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Myocardial bridging detection by non-invasive multislice spiral computed tomography: comparison with intravascular ultrasound

WANG, Ming-hui; SUN, Ai-jun; QIAN, Ju-ying; LING, Qing-zhi; ZENG, Meng-su; GE, Lei; WANG, Ke-qiang; FAN, Bing; YAN, Wei; ZHANG, Feng; Erbel, Raimund; GE, Jun-bo

Original article
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Background Invasive intravascular ultrasound (IVUS) is current diagnostic standard for myocardial bridging (MB). Non-invasive multislice computerized tomography coronary angiography (MSCT) technique has provided a good anatomical view of the tunnel artery now.

Methods A total of 51 consecutive patients with atypical or typical angina scheduled for IVUS were enrolled in this study and MSCT was performed 7 days before IVUS. Coronary imaging was quantified using IVUS and MSCT. Four main vessels (left main artery (LMA), left anterior descending (LAD), left circumflex (LCX), right coronary artery (RCA)) were examined.

Results Forty-one out of 51 (80%) patients received metaprolol (25 mg) before the MSCT scan and 25 of them were current beta-blocker users. The mean heart rate was (64±3) beats per minute. A total of 51 patients underwent IVUS examination (30 with MB and 21 without MB) were chosen for this study. Twenty-eight out of 30 MB cases were correctly diagnosed by MSCT and 2 patients with MB were not detected. Comparison with IVUS, the sensitivity of detection by MSCT was 93%, specificity was 100%. The lumen diameter of the tunnel artery derived from MSCT and IVUS significantly decreased from (2.9±0.3) mm to (2.4±0.4) mm (P<0.001) and from (3.3±0.3) mm to (2.6±0.5) mm (P<0.001), respectively. Minimal and maximal diameters of MB derived from MSCT were significantly smaller than those from IVUS ((2.4±0.4) mm vs (2.6±0.5) mm, P<0.05 and (2.9±0.3) mm vs (3.3±0.3) mm, P<0.05), respectively.

Conclusions MSCT offers a reliable non-invasive method for MB in LAD and atherosclerosis diagnosis with diagnostic accuracy comparable with invasive IVUS.

Chin Med J 2008;121(1):17–21

Department of Cardiology, Zhongshan Hospital, Fudan University; Department of Medicine, Shanghai Medical College, Fudan University, Shanghai 200032, China (Wang MH, Sun AJ, Qian JY, Ge L, Wang KQ, Fan B, Yan W, Zhang F and Ge JB) Department of Radiology, Zhongshan Hospital, Fudan University; Department of Medicine, Shanghai Medical College, Fudan University, Shanghai 200032, China (Ling QZ and Zeng MS) Department of Cardiology, University Clinic Essen, Essen 45122, Germany (Erbel R)

The first two authors contributed equally to this work.

Correspondence to: Dr. GE Jun-bo, Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai 200032, China (Email: jbge@zshospital.com)

(Received May 3, 2007)

Edited by WANG Mou-yue and LIU Huan

Myocardial bridging (MB) is a congenital coronary anomaly,1,2 which occurs when a segment of a coronary artery or its major branch travels through the myocardium instead of on the surface of the myocardium. The artery coursing within the myocardium is called a “tunneled artery”. In general, it is considered as a benign condition. However, a few MB patients with severe tunneled artery compression might suffer from myocardial ischemia and acute coronary syndromes,3–7 cardiac arrhythmias, and even sudden death.8–11 Correct diagnosis of MB in the coronary tree is helpful for guiding the consequence treatment for these patients. Most patients with MB need no special treatment and a few MB patients with severe tunneled artery compression will benefit from beta-blocker, and coronary vasodilators should be avoided.12–14 Intravascular ultrasound (IVUS) is now the golden standard for MB diagnosis. Currently, good anatomical view of the tunnel artery was also shown by noninvasive multislice CT (MSCT).15–17 Till now, there is no systemic study comparing invasive and non-invasive technique on MB diagnosis. This study was, therefore, designed to investigate the feasibility and accuracy of 16-slice MSCT in MB diagnosis in comparison with IVUS.

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METHODS

A total of 51 patients (38 men) with atypical or typical angina underwent invasive quantitative coronary angiography (QCA) and IVUS between August 2005 and November 2005 were chosen for this study. MSCT was performed 7 days before IVUS examination. Four main vessels (left main artery (LMA), left anterior descending (LAD), left circumflex (LCX), right coronary artery (RCA)) were examined. Exclusion criteria included irregular heart rate, allergy to iodinated contrast agents, serum creatinine >120 mmol/L, congestive heart failure (ejection fraction (EF)<40%), chronic bronchitis, chronic obstruction pulmonary disease and other contraindications to beta-blocker. Oral metaprolol (25 mg) was given to patients with heart rates over 65 beats per minute one hour before MSCT imaging to reduce motion artifacts caused by elevated heart rate and sublingual nitroglycerin (0.4 mg) was given one minute before image acquisition. The study protocol was approved by the local ethics committee and all participants gave informed consent.

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Invasive techniques and analysis

QCA was obtained using 6F catheter and the transfemoral Judkins technique was used for all interventions. All angiograms were analyzed off-line with the Cardiovascular Medcon System (Medcon Telemedicine Technology, Inc., Whippany, NJ, USA). The determination of myocardial bridging was based on a typical “milking effect” in coronary artery. After passage of the guidewire across the target lesion, IVUS was performed (Atlantis 3.0F, 40 MHz coronary imaging catheter, SCIMED, Boston Scientific Corporation, USA), continuous ultrasound images were obtained from distal and proximal myocardial segments in real time and stop frames. The position of the IVUS probe was documented and numbered on X-ray film at the points where the IVUS images were taken. The determination of myocardial bridging was based on a typical “half moon” phenomenon, a specific echolucent phenomenon around the bridge segment which exists throughout the cardiac cycle.18 The following parameters were obtained: minimal/maximal luminal diameters of the myocardial segment were measured in systolic and diastolic phase, respectively. Minimal lumen diameter (MLD) of the normal proximal and distal segment to myocardial segment were measured in both systolic and diastolic phases.

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MSCT technique and image reconstruction

MSCT was performed using a 16-detector row MSCT scanner (SOMATOM Sensation 16, Siemens, Forchheim, Germany). The scan parameters were chosen as follows: 16 mm × 0.75 mm collimation, tube voltage 120 kV, effective tube current-time product 750 mA, table feed 3.0 mm/rotation and tube rotation time 375 ms. The Adaptive Cardio Volume reconstruction approach applied with the scanner was used. A bolus of 100 ml contrast medium (ULTRAVIST 370) was injected through an antecubital vein at 4.5 ml/s during a 15–18 seconds period of breath holding; effective radiation dose was 58.5 mGy, and an effective slice thickness was 1.0 mm. Image reconstruction was gated by ECG using a half-scan reconstruction algorithm to perform the temporal resolution of 185 ms. Retrospective ECG-gated reconstruction was obtained at 30%-40% and 60%-70% of the R-R interval (representing relative systolic and diastolic phases). Data were transferred to a PC-based workstation (Wizard, Siemens Medical Solutions, Erlangen, Germany) after reconstruction. Two experienced radiologists blinded to the IVUS results evaluated the coronary segments according to a modified American Heart Association classification.18 By ECG-gated MSCT reconstruction, MB diagnosis was made when the tunnel artery (myocardial segment) covered with different thickness of myocardium and the lumen was narrowed during systolic phase and reconverted during diastolic phase. One tunnel artery axial image from systolic and diastolic phase was chosen to generate appropriate maximum intensity projection (MIP) reconstruction and curved multi-planar reconstructions (MPR).19,20

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Statistical analysis

Data were presented as frequencies or mean ± standard deviation (SD). Statistical analysis was performed with SPSS 11.0 statistical package. The diagnostic performance of MSCT for the detection of myocardial bridging were compared with IVUS as standard reference method, and sensitivity, specificity, negative and positive predictive rates with the corresponding 95% confidence interval were determined. Differences in means were tested by the unpaired Student's t test and differences in proportions by the chi-square test. Quantitative lumen diameters were compared using bivariate correlation. A P value <0.05 was considered statistically significant.

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RESULTS

General clinical characteristics were similar between patients with or without MB (Table). Forty-one out of 51 (80%) patients received metaprolol (25 mg) before the MSCT scan and 25 of them were current beta-blocker users. The mean heart rate was (64±3) beats/min during the scan procedure. The total scan time was (16.1±1.2) seconds. Scan image quality was sufficient in all the 51 patients and no patient or segment was excluded from the analysis.

Table

Table

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Myocardial bridging detection by IVUS, QCA and MSCT

MB was present in 30 patients by IVUS and all MBs were located in LAD and no MB was detected in LMA, LCX, RCA. There were 28 single-MB segments located in the middle portion of the LAD and 2 double-MB segments located in both middle and distal portion of LAD in IVUS examination. Twenty-eight out of 30 MB were correctly diagnosed by MSCT and 2 patients with single MB were misdiagnosed as normal and these 2 myocardial segments were short (3.0 and 4.5 mm, respectively) and the degrees of systolic lumen compression were relatively small (2.8 to 2.7 mm and 2.0 to 1.9 mm, respectively). An MB detected in a sample case by IVUS and MSCT is shown in the figure. In comparison with IVUS, the sensitivity of detecting myocardial bridging by MSCT was 93% (28 of 30), specificity was 100%, positive predictive value and negative predictive value were 100% and 91%, respectively. MSCT identified the atherosclerosis proximal to MB segments and significant stenosis in the segments proximal to the MB in 5 out of 28 MB cases, which is comparable to the IVUS findings (8 out of 30). In comparison with IVUS, QCA correctly diagnosed 29 out of 30 MB cases and 1 patient with single MB at the middle portion of LAD was misdiagnosed by QCA as coronary stenosis. The sensitivity of detection by QCA for patients with or without myocardial bridging was 97% (29 of 30), specificity was 100%, positive predictive value and negative predictive value were 100% and 96%, respectively.

Figure.

Figure.

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MB quantification by IVUS and MSCT

The lumen diameter of the tunnel artery derived from MSCT and IVUS significantly decreased from (2.9±0.3) mm to (2.4±0.4) mm (P<0.001) and from (3.3±0.3) mm to (2.6±0.5) mm (P<0.001) respectively during the cardiac cycle and a significant correlation between lumen diameters derived from MSCT and IVUS was observed (systolic phase: r=0.87, P<0.05; diastolic phase: r=0.92, P<0.05). Minimal and maximal diameters of MB during systolic and diastolic phase derived from MSCT were significantly smaller than those from IVUS ((2.4±0.4) mm vs (2.6±0.5) mm, P<0.05 and (2.9±0.3) mm vs (3.3±0.3) mm, P<0.05) while narrowing percent derived from the two methods was similar ((21.4±10.9)% vs (17.4±7.6)%, P>0.05).

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DISCUSSION

The major finding of the present study is that the diagnostic accuracy on MB in LAD by non-invasive MSCT is comparable with that by invasive IVUS. Our study showed that twenty-eight out of 30 MB diagnosed by IVUS were correctly diagnosed by MSCT. Compared with IVUS, the sensitivity of detecting by MSCT for patients with myocardial bridging was 93%, specificity was 100%. Thus, most of the MB patients could be correctly diagnosed by non-invasive MSCT. This diagnostic tool is cheaper and safer, so MB patients will benefit from this technique and be treated properly.

Conventional invasive coronary angiography was currently standard for clinical evaluation of myocardial bridging, and the diagnosis was proved of the typical systolic vessel compression (milking effect), but it was difficult to demonstrate myocardial bridging when the systolic compression was relatively minimal. Some previous studies suggested that nitroglycerin may augment systolic myocardial compression and helped the diagnosis. However, the presence of atherosclerosis in the myocardial segment would be very difficult to detect using conventional coronary angiography. Therefore, intravascular ultrasound is accepted as a golden standard for the morphological assessment of myocardial bridging.

Coronary MSCT has recently been established as a reliable and non-invasive technique for the diagnosis of coronary lesions and congenital abnormalities.21 By MSCT, the accurate coronary evaluations were based on obtaining image of the coronary artery tree at the time of its maximal vasodilation and minimal motion artifacts. For this reason, the reconstruction window was usually positioned within the diastolic phase.22 But, for the accurate diagnosis of myocardial bridging, it must include the reconstruction window in systolic phase.23

Conventional invasive IVUS is currently the standard diagnosis method for clinical evaluation of myocardial bridging. Though the risk of adverse events is small, the potentially life-threatening consequences such as coronary artery dissection, arrhythmia, stroke (total complication rate: 1.8% and mortality rate: 0.1%) might occur during the invasive procedures.23,24 MSCT offers a safer, more comfortable and cost-effective (the prices of IVUS and MSCT examinations in China are 12 000 Yuan (1500 US$) and 750 Yuan (95 US$)) respectively. Since MSCT could follow the whole “journey” of tunneled artery, it could define the precise location and the length of the MB. It is worthy of noting that in 7 out of 28 MB cases, the MB diameters in systolic and diastolic phases could not be exactly determined by MSCT and further imaging quality improvement by MSCT is therefore warranted.

Study limitations are as follows: First, only symptomatic patients with an inconclusive or conclusive risk on exercise ECG stress testing were referred for catheterization, there was a high incidence of true myocardial bridging (59%) in our patients, tending to increase sensitivity. Second, the important limitation in MSCT was the need of lower heart rate, the dose of radiation, and the side effect of contract administration were also been considered.24

In conclusion, our study results may have important clinical implications, MSCT offers a reliable non-invasive method for myocardial bridging in LAD and atherosclerosis diagnosis with diagnosis accuracy comparable with invasive IVUS. Especially, in some patients with sinus rhythm but haven't the risk of coronary atherosclerosis disease, MSCT can be considered an alternative to invasive coronary angiography for patients with myocardial bridging.

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REFERENCES

1. Grainicianu A. Anatomische studien uber die coronararterien und experimentelle untersuchugen uber ihre durchgangigkeit. Virchow's Arch 1922; 238: 1–8.
2. Ishikawa Y, Akasaka Y, Ito K, Akishima Y, Kimura M, Kiguchi H, et al. Significance of anatomical properties of myocardial bridge on atherosclerosis evolution in the left anterior descending coronary artery. Atherosclerosis 2006; 186: 380–389.
3. Arjomand H, A1 Salman J, Azain J, Amin D. Myocardial bridging of left circumflex coronary artery associated with acute myocardial infarction. J Invasive Cardiol 2000; 12: 431–434.
4. Akdemir R, Gunduz H, Emiroglu Y, Uyan C. Myocardial bridging as a cause of acute myocardial infarction: a case report. BMC Cardiovasc Disord 2002; 2: 15.
5. Gowda RM, Khan IA, Ansari AW, Cohen RA. Acute ST segment elevation myocardial infarction from myocardial bridging of left anterior descending coronary artery. Int J Cardiol 2003; 90: 117–118.
6. Mohlenkamp S, Hort W, Ge J, Erbel R. Update on myocardial bridging. Circulation 2002; 106: 2616–2622.
7. Mazzu A, Di Tano G, Cogode R, Lo Presti G. Myocardial bridging involving more than one site of the left anterior descending coronary artery: an uncommon cause of acute ischemic syndrome. Cathet Cardiovasc Diagn 1995; 34: 329–332.
8. Tio RA, Van Gelder IC, Boonstra PW, Crijns HJ. Myocardial bridging in a survivor of sudden cardiac near-death: role of intracoronary Doppler flow measurements and angiography during dobutamine stress in the clinical evaluation. Heart 1997; 77: 280–282.
9. Cutler D, Wallace JM. Myocardial bridging in a young patient with sudden death. Clin Cardiol 1997; 20: 581–583.
10. Cheng TO. Myocardial bridging in a young patient with sudden death. Clin Cardiol 1997; 20: 743.
11. Alegria JR, Herrmann J, Holmes DR Jr, Lerman A, Rihal CS. Myocardial bridging. Eur Heart J 2005; 26: 1159–1168.
12. Ge J, Erbel R, Rupprecht H, koch L, Kearney P, Gorge G, et al. Comparison of intravascular ultrasound and angiography in the assessment of myocardial bridging. Circulation 1994; 89: 1725–1732.
13. Zhang F, Ge JB, Qian JY, Dong LL, Lu Y. Variant angina associated with isolated myocardial bridging: evaluation using intravascular ultrasound and quantitative coronary angiography. Chin Med J 2007; 120: 171–173.
14. Benett JM, Blomerus P. Thallium-201 scintigraphy perfusion defect with dipyridmole in a patient with myocardial bridge. Clin Cardiol 1988; 11: 268–270.
15. Hoffmann MH, Shi H, Schmitz BL, Schmid FT, Lieberknecht M, Schulze R, et al. Noninvasive coronary angiography with multislice computed tomography. JAMA 2005; 293: 2471–2478.
16. Hoffmann MH, Shi H, Manzke R, Schmid FT, De Vries L, Grass M, et al. Noninvasive coronary angiography with 16-detector row CT: effect of heart rate. Radiology 2005; 234: 86–97.
17. Cademartiri F, Schuijf JD, Mollet NR, Malagutti P, Runza G, Bax JJ, et al. Multislice CT coronary angiography: how to do it and what is the current clinical performance? Eur J Nucl Med Mol Imaging 2005; 32: 1337–1347.
18. Ge J, Jeremias A, Rupp A, Abels M, Baumgart D, Liu F, et al. New signs characteristic of myocardial bridging demonstrated by intracoronary ultrasound and Doppler. Eur Heart J 1999; 20: 1707–1716.
19. Austen WG, Edward JE, Frye RL, Gensini GG, Gott VL, Griffith LS, et al. A reporting system on patients evaluated for coronary artery disease. Report of the Ad Hoc Committee for Grading of Coronary Artery Disease, Council on Cardiovascular Surgery, American Heart Association. Circulation 1975; 51 Suppl 4: 5–40.
20. Kawawa Y, Ishikawa Y, Gomi T, Nagamoto M, Terada H, Ishii T, et al. Detection of myocardial bridge and evaluation of its anatomical properties by coronary multislice spiral computed tomography. Eur J Radiol 2007; 61: 130–138.
21. Kopp AF, Schroeder S, Kuettner A, Heuschmid M, Georg C, Ohnesorge B, et al. Coronary arteries: retrospectively ECG-gated multi-detector row CT angiography with selective optimization of the image reconstruction window. Radiology 2001; 221: 683–688.
22. Amoroso G, Battolla L, Gemignani C, Panconi M, Petronio AS, Rondine P, et al. Myocardial bridging on left anterior descending coronary artery evaluated by multidetector computed tomography. Int J Cardiol 2004; 95: 335–337.
23. Bashore TM, Bates ER, Berger PB, Clark DA, Cusma JT, Dehmer GJ, et al. American College of Cardiology/Society for Cardiac Angiography and Interventions Clinical Expert Consensus Document on cardiac catheterization laboratory standards; a report of the American College of Cardiology Task Force on Clinical Expert Consensus Documents. J Am Coll Cardiol 2001; 37: 2170–2214.
24. Kaiser C, Bremerich J, Haller S, Brunner-La Rocca HP, Bongartz G, Pfisterer M, et al. Limited diagnostic yield of noninvasive coronary angiography by 16-slice multi-detector spiral computed tomography in routine patients referred for evaluation of coronary artery disease. Eur Heart J 2005; 26: 1987–1992.
Keywords:

multislice computerized tomography; coronary angiography; intravascular ultrasound; myocardial bridging

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