The effects of delta 9 tetrahydrocannabinol (cannabis) on cardiac performance with and without beta blockade

Abstract

Systolic time intervals (STI) were measured in ten healthy male volunteers before and after intravenous (i.v.) administration of 25 μg/kg delta 9 tetrahydrocannabinol (Δ 9 THC). Mean ± SEM heart rate increased 32 ± 7 beats/min, while systolic and diastolic blood pressures were unchanged after Δ 9 THC. Total electromechanical systole lengthened 17 ± 4.2 msec, left ventricular ejection time (LVET) prolonged 24 ± 4.0 msec and pre ejection period (PEP) shortened 17 ± 5.1 msec after Δ 9 THC. All these changes were significant (P<0.01). In nine other subjects who underwent prior beta adrenergic blockade, similar but less marked changes were noted in heart rate, blood pressure, and STI after Δ 9 THC. The shortening of PEP after Δ 9 THC was only msec (NS) in beta blocked subjects. Thus, Δ 9 THC significantly increased heart rate, shortened PEP and prolonged LVET(c), without any change in afterload. Beta adrenergic blockade prevented significant shortening of PEP and blunted other responses. These findings suggest that Δ 9 THC enhanced cardiac performance. Partial inhibition of this effect was achieved with prior beta adrenergic blockade.