Autonomic effects on the human cardiac conduction system. Evaluation by intracardiac electrocardiography and programmed stimulation techniques.
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Biomedical subjects
W F Heddle
Publications and source records attributed to W F Heddle.
Atrial pacing in ventricular tachycardia and supraventricular tachycardia with aberrant intraventricular conduction: diagnostic and therapeutic implications.
The diagnostic and potential therapeutic value of rapid right atrial pacing in ventricular tachycardia and supraventricular tachycardia with aberrant intraventricular conduction, was examined. The effect of right atrial pacing at incremental rates beginning 10 bpm above the rate of the tachycardia was studied in five patients with ventricular tachycardia, and in four patients with supraventricular tachycardia with rate-related bundle branch block aberration, the mechanism of tachycardia having been demonstrated at electrophysiology study. Atrial pacing resulted in persistent (four) or occasional (one) normalisation of the QRS complexes to that seen in sinus rhythm in those five patients with ventricular tachycardia. The intraventricular conduction pattern persisted with atrial pacing in those patients with supraventricular tachycardia and aberrant intraventricular conduction. This confirms that atrial pacing is a useful and simple diagnostic test in wide QRS tachycardia, which does not require sophisticated electrophysiological facilities. In three of the patients with ventricular tachycardia, atrial pacing terminated the arrhythmia, suggesting potential therapeutic use of rapid atrial pacing in such patients.
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Association of sick sinus and Lown-Ganong-Levine syndromes.
A 38-year-old woman presented with syncopal attacks for 27 years. The electrophysiology techniques which enabled the diagnosis of both sinus node dysfunction (sick sinus syndrome) and presence of an atrionodal bypass tract (Lown-Ganong-Levine syndrome) are illustrated.
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Intermittent atrioventricular block: procainamide administration as a provocative test.
Twelve patients with clinical features suggesting possible intermittent high degree atrioventricular block were studied. All 12 patients had basic 1:1 atrioventricular conduction but nine had an electrocardiographic pattern of bifascicular distal conduction disease (right bundle branch block with left anterior or posterior hemiblock, or left bundle branch block). Intracardiac conduction was assessed by recording of the His bundle electrocardiogram and atrial pacing techniques, before and 20 minutes after intravenous administration of procainamide, in a dose of up to 10 mg/kg. Before procainamide administration, seven of the 12 patients had a prolonged H-V interval (greater than 55 ms). Procainamide administration lengthened the H-V interval in all 12 patients by 5--40 ms. In five patients, procainamide induced second or third degree AV block below the level of the bundle of His. It was concluded that the administration of procainamide may be a useful provocative test of distal conduction in patients with possible intermittent AV block.
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Verapamil in prophylaxis of paroxysmal atrioventricular nodal reentrant tachycardia.
We examined by electrophysiologic study and clinical follow-up the use of verapamil as a prophylactic agent in 13 patients with refractory paroxysmal supraventricular tachycardia due to atrioventricular (AV) node reentry. Electrophysiologic variables and initiation and maintenance of AV nodal reentry were studied by programmed electrical stimulation. Observations were made before and after intravenous administration of verapamil, 0.15 mg/kg. Twelve of the 13 patients had previously not been controlled by other antiarrhythmic agents. Before verapamil, AV nodal reentry was induced in all 13 patients. Verapamil increased AV nodal transmission time (AH interval), as well as the effective and functional refractory periods of the AV node. Reentry could not be initiated in 5 of the 13 patients after verapamil and was nonsustained in a further 3. The echo zone for atrial premature beats which initiated tachycardia decreased in 2 of the remaining 5 patients. The rate of tachycardia was also significantly decreased. Over a mean follow-up period of 16 months, 11 of the 13 patients had definite symptomatic improvement, with decrease in frequency, duration, and/or associated symptoms of their arrhythmia. Only 1 patient had side effects which necessitated withdrawal of the drug. It was concluded that verapamil is a useful agent in the management of such patients.
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