Prophylactic Implantation of Implantable Cardioverter-Defibrillator for Japanese Patients With Heart Failure
– Problem of “Underuse” –
論文ID: CJ-14-1394
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論文ID: CJ-14-1394
Landmark randomized clinical trials have demonstrated the survival benefits of prophylactic implantation of implantable cardioverter-defibrillator (ICD) for patients with chronic heart failure (CHF), especially with old myocardial infarction (Table),1–6 and prophylactic implantation of ICD decreased all-cause mortality and sudden cardiac death (SCD). However, the prevalence of both all-cause mortality and SCD is significantly lower in Japanese patients with LV dysfunction than in patients from Western countries (Table).7–10 Accordingly, the prophylactic use of ICD seems to be less effective than in Western countries.9
| Study | Study period | Patients | Diseases | NYHA class | Design | Groups | All-cause death | SCD | Predictors of SCD |
|---|---|---|---|---|---|---|---|---|---|
| Western | |||||||||
| MADIT-II1 | 1997–2001 | 1,232 | OMI+EF ≤35% | NA | RCT | ICD Conv. |
8.5% (ICD) 11.9% (conv.) |
3.8% (ICD) 10.0% (conv.) |
ND |
| SCD-HeFT2 | 1997–2001 | 2,521 | EF ≤35% Ischemic 52%, non-ischemic 48% |
II–III | RCT | ICD Amiodarone Placebo |
7.2% (ICD) 8.3% (amiodarone) 8.6% (placebo) |
NA | ND |
| VALIANT3 | 1998–2001 | 3,852 | OMI+EF ≤30% | I–IV | Multicenter observ. | ND | 14.80% | 10%/24.7 Mo | ND |
| DINAMIT4 | 1998–2003 | 676 | Recent MI+EF ≤35% | I–III | Randomized open | ICD (332 patients) Control (342 patients) |
7.9% (ICD) 6.9% (control) |
1.5% (ICD) 3.5% (control) |
ND |
| Zwolle5 | 1994–2004 | 2,544 | OMI+EF ≤35% | I–IV | Observ. | No prophylactic ICD implantation | 5.80% | 2.32% | ND |
| COMPANION6 | 2000–2002 | 1,520 | EF ≤35%+QRS ≥120 ms | III–IV | RCT | Drugs CRT-P CRT-D |
NA | NA | ND |
| Japan | |||||||||
| HIJAMI-II7 | 199 | OMI+EF ≤30% | NA | Multicenter observ. | NA | 33.2%/4.1 years | 5.1%/5 years | ND | |
| Tanno8 | 1997–2001 | 90 | OMI+EF ≤30% | I–IV | Single-center observ. | Survivors Non-survivors |
16.7%/37 months | 2.2%/3 years | ND |
| JCAD9 | 2000–2001 | 291 | OMI+EF ≤35% | NA | Multicenter observ. | NA | 7.15%/2.7 years | 2.38%/2.7 years | ND |
| CHART-210 | 2006–2010 | 2,778 (LVEF ≤35%; 315 patients) |
IHD or NIDCM+EF ≤35% or >35% | II–III | Multicenter observ. | LVEF ≤35% with NSVT LVEF ≤35% without NSVT LVEF >35% |
NA | SCD; 12 patients with EF ≤35% FAEs; 32 patients with EF ≤35%/3.2 years |
cAF or Dd ≥65 mm |
cAF, chronic atrial fibrillation; conv., conventional therapy; CRT, cardiac resynchronization therapy; EF, ejection fraction; FAEs, fatal arrhythmic events; ICD, implantable cardioverter-defibrillator; IHD, ischemic heart disease; LVEF, left ventricular ejection fraction; NA, not available; ND, not done; NIDCM, non-ischemic dilated cardiomyopathy; NSVT, non-sustained ventricular tachycardia; observ., observational cohort study; RCT, randomized controlled trial; SCD, sudden cardiac death.
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The Japanese Circulation Society guideline for non-pharmacotherapy of cardiac arrhythmias (JCS 2011)11 was partially extrapolated from guidelines and studies in Western countries, because evidences are lacking in Japan. Nor have the efficacy of prophylactic ICD implantation, appropriateness of JCS guideline (2011) for prophylactic ICD therapy, risk of SCD in patients with CHF and risk factors of SCD among CHF patients been fully elucidated in Japan.
In this issue of the Journal, Satake et al10 reported the usefulness of primary prevention of SCD in patients with CHF, and conclude that (1) the JCS guideline (2011)11 for prophylactic ICD implantation in CHF patients is validated, (2) prophylactic ICD is underused and (3) chronic atrial fibrillation (cAF) and left ventricular end-diastolic diameter (LVDd) ≥65 mm could be useful for risk stratification of SCD in CHF patients in Japan.
Satake et al10 divided CHF patients into 3 groups according to the JCS guideline (2011)11 and in those with class I or IIa indications of ICD implantation, fatal arrhythmic events occurred in 16.1% and 8.9%, respectively, during a 3.2-year follow-up. Although their sample size is small, these results may enhance the appropriateness of the JCS guideline (2011)11 in clinical practice.
In the United States, recent reports have suggested that ICDs may be significantly underused for primary and secondary preventions of SCD. In a population-based study in Oregon, with more generalizability than randomized controlled trials, only one-fifth of SCD patients in the community had been eligible for primary-prevention ICD. And among these SCD patients, only a small proportion (13%) received an ICD.12 In Get with the Guidelines Program,13 among patients who met indications of prophylactic ICD implantation of contemporary guidelines,14,15 35% received ICD therapy.16 In a population-based study in Canada, only 16% of patients eligible for primary-prevention of ICD (ischemic and non-ischemic cardiomyopathy) received an ICD.17 Other studies in the United States have also suggested underuse (30.7%) of ICD, even for secondary prevention in survivors of SCD.18 Satake et al10 also describe that in patients with EF ≤35% with or without NSVT, the proportion of prophylactic ICD implantation was only 34 of 315 patients (10.8%). These results suggest that the underuse of ICD remains a major problem in clinical practice and the reasons for underuse of ICD for eligible patients have not yet been elucidated. Probable reasons are sex and race differences, socioeconomic status and patients preference.16,19
What should be done to improve the use of ICD therapy for eligible patients? In IMPROVE-HF, multidisciplinary interventions resulted in a 27% increase in ICD implantation over 24 months.20 There might be multiple reasons why a decision is made to not implant an ICD; counseling and balanced education of physicians, patients and the public might increase the implantation of ICDs.19,21
Kadish et al reported that ICD prevented SCD in non-ischemic dilated cardiomyopathy, and they described the presence of AF as a risk factor.22 However, in JCARE-CARD, the presence of AF did not influence prognosis.23 In the population study in Oregon (Oregon Sudden Unexpected Death Study), the multivariate analysis without consideration of CHF found AF to be a significant predictor of SCD. However, when CHF was considered, the AF-SCD association was no longer significant.24 Although the results concerning the association between AF and SCD in CHF patients are divergent, Satake et al conclude that cAF is an independent predictor of fatal arrhythmic events.10 This matter should be confirmed by studies with larger samples.
The most powerful single independent risk factor of SCD is the EF in CHF patients. However, among patients with severely reduced EF, the risk factors of SCD are not yet clarified. In this setting, Satake et al’s conclusion that both cAF and Dd ≥65 mm are risk factors of SCD in patients with severely decreased EF10 is noteworthy for identifying high-risk patients.
To date, vigorous efforts have centered on assessing the risk of SCD, especially in high-risk groups.25 However, the well-known fact that there is an inverse relationship between the incidence of SCD and the absolute numbers of events is important to appreciate.26 To reduce the absolute number of SCD, public access defibrillators may have an important role. But, we cardiologists have the responsibility of managing of attending CHF patients.
Satake et al again spotlight the “underuse” problems of ICD.10 Their findings should be further investigated in a larger sample size and resolved by multidisciplinary approaches. We cardiologists, should make our best efforts to reduce the number of SCD cases. That is our obligation.
