Journal of Cardiovascular Diseases & Diagnosis Stenting of the Left Main Coronary Stenosis

Acute myocardial infarction induced by left main coronary artery (LMCA) stenosis is the infrequent but fatal disease. LMCA stenosis occurs in 4-10% whereas lethal total occusion of LMCA occurs in 0.04-0.42% of angiograms. We report the case of 52 years diabetic obese male with central chest pain for one week; electrocardiogram (ECG) shows ST elevation in leads aVR, V1-V4, and coronary angiography displays stenosis of LMCA (>80% occlusion). The high risk primary angioplasty with drug eluting stent was performed in the unprotected LMCA without any complications.


Introduction
In most of the individuals, the common stem of left coronary artery is short. Left coronary artery has significant role in myocardial contractility as it supplies the left ventricular anterior wall, one third of the right ventricular free wall, the left and the right ventricular apex, a large part of the ventricular septum, and one half of the posterior wall [1]. Any critical stenosis or total occlusion of left main coronary artery results in rapid fatality and might causes grave complications like acute myocardial infarction, ventricular fibrillation, heart failure, cardiogenic shock or death [2][3][4]. The total occlusion of LMCA is very rare around 0.04-0.42% whereas stenosis of LMCA is frequent with 4-10% of total angiograms [4]. Here we discuss the stenosis of LMCA which undergoes successful primary angioplasty with drug eluting stent without any complications.

Case Report
A 52 years diabetic obese male (BMI 31 kg/m 2 ) came to the emergency department with a complaint of intermittent central chest pain with increase in frequency and duration for last one week. He has been smoking for last 20 years with 1 pack per day (20 pack years). He occasionally consumed alcohol. His father died due to acute myocardial infarction at the age of 50 years. He is taking metformin 500 mg two times day for last 10 years. He is not taking any medication for ischemic heart disease. On examination, the patient looked anxious, with pulse 110/min regular and blood pressure of 140/86 mm Hg. The jugular venous pressure and carotid pulse were normal. The ascultation of heart and lung detected no abnormalities. Standard 12 leads electrocardiogram showed ST elevation in aVR (>0.05 mv) and V1-V4 (>0.2 mv), pathological Q wave in leads V1-V4 and ST depression in inferior leads (II, III and aVF) as shown in (Figure 1). The cardiac enzymes were elevated with Myoglobin (157.0 ng/ml), Troponin I (14.10 ng/ml) and CK-MB (37.70 ng/ml). Chest X-ray revealed no abnormalities. The blood creatinine was 0.8 mg/ dl. The echocardiography revealed normal ejection fraction (EF 55%) without any regional wall motion abnormalities. Oxygen, aspirin (150 mg), sublingual nitroglycerine (5 mg), clopidogrel (150 mg), morphine (15 mg PO), Enalapril (5 mg) and metoprolol (50 mg) were given to the patient. The quantitative coronary angiography (QCA) was performed which revealed stenosis of left main coronary artery (>80%) as shown in figure 2. An abciximab (0.25 mg/kg IV bolus followed by 0.125 mg/ kg intravenous continuous infusion for 18 hour concluding 1 hour post primary angioplasty) and intravenous heparin (5000 IU) were given.
The left main coronary artery was intubated with a 6 Frech Judkins left guide catheter with side hole and the lesion of left main coronay artery was crossed with a 0.014 inch sport coronary guidewire. The lesion of LMCA was dilated with 2.5 × 20 mm Raptor ballon at 6 atmospheric pressure. A 3.5 × 8 mm cypher stent was inserted into the left main stem at 14 atmospheric pressure with good results. After the procedure, the dye was injected which showed patency of left main stem with no residual stenosis or complications as shown in figure 3. The ST elevation on the ECG had reverted back to normal with normal cardiac enzymes with Troponin (2 ng/ml) and CK MB (3.3 ng/ml). The patient came for follow up after 6 weeks. The angiography was done which showed patency of LMCA with no complications. The patient was advised to continue clopidogrel (75 mg) for 1 year along with lifelong asprin (75 mg), enalapril (5 mg), metoprolol (50 mg twice daily) and statin (40 mg daily).

Discussion
ST elevation myocardial infarction due to LMCA occlusion causes large regions in the jeopardy mainly the left ventricle. The patient may presents with massive myocardial infarction, ventricular arrhythmia or pump failure. The mortality is very high if LMCA occlusion is associated with cardiogenic shock [2,3]. According to the classification of coronary artery predominance, there are three types of arterial distribution: type I has RCA dominant (48%), type II has combined RCA and LCA dominant (34%) and type III has LCA dominant (18%). The survival after LMCA is dependent upon the rate of occlusion and development of right to left collateral flow as seen in type I or type II arterial distribution [5,6]. The ECG is easy and rapid way of detecting AMI. It shows ST elevation in lead aVR, V1-V4; ST elevation in aVR>V1, and widespread horizontal ST depression in inferior leads, V4-V6. These ECG findings reflect an acute MI due to LMCA occlusion or triple vessels disease [7][8][9].    percutaneous coronary intervention (PCI) or CABG. Now PCI for left main is generally accepted in worldwide [10][11][12]. Spiecker et al. and Fabbicchi et al. supported the use of emergency stent placement as the quickest and the most effective way to achieve reperfusion in the critically ill patients. But they concluded that the surgical revascularization was the definitive therapy for LMCA occlusion especially for diabetic patients because PCI with stent was associated with risk of subacute stent thrombosis and late in stent restenosis [6,12]. The CABG provides revascularization for all areas involved but the time delay, major surgical procedure, post surgical pain and discomfort, wound infection; long hospital stay and logistics make this option less suitable [4]. The use of glycoprotein IIb/IIIa inhibitors, drug eluting stent and dual antiplatelet agents have been found to cause marked reduction of sub acute stent thrombosis and restenosis. Bush and coworkers support the use of PCI with drug eluting stent as the definitive revascularization strategy for many patients with acute LMCA occlusion like our cases above [13].
In the summary; acute LMCA occlusion is a rare and serious condition. The specific ECG findings like horizontal ST depression in lead V4-V6 along with ST elevation in aVR and V1 is associated with left main or severe triple vessels disease. PCI with drug eluting stent is now globally accepted procedure for left main disease like our case above.