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Neurochemical approaches to the prevention of ventricular fibrillation
Abstract:
Current evidence indicates that susceptibility to ventricular fibrillation (VF) can be reduced by decreasing cardiac sympathetic activity and by increasing vagal tone. Pharmacological agents that favor such a pattern of autonomic outflow protect the heart against fibrillation. These include morphine sulfate, clonidine, digitalis drugs, and bromocriptine. An intriguing new approach involves changing the serum concentration of amino acid precursors of the central neurotransmitters that modulate autonomic traffic. Considerable evidence indicates that accumulation of serotonin in the brain reduces sympathetic neural activity. When L-tryptophan or 5-hydroxytryptophan is administered with phenelzine (a monoamine oxidase inhibitor) and carbidopa (a selective peripheral L-amino acid decarboxylase inhibitor) to raise brain serotonin, a significant increase in myocardial electrical stability is observed. This effect results from a decrease in cardiac sympathetic tone as indicated by selective denervation and nerve recording studies. Enhancing serotoninergic neurotransmission can also significantly reduce vulnerability to VF during acute coronary artery occlusion. The effect of augmenting serotoninergic activity without the use of enzyme inhibitors has been investigated by administering agents such as melatonin, 5-methoxytryptophol, and 6-chloro-2-(1-piperazinyl) pyrazine (MK-212). Each of these substances increases cardiac electrical stability. The protective influence is unaffected by bilateral vagotomy but is blocked by the specific serotonin antagonist methergoline. Diminution of cardiac sympathetic drive appears to be the main mechanism of action. Thus, neurochemical interventions can exert a profound effect on cardiac electrical stability. Recent advances in neurochemistry and psychopharmacology promise new insights into the problem of sudden death and suggest a fresh approach for the management of life-threatening arrhythmias.
Insights
Modulating the autonomic nervous system, particularly by enhancing serotonin, can significantly improve cardiac electrical stability and reduce the risk of ventricular fibrillation (VF). This neurochemical approach offers a promising strategy for managing life-threatening arrhythmias.
Area of Science:
- Neurocardiology
- Autonomic Nervous System Regulation
- Cardiac Electrophysiology
Background:
- Ventricular fibrillation (VF) susceptibility is influenced by cardiac sympathetic activity and vagal tone.
- Pharmacological agents can modulate autonomic outflow to protect against fibrillation.
- Neurochemical interventions targeting central neurotransmitters represent a novel approach.
Purpose of the Study:
- To investigate the effects of modulating central neurotransmitter precursors on cardiac electrical stability.
- To explore the role of serotonin in reducing sympathetic drive and preventing ventricular fibrillation.
- To assess the efficacy of various neurochemical agents in enhancing myocardial electrical stability.
Main Methods:
- Administration of L-tryptophan or 5-hydroxytryptophan with enzyme inhibitors (phenelzine, carbidopa) to increase brain serotonin.
- Administration of agents like melatonin, 5-methoxytryptophol, and MK-212 to augment serotoninergic activity.
- Evaluation of cardiac electrical stability through selective denervation, nerve recording studies, and assessment during acute coronary occlusion.
- Testing the influence of vagotomy and serotonin antagonists (methergoline) on the observed effects.
Main Results:
- Increased brain serotonin levels led to enhanced myocardial electrical stability.
- Augmenting serotoninergic neurotransmission significantly reduced vulnerability to ventricular fibrillation.
- Agents like melatonin and MK-212 also increased cardiac electrical stability.
- The protective effect was mediated by a decrease in cardiac sympathetic drive and was independent of vagal tone.
Conclusions:
- Neurochemical interventions, particularly those enhancing serotoninergic activity, profoundly impact cardiac electrical stability.
- Decreasing cardiac sympathetic drive is the primary mechanism for preventing ventricular fibrillation through these interventions.
- Advances in neurochemistry and psychopharmacology offer new strategies for managing sudden cardiac death and arrhythmias.