Detection of stunned myocardium in post-reperfusion cases of acute myocardial infarction

Association between non-perfusion parameters and presence of ischemia in gated-SPECT myocardial perfusion imaging studies

BACKGROUND

Combined assessment of perfusion and function improves diagnostic and prognostic power of gated-SPECT in patients with coronary artery disease. The aim of this study was to investigate whether the presence of stress-induced ischemia is associated with abnormal resting left ventricular (LV) function and intraventricular dyssynchrony.

METHODS AND RESULTS

Gated-SPECT myocardial perfusion imaging (MPI) at rest and 15 min post-stress was performed in 101 patients, who were divided into three groups: those with stress-induced ischemia (Group 1, n = 58), those with normal scans (Group 2, n = 28), and those with scar but no ischemia (Group 3, n = 15). More extensive perfusion defects were found in patients of Groups 1 and 3 [Summed stress score (SSS): 13 ± 8 and 21 ± 9, respectively]. In Group 2, the mean SSS was 1.5. The mean change in LV ejection fraction (LVEF at stress - LVEF at rest) was higher in Group 1 v. Group 2 patients: -5.54% ± 6.24% vs -2.46% ± 5.56%, p = 0.02. Group 3 patients also had higher values, similar to Group 1: -6.47% ± 8.82%. Patients with ischemia had almost 50% higher end-diastolic volumes than patients with normal MPI. Similarly, end-systolic volumes were almost twice as high in this group (p < 0.0001). In addition, the histogram bandwidth, a measure of intraventricular dyssynchrony, was greater in Group 1.

CONCLUSIONS

Baseline differences in left ventricular volumes and degree of dyssynchrony are associated with inducible ischemia on stress testing in a gated-SPECT MPI. Stress-induced ischemia increases the degree of intraventricular dyssynchrony.

Left ventricular dysfunction secondary to ischemia in women with angina and normal coronary angiograms

BACKGROUND

Microvascular disease is proposed as a cause of segmental myocardial blood flow abnormalities and heterogeneous myocardial perfusion in cardiac syndrome X.

OBJECTIVE

To assess if myocardial ischemia can be evidenced through both perfusion abnormalities and poststress left ventricular ejection fraction (LVEF) reduction by gated single photon emission tomography (SPECT) myocardial scintigraphy in women with syndrome X in a similar way to those with epicardial coronary lesions.

METHODS

Three groups of postmenopausal women were studied: group I, 20 women with angina, perfusion defects, and normal coronary angiography; group II, 20 women with epicardial coronary lesions (> or =50% of coronary lumen reduction); group III, 15 volunteers without signs or symptoms of ischemia (control group). Each underwent technetium-99m ((99m)TC) methoxyisobutylisonitrile gated SPECT myocardial scintigraphy (protocol: exercise-stress-rest), brachial artery endothelial function measured by ultrasonography, and lipidogram.

RESULTS

Groups I and III patients had a higher body mass index (BMI). There were more smokers in groups I and II. Very low density lipoprotein cholesterol (VLDL-C) and triglycerides were higher in group II patients. The brachial artery vasodilator responsiveness after 5 minutes of ischemia was similarly lower in patients of groups I and II compared with those of group III (3% vs. 6.5%, respectively; p = 0.03 group III vs. group I and group II). Mean DeltaLVEF (LVEF poststress minus LVEF at rest) was -3.86%, -2.90%, and 4.18% in groups I, II, and III, respectively (p = NS between I and II, p = 0.005 between II and III, and p = 0.003 between I and III). In 43% of group I patients and in 10 of 18 group III patients with perfusion defects, there was a poststress LVEF reduction >5%.

CONCLUSIONS

Stress-induced ischemia is associated with poststress LVEF reduction as a probable manifestation of myocardial stunning in postmenopausal women with typical angina and normal coronary angiography.

Ischemia in women with angina and normal coronary angiograms

BACKGROUND

Coronary artery disease is frequent in postmenopausal women. Myocardial ischemia has been induced with stress testing, and a relationship between endothelial dysfunction and perfusion defects has been reported.

OBJECTIVE

To evaluate whether myocardial ischemia can be evidenced both by perfusion and function abnormalities using gated single-photon emission computed-tomography myocardial scintigraphy with technetium-labeled compounds in women with typical angina, normal coronary angiography, and endothelial dysfunction.

METHODS AND RESULTS

Fifty-nine postmenopausal patients were studied. Each underwent technetium-99m methoxy-isobutyl-isonitrile myocardial scintigraphy (protocol: exercise stress-rest), brachial artery endothelial function measured by ultrasonography, lipidogram, and 24-h ambulatory ECG recording (Holter). Twenty-one patients (group I) showed perfusion defects in myocardial scintigraphy, whereas the other 38 patients (group II) did not. Group I patients exhibited endothelial dysfunction more frequently (57 vs. 29%) than those of group II. Among group I patients, 12 showed a reversible perfusion defect that, in 75% of the cases, was associated with poststress left ventricular ejection fraction reduction greater than 5% and a regional hypokinesis. Nine patients had fixed defects, which in 56% of the cases were associated with poststress left ventricular ejection fraction reduction greater than 5%. Left ventricular ejection fraction poststress minus left ventricular ejection fraction at rest was -5.2% in group I patients versus -1.8% in group II (P<0.001). Three patients in group I showed evidence of ischemia by Holter compared with four in group II.

CONCLUSION

Stress-induced ischemia is associated with poststress left ventricular ejection fraction reduction in postmenopausal women with typical angina, normal coronary angiography, and a trend toward abnormal endothelial-mediated vasodilation.

Clinical implication of reverse redistribution on99mTc-sestamibi images for evaluating ischemic heart disease

OBJECTIVE

The purpose of this study was to clarify the usefulness of 99mTc-sestamibi (MIBI) delayed imaging in the assessment of the severity of myocardial ischemia in patients with coronary artery stenosis.

METHODS

Forty-three angina pectoris with coronary stenosis of greater than 75% were enrolled in this study. Myocardial perfusion SPECT images were obtained 1 and 6 hours after an intravenous injection of MIBI at rest. Stress myocardial perfusion SPECT images were also acquired after the injection of MIBI. And myocardial fatty acid metabolism images were obtained 30 minutes after the injection of BMIPP at rest. Myocardial perfusion SPECT images were divided into 20 segments which were semiquantitatively assessed according to a 4-level defect score scale: score 0 (normal) to score 3 (severely); then the extent score (ES) and severity score (SS) were calculated.

RESULTS

The sensitivity for myocardial ischemia showed the highest rate at 88.3% with MIBI delayed SPECT. According to the coronary angiography findings, MIBI stress SPECT and MIBI delayed SPECT detected the severity and extent of ischemia with more sensitivity than MIBI early SPECT in 12 patients (group A) with stenosis of more than 75% but less than 90% (p < 0.01). Even though MIBI stress SPECT detected the severity and extent of ischemia in 31 patients (group B) with stenosis of more than 90% but less than 100%, there was no significant difference between MIBI stress SPECT and MIBI delayed SPECT. BMIPP SPECT revealed significant differences between group A and group B regarding the severity of myocardial ischemia. MIBI reverse redistribution was observed in 33 patients and no significant difference existed between groups A and B.

CONCLUSIONS

Myocardial washout of MIBI was frequently observed in patients with angina pectoris and the detection accuracy for ischemia was high. MIBI imaging is considered useful for assessment not only of myocardial perfusion but also mitochondrial function. The imagings with BMIPP and delayed MIBI could serve to determine the severity of myocardial ischemia more accurately.