Isolated<unk> <unk>  is poorly specific for a LMCA. The following are other causes of<unk><unk> :
Nontraumatic thoracic aortic dissection
Massive Pulmonary Embolism
Massive GI bleed
Left bundle branch block (LBBB)
Left Ventricular Hypertrophy (LVH) with Strain Pattern
Severe atrial tachydysrhythmias
AVR ST elevation
Cardiac
T wave changes
ST-segment elevation myocardial infarction 
ST segment depression
Post-MI 
De Winter's T waves
Previous MI with recurrent ischemia in same area