Mahmarian, John J.

Backgrounds: Role of coronary artery calcium score (CACS) in acute chest pain patients is currently not well defined. The objective of this study was to investigate the prognostic value of CACS obtained by noncontrast electrocardiogram-gated CT in acute chest pain patients suspected for cardiac origin in emergency department. Methods: We search Pubmed, Embase, Cochrane databases for longitudinal studies of CACS in acute chest pain patients without known coronary artery disease (CAD) in emergency department which reported major adverse cardiovascular events (MACE), consisting of death, nonfatal myocardial infarction (NFMI), revascularization or stroke. Pooled annualized event rate, risk ratios and 95% confidence intervals (CI) were analyzed. A random-effect, generic inverse variance model was used. Result: Eight studies evaluated 3556 patients (mean age = 51 years, 47% men) with the pooled prevalence of hypertension, diabetes mellitus, dyslipidemia and smoking of 42%, 16%, 33% and 33% respectively. During a median follow-up of 5 months (range 1-60 months, 37234 patient-months), the overall pooled MACE rate was 7.6%/y. The pooled event rate of MACE for CACS=0 versus CACS>0 was 0.8%/y (13 events in 18874 patient-months) versus 14.6%/y (224 events in 18360 patient-months). The pooled risk ratio with CACS=0 was 0.04 (95% CI: 0.02-0.07, p<0.001) for MACE compared to CACS>0. The sensitivity, specificity, positive and negative predictive value, positive and negative likelihood ratio of CACS for MACE was 94.5%, 64.1%, 15.8%, 99.4%, 2.63 and 0.09 respectively. The heterogeneity among studies was low with an I 2 of 13%. Conclusion: In acute-chest-pain patients without known CAD presenting to emergency department, MACE was rare in those with CACS=0. Zero CACS by noncontrast electrocardiogram-gated CT in this population has high negative predictive value (>99%) for subsequent cardiac events.

99mTc-hexakis-2-methoxy-2-methylpropyl-isonitrile (Tc-Sestamibi), a new myocardial perfusion radiopharmaceutical, was injected intravenously in 11 patients within 4 hours of the onset of acute myocardial infarction before treatment with intravenous tissue-type plasminogen activator and 6-14 days later. Five patients with acute myocardial infarction who did not receive intravenous thrombolytic therapy underwent a similar injection of radiopharmaceutical. The absence of redistribution of Tc-Sestamibi permitted imaging with single-photon emission computed tomography up to 6 hours after intravenous injection to assess the distribution of myocardial perfusion at the time of administration. The region of hypoperfused myocardium on the initial images varied widely from 9% to 68% of the left ventricle and was significantly greater in anterior than in inferior infarcts (p less than 0.01). The region of hypoperfused myocardium on the final images varied widely from 0% to 63% of the left ventricle and was also greater in anterior infarcts (p less than 0.01). The final hypoperfused region correlated (r = -0.82) with the late resting ejection fraction and with the late regional wall motion score in the infarct segment for both anterior (r = -0.74) and inferior (r = -0.97) infarcts. There was a significant decrease (-13 +/- 11%, p less than 0.003) in the extent of hypoperfused myocardium between the initial and final studies in the patients who received thrombolytic therapy compared with an insignificant increase (4 +/- 6%, p greater than 0.5) in the patients who did not receive thrombolytic therapy. Tomographic imaging with Tc-Sestamibi permits determination of the amount of hypoperfused myocardium "at risk" in acute myocardial infarction. The change in myocardial perfusion determined by Tc-Sestamibi before and after therapy in acute myocardial infarction is a promising tool for assessing treatment.