Systemic and cardiac neuroendocrine activation and severity of myocardial ischemia in humans

The purpose of this study was to assess the effect of different degrees of ischemia on circulating and cardiac neurohormones and vasotone.

Neuroendocrine activation and subsequent systemic vasoconstriction may complicate ischemia. Whether this relates to severity of ischemia and subsequent cardiac dysfunction, and whether neurohormonal balance in the ischemic area changes, is unknown.

Fifty-six normotensive patients with coronary artery disease were evaluated during incremental atrial pacing. On the basis of ST segment changes, patients were classified in a nonischemic (n = 11) or ischemic group (n = 45), the latter patients were subsequently classified as lactate (n = 28) or nonlactate (n = 17) producing, to identify neurohormonal changes in the effluent of the ischemic myocardium.

Angina occurred in 55%, 82% and 82% of patients in the nonischemic, lactate- and nonlactate-producing groups, respectively. Baseline hemodynamic variables and neurohormones were comparable in all groups, as were heart rate, rate-pressure product and coronary hemodynamic variables during pacing. In lactate producers, contractility did not improve, relaxation deteriorated, left ventricular filling pressure increased and cardiac output decreased during pacing, indicating more severe ischemia compared with that in nonlactate producers. Neurohormones did not change in the nonischemic group. In contrast, arterial and coronary venous catecholamines increased significantly more in lactate producers than in nonlactate producers (arterial norepinephrine by 68% vs. 36%, respectively). Moreover, arterial angiotensin II increased in lactate producers from a baseline mean +/- SEM of 6.8 +/- 0.9 to 9.7 +/- 1.6 pmol/liter (p < 0.05), accompanied by a sustained 23% increase in systemic resistance and arterial pressures. In lactate producers, baseline net cardiac norepinephrine release changed to net uptake during pacing (-0.05 +/- 0.02 vs. 0.06 +/- 0.05 nmol/min, p < 0.05). Epinephrine uptake increased in all patients with ischemia, albeit more in lactate producers.

Circulating catecholamines and renin-angiotensin levels are activated, and systemic vasotone is increased in relation to the degree of ischemia. Cardiac epinephrine uptake increases, whereas net baseline norepinephrine release from the ischemic myocardium changes to net uptake. Modulation of this neurohormonal activation may provide an alternative mode to limit ischemia.