Named signs in myocardial bridging

Named signs in myocardial bridging

Signs in myocardial bridging: There are several named signs in myocardial bridging. Myocardial bridging is usually seen in left anterior descending coronary artery, with a segment of the artery passing beneath a myocardial bridge. It produces narrowing of the coronary artery in systole, which is relieved in diastole. Hence most often it does not compromise the coronary blood flow, which is mostly in diastole.

Some of the named signs in myocardial bridging are [1]:

  1. “Milking effect” is noted on coronary angiography indicating the systolic compression and diastolic relief of compression
  2. “Step down-step up” phenomenon can be seen both on coronary angiography still pictures and coronary CT angiography, due to the effect of myocardial bridge on the coronary lumen.
  3. “Half-moon phenomenon” is noted on intravascular ultrasound. It can occur even without the ‘milking effect’, the milking effect can be provoked in these cases.
  4. “Fingertip phenomenon” and “spike-and-dome pattern” are descriptions for the intracoronary Doppler flow patterns in myocardial bridging.

Myocardial bridge muscle index is the product of myocardial bridge thickness multiplied by its length [2]. In that autopsy study, myocardial infarction was more likely in those with a thicker bridge and higher myocardial bridge muscle index. Progression of atherosclerosis was maximum at 2 cm proximal to the entrance of the myocardial bridge in the left anterior descending coronary artery.

Classification of myocardial bridging

Schwarz ER et al have classified myocardial bridging without associated coronary artery disease into 3 types [3]. Type A is an incidental finding on angiography without objective signs of ischemia; Type B had objective signs of ischemia; Type C with or without objective signs of ischemia and altered intracoronary hemodynamics as assessed by quantitative coronary angiography, coronary flow reserve or intracoronary Doppler. Five year follow up showed that types B and C responded well to beta blockers or calcium channel blockers. Patients with type C refractory to medical therapy was treated by stenting of the myocardial bridge.

Other treatment options considered in those with refractory symptoms are minimally invasive coronary artery bypass grafting (CABG) and surgical myotomy [1]. CABG is considered in case of extensive or deep myocardial bridges.

References

  1. Tarantini G, Migliore F, Cademartiri F, Fraccaro C, Iliceto S. Left Anterior Descending Artery Myocardial Bridging: A Clinical Approach. J Am Coll Cardiol. 2016 Dec 27;68(25):2887-2899.
  2. Ishikawa Y, Akasaka Y, Suzuki K, Fujiwara M, Ogawa T, Yamazaki K, Niino H, Tanaka M, Ogata K, Morinaga S, Ebihara Y, Kawahara Y, Sugiura H, Takimoto T, Komatsu A, Shinagawa T, Taki K, Satoh H, Yamada K, Yanagida-Iida M, Shimokawa R, Shimada K, Nishimura C, Ito K, Ishii T. Anatomic properties of myocardial bridge predisposing to myocardial infarction. Circulation. 2009 Aug 4;120(5):376-83.
  3. Schwarz ER, Gupta R, Haager PK, vom Dahl J, Klues HG, Minartz J, Uretsky BF. Myocardial bridging in absence of coronary artery disease: proposal of a new classification based on clinical-angiographic data and long-term follow-up. Cardiology. 2009;112(1):13-21.