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Biomedical subjects

M E Josephson

Publications and source records attributed to M E Josephson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Assessment of permanent dual-chamber pacing as a treatment for drug-refractory symptomatic patients with obstructive hypertrophic cardiomyopathy. A randomized, double-blind, crossover study (M-PATHY).

BACKGROUND: Dual-chamber pacing (DDD) has been proposed as a treatment alternative to surgery for severely symptomatic patients with obstructive hypertrophic cardiomyopathy (HCM), based largely on uncontrolled studies. METHODS AND RESULTS: This prospective, multicenter trial assessed pacing in 48 symptomatic HCM patients with >/=50 mm Hg basal gradient, refractory to drug therapy. Patients were randomized to 3 months each of DDD pacing and pacing backup (AAI-30) in a double-blind, crossover study design, followed by an uncontrolled and unblinded 6-month pacing trial. With randomization, no significant differences were evident between pacing and no pacing for subjective or objective measures of symptoms or exercise capacity, including NYHA functional class, quality of life score, treadmill exercise time or peak oxygen consumption. After 6 additional months of unblinded pacing, functional class and quality of life score were improved compared with baseline (P<0.01), but peak oxygen consumption was unchanged. Outflow gradient decreased 40%, 82+/-32 mm Hg to 48+/-32 mm Hg (P<0. 001), and was reduced in 57% of patients but showed no change or an increase in 43%. At 12 months, 6 individual patients (12%) showed improved functional capacity; each was 65 to 75 years of age. Left ventricular wall thicknesses in the overall study group showed no remodeling between baseline (22+/-5 mm) and 12 months (21+/-5 mm; P=NS). CONCLUSIONS: (1) Pacing cannot be regarded as a primary treatment for obstructive HCM; (2) with randomization, perceived symptomatic improvement was most consistent with a substantial placebo effect; (3) longer, uncontrolled pacing periods were associated with some subjective benefit but unaccompanied by objective improvement in cardiovascular performance and should be interpreted cautiously; (4) modest reduction in outflow gradient was achieved in most patients; and (5) a small subset (12%) >/= 65 years of age showed a clinical response, suggesting that DDD pacing could be a therapeutic option for some elderly patients.

Adult↗
PubMed1999

Presence and significance of the left atrionodal connection during atrioventricular nodal reentrant tachycardia.

It has been suggested that the anatomic substrates of dual atrioventricular nodal pathways are likely to be the atrionodal connections. During atrioventricular nodal re-entrant tachycardia (AVNRT) or ventricular pacing (VP), an earliest retrograde atrial activation in the coronary sinus (CS) distal to the ostium (CS breakthrough) would suggest the presence of an exit from a left atrionodal connection. The aim of the study was to evaluate the incidence of such an atrial retrograde activation in the CS during AVNRT and VP. The retrograde atrial activation was recorded during typical AVNRT (38 patients, 27 women, mean age 44 +/- 18 years) by a multipolar catheter in the CS, a decapolar catheter in the His bundle position, and a deflectable quadripolar catheter along the tricuspid annulus anterior to the CS ostium. In 31 patients the retrograde atrial activation was recorded also during VP at a similar cycle length. A CS breakthrough was found in 18 patients during AVNRT (47%) and in 13 patients during VP (42%). Presence or absence of CS breakthrough was concordant between AVNRT and VP in 90% of the patients. A CS breakthrough, suggesting a left-sided atrionodal connection, is frequently recorded both during AVNRT and VP. In patients with a CS breakthrough pattern, the absence of correlation between the His bundle to the earliest CS retrograde atrial electrogram interval and AVNRT cycle length, or any other atrial activation times recorded in the posterior and anterior region of the Koch's triangle, would suggest that the left-sided atrionodal connection is a bystander during typical AVNRT.

Adolescent↗
PubMed1999

The evolving role of ambulatory arrhythmia monitoring in general clinical practice.

PURPOSE: To evaluate the efficacy of various ambulatory electrocardiographic monitors for the diagnosis of arrhythmia-related disorders and to provide recommendations for their use in clinical practice. DATA SOURCES: Studies published since 1988 were identified through search of the MEDLINE database. STUDY SELECTION: Studies that met methodologic criteria for minimal bias and had clinical relevance were selected. DATA EXTRACTION: Descriptive and analytic data from each study. DATA SYNTHESIS: Ambulatory electrocardiographic monitors, specifically transtelephonic continuous-loop event recorders, are highly effective for establishing a diagnosis in patients with palpitations but are less effective for establishing a diagnosis in patients with syncope. Clinicians may use these devices to monitor for nonsustained ventricular tachycardia in patients at potentially high risk for sudden arrhythmic death; however, few data are available to support this practice. Ambulatory monitors are useful for assessment of the safety and efficacy of antiarrhythmic medications and the recurrence of symptomatic supraventricular arrhythmias. New ambulatory arrhythmia monitoring devices are being developed that may facilitate outpatient management of chronic cardiac disease. CONCLUSIONS: Ambulatory electrocardiographic monitors, particularly transtelephonic continuous-loop event recorders, aid in the diagnosis of symptomatic arrhythmias. These devices are also useful for monitoring the effectiveness and safety of antiarrhythmic medications. Guidelines are lacking for use of these devices to assess prognosis in patients at potential risk for sudden arrhythmic death.

Algorithms↗
PubMed1999

Entrainment/mapping criteria for the prediction of termination of ventricular tachycardia by single radiofrequency lesion in patients with coronary artery disease.

BACKGROUND: A variety of mapping criteria have been proposed to localize critical sites at which radiofrequency (RF) can predictably terminate reentrant ventricular tachycardia (VT) caused by coronary artery disease. The purpose of this study was to determine the accuracy of using a combination of 3 mapping criteria in predicting termination of VT by a single RF lesion. METHODS AND RESULTS: Fifteen consecutive patients with coronary artery disease and recurrent sustained VT underwent an attempted RF ablation of 20 monomorphic VTs. Successful termination of VT by a single RF lesion was predicted if all the following mapping criteria were met: (1) an exact QRS match in the 12-lead ECG during entrainment; (2) a return cycle length </=10 ms of the VT cycle length; (3) presystolic potentials (<70% of VT cycle length) with an activation time to the QRS within 10 ms of the stimulus to QRS. Inability to meet these 3 criteria was considered to predict failure of VT termination by RF energy at that site. RF ablation was applied to 44 left ventricular sites in 20 VTs at which at least 1 of the mapping criteria was met. VT was terminated with a single RF lesion in 19 of 19 sites meeting all criteria; RF failed to terminate VT at 24 of 25 sites at which all 3 criteria were not met (P<0.0005). CONCLUSIONS: To maximize success and minimize the number of RF lesions in patients with infarct-related VT, all the above 3 mapping criteria should be met before the application of RF energy.

Adult↗
PubMed1999

Relation of induced to spontaneous ventricular tachycardia from analysis of stored far-field implantable defibrillator electrograms.

Predischarge testing of implantable cardioverter-defibrillators is often used to tailor antitachycardia pacing algorithms based on the response of induced ventricular tachycardia (VT) to pacing. Despite this practice, little is known about the relation between VT induced at predischarge study and VT that occurs spontaneously. To clarify this relation, we identified 19 patients with VT induced at predischarge study and compared the characteristics of the induced VT with the first episode of spontaneous VT. VT morphology, tachycardia cycle length, and response to antitachycardia pacing were measured from far-field electrograms stored by the implantable cardioverter-defibrillator. All subjects had coronary artery disease and previous myocardial infarction. The mean time from baseline study until a spontaneous VT episode was 162+/-121 days. Analysis of far-field electrograms revealed that spontaneous VT was morphologically different from predischarge-induced VT in 13 of 19 cases (68%). The cycle length of induced VT was significantly shorter than spontaneous VT when VT morphologies were different but not when spontaneous and induced VT had an identical morphology. Antitachycardia pacing was effective in terminating 18 of 19 (95%) induced VTs and 14 of 18 (78%) spontaneous VTs. Antitachycardia pacing was effective in terminating 9 of 12 episodes of morphologically different spontaneous VTs and 5 of 6 episodes of morphologically identical spontaneous VTs (p = NS). Thus, the characteristics of VT induced at predischarge study correlate poorly with those of subsequent spontaneous VT episodes due to the induction of faster "nonclinical" VTs at predischarge testing. This may limit the applicability of predischarge testing in tailoring antitachycardia pacing algorithms.

Algorithms↗
PubMed1999

Ablation of ventricular tachycardia in the setting of coronary artery disease.

Ablation of reentrant ventricular tachycardia (VT) is an accepted therapy for certain patients with VT caused by coronary artery disease (CAD). Its use is currently limited to patients with sustained, monomorphic, hemodynamically tolerated VT. The use of entrainment in mapping reentrant VT has made possible increasingly accurate localization of critical sites on the reentrant pathway that are amenable to ablation. Recent work has examined the accuracy with which various mapping criteria are able to predict successful ablation of reentrant VT in patients with CAD. Other recent studies have investigated attempted ablation of all inducible VTs in patients with multiple VT morphologies. In the future, substrate mapping may make possible ablation of VT in patients with nonsustained or fast, hemodynamically unstable VTs, thus allowing VT ablation to become a first-line therapy for many patients with VT in the setting of CAD.

Body Surface Potential Mapping↗
PubMed1999

Entrainment of typical AV nodal reentrant tachycardia using para-Hisian pacing: evidence for a lower common pathway within the AV node.

INTRODUCTION: Despite the ability to cure atrioventricular nodal reentrant tachycardia (AVNRT) by radiofrequency catheter ablation with a high success rate, the exact localization of the tachycardia circuit is still not well established. The presence of AV nodal tissue between the typical AVNRT circuit and the His bundle, constituting a lower common pathway (LCP), remains controversial. METHODS AND RESULTS: Entrainment of AVNRT during para-Hisian stimulation allows accurate measurement of the His- to- atrial (HA) interval which is part of the same circuit as that of the tachycardia. With an LCP, during tachycardia, there is simultaneous conduction from the low turnaround of the circuit to the atrium (via the fast pathway) and to the His bundle (via the LCP). However, during entrainment by para-Hisian pacing, the impulse has to retrogradely depolarize sequentially the LCP and the fast pathway. Therefore, in the presence of an LCP, the HA interval duration during tachycardia (HAt) should be shorter than that of during entrainment by para-Hisian stimulation (HAe). We considered an LCP present when Hae - HAt was > or = 10 msec. Entrainment of typical AVNRT with para-Hisian stimulation was performed in 23 consecutive patients (21 females) with a mean age of 45+/-17 years. LCP was considered to be present in 18 of 23 patients (78%). In addition, transient His-bundle dissociation from the ongoing tachycardia occurred in seven patients (30%). CONCLUSION: These results support the presence of a LCP during typical AVNRT.

Adolescent↗
PubMed1999

Electrophysiology of postinfarction ventricular tachycardia: a paradigm of stable reentry.

Sustained monomorphic ventricular tachycardia (VT) is a paradigm of a stable reentrant rhythm. The hallmark of stable reentry is the presence of an excitable gap, which in reentrant VT composes 15% to 45% of the tachycardia cycle length. Resetting allows definition of the extent and pattern of the excitable gap. Site-specific resetting responses suggest that the VT circuit has both functionally and anatomically derived characteristics. Entrainment provides information regarding the effects of overdrive pacing on properties of the tissue composing the circuit rather than on properties of the tachycardia itself. These data help us to understand the mechanisms of pharmacologic agents and to direct ablation of reentrant VT.

Animals↗
PubMed1998

An episode of ventricular tachycardia during long-duration spaceflight.

An episode of nonsustained ventricular tachycardia was recorded from a crew member during the second month aboard the MIR space station. Although asymptomatic, this cardiac event increases the concern that serious cardiac dysrhythmias may be a limiting factor during long-duration spaceflight.

Adult↗
PubMed1998

Diagnostic yield and optimal duration of continuous-loop event monitoring for the diagnosis of palpitations. A cost-effectiveness analysis.

BACKGROUND: Continuous-loop event recorders are widely used for the evaluation of palpitations, but the optimal duration of monitoring is unknown. OBJECTIVE: To determine the yield, timing, and incremental cost-effectiveness of each week of event monitoring for palpitations. DESIGN: Prospective cohort study. PATIENTS: 105 consecutive outpatients referred for the placement of a continuous-loop event recorder for the evaluation of palpitations. MEASUREMENTS: Diagnostic yield, incremental cost, and cost-effectiveness for each week of monitoring. RESULTS: The diagnostic yield of continuous-loop event recorders was 1.04 diagnoses per patient in week 1, 0.15 diagnoses per patient in week 2, and 0.01 diagnoses per patient in week 3 and beyond. Over time, the cost-effectiveness ratio increased from $98 per new diagnosis in week 1 to $576 per new diagnosis in week 2 and $5832 per new diagnosis in week 3. CONCLUSIONS: In patients referred for evaluation of palpitations, the diagnostic yield of continuous-loop event recording decreases rapidly after 2 weeks of monitoring. A 2-week monitoring period is reasonably cost-effective for most patients and should be the standard period for continuous-loop event recording for the evaluation of palpitations.

Adult↗
PubMed1998

Usefulness of ST-segment elevation in lead III exceeding that of lead II for identifying the location of the totally occluded coronary artery in inferior wall myocardial infarction.

The presence of ST-segment elevation in lead III exceeding that of lead II, particularly if combined with ST elevation in lead V1, proved to be a powerful marker for occlusion of the proximal or midportion of the right coronary artery. These findings helped to determine the extent of myocardium at risk in inferior wall myocardial infarction and may further guide the decision to administer thrombolytics.

Algorithms↗
PubMed1998

Characteristics of the temporal and spatial excitable gap in anisotropic reentrant circuits causing sustained ventricular tachycardia.

The excitable gap of a reentrant circuit has both temporal (time during the cycle length that the circuit is excitable) and spatial (length of the circuit that is excitable at a given time) properties. We determined the temporal and spatial properties of the excitable gap in reentrant circuits caused by nonuniform anisotropy. Myocardial infarction was produced in canine hearts by ligation of the left anterior descending coronary artery. Four days later, reentrant circuits were mapped in the epicardial border zone of the infarcts with a multielectrode array during sustained ventricular tachycardia induced by programmed stimulation. During tachycardia, premature impulses were initiated by stimulation at sites around and in the reentrant circuits, and their conduction characteristics in the circuit were mapped. All circuits had a temporal excitable gap in at least part of the circuit, which allowed premature impulses to enter the circuit. Completely and partially excitable segments of the temporal gap were identified by measuring conduction velocity of the premature impulses; conduction was equal to the native reentrant wave front in completely excitable regions and slower than the reentrant wave front in partially excitable regions. In some circuits, a temporal gap existed throughout the circuit, permitting the entire circuit to be reset over a range of premature coupling intervals, although the size of the gap varied at different sites. In other circuits, the gap became so small at local sites that even though premature impulses could enter the circuit, the circuit could not be reset. Premature impulses could terminate reentry in circuits that could be reset or not. We also found a significant spatial gap, which was identified by determining the distance between the head of the circulating wave front, which could be located on the activation map, and its tail, which was the site most distal from the head as located by the site of entry of the premature wave front into the circuit. The spatial gap could also vary in different parts of the circuit. Therefore, nonuniform anisotropic reentrant circuits have both a temporal and spatial excitable gap with fully and partially excitable components that change in different parts of the circuit.

Animals↗
PubMed1998

Twiddler's syndrome variants in ICD patients.

Three cases of twiddler's syndrome in patients with an abdominally implanted cardioverter defibrillator (ICD) and an endocardial lead system are reported. The condition was detected when an increase in pacing threshold or lead impedance was noted at routine follow-up. Successful revision was possible in all patients; however, a recurrence in one patient necessitated removal of the device. Elderly female patients with some degree of obesity appear most susceptible. Minimizing pocket size and suturing of the device to the fascia should decrease the chance of developing this problem.

Aged↗
PubMed1998

ST segment elevation induced by class IC antiarrhythmic agents: underlying electrophysiologic mechanisms and insights into drug-induced proarrhythmia.

Three patients in whom Class IC sodium channel blockers induced ST segment elevation in leads V1 through V3 are described. The underlying electrophysiologic mechanism, implications for drug-induced proarrhythmia, and the relationship of the finding to the Brugada syndrome type of idiopathic ventricular fibrillation are discussed.

Anti-Arrhythmia Agents↗