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Relationship Between Transmural Extent of Necrosis and Quantitative Recovery of Regional Strains After Revascularization

Division of Cardiology, Cliniques Universitaires St. Luc, Brussels, Belgium

^_* Reprint requests and correspondence: Dr. Bernhard L. Gerber, Division of Cardiology, Cliniques St. Luc, Université Catholique de Louvain, Av. Hippocrate 10/2803, B-1200 Brussels, Belgium (Email: bernhard.gerber{at}uclouvain.be).

Objectives: To better understand the quantitative relationship of recovery of regional and global dysfunction after revascularization in chronic infarcts with variable transmural extent of necrosis by delayed enhanced cardiac magnetic resonance.

Background: Studies relating transmurality of delayed enhanced magnetic resonance to functional recovery in dysfunctional myocardium using semiquantitative Likert scales have demonstrated the intermediate likelihood (50% probability) of recovery of dysfunction in subendocardial scars.

Methods: Forty-two patients with chronic left ventricular dysfunction due to coronary artery disease underwent tagged and delayed enhanced magnetic resonance before and 10 ± 7 months after revascularization (coronary artery bypass graft: 35, percutaneous transluminal coronary angioplasty: 7). Left ventricular ejection fraction and regional mid-myocardial Eulerian radial thickening strain (Err) and mid-myocardial, subendocardial, and subepicardial Eulerian circumferential shortening strain (Ecc) strains were quantified in 16 segments per patient before and after revascularization and related to pre-operatively measured transmurality of necrosis.

Results: At baseline, 256 of 672 segments were dysfunctional, having <2 SD (i.e., >–10%) mid-myocardial Ecc. The magnitude of recovery of mid-myocardial Ecc (r = –0.33, p < 0.01) was inversely correlated with transmurality of necrosis before revascularization. Segments with <25% necrosis improved mid-myocardial Ecc and Err. No significant improvement of mid-myocardial Ecc or Err occurred when transmurality was 25%. However, subendocardial Ecc improved up to 75% transmural necrosis. Receiver-operator characteristic analysis determined optimal sensitivity (54%) and specificity (82%) for normalization of mid-myocardial Ecc (to <–10% Ecc) at a cutoff value of 18% transmural necrosis. Improvement of left ventricular ejection fraction (from 35 ± 15% to 40 ± 7%, p < 0.001) was best predicted (67% sensitivity, 58% specificity) by the presence of <4.5 dysfunctional segments with <75% transmural necrosis.

Conclusions: The quantitative relationship between necrosis transmurality and improvement of regional and global dysfunction after revascularization is complex. Although improvement of recovery of regional mid-myocardial dysfunction after revascularization was observed only for scarring not exceeding 25% transmurality, global dysfunction significantly improved even when more extensive subendocardial scarring was revascularized.

Key Words: cardiac magnetic resonance • myocardial infarction • myocardial viability • strain

Abbreviations and Acronyms   AUC = area under the receiver-operator characteristic curve   CABG = coronary artery bypass graft   CI = confidence interval   CMR = cardiac magnetic resonance   DE = delayed enhancement   Ecc = Eulerian circumferential shortening strain   EF = ejection fraction   Err = Eulerian radial thickening strain   LV = left ventricle/ventricular   MDCT = multidetector CT

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