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Year : 2020  |  Volume : 63  |  Issue : 3  |  Page : 495-496
Myocardial bridging: An unexplained cause of sudden cardiac death in an explanted donor heart


1 Department of Pathology, AIIMS, New Delhi, India
2 Department of Cardiothoracic and Vascular Surgery (CTVS), AIIMS, New Delhi, India
3 Department of Intensive Care Unit (ICU), CTVS, AIIMS, New Delhi, India
4 Department of Cardiology, AIIMS, New Delhi, India

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Date of Submission06-May-2019
Date of Decision26-Sep-2019
Date of Acceptance14-Jan-2020
Date of Web Publication7-Aug-2020
 

How to cite this article:
Phulware RH, Arava S, Rajashekar P, Hote MP, Singh SP, Seth S, Ray R. Myocardial bridging: An unexplained cause of sudden cardiac death in an explanted donor heart. Indian J Pathol Microbiol 2020;63:495-6

How to cite this URL:
Phulware RH, Arava S, Rajashekar P, Hote MP, Singh SP, Seth S, Ray R. Myocardial bridging: An unexplained cause of sudden cardiac death in an explanted donor heart. Indian J Pathol Microbiol [serial online] 2020 [cited 2020 Oct 30];63:495-6. Available from: https://www.ijpmonline.org/text.asp?2020/63/3/495/291668




Myocardial bridging (MB) or myocardial tunnelling is a congenital coronary anomaly characterized by a segment of coronary artery having an intramural course.[1] Its incidence in general population is high with 5% to 55% in necropsy studies and 0.5% to 9% in coronary angiography.[2],[3] MB can occur in any coronary artery, but the middle and terminal part of the left anterior descending coronary artery (LAD) is most commonly involved.[4] Many studies suggested a probable hemodynamic significance of myocardial bridging and its association with myocardial infarction, ventricular rupture, severe hypotension, angina, arrhythmias, apical ballooning syndrome, hypertrophic cardiomyopathy, and sudden death.[1],[2]

Here, we are presenting a case of MB in a patient who underwent cardiac transplantation and succumbed to sudden cardiac death on the second post-operative day. There were no intra-operative or immediate post-operative surgery related complications.

The index case was a 52-year-old male patient, who underwent heart transplantation for dilated cardiomyopathy (DCM). The age matched donor heart was transplanted from a brain dead individual following a road traffic accident. The transplant surgery was carried out with the biatrial procedural method. The intraoperative and immediate postoperative period was uneventful; however, the patient died on the second postoperative day. A limited autopsy was performed and the explanted donor heart was sent for a detailed histopathological examination. The explanted donor heart weighed 430 g. Externally pericardium was thickened and showed the patchy areas of pericarditis possibly due to the post-surgical reaction with focal adherence of visceral and parietal pericardium. The surgical sutures were intact. On sequential heart dissection both ventricular cavities, myocardium and both atria appeared normal. Tricuspid valve, right ventricular tract and pulmonary artery were unremarkable. Right ventricular wall was grossly unremarkable. Left atrium, mitral valve, and left ventricular wall were within normal limits. No macroscopic evidence of myocardial infarction was seen. Grossly there was no obvious atherosclerosis in any of the coronary arteries. Dissection of coronaries revealed the presence of MB in the middle part of the LAD coronary artery and showed an intramural course within the myocardial muscle (myocardial bridging) of 1.8 cm. The proximal and distal portion of LAD along with other coronaries were having normal epicardial course.

On microscopic examination, the area of myocardium supplied by the LAD coronary artery beyond the myocardial bridge showed the multiple foci of myocardial infarctions along with early changes of infarction such as the waviness of myocardial fibers, oedema, and a few inflammatory cells [Figure 1]. Focal perivascular fibrosis was also noted. Bridging of LAD coronary artery in its mid portion was noted along with the mild intimal thickening and neo-myointimal proliferation in the rest of the subendothelial portion resulting in approximately 30%–35% of luminal reduction of the blood supply. Proximal and distal part of LAD coronary artery did not show any atherosclerotic changes. There was no evidence of cellular or antibody mediated rejection. C4d immunostaining was negative.
Figure 1: (a) The Left anterior descending (LAD) coronary artery in its proximal portion in subepicardial location (arrow),(b) The LAD coronary artery embedded in the myocardium “Myocardial bridging” (Red Arrow), (c) Hematoxylin and eosin (H and E 40×) stained section shows LAD coronary artery entrapped between myocardial fibers, so called “Tunneled or bridged” coronary artery. (d) (H and E ×100) and (e) (H and E ×400) - shows multiple foci on non-regional myocardial infarction with signs of early infarction as intermyocytes oedema, waviness of the myocardial fibers, few inflammatory cells and fibrosis

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The most common causes of sudden death following transplantation, early (<3 months) are complications of transplantation, hyper-acute rejection or acute cellular rejection or antibody mediated rejection (graft failure), graft coronary artery disease, cardiac arrhythmia, multisystem organ failure, and infection. While late (>3 months) causes of death following heart transplantation are the complications of non-cardiac surgery, graft failure, post-transplant lymphoproliferative disorder, infections, chronic kidney disease, and malignant neoplasm.[4],[5] While important donor related causes include rejection, cardiac allograft vasculopathy, hemorrhage, infection, embolism or infarction, malignancy, donor age, drug abuse, etc.[4],[5],[6]

Myocardial bridging is an enigma due to its occurrence in different studies, and the clinical manifestations of this phenomenon may be complicated with severe cardiovascular diseases. Whether the MB contributes to heart diseases and has a decisive effect on life threatening situations is still under research. Several studies have been conducted to clarify the significance of MB in ischemic heart disease.[2],[3]

MB does not lead to any significant hemodynamic changes when it is superficial and short. Deep and long MB on the other hand is associated with severe ischemia, and increased myocardial fibrosis that can lead to sudden cardiac death, which may be due to electrical instability as a result of myocardial fibrosis in MB.[2],[3] The segment proximal to the myocardial bridging has been associated with atherosclerosis rather than the myocardial bridging segment itself. Both hemodynamic and structural changes, such as blood flow disturbance, myocardial under perfusion, and endothelial damage can be noted in the coronary artery segment proximal to a myocardial bridge.[1],[2],[3]

To conclude, MB is a diagnostic challenge as it may be found in any age group. The patient may remain asymptomatic. This enigmatic entity is usually diagnosed at necropsy or autopsy studies. MB, though rare, should be kept in mind while treating a young patient complaining of chest pain with other clinical features of cardiac ischemia.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Hostiuc S, Rusu MC, Hostiuc M, Negoi RI, Negoi I. Cardiovascular consequences of myocardial bridging: A meta-analysis and meta-regression. Sci Rep 2017;7:14644.  Back to cited text no. 1
    
2.
Cutler D, Wallace JM. Myocardial bridging in a young patient with sudden death. Clin Cardiol 1997;20:581-3.  Back to cited text no. 2
    
3.
Ker WD, Neves DG, Damas AS, Mesquita CT, Nacif MS. Myocardial bridge and angiotomography of the coronary arteries: Perfusion under pharmacological stress. Arq Bras Cardiol 2017;108:572-5.  Back to cited text no. 3
    
4.
Alexander RT, Steenbergen C. Cause of death and sudden cardiac death after heart transplantation: An autopsy study. Am J Clin Pathol 2003;119:740-8.  Back to cited text no. 4
    
5.
Chantranuwat C, Blakey JD, Kobashigawa JA, Moriguchi JD, Laks H, Vassilakis ME, et al. Sudden, unexpected death in cardiac transplant recipients: An autopsy study. J Heart Lung Trans 2004;23:683-9.  Back to cited text no. 5
    
6.
Ganesh JS, Rogers CA, Banner NR, Bonser RS, Group S. Donor cause of death and medium-term survival after heart transplantation: A United Kingdom national study. J Thorac Cardiovas Surg 2005;129:1153-9.  Back to cited text no. 6
    

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Correspondence Address:
Sudheer Arava
Additional Professor, Department of Pathology, AIIMS, New Delhi
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/IJPM.IJPM_370_19

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