• Cardiology Clinical Trials
• Interventional Techniques & Devices

• Cardiology Clinical Trials
• Interventional Techniques & Devices
• Cardiology

Late-breaking results from the prospective Shock-Less study indicated that providing clinicians with reports about implantable cardioverter defibrillator (ICD) programming improved adherence to shock-reduction guidelines in real-world practice settings, and significantly reduced the risk of unnecessary ICD shocks in patients. Marc T. Silver, MD, WakeMed Physician Practices, Raleigh, North Carolina, USA, presented the findings.

A total of 4131 patients implanted with a single- or dual-chamber ICD or cardiac resynchronization therapy defibrillator system participated in the study from 2009 to 2012 across 118 international sites. Most patients (85%) were treated with ICDs for primary prevention, with a median follow-up of 22 months after enrollment. After a period of 9 to 12 months, clinicians who programmed ICD shock parameters received therapy reports specific to their clinical sites and patient populations. The reports compared clinicians' programming habits with the targets established in the evidence-based recommendations. These targets included the number of intervals to detect ventricular fibrillation, the longest treatment interval, supraventricular tachycardia discriminators, antitachycardia pacing, and a Lead Integrity Alert (Table 1).

Clinicians programmed devices at their own discretion; appropriate or inappropriate shock episodes were determined by an independent committee.

The control group (Group 1; n=2693) consisted of patients who were implanted before the clinician received a therapy report. The intervention arm (Group 2; n=1438) included patients who were implanted after the first therapy report was delivered, with time to first all-cause shock as the primary endpoint.

The study found that 381 patients experienced at least one shock event: 265 occurred in Group 1 and 116 in Group 2. Patients in Group 2 had a 27% relative risk reduction in all-cause shock episodes as compared with Group 1 (HR, 0.73; 95% CI, 0.58 to 0.91; p=0.005). The number of unnecessary shocks fell by the same percentage; among the 162 patients who experienced inappropriate shocks, 114 occurred in Group 1 and 48 in Group 2.

The risk reduction remained significant (HR, 0.71; 95% CI, 0.57 to 0.89; p=0.002) after adjusting for a number of factors, including the patient's device history, age, blood pressure, and history of atrial fibrillation, smoking coronary artery disease, statin use, NYHA class, and coronary bypass surgery.

These findings suggest that improving clinician adherence to evidence-based ICD programming guidelines holds promise in reducing morbidity—and potential mortality—in ICD patients. The study investigators have posed alternative methods of increasing clinician compliance, such as enhancing algorithms and having ICD manufacturers institute nominal device settings that reflect current guidelines.

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