Therapeutics of Arrythmias

• It is often problematic to determine the best drug for a given patient due to the unknown etiology of many arrhythmias, patient-to-patient variability, and the multiple actions of many antiarrhythmic drugs. Three trial-and-error approaches are widely used:

  • Empiric. That is, based upon the clinician's past experience.

  • Serial drug testing guided by electrophysiological study (EPS). This invasive technique requires cardiac catheterization and induction of arrhythmias by programmed electrical stimulation of the heart, followed by a delivery of drugs to predict the most efficacious drug(s) to use for a given patient.

  • Drug testing guided by electrocardiographic monitoring (Holter monitoring). This noninvasive technique involves 24-hour recording of a patient's ECG before and during each drug treatment to predict optimal efficacy. The recent Electrophysiologic versus Electrocardiographic Monitoring (ESVEM) study concluded that there may not be any significant difference between the predictive value of this technique compared to programmed electrical stimulation.

• Before beginning therapy:

  • Any factor that might predispose a patient to arrhythmias (electrolyte abnormalities, hypoxia, proarrhythmic drugs, underlying disease states) should be eliminated

  • A firm diagnosis should be made before beginning therapy and a baseline ECG should be established to monitor the efficacy of treatment

• Monitoring during therapy should include:

  • Continuous and careful monitoring for efficacy and adverse effects

  • Monitoring plasma concentrations of drug, including free vs. protein-bound because of the narrow therapeutic index of most antiarrhythmic drugs

Category: Pharmacology Notes