CLINICAL RESEARCH
Europace (2012) 14, 341–344 doi:10.1093/europace/eur360
Sudden Death and ICDs
Women and minorities are less likely to receive an implantable cardioverter defibrillator for primary prevention of sudden cardiac death Ure Mezu, Iftikhar Ch, Indrani Halder, Barry London, and Samir Saba * University of Pittsburgh Medical Center, 200 Lothrop Street, UPMC Presbyterian, Suite B-535, Pittsburgh, PA 15213-2582, USA Received 1 August 2011; accepted after revision 21 October 2011; online publish-ahead-of-print 8 November 2011
Introduction
Implantable cardioverter defibrillators (ICDs) improve survival in patients with depressed left ventricular ejection fraction (EF). We investigated whether women and minorities are as likely as white men to receive an ICD for primary prevention of sudden cardiac death. ..................................................................................................................................................................................... Methods We reviewed the electronic medical records of patients with cardiomyopathy by nuclear single-photon emission and results computed tomography imaging (EF ≤ 35%), who had no prior history of sustained ventricular arrhythmias. Clinical and demographic data were collected and the Charlson comorbidity index (CCI) was calculated for each patient. A total of 233 non-selected patients (age ¼ 68 + 12 years, 29% women, 21% black, EF 24 + 6%, CCI 6.62 + 2.9) were included in this analysis of whom 111 (48%) received an ICD. In univariate analysis, ICD recipients were more likely to be Caucasian men compared with black men or women from all races. After adjusting for race, gender, EF, and the CCI in a multivariate logistic regression model, women were 61% less likely than men [odds ratio (OR) ¼ 0.39, 95% confidence interval (CI) 0.20–0.74, P ¼ 0.004] and blacks were 72% less likely than whites (OR ¼ 0.28, 95% CI 0.13–0.59, P ¼ 0.001) to receive an ICD. ..................................................................................................................................................................................... Conclusions Even after adjusting for comorbid conditions, gender, and racial discrepancies in the implantation of ICDs for the primary prevention of sudden cardiac death exist. Further investigations into the root causes of these discrepancies are needed before any corrective measures can be adopted.
----------------------------------------------------------------------------------------------------------------------------------------------------------Keywords
Gender † Ethnicity † Defibrillator † Sudden cardiac death † Primary prevention
When compared with conventional pharmacological therapy, implantable cardioverter defibrillators (ICDs) decrease all-cause mortality and prolong survival in patients with severe left ventricular dysfunction primarily by reducing the risk of arrhythmic death.1 – 4 Accordingly, published guidelines5 recommend implanting an ICD in patients with severe cardiomyopathy whose left ventricular ejection fraction (EF) is ≤35%. Several studies have reported gender and racial disparities in the delivery of cardiac care.6 – 8 More specifically, these trends have been examined in the context of ICD implantations with conflicting results. While some studies based on claims and registry data reported significant underutilization of this life-saving therapy in eligible patients with a concomitant significant gender and racial biases,9 – 13 others have adopted detailed chart review and
exposed these studies as suffering from dramatic overestimations of the rates of ICD underuse and of the disparities by gender and age in the delivery of this life-saving therapy.14 Our group had originally reported that survivors of cardiac arrest between 1996 and 2003 were less likely to receive an ICD if they belonged to ethnic minority groups.15 A follow-up report from the same national database demonstrated improving rates of ICD implantation in survivors of cardiac arrest and closing of the previously exposed racial gap.16 Given the conflicting data based on the method and time frame of prior analyses, we investigated in the present study, over a short period of time restricted to 12 months, whether women and minorities in the urban setting are as likely as white men to receive an ICD for primary prevention of sudden cardiac death, taking
* Corresponding author. Tel: +1 412 647 6272; fax: +1 412 647 7979, Email:
[email protected] Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2011. For permissions please email:
[email protected].
342
U. Mezu et al.
into account detailed chart reviews for 19 comorbid medical conditions that are known to affect survival as part of the validated Charlson comorbidity index (CCI).17,18
depending on the risk of dying associated with the condition. The overall comorbidity score, which predicts mortality for each patient is the arithmetic sum of the values assigned to each identified comorbid condition.17,18.
Methods
Statistical analysis
Patient population and data collection We identified 485 non-selected, consecutive patients who had nuclear imaging in the cardiology department of our institution between January 2006 and December 2006 demonstrating a low EF (≤35%). From this group, patients were eliminated if they had conflicting contemporary EF measurements (.35%) in the medical record (n ¼ 152), or a history of sustained arrhythmias or cardiac arrest (n ¼ 100). The presence of an ICD with or without cardiac resynchronization therapy was determined by manual chart review over a 4-year period subsequent to the documented low EF by nuclear imaging or until documented date of death. Clinical and demographic data were collected and the CCI which predicts the 1-year mortality based on a total of 19 comorbid conditions was calculated for each patient.17,18 For the purposes of this study, primary prevention was defined as implantation in patients with (i) ischaemic or non-ischaemic cardiomyopathy, EF ≤ 35% with a New York Heart Association (NYHA) Class II or III or (ii) patients with EF ≤ 30%, prior myocardial infarction with Class I NYHA.19 The main outcome was the actual implantation of an ICD at any time throughout the follow-up period.
Comorbidities Comorbid conditions in both the ICD and non-ICD groups were assessed using the CCI, which incorporates 19 medical conditions that affect longevity. Table 1 lists the variables included in the CCI. The CCI was calculated by assigning a weight score of 1, 2, 3, or 6
Table 1 Comorbid conditions included in the Charlson comorbidity index
Continuous variables were expressed as mean + standard deviation while categorical variables were presented as percentages. Variables showing significance on univariate analysis (P , 0.1) or predetermined by study design were included in the multivariate analyses. Predetermined variables included the CCI and the EF. A binary logistic regression model was used to assess the independent effect of gender and ethnicity on the likelihood of a patient receiving an ICD for primary prevention indications, while accounting for significant comorbid conditions. A twotailed P value of ,0.05 was considered statistically significant. All analyses were performed using SPSS version 11.0 (Chicago, IL, USA).
Results Baseline characteristics A total of 233 patients with cardiomyopathy and EF ≤ 35% by nuclear imaging who had no conflicting EF measurements and no history of sustained arrhythmia were included in the final analysis. Of those, 111 (48%) received an ICD. Table 2 shows the baseline characteristics of the overall study population and of both the ICD and non-ICD groups. In brief, in univariate analysis, women were significantly less likely than men to receive an ICD (29% of women vs. 55% of men, P ¼ 0.001, Figure 1). Also, black patients were significantly less likely than their white counterparts to receive an ICD (25% of black patients vs. 53% of white patients, P ¼ 0.001, Figure 1). Compared with patients with non-ICDs, ICD recipients had lower EF (23 + 7 vs. 26 + 7%, P ¼ 0.003) and better (i.e. lower) CCI (6.15 + 2.68 vs. 7.05 + 3.17, P ¼ 0.021).
Multivariate analysis After adjusting for gender, race, EF, and the CCI in a multivariate binary logistic regression model (Table 3), women were 61% [odds ratio (OR) ¼ 0.39, 95% confidence interval (CI) 0.20– 0.74,
Score
Condition
1
Myocardial infarction
1 1
Congestive heart failure Peripheral vascular disease
1
Cerebrovascular disease
1 1
Dementia Chronic pulmonary disease
1
Connective tissue disease
Overall
ICD
No ICD
1 1
Peptic ulcer disease Mild liver disease
N 5 233
N 5 111
N 5 122
1
Diabetes
68 + 12
2 2
Haemiplegia Moderate or severe renal disease
2
Diabetes with end organ damage
2 2
Any tumour Leukaemia
2
Lymphoma
3 6
Moderate or severe liver disease Metastatic solid tumour
6
Acquired immunodeficiency syndrome
................................................................................
Table 2 Baseline characteristics of study population by implantable cardiac defibrillator status P value
................................................................................ 67 + 11
69 + 12
Gender (women) 29%
18%
39%
,0.001
Race (black) EF
21% 25 + 7%
11% 23 + 7%
29% 26 + 7%
,0.001 0.003
CCI
6.62 + 2.98 6.15 + 2.68 7.05 + 3.17
0.021
CHF diagnosis Strokes
91% 30%
94% 31%
88% 29%
0.118 0.680
COPD diagnosis
72%
75%
69%
0.196
Age (years)
0.278
ICD, implantable cardiac defibrillator; EF, left ventricular ejection fraction; CCI, Charlson comorbidity index; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease.
343
Ethnic and gender effects on ICD implantation
70
Percent of patients receiving an ICD
P
