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Biomedical subjects

S Furman

Publications and source records attributed to S Furman.

At least 109 records · Page 6Linked to original sources
PubMed1991

The present status of cardiac pacing.

At the time of its inception, pacemaker treatment only had the goal of reliably maintaining a regular ventricular rhythm. After solving technical problems of detection, function and introduction of AV-sequential pacing (1962), cardiac hemodynamics have become the central issue of interest. While, at low heart rates atrial contraction contributes meaningfully to cardiac output, it has been shown that for physiologic needs and high rates, rate-adaptive single-chamber stimulation is hemodynamically more favorable than non-rate adaptive AV-sequential pacing. A rate-adaptive stimulation, more suited to physiologic needs with incorporation of a combination of various control parameters will improve pacing technology in the future. Anti-tachycardia stimulation, now integrated into the function of the implantable cardioverter/defibrillator has substantially widened the scope of this aspect of pacing.

Arrhythmias, Cardiac↗
PubMed1990

Connectors.

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Electrodes, Implanted↗
PubMed1990

Clinical predictors and natural history of atrial fibrillation in patients with DDD pacemakers.

Effective DDD pacing requires that patients remain free of atrial fibrillation (AF). Four hundred eighty-nine consecutive patients undergoing initial transvenous DDD implants were reviewed to determine the incidence of postimplant AF in this population and to assess what factors, known at implant, predicted the later development of AF. The variables analyzed included age, sex, indication for implant (dominant SA or AV node disease), history of AF, atrial electrogram characteristics and pacing threshold, and the status of retrograde conduction. Forty-eight patients (9.8%) developed AF a mean of 23 months postimplant, and 11 of these patients returned to sinus rhythm and were managed once again in DDD for significant periods. A prior history of AF and the presence of dominant sinoatrial disease were far more prevalent in the patients who developed AF (P less than 0.001) though the vast majority of patients with these two independent risk factors remained in sinus rhythm through much or all of their follow-up period. We conclude that the incidence of AF is not of a magnitude to preclude DDD pacing in the vast majority of patients in sinus rhythm at implant.

Aged↗
PubMed1990

Survival of implantable pacemaker leads. The Implantable Lead Registry.

Early polyurethane leads were reported to have a high incidence of materials failure. In 1979 a six-center registry was begun. By October 31, 1989, 7,311 leads had been registered and lead longevity was calculated by individual manufacturer, cumulatively for all manufacturers and for individual leads. Each lead was registered at implant and at removal from service as having been removed for materials failure or for unrelated reasons. Calculations were made for 23 models and for a total of three manufacturers with more than 100 leads implanted. Four thousand seven hundred and sixty three leads (65.1%) were from Medtronic; 2,177 (29.8%) from Cordis; 297 (4.1%) from Intermedics; and 77 (1.0%) were from all others. The 10-year cumulative survival of Medtronic leads was 96.6 +/- 0.4%; for Cordis leads it was 99.9 +/- 0.1% and for Intermediates leads 97.7 +/- 0.9%. Three lead models registered over 100 units and had poorer survival at 5 years than the remainder of all manufacturers' experience. They were #6972 (n = 107) with 78.6 +/- 4.5%; #6991U (n = 294) with 90.6 +/- 1.9%; and #4012 (n = 288) with 97.3 +/- 1.5%. Other possibly failed models did not achieve statistical significance. It can be anticipated that a lead which survives to the seventh year will have prolonged longevity as thereafter additional failures are uncommon.

Electrodes, Implanted↗
PubMed1990

Differentiation of sinus rhythms from supraventricular tachydysrhythmias by activation sequence and timing.

Implantable device detection of tachydysrhythmias remains unreliable and inexact. False responses may occur because of misinterpretation of sinus tachycardia (ST) as a supraventricular tachydysrhythmia (SVTD). Timing of atrioventricular (AV) activation and ventricular dispersion identified and discriminated between ST and SVTDs in 11 dogs. Three bipolar epicardial electrodes recorded left atrial and left and right ventricular depolarizations simultaneously during normal sinus rhythm (NSR) (mean of 5 beats in 11/11 dogs), ST produced by phlebotomy (50 beats in 10 episodes in 6/11) or isoproterenol infusion (105 beats in 21 episodes in 10/11), sinus bradycardia (SB) produced by vagal stimulation (140 beats in 29 episodes in 10/11), and during atrial flutter (AFL) (15 beats in 3 episodes in 3/11) and atrial fibrillation (AF) (152 beats in 31 episodes in 9/11) induced by programmed electrical stimulation. During lidocaine infusion, NSR (55 beats in 11 episodes in 10/11 dogs), SB (84 beats in 17 episodes in 7/11), AFL (10 beats in 2 episodes in 1/11), and AF (103 beats in 21 episodes in 7/11) were recorded. During isoproterenol infusion, SB (45 beats in 9 episodes in 5/11), AFL (15 beats in 3 episodes in 2/11), and AF (64 beats in 13 episodes in 5/11) were recorded in addition to ST. The interval between the left atrial and left ventricular intrinsic deflections (A-V1) and between the left and right ventricular intrinsic deflections (V1-V2) of each beat was measured. The mean value (msec) of A-V1 and V1-V2 in each episode was compared to NSR in the same dogs. A difference of greater than or equal to 16 ms was used for differentiation. In all cases except SB with first-degree AV block, V1-V2 in each episode was insignificant (0-14 msec), categorizing the rhythms as supraventricular. During NSR, ST and SB without AV block, delta A-V1 was small (0-15 msec). In contrast delta A-V1 was greater than or equal to 16 ms in 6/8 episodes of AFL. The remaining two episodes could be differentiated by the greater number of atrial versus ventricular beats. AF could be detected by the variability of A-V1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Rate-modulated pacing.

The primary role of cardiac rate in adapting cardiac output to changing physiological needs has been more clearly recognized in recent years. Previously, the rate of cardiac stimulation had been determined either at pacemaker manufacture, by programming a single rate, or by sensing the atrium. More recently, sensing another physiological or nonphysiological function that changes in response to body need has become possible. Exercise changes blood oxygen saturation, central venous pH, central venous temperature, minute ventilation and respiratory rate, stroke volume, circulating catecholamines, QT interval, evoked endocardial response to a stimulus, and the mechanics of myocardial contraction. Some sensors respond to muscle work but not to intellectual effort or emotion. Pacemaker-based sensors of physiological function or activity allow a change in cardiac stimulation rate in response to need. Whichever sensor is used, increases in ventricular rate during exercise regularly produce a cardiac output response. Single-chamber, rate-modulated pacemakers in atrium or ventricle and dual-chamber devices are now implanted on a widespread basis. These drive the atrium, the ventricle, or both, sensing or pacing the atrium at a rate determined by the sensor.

Body Temperature↗
PubMed1990

[Implanted cardioverters-defibrillators].

The paper represents the data on clinical use of implantable cardioverters-defibrillators. These apparatuses ensure effective arrest and prevention of episodes of ventricular tachyarrhythmias. The potentialities of the method are largely determined by recognition sensitivity and specificity of various tachyarrhythmias. The obvious advantage of the method is an increase in patients' survival reaching 60% within 5 years of cardioverter-defibrillator postimplantation.

Electric Countershock↗
PubMed1989

Lyme carditis: an important cause of reversible heart block.

Lyme disease is a tick-borne spirochetal infection, characterized by erythema chronicum migrans and an acute systemic illness. The disease is endemic in many parts of the north-eastern United States. Without treatment, late rheumatic, neurologic, and cardiac complications frequently occur. We report four serologically confirmed cases of Lyme carditis in previously healthy young men (mean age, 45 years) from endemic areas. Each presented with severe symptomatic atrioventricular block, three with episodes of prolonged ventricular asystole. Two had permanent pacemakers implanted (one was later removed), and another, very nearly did, before diagnosis. All four patients were treated with antibiotics, and in each case their rhythm returned to sinus, though one patient has Wenckebach second degree block with atrial pacing at 120 beats/min 16 months later. Carditis occurs in 4% to 10% of cases of Lyme disease and usually begins 3 to 6 weeks after the initial illness. It manifests as a transient myocarditis with varying degrees of atrioventricular block. The diagnosis is made primarily on clinical grounds and confirmed by serologic testing. Temporary cardiac pacing is frequently needed by patients who have severe heart block with hemodynamic instability. The evidence suggests that, in most cases, the block is at the level of the atrioventricular node. The block generally resolves completely with antibiotic treatment. Complete heart block rarely persists more than 1 week and the long-term prognosis appears to be excellent. Consideration and prompt recognition of this potentially lethal, but reversible, cause of heart block is crucial in order to avoid inappropriate permanent pacemaker implantation.

Adult↗
PubMed1989

AICD benefit.

Explore the source record for details and available documents.

Electric Countershock↗
PubMed1989

Treadmill assessment of an activity-modulated pacemaker: the importance of individual programming.

Maximum benefit from a rate-modulated pacemaker requires individualized programming of rate response settings. We tested an externally strapped activity-sensing pacemaker (Activitrax-Medtronic 8400) in eight healthy volunteers, to assess the pacing responses of the different rate response and activity threshold settings. Five males and three females, aged 20 to 70 years (mean 40), performed a total of 67 treadmill exercise tests, using a specific protocol designed to assess the activity-sensing unit. The external unit was compared to implanted units in four patients, to validate its accuracy. A reproducible sinus response to the treadmill protocol was observed, against which pacing responses were compared. The activity threshold determines the degree of activity required to elicit a pacing rate response, whereas the rate response setting determines the rate attained. Rates of 140 bpm were rarely achieved, despite vigorous exercise. The sensor responds rapidly to activity, not to physiologic demand; to increase in speed, not grade. Four patients performed repeated limited treadmill tests to determine their optimum program setting, with symptomatic status and the healthy volunteer sinus response as guides. These results, and those from the external Activitrax unit, suggest that LOW 6 and MEDIUM 6-10 settings will prove optimum for most patients.

Adult↗