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Biomedical subjects

M Fromer

Publications and source records attributed to M Fromer.

At least 55 records · Page 3Linked to original sources
PubMed1992

Ultrarapid subthreshold stimulation for termination of atrioventricular node reentrant tachycardia.

OBJECTIVES: We investigated the efficacy and safety of ultrarapid subthreshold electrical stimuli in terminating sustained atrioventricular (AV) node reentrant tachycardia. BACKGROUND: Subthreshold stimuli, singly and in trains, have been reported to prolong the effective refractory period, inhibit the response to subsequent suprathreshold extrastimuli and to terminate ventricular tachycardia and reciprocating tachycardia. METHODS: Seventeen consecutive patients with inducible sustained slow-fast AV node reentrant tachycardia (mean tachycardia cycle length 358 +/- 61 ms) were studied. Trains of subthreshold stimuli were tested at various right atrial sites. RESULTS: Trains of subthreshold stimuli reproducibly terminated AV node reentrant tachycardia in 15 patients without administration of adjunctive pharmacologic agents. Effective subthreshold current strength ranged from 0.5 to 1.5 mA (mean 0.9 +/- 0.3). The cycle length of effective subthreshold stimuli trains ranged from 30 to 80 ms (mean 57 +/- 17), and the number of stimuli in the train ranged from 4 to 16 (mean 8 +/- 4). The site of successful termination was the proximal coronary sinus in 6 patients and the right low atrial septum in 12. During successful subthreshold termination, no atrial capture could be detected. Neither atrial fibrillation nor flutter nor tachycardia acceleration occurred. CONCLUSIONS: Low current, high frequency trains of stimuli, when applied at a site presumed to be close to the reentrant circuit, provided a safe and effective method of terminating the common type of AV node reentrant tachycardia. This technique could be used to identify critical parts of the reentrant circuit suitable for ablation and further investigations with this method are warranted.

Adult↗
PubMed1992

Subthreshold electrical stimulation for termination and prevention of reentrant tachycardias.

Subthreshold electrical stimulation (STS) was used to terminate and prevent reentrant supraventricular and ventricular (VT) tachycardia. Of 12 patients with SVT, 8 had atrioventricular nodal (AVN) reentry, and 4 had orthodromic tachycardias. Trains of STS applied close to the AVN area terminated the tachycardias in five of the eight patients with AVN re-entry and two of the patients with orthodromic tachycardia. In 13 patients with recurrent sustained hemodynamically stable VT (mean cycle length 370 +/- 40 ms), trains of STS were delivered at the site of early activity during the tachycardia. Number of train cycles ranged between 3 to 8 pulses and their cycle lengths ranged between 20 and 70 ms. In 7 of the 13 patients VTs were effectively terminated by STS application close to the site of early activity and in the remaining 6 patients it did not. In nine patients the effect of STS applied at the site of early activity on VT induction from the right ventricular apex was examined. In four of the nine patients STS prevented VT induction and in the remaining five patients it did not. These observations suggest that STS applied in proximity to the area critical for initiation and maintenance of reentry can terminate or prevent induction of the tachycardia.

Adult↗
PubMed1992

Efficacy of automatic multimodal device therapy for ventricular tachyarrhythmias as delivered by a new implantable pacing cardioverter-defibrillator. Results of a European multicenter study of 102 implants.

BACKGROUND: Third-generation implantable cardioverter-defibrillators are devices designed to treat ventricular tachycardia (VT) and ventricular fibrillation (VF) by means of overdrive pacing, cardioversion, or defibrillation. So far, the efficacy of tiered therapy has been documented only in small series. Therefore, a European multicenter clinical evaluation study of a new tachyarrhythmia control device, the Medtronic PCD pacer-cardioverter-defibrillator with epicardial patch-lead configuration, was undertaken. METHODS AND RESULTS: We report on 102 patients (mean age, 55 +/- 13 years) from 11 European centers. PCD devices implanted between May 1989 and February 1991 were included. The patients suffered from hemodynamically significant ventricular tachyarrhythmias not suppressed by antiarrhythmic drug therapy and unrelated to acute myocardial infarction; one patient had nonsustained VT and severely depressed left ventricular function. Seventy patients had coronary artery disease with old myocardial infarctions, 23 had cardiomyopathies of various etiologies, and nine patients had no detectable heart disease. Mean ejection fraction was 36 +/- 14% (range, 10-76%). Mean intraoperative defibrillation threshold (51 patients) was 10.6 +/- 5.1 J (range, 2-18 J). The documented follow-up ranged from 1 to 21 months (mean, 9.4 +/- 5.8 months), or 79.9 cumulative patient-years. Perioperative mortality was 3.9%. The actuarial survival rate at 12 months was 91%. One sudden arrhythmic death occurred. Sixty patients (58%) received device therapy. Seventeen patients had therapies only for "VF" episodes, 16 patients only for VT, and 28 patients for VT and "VF" episodes. Based on device memory data, 1,235 spontaneous VT episodes were detected and treated in 43 patients. Twelve hundred four of these VT episodes received painless initial antitachycardia pacing therapy, restoring sinus rhythm in 91%. The 108 ongoing episodes received 209 multiple therapeutic attempts. Eighty-five additional overdrive pacing therapies restored sinus rhythm in 30%. Initial ineffective antitachycardia pacing therapies received 51 cardioversion pulses. The success rate was 61%. Seventy-three additional cardioversion pulses were delivered to backup ineffective pacing therapy as well as ineffective secondary cardioversion pulses. Their success rate was only 40%. Two hundred eighty-six spontaneous episodes were detected in 44 patients as "VF." Overall defibrillation efficacy was 97.6%. CONCLUSIONS: The implanted device nearly eliminates sudden arrhythmic death in patients with documented, potentially fatal ventricular tachyarrhythmias. Automatic tiered therapy is highly effective to restore sinus rhythm, provided that an integrated two-zone tachycardia detection algorithm is used, assigning lower tachycardia rates to overdrive pacing and/or cardioversion and higher tachycardia rates to defibrillation. In general, spontaneous VTs can be terminated by automatic overdrive pacing, and painful or disturbing countershock therapies are not required to terminate the majority of spontaneous VT episodes.

Death, Sudden, Cardiac↗
PubMed1992

[Sudden cardiac death: possibilities of interventional therapy].

There is, at present, no method to prevent sudden cardiac death. However, in patients with documented high risk the implantable automatic cardioverter defibrillator is the only reliable alternative. However, the electrical discharges of high energy may cause discomfort and pain. Antitachycardia pacing is effective for most episodes of ventricular tachycardia and can effectively reduce the number of electrical shocks to be delivered.

Death, Sudden, Cardiac↗
PubMed1992

Transcatheter ablation of cardiac tissue: advantages and disadvantages of different ablative techniques.

Transcatheter ablation techniques are emerging as an alternative therapeutical tool in the management of cardiac arrhythmias. Catheter ablation was initially introduced as the last resort to ablate the atrioventricular nodal conduction in patients with atrial fibrillation and uncontrolled ventricular response and in patients with drug refractory ventricular tachycardias. Direct current energy was used as the sole source of energy, but because of potential significant complications and early and late mortality, presumably mostly due to ventricular tachyarrhythmias, other sources of energy were sought. Radiofrequency current which does not produce barotrauma and does not require general anesthesia rapidly replaced direct current ablation in many centers. Early results with radiofrequency current ablation of the atrioventricular node and accessory atrioventricular pathways are very encouraging. The results of radiofrequency as well as direct current ablation for atrial flutter, atrial tachycardia and ventricular tachycardia, where the components of reentry circuit are less defined, are not as favorable as those of AV junctional tachycardias. However, improvement of catheter and generatory technology and better understanding of the mechanisms of ventricular tachycardias and characteristics of the target site will enhance the results of catheter ablation in ventricular tachcardias. The procedures are still considered investigational, and mostly done by very experienced groups at tertiary referral hospitals with surgical teams available in case of serious complications. Larger patient populations and longer follow-up periods are required before these techniques expand to community hospitals and to patients with minimal symptoms or asymptomatic individuals as a prophylaxis therapy.

Cardiac Catheterization↗
PubMed1991

Catheter ablation.

Catheter ablation is gaining increasing interest for the therapy of symptomatic, sustained arrhythmias of various origins. The scope of this review is to give an overview of the biophysical aspects and major characteristics of some of the most widely used energy sources in catheter ablation, e.g., the discharge of conventional defibrillators, modified defibrillators, laser light, and radiofrequency current application. Results from animal studies are considered to explain the basic mechanisms of catheter ablation. The recent achievements with the use of radiofrequency current to modify or ablate cardiac conduction properties are outlined in more detail.

Animals↗
PubMed1991

Experience with a new implantable pacer-, cardioverter-defibrillator for the therapy of recurrent sustained ventricular tachyarrhythmias: a step toward a universal ventricular tachyarrhythmia control device.

Ten consecutive patients (mean age 57.9 +/- 7.6 years) were treated with an investigational tachyarrhythmia control device, the implantable Medtronic Pacer-, Cardioverter-, Defibrillator model 7216A or 7217B. All patients had coronary artery disease with old myocardial infarctions and presented hemodynamically significant sustained ventricular tachyarrhythmias not suppressed by antiarrhythmic drug therapy and unrelated to acute myocardial infarction. In two patients a nonthoracotomy lead system was implanted. Lowest effective defibrillation energy ranged from 5 to 18 joules (mean 12.2 +/- 4 joules) for the epicardial bielectrode systems and were 15 and 18 joules for the nonthoracotomy lead system implants. The postoperative periods were unremarkable. Follow-up ranged from 7 to 19 months (mean 13.8 +/- 4.5 months). Spontaneous tachyarrhythmia episodes were detected and treated by the device in six patients, five of them received staged therapies. No deaths occurred and no hospital admissions were necessary for device related or ventricular tachyarrhythmia related complications. In conclusion, this integrated device represents a major step toward the development of a universal ventricular arrhythmia control device.

Aged↗
PubMed1991

Antiarrhythmic treatment of atrioventricular tachycardias.

Atrioventricular (AV) tachycardia includes both AV nodal reentrant tachycardia (AVNRT) and AV reentrant tachycardia (AVRT) using an accessory pathway. The treatment of the acute attack is different from the long-term treatment of both AVNRT and AVRT. Verapamil and adenosine, by prolonging the refractory period of the AV node, are highly effective in terminating acute attacks of AVNRT and orthodromic AVRT. Conversion to sinus rhythm is achieved in approximately 90% of the episodes of tachycardias with both agents given intravenously. The initial dose of verapamil is 0.075-0.1 mg/kg and a subsequent bolus of 5 mg can be given to a maximal dose of 15-20 mg. The initial dose of adenosine is 3 or 6 mg, but doses of 9 or 12 mg can be administered if smaller dosages have been unsuccessful. Other agents producing lengthening of the refractory period of the accessory pathway in AVRT or of the fast pathway in AVNRT often terminate reentry tachycardia. Such agents are class IC antiarrhythmic drugs such as flecainide or propafenone and class IA drugs such as procainamide. In patients with accessory pathways and antidromic tachycardia or atrial fibrillation conducting via an accessory pathway, treatment with verapamil or digoxin should be avoided because these agents may enhance the conduction properties of the accessory pathway, thereby leading to an increase of the ventricular rate or even to ventricular fibrillation. Prevention of AVNRT episodes can be obtained with various antiarrhythmic drugs. Digoxin alone or in combination with beta-blockers is effective in approximately 50% of the cases and especially when the combination proved to be successful during electrophysiological testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Sustained ventricular tachycardia: inducibility during invasive electrophysiologic studies].

Electrophysiologic studies are used for diagnosis and treatment in patients with sustained ventricular tachycardia. This method can only be employed if high inducibility of the spontaneous tachycardia can be demonstrated. We therefore investigated prospectively the induction yield in 35 patients with a history of documented sustained ventricular tachycardia. The patients' mean age was 58 years. Coronary artery disease was present in 24 patients, cardiomyopathy in 4, other organic heart diseases in 4, and no heart disease in 3. The ventricular tachycardia induction protocol consisted of three extrastimuli delivered during sinus rhythm and at two pacing cycle lengths, followed by intravenous isoproterenol if no tachycardia was induced before. With the method sustained ventricular tachycardia was induced in 100% of patients with coronary artery disease and cardiomyopathy, in 75% of patients with other heart diseases and in 33% of patients without detectable heart disease. We conclude that electrophysiologic studies have a high yield of sustained ventricular tachycardia induction in patients with underlying organic heart disease. The rational basis for use of electropharmacologic testing therefore exists in these patients. However, in patients without heart disease, the low sensitivity of electrophysiologic studies precludes its use for drug efficacy testing.

Adult↗
PubMed1990

Clinical efficacy of radiofrequency current in the treatment of patients with atrioventricular node reentrant tachycardia.

Eight women (mean age 41 years, range 24 to 62) with drug-resistant atrioventricular (AV) node reentrant tachycardia underwent radiofrequency catheter ablation. Radiofrequency energy was delivered in a unipolar mode with use of a back paddle as the anode placed between the two scapulae. The total applied energy was 2,233 +/- 1,919 J. The AH interval increased from 87 +/- 13 to 113 +/- 17 ms (p less than 0.05) and the PQ interval increased from 141 +/- 15 to 169 +/- 34 ms (p less than 0.05). The anterograde Wenckebach cycle length increased from 300 +/- 41 to 320 +/- 42 ms (p less than 0.05). Retrograde conduction was abolished in five patients. Atrioventricular node tachycardia was still inducible in three patients. During a follow-up period of 9 +/- 3 months, four patients remained clinically asymptomatic without drug therapy and four patients had recurrent symptoms. Three of the latter responded to previously unsuccessful antiarrhythmic drugs and the fourth patient underwent surgical cure for persistence of tachycardia. Right bundle branch block occurred in five patients; it was permanent in four and transient in one. In conclusion, radiofrequency catheter ablation represents a valuable but still investigational therapy in patients with drug-refractory AV node reentrant tachycardia.

Adult↗
PubMed1990

Is there an isolated arrhythmogenic right atrial myocarditis?

Two cases with drug refractory ectopic atrial tachycardia are described. A map-guided partial resection of the right atrium (RA) was done after preoperative endocardial catheter mapping had shown well-defined areas of fractionated RA potentials. Intraoperatively, there were no aneurysmal formations present as described by other authors. Histopathologic examination of the resected tissue showed atrial myocarditis in both patients. Postoperative right ventricular myocardial biopsies revealed no inflammatory tissue. A minor elevation of antibodies against echoviruses was found in one case. Postoperative electrophysiologic studies were negative. We conclude: focal RA myocarditis without concomitant ventricular myocarditis may represent one cause of drug-resistant ectopic atrial tachycardia. Map-guided surgical intervention may cure the disease.

Adult↗
PubMed1990

Clinical experience with a new software-based antitachycardia pacemaker for recurrent supraventricular and ventricular tachycardias.

The Intermedics Intertach 262-12 tachycardia reversion pulse generator was implanted in 14 patients (six male, eight female, mean age at implantation 45 +/- 16 years) with recurrent symptomatic tachycardias. Six patients had atrioventricular (AV) nodal reentrant tachycardia, three patients had orthodromic tachycardia with Wolff-Parkinson-White syndrome, two had circus movement tachycardia via a concealed bypass tract, two had ventricular tachycardia, one patient had atrial flutter. Mean duration of symptoms before implantation was 8 +/- 4 years and mean number of antiarrhythmic drug trials was 3.5 +/- 1. The primary tachycardia response made consisted of autodecremental pacing in one patient, burst pacing in two patients, and adaptive scanning of the initial delay or burst cycle length in eleven patients. The secondary tachycardia response mode consisted of autodecremental pacing in four patients, burst pacing in three patients and burst scanning in four patients. Tachycardia response was automatic in all but one patient with ventricular tachycardia. During a follow-up period of 30.5 +/- 10.6 months, one patient with ventricular tachycardia died from a nonarrhythmic cause. Reinterventions were necessary due to electrode fracture in one patient and due to pacemaker software defect in another one. Two patients underwent surgical cure of their arrhythmia: one patient with atrial flutter and one patient with AV nodal reentry tachycardia, 24 months and 11 months postpacemaker implantation, respectively. Four patients required digitalis to prevent pacing induced atrial fibrillation. Other proarrhythmic effects were not encountered. The pacemaker proved to be a versatile system with reliable tachycardia detection and termination functions. It provided a valuable adjunctive therapy in these selected patients.

Adult↗
PubMed1990

Ten-years follow-up of 20 patients with idiopathic ventricular tachycardia.

The follow-up and characteristics of 20 patients with ventricular tachycardia (VT) and no detectable heart disease is reported. These were 16 men and four women with a mean age of 44 years. Symptoms were present in 18 patients (eight had syncope and ten palpitations or dizziness), VT was sustained in 11 patients and a left bundle branch block morphology with inferior axis was found in 17 patients. In three patients, VT had a right bundle branch block morphology and left-axis deviation. The VT was inducible in 13 patients during the electrophysiological testing (EP) and was sustained in five patients. Medical treatment was introduced in 19 patients. During a mean follow-up of 10 years from the onset of the symptoms and 6 years from the EP testing, one patient died suddenly. He had stopped taking amiodarone 5 months before. In seven patients symptoms recurred and were due to discontinuation of therapy in two cases and inefficacy of previous effective treatment in five patients. After modification of the treatment (three cases), implantation of a pacemaker (one case) and catheter ablation (one case), all patients became asymptomatic. Eleven patients became asymptomatic with the first administered antiarrhythmic therapy. One patient continues to be asymptomatic in spite of discontinuation of his medical therapy. We conclude that patients with VT and no detectable heart disease have a good long-term prognosis and that appropriate therapy can be found in almost all patients.

Adult↗
PubMed1990

Clinical experience with the Intertach 262-12 pulse generator in patients with recurrent supraventricular and ventricular tachycardia.

An antitachycardia pulse generator, the Intermedics Intertach 262-12 was implanted in 16 patients (14 patients with supraventricular tachycardia of various origins and two patients with recurrent ventricular tachycardia), who were not responsive to various antiarrhythmic drug regimens. The follow-up was from 6-49 months (mean 30.9 +/- 13.8). Five patients had a follow-up of over 3 years. The device was used in all patients. One patient with ventricular tachycardia died from a nonarrhythmic cause. Loss of responsiveness to burst pacing was observed in 1/14 patients with supraventricular tachycardia and nontolerance of antitachycardia pacing in one patient. Overall clinical success of pacing was observed in 13/16 patients = 81%. The pacemaker proved to be a versatile system with reliable tachycardia detection and termination functions.

Adult↗
PubMed1988

Effect of intravenous and oral calcium antagonists (diltiazem and verapamil) on sustenance of atrial fibrillation.

Both verapamil and diltiazem are used to control ventricular response during atrial fibrillation (AF). Their effect on the maintenance of AF is not known. The effects of the intravenous and oral administration of verapamil and diltiazem were investigated in 35 patients, 18 with (group I) and 17 without (group II) documented paroxysmal AF. Programmed electrical stimulation, either extra-stimuli or burst atrial pacing, was used to induce AF. In group I, the mean values of the duration of AF before and after the intravenous and oral administration of the calcium antagonists were 31 +/- 12, 112 +/- 49 and 69 +/- 25 minutes, respectively. For group II, the values were 5 +/- 3.4, 39 +/- 13 and 14 +/- 7 minutes, respectively. The differences were statistically highly significant (p less than 0.001), after both oral and intravenous administration compared with the baseline value in both groups. The data suggest that both intravenously and orally administered calcium antagonists enhance sustenance of electrically induced AF, especially in patients with spontaneous arrhythmia. Thus, in patients with paroxysmal AF, verapamil or diltiazem should be administered cautiously, because these drugs may prolong the duration of arrhythmia. Further studies are warranted to investigate the role of calcium antagonists in spontaneously occurring paroxysmal AF.

Administration, Oral↗
PubMed1988

[Replacement of the aortic valve with a bioprosthesis: 5-year surgical results].

To evaluate the clinical course after replacement of the aortic valve with a porcine heart-valve, 87 patients (mean age 52 years [5-70] at time of surgery) were followed up for a five-year period. Operative mortality was 1% and late mortality 8%. The actuarial probability of survival at five years for all patients was 91%. Embolic events occurred in two patients and endocarditis in six. Valve dysfunctions requiring reoperation resulted from bacterial endocarditis in three patients, from primary valve dysfunction in three patients and from paravalvular leak in another three patients. Echocardiographic cross examination of the bioprostheses showed degenerative processes in eight asymptomatic patients. Patients who underwent reoperation or showed valve degeneration were significantly younger (41 +/- 19 years and 42 +/- 9 years respectively) than patients without valve degeneration (52 +/- 9 years) [p less than 0.05]. We conclude that there is an increased risk of primary valve degeneration for patients under age 35. Echo-Doppler sonographic cross examinations of the heart are a highly sensitive means of detecting early degeneration of the bioprostheses.

Actuarial Analysis↗