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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 he

ad and neck procedures.

Causes of Perioperative Cardiac Arrhythmias

Abnormalities of cardiac impulse formation (sma

ll 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 ImpactTachyarrhythmias:

Reduce diastolic ventricular filling Decrease cardiac output and BP Coronary perfusion suffers Myocardial ischemia

Significant bradyarrhythmias also decrease cardiac output

Anesthsia and ArrhythmiaHigher 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 surg

ery 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 cardiov

ersion Without WPW syndrome: Vagal maneuver, adenosine, Ca++ channel blo

cker 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 dr

ugs Pacing Catheter ablation

Ventricular Arrhythmias

Benign Ventricular premature beats and nonsustained v

entricular tachycardia 6.3% incidence of VPBs, only 0.62% severe adverse o

utcomes 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 ca

rdiac 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;86:1397-424

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