BackgroundMarijuana is the commonest illegal drug used in the USA. Legalizing its use as a medical drug is a long-standing debate opposed by the federal government. Marijuana consists of delta-9-tetrahydrocannibol (THC) as an active ingredient. The body has two target receptors for THC in the nervous system: CB(1) and CB(2). CB(1) is located centrally and in some peripheral neurons while CB(2) is located peripherally only. THC medicates its effects on the cardiovascular via the autonomic nervous system Acutely, it causes increase heart rate, precipitating angina in patient with coronary artery disease, atrial fibrillation, supine hypertension, and orthostatic hypotension. Chronic use results in an overstimulation of the parasympathetic nervous system, thus causing sinus bradycardia, and an episode of transient secondary heart block has being reported.Case ReportA 46-year-old black female presented with a syncopal episode lasting for less than a minute. Prior to the episode she felt dizzy and diaphoretic. The dizziness she noted started 1 week ago. The patient was otherwise well, with no history of diabetes, hypertension, or coronary artery disease. There was no medication at home and no recent travel. However, she smoked 2 "bags " of marijuana almost daily for 15 years. Her pulse was 35 b/min; other aspects of her physical examination were normal, except she complained of dizziness lying supine. ECG showed sinus bradycardia with 2:1 AV block. CXR was normal. Since the patient had symptomatic bradycardia a temporary transvenous pacing was put in place. An echo done subsequently was normal except for paradoxical septal movements secondary to pacemaker rhythm. Myocardial infraction was ruled out, and urine toxicology was negative; however, she was not tested for cannabis. Lyme titer and work-up for connective tissue diseases were also negative. Twenty-four hours after temporary wire placement ECG showed complete heart block. The patient was then observed for 72 hours for possible resolution of heart block; however, it persisted, and a permanent pacemaker was inserted.Teaching PointWith the push for medical marijuana use and high frequency among the teenage population any reportable side effects should be taken seriously. The person using marijuana and experiencing persistent dizziness should be encouraged to seek medical attention immediately.