|Year : 2018 | Volume
| Issue : 2 | Page : 69-72
The current status of implantable cardioverter defibrillator for ischemic cardiomyopathy
Venkatakrishnan Ramakumar, Nitish Naik
Department of Cardiology, AIIMS, New Delhi, India
|Date of Web Publication||10-Sep-2018|
Dr. Venkatakrishnan Ramakumar
Department of Cardiology, AIIMS, New Delhi
Source of Support: None, Conflict of Interest: None
Implantable cardioverter defibrillator is the mainstay of sudden cardiac death prevention, but in contrast to its role in secondary prevention, its role in primary prevention is sometimes not so clear in many clinical contexts. When to implant after a myocardial infarction and at what ventricular function still remains debatable in many clinical situations.
Keywords: Coronary artery disease, left ventricular ejection fraction, sudden cardiac arrest
|How to cite this article:|
Ramakumar V, Naik N. The current status of implantable cardioverter defibrillator for ischemic cardiomyopathy. J Pract Cardiovasc Sci 2018;4:69-72
|How to cite this URL:|
Ramakumar V, Naik N. The current status of implantable cardioverter defibrillator for ischemic cardiomyopathy. J Pract Cardiovasc Sci [serial online] 2018 [cited 2019 Jan 19];4:69-72. Available from: http://www.j-pcs.org/text.asp?2018/4/2/69/240965
| Introduction|| |
In the previous article, we had highlighted the use of implantable cardioverter defibrillators (ICDs) in the context of nonischemic cardiomyopathy. In this edition, we review the use of ICDs for ischemic cardiomyopathy and its merits and demerits.
Coronary artery disease (CAD) is a major risk factor for sudden cardiac arrest (SCA), especially when left ventricular ejection fraction (LVEF) is reduced. A number of randomized controlled trials (RCTs) in patients with ischemic cardiomyopathy have demonstrated that ICD implantation results in mortality reduction over the long term.,
| Secondary Prevention|| |
American College of Cardiology/American Heart Association/Heart Rhythm Society guidelines for implantable cardioverter defibrillator as secondary prevention
- In patients with ischemic heart disease (IHD), who either survive SCA due to ventricular tachycardia (VT)/ventricular fibrillation (VF) or experience hemodynamically unstable VT (LOE: B-R) or stable VT (LOE: BNR) not due to reversible causes, an ICD is recommended if meaningful survival >1 year is expected (Class I)
Comments: In the AVID trial, there was an improved overall survival with an ICD compared with antiarrhythmic drug therapy in patients who survived SCA or with hemodynamically unstable VT, with a 2-year relative risk reduction in mortality of 27%. Another trial, the CIDS study, showed a statistically insignificant result trend toward the benefit of ICD over antiarrhythmic drug therapy. The trial was prematurely terminated after the results of the AVID trial were published. A subsequent meta-analysis of the AVID, CIDS, and the CASH studies revealed a 28% relative risk reduction in all-cause mortality and a 50% reduction in arrhythmic deaths. Survival was also extended by an average 4.4 months over 6 years. The benefit was derived predominantly by patients with an ejection fraction (EF) <35%. Another treatment option for well-tolerated ventricular arrhythmias in IHD is ablation. A recent trial had shown that in patients with EF >30% and sustained monomorphic VT that was well tolerated, of whom a majority had IHD, ablation without a backup ICD resulted in low rate of arrhythmic death. Recurrences of ventricular arrhythmia were not fatal and well tolerated.
- In patients with IHD and unexplained syncope who have inducible sustained monomorphic VT on electrophysiological study (EPS), an ICD is recommended if meaningful survival of >1 year is expected (Class I).
Comments: An oft-neglected subset of patients are those with syncope or near syncope with IHD. A landmark study of patients with unexplained syncope who underwent an EPS identified nearly half of the patients as having a positive finding on EPS. Subsequently, these patients had a four-fold increase in mortality over 3 years and tend to have a worse prognosis than those without a positive EPS. The American College of Cardiology (ACC)/American Heart Association(AHA)/Heart Rhythm Society (HRS) guidelines currently recommend an EPS for patients with ischemic cardiomyopathy and a history of cardiac syncope with EF >35% for further risk stratification. Patients with ischemic cardiomyopathy with an EF <35% and a history of cardiac syncope would automatically qualify for an ICD.
In terms of cost-effectiveness, the incremental cost-effectiveness was anywhere between $64,000 and $100,000 per year of life added,,,, which is considered in the intermediate range by the ACC/AHA cost/value statement.
| Primary Prevention|| |
Multiple RCTs over the last two decades have ratified the clear-cut benefit of ICDs in IHD for primary prevention. ICDs currently represent one of the best options for SCA prevention in IHD patients with reduced EF.
American College of Cardiology/American Heart Association/Heart Rhythm Society guidelines for implantable cardioverter defibrillator as primary prevention
- In patients with LVEF of 35% or less that is due to IHD who are at least 40 days post-myocardial infarction (MI) and at least 90 days postrevascularization, and with NYHA Class II or III heart failure (HF) despite guideline-directed medical therapy (GDMT), an ICD is recommended if meaningful survival of >1 year is expected (Class I)
- In patients with LVEF of 30% or less that is due to IHD who are at least 40 days post-MI and at least 90 days postrevascularization, and with NYHA Class I HF despite GDMT, an ICD is recommended if meaningful survival of >1 year is expected (Class I)
Comments: The epoch MADIT II trial demonstrated that in patients with a prior MI and a LVEF of 30% or less, there was an all-cause mortality reduction of 31% over and above medical therapy over an average of 20 months' observational period. In addition, one-third of patients in the MADIT-II trial had Class I symptoms and derived significant benefit from an ICD. The other major trial to establish the role of ICDs was SCD-HeFT which showed a 23% mortality benefit over amiodarone or placebo in patients with HF with reduced EF of <35%, in Class II or III NYHA, just about half of whom were patients with IHD. The survival benefit observed in SCD-HeFT and MADIT-II has led to the advent of ICDs being offered to patients with IHD and reduced EF, in Class II–III HF and a subsequent Class I indication.,
Patients in Class IV HF represent somewhat of an ambiguity. The COMPANION trial did include patients in ambulatory Class IV and demonstrated a trend toward benefit with a CRT-D. An ICD alone in these patients is not recommended in light of an expected survival of <1 year.
- In patients with nonsustained VT (NSVT) due to prior MI, LVEF of 40% or less and inducible sustained VT or VF at EPS, an ICD is recommended if meaningful survival of >1 year is expected (Class I).
Comments: The MUSTT demonstrated that in patients with prior MI, NSVT, and reduced LVEF with inducible VT, an ICD improved survival in patients in whom an anti-arrhythmic did not suppress the VT. This has led to the recommendation that patients with a prior MI and an EF <40% with NSVT should have an EPS and an ICD be recommended if an inducible VT is present.
| Timing of Implantable Cardioverter Defibrillator Insertion|| |
The DINAMIT and IRIS trials had demonstrated that ICD insertion within 40 days of an MI provided no survival benefit and a potential increase in deaths. One possible explanation is that the mortality risk from nonarrhythmic causes and mechanical complications could result in an apparent increase in event rates. Furthermore, the stress of the ICD insertion and postprocedural complications could result in adverse events themselves., In a recent study, a large percentage of patients with stable CAD who underwent successful revascularization for significant obstruction had an increase in EF after 3 months, precluding the need for an ICD. Recent data from PREDICTS revealed a high rate of eventual LVEF recovery among survivors of acute MI with an initial LVEF ≤35%. In patients undergoing revascularization, it is appropriate to wait for 90 days postprocedure and reassess EF to aid decision-making about the insertion of primary prevention of ICD.
The incremental cost-effectiveness ratios were generally <$50,000 per year of life added by an ICD, which provides high value according to the benchmarks set. The value provided by an ICD was consistently high when life expectancy was projected to increase by >1.4 years.
| Some Other Unclear Areas|| |
It is unclear whether the benefit extends to very elderly population of patients above 75 years, though in some of the studies where the patients included were above 75 years of age, the benefit was still seen at this age. Comorbidities such as renal failure can also influence since they have an independent influence on the mortality and an ICD may not exert an influence.
| Some Food for Thought|| |
Can we just ablate for secondary prevention?
One center reported its experience of using a step-wise approach of using radiofrequency ablation as the primary modality for the treatment of VT in patients with structural heart disease and evaluating long-term outcomes. In this study, about 45 patients with a mean LVEF of 40% underwent radiofrequency ablation of VT. Acute success was achieved in 40/45 patients (89%) with no VT being inducible at the end of the ablation procedure; of the remaining five patients, a repeat ablation procedure was successful in eliminating the recurrence of VT, while the other four received an ICD. In the forty patients in whom acute success was achieved, a close clinical follow-up was maintained. In three of these patients, VT recurred and despite a successful repeat ablation procedure, VT was still inducible 3 months after the second procedure – all three of these patients received an ICD. Among the 37 remaining patients, repeat EPS was done at 3 months to assess for re-inducibility of VT (of all anti-arrhythmic drugs including amiodarone) – 13 patients had inducible VT and 12 of these patients required an ICD as the VT was either poorly tolerated (5 patients) or recurred despite one or two additional ablation procedures. In the 23 patients who had a negative EPS at 3 months, only one patient had a recurrence of VT again which also responded to a repeat ablation procedure. After a median follow-up of 45 months, there were no significant differences in mortality between the two groups. Thus. though ablation helped in preventing recurrences of VT, it required multiple procedures and frequent EPS to assess for the risk of recurrences.
| Data on Implantable Cardioverter Defibrillators from India|| |
Data from the Indian Society of Electrocardiography and the Indian HRS show that single-chamber ICD is most frequent (65%). Primary prophylaxis use of ICD is seen in 52.5% of patients. The commonest etiology for ICD use was CAD (58.5%), followed by idiopathic dilated cardiomyopathy (31.8%), and LVEF was <0.35 in 72.5% of patients.
| Conclusion|| |
ICDs have proven to be of significant overall and arrhythmic mortality benefit over and above medical therapy in multiple subsets of patients with ischemic cardiomyopathy. They have proven to be consistently beneficial and cost-effective given that the patient is expected to survive more than 1 year. There is strong evidence of benefit for both primary and secondary prevention once treatable causes are ruled out.
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Conflicts of interest
There are no conflicts of interest.
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