Abnormal 201Tl myocardial single photon emission computed tomography in energetic male patients with myocardial bridge

Case report: A fatal case of myocardial infarction due to myocardial bridge and concomitant vasospasm: the role of stress gated SPECT

Introduction

Although most cases of myocardial bridge (MB) are clinically benign, sometimes it can be one of potential threats of myocardial infarction (MI) and life-threatening arrhythmia. In the present study, we present a case of ST-segment elevation MI caused by MB and concomitant vasospasm.

Case Presentation

A 52-year-old woman was brought to our tertiary hospital due to resuscitated cardiac arrest. Because the 12-lead electrocardiogram indicated ST-segment elevation MI, coronary angiogram was promptly commenced, which showed near-total occlusion at the middle portion of left anterior descending coronary artery (LAD). After intracoronary nitroglycerin administration, this occlusion was dramatically relieved, however, systolic compression at this site remained, indicative of myocardial bridge (MB). Intravascular ultrasound also showed eccentric compression with a "half-moon" sign, which is consistent with MB. Coronary computed tomography also showed a bridged coronary segment surrounded by myocardium at the middle portion of LAD. To assess the severity and extent of myocardial damages and ischemia, myocardial single photon emission computed tomography (SPECT) was additionally conducted, showing a moderate fixed perfusion defect around the cardiac apex, suggesting MI. After receiving optimal medical therapy, the patient's clinical symptoms and signs were improved then the patient was discharged from the hospital successfully and uneventfully.

Conclusion

We demonstrated a case of MB-induced ST-segment elevation MI which was confirmed with its perfusion defects via myocardial perfusion SPECT. There have been proposed a number of diagnostic modalities to examine its anatomic and physiologic significance. Among them, myocardial perfusion SPECT can be available as one of useful modalities to evaluate the severity and extent of myocardial ischemia in patients with MB.

Role of 99mTc-sestamibi gated SPECT/CT myocardial perfusion imaging in the management of patients with myocardial bridging and its correlation with coronary angiography

Myocardial bridging (MB)-a congenital coronary abnormality in its severe form leads to myocardial edema, fibrosis, and ischemia due to coronary artery compression during systole and early part of the diastole. This study evaluated the hemodynamic significance of MB by detecting severity and extent of perfusion abnormality using ^99mTc-sestamibi (MIBI) gated single photon emission computed tomography (SPECT)/CT myocardial perfusion imaging (MPI), its correlation with coronary angiography and role in patient's management. Five patients with complaints of atypical chest pain, exertional angina, or dyspnea underwent stress/rest ^99mTc-MIBI SPECT/CT MPI. The gated stress and rest SPECT/CT images on 17 segment model using quantitative gated-SPECT (QGS) softwarewere analyzed and compared with coronary angiography. Four out of five patients showed reversible perfusion defect in the left anterior descending (LAD) territory segments involved with myocardial bridging (3 patients had already proven MB; while MB was detected in 1 patient after MPI). The fifth patient with MB in the distal LAD revealed normal myocardial perfusion. All the patients were conservatively managed either due to small reversible perfusion defects or normal study except one patient. The gated SPECT/CT MPI of five patients with MB in the present study revealed their perfusion status, information on myocardial wall thickening, contractility, and ejection fraction. <Learning objective: Myocardial bridging may be one of the underlying causes for angina or sudden death even in absence of cardiovascular risk factors. The proven or clinical suspicious myocardial bridging in patients with typical/atypical chest pain and low probability of atherosclerosis should be evaluated with gated SPECT/CTMPI. It helps in detection of coronary artery disease along with severity and extent of myocardial ischemia for their further management.>.

Exercise-Induced Repolarization Changes in Patients with Isolated Myocardial Bridging

BACKGROUND

Although myocardial bridging (MB) is defined as an angiographic phenomenon with a benign course, it has also been associated with adverse cardiovascular events. The effects of exercise on myocardial repolarization in patients with MB were tested in this study, with Tp-e and Tp-e/QT repolarization indexes.

MATERIAL AND METHODS

A total of 50 patients in whom isolated MB was diagnosed at coronary angiography (CAG) (Group I) and 48 patients with normal CAG results (Group II) were included in this study. The participants underwent treadmill exercise stress testing according to the Bruce protocol. QT dispersion (QTd) was defined as the minimum QT interval subtracted from the maximum. The Tp-e interval was defined as the difference between the QT and the QT peak time period. QTd and Tp-e intervals were calculated for all patients before and after exercise testing and differences between groups were compared.

RESULTS

At peak exercise, QTd and cQTd showed a significant increase in comparison to baseline values in the group of patients with myocardial bridges. Significant increases were also found with exercise in the Tp-e, cTp-e durations and Tp-e/QT ratio of the MB patient group in comparison to the baseline values. On the other hand, significant differences in QTd, cQTd, Tp-e, cTp-e intervals, and Tp-e/QT ratio during peak exercise in comparison with baseline values were not detected in the control group (p>0.05).

CONCLUSIONS

Significant increases in QTd, cQTd, Tp-e and cTp-e intervals and Tp-e/QT ratio were detected in the MB patients during exercise testing.

Myocardial bridge: The cause of angina in a young man

Myocardial bridging is basically the systolic narrowing of epicardial coronary arteries, secondary to their tunneled course in myocardium. Though it is a benign condition it can have the symptoms like acute coronary syndrome, arrhythmias and sudden cardiac death. We report a 32-year-old male, who presented with typical exertional angina, had positive exercise treadmill and thallium-201 test. Coronary angiography revealed myocardial bridge of distal left anterior descending coronary artery. He was put on β-blockers and was doing well at 8 years of follow-up.

Myocardial perfusion GSPECT imaging in patients with myocardial bridging

BACKGROUND

The aim of this study was to investigate the incidence, reversibility, and severity of LV perfusion abnormalities in patients with isolated myocardial bridges using a gated myocardial perfusion SPECT study (GSPECT).

METHODS

A retrospective study involved 42 patients without history of myocardial infarction, with isolated myocardial bridges detected in coronary angiography and no substantial evidence of atherosclerotic changes in coronary arteries. In all patients a gated SPECT study was performed at both rest and stress, after intravenous administration of (99m)Tc MIBI. Reconstructed slices were analyzed using a 20-segment model of the left ventricle.

RESULTS

Incidence and severity of stress-induced ischemia were related to degree of artery constriction (P = .002 and .00014, respectively). Perfusion abnormalities were detected only in patients with critical narrowing (≥ 50%) of artery (in 12 out of 28, i.e., 43% of patients). Summed stress scores (SSS) ranged from 4 to 11 (mean 7), indicating slight or moderate defect intensity. Only 1 patient presented with a SSS value of 31 (severe defect). Perfusion defects were stress induced in 70 out of 72 (97%) segments with abnormal perfusion.

CONCLUSION

Perfusion abnormalities were observed in ab. 40% of patients with critical (≥ 50%) narrowing of artery affected by bridging and were mild, stress induced.