Temporal and geographical trends in indications for implantation of cardiac defibrillators in Europe 1993-1998. Medtronic ICD System Investigators

Temporal trends in patient characteristics and outcomes among Medicare beneficiaries undergoing primary prevention implantable cardioverter-defibrillator placement in the United States, 2006-2010. Results from the National Cardiovascular Data Registry's Implantable Cardioverter-Defibrillator Registry

BACKGROUND

Contemporary patterns of use and outcomes of implantable cardioverter-defibrillators (ICDs) in community practice settings are not well characterized. We assessed temporal trends in patient characteristics and outcomes among older patients undergoing primary prevention ICD therapy in US hospitals between 2006 and 2010.

METHODS AND RESULTS

Using the National Cardiovascular Data Registry's ICD Registry, we identified Medicare fee-for-service beneficiaries aged ≥65 years and older with left ventricular ejection fraction ≤35% who underwent primary prevention ICD implantation, including those receiving concomitant cardiac resynchronization therapy between 2006 and 2010 and could be matched to Medicare claims. Outcomes were mortality and hospitalization (all-cause and heart failure) at 180 days, and device-related complications. We used multivariable hierarchical logistic regression to assess temporal trends in outcomes accounting for changes in patient, physician, and hospital characteristics. The cohort included 117 100 patients. Between 2006 and 2010, only modest changes in patient characteristics were noted. Fewer single lead devices and more cardiac resynchronization therapy devices were used over time. Between 2006 and 2010, there were significant improvements in all outcomes, including 6-month all cause mortality (7.1% in 2006, 6.5% 2010; adjusted odds ratio, 0.88; 95% confidence interval, 0.82-0.95), 6-month rehospitalization (36.3% in 2006, 33.7% in 2010; adjusted odds ratio, 0.87; 95% confidence interval, 0.83-0.91), and device-related complications (5.8% in 2006, 4.8% in 2010; adjusted odds ratio, 0.80; 95% confidence interval, 0.74-0.88).

CONCLUSIONS

The clinical characteristics of this national population of Medicare patients undergoing primary prevention ICD implantation were stable between 2006 and 2010. Simultaneous improvements in outcomes suggest meaningful advances in the care for this patient population.

Scaling Characteristics of Heart Rate Time Series Before the Onset of Ventricular Tachycardia

Ventricular tachycardia (VT) provokes sudden cardiac death (SCD), which is a major cause of mortality in developed countries. Implantable cardioverter-defibrillators (ICDs) are an efficient therapy for SCD prevention. In this study we analyze heart rate variability (HRV) in data stored by ICDs. In 29 patients exhibiting VT episodes, the last 1000 normal beat-to-beat intervals are analyzed and compared to an individually acquired control time series (CON). HRV analysis is performed with standard parameters of time and frequency domain as suggested by the HRV Task Force. For scaling analyses of heart rate time series, the fractal dimension is analysed, applying Higuchi's algorithm (HFD). Furthermore, detrended fluctuation analysis (DFA) is performed. None of the standard HRV parameters shows significant differences between CON and VT. Before the onset of VT, the scaling characteristics by means of HFD and DFA are significantly changed. In conclusion, scaling analysis reveals changes in autonomic heart rate modulation preceding VT.

Post-discharge survival following pre-hospital cardiopulmonary arrest due to cardiac aetiology: temporal trends and impact of changes in clinical management

AIMS

To determine whether survival after discharge following pre-hospital cardiopulmonary arrest has improved.

METHODS AND RESULTS

The Heartstart Register was used to identify all 1659 patients discharged alive from Scottish hospitals during 1991-01 following pre-hospital arrest due to cardiac aetiology. The cohort was split into tertiles using year of arrest. A Cox proportional hazards model was used to determine risk of death relative to 1991-93. Patients who survived cardiopulmonary arrest in 1997-01 were less likely to die from any cause (unadjusted HR 0.60, 95% CI 0.48-0.75, P<0.001) or cardiac disease (unadjusted HR 0.50, 95% CI 0.38-0.65, P<0.001). After adjustment for case-mix, there remained significant declines in all-cause (adjusted HR 0.62, 95% CI 0.50-0.78, P<0.001) and cardiac death (adjusted HR 0.52, 95% CI 0.39-0.68, P<0.001). Clinical management had improved, with increased use of thrombolysis (47-63%, chi2 trend, P<0.001), beta-blockers (28-53%, chi2 trend, P<0.001), ACE-inhibitors (48-69%, chi2 trend, P<0.001), and anti-thrombotics (79-88%, chi2 trend, P<001). Adjustment for recorded changes in management attenuated the decline in all-cause death (adjusted HR 0.77, 95% CI 0.60-0.98, P=0.03).

CONCLUSION

Survival following cardiopulmonary arrest has improved after adjusting for changes in case-mix. Better clinical management has contributed to this improvement.

[The impact of the Multicenter Automatic Defibrillator Implantation Trial II in a university hospital--do all patients with myocardial infarction and reduced left ventricular function need an implantable cardioverter-defibrillator?]

BACKGROUND AND OBJECTIVES

Patients with coronary artery disease (CAD) and severely compromised left ventricular ejection fraction are at high risk to die from sudden cardiac death. The Multicenter Automatic Defibrillator implantation Trial II (MADIT II) shows a significant benefit of a cardioverter-defibrillator (ICD) therapy compared to standard treatment alone in this selected group of patients. The objective of the present study was to investigate the number of patients who will fulfil the MADIT II criteria and are candidates for prophylactic ICD implantation.

METHODS AND MATERIAL

From January to December 2001 a total of 2653 patients underwent coronary angiography at our institution due to angina pectoris, positive exercise stress testing, pathological SPECT myocardial perfusion images, suspected dilated cardiomyopathy or ventricular arrhythmias. According to the MADIT II inclusion criteria patients with significant coronary artery disease (diameter stenosis > 50%), ejection fraction < 0.31% and previous myocardial infarction were included. Exclusion criteria were acute coronary syndromes, patients with ventricular tachyarrhythmias or an existing indication for ICD therapy, and patients with coronary artery bypass graft surgery or percutaneous transluminal coronary angioplasty within the past or following three months.

RESULTS

Out of 2653 patients 185 (7%) had an ejection fraction less than 0.31, 149 (5.6%) showed significant coronary artery stenosis and 70 (2.6%) patients fulfilled the MADIT II criteria. The mean age of these patients was 68 +/- 9 years, the left ventricular ejection fraction 24 +/- 6. In 37 patients an ICD system was implanted according to the existing guidelines. 70 patients met the MADIT II inclusion criteria, resulting in an increase of 189% of ICD implantations per year.

CONCLUSION

2.6% out of 2653 patients who were referred to coronary angiography fulfilled the criteria of MADIT II. The expanding indication for ICD therapy will result in an annual increase of 70 (189%) prophylactic ICD implantations in our study population.

Determinants of geographic variations in pacemakers and implantable cardioverter defibrillators implantation rates

Despite the established therapeutic efficacy of pacemakers (PMs) and implantable cardioverter defibrillators (ICDs), marked geographic and national variations in their implant rates have been documented. Tabulation of implant rates and identification of variation patterns are of only modest significance as many factors influence geographic variations. This study examined statistical data regarding implant rates and analyzed the determinants behind these variations. The results showed: (1) the implantation rate of PMs and ICDs depends heavily on national economic status and demographics. (2) Economic factors are an important determinant of implant rates, though high rates were observed in countries with modest economic resources and highly educated physicians and populations. (3) Evaluation of PM and ICD implant rates per million of an overall population, unless based on demography, can lead to significant inaccuracy when comparing different regions and countries. Adjustment of implant rates consistent with demographic parameters is required. (4) Evaluation of the implant rate as appropriate, greater or less than expected in a given country can be achieved by calculation of a "reference" implant rate, and then by its comparison with the actual implant rate. Questions remaining after this analysis are: (1) How do variations in PM and ICD implant rate relate to quality of life, morbidity, and survival? (2) Will overall patient outcomes benefit from a greater implant rate, and is a higher implant rate cost-effective? (3) Should each country attempt to reach a "reference" implant rate, independent of its approach to medicine and level of economic development? These questions can only be answered by prospective randomized trials that allow the development of recommendations based on national needs and resources.

Geographic differences in implantable cardioverter defibrillator usage

Despite the demonstrated efficacy of implantable cardioverter defibrillators (ICDs) in reducing sudden and total mortality in selected patients, their implantation rates vary greatly among countries. In the United States, the implantation rate is 185 implants per million inhabitants compared with only 31 implants per million in western Europe. The differences in ICD use may be explained by the following factors: manner in which sudden cardiac death is perceived by politicians and physicians (sudden cardiac death is perceived as a "nice way of dying"); differences in indications; physicians' information; prevalence of coronary artery disease; sudden cardiac death survival rates; perceived reliability of alternative treatment (namely, antiarrhythmics including amiodarone); economic backgrounds; and health care politics. Furthermore, the cost of this treatment strategy must be considered. This issue has been raised because generalization of ICD use in patients matching clinical characteristics of patients enrolled in the primary prevention trials may represent a significant economic burden to be added to the already overloaded health care system. This low acceptance may not be entirely related to budget constraint but also to the perceived efficacy of ICDs by physicians and health authorities.