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Biomedical subjects

L N Horowitz

Publications and source records attributed to L N Horowitz.

At least 37 records · Page 2Linked to original sources
PubMed1988

Relation of acute antiarrhythmic drug efficacy to left ventricular function in coronary artery disease.

This study assessed the relation between acute antiarrhythmic drug efficacy and left ventricular (LV) function in patients with sustained ventricular tachyarrhythmias, that is, sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Electrophysiologic studies (n = 560) were performed in 201 patients, separated for analysis into less than 30 and greater than or equal to 30% ejection fraction groups. Coronary artery disease was present in all patients. The 8 acute antiarrhythmic regimens were procainamide, quinidine, mexiletine, mexiletine + type 1A agent, flecainide or indecainide, amiodarone, amiodarone + type 1A and "miscellaneous" agents. At least 1 successful acute antiarrhythmic regimen was found in 47% of patients and in a significantly greater proportion of patients with ejection fraction greater than or equal to 30% (52 of 81 = 64%) than in those with ejection fraction less than 30% (43 of 120 = 36%, p less than 0.001). Drug trials were successful (initiation of less than 15 repetitive ventricular responses) in 32% of patients with ejection fraction greater than or equal to 30% versus 19% of those with ejection fraction less than 30% (p less than 0.001). There were no statistically significant differences between the 2 ejection fraction groups in type of heart disease, acute antiarrhythmic dosages or mean serum drug levels. A logistic regression analysis incorporating multiple clinically relevant factors found that ejection fraction was the only factor that correlated significantly with drug success or failure (p less than 0.002). Acute antiarrhythmic drug efficacy relates to LV function per se or to other pathophysiologic mechanisms of which ejection fraction may be a marker.

Administration, Oral↗
PubMed1988

Inducible atrial flutter after the Mustard repair of complete transposition of the great arteries.

Atrial flutter is a common postoperative arrhythmia in patients with complete transposition of the great arteries (d-TGA) after the Mustard repair. Sixty patients with d-TGA who had the Mustard repair were evaluated by electrophysiologic studies. Thirty-three (55%) had inducible sustained atrial flutter; 17 of them developed spontaneous clinical episodes of atrial flutter (clinical atrial flutter group) and 16 did not (nonclinical atrial flutter group). In 6 of the 17 patients (35%) with clinical inducible atrial flutter, the condition was first documented in the electrophysiologic laboratory with subsequent development of spontaneous clinical episodes. Catheter endocardial mapping, used to determine atrial activation sequences and and conduction intervals, revealed intraatrial conduction delays with late activation of the low atrial sites in all patients. Abnormalities of atrial refractoriness were present, with a greater dispersion of atrial refractoriness found in the clinical atrial flutter group. Severe abnormalities of sinus nodal function appeared to a significantly greater degree among patients who had clinical episodes of atrial flutter. These electrophysiologic abnormalities and associated arrhythmias may predispose patients with d-TGA to sudden death.

Atrial Flutter↗
PubMed1988

Proarrhythmic effects of antiarrhythmic drugs in patients with malignant ventricular arrhythmias evaluated by electrophysiologic testing.

The provocation or worsening of arrhythmias by antiarrhythmic regimens was evaluated in patients with malignant ventricular arrhythmias undergoing electrophysiologic studies. In 314 patients with sustained or nonsustained ventricular tachycardia or ventricular fibrillation, 801 drug studies were performed using a standard protocol of programmed electrical stimulation. The criteria for proarrhythmia were: 1) initiation of sustained ventricular tachyarrhythmia in a patient in whom only nonsustained tachycardia was induced at baseline; 2) conversion of a sustained tachycardia that could be terminated by programmed electrical stimulation at baseline to one that required cardioversion for termination during drug therapy; 3) initiation of a sustained tachyarrhythmia by a less aggressive mode of stimulation than was required at baseline; and 4) development of spontaneous or incessant ventricular tachycardia. Proarrhythmia criterion 1 occurred during 20 (18%) of 118 studies and at least once in 15 (28%) of 54 patients. Criterion 2 was met during 39 (7%) of 578 studies and at least once in 29 (13%) of 220 patients. Criterion 3 was achieved during 135 (20%) of 687 studies in patients with sustained ventricular tachyarrhythmias at baseline. Criterion 4 occurred during 9 (1%) of 801 drug studies. In 40 patients in whom well tolerated ventricular tachycardia was initiated with fewer extrastimuli during drug study than at baseline, the drug was continued and the patients were followed up. The recurrence rate of tachycardia was the same in these patients as in 73 patients followed up on regimens on which the number of extrastimuli required for initiation was not reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Drug therapy for survivors of sudden cardiac death.

The proliferation of standard as well as novel community based systems for resuscitation of victims of out-of-hospital cardiac arrest has provided a large group of sudden cardiac death survivors who present a therapeutic challenge. The nature and severity of the underlying heart disease must be delineated. Particularly, myocardial ischemia and congestive heart failure must be controlled. Prior to considering device therapy of surgical intervention, pharmacologic therapy should be evaluated. Baseline electrophysiological studies determine the applicability of serial pharmacologic testing. In patients with inducible VT/VF, serial electrophysiological testing can identify drug regimens that prevent the arrhythmia in approximately 40% of patients. In an additional 20% of patients, regimens which slow the ventricular tachycardia and significantly reduce the arrhythmia related mortality can be identified. Three to 5-year follow-up has shown such an approach can reduce the sudden death mortality in these patients to less than 3% per year. It has been suggested that certain medication, most notably amiodarone, electrophysiological testing has not been useful in assessing efficacy. Several recent studies, however, have shown that electrophysiological testing is indeed useful even in evaluating the efficacy of amiodarone. In patients in whom ventricular tachycardia/ventricular fibrillation cannot be prevented or significantly slowed, medical therapy is generally ineffective and the sudden death mortality is 20% to 40% per year. In such patients, other therapeutic modalities should be considered.

Anti-Arrhythmia Agents↗
PubMed1988

New antiarrhythmic drugs.

While controversy still exists as to the precise indications for the treatment of all forms of ventricular arrhythmia, advances in the number and, more importantly, type of antiarrhythmic drugs can provide the clinician with a rational basis for selecting antiarrhythmic drug therapy. A host of new agents with different pharmacokinetic and electrophysiological actions are now available, and can be compared or contrasted to conventional antiarrhythmic agents such as quinidine, procainamide, disopyramide, lignocaine (lidocaine) and bretylium. This review summarises the electrophysiological, haemodynamic, pharmacokinetic, and efficacy and safety data of mexiletine, tocainide, flecainide, encainide, propafenone, amiodarone, sotalol, pirmenol, cibenzoline (cifenline) and ethmozine (moracizine, moricizine), and aims to provide a basis on which clinicians can compare and contrast these agents and form an algorithm for selection of antiarrhythmic drug therapy in the treatment of patients with ventricular arrhythmias.

Anti-Arrhythmia Agents↗
PubMed1988

The electrophysiologic properties of esmolol, a short acting beta-blocker.

Although beta-blockers have established efficacy in treating ventricular ectopy and PSVT, their applicability for acute antiarrhythmic interventions in patients with organic heart disease or COPD, is frequently limited by negative inotropic or bronchospastic side effects. The development of an ultrashort acting beta-blocker with rapid reversibility of its side effects would widen their applicability. Therefore, we tested the electrophysiologic properties of such a new short acting beta-blocker, esmolol, in 14 patients (10 with organic heart disease) with a mean EF of 47.6 +/- 17%, undergoing standard clinical electrophysiologic studies for various indications. Like most other beta-blockers, esmolol's major direct effects were on sinus node function and AV nodal conduction characteristics; significantly prolonging sinus cycle length, cycle length to Wenckebach and AH interval in sinus rhythm and at a paced cycle length of 600 ms. In contrast to most other beta-blockers, following termination of its infusion, esmolol shortened parameters of sinus node function and AV nodal refractoriness, with respect to the control values, suggesting a possible rebound phenomena. These effects occurred within 5 min of terminating the intravenous drug infusion. Esmolol had no significant effect on systolic blood pressure, electrocardiographic intervals and had rare adverse reactions. We conclude that esmolol is an ultra-short acting beta-blocker, with typical direct electrophysiologic effects on sinus node and AV nodal function, and a possible rebound phenomena following its discontinuation that may make it particularly suited to acute antiarrhythmic interventions in patients susceptible to adverse beta-blocker side effects.

Adrenergic beta-Antagonists↗
PubMed1987

Development of congestive heart failure and alterations in left ventricular function in patients with sustained ventricular tachyarrhythmias treated with amiodarone.

The interaction between the efficacy and tolerance of amiodarone and the degree of left ventricular (LV) dysfunction was assessed in 126 patients with sustained ventricular tachyarrhythmias. In all patients radionuclide angiographic LV ejection fraction (EF) was measured before and after 8 to 12 months of amiodarone therapy. At baseline mean EF was 25 +/- 13% and 86 patients had an EF of 30% or less. In patients receiving amiodarone at steady state, there was a small but significant increase in EF (23 to 26%, p less than 0.05). Congestive heart failure (CHF) was present in 43 patients before amiodarone therapy. In 16 patients new (9 patients) or worsened (7 patients) CHF developed during the first year of amiodarone therapy. Development of CHF was not consistently related to a change in EF or heart rate. The clinical efficacy and tolerance of amiodarone were affected by the baseline EF and development of CHF. Efficacy and tolerance was 80% in patients with an EF of more than 30% and 60% in those with an EF of 30% or less. Among the 16 patients in whom new or worsened CHF developed, 6 (38%) died and 9 (56%) had recurrent ventricular tachyarrhythmias. Both baseline EF and development of CHF during amiodarone treatment significantly affect the prognosis in patients with ventricular tachyarrhythmias.

Adult↗
PubMed1987

Determinants of hospital cost and length of stay for patients undergoing electrophysiologic testing.

To assess the effects of various clinical factors in determining the cost and length of stay in patients undergoing electrophysiologic testing for cardiac arrhythmias, the hospital cost and length of stay data were reviewed in 222 consecutive inpatients who underwent electrophysiologic testing from January 1 to December 31, 1984. Admissions were classified as: primarily for treatment of arrhythmias (171 patients); primarily for treatment of arrhythmias but with serious concurrent illnesses that prolonged hospitalization (43 patients); or primarily for nonarrhythmic problems with electrophysiologic study an incidental part of hospitalization (8 patients). Based on allowable length of stay for the applicable DRGs, actual hospitalizations exceeded Medicare allowable length of stay by 50 to 500%. Retrospective review of hospital charts indicated that 3 clinical factors serve as effective markers in determining length of stay: need for amiodarone, induction of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF), and presence of serious other medical problems that require stabilization before electrophysiologic testing. Our data indicate that 3 classes of patients can be identified: I. DRG A (45%)--those who did not have sustained VT or VF induced, did not require amiodarone and had no serious concurrent illnesses. The mean length of stay was 7.1 days. II. DRG B patients (21%)--those who had sustained VT or VF induced, but did not require amiodarone and had no serious concurrent illnesses. The mean length of stay was 13.7 days. III. DRG C patients (34%)--those who either had a serious concurrent illness or required amiodarone. The mean length of stay was 19.7 days. This classification schema might allow a more appropriate system for determining reimbursement.

Amiodarone↗
PubMed1987

Efficacy of oral and intravenous indecainide in ventricular arrhythmias.

To evaluate the efficacy of oral and intravenous indecainide, a new class IC antiarrhythmic agent, 3 separate protocols were performed in patients with benign or potentially lethal ventricular arrhythmias. An open-label intravenous trail in 10 patients was conducted using a dose of 1.7 mg/kg/min under constant monitoring. An oral short-term in-hospital trial in 20 patients (8 patients entered directly from the intravenous short-term trial) was conducted using a single-blind placebo dose titration protocol in which 50 mg of indecainide every 8 hours was increased at 3-day intervals to 75 mg, and then 100 mg every 8 hours depending on the observed change in ventricular arrhythmia frequency by Holter monitoring. Finally, an outpatient long-term oral trial was conducted in 17 of the 20 patients who completed the inpatient oral short-term trail. Two of the 10 patients from the inpatient intravenous trail did not enter the oral trial, because a proarrhythmic response developed in 1 and because of a lack of efficacy in the other. During the inpatient oral trial, 17 of 20 patients (85%) responded to indecainide and entered the long-term phase. Two of these patients were removed from the trial because of lack of efficacy at 3 and 10 months, respectively. In the oral therapy protocols, minor side effects of the central nervous system occurred in 4 of 17 patients (24%). Six of 20 patients (30%) each had more than a 25% increase in PR and QRS duration that was not associated with higher degrees of block.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1987

Proarrhythmic responses during electrophysiologic testing.

Antiarrhythmic drugs may worsen ventricular arrhythmias in certain patients. This effect, termed proarrhythmia, aggravation or provocation of arrhythmia, can be investigated with either noninvasive or invasive techniques. Using electrophysiologic study, 160 patients with ventricular tachycardia or ventricular fibrillation were evaluated during treatment with 432 different antiarrhythmic regimens. Proarrhythmic responses were noted in 68 drug trials (16%), and at least 1 event was observed in 51 patients (32%). Nonsustained ventricular tachycardia was converted to sustained ventricular tachycardia in 17% of these studies. Hemodynamically stable ventricular tachycardia was converted to an arrhythmia that required cardioversion for termination in 5% of the studies. Ventricular tachyrhythmia was more easily induced in 12% of trials. These proarrhythmic responses were not related to changes in QRS duration, QT interval or JT interval measured at baseline or to changes produced by antiarrhythmic drugs.

Anti-Arrhythmia Agents↗
PubMed1987

Electrophysiologic assessment of antiarrhythmic drug efficacy for ventricular tachyarrhythmias associated with dilated cardiomyopathy.

To determine the benefit of serial electrophysiologic drug testing in patients with ventricular tachyarrhythmias related to dilated cardiomyopathy, programmed ventricular stimulation was performed in 38 patients. In the baseline study, sustained ventricular tachycardia (VT) was induced in 18 patients, ventricular fibrillation in 7 and nonsustained VT in 13. The patients underwent a total of 84 trials of drug therapy (mean 2.3 +/- 1.4 trials/patient). Complete success (induction of fewer than 6 repetitive responses) was recorded in 19 trials and partial success (induction of at least 6 but no more than 15 repetitive responses) in 7. Potential proarrhythmic effects were observed in 9 trials. Overall, at least 1 successful regimen was identified for 20 patients (53%). During a mean follow-up of 21 +/- 13 months, there were no arrhythmia recurrences or episodes of sudden death among patients discharged with a drug regimen determined to be effective by serial drug testing. In comparison, among patients taking regimens that failed to prevent arrhythmia induction, there were 3 arrhythmia recurrences and 2 sudden deaths (p less than 0.05). Serial electrophysiologic drug testing provides an effective method of identifying successful medical therapy for patients with ventricular arrhythmia related to dilated cardiomyopathy.

Adult↗
PubMed1987

Influence of left ventricular dysfunction on flecainide therapy.

Seventy-six patients with ventricular tachyarrhythmias (40 sustained and 36 nonsustained) were treated with oral flecainide. Radionuclide left ventricular ejection fraction was 30% or less in 33 patients and greater than 30% in 43 patients. Before flecainide, compensated heart failure was present in 23 patients (ejection fraction less than or equal to 30% in 15 and greater than 30% in 8). Flecainide mean dose was 150 mg twice daily and mean plasma concentration was 720 ng/ml. New or worsened congestive heart failure occurred in seven patients on flecainide therapy, all with an ejection fraction of less than 30%; six had a previous history of compensated heart failure and of these, three died. Ejection fraction was the only independent variable that significantly influenced efficacy and tolerance of flecainide. After 1 year of therapy, efficacy and tolerance was 58% (25 of 43) in patients with an ejection fraction greater than 30% and 12% (4 of 33) in patients with an ejection fraction of 30% or less (p less than 0.001). Thus, congestive heart failure can occur during flecainide therapy, particularly in patients with a previous history of congestive heart failure and ejection fraction of less than 30%, and may particularly limit therapy in these patients. Clinical efficacy and tolerance were significantly lower in patients with an ejection fraction of less than 30%.

Adult↗
PubMed1987

Electrophysiologic consequences of the Mustard repair of d-transposition of the great arteries.

This study describes the electrophysiologic effects of the Mustard repair of d-transposition of the great arteries on the sinus node and on conduction and refractoriness in the atrium, atrioventricular (AV) node and ventricle. Seventy-two electrophysiologic studies were performed on 64 patients after the Mustard operation. Standard rest and 24 hour ambulatory electrocardiograms were evaluated. Catheter endocardial atrial mapping, available in 67 of the 72 studies, revealed that sinus rhythm was present in the atria in 33 patients, ectopic atrial rhythm in 26 and junctional rhythm in 8. Intraatrial conduction delays with very late activation of the low medial, low lateral or low right atrium at the AV junction were present in 53 of 59 patients with atrial or sinus rhythm. Sinus node function was normal in only nine patients. Prolonged refractory periods were found in the right atrial portion of the new right atrium when compared with the left atrial portion of the new right atrium. Forty-one percent of the patients had prolongation of atrial refractoriness with shortening of the paced cycle lengths. Fifty-one percent developed sustained intraatrial reentry with programmed atrial stimulation. Forty-eight percent of these patients with inducible atrial tachycardia have since developed clinical episodes of atrial flutter. In summary, electrophysiologic studies revealed significant abnormalities of sinus node function and atrial conduction and refractoriness. Alone or in combination, these abnormalities, which result in severe bradycardia or rapid atrial arrhythmias, may lead to sudden death. The Jatene or arterial switch procedure may provide an appropriate alternative operation in this group of patients.

Adolescent↗
PubMed1987

Reduction in sudden death and total mortality by antiarrhythmic therapy evaluated by electrophysiologic drug testing: criteria of efficacy in patients with sustained ventricular tachyarrhythmia.

Reports of the results of electrophysiologic testing of antiarrhythmic regimens have concentrated on inducibility of ventricular tachycardias during drug treatment. Many drug regimens, however, affect the tachycardia but fail to prevent its initiation. In this study, 258 patients who underwent serial electrophysiologic studies were followed up. The patients were divided into three groups on the basis of the results of electrophysiologic testing. Group 1 included patients in whom the initiation of ventricular tachycardia was prevented by the drug regimen. In groups 2 and 3 the ventricular tachycardia was still inducible with the discharge drug regimen. In group 2, the drug regimen demonstrated a beneficial response (that is, the tachycardia cycle length increased by greater than 100 ms and the tachycardia did not produce severe symptoms). In group 3, the regimen did not produce a beneficial response. During follow-up, recurrence of sustained ventricular tachycardia occurred in 7 (7%) of 103 group 1 patients but in 20 (39%) of 51 and 52 (50%) of 104 group 2 and 3 patients, respectively. However, the total mortality and sudden death mortality rates were substantially reduced in group 2 (12 and 4%, respectively) compared with group 3 (39 and 34%). In fact, the total mortality and sudden death mortality in groups 1 and 2 were not significantly different. Thus, under certain circumstances, a drug regimen that produces a beneficial response may be an acceptable clinical alternative, particularly when no regimen prevents induction of ventricular tachycardia.

Adolescent↗
PubMed1987

Risks and complications of clinical cardiac electrophysiologic studies: a prospective analysis of 1,000 consecutive patients.

The complications of clinical cardiac electrophysiologic studies were prospectively evaluated in 1,000 consecutive patients studied in one laboratory with an unaltered protocol to better assess the risks of this procedure. There were 728 men and the mean age of the entire group was 58 years (range 16 to 84). Coronary artery disease was the most common type of heart disease (56%) and 200 patients had no identifiable organic heart disease. The indication for study was a ventricular tachyarrhythmia or cardiac arrest in 582 patients. Each patient underwent an initial (baseline) study and 444 patients underwent serial drug studies (2.7/patient). There was one death during these studies. Other major complications included arterial injury (0.4%), thrombophlebitis (0.6%), systemic arterial embolism (0.1%), pulmonary embolism (0.3%) and cardiac perforation (0.2%). Significant arrhythmic complications included catheter-induced permanent complete atrioventricular (AV) block in 1 patient, nonclinical atrial fibrillation that required therapy in 10 patients and severe proarrhythmic events in 12 (3%) of 397 patients undergoing drug studies for ventricular tachyarrhythmias. Cardioversion was required for termination of ventricular tachyarrhythmias in 179 baseline studies (53% of patients with inducible arrhythmia), and in an additional 35 patients, cardioversion was required at least once during follow-up studies. Although clinical cardiac electrophysiologic studies are associated with complications, the risks are small and acceptable.

Arrhythmias, Cardiac↗