Case presentation
A 26 years old young medical intern presented with complains of dizziness and recurrent syncope. At presentation his pulse was 42/min, blood pressure-100/70 mm of Hg, temperature-98.1F and respiratory rate 16/min. The rest of physical examination was within normal limits. Electrocardiogram (ECG) on presentation showed high grade atrioventricular block [Figure:1(a) and 1(b)]. There was no improvement in the heart rate by administration of intravenous atropine . Patient admitted to using marijuana since last 4 years and in preceding two years he was smoking 5-8 joints (4-5 grams) daily. Clinically possibility of congenital complete heart block (CHB) or CHB due to chronic use of Marijuana was kept in differential diagnosis.
His tonsillectomy was done 9 years back and at that time pre-anaesthetic check ECG was within normal limits. The routine medical check-up at the time of admission to medical collage was also normal, as per records. There was no family history of any heart disease .
The blood counts and metabolic panel were within normal limit (Supplementary table 1). Serological tests for syphilis, lymes disease, hepatitis B, hepatitis C and HIV were negative. Serial troponin-I reports did not show any elevation, patient’s thyroid stimulating hormone was normal. Urinary screen 11-Nor-9-carboxy THC was positive (18ng/ml). The chest x-ray was normal. There was no evidence (clinical/ biochemical or radiological) to suggest rheumatic, sarcoid heart disease or myocarditis. On 2D-echocardiography cardiac chambers and valves were normal with normal left ventricular function (Ejection fraction=66%). On EP study the base line rhythm was 2:1 AV block with following parameters; AH interval -180ms, HV interval - 85 ms, PP interval -648ms, RR interval -1274ms [Figure 2(a)]. High grade supra-his (nodal) AV block was observed while atrial pacing at 600ms cycle length [Figure 2(b)]. Coronary angiography was suggestive of normal coronaries.
Dual chamber pacemaker was implanted and patient was discharged in stable condition. At discharge ECG was showing ApVp (atrial paced ventricular paced) rhythm which changed to AsVp (atrial sensed ventricular paced) and then AsVs (atrial sensed ventricular sensed) rhythm over a period of 3 months.