Thrombosis of the Left Main Stem following Steroid Abuse in a 21 Year Old Male Mimicking Spontaneous Dissection

Spontaneous acute dissection of left main stem artery is an extremely rare occurrence, with less than 40 cases documented in world literature. The clinical presentation of spontaneous left main stem dissection is similar to severe atherosclerotic disease, but the usual risk factors are absent. More than 70% of SCAD occurs in women and 30% occur during peripartum period and the mean age is 30-45 years. Other causes include connective tissue disorders, SLE vasculitis, substance abuse and vigorous exercise. However, varying degree of atherosclerosis has been increasingly described in many patients with SCAD. In one series when intravascular ultrasound was used routinely to evaluate SCAD, atherosclerosis was found in 83% patients. Atherosclerosis predisposes to SCAD especially when plaque rupture causes intraluminal thrombosisand creates a deep subintimal dissection followed by intramural hematoma formation, the intima underlying the plaque having either thinned out substantially or in many cases being non-existent. Besides, the inflammatory process associated with an atherosclerotic plaque increases microvessel density and propensity to rupture at the intima-media border and predisposes to a primary intramedial dissection and medial hematoma. Intravascular ultrasound may thus not visualise an intimal tear at all either because the process was primarily that of an intramedial microvessel rupture without intimal tear, or, alternately, because the deep sub-intimal tear associated with the plaque rupture quite often seals up as a result of intraluminal clotting and increased pressure.