The Application of Serial Electrophysiological Testing in the Management of Patients With Ventricular Arrhythmias

Rae, Alan P (1987) The Application of Serial Electrophysiological Testing in the Management of Patients With Ventricular Arrhythmias. MD thesis, University of Glasgow.

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The lethal potential of ventricular tachyarrhythmias is well recognised and because of the ineffectiveness of empirically prescribed therapy a directed approach to the treatment of these arrhythmias is mandated. The aim of the studies in this thesis was to further define the applicability of serial electrophysiological testing for the determination of effective antiarrhythmic therapy in patients with these arrhythmias. In Chapter 1, the potential mechanisms for the development of ventricular tachyarrhythmias and their relation to the use of programmed stimulation are discussed. The prognostic impact of ventricular arrhythmias is reviewed. The therapeutic options are described and the classification of antiarrhythmic drugs is explained. The different management strategies for the prescription of antiarrhythmic therapy are discussed. The historical development and rationale for electrophysiological testing is described. The methodology and equipment required for this approach is described in Chapter 2. In particular, the stimulation protocol employed in all studies in this thesis is explained. The induction of ventricular tachyarrhythmia in response to the stimulation protocol is dealt with in Chapter 3. The varying impact of different factors including the type of underlying heart disease in the patient population being studied and the different components of the stimulation protocol are described. The comparability of the results with those reported from other laboratories confirms the utility of the stimulation protocol. The controversial aspect of sensitivity, specificity and reproducibility of programmed stimulation is discussed. In Chapter 4, the techniques for tachycardia termination and the effectiveness of pacing modalities are described. The effect of cycle length and antiarrhythmic therapy on pacing termination are discussed. The concordance between the response to electrophysio-logical testing with both intravenous and oral formulations of procainamide is dealt with in Chapter 5. The advantages of testing intravenous therapy were offset by the observation that non indueibility with intravenous procainamide was not predictive of noninducibility with oral procainamide. The results from this study confirm that retesting on oral therapy is required even if the intravenous agent is shown to be effective. The use of serial electrophysiological drug testing to identify effective therapy in patients with ventricular tachyarrhythmias related to coronary artery disease is described in Chapter 6. Overall drug efficacy, efficacy of individual regimens and the effect of the type of induced arrhythmia on drug response are detailed. The long-term effectiveness of antiarrhythmic regimens identified as successful by electrophysiological testing is confirmed using both the accepted stimulation end-point of noninducibility and the more relaxed end-point of 15 or less repetitive responses. In Chapter 7, similar results confirming the predictive value of serial drug testing were obtained for patients with ventricular tachyarrhythmias related to cardiomyopathy. The effect of the combination of amiodarone plus the Type 1 agent procainamide on arrhythmia inducibility is discussed in Chapter 8. The main benefit of the addition of procainamide was on the haemodynamic impact of the induced arrhythmia which may provide a degree of protection from sudden death. Using multivariate statistical techniques the determinants of the response to serial electrophysiological drug testing were analysed in Chapter 9. Patients with poor left ventricular function were less likely to respond to medical therapy, and suppression of arrhythmia induction was more difficult in patients with induced sustained ventricular tachycardia than in patients with either ventricular fibrillation or nonsustained ventricular tachycardia. During follow up, if recurrence of arrhythmia occurred, it was more likely to be as sudden death if the patients had cardiac failure, and the induced arrhythmia in the discharge drug study was not symptomatically tolerated. The major independent variable which predicted recurrence of arrhythmia during follow-up was failure of serial electrophysiological drug testing to identify a successful therapy. In Chapter 10, the predictive value of the response to procainamide is discussed. Failure of procainamide to suppress arrhythmia inducibility predicts failure of other agents in patients with induced sustained ventricular tachycardia but not in patients with either ventricular fibrillation or nonsustained ventricular tachycardia. The implications of these observations in the evaluation of antiarrhythmic drug efficacy are discussed. In Chapter 11, the use of programmed stimulation to reveal the potential for drug related worsening of arrhythmias is described. The different proarrhythmic responses and their potential clinical value are discussed and the lack of predictability of these responses is investigated. Important unresolved problems in the clinical application of electrophysiological testing for the management of patients with ventricular tachyarrhythmias are discussed in Chapter 12.

Item Type: Thesis (MD)
Qualification Level: Doctoral
Keywords: Medicine
Date of Award: 1987
Depositing User: Enlighten Team
Unique ID: glathesis:1987-77544
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jan 2020 11:53
Last Modified: 14 Jan 2020 11:53

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