Mechanical discoordination rather than dyssynchrony predicts reverse remodeling upon cardiac resynchronization

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 295; no. 2; pp. H640 - H646
• Main Authors: Kirn, Borut, Jansen, Annemieke, Bracke, Frank, van Gelder, Berry, Arts, Theo, Prinzen, Frits W
• Format: Journal Article
• Language: English
• Published: United States 01.08.2008
• Subjects: Aged; Cardiac Pacing, Artificial; Case-Control Studies; Feasibility Studies; Female; Heart Failure - pathology; Heart Failure - physiopathology; Heart Failure - therapy; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Models, Cardiovascular; Myocardial Contraction; Patient Selection; Stress, Mechanical; Stroke Volume; Time Factors; Treatment Outcome; Ventricular Function, Left; Ventricular Remodeling
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00106.2008

1 Institute of Physiology, School of Medicine, University of Ljubljana, Slovenia; 2 Department of Cardiology, Catharina Hospital, Eindhoven; and 3 Department of Biomedical Engineering, and 4 Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands Submitted 31 January 2008 ; accepted in final form 27 May 2008 By current guidelines a considerable part of the patients selected for cardiac resynchronization therapy (CRT) do not respond to the therapy. We hypothesized that mechanical discoordination [opposite strain within the left ventricular (LV) wall] predicts reversal of LV remodeling upon CRT better than mechanical dyssynchrony. MRI tagging images were acquired in CRT candidates ( n = 19) and in healthy control subjects ( n = 9). Circumferential strain ( cc ) was determined in 160 regions. From cc signals we derived 1 ) an index of mechanical discoordination [internal stretch fraction (ISF), defined as the ratio of stretch to shortening during ejection] and 2 ) indexes of mechanical dyssynchrony: the 10–90% width of time to onset of shortening, time to peak shortening, and end-systolic strain. LV end-diastolic volume (LVEDV), end-systolic volume (LVESV), and ejection fraction (LVEF) were determined before and after 3 mo of CRT. Responders were defined as those patients in whom LVESV decreased by >15%. In responders ( n = 10), CRT increased LVEF and decreased LVEDV and LVESV (11 ± 6%, 21 ± 16%, and 30 ± 16%, respectively) significantly more ( P < 0.05) than in nonresponders (1 ± 6%, 3 ± 4%, and 5 ± 10%, respectively). Among mechanical indexes, only ISF was different between responders and nonresponders (0.53 ± 0.25 vs. 0.31 ± 0.16; P < 0.05). In patients with ISF >0.4 ( n = 10), LVESV decreased by 31 ± 18% vs. 5 ± 11% in patients with ISF <0.4 ( P < 0.05). We conclude that mechanical discoordination, as estimated from ISF, is a better predictor of reverse remodeling after CRT than differences in time to onset and time to peak shortening. Therefore, discoordination rather than dyssynchrony appears to reflect the reserve contractile capacity that can be recruited by CRT. resynchronization therapy; cardiac mechanics Address for reprint requests and other correspondence: B. Kirn, Univ. of Maastricht, Dept. of Biomedical Engineering, Cardiovascular Research Inst. Maastricht, Maastricht, The Netherlands (e-mail: borut.kirn{at}bf.unimaas.nl )