Good Morning 20 August 2002

Anesthetic Considerations in Patients With Cardiac Arrhythmias 麻醉科 林子富

Perioperative Cardiac Arrhythmias  Incidence:  Overall: 70.2%  > 90% in cardiac surgery  Majority (90.7%): ASA 1 and 2  Without preexisting cardiac dz. or noncardiac surgery: benign and short-lived  18% to 30% (conventional intermittent EKG) vs. 60% to 80% (continuous Holter)  Common factors:  Tracheal intubation, extubation & known heart dz.  More frequently observed in neurologic, thoracic and head and neck procedures.

Causes of Perioperative Cardiac Arrhythmias  Abnormalities of cardiac impulse formation (small portion) :  In normal automaticity:  Bradycardia and escape beats with high dose narcotics  In abnormal automaticity:  A less negative diastolic potential  In triggered automaticity:  Etopic beat activated by preceding action potential “Early afterdepolarization” during phase 3 “Delayed afterdepolarization” during phase 4  Abnormalities of impulse conduction:  Re-entry excitation (most common mechanism underlying premature beasts and tachyarrhythmias)

Physiologic Impact  Tachyarrhythmias:  Reduce diastolic ventricular filling  Decrease cardiac output and BP  Coronary perfusion suffers  Myocardial ischemia  Significant bradyarrhythmias also decrease cardiac output

Anesthsia and Arrhythmia  Higher incidence  Anesthetic agents altering cardiac impulse generation and conduction  Volatile agents causing AV dissociation  Perioperative ischemia and elevated catecholamine level  Light anesthetic levels  Hypoxemia  Hypercarbia  Exogenous epinephrine and aminophylline

Sinus Node Dysfunction  Transient  Autonomic implication  Neuraxial blockade, laryngoscopy, endotracheal instrumentation  B1 agonist  Atropine  Cardiac pacing

Paroxysmal Supraventricular Tachycardia  Onset and termination are usually abrupt.  Higher incidence in major vascular, cancer, and orthopedic surgery  Death rate in non-cardiac surgery remains high: 50%  Causes of PSVT:  AV node and accessory pathways re-entry: 85% to 90%  SA node and intra-atrial re-entry: casual mechanism  Narrow-QRS PSVT  With WPW syndrome: Vagal maneuver, adenosine, B-bloker, and cardioversion  Without WPW syndrome: Vagal maneuver, adenosine, Ca++ channel blocker followed by cardioversion  Wide-QRS PSVT  IV procainamide and amiodarone and cardioversion

Atrial Fibrilattion  >90% of SVTs in the post-op setting  Etiology:  Cardiac cause  Systemic process  Electrolyte imbalance  If ventricular rate increases in an acute fashion perioperatively leading to significant hemodynamic perturbation, treatment should be prompt.  Verapamil, esmolol, digoxin  DC cardioversion  Acute onset ( <1year)  LA diameter < 45mm  No ventricular enlargement  Prior anticoagulation for arrhythmias older than 4 to 5 days

Atrial Flutter  Less frequently encountered  Same etiological factors as AF  Not typically responsive to antiarrhythmic drugs  Pacing  Catheter ablation

Ventricular Arrhythmias  Benign  Ventricular premature beats and nonsustained ventricular tachycardia  6.3% incidence of VPBs, only 0.62% severe adverse outcomes  Structurally normal hearts  Reduction of VPBs and NSVT in GA

Ventricular Arrhythmias  Potentially malignant  Sustained monomorphic ventricular tachycardia  >90% previous infarction leading to LV dysfunction  Antiarrhythmic effects of volatile agents (animal study)  Lidocaine, procainamide, amiodarone  High-energy cardioversion

Ventricular Arrhythmias  Malignant  Polymorphic ventricular tachycardias  Mostly due to torsades de points or acute ischemia  Significant prolongation of the Q-T interval  Correction of ischemia  Asynchronous DC cardioversion  Repletion of K+ and Mg++  Atropine and isoproterenol ( not in ischemia )  V-pacing  Lidocaine or phenytoin  Ventricular fibrillation  High-energy shock  Drugs only for prevention of recurrence

Summary  Common but most are transient and benign  Greater implications in the presence if significant cardiac structural abnormality  Special challenges of the operative setting  Hypo- and hyper-tension, low-flow rate, volume overload, high catecholamine state, hypoxia, hypercarbia, temperature alterations, and pericardial tamponade …  Antiarrhythmics with their proarrhythmic potential  Devices for cardioversion, defibrillation, and pacing and familiarity with their use..

References 1. Anesthetic Considerations in Patients With Cardiac Arrhythmias, Pacemakers, and AICDs. International Anesthesiology Clinics 39(4):21-42,2001 Fall 2. Perioperative Cardiac Dysrhythmias diagnosis and management. Anesthesiology 1997;86:

Have A Nice Day