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Biomedical subjects

S S Barold

Publications and source records attributed to S S Barold.

At least 145 records · Page 8Linked to original sources
PubMed1983

Doppler echocardiographic studies in sequential atrioventricular pacing.

Six patients with sequential atrioventricular pacemakers were studied by Doppler echocardiography. A commercially available continuous wave system (transcutaneous aortovelography) was used and the transducer was placed in the suprasternal notch and angled to obtain peak aortic arch blood flow velocity. Changes in Doppler peak velocity have been previously shown to correlate closely and reliably with changes in hemodynamically measured stroke volume/cardiac output in the same patients following interventions. In all patients, the pacemaker was programmed from DVI mode to VVI (heart rate was kept constant) and then back to DVI, with the Doppler transducer held in a fixed position all the time, and peak velocities measured after the patient had been in any particular mode for at least 1 minute. Five of 6 patients showed reduction in peak velocities ranging from 13-25% (mean 18.4%) when the pacing mode was switched from DVI to VVI. Doppler peak velocity remained unchanged in 1 patient. Doppler echocardiography represents a simple, noninvasive method for estimating increments in stroke volume/cardiac output obtained with sequential AV pacing.

Atrioventricular Node↗
PubMed1981

Transient early T wave sensing by implanted programmable demand pulse generator.

A seven-year-old girl with a permanent epicardial programmable pulse generator developed inappropriate slowing of the pacing rate due to oversensing a combination of T wave and afterpotential voltage. This phenomenon occurred only in the first three days after implantation and was demonstrable only at long programmed pulse widths. Our observations suggest that the current of injury in the early post-operative period may generate a relatively high T wave voltage capable of combining with a large afterpotential to produce a signal exceeding the sensitivity of a demand pulse generator.

Cardiac Pacing, Artificial↗
PubMed1981

Autointerference of demand pulse generators.

We describe in this report two cases of autointerference of demand pacemakers by signals originating within a pulse generator itself rather than the electrode or connection. Restoration of regular fixed rate pacing upon application of the magnet cannot differentiate between an external or internal source of oversensing as exemplified in our two cases. The absence of any visible interference on the surface electrocardiogram and the relatively late appearance of autointerference in the life of a pulse generator may mimic an intermittent fracture (or insulation defect) with over sensing of false signals. Autointerference of demand pacemakers, although rare, should be added to the list of causes producing oversensing and prolongation of the spike-to-spike interval.

Aged↗
PubMed1981

Interpretation of electrocardiograms produced by a new unipolar multiprogrammable "committed" AV sequential demand (DVI) pulse generator.

This paper describes our approach to the interpretation of electrocardiograms produced by a new unipolar multiprogrammable "committed" DVI pulse generator (Intermedics) during normal function. The arrhythmias engendered by this new DVI pacemaker may be better understood by conceptualizing the recycling mechanism in terms of a simple atrial pulse generator with two important qualification: 1) the ventricular stimulus obligatorily follows the atrial stimulus after 155 ms (AV sequential interval); 2) the pulse generator senses ventricular events (via the ventricular electrode) but recycles according to its atrial timing cycle (AA interval). These characteristics lead in turn to two important consequences: a) the QA interval (from the onset of a sensed QRS complex to the succeeding atrial stimulus) must be longer than the VA interval (from a ventricular stimulus to the succeeding atrial stimulus) by a period equal to or slightly greater than the AV sequential time. This may be considered to represent a form of hysteresis. b) the pacemaker refractory period always starts at the onset of an atrial cycle (AA interval( and therefore occurs after the delivery of an atrial stimulus or after a sensed ventricular event. The above characteristics may cause pacemaker stimuli to fall within the P wave, PR interval, QRS, ST segment and the ascending limb of the T wave during normal function of the pulse generator. Superficially, these peculiarities resemble malfunction and may be quite befuddling but they all occur predictably according to the electronic design of the pulse generator.

Arrhythmias, Cardiac↗
PubMed1980

Sources of error in the determination of output voltage of pulse generators by pacemaker system analyzers.

The use of threshold or pacemaker system analyzers with widely different characteristics has introduced potential sources of error in the determination of the output voltage of pulse generators. This is further compounded by the availability of pulse generators with diverse waveform configurations and programmability capabilities. Because of this non-uniformity, the physician must have some rudimentary knowledge of waveform characteristics and appreciate the limitations of threshold or pacemaker system analyzers to avoid the unnecessary replacement of normally-functioning pulse generators.

Electric Power Supplies↗
PubMed1980

Characterization of pacemaker arrhythmias due to normally functioning AV demand (DVI) pulse generators.

Normally functioning DVI pulse generators with different electronic characteristics may cause complex cardiac arrhythmias that must not be interpreted as pacemaker malfunction. When there is no refractory period after the atrial output, a DVI pulse generator may deliver atrial pacemaker impulses at irregularly shortened intervals and produce an increase in the atrial pacemaker rate compared with the programmed free-running AV sequential rate. Theoretically this variation of the atrial cycle length can occur only within a well-defined range that represents the difference between the ventricular and atrial output escape intervals. In reality, the interplay of the spontaneous sinus rate, duration of AV conduction, time of sensing the ventricular electrogram in relation to the surface QRS complex, and the programmed AV sequential time all influence the atrial pacemaker rate. DVI pulse generators may also create interesting arrhythmias such as pseudopseudofusion beats (delivery of an atrial spike within the QRS complex), double pseudofusion beats, and double pacemaker impulses within the QRS complex according to the electrophysiologic circumstances and specifications of the pulse generator.

Arrhythmias, Cardiac↗