Abstract 2019: Systolic Dyssynchrony is Present in Heart Failure with Narrow or Wide QRS, while Diastolic Dyssynchrony is Present Only in Heart Failure with Wide QRS in a Canine Model of Heart Failure
Background: Assessment of dyssynchrony is important to define the patients who benefit from cardiac resynchronization therapy. We performed this study to define the degree of dyssynchrony throughout systole and diastole in experimental heart failure with narrow versus wide QRS.
Methods :To induce heart failure with wide QRS, mongrel dogs underwent His ablation followed by pacing from RV at intrinsic rate (D group, n=12) and 170 bpm (DHF group, n=8). To induce heart failure with narrow QRS, dogs were paced from the atrium at 190 bpm (HF group, n=9). 4 weeks later, echocardiography was obtained (GE Vigmed, Norway) and radial strain curves were obtained by speckle tracking analysis (EchoPAC PC BTO 5) from six segments of the mid-short axis view. We defined dyssynchrony at various phases of segmental contraction as SD of time to 10, 20, 50, 80 and 100% of peak radial strain. Dyssynchrony at beginning of segmental relaxation was defined as SD of time to achieve 30% of relaxation.
Results: As shown in the graph, D group shows persistent dyssynchrony throughout systole and early diastole, DHF group shows progressive worsening of dyssynchrony from early systole to early diastole. In contrast, HF group shows dyssynchrony throughout systole, but no dyssynchrony in early diastole.
Conclusion: In experimental heart failure with wide QRS, dyssynchrony starts in early systole and persists into diastole while heart failure with narrow QRS shows dyssynchrony only in systole, not in diastole. Future studies are required to define whether this concept is also valid in human heart failure.