Improve the prevention of sudden cardiac arrest in emerging countries: the Improve SCA clinical study design.

Aims: This study aims to demonstrate that primary prevention (PP) patients with one or more additional risk factors are at a similar risk of life-threatening ventricular arrhythmias when compared with secondary prevention (SP) patients, and would receive similar benefit from an implantable cardioverter defibrillator (ICD), or cardiac resynchronization therapy-defibrillator (CRT-D) implant. The study evaluates the benefits of therapy for high-risk patients in countries where defibrillation therapy for PP of SCA is underutilized.

Methods: Enrolment will consist of 4800 ICD-eligible patients from Asia, Latin America, Eastern Europe, the Middle East, and Africa. Upon enrolment, patients will be categorized as SP or PP. Primary prevention patients will be assessed for additional risk factors: syncope/pre-syncope, non-sustained ventricular tachycardia, frequent premature ventricular contractions, and low left ventricular ejection fraction. Those PP patients with one or more risk factors will be categorized as '1.5' patients. Implant of an ICD/CRT-D will be left to the patient and/or physician's discretion. The primary endpoint will compare the appropriate ICD therapy rate between SP and 1.5 patients. The secondary endpoint compares mortality between 1.5 implanted and non-implanted patients.

Conclusion: The Improve SCA study will investigate a subset of PP patients, believed to be at similar risk of life-threatening ventricular arrhythmias as SP patients. Results may help clinicians identify and refer the highest risk PP patients for ICDs, help local societies expand guidelines to include PP of SCA utilizing ICDs, and provide additional geographical-relevant evidence to allow patients to make an informed decision whether to receive an ICD.

Trial Registration: NCT02099721.