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  • The Internet Journal of Cardiology
  • Volume 8
  • Number 2

Original Article

Muscle Bridge; Be careful while reporting “Myocardial Bridge”

J Kojoury, M Tavassoly

Keywords

muscle bridge, myocardial ischemia., vasovagal reaction

Citation

J Kojoury, M Tavassoly. Muscle Bridge; Be careful while reporting “Myocardial Bridge”. The Internet Journal of Cardiology. 2009 Volume 8 Number 2.

Abstract

A 62 – year – old lady presented to emergency department with chief complaint of repeated compressive chest pain at physical activity. In electrocardiography had only Minor ST- T change& Angiography showed narrowing at mid part of left anterior descending artery which was mainly at systole with normal caliber in diastole and good distal flow but after normalization of blood pressure & pulse Rate, the left anterior descending artery lesion became disappear in systole & diastole. Thus in this patient, hypotensive episode due to fainting and vasovagal reaction, could provoke myocardial bridge.

 

Case Presentation

A 62 – year – old lady presented to emergency department with chief complaint of repeated compressive chest pain at physical activity. The patient hadn't history of Hypertension, Diabetes Mellitus, Hyperlipidemia or smoking. Her Blood pressure was 120 over 70 mmHg with pulse and pulse rate was 80 beats per minute, in cardiac auscultation had LT sided S4 without any murmur, in lung examination hadn't abnormal finding.

In electrocardiography had only Minor ST- T change & transthorasic echocardiography showed ejection fraction of 55% without Regional wall motion abnormality, the valvular structures were normal.

Due to continuing chest pain, coronary Angiography was planned for her. At the start of angiography, the patient developed Hypotension & bradycardia (BP 70mmHg over pulse and Heart Rate of 40 beats per minute), which was addressed properly with hydration and atropine injection. After stabilization coronary angiography was preceded and showed left main coronary artery had none significant plaque at distal part and a narrowing at mid part of left anterior descending artery which was mainly at systole with normal caliber in diastole and good distal flow (figures 1, 2).

Figure 1
Systole (fig.1) (show narrowing of LAD)

Figure 2
Diastole (fig2) (Show normal flow of LAD)

Although, this coronary Angiography had characteristic appearance for muscle Bridge, after normalization of blood pressure & pulse Rate, new projection revealed left anterior descending artery lesion became disappear in systole & diastole (fig3,4).

Figure 3
Figure 3: Systole (after stabilization)

Figure 4
Figure 4: Diastole (after stabilization)

Thus in this patient, hypotensive episode due to fainting and vasovagal reaction, could provoke myocardial bridge.

Discussion

Myocardial bridges are most commonly localized in the middle segment of the left anterior descending coronary artery (LAD)¬1 .They are located at a depth of 1 to 10 mm2,3 with a typical length of 10 to 30 mm 4 .

Coronary atherosclerosis in association with myocardial bridging has primarily been studied in the LAD. The segment proximal to the bridge frequently shows atherosclerotic plaque formation 4,5 .

Muscle bridge presented with Angina, myocardial ischemia, myocardial infarction, left ventricular dysfunction, myocardial stunning, paroxysmal AV blockade, as well as exercise-induced ventricular tachycardia and sudden cardiac death are accused sequelae of myocardial bridging. 6,7,8 . The current gold standard for diagnosing myocardial bridges is coronary angiography with the typical “milking effect” and a “step down–step up” phenomenon induced by systolic compression of the tunneled segment.

Decreasing intracoronary pressure by different means, such as intracoronary nitrates is the best way to induce this milking effect.This case shows that in those with baseline low blood pressure ( such as those recovering the vasovagal reaction) may show a similar presentation too.

On the basis of the above mechanisms for ischemia, three treatment strategies have been explored:

Negative inotropic and/ or chronotropic agents ie;B blockers9,10 and calcium channel blockers11. This generally is considered the first line therapy in symptomatic patients.

Surgical myotomy or bypass surgery12,13. In those refractory to medications.

Stenting of tunneled segment 14, 15.

References

1. Poláek P, Zechmeister A. The occurrence and significance of myocardial bridges and loops on coronary arteries.In: V.Krutna, ed. Monograph 36, Opuscola Cardiologica. Acta Facultatis Medicae Universitatis Brunenses. University J.E. Purkinje, Brno; 1968: 1–99.
2. Penther P, Blanc JJ, Boschat J, et al. L’artère interventriculaire antérieure intramurale: étude anatomique. Arch Mal Coeur. 1977; 70: 1075–1079
3. Ortale JR, Gabriel EA, Lost C, et al. The anatomy of the coronary sinus and its tributaries. Surg Radiol Anat. 2001; 23: 15–21
4. Myocardial bridges: a review. Prog Cardiovasc Dis. 1983; 26: 75–88
5. Giampalmo A, Bronzini E, Bandini T. Sulla minor compromissione aterosclerotica delle arterie coronarie quando siano (per variante anatomica) in situazione intramiocardica. Giornale ItalArterioscl.1964;2:1–14.
6. Noble J, Bourassa MG, Petitclerc R, et al. myocardial bridging and milking effect of the left anterior descending coronary artery: normal variant or obstruction? Am J Cardiol. 1976; 37: 993–999
7. Rossi L, Dander B, Nidasio GP, et al. Myocardial bridges and ischemic heart disease. Eur HeartJ.1980; 1:239–245
8. Hort W. Anatomie und Pathologie der Koronararterien. B. Muskelbrücken der Koronararterien.In: W.Hort, Hrsg. Pathologie des Endokards, der Koronararterien und des Myokards. Berlin, Germany: Spring.
9. Nair CK, Dang B, Heintz MH, et al. Myocardial bridges: effect of propanolol on systolic compression. Can J Cardiol. 1986; 2: 218–221
10. Schwarz ER, Klues HG, vom Dahl J, et al. Functional, angiographic and intracoronary Doppler flow characteristics in symptomatic patients with myocardial bridging: effect of short-term intravenous beta-blocker medication. J Am Coll Cardiol. 1996; 27: 1637–1645
11. Kracoff OH, Ovsyshcher I, Gueron M. Malign course of a benign anomaly: myocardial bridging. Chest. 1987; 92: 1113–1115
12. Binet JP, Guiraudon G, Langlois J, et al. Angine de poitrine et ponts musculaires sur l’artère interventriculaire anterieure: a propos trois cas opérés. Arch Mal Cur. 1978; 71: 251–258
13. Iversen S, Hake U, Meyer E, et al. Surgical treatment of myocardial bridging causing coronary artery obstruction. Scand J Thor Cardiovasc Surg. 1992; 26: 107–111
14. Klues HG, Schwarz ER, vom Dahl J, et al. disturbed intracoronary hemodynamics in myocardial bridging. Early normalization by intracoronary stent placement. Circulation.1997;96:2905–29
15. Haager 15.Haager PK, Schwarz ER, vom Dahl J, et al. Long-term angiographic and clinical follow up in patients with stent implantation for symptomatic myocardial bridging. Heart. 2000; 84: 403–408

Author Information

Javad Kojoury, M.D.
Cardiologist, Interventionist. Associate professor of cardiology.

Maryam Tavassoly, M.D.
Cardiology Resident

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