Relationship between transmural extent of necrosis and quantitative recovery of regional strains after revascularization.

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 > or =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 > or =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.