Assessment of left ventricular mechanical dyssynchrony in left bundle branch block canine model: Comparison between cine and tagged MRI

2016 ◽  
Vol 44 (4) ◽  
pp. 956-963 ◽  
Author(s):  
Salvatore Saporito ◽  
Hans C. van Assen ◽  
Patrick Houthuizen ◽  
Jean-Paul M.M. Aben ◽  
Marc Strik ◽  
...  
Keyword(s):  
Left Bundle Branch Block ◽  
Model Comparison ◽  
Canine Model ◽  
Mechanical Dyssynchrony ◽  
Left Ventricular ◽  
Tagged Mri ◽  
Bundle Branch Block ◽  
Left Ventricular Mechanical Dyssynchrony

Mechanism of prolonged electromechanical delay in late activated myocardium during left bundle branch block

2011 ◽  
Vol 301 (6) ◽  
pp. H2334-H2343 ◽  
Author(s):  
Kristoffer Russell ◽  
Otto A. Smiseth ◽  
Ola Gjesdal ◽  
Eirik Qvigstad ◽  
Per Andreas Norseng ◽  
...  
Keyword(s):  
Papillary Muscle ◽  
Left Bundle Branch Block ◽  
Biventricular Pacing ◽  
Lateral Wall ◽  
Mechanical Dyssynchrony ◽  
Left Ventricular ◽  
Electromechanical Delay ◽  
Bundle Branch Block ◽  
Experimental Findings

During left bundle branch block (LBBB), electromechanical delay (EMD), defined as time from regional electrical activation (REA) to onset shortening, is prolonged in the late-activated left ventricular lateral wall compared with the septum. This leads to greater mechanical relative to electrical dyssynchrony. The aim of this study was to determine the mechanism of the prolonged EMD. We investigated this phenomenon in an experimental LBBB dog model ( n = 7), in patients ( n = 9) with biventricular pacing devices, in an in vitro papillary muscle study ( n = 6), and a mathematical simulation model. Pressures, myocardial deformation, and REA were assessed. In the dogs, there was a greater mechanical than electrical delay (82 ± 12 vs. 54 ± 8 ms, P = 0.002) due to prolonged EMD in the lateral wall vs. septum (39 ± 8 vs.11 ± 9 ms, P = 0.002). The prolonged EMD in later activated myocardium could not be explained by increased excitation-contraction coupling time or increased pressure at the time of REA but was strongly related to dP/d t at the time of REA ( r = 0.88). Results in humans were consistent with experimental findings. The papillary muscle study and mathematical model showed that EMD was prolonged at higher dP/d t because it took longer for the segment to generate active force at a rate superior to the load rise, which is a requirement for shortening. We conclude that, during LBBB, prolonged EMD in late-activated myocardium is caused by a higher dP/d t at the time of activation, resulting in aggravated mechanical relative to electrical dyssynchrony. These findings suggest that LV contractility may modify mechanical dyssynchrony.

Left ventricular resynchronization therapy in a canine model of left bundle branch block

2002 ◽  
Vol 282 (6) ◽  
pp. H2238-H2244 ◽  
Author(s):  
Lili Liu ◽  
Bruce Tockman ◽  
Steven Girouard ◽  
Joseph Pastore ◽  
Greg Walcott ◽  
...  
Keyword(s):  
Left Bundle Branch Block ◽  
Wall Motion ◽  
Normal Sinus Rhythm ◽  
Posterior Wall ◽  
Canine Model ◽  
Left Ventricular ◽  
Pressure Derivative ◽  
Bundle Branch Block ◽  
Normal Sinus ◽  
Before And After

Positive responses to left (LV) and biventricular (BV) stimulation observed in heart failure patients with left bundle branch block (LBBB) suggest a possible mechanism of LV resynchronization. An anesthetized canine LBBB model was developed using radio frequency ablation. Before and after ablation, LV pressure derivative over time (dP/d t) and aortic pulse pressure (PP) were assessed during normal sinus rhythm with right ventricle (RV), LV, or BV stimulation combined with four atrioventricular delays in six dogs. In three more dogs, M-mode echocardiograms of septal and LV posterior wall motion were obtained before and after LBBB and during LV stimulation. LBBB caused QRS widening and hemodynamics deterioration. Before ablation, stimulation alone worsened LV dP/d t and PP. After ablation, LV and BV stimulation maximally increased LV dP/d t by 16% and PP by 7% ( P < 0.001), whereas little improvement was observed during RV stimulation. M-mode echocardiogram showed that LBBB resulted in a paradoxical septal wall motion that was corrected by LV stimulation. In conclusion, LV and BV stimulation improved cardiac function in a canine LBBB model via resynchronization of LV excitation and contraction.

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