Can cardiac resynchronization therapy cause harm?

Differentiation between left bundle branch block (LBBB) preceded dilated cardiomyopathy and dilated cardiomyopathy preceded LBBB by cardiac magnetic resonance imaging

BACKGROUND

Dilated cardiomyopathy (DCM) may be a result of or the cause of left bundle branch block (LBBB) in patients with DCM and LBBB. It is almost impossible from the history alone to know which came first in clinical work.

METHODS

Patients with LBBB and DCM who had cardiac magnetic resonance (CMR) examination were analyzed. Occurrence sequence of DCM and LBBB was determined by chart reviewing. Diastolic lateral/septal wall thickness ratio (DLSWTR) and lateral wall thickening (LWT) were compared between patients with different time sequences. Response to CRT was analyzed according to medical history and CMR manifestation.

RESULTS

Sixty-three patients were divided into two groups by cluster analysis. DLSWTR and LWT were significantly higher in group 1 (preserved lateral wall thickness and function), compared to those in group 2 (reduced lateral wall thickness and function) (1.06 ± 0.13 vs. 0.8 ± 0.12, 34.57 ± 11.48% vs. 11.18 ± 5.56%, respectively, both P < .001). Occurrence sequence was clear in 14 patients and further analyzed. In group 1, seven patients were clearly having no evidence of DCM when LBBB was first diagnosed (defined as LBBB-precede-DCM) and in group 2, seven patients did not have LBBB when DCM was diagnosed (defined as DCM-precede-LBBB). Among 10 patients who received CRT therapy, all seven patients in group 1 responded well whereas none of three patients in group 2 responded well.

CONCLUSIONS

Occurrence sequence of DCM and LBBB can be discriminated by CMR. Preserved lateral wall morphology and function in CMR suggested LBBB preceded to DCM. Such features may be predictors of good response to CRT.

Time to left ventricular reverse remodeling after cardiac resynchronization therapy: Better late than never

INTRODUCTION

Left ventricular reverse remodeling (LVRR), defined as reduction of end-diastolic and end-systolic dimensions and improvement of ejection fraction, is associated with the prognostic implications of cardiac resynchronization therapy (CRT). The time course of LVRR remains poorly characterized. Nevertheless, it has been suggested that it occurs ≤6 months after CRT.

OBJECTIVE

To characterize the long-term echocardiographic and clinical evolution of patients with LVRR occurring >6 months after CRT and to identify predictors of a delayed LVRR response.

METHODS

A total of 127 consecutive patients after successful CRT implantation were divided into three groups according to LVRR response: Group A, 19 patients (15%) with LVRR after >6 months (late LVRR); Group B, 58 patients (46%) with LVRR before 6 months (early LVRR); and Group C, 50 patients (39%) without LVRR during follow-up (no LVRR).

RESULTS

The late LVRR group was older, more often had ischemic etiology and fewer patients were in NYHA class ≤II. Overall, group A presented LVRR between group B and C. This was also the case with the percentage of clinical response (68.4% vs. 94.8% vs. 38.3%, respectively, p<0.001), and hospital readmissions due to decompensated heart failure (31.6% vs. 12.1% vs. 57.1%, respectively, p<0.001). Ischemic etiology (OR 0.044; p=0.013) and NYHA functional class <III (OR 0.056; p=0.063) were the variables with the highest predictive value for late LVRR.

CONCLUSIONS

Late LVRR has better clinical and echocardiographic outcomes than no LVRR, although with a suboptimal response compared to the early LVRR population. Ischemic etiology and NYHA functional class <III are predictors of late LVRR.

Development of a multiparametric score to predict left ventricular remodelling and prognosis after cardiac resynchronization therapy

AIMS

Optimal delivery of CRT requires appropriate patient selection and device implantation. Echocardiographic predictors of CRT response individually appear to enhance patient selection, but do not fully reflect the complex underlying myocardial dysfunction. We hypothesized that a multiparametric approach would offer greater predictive value and sought to derive a score incorporating baseline characteristics including: dyssynchrony, LV function, and LV lead position.

METHODS AND RESULTS

Data were analysed from 294 patients undergoing CRT between June 2008 and December 2012. All patients were in sinus rhythm with QRS >120 ms, NYHA class II-IV, and LVEF <35%. Detailed clinical assessment including echocardiography was completed at baseline and 6 months after CRT. Response was defined as a ≥15% reduction in LV end-systolic volume. Dyssynchrony (interventricular delay and radial strain delay), global longitudinal strain, and LV lead position were independent predictors of LV remodelling and were used to derive a predictive score which correlated with reduction in LV volume (r = - 0.5, P < 0.001) and was higher with QRS >150 ms and non-ischaemic aetiology. A cut-off score <0.6 offered the highest specificity and positive predictive value (100%) to determine non-response. A score >3.28 offered high specificity (specificity 86%, sensitivity 70%) to predict response. Survival proportion at longer term follow-up was low (21%) in the group with predictive score <0.6.

CONCLUSION

A multiparametric strategy, which defines anticipated probability of response to CRT, offers potential to predict non-responders with poor long-term survival following CRT. The value of this approach in avoiding unnecessary device implantation with potential for harm requires validation in large multicentre studies.

QRS prolongation induced by cardiac resynchronization therapy correlates with deterioration in left ventricular function

BACKGROUND

The benefits of cardiac resynchronization in inducing reverse ventricular remodeling in patients with left ventricular (LV) systolic dysfunction have been well established. Still, up to 30% of the patients fail to derive significant improvement from this therapy. A subset of "nonresponders" experience deterioration in LV function following cardiac resynchronization therapy (CRT). Characteristics of this patient population, however, have not been studied.

OBJECTIVE

To determine characteristics of patients who experience deterioration in LV function following CRT.

METHODS

Clinical, electrocardiographic, and echocardiographic data were collected in 856 consecutive patients presenting for a new CRT device. For inclusion, all patients had an LV ejection fraction '40%, a QRS duration '120 ms, and available baseline and follow-up echocardiograms and electrocardiograms. Deterioration in LV function was defined as an absolute decrease of 5% or greater in ejection fraction from baseline. Multivariate models were constructed to identify variables significantly associated with deterioration.

RESULTS

A total of 507 patients met inclusion criteria, of which 60 (11.8%) met criteria for deterioration. Patients with deterioration were more likely to be men (86.7% vs 66.9%; P = .002), have a non-left bundle branch block morphology (41.7% vs 23.7%; P = .001), and a history of atrial fibrillation (66.7% vs 51.7%; P = .03). On comparing the pre-CRT QRS duration with the first biventricular-paced QRS duration post-CRT implant, it was found that patients with LV deterioration had significant QRS widening than did those without deterioration (ms) (+3.9 ± 34.1 vs -9.0 ± 27.4, P = .007, respectively). In multivariate analysis, QRS widening indexed to the baseline QRS duration was significantly associated with LV deterioration (odds ratio 1.14 [1.06-1.23]; P = .001).

CONCLUSION

QRS widening is associated with deterioration in LV function following CRT.