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Biomedical subjects

D L Hayes

Publications and source records attributed to D L Hayes.

119 records · Page 7Linked to original sources
PubMed1984

Apparent pacemaker failure due to reversion circuitry within the programming device.

While being evaluated for a recurrent tachyarrhythmia, a patient with a permanent pacemaker underwent reprogramming of the unit from the DVI to the VVI mode for assessment of the underlying rhythm. Subsequent reprogramming of the pacemaker to the DVI or DDD mode was impossible despite multiple attempts and the use of multiple programmers. The problem was considered to be a malfunction of the pacemaker circuitry, and plans were made for the pacemaker to be explanted and a replacement unit implanted. Before the procedure, the pacemaker company was notified of the explantation. We subsequently learned that a special programming sequence had to be carried out because of reversion circuitry present in the pacemaker but not described in the available literature. This report emphasizes the need for familiarity with each of the individual pacemakers being implanted and the need for the manufacturer to be as specific as possible given the complexity of current units.

Equipment Design↗
PubMed1984

The effects of nuclear magnetic resonance imagers on external and implantable pulse generators.

This study evaluates the effect of nuclear magnetic resonance (NMR) scanning on pacemaker function. It must be emphasized that each manufacturer's pulse generators and each pacing modality may behave differently and, therefore, require individual evaluation. According to our results, patients with pacemakers should have their pacing activity monitored continuously during scanning with the NMR 1500 gauss imaging system. External pulse generators should be set to the asynchronous mode and placed outside the NMR image volume but within the radiofrequency (RF) shield. Implanted pacemakers should be verified for type and mode of operation. All implantable pulse generators evaluated reverted from the demand to the asynchronous mode within the magnetic field of the scanner. There was no observable damage to the discrete pacemaker components that were tested. In vivo testing of implantable single-chamber pulse generators did not significantly alter the pacemaker's operating parameters. Changes in stimulation rate analogous to the RF field pulse rate were seen. In single-chamber devices the resultant rate was a multiple of the RF frequency, changing to a value less than the normal asynchronous magnetic rate. With more sophisticated dual-chamber devices the results varied. With VDD pacing during RF scanning, the cardiac stimulation rate increased to a value analogous to the RF field modulation period. More extensive in vivo testing using different models of pulse generators of various manufacturers is needed to identify specific device susceptibility to the RF, time variance and steady-state magnet fields. From these data a comprehensive statement about NMR scanning of patients with implanted pacemakers can be made.

Electrocardiography↗
PubMed1984

Follow-up of DDD pacemakers.

With the increasing complexity of DDD pacemakers, follow-up of these pulse generators has also become more complex. A pattern for testing DDD pacemakers should be developed, the patient should be taken through these pacing sequences in a systematic way, and the values should be recorded. To adequately follow-up the patient with a DDD pacemaker, one must know the patient and his underlying rhythm, the pulse generator and its programmable flexibility, and any peculiarities of the particular pulse generator.

Aged↗
PubMed1983

Atrio-ventricular and ventriculo-atrial conduction times in patients undergoing pacemaker implant.

Pacemaker mediated reentrant tachycardias have been seen frequently during use of dual chamber sensing pacemakers and are dependent on the presence of intact retrograde (ventriculo-atrial) conduction. The status of a patient's retrograde (VA) conduction cannot be determined from the surface electrocardiogram. At the time of pacemaker implant the state of antegrade conduction should be determined at incremental atrial pacing rates, the exact timing measured from the intracardiac electrograms, i.e., from the intrinsic deflection of the intrinsic deflection of the ventricle. With this information obtained in 53 patients, it was possible to determine which patients could safely receive dual chamber sensing pacemaker devices, the appropriate pacemaker atrial refractory period setting to avoid pacemaker mediated tachycardias in those patients with intact retrograde conduction, and the optimal timing for programming the pacemaker's AV delay. Patients who have been studied in this manner and who were felt to be suitable for a dual chamber sensing device have not displayed pacemaker mediated reentrant tachycardias. Forty-seven percent of all patients who require pacemaker implant have VA 1:1 conduction; 67% of those with sinus node dysfunction and 14% of those with complete antegrade block have VA conduction at a mean interval of 235 +/- 50 ms (range 110-380 ms).

Atrioventricular Node↗
PubMed1983

Permanent endocardial pacing in pediatric patients.

Improved technology with smaller pulse generators and passive and active fixation endocardial lead systems has the potential for facilitating safe, reliable pacing in pediatric patients. Of 18 pediatric patients (mean age 11.1 years) undergoing permanent transvenous cardiac pacing during the period April, 1977, to January, 1981, two (11%) required reoperation during a mean follow-up of 18.8 months. Satisfactory stable pacing was maintained even in patients with dual-chamber pacing systems and in patients with transposition of the great vessels in whom a lead was placed in a morphologically left atrium. This reoperation rate of 11% contrasts with a reoperation rate of 32% in 22 pediatric patients (mean age 8.7 years) who underwent placement of ventricular-demand epicardial pacing systems during the same period. In our experience, transvenous endocardial pacing is the preferred route in pediatric patients because of the improved lead system survival and the potential for atrial or atrioventricular sequential pacing.

Adolescent↗
PubMed1983

Early experience with a universal (DDD) pacing device.

To assess the advantages and complications of a new universal (DDD) pacemaker, we studied retrospectively the initial 38 patients who received such a pacing device. This group consisted of 27 men and 11 women whose ages ranged from 23 to 89 years. The pacemaker was the initial one for 32 patients and was the replacement unit for 6. Indications for dual-chamber pacing included a need to maintain atrioventricular synchrony, the previous occurrence of the pacemaker syndrome or the presence of intact ventriculoatrial conduction, and previous success with atrioventricular sequential pacing. Pacemaker-mediated tachycardia developed in six patients during the follow-up period. All six were successfully treated by a change in pacing mode. Eighteen pacemakers remained in the DDD mode, 17 were reprogrammed to the DVI mode, and 3 were reprogrammed to the VVI mode. Seven patients experienced difficulties with loss of capture or undersensing, the most common problem being failure of atrial sensing. This was corrected in four of five patients by noninvasive reprogramming. Pacemaker-mediated tachycardia is a frequent complication that can be avoided by assessing ventriculoatrial conduction before implantation of the pacemaker. Use of the DDD device should be considered in patients in whom atrioventricular synchrony must be maintained or who have previously had the pacemaker syndrome with VVI pacing.

Adult↗
PubMed1983

Implantation of atrioventricular synchronous and atrioventricular universal pacemakers.

Implantation of pacemakers which sense in the atrium and the ventricle requires understanding of both antegrade conduction, from the atrium to the ventricle, and retrograde conduction, from the ventricle to the atrium. Of 53 patients undergoing pacemaker implantation, 25 (47%) had retained VA conduction and 25% of those with complete heart block had 1:1 retrograde (VA) conduction. Determination of both conduction intervals is made by recording the intrinsic deflections of the atrium and the ventricle and measuring the interval. Antegrade intervals (IDA leads to IDV) for those with intact conduction ranged from 189 to 325 msec (mean 212 msec). Retrograde intervals (StV leads to IDA) for those with intact VA conduction ranged from 110 to 346 msec (mean 235 msec). Of 16 patients having VDD and DDD pacemakers implanted without conduction studies, seven (44%) developed pacemaker-mediated tachycardia. The prevention of pacemaker-mediated reentry tachycardia requires knowledge of the VA conduction interval (if it exists) and programming of the atrial refractory period so that retrograde P waves fall within it and are unsensed.

Electrocardiography↗
PubMed1982

Stochastic frequency-domain tissue characterization: application to human spleens "in vivo'.

Ultrasonic waveforms backscattered from normal and pathologic human spleens were recorded in vivo using a high-speed digital data acquisition system. A frequency-domain analysis was performed for 50 digitized waveforms from each spleen, in which autocorrelations of frequency spectra were employed to measure the mean spacing among adjacent tissue scatterers. Mean scatterer spacing for normal spleens averaged 1.10 +/- 0.14 mm, whereas abnormal, diffusely of these measurements are in accord with those expected from splenic histology. The techniques described may be valuable in ultrasonic diagnosis of the spleen and other organs.

Adult↗
PubMed1979

Use of computed tomography in diagnosis of soft-tissue tumors.

Soft-tissue tumors can evade the usual diagnostic methods. In the case presented, computed tomography proved to be the best diagnostic tool in demonstrating a malignant extranodal lymphoma. Computed tomography is useful not only in detecting a tumor but also in determining its extent. This aids the surgeon in selecting and conducting the most appropriate operation.

Abdominal Neoplasms↗