Left Main Aneurysm

Case Study: Left Main Aneurysm

Introduction:

Left main coronary artery (LMCA) aneurysms are of extremely low incidence (0.1% in adults) and is often an incidental finding at coronary angiograms (ref 1). Coronary artery aneurysm (CAA) exist when the dilatation of the vessel exceeds the diameter of the lumen by a factor of at least 1.5 (ref 2). The aetiology is still not well understood nevertheless in 50% to 90% of cases atherosclerotic disease of the coronary arteries via repeated destruction and remodelling of the media layer of the vessel wall is the culprit (ref 3). This case report presents a patient who was referred for coronary angiography prior to mitral valve replacement.  CT angiogram was also performed to further delineate the surrounding anatomy. The patient successfully underwent surgery for coronary artery bypass grafts (CABG), mitral valve replacement and Maze procedure.

Figure 1: Pre-operative Coronary Angiography demonstrating LMCA aneurysm & proximal LAD stenosis

Figure 1: Pre-operative Coronary Angiography demonstrating LMCA aneurysm & proximal LAD stenosis

Figure 2: 3D reconstruction of aneurysm

Figure 2: 3D reconstruction of aneurysm

Figure 2: 3D reconstruction of aneurysm

Figure 2: 3D reconstruction of aneurysm

Case History:

The patient was a 50 year old Aboriginal lady whose significant
past medical history included:

  • Biventricular failure
  • Worsening rest and exertional dyspnoea, associated with paroxysmal nocturnal dyspnoea, orthopnoea and peripheral oedema, associated with marked reduction in exercise tolerance
  • Ex-heavy smoker
  • Ex-heavy alcohol intake
  • Past episodes of community acquired pneumonia.

Clinical examination showed:

  • The patient  was extremely dyspnoeic
  • Oxgen saturation on room air was 90%
  • Elevated jugular venous pulse
  • She was tachycardic with a heart rate of 140 bpm and her ECG showed evidence of atrial flutter with variable block
  • Her blood pressure was approximately 110/80 mmHg
  • She had evidence of severe mitral regurgitation on auscultation and had pitting peripheral oedema to her mid thigh bilaterally
  • Abdominal examination showed that she had hepatomegaly and possible underlying ascites.

Diagnostic tests:

Patient was admitted to the Coronary Care Unit (CCU) and underwent aggressive diuresis with an intravenous Frusemide infusion.  Over the next week, the patient lost approximately 8.5 kilograms in fluid.  Continuous cardiac monitoring showed that she was in atrial flutter with variable block.

Transthoracic echocardiography: Showed evidence of severe mitral regurgitation secondary to anterior leaflet perforation with windsock and severe prolapse suggestive of past infective endocarditis.  The left ventricle was mildly dilated and had overall normal preserved systolic function.  There was moderate dilatation of the right ventricle with severe systolic dysfunction.  There was severe biatrial enlargement with mild tricuspid regurgitation and the pulmonary artery systolic pressure was 50 mmHg.  Following aggressive diuresis, the left ventricular function improved from an ejection fraction of 40% to 53%, however, the mitral regurgitation remained severe.

Pre-operative coronary angiography:
Revealed a very large aneurysm of the left main coronary artery which obscured the origin of the LAD and circumflex coronary arteries. There was probable mild to moderate proximal left main stenosis.  The LAD had a moderate narrowing, approximately 50-60% of the origin with otherwise mild irregularities elsewhere.  The intermediate coronary artery was a small calibre vessel.  The circumflex coronary artery was a large and dominant vessel with moderate to severe proximal disease.  The right coronary artery was a non-dominant vessel with no significant obstructive disease.  The left ventriculogram showed evidence of moderate dilatation of the LV with mild to moderate global impairment of systolic function.  There was severe mitral regurgitation into a hugely dilated left atrium.

CT coronary angiography: Showed a very large aneurysm in the distal left main coronary artery.  This measured 20 x 14 x 13 mm. This extended into the origins of the circumflex, first acute marginal and the LAD. The major vessels beyond the aneurysm were of moderate calibre with no haemodynamically significant stenoses.  There was mild left and moderate right ventricular global systolic dysfunction with features of pulmonary arterial hypertension.  There was thrombus present in the right atrial appendage.  There was also pulmonary mosaic density which was thought to be due to inflammatory airways disease and supported by the presence of mild basal bronchiectasis. The other differential included pulmonary hypertension and thromboembolic disease.

Treatment:

Underwent coronary artery bypass grafting x 1, mitral valve replacement and a Maze procedure of the left atrium. Vessels grafted included LIMA to LAD and saphenous vein graft to OM1.  The mitral valve was replaced with a 29mm Mosaic mitral valve prosthesis.  The findings during the operation were a dilated right atrium and right ventricle with organised clot in the right atrium.  Examination of the anterior mitral leaflet of the mitral valve showed it to be thin and flail with marked perforations.  A Maze procedure was also performed inter-operatively. Post-operative transthoracic echocardiography demonstrated a normal left ventricular size and systolic function with mild right ventricular dilatation and mild to moderate systolic dysfunction.   The Mosaic mitral valve prosthesis was functioning normally.

Discussion:

Percutaneous obliteration of LMCA aneurysm has been previously described (ref 4,5) using a PTFE covered stent and can be an option instead of surgical treatment. The current case report was not suitable for percutaneous intervention as the patient had extensive coronary artery disease and mitral valve replacement had to be performed. The American College of Cardiology (ACC) recommended CABG (ref 3) “…due to the size and location of the aneurysm, and the extent of concomitant CAD”. MRI scanner to rule out any extracardiac aneurysm was not performed but would have been of interest. To this day coronary angiography is still the gold standard to diagnose this type of pathology.

Authors:

Eric Simillion: BSc. (Medical Imaging Technology) PG Dip MIS, Curtin University, Australia.

Dr. Shakeeb Razak MBBS; FRACP (Cardiology), at Royal Perth Hospital.

Reference(s)

  1. Elahi MM, Dhannapuneni RV, Keal R. Giant left main coronary artery aneurysm with mitral regurgitation. Heart 2004:90: 1430.
  2. Lima B, Varma SK, Lowe JE. Monsurgical management of left main coronary aneurysm. Tex Heart Inst J. 2006; 33(3): 376-379.
  3. Gassis SA, Helmy T.‘Left main coronary aneurysm’ from American College of Cardiology website :http://www.cardiosource.com/casestudies/Casestudy.asp?StudyID=397&tabID=2845&reset=397#
  4. Young JJ, Schreiner AD, Shimshak TM et al. Successful exclusion of a left main coronary artery aneurysm with a PTFE-covered coronary stent. J Invasive Cardiology  2004;16:433-434.
  5. Strozzi M, Ernst A, Banfic L. Obliteration of a left main coronary artery aneurysm with a PTFE-covered stent. J Invas Cardiol 2002;14:280–281.

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