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Abstract
Cardiac dysrhythmias are common during the perioperative period.
Understanding dysrhythmias is a cornerstone in the practice of anesthesia.
Understanding anatomy and physiology of conductive system is the basis to understand dysrhythmias. Conductive system consists of sino-atrial node, atrioventricular node, bundle of his and bundle branches.
On the molecular level, cardiac ion channels play the pivotal role in electrical function of the heart. Cardiac ion channels are important to regulate ion movement across the cell membrane. The most important ion channels are sodium, potassium , calcium and chloride channels. Major ion currents move through them forming the action potential (AP).
Action potential consists of five stages and varies according site in the heart.
Some regions in the heart have the property of automaticity, i.e. the ability to generate action potential. Impulse propagation depends on excitability, conductivity and refractoriness.
Pathophysiological mechanisms responsible for dysrhythmias include disorders in impulse formation and disorders in impulse conduction. Disorders in impulse formation include abnormal automaticity and triggered activity. Disorders in conduction include conduction block and reentry. Mechanism may be combined.
Diagnosis of dysrhythmias depends on proper preoperative history, clinical examination and investigations. Electrocardiogram ECG is the main diagnostic tool.
Diagnosis of the cause and/or associated disorders is important.
Types of dysrhythmias include supraventricular dysrhythmias, ventricular dysrhythmias and heart block. Diagnosis of specific type depends on the rate, the rhythm, the relation between P-wave and QRS complex and the shape of QRS.
Significant (dangerous) perioperative dysrhythmias include high grade AV block, Mobitz type II AV bock, third degree heart block, symptomatic ventricular dysrhythmias, supraventricular dysrhythmias with uncontrolled ventricular rate, symptomatic bradycardia and a newly diagnosed ventricular tachycardia.
An enormous number of stimuli are possible causes of perioperative dysrhythmias. For example, anesthetic drugs, sympathetic or vagal outflow, hypoxemia, hypercarbia, endocrinal factors, malignant hyperthermia, electrolyte and acid base imbalance, cardiac disease and many other factors. Understanding and management of them is the start point to manage preoperative dysrhythmias.
Available lines of treatment include pharmacological treatment, electrotherapy and surgical intervention.
Understanding principle, indications, complications and limitation of each method is important for any anesthesiologist The proper management of perioperative dysrhythmias can improve the anesthetic outcome, which is the aim of all anesthesiologists.