Methods

This retrospective cohort study involved all patients with AIC undergoing new implantation of a CRT device at the Cleveland Clinic (Cleveland, Ohio) from February 2000 to April 2007. Patients were diagnosed with AIC based on clinical history, results of a cardiac workup with proximity to receiving Adriamycin (Doxorubicin hydrochloride, Pfizer Inc., New York) for cancer therapy, and absence of another explanation for heart failure cause. Echocardiographic parameters and New York Heart Association (NYHA) class were assessed at the time of device implantation and at the time of first follow-up (mean 9.1 ± 6.3 months). This cohort was compared to 189 consecutive patients with non-AIC dilated cardiomyopathy who underwent CRT device implantation from 2005 to 2007. Stress testing and/or cardiac catheterization was used to establish a nonischemic cause. All patients had a left ventricular (LV) ejection fraction ≤35% and a wide QRS complex ≥120 ms or a narrow QRS with evidence of dyssynchrony on preimplantation echocardiogram (based on enrollment in the Cardiac-Resynchronization Therapy in Heart Failure with Narrow QRS Complexes [RethinQ trial ]) or an indication for permanent pacing. Titration of optimal medical therapy before CRT device implantation was made at the discretion of staff providers who had no knowledge of the present study. CRT device implantations were performed transvenously in most patients by electrophysiologists targeting a lateral or posterolateral vein for the LV lead position. In rare instances when a transvenous lead could not be placed due to procedural difficulty, a minimally invasive epicardial lead was placed by a staff cardiothoracic surgeon. Atrioventricular optimization was performed at the discretion of the treating physicians typically in the setting of poor response.

The electronic medical record was abstracted for demographic, clinical, and echocardiographic data. All patients had medication refractory heart failure and received an extensive cardiac workup including electrocardiography, echocardiography, laboratory testing, stress testing, and cardiac catheterization as clinically indicated. In our analysis, we included only procedures that were performed according to standard procedures at the Cleveland Clinic. The end points assessed were changes in LV ejection fraction, LV end-diastolic and end-systolic diameters, degree of severity of mitral regurgitation, and NYHA functional class from baseline to time of first follow-up after device implantation. All-cause mortality after device implantation was determined using the US Social Security Death index. Continuous variables were presented as mean ± SD. Discrete variables were recorded as percentages. Comparisons were made using Fisher’s exact test for discrete variables and Mann-Whitney test for continuous variables. Wilcoxon matched-pairs signed-ranks test was used to compare matched variables. Time-related outcomes were compared using Kaplan-Meier survival analysis.

A propensity score was derived using a multivariate logistic regression model with development of AIC as the dependent variable and age, gender, QRS duration, and baseline LV ejection fraction as the independent variables. The c-statistic for the propensity score model was 0.85, indicating a good ability to discriminate between patients with and without AIC. Patients were then matched on their propensity score using a greedy matching technique. With this technique, each patient with AIC was matched to a patient with the closest propensity score without AIC, thus addressing confounding by indication. For all analyses, a 2-tailed p value ≤0.05 was considered statistically significant. All analyses were performed using GraphPad Prism 5.0 (GraphPad Software, Inc., La Jolla, California) and SAS 9.1 (SAS Institute, Cary, North Carolina).

Results

Baseline characteristics of the overall study population are listed in Table 1 . Of patients in the AIC group, 61.1% had a history of breast cancer, with 77.8% of patients having a history of concomitant radiation therapy ( Table 2 ). Variables that differed significantly between the 2 groups were gender, baseline QRS duration, baseline LV ejection fraction, and incidences of hypertension and atrial fibrillation (p <0.05). All patients in the AIC group had the chronic or late-onset forms of the disease. Patients with AIC were also noted to have less LV dilatation at baseline compared to the nonischemic cardiomyopathy (NIC) cohort.

Pre- and postimplantation echocardiograms were available for all 18 patients in the AIC group and in 134 of 189 patients in the NIC group. Follow-up echocardiogram and NYHA class were assessed at a mean of 9.1 ± 6.3 months after CRT device implantation. Patients with AIC were seen to improve across all echocardiographic end points including increases in LV ejection fraction ( Figure 1 ) and decreases in LV end-diastolic and end-systolic dimensions, mitral regurgitation, and NYHA functional class ( Table 3 ). These improvements were comparable to that observed in the NIC cohort ( Table 4 ). Of patients in the AIC group, 72.2% demonstrated an improvement in LV ejection fraction of ≥5% versus 70.9% in the NIC group (p = 1.0). Of patients in the AIC group, 16.6% had no significant change in LV ejection fraction versus 17.3% in the NIC group (p = 1.0). Of patients with AIC, 11.1% had a worsening in LV ejection fraction compared to 11.8% in the NIC group (p = 1.0). In the AIC group, 69.2% showed an increase in NYHA functional class versus 67.4% in the NIC group (p = 1.0), 30.75% had no change versus 20.3% in the NIC group (p = 0.73), and no patients worsened versus 12.2% in the NIC group (p = 0.36). There were 4 deaths in the AIC group versus 26 in the NIC group (p = 0.75) over a mean follow-up of 3.12 ± 0.95 years ( Figure 2 ).

Ejection fraction before (EF pre) and after (EF post) CRT in patients with AIC at baseline and at 9.1 ± 6.3 months.

Table 3

Echocardiographic and functional class changes in patients with Adriamycin-induced cardiomyopathy before and after cardiac resynchronization therapy

Variable	Baseline	After	Change	p Value
Ejection fraction (%)	18.6 ± 7.6	27.2 ± 13.5	8.6 ± 9.5	0.0006
Left ventricular end-diastolic diameter (cm)	6.04 ± 0.63	5.56 ± 0.95	−0.49 ± 0.64	0.0131
Left ventricular end-systolic diameter (cm)	5.17 ± 0.71	4.47 ± 1.18	−0.71 ± 0.77	0.0031
Mitral regurgitation (severity 0–9)	4.3 ± 2.0	3.1 ± 1.9	−1.2 ± 2.3	0.0420
New York Heart Association functional class	2.9 ± 0.3	2.4 ± 0.3	−0.6 ± 0.5	0.0039

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