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Biomedical subjects

M M Scheinman

Publications and source records attributed to M M Scheinman.

At least 181 records · Page 10Linked to original sources
PubMed1986

Catheter ablation for patients with cardiac arrhythmias.

Catheter ablative techniques have recently been introduced as therapy for patients with drug-resistant cardiac arrhythmias. These techniques include delivery of high-energy direct-current shocks in order to electrocoagulate the atrioventricular junction for those with supraventricular arrhythmias. This technique, if successful, results in arrhythmia control but induces chronic pacemaker dependency. The evidence, to date, suggests that 90% of these patients are improved after attempted atrioventricular junctional ablation. Catheter ablative procedures have been used for attempted ablation of accessory pathways and has been shown to be especially effective for those with posteroseptal accessory pathways. More recently, techniques for ablation of ventricular tachycardia foci have been introduced but experience with this procedure is too limited to allow for definitive recommendations.

Adolescent↗
PubMed1986

Catheter atrioventricular junctional ablation in patients with accessory pathways.

Seven patients with accessory pathway and symptomatic atrioventricular reciprocating tachycardia underwent catheter ablation of the atrioventricular junction (AVJ). Four patients had the Wolff-Parkinson-White syndrome, two had concealed left free-wall accessory pathways, and one patient had a nodoventricular connection. All patients failed multiple antiarrhythmic drugs and one failed attempted surgical ablation of a posteroseptal accessory pathway. Chronic interruption of atrioventricular node-His conduction was achieved in all patients. Over a mean follow-up period of 21 +/- 14 months, four patients remained asymptomatic without antiarrhythmic therapy. One patient developed atrial fibrillation after magnet application to her VVI pacemaker, another developed atrial flutter, and a third had nonparoxysmal sinus or atrial tachycardia. Two patients required chronic quinidine therapy. Two patients with concealed accessory pathways had pacemaker-mediated tachycardia which was controlled by pacemaker reprogramming. Atrioventricular junctional ablation in patients with accessory pathways proved effective in that all are currently controlled without need for surgical intervention. On follow-up, a relatively high incidence of atrial arrhythmias requiring antiarrhythmic therapy was found.

Adult↗
PubMed1986

Catheter ablation for control of ventricular tachycardia: a report of the percutaneous cardiac mapping and ablation registry.

Catheter ablation of ventricular tachycardia is a procedure of last resort in critically ill patients. The Percutaneous Cardiac Mapping and Ablation Registry was able to collect data on 88 patients undergoing ablation of ventricular tachycardia foci. The mean following interval for the group was 10 +/- 8 months. Results were divided into three categories: Group I patients remained asymptomatic and were on no antiarrhythmic medications (33%); Group II remained asymptomatic and took antiarrhythmic agents (38%); Group III patients were considered unsuccessful and consisted of 29 percent of the total. More than one-third of patients received two shocks; the remainder received from one to five shocks. Overall mortality included four procedure-related deaths and total follow-up mortality was 25 percent. Catheter ablation for ventricular tachycardia should be undertaken only in highly specialized centers with an expert and experienced electrophysiologist with immediate surgical back-up available.

Adolescent↗
PubMed1986

Ablation therapy for patients with supraventricular tachycardia.

Over the past decade, a more complete understanding of the mechanisms of supraventricular tachycardia has made possible the development of surgical and catheter techniques designed to control these arrhythmias. Ablative techniques are generally used when the arrhythmia proves refractory to drug and/or antitachycardia pacing therapy or when lifelong drug therapy is believed to be less desirable than a potentially curative procedure. In this essay, we explore the known mechanisms for supraventricular arrhythmias as well as the rationale for the use of ablative techniques.

Atrioventricular Node↗
PubMed1986

Clinical and electrophysiologic characterization of automatic junctional tachycardia in adults.

Junctional ectopic tachycardia has been described in infants but not in adults. Five adults with rapid symptomatic paroxysmal junctional tachycardia, distinct from the more common slower nonparoxysmal junctional tachycardia, were recently evaluated. The tachycardia was irregular (rate 120 to 250) and accompanied by periods of atrioventricular dissociation and narrow QRS complexes. A junctional origin was documented during electrophysiologic study in four of the five patients. Analysis of Holter recordings; the response to exercise, isoproterenol, and propranolol; and the effects of atrial and ventricular stimulation appeared to implicate abnormal automaticity of a high junctional focus that was catecholamine sensitive or dependent as the tachycardia mechanism. All patients responded somewhat to beta-blockers, although a combination of procainamide and propranolol proved to be the most effective therapy in one patient and another chose electrode catheter ablation of the atrioventricular junction rather than continued drug therapy. Thus, junctional ectopic tachycardia may occur in adults and its mechanism appears to be related to abnormal automaticity that is catecholamine sensitive or dependent. Initial therapy should include beta-blockers but selected patients may require more aggressive management.

Adult↗
PubMed1986

Use-dependent effects of lidocaine on conduction in canine myocardium: application of the modulated receptor hypothesis in vivo.

Lidocaine is a commonly used antiarrhythmic drug that causes use-dependent blockade of sodium channels in vitro and reduces conduction velocity in vitro and in vivo. According to the modulated receptor hypothesis of antiarrhythmic drug action, lidocaine has a low affinity for rested sodium channels but a high affinity for open and inactivated channels. In the present experiments, we characterized use-dependent conduction slowing and recovery from slowing by lidocaine in anesthetized dogs. The His-to-ventricular conduction interval was used as the indicator of conduction velocity. We found that prolongation of conduction time was greater as the stimulation frequency was increased. Moreover, on abruptly changing the stimulation frequency, a new steady-state conduction time was approached in two to three depolarizations. On discontinuation of stimulation, the conduction time of progressively less premature extrastimuli shortened exponentially with a terminal phase time constant of 152 +/- 115 msec. These effects by lidocaine were enhanced during acidosis and enhancement was reversed by correction of the acidosis. It is concluded that the effects in vivo of lidocaine on conduction under several conditions of rate, rhythm, and pH are similar to its effects on the maximum upstroke velocity of the action potential in vitro. Although these experiments were not designed to validate the modulated receptor hypothesis, it appears that the modulated receptor hypothesis can predict the effects of lidocaine on conduction in vivo.

Animals↗
PubMed1986

Polymorphous ventricular tachycardia: clinical characterization, therapy, and the QT interval.

Forty-five consecutive patients with polymorphous ventricular tachycardia (PVT) were studied. The arrhythmia proved to be of a drug-related cause in 27 and due to an electrolyte disorder in four patients. Coexistent cardiac diseases without metabolic or drug-related abnormalities included ischemic heart disease in three, cardiomyopathy in three, and mitral valve prolapse in two. PVT was exercise-induced in four and associated with bradyarrhythmias in two. A prolonged QT or corrected QT interval was inconsistently related to the occurrence of PVT. In patients in whom PVT was induced by certain type I drugs, other type I antiarrhythmic drugs were usually either ineffective or resulted in aggravation of arrhythmia. For the group as a whole, treatment with lidocaine resulted in inconsistent beneficial effects, while cardiac pacing was almost universally effective for those with drug-induced PVT, regardless of the length of the QT interval. Long-term amiodarone therapy proved safe and effective for 12 of the 24 patients with drug-induced PVT who required long-term therapy for their original arrhythmia. We conclude that identification of PVT is the key clinical issue and that the QT interval is not necessarily the prime abnormality nor the variable to be considered in predicting success of therapy. Temporary cardiac pacing appears to be very effective in the short-term management of these patients. Use of type I antiarrhythmic agents in patients with drug-induced PVT generally resulted in aggravation of arrhythmia. In contrast, long-term amiodarone therapy for control of the original arrhythmia appears to be a promising approach for those with PVT associated with type I agents.

Adolescent↗
PubMed1986

Histologic changes and arrhythmogenicity after discharge through transseptal catheter electrode.

Ventricular tachycardia commonly arises within the intraventricular septum and successful catheter ablation of septal tachycardia might be enhanced by transseptal electrode placement. We have evaluated the safety of a transseptal ablation procedure. Arrhythmogenicity and histology were examined after high-energy capacitor discharges were delivered to an intracavitary cathode-anode pair placed on opposite sides of the interventricular septum in pentobarbital-anesthetized dogs. After two discharges of 200 or 100 J proved lethal, paired discharges of 30 or 50 J (10 dogs) or a single discharge of 100 J (four dogs) was used to induce 28 lesions. Acute rhythm changes and risk of induction of ventricular tachycardia by programmed stimulation were measures of arrhythmogenicity. Gross and histologic examination of the hearts after 20 min to 28 days allowed characterization of the evolution of lesions. The conduction system in nearby and remote locations was extensively examined in four dogs. Refractory ventricular fibrillation developed with paired shocks at 200 or 100 J. At lower energy levels, acute ventricular fibrillation occurred with 12 of 20 shocks (60%), but defibrillation was consistently achieved. After ablation, no dog had ventricular tachycardia or fibrillation induced with programmed stimulation. Matching anodal and cathodal lesions spanned the septum without perforation in 10 of 16 dogs, and the lesions were of similar histology. Each contained central areas of hemorrhage surrounded by a region of coagulation necrosis merging with normal myocytes peripherally. There was necrosis and edema without inflammation at 20 min, acute inflammatory cell infiltration at 1 to 2 days, and myocyte replacement by granulation tissue after 6 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Ablation of cardiac tissues by an electrode catheter technique for treatment of ectopic supraventricular tachycardia in adults.

Five patients with chronic or recurrent ectopic supraventricular tachycardias unresponsive to drugs underwent programmed stimulation, endocardial mapping, and attempted catheter ablation of the arrhythmia focus. For attempted ablation, an intracardiac electrode catheter was positioned near the exit point of the tachycardia and served as the cathode while a chest wall patch served as the anode. In two patients with tachycardia originating near the coronary sinus, discharges of 200 or 400 J each were delivered to two electrodes at the earliest area of endocardial activation. These two patients with incessant tachycardia remain free of tachycardia for 17 and 11 months, respectively. In one patient with tachycardia originating from the right atrial appendage, both catheter and surgical ablation proved unsuccessful in that a new focus of atrial tachycardia supervened. This patient subsequently underwent successful catheter ablation of the atrioventricular junction. Two patients with junctional tachycardia underwent catheter ablation of the atrioventricular junction. Complete atrioventricular block followed atrioventricular junctional ablation and these patients required permanent cardiac pacing. The junctional tachycardia was replaced by sinus rhythm with episodes of unsustained atrial tachycardia. However, after 13 +/- 5 months follow-up, neither of the patients require antiarrhythmic drugs. Catheter ablation can be effective for atrial foci near the coronary sinus os, and can be performed with preservation of atrioventricular conduction. Arrhythmia ablation is possible in those with atrioventricular junctional tachycardia but requires the sacrifice of atrioventricular conduction. After ablation, other automatic atrial foci may become operative and complicate use of dual-chamber pacemakers.

Adolescent↗
PubMed1986

Catheter ablation techniques in patients with supraventricular tachycardia.

Catheter ablation is an experimental procedure that may prove useful for patients with drug-refractory supraventricular tachycardia. Current techniques involve the use of high-energy direct-current shocks, delivered via electrode catheters. These techniques have been used most commonly for ablating the atrioventricular (AV) junction in patients with supraventricular tachycardia. Such ablation may be of value in a subset of patients with the Wolff-Parkinson-White syndrome. In addition, limited data suggest that direct catheter ablation of posteroseptal accessory pathways may prove safe and effective when shocks are applied just outside the os of the coronary sinus. Catheter ablation has also been used in small numbers of patients with ectopic atrial tachycardia. The chief limitation of catheter ablation of the AV junction is the induction of pacemaker dependency. Successful ablation of an accessory pathway or of an ectopic atrial tachycardia focus obviates the need for long-term pacing. For many reasons, catheter ablation represents an exciting approach to the management of patients with drug-refractory supraventricular tachycardia.

Journal Article↗
PubMed1985

Cardiac arrest and sudden death in patients treated with amiodarone for sustained ventricular tachycardia or ventricular fibrillation: risk stratification based on clinical variables.

Multivariate analysis of 11 clinical variables was performed in 104 patients with sustained, symptomatic ventricular tachycardia (VT) or ventricular fibrillation treated with amiodarone to determine variables predictive of subsequent cardiac arrest or sudden death. Twenty-five patients (24%) had fatal or nonfatal cardiac arrest after 7.3 +/- 6.2 months (mean +/- standard deviation) of therapy. Multivariate analysis identified an ejection fraction of less than 0.40, syncope or cardiac arrest before amiodarone therapy, and VT (3 or more consecutive ventricular premature complexes) during predischarge ambulatory electrocardiographic monitoring as variables associated with a high risk of subsequent fatal or nonfatal cardiac arrest (p less than 0.03). Patients who had these 3 clinical variables had a much higher predicted incidence of cardiac arrest at 6 months (62%) and 12 months (76%) than did patients with an ejection fraction greater than 0.40, without syncope or cardiac arrest before amiodarone therapy, and without VT during predischarge ambulatory electrocardiographic monitoring (2% and 5%, respectively) (p less than 0.02). Risk stratification using clinical variables can predict which patients are at high risk of recurrent cardiac arrest or sudden death during amiodarone therapy.

Aged↗
PubMed1985

Electrophysiologic and anatomic changes in the atrioventricular junction of dogs after direct-current shocks through tissue fixation catheters.

Barb-tipped fixation electrode catheters were inserted under fluoroscopic control in the region of the atrioventricular (AV) node in 6 dogs. A series of direct-current shocks (20 to 240 J) were delivered from the electrode catheter to a back plate. Serial electrophysiologic studies were performed before and 2 to 3 weeks after delivery of the shocks. In general, low-energy shocks--20 to 180 J--resulted in predominant damage to the approaches to the AV node, the AV node and common bundle, whereas larger shocks created diffuse damage involving the His bundle and bundle branches. Despite histologic damage to the AV junction, only minimal changes in AV conduction were observed. Thus, there is a large safety margin for AV conduction.

Animals↗
PubMed1985

Clinical significance of ventricular fibrillation-flutter induced by ventricular programmed stimulation.

Two hundred twenty-four patients underwent ventricular programmed stimulation (VPS) without prior documentation of the clinical occurrence of sustained ventricular tachycardia (VT) or ventricular fibrillation-flutter (VF). Indications for VPS were: palpitations or nonsustained VT during ambulatory monitoring (85 patients), syncope or presyncope (137 patients), and a family history of sudden death (two patients). Sustained VF requiring transthoracic defibrillation was initiated by VPS in 18 patients (8.0%). Four patients were treated for inducible VF with antiarrhythmic agents directed by electropharmacologic testing; five patients were treated empirically; nine patients received no therapy. No patient has had a cardiac arrest or sudden death during a follow-up period 25.2 +/- 13.8 months (mean +/- standard deviation). VF was initiated by two ventricular extrastimuli in three patients and by three extrastimuli in 15 patients. The incidence of VF was similar in patients with and without previous symptoms (8.8% vs 6.9%) or heart disease (7.1% vs 9.6%). It was significantly higher when VPS at three ventricular sites with a current of 5 mA (pulse width 2 msec) was compared to programmed stimulation at two ventricular sites with a current twice diastolic threshold (pulse width 2 msec) (15.2% vs 3.0%, p less than 0.05). VF initiated by VPS in patients without prior VT or VF appears to be a nonspecific finding. Antiarrhythmic therapy for VF may not be necessary in these patients.

Adult↗