The myocardial ischemia evaluated by real-time contrast echocardiography may predict the response to cardiac resynchronization therapy: a large animal study.

Yongle Chen,Haohua Yao,Haiyan Chen,Yongshi Wang,Leilei Cheng,Weipeng Zhao,Xianhong Shu,Cuizhen Pan

doi:10.1371/journal.pone.0113992

Abstract

Evidence-based criteria for applying cardiac resynchronization therapy (CRT) in patients with ischemic cardiomyopathy are still scarce. The aim of the present study was to evaluate the predictive value of real-time myocardial contrast echocardiography (RT-MCE) in a preclinical canine model of ischemic cardiomyopathy who received CRT. Ischemic cardiomyopathy was produced by ligating the first diagonal branch in 20 beagles. Dogs were subsequently divided into two groups that were either treated with bi-ventricular pacing (CRT group) or left untreated (control group). RT-MCE was performed at baseline, before CRT, and 4 weeks after CRT. Two-dimensional speckle tracking imaging was used to evaluate the standard deviation of circumferential (Cir12SD), radial (R12SD), and longitudinal (L12SD) strains of left ventricular segments at basal as well as middle levels. Four weeks later, the Cir12SD, R12SD, and myocardial blood flow (MBF) of the treated group were significantly improved compared to their non-CRT counterparts. Furthermore, MBF values measured before CRT were significantly higher in responders than in non-responders to bi-ventricular pacing. Meanwhile, no significant differences were observed between the responder and non-responder groups in terms of Cir12SD, R12SD, and L12SD. A high degree of correlation was found between MBF values before CRT and LVEF after CRT. When MBF value>24.9 dB/s was defined as a cut-off point before CRT, the sensitivity and specificity of RT-MCE in predicting the response to CRT were 83.3% and 100%, respectively. Besides, MBF values increased significantly in the CRT group compared with the control group after 4 weeks of pacing (49.8±15.5 dB/s vs. 28.5±4.6 dB/s, p<0.05). Therefore, we considered that myocardial perfusion may be superior to standard metrics of LV synchrony in selecting appropriate candidates for CRT. In addition, CRT can improve myocardial perfusion in addition to cardiac synchrony, especially in the setting of ischemic cardiomyopathy.

Highlights

Heart failure, a complex clinical syndrome that encompasses a host of abnormalities in cardiac structure and function, is a major public health epidemic that accounts for a high degree of mortality and morbidity worldwide [1]
The left ventricular ejection fraction (LVEF) of dogs in the control group was spontaneously improved after myocardial infarction (MI) and peaked at 45% by 4 weeks after the intervention
Since the LVEF of dogs in the control group was spontaneously improved after MI and peaked at 45% by 4 weeks after the intervention, we defined LVEF >45% was a positive response to cardiac resynchronization therapy (CRT) for the beagles in the bi-ventricular pacing group

Summary

Introduction

A complex clinical syndrome that encompasses a host of abnormalities in cardiac structure and function, is a major public health epidemic that accounts for a high degree of mortality and morbidity worldwide [1]. CRT by means of bi-ventricular pacing can support ventricular contraction, increase cardiac output, relieve heart failure symptoms, improve quality of life of patients, and reduce their overall mortality. Despite these highly encouraging effects, the overall efficacy of CRT is hampered by the fact that approximately 30% of patients who are administered the therapy do not benefit from bi-ventricular pacing and in some cases may exhibit worsening of their heart failure symptoms [3,4,5]. The aim of the present animal study was twofold: (1) to validate that changes in myocardial perfusion may be key factors in predicting the outcome of CRT in the setting of ischemic cardiomyopathy and (2) to explore that CRT can improve myocardial perfusion in this common disease etiology

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