Implantable Cardioverter Defibrillator Indications
General Principles
Current indications for implantable cardioverter defibrillator (ICD) therapy are derived from the inclusion criteria of several pivotal clinical trials. Each of these studies demonstrated mortality benefit with ICD therapy in a specific patient cohort (see Table 14-1). Applying these results to individual patients, however, requires not only a knowledge of these data, but also an appreciation for the unique clinical features of ICD therapy (see Table 14-2).
Recommendations regarding patient selection for ICD therapy were included in the 2006 American College of Cardiology/American Heart Association/European Society of Cardiology (ACC/AHA/ESC) guidelines for the management of ventricular arrhythmias and the prevention of sudden cardiac death (SCD). Although these recommendations provide the framework for a standardized approach to ICD utilization, decisions regarding ICD implantation are unique to each patient.
Clinical Trials
Clinical trials have definitively established that ICD therapy dramatically reduces the risk of arrhythmic death, and that in specific patient cohorts this reduced rate of arrhythmic death results in improved overall survival. Since the publications of Multicenter Automatic Defibrillator Implantation
Trial (MADIT) (primary prevention) and antiarrhythmics versus implantable defibrillators (AVID) (secondary prevention) in 1996 and 1997 respectively, ICD indications have evolved rapidly.
Trial (MADIT) (primary prevention) and antiarrhythmics versus implantable defibrillators (AVID) (secondary prevention) in 1996 and 1997 respectively, ICD indications have evolved rapidly.
TABLE 14-1 Studies Demonstrating Mortality Benefit with Implantable Cardioverter Defibrillator (ICD) Therapy in a Specific Patient Cohort
| Trial | Patient Population | Inclusion Criteria | Resultsa |
| a Risk reduction for ICD versus control, except for MUSTT (see noteb). Results are statistically significant unless noted. b MUSTT was not a randomized comparison of ICD therapy to AADs or conventional medical therapy. Rather it compared EPS-guided therapy (AAD or ICD) to conventional medical therapy. There was a nonsignificant improvement in survival among patients assigned to EPS guided therapy (6% ARR) that was entirely due to substantially reduced mortality in patients treated with an ICD. Patients in the EPS-guided arm who were treated with AADs had outcomes similar to the control arm (conventional medical therapy without EPS). AVID, antiarrhythmics versus implantable defibrillators; CASH, Cardiac Arrest Study Hamburg; CIDS, Canadian Implantable Defibrillator Study; MUSTT, Multicenter Unsustained Tachycardia Trial; MADIT, Multicenter Automatic Defibrillator Implantation Trial; SCD–HeFT, Sudden Cardiac Death in Heart Failure Trial; COMPANION, Comparison of Medical Therapy, Pacing,and Defibrillation in Heart Failure; VF, ventricular fibrillation; VT, ventricular tachycardia; LVEF, left ventricular ejection fraction; bpm, beats per minute; MI, myocardial infarction; NSVT, nonsustained ventricular tachycardia; EPS, electrophysiologic study; HF, heart failure; NYHA, New York Heart Association; CRT, cardiac resynchronization therapy; AAD, antiarrhythmic drug; ARR, absolute risk reduction; RRR, relative risk reduction. | |||
| AVID (1997) | Secondary | Resuscitated VF; symptomatic VT requiring cardioversion with an LVEF <40% | 31% RRR, 11% ARR in overall mortality at 36 mo compared to class III antiarrhythmics (most commonly amiodarone) |
| CASH (2000) | Secondary | Resuscitated SCA | 23% RRR, 8% ARR (nonsignificant) in overall mortality at 57 mo compared to amiodarone or metoprolol |
| CIDS (2000) | Secondary | VF; out-of-hospital SCA requiring defibrillation or cardioversion; sustained VT causing syncope; VT (>150 bpm) causing presyncope or angina, with an LVEF <35%; syncope with subsequent spontaneous or induced monomorphic VT | 20% annual RRR; 2% annual ARR (nonsignificant) in overall mortality compared to amiodarone |
| MUSTT (1999) | Primary | LVEF ≤40, prior MI, NSVT, (+) EPS (inducible VT) | a50% RRR, 24% ARR in overall mortality at 5 yr for ICD compared to conventional medical therapy |
| MADIT (1996) | Primary | LVEF ≤35, prior MI, NSVT, (+) EPS (inducible monomorphic VT that was not suppressible with procainamide) | 54% RRR and 23% ARR for overall mortality at 27 mo compared to antiarrhythmic therapy |
| MADIT II (2002) | Primary | Prior MI, LVEF ≤30 | 35% RRR, 5.6% ARR in overall mortality at 20 mo compared to conventional medical therapy |
| SCD-HeFT (2005) | Primary | LVEF ≤35, NYHA class II or III HF (cardiomyopathy was ischemic or nonischemic in 52% and 48% of patients, respectively) | 23% RRR, 7% ARR in overall mortality at 5 yr compared to conventional medical therapy |
| COMPANION (2004) | Primary | LVEF ≤35, NYHA class III or IV HF, and QRS >120 msec (Patients were randomly assigned to standard medical therapy, CRT alone, or CRT with an ICD) | 36% RRR, 7% ARR in overall mortality at 12 mo for CRT plus an ICD compared to conventional medical therapy |
TABLE 14-2 Complications Associated with Implantable Cardioverter Defibrillator (ICD) Therapy
| VT, ventricular tachycardia. | |
| Device-related issues | |
| Implantation risk (standard transvenous approach in a typical patient) | The reported incidence of serious complications (e.g., serious infection, cardiac perforation, pneumothorax, or bleeding/hematoma) varies from ∼1%–7%. Patient-specific issues (e.g., complicated access or increased infectious risk) can increase these risks |
| Long-term device-related risks | Infection/erosion requiring explantation Inappropriate shocks |
| Device or lead failure | |
| Patient-specific concerns | |
| Competing mortality Goals of care and quality of life | Many ICD candidates have substantial comborbidities in addition to advanced cardiac disease; therefore, the benefit of a reduced risk of arrhythmic death may be mitigated by an increased incidence of nonarrhythmic death (e.g., heart failure) |
| Infectious risks | Conditions associated with an increased incidence of infection and bacteremia (e.g., hemodialysis, chronic immunosuppression), may increase the long-term risk of device infection. |
General Concerns Related to Implantable Cardioverter Defibrillator Therapy
Once it is recognized that a patient’s clinical profile justifies consideration of an ICD, a number of additional issues also need to be considered (Table 14-2). Because the benefit of ICD therapy is straightforward (improved survival), these additional issues are largely factors that could mitigate the expected benefit from and/or the patient’s desire for a device. All cardiologists who refer patients for consideration of ICD implantation should have at least a general knowledge of these issues. Physicians directly responsible for recommending
ICD implantation should have a firm understanding of each of these concerns and be comfortable discussing them with prospective patients with ICD and their families.
ICD implantation should have a firm understanding of each of these concerns and be comfortable discussing them with prospective patients with ICD and their families.
For most ICD candidates, the potential mortality benefit of the device outweighs these concerns. It is not possible to define specific circumstances in which competing mortality or reduced quality of life make ICD therapy inappropriate. However, the ACC/AHA/ESC guidelines addressed this issue by including in all statements recommending ICD implantation the stipulation that the patient should “have reasonable expectation of survival with good functional status for more than one year.” Ultimately, it is the responsibility of the physician recommending ICD therapy to individualize this assessment and decision process, ensuring that each patient makes a well-informed decision.
Secondary Prevention
Patients who survive sudden cardiac arrest (SCA) or symptomatic ventricular tachycardia (VT) are at an increased risk for recurrent malignant arrhythmias and SCD. Most such patients should be treated with an ICD, regardless of the nature of underlying heart disease (see Table 14-3).
TABLE 14-3 Treatment with an Implantable Convertible Defibrillator (ICD)
| SCA, superior cerebellar artery; SOB, shortness of breath; NSTEMI, non-ST segment elevation; STEMI, ST-segment elevation; RV, right ventricular. |
| Events for which an ICD is indicated for secondary prevention of SCD |
| Resuscitated SCA due to ventricular fibrillation or ventricular tachycardia (VT) |
| Symptomatic ventricular tachycardia (e.g., syncope, presyncope, chest pain, SOB), particularly in patients with reduced systolic function |
| Exceptions |
| Reversible triggers, most commonly acute ischemia (documented NSTEMI, or STEMI within 48–72 h of the arrhythmic event) |
| Limited life expectancy (e.g., <1-2 yr) or poor quality of life |
| Asymptomatic/hemodynamically tolerated VT in patients with structurally normal hearts (e.g., RV outflow tract VT) |
The rationale for this approach is based on the results of three randomized trials (AVID, Cardiac Arrest Study Hamburg [CASH], and Canadian Implantable Defibrillator Study [CIDS]) that compared the efficacy of the ICD to that of antiarrhythmic drugs (AADs), most commonly amiodarone (Table 14-1). A meta-analysis that included these three trials and a fourth
smaller trial showed that ICD therapy resulted in relative and absolute mortality reductions of 25% and 7%, respectively.
smaller trial showed that ICD therapy resulted in relative and absolute mortality reductions of 25% and 7%, respectively.
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