Author + information
- Received June 27, 2012
- Revision received October 11, 2012
- Accepted November 8, 2012
- Published online March 5, 2013.
- Valentina Kutyifa, MD*,†,* (, )
- Axel Kloppe, MD‡,
- Wojciech Zareba, MD, PhD*,
- Scott D. Solomon, MD§,
- Scott McNitt, MS*,
- Slava Polonsky, MS*,
- Alon Barsheshet, MD*,
- Bela Merkely, MD, PhD†,
- Bernd Lemke, MD‡,
- Vivien Klaudia Nagy, MD†,
- Arthur J. Moss, MD* and
- Ilan Goldenberg, MD*
- ↵*Reprint requests and correspondence:
Dr. Valentina Kutyifa, Heart Research Follow-up Program, Cardiology Division, University of Rochester Medical Center, 265 Crittenden Boulevard, Box 653, Rochester, New York 14642
Objectives The goal of this study was to evaluate the influence of left ventricular (LV) lead position on the risk of ventricular tachyarrhythmia in patients undergoing cardiac resynchronization therapy (CRT).
Background Left ventricular ejection fraction (LVEF) is a surrogate marker of heart failure (HF) status and associated risk. Data on the effectiveness of cardiac resynchronization therapy with defibrillator (CRT-D) in patients with mild HF and better LVEF are limited.
Methods In the MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy) study, the echocardiography core laboratory assessed baseline LVEF independent of the enrolling centers and identified a range of LVEFs, including those >30% (i.e., beyond the eligibility criteria). Echocardiographic response with CRT, defined as percent change in left ventricular end-diastolic volume (LVEDV), was analyzed in 3 prespecified LVEF groups: >30%, 26% to 30%, and ≤25%. The primary endpoint was HF or death. Secondary endpoint included all-cause mortality.
Results LVEF was evaluated in 1,809 study patients. There were 696 (38%) patients with LVEF >30% (in the range of 30.1% to 45.3%); 914 patients (50.5%) with LVEF 26% to 30%; and 199 patients with LVEF ≤25% (11%). The mean reduction in LVEDV with CRT-D therapy at the 1-year follow-up was directly related to increasing LVEF (LVEF >30%: 22.3%; LVEF 26% to 30%: 20.1%; and LVEF ≤25%: 18.7% reduction, respectively [p = 0.001]). CRT-D treatment similarly reduced the risk of HF/death in patients with LVEF >30% (hazard ratio [HR]: = 0.56 [95% confidence interval (CI): 0.39 to 0.82], p = 0.003), LVEF 26% to 30% (HR: 0.67: [95% CI: 0.50 to 0.90], p = 0.007), and LVEF ≤25% (HR: 0.57 [95% CI: 0.35 to 0.95], p = 0.03; all p values for LVEF-by-treatment interactions >0.1).
Conclusions In MADIT-CRT, the clinical benefit of CRT was evident regardless of baseline LVEF, including those with LVEF >30%, whereas the echocardiographic response was increased with increasing LVEF, indicating that CRT might benefit patients with better LVEF. (Multicenter Automatic Defibrillator Implantation With Cardiac Resynchronization Therapy [MADIT-CRT]; NCT00180271)
- cardiac resynchronization therapy
- heart failure
- implantable cardioverter-defibrillator
- left ventricular ejection fraction
Cardiac resynchronization therapy (CRT) has been shown to reduce heart failure (HF) symptoms, hospitalizations, and mortality in patients with moderate or severe drug-refractory HF, severely depressed left ventricular ejection fraction (LVEF), and prolonged QRS interval (1–3). CRT provides electromechanical resynchronization, improves left ventricular systolic function, and induces left ventricular reverse remodeling (4).
The MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy) study, the RAFT (Resynchronization/Defibrillation in Ambulatory Heart Failure Trial) study, and the REVERSE (Resynchronization Reverses Remodeling in Systolic Left Ventricular Dysfunction) trial have further broadened CRT indication to patients with mild HF (5–7).
Using the preselected cutoff point of left ventricular ejection fraction (LVEF) as inclusion criterion for CRT is considered an arbitrary method. Patients develop HF across the spectrum of LVEF. Depressed LVEF was shown to be a surrogate marker of HF status and is associated with increased risk of adverse events, all-cause mortality, and sudden cardiac death (8–10). However, the risk associated with LVEF is a continuum until the cutoff point of 45% (9). Therefore, there is a rationale for CRT in patients with less depressed LVEF.
In MADIT-CRT, inclusion criteria comprised patients with LVEF ≤30% as evaluated by enrolling centers before enrollment. All patients additionally underwent central echocardiographic analysis of LVEF in the study core laboratory of Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, where a substantial proportion of patients were identified as having LVEF >30%, which is beyond the eligibility criteria. This provides a unique opportunity to evaluate the efficacy of cardiac resynchronization therapy with defibrillator (CRT-D) in patients with less decreased cardiac function.
The aims of the current study were to evaluate the relationship between LVEF and the following: 1) the clinical outcomes of patient with mild HF enrolled in MADIT-CRT; 2) the echocardiographic response to CRT-D in the trial; and 3) the clinical benefit of CRT-D, with a specific focus on the subset of patients with more preserved LVEF enrolled in the trial.
The design, protocol, and results of MADIT-CRT have been published previously (11,12). Briefly, 1,820 patients with ischemic cardiomyopathy (New York Heart Association [NYHA] functional class I or II) or nonischemic cardiomyopathy (NHYA functional class II only), LVEF <30%, and a prolonged QRS duration >130 ms were randomized to receive CRT-D or implantable cardioverter-defibrillator (ICD) therapy in a 3:2 ratio. All eligible patients met the guideline criteria for ICD (13). Patients were excluded if they were aged <21 years, if they had existing indication for CRT, implanted pacemaker, NYHA III or IV functional class in the past 90 days before enrollment, coronary artery bypass graft surgery, or percutaneous coronary intervention or myocardial infarction within the past 90 days before enrollment. A total of 110 hospital centers from North America and Europe participated in this international multicenter trial. The study was in compliance with the Declaration of Helsinki, and all enrolling sites had the protocol approved by the local institutional review board. All patients provided written informed consent before enrollment.
Patients were excluded from the current study if their baseline LVEF measurement was not available due to missing images or poor quality of echocardiographic images. Accordingly, the study sample comprised 1,809 (99%) of the 1,820 patients enrolled in MADIT-CRT; 1,074 (60%) were randomized to CRT-D therapy. The baseline analysis was performed on an intention-to-treat basis.
Data acquisition and patient follow-up
The MADIT-CRT trial was conducted from December 22, 2004, through June 22, 2009. After device implantation, patients had an ambulatory follow-up at 1 month and every 3 months thereafter until the termination of the trial. The mean follow-up of the enrolled patients was 29.4 months. All patients had clinical evaluation at each follow-up visit or at any meaningful clinical event.
Echocardiograms were obtained according to a study-specific protocol at baseline, which was before device implantation (n = 1,809), and at 1 year. Paired echocardiograms from baseline and at 12 months with device turned on were available in 1,372 patients (623 patients in the ICD-only group and 749 in the CRT-D group).
Echocardiography investigators and sonographers were qualified to perform echocardiography according to the approved echocardiography protocol. Recordings were analyzed off-line at the Brigham and Women's Hospital as an independent echocardiography core laboratory. Echocardiography investigators analyzing the images were blinded to treatment assignment or clinical outcome.
Left ventricular volumes were measured by using Simpson's disk method in the apical 4- and 2-chamber views, and LVEF was calculated according to the established American Society of Echocardiography protocols (14). The coefficients of variation for end-diastolic volume, end-systolic volume, and LVEF were 5.2%, 6.2%, and 5.5%, respectively, as reported previously (4).
Left ventricular mechanical dyssynchrony was measured by using B-mode speckle tracking software (TomTec Imaging Systems, Unterschleissheim, Germany), as reported previously (15). Left ventricular mechanical dyssynchrony was determined as the SD of regional time-to-peak transverse strain, measured during systole in the 12 anatomic wall segments (septum, lateral, anterior, and inferior walls basal, mid- and apical segments) of the left ventricle.
Definitions and endpoints
Patients with baseline LVEF measurements were divided into 3 prespecified groups based on the echocardiography core laboratory assessment: LVEF ≤25%, LVEF 26% to 30% (classic criterion), and LVEF >30% (beyond the eligibility criteria).
The primary endpoint of the current study was the first occurrence of an HF episode or death from any cause. Secondary endpoint included all-cause mortality.
The diagnosis of HF was made by physicians unblinded to treatment assignment, if patients were exhibiting signs and symptoms consistent with congestive HF that resulted in intravenous decongestive treatment in an outpatient setting or augmented decongestive therapy with oral or parenteral medications during an in-hospital stay. Adjudication of the endpoints (both HF/death and death) was conducted by an independent mortality committee and by an HF committee unaware of treatment assignments, according to prespecified criteria, as described previously (11).
When analyzing the echocardiographic response to CRT, we evaluated the left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), and left atrial volume (LAV) percent changes at the 12-month follow-up in all 3 LVEF groups.
The left ventricular remodeling effect of CRT-D was defined as percent reduction in LVEDV between enrollment and 1-year echocardiogram (calculated as the difference between 1-year and baseline LVEDV, divided by baseline LVEDV). The left atrial remodeling effect of CRT-D was defined as percent reduction in LAV between enrollment and 1-year echocardiogram (calculated as the difference between 1-year volume and baseline volume, divided by baseline volume).
Continuous variables are expressed as mean ± SD. Categorical data are summarized as frequencies and percentages. Baseline clinical characteristics were compared between the prespecified subgroups stratified according to baseline LVEF by using the Kruskal-Wallis test for continuous variables and the chi-square test or Fisher exact test for dichotomous variables, as appropriate. The correlation of LVEF identified by the centers and measured by the echocardiography core laboratory was analyzed by using the Spearman's rank correlation method. The correlation of baseline LVEF, QRS duration, and left ventricular volumes were assessed by using the Pearson's correlation method. Regression models were conducted to evaluate the relation between baseline dyssynchrony and the degree of echocardiographic response to CRT (defined as percent change in LVESV at 1 year) within each ejection fraction (EF) category.
Cumulative probability of first HF or death events according to baseline LVEF and treatment arm within each LVEF group was displayed according to the Kaplan-Meier method, with comparisons of cumulative event rates according to the log-rank test. Multivariate Cox proportional hazards regression analysis was used to identify and evaluate the impact of LVEF groups on the endpoint of HF/death or death. The Cox model was adjusted for relevant clinical covariates by using best subset regression modeling.
All statistical tests were 2-sided; a p value <0.05 was considered statistically significant. Analyses were conducted by using SAS version 9.2 (SAS Institute, Inc., Cary, North Carolina).
At baseline, 914 patients (50.5%) had LVEF 26% to 30% (median = 28.1%; quartile [Q] Q1 = 27.1%; Q3 = 29.0%), and 199 patients (11%) comprised the LVEF group of ≤25% (median = 23.2%; Q1 = 21.8%; Q3 = 24.2%). The subgroup of LVEF >30% included 696 (38%) patients (in the range of 30.1% to 45.3%; median = 31.8%; Q1 = 30.8%; Q3 = 33.1%), as evaluated by the echocardiography core laboratory.
LVEFs identified by the enrolling centers were multiples of 5 in 72% of cases, possibly due to the fact that most centers used estimates for this measure. There was a weak but significant correlation between LVEFs identified by the centers and measured by the echocardiography core laboratory (r2 = 0.105, p < 0.001). The distribution and correlation of LVEF identified by the enrolling centers and measured by the echocardiography core laboratory are shown in Figure 1.
The baseline clinical characteristics of patients with LVEF ≤25%, LVEF 26% to 30%, and LVEF >30% are shown in Table 1. Patients with increasing LVEF were older, more often female, had a lower heart rate, less often had left bundle branch block and more often right bundle branch block, and had an intraventricular conduction delay electrocardiography pattern. There was a trend toward more frequent ischemic cardiomyopathy and fewer previous episodes of severe HF (>3 months before enrollment) with less depressed LVEF. Baseline drug treatment was similar across LVEF ranges, with less use of diuretics and digitalis with increasing LVEF. Echocardiographic results showed gradually smaller LVEDV, LVESV, and LAVs across LVEF groups, demonstrating less advanced stage of the disease.
Baseline LVEF was inversely related to baseline QRS (r = −0.22, p < 0.001), and left ventricular volumes (LVEDV index r = 0.35, p < 0.001; LVESV index r = 0.36, p < 0.001), suggesting that these parameters were highly correlated in MADIT-CRT.
Effect of baseline LVEF on primary clinical outcome and all-cause mortality
The primary endpoint of HF or death was met in 375 patients (20.7%) with baseline LVEF measurements; 126 patients (7%) died, 78 (4.3%) of cardiac causes during the mean follow-up of 29.4 ± 11 months.
Patients with baseline LVEF ≤25% showed significantly higher cumulative incidence of HF or death episodes compared with patients with LVEF 26% to 30% or LVEF >30% (Fig. 2A).
The multivariate Cox model after adjustment for relevant clinical covariates (treatment, ischemic etiology of cardiomyopathy, NYHA class III or IV greater than 3 months before enrollment, baseline heart rate, and age at enrollment) revealed similar findings. Patients with LVEF ≤25% had 55% higher risk of HF or death compared with patients with LVEF 26% to 30%, and 66% higher risk compared with patients with LVEF >30%. Patients with LVEF 26% to 30% and LVEF >30% demonstrated a similar risk of HF/death. LVEF as a continuous measure was a surrogate marker of the primary endpoint, demonstrating a significant 5% reduction in the risk of HF/death for each unit increment in LVEF (Table 2).
Patients had low and similar incidence of all-cause mortality irrespective of their LVEF group at baseline (3-year Kaplan-Meier cumulative event rates in LVEF ≤25%: 9%; LVEF 26% to 30%: 8%; LVEF >30%: 8% [p log-rank test = 0.709]) (Fig. 2B). This finding was confirmed in the multivariate model after adjustment for relevant clinical covariates (data not shown).
Effect of CRT therapy on the primary clinical outcome and all-cause mortality by LVEF
Evaluating the treatment effects of CRT-D versus ICD-only therapy, 1,809 patients (1,074 CRT-D patients and 735 ICD patients) with baseline LVEF data available were analyzed on an intention-to-treat basis.
Univariate Kaplan-Meier survival analysis showed that compared with ICD-only therapy, treatment with CRT-D showed borderline significance in decreasing the cumulative incidence of HF/death in patients with LVEF ≤25% (p = 0.062). This effect was statistically significant among patients with LVEF 26% to 30% (p = 0.003) and with LVEF 30% (p = 0.009) (Fig. 3).
Consistent with these findings, the multivariate Cox model after adjustment for relevant clinical covariates found that CRT-D treatment was associated with a significant 43% reduction in the risk of HF or death in patients with LVEF ≤25% (p = 0.03), a 33% risk reduction in patients with LVEF 26% to 30% (p = 0.007), and a significant 44% risk reduction among those with LVEF >30% (p = 0.003). The interaction p value was not significant for all LVEF groups (all p values for treatment-by-LVEF interactions >0.10), indicating that the clinical benefit of CRT-D was maintained regardless of baseline LVEF (Table 3).
The treatment effect on the endpoint of all-cause mortality was neutral in patients with LVEF <25% (hazard ratio [HR]: 1.49 [95% confidence interval (CI): 0.60 to 3.70], p = 0.387), LVEF 26% to 30% (HR: 0.89 [95% CI: 0.54 to 1.46], p = 0.647), and LVEF >30% (HR: 0.85 [95% CI: 0.46 to 1.58], p = 0.614), possibly due to the relatively low rate of mortality events in each LVEF group during the trial (Fig. 2B).
The magnitude of echocardiographic response to CRT-D by LVEF groups
Echocardiographic response was assessed at 12-month follow-up in patients with implanted CRT-D; crossovers were excluded from this analysis (n = 119).
Echocardiographic response to CRT-D was directly correlated to LVEF. Patients with LVEF ≤25% exhibited less decrease of LVEDV percent change from baseline to 1 year (−18.7 ± 11.6%) compared with patients with LVEF 26% to 30% (−20.1 ± 10.7%) or patients with LVEF >30% (−22.3 ± 12.3%) (p = 0.001). Furthermore, patients with LVEF >30% showed a significantly greater reduction in LVEDV than patients with LVEF 26% to 30% (p = 0.001).
Similarly, the degree of LVESV percent reduction with CRT-D therapy was also directly correlated to increasing LVEF groups (−31.4 ± 13.5% change vs. −32.0 ± 13.8% vs. −33.6 ± 17.1% change; p < 0.001 for the overall difference). Patients with LVEF >30% exhibited a greater reduction in LVESV than patients with LVEF 26% to 30% (p = 0.029).
Consistent findings were seen in LAV reduction (−22.67 ± 10.9% vs. −27.6 ± 11.6% vs. −30.4 ± 12.5%; p < 0.001). Again, patients with LVEF >30% gained more pronounced left atrial remodeling than those with LVEF 26% to 30% (p = 0.001) (Fig. 4).
We also analyzed LV dyssynchrony data available in 587 (61.5%) of 955 patients undergoing CRT-D. Patients with LVEF ≤25% exhibited greater baseline left ventricular dyssynchrony (207.1 ± 63.1 ms) compared with patients with LVEF 26% to 30% (194 ± 64.4 ms) or LVEF >30% (175.5 ± 65.3 ms) (p < 0.001). However, the reduction in left ventricular dyssynchrony at 12 months of follow-up was similar across LVEF groups (−13.4 ± 49.1% vs. −19.0 ± 43.0% vs. −14.0 ± 55.8% change; p = 0.93). We further correlated the relation between baseline dyssynchrony and the degree of echocardiographic response to CRT (defined as percent change in LVESV at 1 year) within each EF category prespecified by using a regression model. This analysis showed that among patients with LVEF >30% and LVEF 26% to 30%, the degree of baseline dyssynchrony was directly correlated with the percent reduction in LVESV (p < 0.001 for both categories). Among those with a lower LVEF, there was no correlation between dyssynchrony and echocardiographic response to CRT (p = 0.99).
Our study demonstrates that patients with mild HF with LVEF ≤25% at baseline had an increased risk for subsequent HF or death compared with patients with LVEF 26% to 30% or LVEF >30%. However, the clinical benefit of CRT-D was maintained across all LVEF groups; the echocardiographic response to CRT-D was even more pronounced among patients with higher LVEFs, including those with LVEF >30% (beyond the eligibility criteria of this study). These findings suggest that mildly symptomatic HF patients with LVEF >30% might be potential candidates for CRT-D. Furthermore, this subset of patients may derive a more favorable echocardiographic response to CRT-D than patients currently indicated for treatment with the device, which could translate into improved clinical outcome during long-term follow-up.
Previous smaller studies have suggested that patients with severe HF (NYHA III and IV) and higher baseline LVEF could be eligible for CRT; they have shown improvement in clinical status and echocardiographic parameters (16,17). Recently, Chung et al. (18) reported that 86 (24%) of 361 patients enrolled in the PROSPECT (Predictors of Response to Cardiac Re-Synchronization Therapy) trial had LVEF >35% measured by the echocardiography core laboratory. They found that CRT improved the clinical composite score and was associated with similar decrease of LVESV in patients with LVEF ≤35% or >35%. The REVERSE trial included patients with mild HF and LVEF <40% (6); however, the mean LVEF in the study was low (26.8 ± 7.0% in the group with the CRT device turned ON [CRT ON] CRT-ON arm), indicating that the proportion of patients with better LVEF might have been small. In contrast to the PROSPECT substudy, our analysis showed that patients with LVEF >30% exhibited even more pronounced echocardiographic response to CRT-D than patients with lower LVEF.
The findings of this analysis seem to be in contrast to previous data that the sickest patients may benefit most from device therapy due to increased long-term risk (19). However, we suspect that as with most therapies, there is a “sweet spot” for CRT, whereby there may be benefit as ventricular function worsens to some extent, but that when ventricular function worsens beyond a certain level, there is no further benefit because the ventricle becomes too “sick” to respond.
The importance of a preventive strategy in HF has been demonstrated by a study by Gasparini et al. (20); in a population of >500 patients, 26% achieved left ventricular remission (defined as return to NYHA I and EF >50%). Notably, in multivariate analysis, an LVEF 30% to 35% and LVEDV <180 ml were strongly associated with the HF remission phase. We have shown similar effect in the current analysis in patients with mild HF and CRT implantation.
Notably, patients with LVEF >30% showed a clinical response to CRT-D similar to that of patients with lower LVEF, despite the fact that they had a higher frequency of right bundle branch block and intraventricular conduction delay and less wide QRS durations, characteristics which were proven to be associated with unfavorable response in MADIT-CRT (21). There was a significant correlation between baseline QRS duration and LVEF and baseline QRS duration and LVEDV/LVESV index. Furthermore, patients with LVEF >30% had significantly smaller end-diastolic and end-systolic volumes, indicating less advanced stage of the disease. This finding highlights the importance of HF progression prevention in this patient population.
The risk of HF or death was significantly higher in the patient group with LVEF <25%; however, the curves diverged only after 1 year. This phenomenon might be explained by the fact that those patients implanted with a CRT-D device develop left ventricular reverse remodeling within 1 year, which is associated with a subsequent reduction in the risk of HF or death events. This mechanism is consistent with a previous publication from MADIT-CRT, which showed that changes in left ventricular volumes with CRT therapy are highly correlated with subsequent clinical outcomes (4).
Similar to the primary MADIT-CRT report, in which treatment with CRT-D was not associated with a statistically significant effect on the risk of all-cause mortality (12), the current study also found no significant mortality reduction with CRT-D in any of the LVEF subgroups. This can be explained by the fact that patients with asymptomatic or mild HF enrolled in MADIT-CRT experienced a relatively low rate of death during the trial, possibly requiring a longer follow-up period to show a significant mortality benefit from the device.
We found a significant reduction in LAV in all 3 LVEF groups, which might be explained by significant reduction in mitral regurgitation as reported in the total CRT-D population compared with ICD patients (published elsewhere [4,22]). Another publication from our group evaluated the reduction in LAV and subsequent decrease in atrial arrhythmias, suggesting that reduction in LAV was associated with significantly lower risk of atrial arrhythmias (22). Therefore, we hypothesize that patients with LVEF >30% have more significant reduction in LAV, probably due to a more pronounced decrease in mitral regurgitation that might be associated with lower risk of atrial arrhythmias during follow-up. Furthermore, LAV often reflects the cumulative effects of left ventricular filling pressures over time and thus may provide a more sensitive morphophysiologic expression of the remodeling effects of CRT than the left ventricle.
The relationship of baseline dyssynchrony and clinical outcome in MADIT-CRT has been reported earlier (4). Briefly, those patients with mild to moderate baseline dyssynchrony demonstrated the greatest benefit from CRT-D, whereas those with lower or higher degrees of dyssynchrony derived a lower benefit, displaying a J-shaped pattern within quartiles. In the current analysis, it also seems that patients with a lower EF, who had a greater degree of baseline dyssynchrony, had a lower echocardiographic response to CRT compared with patients in the higher EF categories. This finding is further supported by the correlation of dyssynchrony and echocardiographic response in the LVEF 26% to 30% group and the LVEF >30% group, whereas patients with LVEF ≤25% did not show association between dyssynchrony and echocardiographic response. These results differ from previous reports among patients with more advanced HF symptoms, in which there was a direct correlation between the degree of dyssynchrony and response to CRT. Thus, our findings regarding the interaction among baseline LVEF, dyssynchrony, and response to CRT may be unique to the patients with mild HF who are treated with the device.
The current study found a pronounced difference between the echocardiographic assessment of LVEF at the sites and the central core laboratory assessment. Thus, 38% of the patients who were identified by the centers as having LVEF ≤30%, and therefore deemed eligible for the study, were subsequently determined by the core laboratory as having LVEF >30%. These differences are similar to those shown in the PROSPECT study (18) and may be possibly explained by the fact that a nonblinded reading of cardiac function can be biased by the patient's condition, and by inclusion bias, and may therefore underestimate LVEF. LVEF identified by the centers were in multiples of 5 in 72% of cases, suggesting that sites used visual estimation rather than a more quantitative approach (as was used in the core laboratory).
This is the first report of data presented from a large patient cohort analyzing the impact of baseline LVEF, including those with LVEF >30% on the primary endpoint of HF or death in patients with NYHA class I or II undergoing CRT implantation.
This is a post hoc analysis by echocardiographic groups that were not part of the original design of MADIT-CRT, and the incomplete datasets or images with poor quality were excluded from the analysis. Another possible limitation is that some study patients with images at baseline might be deactivated from the study or die before the 1-year reassessment. Our results did not show a statistically significant difference in the benefit of CRT-D for the primary endpoint among the EF subgroups according to interaction term analyses. However, the lack of statistical significance of the interaction tests may be related to sample size and the number of primary endpoint events in MADIT-CRT.
We demonstrated that the clinical benefit of CRT is present regardless of LVEF groups in patients enrolled in MADIT-CRT, including those with LVEF >30% (beyond the eligibility criteria). The echocardiographic response was directly correlated with increasing LVEF, indicating that patients with better baseline LVEF may derive benefit from CRT.
The MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy) study was supported by a research grant from Boston Scientific to the University of Rochester School of Medicine and Dentistry. Dr. Kutyifa has received honoraria from Servier and research support from Boston Scientific. Dr. Merkely is a member of the speaker's bureau for Boehringer-Ingelheim; and has received honoraria/consultant fees from Biotronik, Medtronic, and St. Jude Medical. Drs. Zareba and Solomon have received research grants from Boston Scientific. Drs. Moss and Goldenberg have received research grants. All others authors have reported that they have no relationships relevant to the contents of this paper to disclose. The first 2 authors contributed equally to the original concept and to authorship of this investigation.
- Abbreviations and Acronyms
- confidence interval
- cardiac resynchronization therapy
- cardiac resynchronization therapy with defibrillator
- ejection fraction
- heart failure
- hazard ratio
- implantable cardioverter-defibrillator
- left atrial volume
- left ventricular end-diastolic volume
- left ventricular ejection fraction
- left ventricular end-systolic volume
- New York Heart Association
- Received June 27, 2012.
- Revision received October 11, 2012.
- Accepted November 8, 2012.
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