Isolated heart block in snake bite: Recurrent syncope as presenting symptom

A 44-year-old healthy male with no prior comorbid conditions, presented to our emergency department with recurrent syncopal attacks, each lasting for 2 minutes for 2 days. He had a history of an unknown snake bite 2 days ago following which he developed syncopal attacks. He had received 20 vials of anti-snake venom. His vital parameters were normal and a mark of the snake bite was present on the right ankle. Central nervous system examination was normal. Electrocardiogram revealed complete right bundle branch block with 2:1 Mobitz type 2 block (Fig. 1).

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FIG 1.

Electrocardiogram suggestive of severe bradycardia with complete right bundle branch block and 2:1 Mobitz type 2 block

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The big 4 snakes¹ are Indian cobra (Naja naja), the common krait (Bungarus caeruleus), the Russell viper (Daboia russelii) and the saw-scaled viper (Echis carinatus). Cardiotoxicity due to snake bite is poorly described in the literature. Viper toxin is more commonly associated with adverse cardiovascular events.² Electrocardiographic changes include sinus arrhythmia (6.6%), myocardial ischaemia (10%), non-specific ST-T changes (16.7%) and atrioventricular block (3.3%).³ Case reports of cardiac tamponade,⁴ Takotsubo cardiomyopathy,⁵ acute myocardial infarction,⁶ and cardiogenic pulmonary oedema,⁷ have been described.

We emphasize that a trivial syncopal attack can be the presenting symptom of a dangerous snake bite.