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Biomedical subjects

W M Miles

Publications and source records attributed to W M Miles.

66 records · Page 4Linked to original sources
PubMed1984

Propafenone treatment of recurrent ventricular tachycardia: comparison of continuous electrocardiographic recording and electrophysiologic study in predicting drug efficacy.

Propafenone was administered to 29 patients who had multiple episodes of recurrent ventricular tachycardia (VT) or ventricular fibrillation (VF) despite previous antiarrhythmic therapy. All patients had 24-hour continuous electrocardiographic recording and electrophysiologic study in a drug-free control state and while receiving maximum doses of propafenone. During propafenone treatment, the mean frequency of ventricular premature complexes (VPCs) decreased 74% (p less than 0.05). There was more than an 83% decrease in VPC frequency in 17 of 29 patients, and 11 patients had 99 to 100% decreases. Propafenone prevented VT induction at electrophysiologic study in 6 patients, whereas another 12 patients were judged to have satisfactory electrophysiologic responses on the basis of slower VT rates and absence of hemodynamic compromise during VT. After long-term treatment from 2 to 26 months, 9 patients continued propafenone without evidence of recurrent arrhythmia. Six of these 9 patients had not VT induction at electrophysiologic study while receiving propafenone. The decrease in VPC frequency produced by propafenone was a poor predictor of a successful electrophysiologic study and of long-term therapy. In conclusion, propafenone has potential as an effective antiarrhythmic agent, but better methods to stratify risk for recurrence of VT and VF are needed.

Adult↗
PubMed1984

Development of the implantable transvenous cardioverter.

The development of the transvenous cardioverter, from the initial animal studies, to the clinical studies using temporary leads, to the initial permanent implants is described. Shocks less than or equal to 2.0 joules synchronized to the QRS complex and delivered through a specially designed catheter electrode placed in the apex of the right ventricle successfully terminate most episodes of ventricular tachycardia in patients. The implanted unit which also serves as a demand ventricular pacemaker, can be used to perform programmed electrophysiologic studies. Future devices must be capable of defibrillation and more accurate arrhythmia detection.

Aged↗
PubMed1984

Early experience with an implantable cardioverter.

We tested the efficacy and safety of a fully programmable cardioverter weighing 95 g, in terminating sustained ventricular tachycardia. The device was implanted tranvenously under local anesthesia in seven patients. On command from a programmer or automatically, the cardioverter delivered shocks through a lead inserted to the apex of the right ventricle. It also served as a demand ventricular pacemaker and could perform programmed ventricular stimulation or overdrive pacing. Cardioversion of ventricular tachycardia required less than 0.5 J (mean) and was well tolerated by the patients, who were awake and not sedated. In one patient, a shock terminated ventricular tachycardia with the device in the automatic mode but produced atrial fibrillation with a rapid ventricular response that was intermittently recognized as ventricular tachycardia, triggering additional shocks. One such shock in the ST segment produced ventricular fibrillation that was terminated transthoracically in the emergency room, without residual impairment. We conclude from these preliminary observations that cardioversion of sustained ventricular tachycardia by means of an implantable catheter device is feasible, but for the present its use in the automatic mode must be cautious and selective. The unit's small size, ease of implantation, usefulness for noninvasive electrophysiologic studies, programmability, and bradycardia pacing functions are advantages. The next-generation device must be able to defibrillate and provide better differentiation of arrhythmias.

Adult↗
PubMed1984

Evaluation of the patient with wide QRS tachycardia.

Acute and long-term therapy as well as prognosis in patients with wide QRS tachycardia differ depending on the mechanism of the arrhythmia. Twelve-lead electrocardiography and prolonged electrocardiographic monitoring are often diagnostic. However, additional techniques such as esophageal and right atrial electrocardiography, or His bundle electrocardiography with detailed electrophysiologic studies, are sometimes necessary to delineate the mechanism of the arrhythmia.

Adult↗
PubMed1984

Clinical use and pharmacology of amiodarone.

Amiodarone, an investigational drug in the United States, has had considerable use in this country and worldwide in the treatment of cardiac arrhythmias. This article reviews the clinical pharmacology of this potentially useful antiarrhythmic agent.

Amiodarone↗
PubMed1984

Preexcitation syndromes. Mechanisms and management.

Ventricular preexcitation occurs when, in relation to atrial events, some or all of the ventricular muscle is activated earlier by the atrial impulse than would be expected if conduction of the impulse activated the ventricles by way of the normal atrioventricular conduction system. The purpose of this article is to review the pathophysiology of the variants of preexcitation and to discuss the therapeutic approach to patients who have tachyarrhythmias.

Anti-Arrhythmia Agents↗
PubMed1984

Synchronous intracardiac cardioversion.

The concept of synchronous transvenous cardioversion of sustained ventricular tachycardia is discussed. This article reviews the animal experience, initial and collective studies in patients, and results of permanent implantation in two patients.

Aged↗
PubMed1984

Future directions: electrical therapy for cardiac tachyarrhythmias.

Directions and research opportunities in basic animal and clinical investigations and in industry that relate to the application and development of electrical devices which control tachyarrhythmias are presented. In basic research, a better understanding of mechanisms responsible for tachyarrhythmias , their onset and methods of termination, would provide increased rationale for selecting a particular therapeutic approach. Knowing the distribution in the heart of applied electrical current when delivered by different types of electrodes placed at different myocardial sites would be helpful. Clinically, we must develop appropriate algorithms to accurately differentiate sinus tachycardia, the various forms of supraventricular tachycardias and ventricular tachycardia. These must be incorporated into future cardioverters and defibrillators . In industry, new sensors, electrodes, expanded telemetry capabilities and implanted microprocessors will aid in creation of a universally applicable generic form of electrical therapy that can be programmed to treat any form of tachycardia.

Animals↗
PubMed1984

Initial experience with Symbios Model 7008 pacemaker.

The Symbios 7008 pacemaker is capable of treating both bradycardias and tachycardias. In this report, we summarize operation of the pacemaker and the initial experience in 21 patients who have received implants. All patients have supraventricular tachyarrhythmias that have been terminated successfully with automatic atrial burst pacing (19 patients) or AV sequential pacing. More than half of the patients also have bradyarrhythmias requiring pacing and thus benefit from both functions of the device. Experience to date has been favorable.

Adult↗
PubMed1984

Preliminary experience with the implantable transvenous cardioverter.

A synchronized shock of less than or equal to 2.0 joules delivered over a specially designed catheter electrode passed to the apex of the right ventricle effectively terminates sustained ventricular tachycardia in dogs and in patients. The capability has been engineered into a 95 gram device implanted using lidocaine anesthesia, which is also capable of VVI pacing and of performing programmed electrophysiologic studies. Seven patients have received the implant and the initial experience is described.

Aged↗
PubMedDate not supplied

Ablative therapy for ventricular arrhythmias.

Radiofrequency catheter ablation techniques have enjoyed successful applications in patients with a wide variety of supraventricular tachycardias, especially the Wolff-Parkinson-White syndrome and atrioventricular nodal reentry. More recent reports have shown successful applications in patients with atrial tachycardias and atrial flutter. In addition to these, there are now reports of success during attempts to use radiofrequency techniques to eliminate ventricular tachycardia (VT), both in patients without structural heart disease (idiopathic VT) and patients with structural heart disease (primarily coronary artery disease). Techniques to map sites for ablation in patients with idiopathic VT usually include identifying early endocardial activation and using pace mapping. Success rates for ablation of idiopathic VT have been very high (over 90%) in patients with VT arising from the right ventricular outflow tract. Success rates have not been quite as high when VTs arising from sites other than the right ventricular outflow tract are targeted in the patient with idiopathic VT. In patients with VT caused by coronary artery disease, early endocardial activation and pace mapping can be unreliable. In these patients, searching for mid-diastolic potentials or showing concealed entrainment have proved more reliable. When these latter techniques are applied, success rates in eliminating a single focus of VT in a patient with coronary artery disease has been reported to be as high as 60% to 80%. Future therapies will include new energy sources, new (larger and/or cooled) electrodes, and multipoint catheter mapping, possibly using body surface mapping techniques.

Adult↗