Elsevier

Journal of Nuclear Cardiology

Volume 18, Issue 6, December 2011, Pages 1059-1065
Journal of Nuclear Cardiology

Original Article
Myocardial perfusion GSPECT imaging in patients with myocardial bridging

https://doi.org/10.1007/s12350-011-9406-8Get rights and content

Abstract

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 99mTc 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.

Introduction

Myocardial bridging, a congenital anomaly, occurs if a segment of a coronary artery travels through the myocardium instead of the myocardium surface. Bridges, in a majority of cases, affect the left anterior descending artery. In coronary angiography their incidence varies between 0.5% and 4.5% of studied patients.1,2 Symptomatology of myocardial bridges includes not only a chest pain, but also heart rhythm and conductivity disorders and even cases of sudden cardiac death.3, 4, 5, 6 Typically, myocardial bridging causes a narrowing of the coronary artery at the time of ventricular contraction, causing the angiographic “milking” effect.2,7 However, several quantitative angiographic and intravascular ultrasound studies in patients with myocardial bridging demonstrated that vessel compression is not limited to systole, but rather persists into diastole and thereby affects the predominant phase of coronary perfusion.7, 8, 9

Cardiac literature does not propose established standards for dealing with myocardial bridging. Pharmacological treatment is applied most frequently,10,11 but also percutaneous transluminal coronary angioplasty10,12,13 and cardiosurgical interventions (myotomy, aortal-coronary bypassing)14,15 have been practiced.

Myocardial perfusion single photon emission computed tomography (SPECT) imaging—a sensitive, noninvasive method, widely used for detection of perfusion abnormalities could potentially be helpful in dealing with cardiac bridges. A gated SPECT study also providing possibility to assess left ventricular regional and global contraction is a more advanced form of this method.16,17 One of advantages of GSPECT is a possibility to correct for artifacts resulting from attenuation of gamma radiation by organs and tissues surrounding a heart, by means of combination of perfusion images with regional left ventricular contractility.18,19

In the literature, only a few studies using radionuclide myocardial perfusion imaging for the evaluation of the effect of myocardial bridges upon perfusion of the left ventricular myocardium have been reported. These were mostly studies on small groups of patients.9,12,20, 21, 22, 23 Therefore, the aim of this study was to define the incidence, severity, and reversibility of myocardial perfusion abnormalities by SPECT imaging in patients with myocardial bridging.

Section snippets

Methods

A retrospective study involved 42 patients among 5,250 referred to our department in the years 2006-2009 for myocardial perfusion SPECT study. Selected patients had neither prior history nor ECG signs of a myocardial infarction and were later on referred for coronary angiography due to a suspicion of coronary artery disease, but this study revealed a myocardial bridging and no substantial evidence of atherosclerotic changes in coronary arteries. The study group of 42 patients was selected among

Results

All myocardial bridges revealed by coronary angiography were located on left anterior descending artery. Systolic artery constriction ranged from 30% to 90% (mean value 50%).

A statistically significant relationship between degrees of systolic artery constriction and summed stress scores (SSS) obtained from myocardial perfusion study has been found (P = .00014). This relationship is presented in Figure 2. As a consequence of this finding, a statistically significant relationship between a degree

Discussion

Disturbed intracoronary hemodynamics in myocardial bridges has been demonstrated by means of coronary angiography, intracoronary ultrasound, and Doppler studies.9,25,26 Schwarz et al25 showed that a delay in diastolic lumen gain in artery segment affected by bridging represents the major functional abnormality leading to increased flow velocities and the occurrence of clinical symptoms. They also demonstrated that dynamic flow and diameter alterations combined with a reduced coronary flow

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    See related editorial, doi:10.1007/s12350-011-9443-3.

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