Simultaneous assessment of myocardial perfusion and left ventricular function during transient coronary occlusion.

OBJECTIVES: We used technetium-99m sestamibi imaging to evaluate the magnitude of changes in left ventricular function and perfusion and to investigate their interdependence during transient coronary occlusion. BACKGROUND: Transient coronary occlusion during coronary angioplasty provides a unique opportunity for examining the effects of acute myocardial ischemia on left ventricular function and perfusion. METHODS: Thirty-five patients with normal left ventricular function underwent first-pass radionuclide angiography with technetium-99m sestamibi using a multicrystal gamma camera during balloon occlusion of a coronary artery. Single-photon tomography was performed 2.1 +/- 1.7 h later. Subsequently, all scans were repeated at rest. RESULTS: The mean size +/- SD of the perfusion defect during coronary occlusion was 23 +/- 18%, with significantly larger defects observed for occlusions of the left anterior descending coronary artery (39 +/- 20%) than for occlusions of the left circumflex (15 +/- 11%) or right (15 +/- 9%) coronary artery (p < 0.05). The mean change in ejection fraction from recovery to occlusion was -17 +/- 17% and was significantly larger for left anterior descending (-26 +/- 21%) and left circumflex (-15 +/- 11%) than for right (-8 +/- 10%) coronary artery occlusions (p < 0.05). For the entire group, ejection fraction during occlusion correlated significantly with perfusion defect size (r = 0.63, p = 0.0004), whereas the extent of ischemic myocardium correlated with the decrease in ejection fraction (r = 0.69, p = 0.0001). The defects present during occlusion reversed within a few hours. CONCLUSIONS: Changes in left ventricular function and perfusion develop pari passu during coronary occlusion and are more severe when the left anterior descending artery is occluded. Although a significant correlation exists between the extent of the perfusion defect and the severity of the decrease in ejection fraction, there is a substantial individual variation with respect to changes in both myocardial perfusion and ventricular function during acute coronary occlusion.

Use of a rapid assay of subforms of creatine kinase MB to diagnose or rule out acute myocardial infarction.

BACKGROUND: Ruling out myocardial infarction in patients coming to the emergency room with chest pain is hindered by the lack of a specific early diagnostic marker. Less than 30 percent of patients admitted to coronary care units have infarction, resulting in substantial unnecessary expenditures. We developed a rapid assay of the subforms of creatine kinase MB (CK-MB) and prospectively analyzed its sensitivity and specificity in diagnosing myocardial infarction in the first six hours after the onset of chest pain. METHODS: In 1110 consecutive patients who came to the emergency room with chest pain, blood samples were collected every 30 to 60 minutes until at least 6 hours after the onset of symptoms; in patients who were then admitted to the hospital, samples were collected every 4 hours for up to 48 hours. The samples were analyzed for CK-MB subforms, and the diagnosis of myocardial infarction was confirmed by conventional CK-MB analysis. RESULTS: Of the 1110 patients evaluated, 121 had myocardial infarction. The sensitivity of the assay of CK-MB subforms to detect myocardial infarction in the first six hours after the onset of symptoms was 95.7 per cent, as compared with only 48 percent for the conventional CK-MB assay; the specificity was 93.9 percent among patients hospitalized without myocardial infarction and 96.2 percent among those sent home. Among the patients with myocardial infarction, definitive results of the subform assay were available a mean (+/- SD) of 1.22 +/- 1.17 hours after their arrival in the emergency room. CONCLUSIONS: The assay of CK-MB subforms reliably detected myocardial infarction within the first six hours after the onset of symptoms, and its use could reduce admission to the coronary care unit by 50 to 70 percent, thereby reducing costs.