The effect of vasoactive drugs on coronary venous pressure

Vasoactive drugs such as nitroglycerine, dipyridamole, isoproterenol, or noradrenaline have had their actions attributed to their effects on the coronary arterial systems and/or the myocardium. In open chest anesthetized dogs catheters were placed in a coronary artery (CA), in an obstructed peripheral coronary artery (PCA), a small peripheral coronary vein (PCV), and the coronary sinus (CS). A gradient between each site was present with a peak systolic pressure found to be 70 mm Hg (CA), 40 mm Hg (PCA), 20 mm Hg (PCV), and 5 mm Hg (CS). Nitroglycerine decreased all pressures uniformly. Dipyridamole increased pressure in the PCV so that it became similar and often exceeded the PCA pressure. Isoproterenol on the other hand augmented all pressures, but the PCV pressure was relatively more augmented than the PCA pressure. Noradrenaline had similar effects on the pressure gradients as isoproterenol. These data suggest that a significant venous gradient is present in the heart which is subject to alteration by vasoactive drugs. Nitroglycerine acts as a non-specific vasodilator as pressures in all regions fell. On the other hand dipyridamole specifically reduces the gradient between the small arteries and veins and in most instances the PCV pressure became even greater than the PCA. Thus it appears that coronary venous resistance responds to drugs quite differently than does arterial resistance.