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Biomedical subjects

V A Morant

Publications and source records attributed to V A Morant.

12 recordsLinked to original sources
PubMed1992

Flecainide therapy in patients treated for supraventricular tachycardia with near normal left ventricular function.

Concerns about the safety and efficacy of class IC antiarrhythmic agents have arisen as a result of the recent CAST data. We reviewed records of 175 consecutive patients treated with flecainide between July 1, 1988 and July 5, 1989. One hundred ten patients with normal or mildly impaired left ventricular function and symptomatic supraventricular arrhythmias were identified. Follow-up data were obtained on 102 patients for a mean of 14 months. The average duration of flecainide therapy was 13 months. Tachyarrhythmias treated included atrial fibrillation/flutter, atrioventricular reentry, and atrioventricular nodal reentry. Flecainide provided effective antiarrhythmic therapy in 62% of the patients and was discontinued in 38% of the patients. Left atrial size did not predict treatment failure. Two patients developed proarrhythmic events (nonsustained ventricular tachycardia). There were no deaths during the follow-up period. In conclusion, flecainide provides safe and effective therapy for supraventricular tachyarrhythmias in patients with normal or mildly impaired left ventricular function.

Atrial Fibrillation↗
PubMed1991

Patients with a high defibrillation threshold: clinical characteristics, management, and outcome.

Of 125 patients prepared to receive implantable cardioverter-defibrillators (ICDs) with the patch-patch configuration of the difibrillating electrodes, 23 (18%) had high (greater than or equal to 25 joules) defibrillation thresholds (DFTs). These patients had lower left ventricular ejection fractions (27 +/- 12 vs 34 +/- 13; p less than 0.03) and a higher incidence of previous heart surgery (47% vs 19%; p less than 0.01) than patients with normal DFTs but did not differ in age, type of heart disease, incidence of concomitant heart surgery, or use of antiarrhythmic medication. Defibrillators were implanted in 18 of these 23 patients, 12 during the initial surgery and six after repeat DFT testing 2 weeks later. After 22 +/- 11 months of follow-up, four patients with ICDs died (two suddenly, and two of nonsudden cardiac causes). Two patients without ICDs died of nonsudden cardiac causes. Appropriate shocks were received by five patients (29%) including both who died suddenly later. A high DFT may be more common than previously stated. It is associated with poor ventricular function and previous heart surgery. Repeated DFT testing may be useful in some patients. A high DFT does not preclude successful ICD shocks, but other therapies may provide better results.

Aged↗
PubMed1991

Implantable cardioverter defibrillator implanted by nonthoracotomy approach: initial clinical experience with the redesigned transvenous lead system.

Standard implantation procedure for the implantable cardioverter defibrillator (ICD) has traditionally required a thoracotomy approach. A newly revised nonthoracotomy defibrillator lead system that uses a single transvenous tripolar endocardial lead alone or in combination with a subcutaneous/submuscular patch lead was introduced into clinical trials in September, 1990. Fourteen patients requiring a cardioverter defibrillator for recurrent sustained ventricular tachycardia (eight patients) or aborted sudden cardiac death (six patients) were evaluated for implantation of this lead system. Primary successful lead system implantation was obtained in nine patients. The remaining five patients had unacceptably high defibrillation thresholds (DFTs) for implantation. One of the nine initially successful implants demonstrated unacceptable DFTs and cross-talk inhibition from a permanent pacemaker necessitating removal of the nonthoracotomy lead system and replacement with a conventional lead system via thoracotomy. All remaining primary implanted patients experienced successful conversion of induced ventricular fibrillation prior to hospital discharge. Continued follow-up and greater experience to confirm the durability and efficacy of the nonthoracotomy AICD lead system are needed.

Aged↗
PubMed1990

Potassium loading as adjunct treatment of repetitive ventricular arrhythmias.

To evaluate potassium supplementation as adjunct therapy for ventricular arrhythmias, consecutive normokalemic patients undergoing in-hospital antiarrhythmic therapy for ventricular tachycardia were randomly assigned to one of four groups: intravenous potassium chloride (Group I, 44 patients) v intravenous saline (Group II, 48 patients); and oral potassium chloride capsules (Group III 50 patients) v no additional treatment (Group IV, 47 patients). All groups underwent serial serum potassium determinations and 24-hour electrocardiographic monitoring. Analysis revealed no significant differences in ventricular ectopic activity among groups, and there was no significant association between serum potassium level and incidence of ventricular arrhythmias. We conclude that normokalemic patients undergoing antiarrhythmic therapy for ventricular tachycardia benefit little from concomitant short-term potassium supplementation.

Female↗
PubMed1990

Pacemaker and defibrillator combination therapy for recurrent ventricular tachycardia.

The judicious use of antitachycardia pacemakers can enhance the benefits of automatic implantable cardioverter defibrillators in certain patients. Both devices were implanted in 10 highly selected patients with drug-refractory pace-terminable sustained ventricular tachycardia. During the observation period of 8 +/- 4.8 months, the automatic pacemakers detected 1,542 episodes of ventricular tachycardia and appropriately managed 1,373. The automatic implantable defibrillator was activated at least once in every patient; on two documented occasions, the defibrillator discharged because the automatic pacemaker accelerated the tachycardia. Concomitant antiarrhythmic drugs could be reduced but not withdrawn. With meticulous device programming and testing, the two systems in combination can work synergistically to manage malignant ventricular arrhythmias in carefully selected patients.

Aged↗
PubMed1989

The use of beep-o-grams in the assessment of automatic implantable cardioverter defibrillator sensing function.

Noninvasive assessment of sensing performance in the automatic implantable cardioverter defibrillator is limited by the absence of telemetry or memory functions. The adaptation of the electrophysiological test mode into a "beep-o-gram" recording, with simultaneous audible tones and a surface electrocardiogram, was used in the confirmation of sensing malfunction. Eleven of 13 recordings in patients with documented or clinically suspected inappropriate defibrillator discharges (group 1) demonstrated evidence of definite oversensing. Nonspecific oversensing or undersensing was present in 77% of 27 randomly selected asymptomatic patients without known sensing malfunction (group 2). The sensitivity and specificity for identifying definite oversensing was 85% and 60%, respectively. The beep-o-gram system is a reliable, noninvasive means of confirming sensing malfunction in the automatic implantable cardioverter defibrillator. Its specificity is limited by the detection of subclinical sensing aberrations, to some degree related to the device's automatic gain control sensing algorithm.

Electric Countershock↗
PubMed1986

Design-dependent cross-talk in a second generation DDD pacemaker.

A unique mechanism of "cross-talk" has recently been described in the Gemini 415A DDD pacemaker in which cross-inhibition of the ventricular output stimulus may occur in the early Gemini 415A models which were manufactured with dual anodal rings interconnected by a wire. The Gemini 415A units with dual anodal rings were implanted under investigational protocol in 53 patients from September 1982 to August 1984. To date, cross-talk has been discovered in six patients during clinical follow-up, manifesting as inappropriate ventricular inhibition. Syncope was documented in one patient. Non-Cordis atrial and ventricular leads were present in all six patients and five patients had at least one chronic lead. Cross-talk was neither evident nor provokable in Gemini 415A units which had compatible Cordis lead systems. Reduction of the atrial output and/or the ventricular sensitivity prevented cross-inhibition in three patients. Cross-talk persisted in three patients despite programming to the lowest atrial output and/or ventricular sensitivity parameters. Cross-talk, spontaneous or provoked, has not occurred in 36 patients having currently designed 415A pulse generators manufactured with a single anodal ring in the ventricular connector channel. We conclude that: this unique form of cross-talk is "design-dependent" and occurs only in Gemini 415As with dual interconnected anodal rings and cannot occur in 415As manufactured with a single anodal ring; this form of cross-talk has occurred only in 415As with non-Cordis leads and appears to be a time-dependent development; reduction of the atrial output or use of pacing modes without atrial pacing or ventricular sensing can prevent cross-talk.(ABSTRACT TRUNCATED AT 250 WORDS)

Bradycardia↗
PubMed1986

Noninvasive assessment of ventriculo-atrial conduction and early experience with the tachycardia termination algorithm in pacemaker-mediated tachycardia.

Since the advent of physiologic dual chamber pacing systems, pacemaker-mediated tachycardia (PMT) has occurred and the need for invasive measurement of ventriculo-atrial conduction (VAC) has arisen. The variability in VAC and the potential for PMT often make it necessary to assess for the presence or absence of VAC at different points in time. We noninvasively evaluated 20 pacemaker patients for the presence or absence of VAC. We compared ventriculo-atrial conduction time (VACT) obtained with the atrial sense event maker with that obtained from Holter monitoring and invasive methods. The incidence of spontaneous (S) and induced (I) PMT and the efficacy of the tachycardia termination algorithm (TTA) was assessed. Fourteen of 20 had VAC with invasive or noninvasive methods. Twelve of 19 had PMT (63%); three were sustained (greater than 15 beats). We conclude that VACT assessed with the atrial sense event marker (ASEM) yielded a high correlation when compared to the Holter monitor data obtained utilizing our methodology. PMT is commonly a nonsustained (less than 15 beats) event, and the TTA is effective in sustained PMT. Myopotential sensing, atrial premature contractions and loss of atrial capture are common mechanisms in the initiation of PMT.

Adult↗
PubMedDate not supplied

Atrial pacemaker leads compared.

In order to analyze the impact of different polarity and electrode designs on the acute pacing and sensing characteristics of pacemaker leads, 80 patients with complete heart block or sinus node dysfunction undergoing pacemaker implantation received eight different leads from five manufacturers. Once the leads were positioned, volt and current thresholds, P wave, peak-to-peak, and slew rate were assessed prospectively. There was no statistically significant difference between acute pacing thresholds, sensing characteristics, or unipolar and bipolar pacing thresholds. Active fixation leads allow atrial mapping and lead placement in areas generally inaccessible to tined tip leads. This is an advantage, especially for patients with a history of open heart surgery.

Electrodes, Implanted↗
PubMedDate not supplied

Transcatheter electrical AV junction ablation: predictors of success.

The initial and long-term results of transcatheter electrical ablation in 29 patients with drug-refractory supraventricular tachyarrhythmias were analyzed. Ablation was immediately successful (defined as induction of chronic complete heart block) in 25 patients (86.2%). Among the group in whom ablation was unsuccessful, there were more patients with ectopic atrial tachycardia and a higher incidence of narrow QRS escape rhythm following the initial ablation. A His amplitude equal to or greater than 0.3 mV was correlated with success. Complications of ablation included deep venous thrombosis and ventricular arrhythmias. Post-ablation stress testing was superior to ambulatory monitoring in identifying early return of atrioventricular conduction.

Adult↗