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 Table of Contents  
REVIEW ARTICLE
Year : 2018  |  Volume : 4  |  Issue : 1  |  Page : 6-9

Current status of the ICD in nonischemic cardiomyopathy


Department of Cardiology, AIIMS, New Delhi, India

Date of Web Publication4-May-2018

Correspondence Address:
Dr. Venkatakrishnan Ramakumar
Department of Cardiology, AIIMS, New Delhi
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jpcs.jpcs_16_18

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  Abstract 

Risk stratification of patients before considering implantable cardioverter defibrillator (ICD) therapy is important for targeting therapy. Recommendations for selecting the optimal patients for ICD therapy are based on major trials. For patients with nonischemic dilated cardiomyopathy, left ventricular ejection fraction (LVEF) ≤35%, and associated heart failure (HF) with New York Heart Association (NYHA) functional Class II or III status, ICD therapy for primary prevention of sudden cardiac death (SCD) is recommended. ICDs are effective at reducing total mortality and mortality from SCD, although the benefits of an ICD on total mortality may be diminished in the setting of guideline-directed optimal medical therapy and cardiac resynchronization therapy. For patients with an LVEF ≤35%, HF with NYHA functional Class III or IV status, and a QRS duration ≥120 milliseconds, biventricular pacing combined with an ICD is recommended.

Keywords: Dilated cardiomyopathy, guidelines, implantable cardioverter defibrillator, implantable defibrillator, India, nonischemic cardiomyopathy


How to cite this article:
Ramakumar V, Naik N. Current status of the ICD in nonischemic cardiomyopathy. J Pract Cardiovasc Sci 2018;4:6-9

How to cite this URL:
Ramakumar V, Naik N. Current status of the ICD in nonischemic cardiomyopathy. J Pract Cardiovasc Sci [serial online] 2018 [cited 2018 Sep 21];4:6-9. Available from: http://www.j-pcs.org/text.asp?2018/4/1/6/231930


  Introduction Top


Implantable cardioverter defibrillator (ICD) therapy prevents sudden death and prolongs life in patients at high risk of sudden arrhythmic death, provided that the patient does not suffer from other conditions that limit life expectancy to <1 year.[1],[2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14] With respect to sudden cardiac death (SCD), the ICD has been consistently shown to provide a mortality benefit, an area where antiarrhythmic drugs have not been useful. The benefit provided by an ICD can extend well beyond the initial few years. Long-term studies have demonstrated the efficacy of ICDs over a mean follow-up of 8 years.[2] However, ICDs do not come without their caveats and pitfalls. In recent times, the role of the ICD in nonischemic dilated cardiomyopathy (DCM) has been questioned, particularly in patients already having cardiac resynchronization therapy (CRT). Defibrillators may cause complications, including inappropriate shocks, which are especially frequent in children.[3] Furthermore, a clear gap exists between guidelines and clinical practices in several countries. A limiting factor in the use of an ICD is its high upfront costs. In any patient, the management includes appropriate management of arrhythmias and appropriate use of an ICD.

Management of tachycardia

  • In a patient who is having recurrent ventricular arrhythmias and has nonischemic cardiomyopathy, treatment to terminate the tachycardia is required
  • For sustained monomorphic ventricular tachycardia (VT), amiodarone or sotalol is tried first and then catheter ablation can be considered
  • For polymorphic VT or ventricular fibrillation (VF):
    • We need to try and correct reversible causes such as drug and electrolyte imbalance and ischemia and also rule out QT prolongation
    • If no cause is found, the first drug tried is amiodarone, and then beta-blockers or lidocaine are tried
    • If the VT persists then catheter ablation is tried, and if that also fails, the last option is autonomic modulation by sympathetic denervation.



  Prevention of Sudden Cardiac Death: the Guidelines Top


Secondary prevention: (ACC/AHA/HRS 2017 guidelines)

Class I

In patients who either survive sudden cardiac arrest due to VT/VF, or experience hemodynamically unstable VT, if survival more than 1 year is expected.

Class IIa

Syncope suspected to be due to ventricular arrhythmia, ICD should be implanted or an EPS should be done for risk stratification if life expectation is more than 1 year.

Primary prevention

Class I

In patients with left ventricular ejection fraction (LVEF) of 35% or less and with New York Heart Association (NYHA) Class II or III heart failure (HF) despite GDMT for at least 3 months, if life expectancy is more than 1 year.

Class II A

In patients with NICM due to a lamin A/C mutation who have 2 or more risk factors (NSVT, LVEF <45%, nonmissense mutation, and male sex).


  Discussion of the Evidence Behind the Guidelines and the New Data Top


Patients with DCM should be on optimal medical therapy for at least 3 months with persistent EF <35% before a decision of ICD is taken unless there is an indication for secondary prevention. Initially, the cardiomyopathy trial (CAT; 104 patients with recent onset [≤9 months] nonischemic DCM and an LVEF ≤30%; ICD vs. medical therapy) and the amiodarone versus ICD trial (AMIOVIRT; 103 patients with nonischemic DCM, LVEF ≤35%, Class I to III HF, and asymptomatic NSVT; randomized to ICD vs. amiodarone therapy) showed no significant benefit of ICD therapy in the primary endpoint of all-cause mortality.[8] In the CAT study, cumulative survival was not significantly different between the two groups (93% and 80% in the control group vs. 92% and 86% in the ICD group after 2 and 4 years, respectively). In the AMIOVIRT study, the percent of patients surviving at 1 year (90% vs. 96%) and 3 years (88% vs. 87%) in the amiodarone and ICD groups, respectively, were not statistically different.[15],[16],[17]

The primary prevention guideline[4-30] recommendations in DCM patients are based on the results of two randomized controlled trials (the Defibrillators in Non-Ischemic Cardiomyopathy Treatment Evaluation [DEFINITE] and the SCD in HF Trial [SCD-HeFT]). The trials showed a trend toward a reduction of mortality from any cause in the ICD arm.

Subsequently, the DANISH trial has raised questions on putting ICDs in all such patients.

The DANISH trial

The Danish study to assess the efficacy of ICDs in Patients with Non-Ischemic Systolic HF on Mortality (DANISH) randomly assigned 1116 patients with symptomatic systolic HF (LVEF ≤35%) not caused by ischemic heart disease to an ICD with guideline-directed optimal medical therapy or medical therapy alone.[31] Both groups received optimal medical therapy (97% on an ACE-I or angiotensin II receptor blockers, 92% on a beta blocker, 58% on a mineralocorticoid antagonist) and 58% of both groups receiving CRT. Over a median follow-up of 5.6 years, there was no significant difference in the primary outcome of total mortality (21.6% in the ICD group compared with 23.4% in the group without an ICD), a significant reduction in the secondary outcome of SCD in the group receiving ICDs (4.3%) compared with 8.2% in the no ICD group. Compared with prior primary prevention ICD trials, the overall mortality rate of patients in the DANISH trial was low, due to improved medical therapy for HF and the use of CRT, which was not available during the older primary prevention trials. In a subgroup analysis, there was an overall mortality benefit in the age group <70 years. According to the DANISH results, in patients with nonischemic HF and EF ≤35%, treated with current therapy, the number needed to treat to prevent one death in a follow-up of 5.6 years was very high (56 patients).

Status after the DANISH trial

In a 2004 meta-analysis of 1854 patients with nonischemic cardiomyopathy from five ICD primary prevention trials (CAT, AMIOVIRT, DEFINITE, SCD-HeFT, and COMPANION), ICD recipients had a significant reduction in all-cause mortality compared with medical therapy alone. Based on the averaged control group mortality rate (7%/year), the absolute risk reduction was approximately 2% per year.

In updated meta-analyses that have been published that include patients from the DANISH trial, the meta-analyses demonstrate a significant benefit of the ICD on all-cause mortality in patients with nonischemic cardiomyopathy. When only patients who also received CRT in the COMPANION and DANISH trials were analyzed, there was a nonsignificant trend toward reduction in all-cause mortality among patients with an ICD. In summary, while a significant reduction in SCD was noted in patients receiving an ICD, the DANISH trial demonstrated no significant reduction in total mortality from ICD therapy compared with standard therapy (medical therapy with CRT when indicated) for patients with symptomatic systolic HF not caused by coronary artery disease.[32],[33],[34],[35],[36],[37],[38]

Identification of patients who will not benefit from implantable cardioverter defibrillator in spite of indications is also important. Some patients will not survive due to comorbidities

In a study of ICDs for primary prevention, several predictors of increased all-cause mortality, denoted by the acronym “SHOCKED,” were identified: 75 years of age or older, HF with NYHA Class III, out of rhythm from atrial fibrillation, chronic obstructive pulmonary disease, kidney disease, chronic, EF (LVEF) 20% or lower, and diabetes mellitus. These markers may allow for the identification of patients at highest risk of nonarrhythmic mortality following ICD implantation and so they would derive little or no benefit from the ICD.[21]

Class IV heart failure

Once Class IV HF is refractory, life expectancy is generally <1 year unless cardiac transplantation is performed. The role of ICD therapy for primary prevention of SCD in patients with NYHA Class IV HF with a narrow QRS complex has not been studied. Given these considerations, for ambulatory patients with NYHA Class IV HF, a LVEF ≤35% and a narrow QRS complex, who are awaiting cardiac transplantation outside the hospital, ICD implantation may be considered as a bridge to transplantation. There are very limited data to support this recommendation.

Implantable cardioverter defibrillator use in India

Single-chamber ICDs are used most frequently (65%) used for the prevention of SCD from ventricular tachyarrhythmias. Primary prophylaxis use of ICD was seen in 52.5%, for CAD (58.5%), DCM (31.8%), hypertrophic cardiomyopathy (6%), and channelopathies (3.7%).[39]

Use of newer markers may reclassify patients?
  • EF < 35%
    • If magnetic resonance imaging (MRI) late gadolinium enhancement (LGE) is negative, no familial DCM > could be lower risk
  • EF 35%–49%
    • MRI positive for fibrosis on MRI or familial DCM or SCD, Gene mutation > suggests higher risk and may benefit from ICD.[38]


Myocardial fibrosis on cardiac magnetic resonance

The presence of myocardial fibrosis, identified by LGE on cardiac MRI, has been associated with a greater risk of ventricular arrhythmias or SCD in patients with DCM. A 2017 meta-analysis assessed the relationship between LGE and ventricular arrhythmias in patients with nonischemic DCM.[40] Mean LVEF in the various cohorts ranged from 20% to 43% and LGE was identified in 44%. Over a mean follow-up of 3 years, the primary end-point (sustained ventricular arrhythmia, appropriate ICD intervention, or SCD) occurred in 350 patients, including 21% of patients with LGE (compared with 4.7% of patients without LGE). Notably, subgroup analysis revealed that LGE was able to risk stratify patients at all levels of LVEF (both above and below 35%).


  Summary and Recommendations Top


ICDs are useful in the treatment of ventricular tachyarrhythmias and prevention of SCD, but risk stratification of patients before considering ICD therapy is important for targeting therapy to patients at highest risk of SCD. Recommendations for selecting the optimal patients for ICD therapy are based largely on the entry criteria in the major trials. Before recommending ICD therapy for the primary prevention of SCD, there should be a expectation of survival with a good functional status for at least 1 year. For patients with nonischemic DCM, LVEF ≤35%, and associated HF with NYHA functional Class II or III status, ICD therapy for primary prevention of SCD is recommended rather than optimal medical therapy alone. ICDs are effective at reducing total mortality and mortality from SCD, although the benefits of an ICD on total mortality may be diminished in the setting of guideline-directed optimal medical therapy and CRT. For patients with an LVEF ≤35%, HF with NYHA functional Class III or IV status, and a QRS duration ≥120 msonds, a combined CRT-D device (biventricular pacing combined with an ICD) rather than an ICD alone is recommended.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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