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Ejection fraction in left bundle branch block is disproportionately reduced in relation to amount of myocardial scar

Axelsson, Jimmy; Wieslander, Björn; Jablonowski, Robert LU ; Klem, Igor; Nijveldt, Robin; Schelbert, Erik B.; Sörensson, Peder; Sigfridsson, Andreas; Chaudhry, Uzma LU and Platonov, Pyotr G. LU , et al. (2018) In Journal of Electrocardiology 51(6). p.1071-1076
Abstract

Introduction: The relationship between left ventricular (LV) ejection fraction (EF) and LV myocardial scar can identify potentially reversible causes of LV dysfunction. Left bundle branch block (LBBB) alters the electrical and mechanical activation of the LV. We hypothesized that the relationship between LVEF and scar extent is different in LBBB compared to controls. Methods: We compared the relationship between LVEF and scar burden between patients with LBBB and scar (n = 83), and patients with chronic ischemic heart disease and scar but no electrocardiographic conduction abnormality (controls, n = 90), who had undergone cardiovascular magnetic resonance (CMR) imaging at one of three centers. LVEF (%) was measured in CMR cine images.... (More)

Introduction: The relationship between left ventricular (LV) ejection fraction (EF) and LV myocardial scar can identify potentially reversible causes of LV dysfunction. Left bundle branch block (LBBB) alters the electrical and mechanical activation of the LV. We hypothesized that the relationship between LVEF and scar extent is different in LBBB compared to controls. Methods: We compared the relationship between LVEF and scar burden between patients with LBBB and scar (n = 83), and patients with chronic ischemic heart disease and scar but no electrocardiographic conduction abnormality (controls, n = 90), who had undergone cardiovascular magnetic resonance (CMR) imaging at one of three centers. LVEF (%) was measured in CMR cine images. Scar burden was quantified by CMR late gadolinium enhancement (LGE) and expressed as % of LV mass (%LVM). Maximum possible LVEF (LVEFmax) was defined as the function describing the hypotenuse in the LVEF versus myocardial scar extent scatter plot. Dysfunction index was defined as LVEFmax derived from the control cohort minus the measured LVEF. Results: Compared to controls with scar, LBBB with scar had a lower LVEF (median [interquartile range] 27 [19–38] vs 36 [25–50] %, p < 0.001), smaller scar (4 [1–9] vs 11 [6–20] %LVM, p < 0.001), and greater dysfunction index (39 [30–52] vs 21 [12–35] % points, p < 0.001). Conclusions: Among LBBB patients referred for CMR, LVEF is disproportionately reduced in relation to the amount of scar. Dyssynchrony in LBBB may thus impair compensation for loss of contractile myocardium.

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@article{495f11b2-7bf1-4775-a5d9-f4dc32c69f4b,
  abstract     = {<p>Introduction: The relationship between left ventricular (LV) ejection fraction (EF) and LV myocardial scar can identify potentially reversible causes of LV dysfunction. Left bundle branch block (LBBB) alters the electrical and mechanical activation of the LV. We hypothesized that the relationship between LVEF and scar extent is different in LBBB compared to controls. Methods: We compared the relationship between LVEF and scar burden between patients with LBBB and scar (n = 83), and patients with chronic ischemic heart disease and scar but no electrocardiographic conduction abnormality (controls, n = 90), who had undergone cardiovascular magnetic resonance (CMR) imaging at one of three centers. LVEF (%) was measured in CMR cine images. Scar burden was quantified by CMR late gadolinium enhancement (LGE) and expressed as % of LV mass (%LVM). Maximum possible LVEF (LVEFmax) was defined as the function describing the hypotenuse in the LVEF versus myocardial scar extent scatter plot. Dysfunction index was defined as LVEFmax derived from the control cohort minus the measured LVEF. Results: Compared to controls with scar, LBBB with scar had a lower LVEF (median [interquartile range] 27 [19–38] vs 36 [25–50] %, p &lt; 0.001), smaller scar (4 [1–9] vs 11 [6–20] %LVM, p &lt; 0.001), and greater dysfunction index (39 [30–52] vs 21 [12–35] % points, p &lt; 0.001). Conclusions: Among LBBB patients referred for CMR, LVEF is disproportionately reduced in relation to the amount of scar. Dyssynchrony in LBBB may thus impair compensation for loss of contractile myocardium.</p>},
  author       = {Axelsson, Jimmy and Wieslander, Björn and Jablonowski, Robert and Klem, Igor and Nijveldt, Robin and Schelbert, Erik B. and Sörensson, Peder and Sigfridsson, Andreas and Chaudhry, Uzma and Platonov, Pyotr G. and Borgquist, Rasmus and Engblom, Henrik and Strauss, David G. and Arheden, Håkan and Atwater, Brett D. and Ugander, Martin},
  issn         = {0022-0736},
  keyword      = {Left bundle branch block,Left ventricular ejection fraction,Magnetic resonance imaging,Myocardial scarring},
  language     = {eng},
  number       = {6},
  pages        = {1071--1076},
  publisher    = {Elsevier},
  series       = {Journal of Electrocardiology},
  title        = {Ejection fraction in left bundle branch block is disproportionately reduced in relation to amount of myocardial scar},
  url          = {http://dx.doi.org/10.1016/j.jelectrocard.2018.09.009},
  volume       = {51},
  year         = {2018},
}