Search PubMed⌕ Search

Biomedical subjects

S Furman

Publications and source records attributed to S Furman.

At least 271 records · Page 15Linked to original sources
PubMed1977

Cardiac pacing in children and adolescents.

Nineteen patients aged 1 month to 18 years underwent implantation of a cardiac pacemaker and were followed up for up to 9 years (average duration of pacing 54 months). Complete heart block was present in 16 patients and sinus nodal dysfunction in 3. Heart block was presumably of congenital orgin in eight, secendary to cardiac surgery in seven and subsequent to cardiac catheterization in one. Sinus nodal dysfunction was of presumed congenital origin in one and occurred after cardiac surgery in two. Pacing was required because of syncopal attacks in eight patients, three of whom had congestive heart failure or low cardiac output on physiologic studies. It was required in four because of congestive heart failure, in two because of low cardiac output (one with a wide QRS complex), and in five for postoperative rhythm control. With return of sinus rhythm after 2 and 3 months, respectively, pacing was discontinued in two patients. One child was partially corrected disease died within 3 months, one died of wound breakdown and sepsis after 10 months of pacing and one died suddenly 4 years after implantation. All others have returned to normal activity; only one requires cardiac medication. The degree of emotional stability has been striking. Asynchronous and atrial synchronous pacing are of equal therapeutic value. The very small radiofrequency implanted receiver has been useful in younger children. The major problems have been caused by the large size and short longevity of the generators and the child's growth stressing the lead system. Transvenously implanted pacemakers have presented no greater management problems than those placed during thoracotomy.

Adolescent↗
PubMed1977

A comparison of unipolar and bipolar electrograms for cardiac pacemaker sensing.

Simultaneous unipolar and bipolar electrograms were recorded and compared from 49 pacemaker patients with bipolar endocardial electrodes. Average bipolar depolarization signal voltage equalled that of unipolar but showed greater variation. Bipolar and unipolar slew rates were equal in both mean and variance. The proximal pole voltage had little effect on the bipolar result in 8% of the cases, tended to cancel the tip voltage in 49% of the cases and augmented the tip voltage in 43% of the electrograms. The average bipolar R wave duration was 28% less, the T wave amplitude 34% less, and the ST-segment elevation 37% less than the unipolar values. By consistently attenuating the undersirable T waves and ST elevations, while leaving the depolarization signal unaffected, the bipolar electrode offered the advantage of a superior signal-to-noise ratio for sensing depolarization. In one case, however, the bipolar signal was so small as to cause a clinical sensing failure.

Arrhythmias, Cardiac↗
PubMed1977

Vulnerability of the mildly ischemic ventricle to cathodal, anodal, and bipolar stimulation.

We studied the difference between myocardial vulnerability to arrhythmias caused by cathodal, anodal, and bipolar stimulation in 29 dogs with partial right coronary artery occlusion. We used 2-msec duration stimuli of up to 8 mA to determine the ventricular vulnerable periods, their relationship to the refractory periods, and the fibrillation or multiple response thresholds for unipolar anodal and cathodal stimulation after two premature ventricular contractions. The vulnerable period for arrhythmias began at the end of the respective refractory periods and terminated at a specific time within the cardiac cycle. Within this period the arrhythmia and excitation thresholds were equal. Because shorter refractory periods were obtained with anodal stimulation than cathodal, the vulnerable periods for anodal stimulation were longer. This indicated that the vulnerable periods for bipolar stimulation also would be longer than for unipolar cathodal stimulation since bipolar and anodal refractory periods are equal when the cathode and anode are of similar surface area. Results from seven of the experiments showed that a dual focus of excitation, which can only occur with bipolar stimulation, did not make the ventricle more vulnerable to arrhythmias than did unifocal stimulation. These results indicate that the difference between the arrhythmia vulnerability to unipolar cathodal, anodal, and bipolar stimulation is dependent on the relationship between their excitability characteristics, i.e., their strength-interval curves.

Animals↗
PubMed1977

Electrode causation of pacemaker inhibition.

Electromechanical nonphysiologic signals caused by the movement of intracardiac metal portions of an endocardial grasping electrode were shown to be "falsely" recycling an implanted pacemaker. The signals were similar in amplitude and slew rate to the ventricular electrogram and were terminated by ending the movement of the two metallic surfaces.

Arrhythmias, Cardiac↗
PubMed1977

The ventricular endocardial electrogram and pacemaker sensing.

During cardiac pacemaker implantation and pulse generator replacement, unipolar, right ventricular electrograms were recorded from 133 patients (77 at implantation and 56 at pulse generator replacement) at 200 mm. per second with a band pass of 0.1 to 2,000 Hz on photographic paper. Each signal was analyzed for electrogram structure, peak-to-peak voltage deflection, ST-segment displacement, and maximum voltage deflection/time (slew rate [dv/dt]). The QRS designation of the peripheral electrocardiogram was used for the endocardial electrogram wave forms, which are sufficiently similar to allow QRS terminology to be used. Of the acute electrograms (at implantation) 58 per cent had a small Q followed by an R wave which was 10 per cent or more of the S amplitude; 30 per cent had an R wave less than 10 per cent of the S; all had a straight line segment, within the QRS complex, exhibiting maximum amplitude and slew rate and a large ST-segment elevation. In 12 per cent the Q was followed by an R wave only. The mean voltage was 12.4 mv. +/- 5.5, the slew rate mean 2.9 v. per second +/- 1.5, and the ST displacement 4.0 mv. +/- 2.6. All chronic (over 6 months after implantation) electrograms but one had no ST-segment elevation, and all had an inverted T wave and a straight line segment extending from the highest to the lowest peaks of the QRS complex. The chronic voltage amplitude is 15 per cent lower and the slew rate 41 per cent lower than that of the acute electrogram. The margin of amplitude and slew rate required at implantation to maintain adequate postimplant sensing must accommodate these changes. The possibility of satisfactory pacing threshold associated with poor sensing exists. Knowledge of the amplitude and slew rate allows the determination of the optimal position for electrode placement and the sensitivity required for satisfactory pulse generator selection, design, and operation.

Electrocardiography↗
PubMed1976

Pacemaker failures characterized by continuous direct current leakage.

Pulse generator failure caused by continuous leakage of direct current through an output capacitor has not previously been appreciated. Routine post-explant electronic evaluation has identified the defect in six implanted and one external pulse generator. The constant direct current in the implantable units, 0.14 to 0.26 milliamperes, is in the range that produces ventricular arrhythmias in dogs although this did not occur in our patients. Evidence of local myocardial damage existed in four cases and of electrode deterioration in three. The implant failures occurred without warning and in four cases within 2 weeks of demonstrated normal function, blunting the predictive benefits of pacemaker monitoring programs. Capacitor discharge circuits used in many pacers are inherently capable of developing direct current leakage in the event of output capacitor short circuit. In one model of pacemakers such continuous direct current leakage caused 8.3 percent (3 of 36) of pulse generator failures, widely scattered in time at 23, 27 and 46 months after implant. Capacitor short circuit causing constant direct current leakage can masquerade as primary battery failure and should be suspected when cessation of pacer function is associated with increased threshold or poor myocardial electrogram without evidence of wire break or displacement.

Aged↗
PubMed1975

Removal of myocardial fragment containing a pacemaker electrode.

An implanted right ventricular electrode that had become infected and entrapped was removed using continuous traction. Upon removal it was found to be attached to an irregular mass of myocardium 2 to 3 cm long. No unfavorable effects resulted. A new pacemaker was implanted, and the patient has remained well.

Aged↗