Stress triggers different pathophysiological mechanisms in younger and older cardiomyopathic hamsters

Abstract

Because cardiomyopathic hamsters (CMHs) in the lesion-forming period of their disease are more susceptible to the lethal effects of stress than older CMHs, we tested the hypothesis that different pathophysiological effects of stress may occur: coronary vasospasm in younger CMHs and congestive heart failure in older ones. CMHs aged 2.5 and 6.5 months were stressed with 2 h supine cold immobilization for 5 consecutive days. Three, 5 and 7 days after stress, the hearts were excised and perfused using a modified Langendorff system. Maximum +/- dP/dt, developed pressure, ventricular relaxation time (Tau) and coronary vascular resistance (CVR) were recorded and CVR was also measured following coronary infusion of arginine vasopressin (AVP). Stress produced ventricular dysfunction (decreased maximum +/- dP/dt, developed pressure, and increased Tau) in older CMHs (P < 0.05) but not in younger CMHs. Baseline CVR in younger CMHs was significantly higher than in older CMHs (P < 0.01) and AVP infusion produced a bigger increase in CVR in younger stressed CMHs than in either younger nonstressed or older stressed CMHs (P < 0.05). The younger CMH heart exhibits greater resting vascular tone and stress produces coronary vasoconstriction that is consistent with coronary spasm. In contrast, the older CMH experiences a decrease in cardiac function which remains 7 days after stress and indicates an exacerbation of CHF from the mild form existing prior to stress. The lethal effects of stress may occur because of the activation of different pathological processes in younger and older CMHs.