Envenomation by Hemiscorpius lepturus is not painful and the clinical manifestations include bloody urine due to hemoglobinuria or hematuria, dermonecrotic reactions, cardiac arrhythmia and in minority of cases acute renal failure which may lead to death following disseminated intravascular coagulation in infants. Cardiac effects of envenomation by H. lepturus venom including inotropic, chronotropic and arrhythmogenic properties are not studied as now in rat hearts with Langendorff apparatus.Rat hearts were allowed to equilibrate in its buffer and cardiotropic plus arrhythmogenic effects induced by injection of different doses of H. lepturus venom were detected and recorded by computer acquisition based data in Langendorff apparatus. The neutralizing effects of Razi Institute antivenom and autonomic drugs were assayed in parallel studies.Hemiscorpius lepturus venom (25 μg/100 l) treatment caused a negative inotropic (65.4 ± 3.2 versus 110.2 ± 3.4) and chronotropic effects (186.3 ± 4.2 versus 302 ± 6.3) in comparison to normal saline. Arrhythmogenic aspects including bradycardia, QRS widening and ST depression were induced by venom injection. Pre venom treatment (20 min) of Razi Institute antivenom (10 μl) neutralized cardiotropic effects but post venom injection (15 min later) had no therapeutic role. Pre (10 min before) and post (15 min after) injection of adrenaline (10 μl) neneutralized cardiotropic effects while pre venom injection (20 min) of propanolol (10 μl) had aggravating effects.Our study paves the way for further in vivo investigation of cardiovascular effects of this venom for finding suitable treatments instead of its ordinary antivenom medication in cardiogenic shock induced by the venom.