Twenty-four-hour quantitative thallium imaging for predicting beneficial revascularization

Impaired coronary flow reserve is the most important marker of viable myocardium in the myocardial segment-based analysis of dual-isotope gated myocardial perfusion single-photon emission computed tomography

OBJECTIVE

The aim of this study was to investigate the most robust predictor of myocardial viability among stress/rest reversibility (coronary flow reserve [CFR] impairment), (201)Tl perfusion status at rest, (201)Tl 24 hours redistribution and systolic wall thickening of (99m)Tc-methoxyisobutylisonitrile using a dual isotope gated myocardial perfusion single-photon emission computed tomography (SPECT) in patients with coronary artery disease (CAD) who were re-vascularized with a coronary artery bypass graft (CABG) surgery.

MATERIALS AND METHODS

A total of 39 patients with CAD was enrolled (34 men and 5 women), aged between 36 and 72 years (mean 58 ± 8 standard in years) who underwent both pre- and 3 months post-CABG myocardial SPECT. We analyzed 17 myocardial segments per patient. Perfusion status and wall motion were semi-quantitatively evaluated using a 4-point grading system. Viable myocardium was defined as dysfunctional myocardium which showed wall motion improvement after CABG.

RESULTS

The left ventricular ejection fraction (LVEF) significantly increased from 37.8 ± 9.0% to 45.5 ± 12.3% (p < 0.001) in 22 patients who had a pre-CABG LVEF lower than 50%. Among 590 myocardial segments in the re-vascularized area, 115 showed abnormal wall motion before CABG and 73.9% (85 of 115) had wall motion improvement after CABG. In the univariate analysis (n = 115 segments), stress/rest reversibility (p < 0.001) and (201)Tl rest perfusion status (p = 0.024) were significant predictors of wall motion improvement. However, in multiple logistic regression analysis, stress/rest reversibility alone was a significant predictor for post-CABG wall motion improvement (p < 0.001).

CONCLUSION

Stress/rest reversibility (impaired CFR) during dual-isotope gated myocardial perfusion SPECT was the single most important predictor of wall motion improvement after CABG.

Detection of viability after myocardial infarction: available techniques and clinical relevance--a review

The differentiation of viable from nonviable myocardium in patients with myocardial infarction (MI) and left ventricular (LV) dysfunction is of important clinical relevance. It is now known that impaired LV function after infarction not always represents an irreversible process. LV ejection fraction is significantly reduced in many patients after infarction and, although abnormally contracting myocardial segments may result from irreversible scarring, numerous studies have shown that many asynergic zones have sustained metabolic activity. An accurate detection of myocardial viability aids in clinical decision making to select the appropriate therapy for patients with MI. Recently, cardiac imaging techniques that evaluate myocardial viability on the basis of myocardial perfusion, cell membrane integrity, metabolic activity and residual coronary reserve, have been developed with clinical success. These methods provide greater precision in the assessment of viable myocardium than can be achieved by analysis or coronary anatomy, regional function or the presence or absence of electrocardiographic Q waves, criteria that were used in the past. The clinical challenge is to predict which myocardial regions are viable and will improve systolic function after revascularization, thereby enhancing global LV function. In this review, the currently available imaging techniques for assessment of myocardial viability are discussed.