Anabolic steroids alter the haemodynamic responses of the canine left ventricle.
The effect of an anabolic steroid on canine left ventricular function was studied by catheterization exposing control (n = 7) and methandienone-treated (n = 6) dogs to pacing, volume and isoproterenol tests at the beginning of the experiment and 6 weeks later. The physical performance of the animals was evaluated by submaximal exercise test (SMT), in which the steroid-treated dogs had lower heart rate than the sedentary controls (P less than 0.001). Heart weight was greater in the steroid than in the control group (P less than 0.05). Isoproterenol infusion increased the maximum value of the left ventricular pressure curve (dP/dtmax) less in the steroid-treated than in the control animals (P less than 0.05). Also heart rate was lower in the steroid than in the control group after inotropic load, while end-diastolic, end-systolic and stroke volumes decreased significantly more in the control group (P less than 0.05). Systemic vascular resistance decreased in the steroid treated animals, but remained unchanged in the control group (P less than 0.05 between the groups). During volume overload dP/dtmax increased in the control group but decreased slightly in the steroid group (P less than 0.05 between the groups). The pressure-volume diagram showed that the left ventricle of the steroid-treated animals worked on higher ventricular volumes than in the control group. In conclusion, long-term methandienone treatment results in cardiac hypertrophy in dogs, reduces its response to an inotropic loads and leads to working on larger ventricular volumes.