This is the first reported case of intracardiac thrombus following a scorpion sting in a child. A 12-year old boys was brought with a history of scorpion stings on his left hand during sleep 6 hours prior to presentation. He had developed excessive sweating, cold extremities and breathlessness following the sting. The clinical picture and the description of the scorpion favored Indian Red Scorpion (Mesobuthus Tumulus), the species most prevalent in this region. On examination the child was conscious with a heart rate of 160/min respiratory rate 40/min, SpO2 of 88% and blood pressure of 100/70 mmHg. He had cold extremities with excessive sweating. Cardiac examination revealed tachycardia with gallop rhythm. He had bilateral wheeze and crepitations. All his peripheral pulses were palpable. Neurological examination was normal. There was no significant history.
His investigation revealed Hb of 14 gm/dl, leukocyte count 24 x 103/iL and platelet count 356 x 103/iL. X-ray chest revealed evidence of pulmonary edema. EGG revealed T-wave inversion. Tele-echocardiography done on day one in association with cardiologist from Narayana Hrudayalaya, Bangalore, revealed impaired left ventricular function with ejection fraction of 25% and tricuspid regurgitation. A diagnosis of scorpion sting with myocarditis with pulmonary edema was made and he was treated with oxygen, prazosin and Dobutamine infusion. His severity of tachypnea and tachycardia decreased over 36 hours. Repeat tele-echocardiography done after 48 hours revealed impaired left ventricular function with ejection fraction of 40% and left ventricular thrombus attached to apex measuring 15.4 x 7.9 mm. He was started on I.V. heparin and antithrombotic dose (5 mg/kg/day) of aspirin with monitoring of APTT. Meanwhile his coagulation profile (BT, CT, PT & APTT) and fibrin degradation levels done were normal. On day six repeat tele-echocardiography did not reveal the thrombus and left ventricular function had improved with ejection fraction of 60%. The patient was discharged after 8 days and repeat tele-echocardiography done after 15 days was normal.
Discussion:
Indian Red Scorpion (Mesobuthus Tumulus), the scorpion involved in our case, the commonest poisonous scorpion in our region. The venom of the M. Tumulus can affect various tissues and organs including the heart, brain, lung, pancreas and blood.
The various metabolic changes following a scorpion sting might be responsible for increased risk of thrombosis. There is an increase in the free fatty acids (EFA) levels along with simultaneous reduction in tri-glyceride levels following envenomation 2, 3, 4. Increased catecholamine, Glucagon, cortisol and changes in insulin secretion 3, 5, 6, might be responsible for increased FFA following envenomation. The catecholamines stimulate a hormone sensitive lipase which increases FFA concentration and inhibits insulin secretion 7. The increased FFA levels, by altering the function of the platelets may increase the tendency to thrombosis and may result in DIC 3.
The effect of 1-epinephrine, which plays a significant role in the initiation of thrombosis results from binding of 1-epinephrine to alpha-2 adrenergic receptors on the platelet surface. Treatment of platelets with insulin not only increases prostacycline receptor concentration on the platelet surface, but also results in the reduction of alpha-2 adrenergic receptors on the platelet surface. As such, platelet exposure to insulin prevents 1-epinephrine induced potentiation of platelet aggregation by other aggregating agents 8, 9. Thus, after scorpion envenomation increased epinephrine and decreased insulin also contribute to platelet aggregation and thrombosis.
The metabolic changes following the scorpion sting along with decreased cardiac contractility and stasis of blood in the left ventricle might have led to the formation of thrombus in the left ventricle in our case.
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