configurations in a study population that included patients (n=78) who were candidates for ICD implantation. Subsequently, they also tested the best configuration in additional patients (n=49) to determine the subcutaneous defibrillation threshold in comparison with that of transvenous ICD. Long-term use of subcutaneous ICD use was also followed in a pilot study (n=6) and then in a larger trial (n=55).
The best device configuration, researchers found, utilized a parasternal electrode and a left lateral thoracic pulse generator, which was as effective as a transvenous ICD for terminating induced ventricular fibrillation but with a higher mean energy requirement (36.6 ± 19.8 J vs. 11.1 ± 8.5 J). Ventricular fibrillation was detected in 100% of 137 induced episodes in patients who received a permanent subcutaneous ICD. Additionally, after a mean of 10 months, the device had detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia.
According to researchers, these studies cannot show whether subcutaneous ICDs are superior to conventional transvenous ICDs regarding such characteristics as lead stability or failure, but they shed light on the feasibility of an entirely subcutaneous ICD. However, “the relative benefit of subcutaneous ICDs, as compared with transvenous ICDs, will need to be shown in large, long-term, randomized, prospective, multicenter clinical trials,” they wrote.
Bardy GH. N Engl J Med. 2010;363:36-44.
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Appropriate ICD interventions found lacking in women
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Women had less appropriate implantable cardioverter defibrillator interventions compared with men, although there was no apparent difference with mortality, data from a study appearing in Heart Rhythm suggested.
The Texas- and Italy-based researchers utilized PubMed, Central and other databases to find studies that examined gender differences in the specified endpoints, provided the HR obtained in multiple Cox regression analyses and adjusted for all confounding variables.
They found five studies that enrolled patients (n=7,229, 22% women) with dilated cardiomyopathy. Women had no significant difference in overall mortality (HR=0.96; 95% CI, 0.67–1.39) vs. men, but had less appropriate ICD interventions (HR=0.63; 95% CI, 0.49–0.82). The ICD benefit on mortality was greater in men (HR=0.67; 95% CI, 0.58–0.78), whereas it did not attain statistical significance in women (HR=0.78; 95% CI, 0.57–1.05). Women tended to have more advanced disease than men, including a higher percentage of NYHA functional class >II (mean difference, 6.3%) and left bundle-branch block (mean difference, 7%), and more use of diuretics (mean difference, 8.7%).
This study’s findings, the researchers wrote, challenge current left ventricular ejection fraction-based prophylactic ICD recommendations and raise concerns about generalizing such recommendations to underrepresented patients in primary prevention ICD trials. These findings, they added, “call for further research with appropriate economic and social analyses to determine the cost-effectiveness of this therapy in women.”
Santangeli P. Heart Rhythm. 2010;7:876–882.
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