Improvement in Regional Contractility of Myocardium after CABG

Lee, Byeong Il; Paeng, Jin Chul; Lee, Dong Soo; Lee, Jae Sung; Chung, June Key; Lee, Myung Chul; Choi, Heung Kook

Abstract

PURPOSE
The maximal elastance (E (max) ) of myocardium has been established as a reliable load-independent contractility index. Recently, we developed a noninvasive method to measure the regional contractility using gated myocardial SPECT and arterial tonometry data. In this study, we measured regional E (max) (rE (max) ) in the patients who underwent coronary artery bypass graft surgery (CABG), and assessed its relationship with other variables. MATERIALS AND METHODS: 21 patients (M: F=17: 4, 58+/-12 y) who underwent CABG were enrolled. (201) Tl rest/ dipyridamole stress (99m) Tc-sestamibi gated SPECT were performed before and 3 months after CABG. For 15 myocardial regions, regional time-elastance curve was obtained using the pressure data of tonometry and the volume data of gated SPECT. To investigate the coupling with myocardial function, preoperative regional E (max) was compared with regional perfusion and systolic thickening. In addition, the correlation between E (max) and viability was assessed in dysfunctional segments (thickening < 20% before CABG). The viability was defined as improvement of postoperative systolic thickening more than 10%. RESULTS: Regional E (max) was slightly increased after CABG from 2.41+/-1.64 (pre) to 2.78+/-1.83 (post) mmHg/mL. E (max) had weak correlation with perfusion and thickening (r=0.35, p< 0.001). In the regions of preserved perfusion (> or=60%), E (max) was 2.65+/-1.67, while it was 1.30+/-1.24 in the segments of decreased perfusion. With regard to thickening, E (max) was 3.01+/-1.92 mmHg/mL for normal regions (thickening > or=40%), 2.40+/-1.19 mmHg/mL for mildly dysfunctional regions (< 40% and > or=20%), and 1.13+/-0.89 mmHg/mL for severely dysfunctional regions (< 20%). E (max) was improved after CABG in both the viable (from 1.27+/-1.07 to 1.79+/-1.48 mmHg/mL) and non-viable segments (from 0.97+/-0.59 to 1.22+/-0.71 mmHg/mL), but there was no correlation between E (max) and thickening improvements (r=0.007). CONCLUSIONS: Preoperative regional E (max) was relatively concordant with regional perfusion and systolic thickening on gated myocardial SPECT. In dysfunctional but viable segments, E (max) was improved after CABG, but showed no correlation with thickening improvement. As a load-independent contractility index of dysfunctional myocardial segments, we suggest that the regional E (max) could be an independent parameter in the assessment of myocardial function.