AV nodal or infranodal disease causing intermittent third degree AV block and preexcitation with atrial fibrillation leading to ventricular fibrillation. These should be addressed appropriately with pacemaker, radiofrequency ablation or therapies other than ICD. Patients with syncope of undetermined etiology and without a documented or inducible sustained ventricular tachycardia are also not candidates for ICD and so are the ones with projected life expectancy less than 6-12 months. Improved technology associated with the implantation of an ICD as well as multiple studies showing dramatic success in preventing SCDs led to widespread acceptance of this new therapy. Among different antiarrythmic drugs, only beta blockers and amiodarone have been shown to be
of benefit in decreasing sudden death in survivors of myocardial infarction. While multiple trials have confirmed a clear mortality benefit of ICD over antiarrythmic drugs, they still have significant role in patients who do not want or are not candidates for an ICD therapy and also have adjunctive role in those who have frequent arrhythmia recurrences and device discharges. Primary prevention of SCA
poses a major challenge in terms of identification of the individuals at substantial risk from a huge pool of individuals without a prior event and to provide a safe and cost effective treatment to them. The current guidelines for ICD placement for primary prevention of SCA include: Patients with ischemic dilated cardiomyopathy (IDCM), prior MI, New
York Health Association (NYHA) Class II & III heart failure, left ventricular ejection fraction (LVEF) less than or equal to 35%. Patients with non-ischemic dilated cardiomyopathy (NIDCM) >3 months, NYHA Class II & III heart failure, LVEF less than or equal to 35% Patients who are at high risk of SCA due to genetic disorders such as long QT syndrome, Brugada syndrome, hypertrophic cardiomyopathy and arrhythmogenic right ventricular dysplasia.
SUMMARY SCA and SCD represent a catastrophic medical problem on an individual basis, a major public health concern on population basis, and a field of emerging interest globally. SCD is most commonly caused by a ventricular tachy-arrhythmia that degenerates into ventricular fibrillation. The acute management of SCA involves standard CPR protocols. Survivors of SCA need a thorough evaluation for identification and treatment of provoking factors, underlying structural or electrical abnormalities of the heart and evaluation of family members in selected cases. ICDs have proven to be effective in primary and secondary prevention of SCDs. Due consideration should be given to various factors including left ventricular ejection fraction (most important), etiology of underlying cardiomyopathy and its duration, timing of myocardial events or revascularization procedure, degree and duration of congestive heart failure, optimization of medical therapy, and electrophysiological consultation while selecting a patient for ICD therapy. ■
AH
REFERENCES References available on request (
magazine@informa.com)
AUTHOR INFO Associate Professor at the Department of Forensic Medicine, Srinivas Institute of Medical Sciences and Research Centre, Mangalore, India Internal Medicine Resident, University of Arkansas for Medical Sciences, Little Rock, AR, USA Consultant & Head at the Department of Emergency and Critical Care, Sri Gokulam Hospital and Research Institute, Salem, India
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