Electrical-mechanical remodeling in left bundle branch block-induced cardiomyopathy：An experimental study

doi:10.3877/cma.j.issn.1672-6448.2024.10.008

Abstract

Abstract:

Objective

To comprehensively evaluate electrical-mechanical remodeling in left bundle branch block-induced cardiomyopathy （LBBB-CM） and deeply investigate its impact on cardiac function using electrocardiographic parameters and left ventricular myocardial work parameters.

Methods

In 14 Beagle dogs，LBBB was induced by radiofrequency ablation under anesthesia. Electrocardiograms and echocardiograms were collected and analyzed before and 12 months after model creation. Seven LBBB dogs and seven healthy adult dogs were randomly selected for cardiac dissection and pathological analysis， and Masson staining was used to analyze the endocardial collagen content. According to their left ventricular injection fraction （LVEF） of LBBB dogs at 12 months after model creation， the experimental dogs were divided into an LVEF-preserved group （LVEF≥50%）and an LVEF-decreased group （LVEF＜50%） to investigate the difference in electrical-mechanical remodeling between the two groups as well as the correlations between electrocardiographic parameters， myocardial work parameters， and cardiac function parameters.

Results

Compared with the baseline values， the left ventricular end-diastolic and end-systolic volumes of the experimental dogs significantly increased （P＜0.01 for all）， while the left ventricular ejection fraction （LVEF） significantly decreased ［baseline （62.05±3.26）% vs 12 months after model creation （49.72±5.93）%， P＜0.001］ at 12 months. The left ventricular global longitudinal strain （GLS）and global myocardial work efficiency （GWE） significantly decreased （P＜0.05）， and the global constructive work （GCW） and global wasted work （GWW） significantly increased （P＜0.001） in LBBB dogs at 12 months compared with the baseline values. Quantitative analysis of endocardial collagen content revealed that the collagen volume fraction （CVF） of the endocardium in each segment of the left ventricle in LBBB dogs was significantly increased compared with that of control dogs （P＜0.05）. Further analysis revealed that the total QRS area in the LVEF-decreased group was significantly larger than that of the LVEF-preserved group ［LVEF-preserved group （665.02±147.44） mV·ms vs LVEF-decreased group （979.05±331.17） mV·ms， P＜0.05］. Compared with the LVEF-preserved group， the left ventricular end-systolic volume （LVESV） significantly increased（P＜0.05）， while the segmental myocardial work index （SMW） of the anteroseptal and ventricular septum and the segmental myocardial work efficiency （SWE） of the ventricular septum significantly decreased in the LVEF-decreased group ［SMW-anteroseptal: LVEF-preserved group （1363.22±495.37） mmHg% vs LVEF-decreased group （557.20±572.07） mmHg%， P=0.02； SMW-septal: LVEF-preserved group （920.78±473.25） mmHg% vs LVEF-decreased group （334.60±324.47） mmHg%， P=0.03； SWE-septal， LVEF-preserved group （83.11±10.33）%vs LVEF-decreased group （61.20±22.68）%， P=0.03］. Significant differences were observed in the segmental wasted work （SWW） of the ventricular septum between the two groups （LVEF-preserved group （325.22±200.96）mmHg% vs LVEF-decreased group （763.60±411.08） mmHg%， P=0.02）. Correlation analysis indicated that the total QRS area was negatively correlated with LVEF （r=-0.67， P＜0.01）. For the segmental myocardial work parameters of septum in the middle segment， SWW was strongly negatively correlated with LVEF （r=-0.78，P＜0.01）， while SWE was moderately positively correlated with LVEF （r=0.64， P=0.01）.

Conclusion

LBBB is not a benign arrhythmia， leading to the occurrence and development of cardiomyopathy. The electrical-mechanical remodeling of the heart induced by LBBB is related to the cardiac dysfunction， accompanied by severe endocardial fibrosis. Septal injury may trigger cardiac dysfunction in LBBB.

Key words: Echocardiography, Left bundle branch block, Ventricular function, left, Myocardial work, QRS complex

Fen Chen, Beibei Ge, Xiaoxian Wang, Mingxia Li, Fang Xu, Jian Shi, Guanjun Guo, Aijuan Fang, Zhongqing Shi, Zhanru Qi, Hui Chen, Jing Yao. Electrical-mechanical remodeling in left bundle branch block-induced cardiomyopathy：An experimental study[J]. Chinese Journal of Medical Ultrasound (Electronic Edition), 2024, 21(10): 978-985.

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URL: https://chaosheng.cma-cmc.com.cn/EN/10.3877/cma.j.issn.1672-6448.2024.10.008

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Figures/Tables 9

References 22

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心电参数	造模前基线	造模后即刻	造模后12个月
QRS时限（ms）	80.83±8.21	125.33±7.44^*	124.93±6.76^*
QRS波总面积（mV·ms）	-	-	777.17±241.18

心电参数	造模前基线	造模后即刻	造模后12个月
QRS时限（ms）	80.83±8.21	125.33±7.44^*	124.93±6.76^*
QRS波总面积（mV·ms）	-	-	777.17±241.18

超声参数	基础状态	LBBB造模后12个月	t值	P值
LVEDV（ml）	19.79±5.32	25.71±7.94	3.71	0.003
LVESV（ml）	7.50±2.10	13.14±4.93	5.05	＜0.001
LVEF（%）	62.05±3.26	49.72±5.93	7.20	＜0.001
GLS（%）	16.44±3.91	12.81±3.77	2.22	0.045
GMW（mmHg%）	865.36±252.61	978.00±257.05	1.13	0.278
GWE（%）	87.43±4.24	80.71±3.63	3.88	0.002
GCW（mmHg%）	1311.14±298.11	1928.71±245.45	5.58	＜0.001
GWW（mmHg%）	150.07±85.00	429.43±101.69	6.81	＜0.001

超声参数	基础状态	LBBB造模后12个月	t值	P值
LVEDV（ml）	19.79±5.32	25.71±7.94	3.71	0.003
LVESV（ml）	7.50±2.10	13.14±4.93	5.05	＜0.001
LVEF（%）	62.05±3.26	49.72±5.93	7.20	＜0.001
GLS（%）	16.44±3.91	12.81±3.77	2.22	0.045
GMW（mmHg%）	865.36±252.61	978.00±257.05	1.13	0.278
GWE（%）	87.43±4.24	80.71±3.63	3.88	0.002
GCW（mmHg%）	1311.14±298.11	1928.71±245.45	5.58	＜0.001
GWW（mmHg%）	150.07±85.00	429.43±101.69	6.81	＜0.001

组别	数量（只）	室间隔	前壁	侧壁	后壁	心尖部
正常对照犬	7	7.69±3.81	19.85±9.14	8.90±2.36	13.06±6.67	8.35±1.44
LBBB犬	7	46.27±13.89	40.88±12.82	33.13±18.56	49.76±12.43	54.13±15.60
t值		7.08	3.06	3.17	3.85	7.12
P值		＜0.001	0.01	0.01	0.01	＜0.001

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