A 55-year-old man with past medical history significant for hypertension (HTN), hyperlipidemia, and type 2 diabetes mellitus, was admitted to the coronary care unit 3 months ago with non-ST-elevation myocardial infarction (NSTEMI). Coronary angiography then revealed 95% narrowing in the proximal left anterior descending coronary artery. He underwent successful percutaneous coronary intervention and stent placement with excellent angiographic results and resolution of his symptoms. His left ventricular ejection fraction (LVEF) was 25% by left ventriculography performed at the time of the intervention. He was established on dual antiplatelet therapy, statin, and guideline-directed medical therapy for heart failure (HF). Beta blocker and angiotensin-converting enzyme (ACE) inhibitor were gradually titrated to the maximally tolerated doses during the next few months after discharge. He returned for his 3-month post discharge visit reporting no angina. An echocardiogram in the office revealed an LVEF of 30%. His 12-lead electrocardiogram (ECG) showed normal sinus rhythm (NSR), normal intervals, old septal infarct, and QRS of 110 ms. His medications include carvedilol 25 mg by mouth twice daily, lisinopril 10 mg by mouth twice daily, spironolactone 25 mg by mouth once a day, aspirin 81 mg by mouth once a day, clopidogril 75 mg by mouth once a day, and atorvastatin 80 mg by mouth before bed. He resides in NYHA functional class II. What is the single most important therapy you recommend to improve his survival?
Sudden cardiac death (SCD) is a major public health problem and the cause of death in approximately 500,000 patients every year in the United States. An implantable cardioverter defibrillator (ICD) is a device-based therapy designed to detect and treat lethal ventricular arrhythmias and has shown to decrease mortality in high-risk populations, including those who survived prior cardiac arrests. Among patients without prior history of cardiac arrest or sustained ventricular arrhythmias, the LVEF of 35% or less has been identified as the single best predictor of SCD risks. Several randomized clinical trials have enrolled patients with low ejection fraction, various clinical HF profiles without history of cardiac arrest or sustained ventricular arrhythmias, and shown survival benefits from prophylactic ICD implantation when compared to conventional therapy alone. In this chapter we will discuss the risks of SCD among HF patients, major components and basic functions of the intravenous ICD system, the ICD implant procedure, and possible complications. We will also discuss the clinical trials that led to the introduction of ICD as a lifesaving therapy in certain patient populations and highlight recent indications and contraindications of ICD therapy according to the most recent guidelines.
IMPLANTABLE CARDIOVERTER DEFIBRILLATORS
ICDs are surgically implanted devices with the ability to continuously monitor cardiac rhythm, as well as detect and terminate life-threatening arrhythmias. The ICD system consists of a pulse generator that is implanted subcutaneously in the subpectoral fascia medial to the deltopectoral groove and connected to a single ventricular lead (single-chamber ICD) or ...