Treatment of Ventricular Tachyarrhythmias and Indications for ICD implantation

Treatment with an Implantable Cardioverter Defibrillator (ICD) has become a mainstay in the prevention of sudden death, both as a primary and a secondary intervention. Although placement of an ICD can be lifesaving, placement entails modest risk and is expensive. Numerous studies have demonstrated clinical benefit of ICD implantation in patients who have survived sudden death (secondary prevention) and in those at increased risk of sudden death (primary prevention). The results of these studies combined with consensus guidelines have led our group to propose the following framework for the evaluation and treatment of patients. Intensive and ongoing efforts are designed to refine further the selection of patients most likely to benefit from ICD implantation.

ICDs should be placed in the following patients:

• The patient resuscitated from sudden death due to ventricular tachycardia (VT) or ventricular fibrillation (VF).
• The patient with depressed left ventricular function (LVEF <40%), nonsustained VT (NSVT) and inducible VT during electrophysiologic study.
• Patients with an ischemic cardiomyopathy and severely depressed left ventricular function (LVEF < 30%) and a QRS duration >120 msec. Cardiac function should be assessed more than 1 month after a myocardial infarction and 3 months after CABG.
• Patients with documented familial or inherited conditions associated with a high risk of life-threatening ventricular tachyarrhythmias, such as long QT syndrome (LQTS), Brugada syndrome, arrhythmogenic RV dysplasia (ARVD), or hypertrophic cardiomyopathy (HOCM).
• Syncope of undetermined origin with clinically relevant, hemodynamically significant sustained VT or VF induced at electrophysiological study when drug therapy is ineffective, not tolerated, or not preferred.
• Spontaneous sustained VT associated with structural heart disease.

ICDs are not indicated in the following patients:

• Patients in whom episodes of syncope, sudden death, ventricular tachycardia or ventricular fibrillation is secondary to a transient and readily reversible/avoidable phenomenon. An example is the patient who has ventricular tachycardia complicating a myocardial infarction (within 48 hours of the infarction).
• Spontaneous sustained VT occurring in a normal heart. These patients can be safely treated with beta-blockers, in some cases calcium channel blockers, and/or catheter-mediated radiofrequency ablation.
• Patients with incessant VT or VF: This requires intervention aimed at reversing the underlying cause of VT or VF. Placement of an ICD would result in repetitive cardioversions in such patients.
• Patients with terminal illness and a prognosis less than 6 months to one year.
• Patients with no history of spontaneous or inducible sustained ventricular arrhythmias undergoing CABG
• Patients with a psychiatric disorder that could be aggravated by device implantation or in whom adequate follow up cannot be assured.
• Patients with refractory Class IV congestive heart failure who are not candidates for heart transplantation.

Evaluation of the patient with non-sustained ventricular tachycardia

Patients in whom non-sustained VT has been identified require the following evaluation:

• Cardiac ultrasound (echocardiogram) to determine whether structural heart disease is present
• ·Evaluation to determine whether the patient is at risk for cardiac ischemia, (e.g. myocardial perfusion imaging or coronary angiography depending on the clinical circumstances)

Evaluation of the patient with coronary artery disease for their risk of sudden death

• Patients with documented coronary artery disease and left ventricular dysfunction (EF < 40%) should be evaluated with the use of Holter monitoring to define the presence and extent of non-sustained and/or sustained VT. Patients with non-sustained VT should be evaluated with an electrophysiologic study. Patients with sustained ventricular tachyarrhythmias should receive implantation of an ICD.

Evaluation of patients with non-ischemic cardiomyopathy

• Patients with non-ischemic cardiomyopathy and depressed left ventricular function (LVEF<40%) should be evaluated with Holter monitoring. Patients with sustained ventricular tachyarrhythmias should be treated with an ICD. Treatment of patients with non-sustained ventricular tachycardia is controversial. Limited data is available to guide therapy in this setting. Nevertheless a cautious approach has been advocated and Medicare reimbursement is provided for implantation of an ICD in patients with non-ischemic cardiomyopathy and inducible sustained ventricular tachyarrhythmias. Trials evaluating this patient group are forthcoming.

Treatment of the patient with a structurally normal heart and high grade ventricular ectopy (many PVC's, nonsustained and/or sustained VT)

• Patients with a structurally normal heart and VT have an excellent prognosis. Such patients can be managed safely with observation if asymptomatic or with beta-blockers to decrease symptoms. Those patients with frequent ventricular ectopy (>20 PVC's/hr) can be treated with beta-blockers to decrease symptoms and minimize the potential development of tachycardia-mediated cardiomyopathy. In some cases ectopy may decrease in response to treatment with verapamil. Ablation can be performed to eliminate symptoms in patients wishing to avoid drugs or in whom drug therapy is ineffective.