Stoelting's Anesthesia and Co-Existing Disease · 8th Edition
Abnormalities of Cardiac Conduction and Cardiac Rhythm
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Key Takeaways
- Five-lead ECG monitoring using leads II and V5 detects approximately eighty percent of perioperative myocardial ischemia affecting inferior and lateral ventricular walls.
- Atrioventricular blocks progress in severity from first-degree conduction delay to third-degree complete heart block, which requires immediate transcutaneous or transvenous pacing.
- Supraventricular tachyarrhythmias present narrow QRS complexes and include paroxysmal supraventricular tachycardia, atrial fibrillation, atrial flutter, and Wolff-Parkinson-White syndrome.
- Ventricular dysrhythmias from premature contractions to ventricular fibrillation require urgent intervention with amiodarone, synchronized cardioversion, or immediate defibrillation.
- Neuraxial anesthesia increases bradycardia risk through unopposed parasympathetic activity and the Bezold-Jarisch reflex, potentially causing profound bradycardia or asystole.
- Cardiac implantable electronic devices necessitate preoperative assessment and intraoperative precautions to prevent electromagnetic interference from monopolar electrocautery during surgery.
Chapter SummaryWhat this audio overview covers
Cardiac conduction abnormalities and dysrhythmias represent critical perioperative concerns requiring rapid recognition and appropriate management. The electrocardiogram serves as the fundamental diagnostic tool, with intraoperative monitoring typically utilizing a five-lead configuration that samples leads II and V5 to detect approximately eighty percent of ischemic changes across both inferior and lateral ventricular territories. Understanding the cardiac conduction system—comprising the sinoatrial node, atrioventricular node, bundle of His, bundle branches, and Purkinje fibers—is essential for interpreting ECG findings and recognizing conduction disturbances. Myocardial cells generate and propagate electrical signals through organized action potential phases involving precise ion channel regulation, ultimately triggering excitation-contraction coupling that translates electrical activity into mechanical pumping. Atrioventricular blocks range from benign first-degree delays to life-threatening complete heart block requiring immediate pacing, while intraventricular blocks such as right and left bundle branch block indicate varying degrees of conduction disruption with different clinical implications. Supraventricular tachyarrhythmias originating proximal to the bundle of His present with narrow QRS complexes and include conditions such as paroxysmal supraventricular tachycardia, atrial fibrillation, atrial flutter, and Wolff-Parkinson-White syndrome, each requiring distinctive pharmacologic or ablative approaches. Ventricular dysrhythmias ranging from premature ventricular contractions to ventricular fibrillation demand urgent intervention, with monomorphic ventricular tachycardia responding to amiodarone or synchronized cardioversion and ventricular fibrillation requiring immediate defibrillation. Bradydysrhythmias present particular concern during neuraxial anesthesia when unopposed parasympathetic activity or the Bezold-Jarisch reflex may precipitate profound bradycardia or asystole. Patients with cardiac implantable electronic devices require preoperative assessment and specialized intraoperative precautions to prevent electromagnetic interference, particularly from monopolar electrocautery. Long QT syndrome and associated acquired prolongation create vulnerability to torsades de pointes, a life-threatening polymorphic arrhythmia. Treatment modalities encompass pharmacologic interventions including adenosine, atropine, amiodarone, and epinephrine alongside electrical therapies such as synchronized cardioversion, defibrillation, and transcutaneous pacing, with catheter ablation offering definitive management for select reentrant mechanisms.