Clinical significance of reverse redistribution on resting thallium-201 imaging in patients with vasospastic angina

Non-invasive diagnosis of vasospastic angina

Vasospastic angina (VSA), or variant angina, is an under-recognized cause of chest pain and myocardial infarction, especially in Western countries. VSA leads to a declined quality of life and is associated with increased morbidity and mortality. Currently, the diagnosis of VSA relies on invasive testing that requires the direct intracoronary administration of ergonovine or acetylcholine. However, invasive vasoreactivity testing is underutilized. Several non-invasive imaging alternatives have been proposed to screen for VSA. This review aims to discuss the strengths and limitations of available non-invasive imaging tests for vasospastic angina.

Clinical usefulness of myocardial scintigraphy in patients with vasospastic angina

BACKGROUND

Myocardial scintigraphy is defined as class IIb in the Japanese Circulation Society guideline for diagnosis of vasospastic angina (VSA). However, Caucasian guidelines had no classification of cardiac scintigraphy for diagnosis of VSA.

OBJECTIVES

To clarify the clinical usefulness of myocardial scintigraphy, we analyzed the sensitivity and specificity of each cardiac scintigraphy.

METHODS

We extracted the 136 papers of myocardial scintigraphy from the PubMed database from 1980 to 2018 in patients with VSA. Finally we analyzed the 88 papers including 33 papers of^201-thallium (Tl), 10 papers of ¹²³I beta-methyl 15-para-iodophenyl 3(R, S)-methylpentadecanoic acid (BMIPP), 9 papers of ¹²³I-metaiodobenzylguanidine (MIBG), 4 papers of ^99mTc-sestamibi (MIBI: methoxy-isobutyl-isonitrile), and 2 papers of tetrofosmin to investigate the sensitivity and specificity of each tracer.

RESULTS

Tl, BMIPP, or MIBG cardiac scintigraphy were useful to diagnose patients with VSA, because sensitivity was 57-73%. Specificity was 55-83%. Sensitivity of left circumflex artery was significantly lower than other vessels. BMIPP imaging may be helpful for clinical course of VSA. However, myocardial scintigraphic abnormal findings may not always show the ischemic memory due to coronary artery spasm.

CONCLUSIONS

Recent cardiologists do not perform hyperventilation tests or MIBG scintigraphy for diagnosis of coronary spasm. After understanding the flow of the times, cardiologists should use Tl or BMIPP myocardial scintigraphy for VSA as one of supplementary tools in the real world.

Investigation of the mechanism of reverse redistribution in thallium-201 myocardial perfusion scintigraphy in patients with suspicion for coronary artery spasm

BACKGROUND

Reverse redistribution (RR) is one of the features on myocardial perfusion scintigraphy (MPS) in patients with coronary artery spasm (CAS). This study was aimed to explore the mechanism of RR in patients with suspicion for CAS.

METHODS AND RESULTS

Thirty patients with RR and suspicion for CAS but without coronary artery stenosis (RR group) and 32 control patients without RR (control group) underwent coronary angiography before and after a dipyridamole administration. Coronary blood flow velocity and myocardial perfusion, as determined by corrected thrombolysis in myocardial infarction (TIMI) frame count (CTFC) and TIMI myocardial perfusion grade (TMPG), were measured. Coronary angiography showed significantly slower blood flow velocity [CTFC (37 ± 6) frame vs (29 ± 7) frame, P < .01] and lower myocardial perfusion [TMPG (2.08 ± 0.38) grade vs (2.55 ± 0.33) grade, P < .05] in RR-related arteries than in RR-unrelated arteries in the RR group. But, there was no significant difference among different coronary artery branches in the control group. After the injection of dipyridamole, CTFC decreased and TMPG increased in the RR group. The decline in CTFC and the increase in TMPG in RR-related arteries were more significant than those in RR-unrelated ones (28% vs 14% and 45% vs 16%, respectively; both P < .01). The endothelin-1/nitric oxide (NO) ratio was significantly higher in the RR group than in the control group before the injection of dipyridamole (2.79 ± 0.37 vs 1.70 ± 0.19, P < .01). After the injection of dipyridamole, the ratio went down in both groups, but the decline was statistically significant in the RR group (2.42 ± 0.33, P < .05) but not in the control group (1.42 ± 0.19, P < .05). Pearson correlation analysis showed that there was a positive correlation between summed rest scores on MPS and the endothelin-1/NO ratio (r = 0.853, P = .000) as well as CTFC (r = 0.808, P = .000) before the injection of dipyridamole in the RR group.

CONCLUSION

Patients with suspicion for CAS may exhibit a mild spasm of RR-related arteries and corresponding microvasculature and a significant imbalance of coronary blood flow velocity and myocardial perfusion at rest between RR-related and RR-unrelated areas. This is overcome by stress-induced hyperemic flow increases and which may account for RR on MPS.

Diabetes mellitus impairs myocardial oxygen metabolism even in non-infarct-related areas in patients with acute myocardial infarction

BACKGROUND

Although diabetes is associated with poor clinical outcomes after acute myocardial infarction, to date there have been no reports focusing on the myocardial oxygen metabolism in these patients. Thus, we evaluated the myocardial oxygen metabolism in patients with and without diabetes suffering from acute myocardial infarction using carbon-11 acetate positron emission tomography.

METHODS

20 patients (13 diabetic patients [group A] and 7 non-diabetic patients [group B]) underwent carbon-11 acetate positron emission tomography soon after the onset of acute myocardial infarction. The myocardial oxygen metabolism was evaluated within the infarct-related area and in the non infarct-related area. 6 healthy volunteers (group C) and 6 diabetic patients without coronary artery disease (group D) also participated as controls.

RESULTS

There were no significant differences in gender, age, infarct-related artery, peak level of serum creatine phosphokinase, left-ventricular ejection fraction at onset, or the defect severity on myocardial perfusion images between group A and group B. In group A, the clearance rate (Kmono) of carbon-11 acetate in infarct-related area (0.042+/-0.010) was not significantly different from that in group B (0.049+/-0.016). In contrast, Kmono in non infarct-related area in group A (0.059+/-0.010) was significantly lower than that in group B (0.076+/-0.009; p=0.002), group C (0.072+/-0.004; p=0.026) and group D (0.078+/-0.005; p=0.001).

CONCLUSIONS

These data indicate that the myocardial oxygen metabolism even in non infarct-related area in diabetic patients was impaired after the onset of acute myocardial infarction.