Search PubMed⌕ Search

Biomedical subjects

B B Lerman

Publications and source records attributed to B B Lerman.

At least 91 records · Page 5Linked to original sources
PubMed1989

Stability of electrophysiological parameters after acute amiodarone loading: implications for patient management.

The appropriate timing of electrophysiological study in patients treated with amiodarone is uncertain. Twenty patients with coronary artery disease in whom sustained ventricular tachycardia was still inducible after 9 +/- 1 days of amiodarone loading (1,200-1,400 mg/day) underwent repeat electrophysiological testing after an additional month of maintenance therapy (400 mg/day). Compared with baseline, both short- and long-term amiodarone therapy caused significant changes in QTc, right ventricular effective refractory period, and ventricular tachycardia cycle length. However, there was no significant change in electrophysiological parameters between the end of the acute amiodarone loading period and 1 month of additional therapy. Sustained ventricular tachycardia remained inducible in 19 of 20 patients after 1 month of maintenance therapy. Amiodarone and desethylamiodarone plasma concentrations remained stable after amiodarone loading, but did not correlate with the magnitude of electrophysiological changes from baseline. These data suggest that electrophysiological testing after 9 days of high dose amiodarone therapy may accurately reflect long-term electrophysiological effects.

Aged↗
PubMed1989

Electrophysiologic effects of dipyridamole on atrioventricular nodal conduction and supraventricular tachycardia. Role of endogenous adenosine.

Exogenous adenosine has been shown to have potent electrophysiologic effects and antiarrhythmic properties within the atrioventricular (AV) node. Endogenous adenosine, a nucleoside with an increased release signaled by ischemia and hypoxia, is not believed to exert significant effects during homeostatic conditions. Recent experimental evidence suggests, however, that under normoxic conditions, the amount of adenosine released may be sufficient to mediate some of its physiologic effects. This study was designed to test the hypothesis that in humans the electrophysiologic effects of endogenously released adenosine on AV nodal conduction can be demonstrated under normoxic conditions by inhibiting uptake and degradation of the nucleoside. In the first protocol, the effects of intravenous dipyridamole (0.56 mg/kg bolus i.v., 5 micrograms/kg/minute infusion), a nucleoside-transport blocker that elevates endogenous plasma levels of adenosine, on AV nodal conduction were evaluated in seven patients. At a constant atrial paced cycle length, dipyridamole increased the AH interval from 110 +/- 19 to 164 +/- 26 msec, p = 0.002 (+/- SEM). Aminophylline (5.6 mg/kg i.v.), a competitive antagonist of adenosine, completely reversed the effects of dipyridamole on AV nodal conduction. Similarly, dipyridamole increased the cycle length at which pacing-induced AV nodal Wenckebach occurred, from 348 +/- 31 (control) to 388 +/- 33 msec (dipyridamole) (p = 0.002). In a second protocol, the effects of intravenous dipyridamole were evaluated in another group of six patients who had supraventricular tachycardia (SVT) in which the AV node was part of the reentrant circuit.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1988

Usefulness of adenosine for arrhythmias in infants and children.

Adenosine was administered to 25 infants and children (11 patients after presenting with a sustained arrhythmia, and 14 during a diagnostic electrophysiologic study) to determine its electrophysiologic effects. Adenosine was given as an intravenous bolus (starting dose 37.5 micrograms/kg, and increased by 37.5 micrograms/kg increments until an effect was seen). Adenosine caused tachycardia termination or transient increased atrioventricular (AV) block in all 25 patients. Seven patients had tachycardia requiring only the atria for perpetuation and developed increased AV nodal block (minimum effective adenosine dose range 37.5 to 350 micrograms/kg, mean 131). Thirteen had AV reciprocating tachycardia or AV node reentry tachycardia (minimum effective adenosine dose range 37.5 to 225 micrograms/kg, mean 114). Four other patients received adenosine to rule out preexcitation (minimum effective adenosine dose range 37.5 to 375 micrograms/kg, mean 165). One of the 25 patients had junctional ectopic tachycardia and adenosine administration caused retrograde AV block. Six of the 25 (24%) had noticeable but minor side effects. One patient had sustained bradycardia (2 to 3 minutes requiring temporary pacing). Adenosine is a safe and effective agent in the evaluation and treatment of infants and children with arrhythmias.

Adenosine↗
PubMed1988

Current-based versus energy-based ventricular defibrillation: a prospective study.

Defibrillation is thought to be mediated by a depolarizing current; however, the present method of defibrillation is based on delivering an empiric dose of energy to all patients. The hypothesis of this study was that for equivalent efficacy rates, a current-based defibrillation method would result in delivering less energy and peak current than would the standard energy-based method. In a group of 86 consecutive patients with ventricular fibrillation, every other patient was prospectively assigned to receive shocks according to method 1 or method 2. Method 1 was current based and delivered successive shocks of 25, 25 and a maximum of 40 A; method 2 was energy based and delivered shocks of 200, 200 and 360 joules. Patients in both groups were similar with respect to age, gender, weight, cardiac diagnosis, ejection fraction, antiarrhythmic therapy, chest circumference, chest depth and transthoracic impedance. Each method had statistically equivalent first shock (79% current-based versus 81% energy-based) and cumulative shock success rates. The mean first shock energy was 120 +/- 30 joules for patients receiving the current-based method and 200 joules for patients receiving energy-based shocks (p = 0.0001). The mean peak current was 24 +/- 2.3 and 33 +/- 5.0 A, respectively (p = 0.0001). Therefore, for equivalent first shock success rates, the energy-based method delivered 67% more energy and 38% more current than the current-based method. High transthoracic impedance (greater than or equal to 90 omega) predicted first shock failure only in patients undergoing defibrillation by the energy-based method (p = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Electrophysiological evaluation of sustained ventricular tachyarrhythmias in idiopathic dilated cardiomyopathy.

Sustained ventricular tachyarrhythmias and sudden death are particularly prevalent in patients with idiopathic dilated cardiomyopathy (IDC). In contrast to patients with ischemic heart disease, the value of electrophysiological stimulation (EPS) in patients with IDC has not yet been established. To clarify the role of EPS in these patients, we studied 19 patients (58 +/- 11 years) with IDC who had symptomatic ventricular tachycardia (VT) or ventricular fibrillation (VF). The mean left ventricular ejection fraction was 26 +/- 9%. Ten patients had survived out-of-hospital cardiac arrest, eight had documented sustained monomorphic VT and one patient had non-sustained VT associated with syncope. Thirteen of the 19 patients (68%) had their clinical ventricular tachyarrhythmias induced at EPS (12 VT, 1 VF). In nine of 13 patients (69%), the arrhythmias were subsequently suppressed during serial electrophysiological drug testing. During 17 +/- 11 months of follow-up, 10/19 (53%) patients experienced recurrence of their arrhythmias and nine out of 19 (47%) patients died; six died suddenly and three secondary to heart failure. There was no difference in arrhythmia recurrence between patients with and without inducible ventricular tachyarrhythmias at initial study. Furthermore, suppression of arrhythmia during serial testing did not predict outcome; recurrences were observed in five out of nine patients whose arrhythmias were suppressed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Surgical ablation of ventricular tachycardia with sequential map-guided subendocardial resection: electrophysiologic assessment and long-term follow-up.

A new operative technique of sequential map-guided subendocardial resection (SER) was used in 45 consecutive patients for the treatment of sustained ventricular tachycardia due to coronary artery disease. This technique is characterized by map-guided SER or cryothermic ablation during normothermic cardiopulmonary bypass, followed by repeated sequences of programmed stimulation to assess adequacy of resection. The patients' mean age was 59 +/- 10 years and the mean left ventricular ejection fraction was 34 +/- 12%. Twenty-five (56%) patients had a history of myocardial infarction within the previous 2 months. After ventriculotomy, 34 patients (76%) had inducible monomorphic ventricular tachycardia. These patients underwent repeated sequences of ventricular tachycardia induction and mapping during normothermic bypass followed by successive SER or cryothermic ablation until sustained monomorphic ventricular tachycardia was no longer inducible. Twenty-seven patients had a total of 60 discrete, mappable tachycardias induced and seven patients had 10 discrete tachycardias that were too fast to accurately map. In the remaining 11 patients, no ventricular tachycardia was inducible after ventriculotomy and SER, which included all visually identifiable scar, was performed. The mean cardiopulmonary bypass time was 102 +/- 27 min. Forty-one of 45 patients (91%) survived to hospital discharge, and 35 of 41 patients (85%) had no inducible ventricular tachycardia at postoperative electrophysiologic evaluation performed in the absence of all antiarrhythmic drugs. The remaining six patients had no inducible ventricular tachycardia with drug therapy. All four operative nonsurvivors had refractory cardiac collapse preoperatively. Over 19 +/- 12 months of follow-up, there were four sudden cardiac deaths and no nonfatal recurrences of ventricular tachycardia. There were seven additional cardiac deaths. Actuarial cardiac survival was 0.57, and freedom from arrhythmic events was 0.76 at 42 months. Thus, in the absence of cardiogenic shock, the technique of sequential map-guided SER achieves: (1) a high operative survival with acceptable perfusion times, (2) excellent long-term arrhythmia control, and (3) survival comparable to that in patients with similar left ventricular function and no history of ventricular tachyarrhythmia.

Aged↗
PubMed1988

Antiadrenergic effects of adenosine on His-Purkinje automaticity. Evidence for accentuated antagonism.

The effects of adenosine on the human His-Purkinje system (HPS) were studied in nine patients with complete atrioventricular (AV) block. Adenosine had minimal effect on the control HPS cycle length, but in the presence of isoproterenol increased it from 906 +/- 183 to 1,449 +/- 350 ms, P less than 0.001. Aminophylline, a competitive adenosine antagonist, completely abolished this antiadrenergic effect of adenosine. In isolated guinea pig hearts with surgically induced AV block, isoproterenol decreased the HPS rate by 36%, whereas in the presence of 1,3-dipropyl-8-phenyl-xanthine, a potent adenosine antagonist, the HPS rate decreased by 48% and was associated with an increased release of adenosine. Therefore, by blocking the effects of adenosine at the receptor level, the physiologic negative feedback mechanism by which adenosine antagonizes the effects of catecholamines was uncoupled. The results of this study indicate that adenosine's effects on the human HPS are primarily antiadrenergic and are thus consistent with the concept of accentuated antagonism. These effects of adenosine may serve as a counterregulatory metabolic response that improves the O2 supply-demand ratio perturbed by enhanced sympathetic tone. Some catecholamine-mediated ventricular arrhythmias that occur during ischemia or enhanced adrenergic stress may be due to an imbalance in this negative feedback system.

Adenosine↗
PubMed1987

Relation between amiodarone and desethylamiodarone plasma concentrations and electrophysiologic effects, efficacy and toxicity.

Because the value of monitoring amiodarone plasma concentrations remains undefined, this study was performed to evaluate its role during the management of patients receiving amiodarone. The early electrophysiologic effects of amiodarone were assessed in 40 consecutive patients with coronary artery disease and sustained ventricular tachycardia or fibrillation who underwent electrophysiologic studies and measurement of amiodarone plasma concentration before and 29 +/- 15 (mean +/- SD) days after initiation of therapy. Amiodarone and desethylamiodarone plasma levels did not correlate with changes in either sinus cycle length, QTc interval, ventricular effective refractory period, AH and HV intervals or ventricular tachycardia cycle length. Amiodarone and desethylamiodarone plasma concentrations and the effects of the drug on conduction intervals or right ventricular effective refractory periods were not related to suppression of arrhythmia induction by ventricular stimulation after 1 month of therapy. The relation between amiodarone plasma concentrations and both toxicity and efficacy during long-term therapy were prospectively assessed in a larger series of 114 consecutive patients with either symptomatic supraventricular or ventricular arrhythmias who were followed up on long-term amiodarone therapy for 26 +/- 15 months. Sixty-three patients (55%) had one or more adverse effects attributed to amiodarone. By life-table analysis, 40, 69 and 80% of patients had experienced an adverse reaction after 1, 2 and 3 years of therapy, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Differential electrophysiologic properties of decremental retrograde pathways in long RP' tachycardia.

Long RP' supraventricular tachycardias (SVT) often demonstrate both slow and decremental conduction properties in the retrograde pathway of the reentrant circuit. The electrophysiologic properties of these pathways are poorly understood. We studied 10 patients with long RP' SVT (RP'/RR, 0.52 to 0.71); five had the unusual form of atrioventricular nodal reentry (fast-slow) and five patients had accessory AV pathways with slow, decremental retrograde conduction properties. During SVT, the effects of intravenous adenosine (37.5 to 150 micrograms/kg), which increases potassium current (iK) in supraventricular tissue and hyperpolarizes membrane potential toward Ek (-90 mV), and the response to slow-inward channel blockade with verapamil (0.10 to 0.20 mg/kg iv) were evaluated. Adenosine and verapamil has similar effects in the presence of fast-slow AV nodal reentry since both agents terminated SVT by producing block in the retrograde slow AV nodal pathway. In contrast, adenosine and verapamil had differential effects on retrograde conduction in decremental accessory pathways. Adenosine terminated all episodes of SVT in the retrograde decremental pathway, whereas verapamil had a direct effect on this tissue in only two of five patients. Decremental retrograde accessory pathways can therefore demonstrate at least two types of electrophysiologic responses. Pathways that respond only to adenosine-induced hyperpolarizing K+ current likely comprise depressed fast-Na+ channel tissue, i.e., partially depolarized (greater than -60 to -70 mV) atrial tissue. In contrast, decremental accessory pathways that respond to both modulation of the slow-inward calcium current and K+ conductance have pharmacologic properties similar to those of the AV node and may represent more completely depolarized atrial fibers with resting membrane potentials of -60 mV or less.

Adenosine↗
PubMed1987

Predictors of efficacy of amiodarone and characteristics of recurrence of arrhythmia in patients with sustained ventricular tachycardia and coronary artery disease.

The value of serial electropharmacologic testing during long-term oral amiodarone therapy for prediction of long-term drug efficacy as well as characteristics of arrhythmia recurrence is controversial. One-hundred four consecutive patients with coronary artery disease and sustained ventricular tachyarrhythmias (VT) underwent initial electrophysiologic (EP) evaluation in the drug-free state and again after an amiodarone loading period of 25 +/- 14 days (mean +/- SD). Twenty-six patients (25%) had no inducible ventricular tachyarrhythmia during therapy with amiodarone (VT control group), whereas arrhythmia inducibility persisted in the remaining 78 patients (VT noncontrol group). During 17.4 +/- 13.7 months of follow-up, two patients in the VT control group either had VT recurrence or died suddenly compared with 21 VT recurrences and eight sudden cardiac deaths in the VT noncontrol group (actuarial event rates at 36 months of 0.11 and 0.56, respectively, p = .0065). The cycle lengths of recurrent VT in these 21 patients in the VT noncontrol group were compared with those observed at final EP testing. A significant linear correlation was demonstrated (r = .76, p = .0001). Subgroup analysis of patients in the VT noncontrol group showed no EP predictors of outcome, including cycle length of induced VT. However, patients dying suddenly during the follow-up period had a higher prevalence of new or worsening congestive heart failure (75%) compared with patients with VT recurrence (19%) or those with no arrhythmic event (29%) (p less than .02).2off

Aged↗
PubMed1987

Relationship between canine transthoracic impedance and defibrillation threshold. Evidence for current-based defibrillation.

The electrical parameter used to define defibrillation strength is energy. Peak current, however, may more accurately reflect the field quantities (i.e., electric field strength and current density) that mediate defibrillation and therefore should be a better clinical descriptor of threshold than energy. Though transthoracic impedance is a major determinant of energy-based threshold and is sensitive to operator-dependent changes in impedance (electrode-subject interface), an ideal threshold descriptor should be invariant with respect to these changes in impedance. We therefore compared the relative invariance of energy- and current-based thresholds when transthoracic impedance was altered by one of two methods: (a) change in electrode size (protocol A) or (b) change in electrode force (protocol B). In protocol A, impedance was altered in each dog by a mean of 95%. Energy thresholds determined at both low and high impedance were 44 +/- 21 J (mean +/- SD) and 105 +/- 35 J, respectively, P less than 0.0001. In contrast, peak current (A) thresholds were independent of transthoracic impedance, 22 +/- 5 A (low impedance) vs. 24 +/- 6 A (high impedance), P = NS. Energy and current thresholds showed a similar relationship for animals tested in protocol B. Therefore, current-based thresholds, in contrast to energy thresholds are independent of operator-dependent variables of transthoracic impedance and are invariant for a given animal. These results suggest that redefining defibrillation threshold in terms of peak current rather than energy provides a superior method of defibrillation.

Animals↗
PubMed1987

Sequential endocardial resection for the surgical treatment of refractory ventricular tachycardia.

The optimal surgical therapy for refractory ventricular tachycardia is controversial. The usual operation involves induction of tachycardia and endocardial mapping during normothermic cardiopulmonary bypass, followed by systemic hypothermia, aortic cross-clamping, and resection of the identified site of origin of the tachycardia. Our initial experience with this technique in 20 patients (mean age 60 years, mean ejection fraction 29%, mean number of failed antiarrhythmic drugs three) resulted in five (25%) surgical deaths, three caused by ventricular tachycardia and two by respiratory or heart failure. Electrophysiologic study showed that 11 of 15 survivors were free from ventricular tachycardia after operation, for a success rate in the survivors of 73%. Most failures occurred in patients with multiple tachycardia morphologies that were not eradicated by initial resection. Thereafter, the technique of sequential endocardial resection was used. After completion of endocardial mapping, directed normothermic endocardial resection is performed; more attempts to induce ventricular tachycardia are made and followed by further mapping and resection until tachycardia can no longer be induced. Fifty patients (mean age 59 years, mean ejection fraction 33%, mean number of failed antiarrhythmic drugs three) were treated by this method, with a mean of two resections per patient (range one to six). Mean perfusion time in the sequential resection group (101 +/- 28 minutes) was not significantly different from that of the earlier patients (101 +/- 40 minutes). There were four (8%) surgical deaths, one caused by persistent arrhythmia and three caused by respiratory or heart failure. Electrophysiologic study after operation showed that 40 of 46 survivors (87%) were free of ventricular tachycardia. Symptoms in the six with inducible tachycardia on postoperative electrophysiologic study were well controlled with medication. These data suggest that sequential endocardial resection guided by intraoperative mapping is a highly effective operative approach for patients with ventricular tachycardia.

Cardiac Pacing, Artificial↗
PubMed1986

Atrial pacing for conversion of atrial flutter.

Fifty-seven episodes of atrial flutter in 46 consecutive medically treated patients (aged 60 +/- 17 years) were treated by rapid atrial pacing. Thirty-three patients (72%) had structural heart disease. Most pacing trials were conducted in patients receiving digoxin (88%) and antiarrhythmic drugs (77%). In 51 of 57 trials (89%), patients were successfully converted to normal sinus rhythm. Multivariate analysis revealed that patients who had congestive heart failure and who were older were more likely to be refractory to pacing. Left atrial size did not influence outcome. Confirmation of local atrial capture with a bipolar atrial electrogram and use of multiple atrial pacing sites enhanced the success rate. Eight patients (17%) demonstrated sinus node suppression after atrial pacing; sinus node disease was previously unsuspected in 4 of these patients. These bradyarrhythmias were easily managed because a pacing catheter was already in place. The only significant complication was femoral vein thrombosis in 1 patient. It is concluded that atrial pacing is an effective, safe and convenient method for the elective conversion of atrial flutter in the general population of medically treated patients. This technique is an attractive alternative to transthoracic cardioversion, and may be preferable in many patients.

Adult↗
PubMed1986

De novo refractory ventricular tachyarrhythmias after coronary revascularization.

Twelve of 1,675 patients who underwent coronary artery bypass grafting during a 2.5-year period had new onset, recurrent, sustained ventricular tachyarrhythmia a mean of 27 days (range 2 to 150) postoperatively. No patient had an intra- or perioperative myocardial infarction and all patients were hemodynamically stable and had normal metabolic and electrolytic indexes at the time of ventricular tachyarrhythmia. Preoperative ejection fraction was 39 +/- 10% (mean +/- standard deviation) and all patients had Lown grade II or less ventricular ectopic activity on ambulatory monitoring. Postoperative angiography demonstrated occluded saphenous vein grafts in 3 of 7 patients studied, none of whom had symptoms suggestive of myocardial ischemia. Treatment with conventional antiarrhythmic therapy was unsuccessful in all but 1 patient, and 10 patients were treated with amiodarone and 1 patient with propafenone. Four of these patients also received an automatic implantable defibrillator. Thus, de novo ventricular tachyarrhythmia can occur unexpectedly after coronary artery bypass grafting and may be the result of several factors related to either subclinical graft occlusion or increased dispersion of repolarization secondary to reperfusion.

Aged↗
PubMed1986

Mechanism of atropine-resistant atrioventricular block during inferior myocardial infarction: possible role of adenosine.

Mechanisms responsible for atrioventricular (AV) block during acute inferior myocardial infarction are only partially understood. Increased parasympathetic tone is the factor usually postulated; however, persistence of AV block after atropine administration is frequently observed. Adenosine, an endogenous ischemic metabolite, has well established depressant effects on AV node conduction. In this report, an episode of atropine-resistant AV block was reversed by aminophylline, a competitive adenosine antagonist, in a patient with an acute inferior myocardial infarction. This observation suggests a role for adenosine in the mediation of ischemia-induced AV node block.

Adenosine↗
PubMed1986

Resection of scarred papillary muscles improves outcome after surgery for ventricular tachycardia.

Papillary muscle scarring is encountered frequently during operations for sustained ventricular tachycardia (VT). Indications for excision of the papillary muscle scar and mitral valve replacement (MVR) are controversial. The findings in 46 consecutive patients undergoing operative electrophysiologic map-directed endocardial resections for VT were reviewed. There was papillary muscle scarring in 15 patients (average age: 59 years; sex: 11 male, 4 female; average ejection fraction: 31 +/- 14%). Eleven patients had a VT with the site of origin on a scarred papillary muscle; four had another VT site of origin. Six patients underwent papillary muscle scar resection (5 with MVR); six underwent papillary muscle cryotherapy (-60 C X 2 min); and three had neither papillary muscle resection nor MVR. All six patients with papillary muscle resection +/- MVR are alive and free of arrhythmia after 14.3 +/- 7.6 months of follow-up. Five of six patients treated by papillary muscle cryotherapy alone manifested spontaneous (4 patients) or inducible (1 patient) VT during early postoperative evaluation. Two of the three patients with untreated papillary muscle scarring developed late complications requiring reoperation. One patient developed mitral regurgitation requiring MVR 5 months later. The other developed a previously undocumented VT 2 years after operation. Significant papillary muscle scarring visualized at the time of operation for arrhythmia is an indication for resection of the scar and the papillary muscle, even if this necessitates MVR. In this series, attempts to preserve the papillary muscle, by incomplete resection of the scar or by cryotherapy, resulted in a high failure rate owing to recurrent VT or mitral regurgitation.

Aged↗
PubMed1986

Repetitive supraventricular tachycardia: clinical manifestations and response to therapy with amiodarone.

Repetitive supraventricular tachycardia is an uncommon arrhythmia which usually occurs in patients free of structural heart disease. It is characterized by incessant short salvos of supraventricular tachycardia separated by only one or two normal sinus beats. Therapy with conventional antiarrhythmic drugs is usually ineffective. This report describes three patients with repetitive supraventricular tachycardia in whom evidence for associated sinus node dysfunction was observed. Amiodarone therapy, with ventricular pacing in two patients, has provided effective control of this arrhythmia in all three patients.

Adult↗