Effects of short- and long-term left ventricular hypertrophy on coronary circulation

Although most studies suggest that coronary vasodilator responses are impaired in dogs with cardiac hypertrophy, the factors that contribute to this impairment have not been elucidated. To determine if the duration of hypertrophy was an important determinant, we studied coronary vasodilator responses in awake dogs with two-kidney renal hypertension of 6 wk (n = 11) and 6 mo (n = 8) duration. The dogs with hypertension (6 wk and 6 mo) and left ventricular hypertrophy (LVH) had about a 25% (P less than 0.05) increase in LV mass and mean arterial pressure. During maximal coronary vasodilation induced with 4.7 microM . kg-1 . min-1 iv adenosine, maximal flow was significantly decreased in both groups of hypertensive dogs, and minimal coronary vascular resistance was increased by about 50% (P less than 0.05). Minimal coronary vascular resistance was similar in dogs with 6 wk and 6 mo of hypertension and LVH. These experiments suggest that 1) mild LVH (25% increase in LV mass) can significantly decrease coronary dilator reserve and 2) within the time frame examined (6 wk to 6 mo), the duration of hypertension and LVH does not increase the coronary vascular abnormalities associated with cardiac enlargement.