Mechanisms of right ventricular electromechanical dyssynchrony and mechanical inefficiency in children after repair of tetralogy of fallot.
BACKGROUND
Right bundle branch block and right ventricular (RV) dysfunction are common after tetralogy of Fallot repair (rTOF). We hypothesized that right bundle branch block is associated with specific RV mechanical dyssynchrony and inefficient contraction.


RESULTS
We studied rTOF children and age-matched controls. QRS duration and morphology were assessed. RV mechanical dyssynchrony, indicated by early septal activation (right-sided septal flash), RV lateral wall prestretch/late contraction, postsystolic shortening, and intraventricular delay were analyzed using 2-dimensional strain echocardiography. Peak oxygen consumption reflected exercise capacity. Pulmonary regurgitation and RV volumes were assessed by MRI. Forty-six rTOF patients and 46 controls were studied. Ninety-three percent of rTOF patients demonstrated a right-sided septal flash with simultaneous RV basal lateral wall prestretch/late activation. The RV basal segment was the most delayed in onset (115 [0-194] versus 35 [0-96] ms) and termination (462 [369-706] versus 412 [325-529] ms) of longitudinal shortening, with postsystolic shortening. QRS duration correlated with RV basal time to onset and peak shortening (P<0.05). Intra-RV delay was higher in rTOF (P<0.05) in association with RV dilatation (r=0.33; P=0.04). In rTOF, RV mechanics were inefficient, with prestretch and postsystolic shortening comprising 15±11% and 16±9% of total shortening, respectively. A composite parameter of electric and mechanical dyssynchrony correlated with RV end-diastolic volume (r=0.39; P=0.03).


CONCLUSIONS
Typical electromechanical dyssynchrony associated with mechanical inefficiency, regional dysfunction, and RV dilatation is common in rTOF children, possibly contributing to progressive RV dysfunction. The potential of cardiac resynchronization in appropriate patients requires further study.
From the Division of Pediatric Cardiology, The Labatt Family Heart Center, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada (W.H., C.S., A.D., L.M., M.K.F.); and Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona, Spain (B.B.).
Wei
W
Hui
From the Division of Pediatric Cardiology, The Labatt Family Heart Center, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada (W.H., C.S., A.D., L.M., M.K.F.); and Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona, Spain (B.B.).
Cameron
C
Slorach
From the Division of Pediatric Cardiology, The Labatt Family Heart Center, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada (W.H., C.S., A.D., L.M., M.K.F.); and Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona, Spain (B.B.).
Andreea
A
Dragulescu
From the Division of Pediatric Cardiology, The Labatt Family Heart Center, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada (W.H., C.S., A.D., L.M., M.K.F.); and Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona, Spain (B.B.).
Luc
L
Mertens
From the Division of Pediatric Cardiology, The Labatt Family Heart Center, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada (W.H., C.S., A.D., L.M., M.K.F.); and Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona, Spain (B.B.).
Bart
B
Bijnens
From the Division of Pediatric Cardiology, The Labatt Family Heart Center, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada (W.H., C.S., A.D., L.M., M.K.F.); and Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona, Spain (B.B.). mark.friedberg@sickkids.ca.
Mark K
MK
Friedberg
D001696:Biomechanical Phenomena; D002037:Bundle-Branch Block / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D002648:Child; D015150:Echocardiography, Doppler; D004562:Electrocardiography; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000503:physiopathology*; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D011183:Postoperative Complications; D011379:Prognosis; D011446:Prospective Studies; D012372:ROC Curve; D013771:Tetralogy of Fallot / Q000601:surgery*; D018497:Ventricular Dysfunction, Right / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology
bundle-branch block; heart ventricles; tetralogy of Fallot