Long-term outcome of a residual scar from myocardial infarction after coronary artery bypass grafting: a 100-month study using myocardial perfusion scintigraphy

Coronary artery disease investigated using 99mTc-tetrofosmin myocardial SPECT

BACKGROUND

Coronary artery disease can be diagnosed from stress and delayed images of myocardial single photon emission computed tomography (SPECT) using technetium-99 m-tetrofosmin (TcTF). However, the negative predictive value of stress SPECT images after a single injection of a low tracer dose remains unknown. Thus, the present study investigates whether normal stress SPECT results predict event-free survival.

MATERIALS AND METHODS

We screened 302 consecutive patients who were randomly assigned to two groups for myocardial ischaemia using either stress SPECT with a low dose of TcTF (296 MBq, TcTF group, n = 150) or stress together with rest SPECT using thallium(201) chloride (TlCl, 111 MBq; TlCl group, n = 152) as the tracer. A total of 80 patients with abnormal SPECT findings were excluded and the remaining 222 with normal results (age, 66.5 +/- 0.7 years; TcTF/TlCl, 112/110) were enrolled in the present study and followed up for 401 +/- 9 days, with the endpoint being ischaemic cardiac events.

RESULTS

The incidence of cardiac events did not differ between the two groups (0.9% and 0.0% in TcTF and TlCl groups, respectively). The cost and duration of TcTF and TlCl SPECT examinations were about 425 and 603 Euros and 50 and 280 min, respectively.

CONCLUSIONS

The negative predictive values of stress SPECT using a low dose of TcTF and of combined stress and rest SPECT using TlCl did not differ and both were clinically acceptable. Thus, stress SPECT using low dose TcTF is useful in screening patients for myocardial ischaemia.

Prognostic Value of Myocardial Perfusion Single-Photon Emission Computed Tomography for the Prediction of Future Cardiac Events in a Japanese Population A Middle-Term Follow-up Study

BACKGROUND

The prognostic value of rest 201Tl/stress (99m)Tc-tetrofosmin myocardial perfusion single-photon emission computed tomography (SPECT) for the prediction of future hard cardiac events, including acute myocardial infarction (AMI), unstable angina (UAP) and cardiac death, and the implications for risk stratification has not yet been defined in a Japanese population.

METHODS AND RESULTS

The 1,988 patients who underwent rest 201Tl/stress (99m)Tc-tetrofosmin SPECT were identified and followed up for the occurrence of AMI, UAP and cardiac death. The mean follow-up interval was 26.9+/-15.8 months. The 142 patients were revascularized within 60 days after SPECT and they were censored from the prognostic analysis. Summed stress score (SSS), summed rest score and summed difference score (SDS) were calculated using a 5-point scoring (Normal: 0, No uptake: 4) and a 20-segment model; 22 cases of myocardial infarction, 31 of UAP and 22 cardiac deaths occurred (1.2%, 1.7% and 1.2%, respectively). Multivariate Cox regression analysis showed that hypertension (Wald 6.37, p<0.05) and SDS (Wald 8.77, p<0.01) were independent predictors of AMI and UAP. Advanced age (Wald 16.0, p<0.001), SSS (Wald 10.9, p<0.01) and SDS (Wald 4.58, p<0.05) were independent predictors of cardiac death.

CONCLUSION

Myocardial perfusion SPECT yields prognostic information toward the identification of acute coronary syndrome and cardiac death.

Medium- to long-term prognostic impact of dipyridamole thallum-201 myocardial single-photon emission computed tomography in elderly patients

Dipyridamole thallium-201 single-photon emission computed tomography (SPECT) has not been extensively evaluated for risk stratification and the medium- to long-term prognostic value in elderly cardiac patients who are unable to exercise. The present study group comprised 210 consecutive patients aged at least 70 years with known or suspected coronary artery disease (CAD). The SPECT findings were classified as a reversible, fixed, or combined (reversible and fixed) defect. Of the 210 patients, 201 (77+/-5 years, 85 male) were successfully followed for 49+/-26 months. Thirteen (7%) patients had cardiac events: cardiac death (n=10), non-fatal myocardial infarction (n=1), or coronary artery bypass grafting (n=2). Cardiac events occurred in 3 of 112 patients with normal SPECT and in 10 of 89 patients with an abnormal scan (0.7% /year vs 2.8% /year, p=0.01). Stepwise Cox regression analysis revealed that the significant predictors of cardiac events were combined defects (relative risk 7.3) and the number of defect areas (relative risk 4.4). The predictive value of dipyridamole thallium-201 SPECT is maintained over 4 years in mixed populations of elderly CAD patients who are unable to exercise.

Beneficial effect of coronary artery bypass grafting as assessed by quantitative gated single-photon emission computed tomography

The development of quantitative gated single-photon emission computed tomography (SPECT) has enabled the assessment of left ventricular perfusion, function and wall thickness in a single examination. Accordingly, the present study used gated SPECT to assess the benefit of coronary artery bypass grafting (CABG) in patients with coronary artery disease; 47 of those patients were evaluated before and 5 months after CABG. As a result of coronary revascularization, a significant improvement was observed in global ejection fraction (50+/-12 --> 53+/-11%; p<0.05). In 107 revascularized territories, the average regional reversible defect score (0.8+/-0.5 --> 0.2 +/-0.3; p<0.0001), average regional perfusion score at rest (0.6+/-0.6 --> 0.3+/-0.4; p<0.0001), average regional wall motion score (0.9+/-0.7 --> 0.7+/-0.5; p<0.05), and end-diastolic wall thickness (8.1+/-1.3 --> 8.6+/-1.5 mm; p<0.0005) all improved significantly. Even in 34 non-revascularized territories, the average regional reversible defect score (0.5+/-0.7 --> 0.2+/-0.5; p<0.03), average regional wall motion score (0.8+/-1.1 --> 0.5 +/-1.0; p<0.03) and end-diastolic wall thickness (8.0+/-1.4 --> 9.1+/-2.0 mm; p<0.03) all improved significantly. These results indicate that improvement in myocardial ischemia, hibernation and left ventricular function with CABG can be assessed in detail with gated SPECT.