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Cardiac sympathetic activity in response to acute myocardial ischemia
G E Newton1, A G Adelman, V C Lima
1Department of Medicine, Mount Sinai Hospital, University of Toronto, Ontario, Canada.
Insights
Myocardial ischemia during angioplasty did not activate cardiac sympathetic nerves. Despite generalized sympathoadrenal activation, cardiac norepinephrine spillover decreased, indicating no direct heart sympathetic response.
Area of Science:
- Cardiology
- Neuroscience
- Physiology
Background:
- Cardiac sympathetic responses to myocardial ischemia in humans are not fully understood.
- Previous studies suggest brief ischemia doesn't cause norepinephrine overflow from the heart.
Purpose of the Study:
- To investigate cardiac sympathetic nervous system activation during brief myocardial ischemia in humans.
- To differentiate cardiac-specific responses from generalized sympathoadrenal activation.
Main Methods:
- Eleven patients undergoing angioplasty of the left anterior descending coronary artery were studied.
- Cardiac norepinephrine spillover was measured before, during, and after balloon inflation.
- Arterial norepinephrine and epinephrine concentrations were also monitored.
Main Results:
- Angioplasty induced significant S-T segment elevation and reduced transcardiac lactate extraction.
- Cardiac norepinephrine spillover significantly decreased during and after balloon inflation compared to control.
- Arterial norepinephrine and epinephrine levels increased during balloon inflation.
Conclusions:
- Brief myocardial ischemia from angioplasty does not activate the cardiac sympathetic nervous system in humans.
- Generalized sympathoadrenal activation occurs, but it does not translate to increased cardiac norepinephrine release.
- The heart's sympathetic response to acute ischemia differs from systemic responses.
Abstract:
Although experimental evidence has demonstrated that brief periods of myocardial ischemia are not associated with norepinephrine overflow from the heart, cardiac sympathetic responses to myocardial ischemia in humans remain unclear. Eleven patients undergoing angioplasty of the left anterior descending coronary artery had cardiac norepinephrine spillover measured immediately before inflation, during the final minute of a 5-min balloon inflation, and 1 min after deflation. Angioplasty caused significant S-T segment elevation and a reduction in the transcardiac lactate extraction ratio. Cardiac norepinephrine spillover was reduced from a mean value of 58 +/- 14 pmol/min at control to 41 +/- 15 pmol/min during balloon inflation and 38 +/- 14 pmol/min after deflation (P < 0.05 vs. control for both inflation and deflation values). In contrast, during balloon inflation, there were significant increases in arterial norepinephrine and epinephrine concentrations. Therefore, a brief period of myocardial ischemia caused by angioplasty of the left anterior descending coronary artery does not result in cardiac sympathetic activation, despite evidence of generalized sympathoadrenal activation.