Discussion
Mohlenkamp et al ., defines myocardial bridge as a muscle overlying intra-myocardial segment of an epicardial artery . Although generally a benign condition , myocardial bridging can be associated with myocardial ischemia . On average , myocardial bridges are present in onethird of adults . The rate of angiographic bridging is < 5 %. The prevalence also appears to be high in post-heart transplant patients and in patients with hypertrophic obstructive cardiomyopathy ( HOCM ). 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 . Other attempted treatment modalities include the use of calcium channel blockers , stenting of tunneled segment , surgical myotomy , and CABG . 1 Corban et al . finds that myocardial bridges are commonly located over the left anterior descending artery . 2 Ishikawa and colleagues find that myocardial bridges suppress coronary atherosclerosis by altering endothelial permeability , which may be due to changes in hemodynamic force tending towards higher shear stress . 3 However , there have been no consistent associations described in the literature between atypical or angina-like chest pain and symptom severity , length or depth of tunneled segment , or degree of compression by the myocardial bridge . Schwarz et al ., point out that in patients with myocardial bridges , administration of short-acting beta-blockers during atrial pacing alleviates angina symptoms and signs of ischemia . 4 Pratt and colleagues state that surgical approach is usually reserved for patients who are symptomatic and refractory to medical treatment . 5 Longterm prognosis in patients with isolated myocardial bridging is generally good . A study done by Kramer et al ., in Ohio revealed the rate of incidence of myocardial bridging to be 12 % in 658 normal angiograms performed . The same study found that five-year survival in 81 subjects aged 46 years was 97.5 %, with neither of the two deaths related to the myocardial bridge 6 . A long-term follow-up study done by Juilliere et al ., found that among
7,467 consecutive coronary angiograms performed during an eight-year period , 61 patients had a myocardial bridge of the left anterior descending coronary artery . The overall prevalence of myocardial bridges was 0.82 %. 7 A descriptive cross-sectional study done by Saidi et al ., attempted to better study the morphology of myocardial bridges by dissecting 109 adult hearts . Myocardial bridges were found in 40.4 % of the hearts , most commonly in the left anterior descending artery ( LAD ). The average length of the bridges was 22.66 + 11.94 mm while the depth was 1.83 + 0.98mm , with only 11 % being long ( 34.87mm - 50mm ) and 9 % of them being deep ( 3.46mm - 5.00mm ). The tunica intima was thickest proximal to and thinnest under the myocardial bridge . The same study revealed that myocardial bridges were found in 44 ( 40.4 %) hearts ( 32 males , 12 females ). About 84 % of the bridges were found in the middle third of the left anterior descending . Other bridged vessels included the right coronary artery ( 6.8 %) and the left circumflex , arteria ramus intermedius . The posterior interventricular and the right marginal arteries had one bridge each ( 2.3 %). 8 As described by Yukio , et al . knowledge about myocardial bridge is relevant because coronary vasospasms can result from increased contractions as seen in physical activity or increased size and as seen in hypertrophic cardiomyopathy . 9
Conclusion
Myocardial bridging can present with multiple variations . Patient symptomatology can also vary ranging from asymptomatic presentation , angina , syncope , and sudden death . When obvious cardiac and non-cardiac causes of chest pain do not explain patient ’ s symptomatology , a high index of suspicion for anatomical coronary variations should be kept in mind . Subtle EKG changes and pain relief with beta blockers may help point towards structural variations . Early cardiology referral and timely coronary angiogram help prevent adverse patient outcomes .
References
1 . Möhlenkamp S , Hort W , Ge J , Erbel R : Update on myocardial bridging . Circulation . 2002 , 12:2616-22 . doi10.1161 / 01 . cir . 0000038420.14867.7a . PMID : 12427660
2 . Corban MT , Hung OY , Eshtehardi P , et al .: Myocardial bridging : contemporary understanding of pathophysiology with implications for diagnostic and therapeutic strategies . J Am Coll Cardiol . 2014 , 63:2346-55 . doi10.1016 / j . jacc . 2014.01.049
3 . Ishikawa Y , Ishii T , Asuwa N , et al .: Absence of atherosclerosis evolution in the coronary arterial segment covered by myocardial tissue in cholesterol-fed rabbits . Virchows Archiv430 . 163-171 .
4 . 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 , 27:1637-16 . doi10.1016 / 0735-1097 ( 96 ) 00062-9 . PMID : 8636548 .
5 . Pratt JW , Michler RE , Pala J , et al .: Minimally-invasive coronary artery bypass grafting for myocardial muscle bridging . Heart Surgery Forum . 1999 , 2:250-253 .
6 . Kramer JR , Kitazume H , Proudfit WL , et al .: Clinical significance of isolated coronary bridges : benign and frequent condition involving the left anterior descending artery . Am Heart J . 1982 , 103:283-288 . oi10.1177 % 2F021849239700500410
7 . 7 . Juillière Y , Berder V , Suty- Selton C , et al .: Isolated myocardial bridges with angiographic milking of left anterior descending coronary artery : a long-term follow-up study . Am Heart J . 1995 , 129:663-665 . doi10.1016 / 0002-8703 ( 95 ) 90312-7 .
8 . 8 . Saidi , H ., Ongeti , W . K ., & Ogeng ' o , J . ( 2010 : Morphology of human myocardial bridges and association with coronary artery disease . African health sciences . 10:242-247 .
9 . 9 . Yukio I , Yoko K , Ehiichi K , et al .: ( 1 ) coronary events caused by myocardial bridge . Annals of vascular diseases . 2009 , 2:79-94 .
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