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Biomedical subjects

S Furman

Publications and source records attributed to S Furman.

At least 253 records · Page 14Linked to original sources
PubMed1979

The autodiagnostic pacemaker.

Loss of normal pacemaker stimulation and/or sensing functions requires prompt detection, automatic correction, and automatic and continuous "marking" of the intermittent failure. The autodiagnostic pacemaker (ADP) detects "failure to capture" (FC) by distinguishing, at its single stimulating and sensing electrode, between the normal biphasic cardiac response evoked by an adequate stimulus (corresponding to the QRS and T waves on the surface cardiogram) and the monophasic pseudo-response generated by electrotonic spread of a subthreshold stimulating current. Detection of "failure to sense" (FS) spontaneous cardiac activity requires two amplifiers: a "timing control" amplifier of standard fidelity and standard (approximately 250 ms) refractory period, and a second amplifier which has negligible refractoriness and provides high fidelity amplification of all evoked and spontaneous activity. Failure to sense (FS) is defined as a specified number of consecutive failures to recycle correctly the pacemaker's timing circuits. Similarly, a specified number of consecutive failures of the stimulus to evoke an active cardiac response is defined as a failure to capture (FC). When FC is detected, the ADP doubles the applied stimulus voltage and generates marker pulses which follow every subsequent stimulus by 40 ms. The marker pulses appear on the surface electrocardiogram, serving as an externally detectable "memory" of the earlier, possible corrected, failure. When FS is detected, non-stimulating marker pulses, of a different time relation (80 ms delay) to each stimulus, are generated continually and can also be detected externally. The ADP has been tested in 14 anesthetized, open-chest dogs. Unipolar rather than bipolar electrodes were used as they rpovided more reliable stimulation and more satisfactory electrograms for detection.

Animals↗
PubMed1979

Nuclear pacemakers.

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Electric Power Supplies↗
PubMed1979

Comparison of active and passive adhering leads for endocardial pacing.

The frequency of lead failure requiring invasive correction in a total of 276 implants of four different transvenous leads (6907, continuous lead, IE-65-I, and MIP 2000) was observed during a one-and-one-half year period with a minimum of two months follow-up post-implant. Implants were on a successive sequential basis, randomly distributed between the two surgeons normally performing implants, and unselected for presumed ease or difficulty of the procedure. Failure rates with the 6907 and continuous leads were 7 of 76, or 9.2%; with the IE-65-I, 2 of 76, or 2.6%; and with the MIP 2000, 8 of 45, or 17.8%. The difference between the IE-65-I and the two conventional leads was significant at the 5% level, and between the IE-65-I and the group of the other three at the 1.6% level. The MIP 2000 was significantly different from the other three leads at the 2.7% level. Previous clinical experience with 849 implants with continuous and 6807 leads indicated that the overall data was similar to that obtained in the present evaluation. No significant differences in failure rates between surgeons and no measurable "practice effect" could be detected. It was concluded that the design of the lead is a major factor in the differing need for early secondary intervention.

Aged↗
PubMed1979

Early malfunction of transvenous pacemaker electrodes. A three-center study.

A 3-year study by three medical centers has revealed a 1-year electrode malfunction rate of 7.4%; most malfunctions occurred within the first 30 days. The incidence of unavoidable early malfunction (3.2%) fell within the 5% standards suggested by the committee report of the Inter-Society Committee on Heart Diseases. Incidences of obscure cause (3.2%) may be difficult to identify prospectively and may be, to a certain extent, unavoidable. The majority of the malfunctions (4.2%) showed specific clues that indicated that they were preventable. Successful repositioning was achieved on the first attempt in 80.6% of the cases with malfunction, and only 0.7% required ultimate myocardial electrode implantation. The principal clues to potentially unsatisfactory positioning included the presence of a large right ventricle with or without tricuspid insufficiency, current thresholds greater than 0.5 mA and ST-segment deviations on the intracardiac electrogram of less than 2 mV. Electrode malfunction may be more common with bipolar than with unipolar electrodes; but significant differences in the incidence of malfunction among different unipolar electrodes were observed. These data indicate that further developments in transvenous electrode design are warranted.

Arrhythmia, Sinus↗
PubMed1978

Termination of ventricular tachycardia with bursts of rapid ventricular pacing.

Bursts of rapid ventricular pacing used during 573 episodes of ventricular tachycardia in 23 patients terminated 5 12 episodes (89 percent), with burst rates averaging 56 beats/min above the ventricular tachycardia rate, for 5 to 10 captures. Tachycardia was accelerated by pacing bursts to rates below 300 beats/min in 16 episodes (3 percent); 10 of these terminated spontaneously or responded to further bursts. Acceleration of heart rate to more than 300 beats/min or ventricular fibrillation occurred six times (1 percent), each episode requiring direct current cardioversion. Pacing bursts had no effect in 38 instances (7 percent), mostly in patients with terminal cardiogenic shock. Implantable pacemakers delivering bursts of rapid ventricular pacing were placed in two patients who have used these units at home. No deaths were associated with bursts of rapid ventricular pacing, which is an effective, rapid, pleasant alternative to repeated direct current cardioversion and a useful tool during electrophysiologic testing in patients with recurrent tachycardia.

Adolescent↗
PubMed1977

Inhibition of a ventricular synchronous pacemaker.

Noncompetitive ventricular synchronous pacemakers (VVT) have been available since 1965. Most presently available and earlier models have a single, fixed pulse-to-pulse interval divided into a total refractory period of 350 to 400 msec., followed by a sensitive period. During the refractory period the pacemaker will not respond to QSR complexes or electrical signals, but a pacer stimulus will be produced during the sensitive period. The generator cannot be inhibited under any circumstances. The Cordis Omni-Sctocor has a refractory period and two sensitive periods, during one of which the generator is inhibited. Unlike other ventricular synchronous pacers, the Omni-Ectocor is capable of inhibition by single or multiple ventricular or other signals, of slowing or increase of the stimulus formation rate which depends on the timing of the premature ventricular contractions, and of inhibition by a run of ventricular tachycardia or by electromagnetic interference. The rate of interference producing these effects is a function of the automatic rate to which the generator is programmed. All of these factors must be considered for proper interpretation of the ECG.

Electrocardiography↗
PubMed1977

Cardiac pacing and pacemakers II. Serial electrophysiologic-pharmacologic testing for control of recurrent tachyarrhythmias.

The place of pacemakers in the treatment of tachyarrhythmias has expanded far beyond the initial role in the brady-tachy syndrome, of providing a "minimum guaranteed rate" while medications suppress the tachycardia. Techniques have been developed for prevention, termination, and duplication of a patient's spontaneous tachycardia under safe catheterization laboratory conditions. Combined with accumulating information about the normal responses to electrophysiologic stresses, these techniques have led to a new dimension in arrhythmia control. Most tachycardias previously felt to be refractory can be controlled after serial electrophysiologic-pharmacologic testing, during which sequential pharmacologic and pacer regimens are tested until a combination is found which prevents induction of tachycardias, and/or a pace mode is found which reliably terminates the tachycardia. Use of such an approach reduces hospital admissions and referral for surgery, and eliminates prolonged hospitalization for assessment of therapy in patients with infrequent but potentially lethal spontaneous tachycardias.

Adolescent↗