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Novel algorithm led to low rate of inappropriate ICD shocks
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A novel discrimination algorithm designed to distinguish between true ventricular arrhythmias and other rhythms was associated with a low rate of inappropriate shocks in patients with single- and dual/triple-chamber implantable cardioverter defibrillators, according to new data from the PainFree SST study.
Researchers enrolled 2,790 patients with an approved indication for ICD implantation (mean age, 65 years; 79% men) in the prospective trial. All patients received a single- or dual/triple-chamber ICD (Protecta, Medtronic) with a set of six discrimination algorithms designed to distinguish between true ventricular arrhythmias and other rhythms (SmartShock Technology, Medtronic). Patients were analyzed separately by ICD type (single-chamber vs. dual/triple-chamber).
Angelo Auricchio
The primary endpoint was percentage of patients who received at least one inappropriate shock at 1 year. Secondary endpoints included percentage of patients who received any inappropriate therapy, incidence of appropriate device therapy, undertreatment of ventricular arrhythmias and all-cause mortality.
Inappropriate shocks rare
For patients with dual/triple-chamber ICDs, the incidence of inappropriate shock was 1.5% (95% CI, 1-2.1) at 1 year, 2.8% (95% CI, 2.1-3.8) at 2 years and 3.9% (95% CI, 2.8-5.4) at 3 years. For patients with single-chamber ICDs, the incidence of inappropriate shock was 2.5% (95% CI, 1.5-3.9) at 1 year and 3.7% (95% CI, 2.2-5.7) at 2 years, according to the results. The researchers observed 84 episodes of inappropriate shocks in 48 of 2,019 patients with dual/triple-chamber ICDs and 31 episodes of inappropriate shocks in 22 of 751 patients with single-chamber ICDs.
Incidence of any inappropriate therapy was 2.3% (95% CI, 1.7-3.1) at 1 year, 3.7% (95% CI, 2.8-4.8) at 2 years and 5.7% (95% CI, 4-7.6) at 3 years for patients with dual/triple-chamber ICDs and 3.4% (95% CI, 2.2-5) at 1 year and 4.8% (95% CI, 3.2-7) at 2 years for patients with single-chamber ICDs.
The most common cause of inappropriate shock in all device types was atrial fibrillation, followed by oversensing due to electrogram noise. Independent predictors of inappropriate shocks included prior AF (HR = 2.9; P = .0001), history of ventricular tachycardia (HR = 2.2; P = .001) and absence of prior MI (HR = 2.3; P = .009), according to the results.
Appropriate shocks were delivered in 5.9% (95% CI, 4.9-7.1) of patients at 1 year and 10.1% (95% CI, 8.6-11.7) at 2 years in patients with dual/triple-chamber ICDs and in 6.5% (95% CI, 4.8-8.5) of patients at 1 year and 10.4% (95% CI, 7.8-13.3) at 2 years in those with single-chamber ICDs.
No deaths related to technology
Overall, there were 230 deaths during the study period, none of which were related to inappropriate device therapy or inappropriately withheld device therapy, according to the researchers. Estimated mortality at 2 years was 10.2% (95% CI, 8.7-11.6) in patients with dual/triple-chamber ICDs and 6% (95% CI, 3.9-8) in those with single-chamber ICDs.
The discrimination algorithms withheld therapy for 9,863 episodes; of the 3,291 episodes detected by electrogram, therapy was appropriately withheld 98.6% of the time, the researchers wrote. Relative sensitivity at detecting true ventricular arrhythmias was 98.8%.
“The new results from PainFree SST reinforce that SmartShock Technology streamlines programming to help deliver shocks only when necessary to save a life, and that ICD programming truly matters in improving outcomes,” Angelo Auricchio, MD, PhD, FESC, of Fondazione Cardiocentro Ticino, Lugano, Switzerland, said in a press release. – by Erik Swain
Disclosures: The study was funded by Medtronic. Auricchio reports consulting and receiving speaker fees from Medtronic. Other researchers report financial ties with Biotronik, Boston Scientific, Cordis, Medtronic, Sorin and St. Jude Medical.
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