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Biomedical subjects

D L Hayes

Publications and source records attributed to D L Hayes.

At least 91 records · Page 5Linked to original sources
PubMed1992

Testing of work environments for electromagnetic interference.

A challenge for pacemaker therapists is whether a patient working in an environment with the potential for electromagnetic interference (EMI) can return to their work after a pacemaker has been implanted. Common practice has been to prohibit pacemaker patients from using electric welding machines. Twelve work environments and a new method for monitoring the pacemaker rhythm in the presence of EMI were tested. The new method uses a special memory called the event record found in several Siemens Pacesetter pacemaker models. Surface ECGs with a marking system, intracardiac electrograms, and a digital monitor were used to verify the results with event records. The results from several sources of EMI are reported. Twenty-one in vivo and in vitro tests were performed in the work environments of 12 patients. Event records were useful and accurate both in vivo and in vitro. Electric are welding machines up to 225 A did not affect these pacemakers. Arc welding machines using 1,000 A or more inhibited the in vitro test system within 1 or 2 meters of the weld or power generator. Electric welding machines with high frequency voltage superimposed on the welding current affected the pacemaker when it was within 2 meters of the power unit and 1 meter of the weld. Very large industrial degaussing coils affected pacemakers within 2 meters. The test method using event records was found to be an effective addition to monitoring the pacemaker. These results are specific for the pacemaker models tested. Such testing allows the physician to make a knowledgeable decision regarding return to work for the pacemaker patient in a high EMI environment.

Electricity↗
PubMed1992

A multicenter experience with a bipolar tined polyurethane ventricular lead.

A multicenter study was undertaken to determine the failure rate of a specific polyurethane bipolar tined pacing lead, the Medtronic 4012 pacing lead. Six centers in the United States and Canada implanted 1,190 Medtronic 4012 pacing leads. The study was designed to determine the probability and clinical manifestations of lead failure. Only failures compatible with an insulation problem were included. The probability of a 4012 lead failure by Kaplan-Meier analysis was 20.9% at 6 years after implantation. Failures were manifested as sensing abnormalities, failure to capture, early battery depletion, and significant decrease in measured impedance compared with the previous impedance measurements. Of the 95 definite lead failures, 16 (16.8%) were associated with symptoms similar to those experienced before pacemaker placement. The observed failure rate is unacceptable, and strong consideration should be given to replacing the 4012 pacing lead in pacemaker-dependent patients and closely monitoring nondependent patients.

Aged↗
PubMed1992

Timing cycles of permanent pacemakers.

A clear understanding of the components of the pacemaker timing cycles is crucial to understanding and interpreting paced electrocardiograms. The information given in this article provides basic rules for timing cycles for pacing modes currently in use and pacing modes less frequently used but of importance in understanding current timing cycles. Although understanding basic timing cycles allows interpretation of most paced electrocardiograms, manufacturer-dependent variations of the timing cycle operation make it necessary to be intimately familiar with the design of each pacemaker to be interpreted.

Bradycardia↗
PubMed1991

Advances in pacing therapy for bradycardia.

Advances have been made rapidly in the field of cardiac pacing. The most significant technologic advance is that of pacemakers capable of rate-adaptive pacing. Multiple types of sensors are now used for rate-adaptive pacing; some are commercially available and many are undergoing clinical investigation. In the near future, clinical investigation will begin on pacemakers that incorporate dual simultaneous sensors for rate-adaptive pacing. Significant improvement has been made in electrode design. Electrodes with low thresholds allow improved battery longevity. Steroid-eluting leads have proven reliable and capable of avoiding the early threshold rise seen with other electrodes. Standardization of pacemaker connector dimensions is now under way. The International Standards Organization has established the guidelines for connector standardization, and the guidelines have been adopted by the major manufacturers. The ultimate "smart" pacemaker would be capable of autoprogramming most or all of its programmable features. Many autoprogramming features have already been incorporated, and several others such as automatic programming of output and sensitivity are under investigation.

Bradycardia↗
PubMed1991

Standardized informal exercise testing for programming rate adaptive pacemakers.

It is essential that patients with pacemakers capable of rate modulation undergo some form of exercise testing to assure appropriate rate modulation. Informal exercise testing is a reasonable and less expensive alternative to formal treadmill testing. Empiric adjustment of the rate response parameters by assessing the patient's rate response while walking at a self-determined casual and brisk pace has been used. However, no normals exist to determine the appropriate rate response for a "casual" and "brisk" walk. Volunteers were tested with metronome-guided casual and brisk walks in an effort to standardize the informal exercise and determine expected heart rate response for these levels of activity. Results of the metronome-guided rate response in normal volunteers may be useful in determining the appropriate rate response for pacemaker patients when tested in such an informal manner.

Adult↗
PubMed1991

Antitachycardia pacemaker treatment of postoperative arrhythmias in pediatric patients.

An automatic antitachycardia pulse generator (Intertach 262-12) was implanted in each of six pediatric patients (mean age, 10 years) with drug-resistant and persistent postoperative supraventricular arrhythmias. Four had bradycardia-tachycardia syndrome, two after a Mustard procedure for transposition of the great arteries, one after a Senning procedure for the same anomaly, and one after a Fontan procedure for univentricular heart with transposition of the great arteries. Of the two remaining patients, one had atrial flutter after a modified Fontan procedure for univentricular heart and one had intra-atrial reentry tachycardia after a modified Fontan procedure for double-outlet right ventricle with pulmonary stenosis. During a mean follow-up interval of 31 months after implantation, pacemakers were activated on multiple occasions and functioned appropriately in all six patients. Complications necessitated six invasive interventions in three patients: erosion or infection of the system, adaptor fracture, and connector block fracture on one occasion each and lead dislodgment on three occasions. Four of the six patients continued to take drugs at the end of this study; however, all patients had their drug therapy reduced and one was taking digoxin only. The number of hospital admissions decreased after implantation. Despite a number of technical challenges, this newer multiprogrammable antitachycardia pacemaker appears to be a valuable addition to the treatment of refractory postoperative supraventricular tachyarrhythmias in pediatric patients.

Adolescent↗
PubMed1990

Venous obstruction due to permanent transvenous pacemaker electrodes: treatment with percutaneous transluminal balloon venoplasty.

Transvenous placement of permanent pacemaker leads is currently the most common method for permanent cardiac pacing. Venous abnormalities, in particular venous stenosis or thrombosis (or both) frequently have been described, although most patients remain asymptomatic because of the development of an adequate venous collateral circulation. Venous obstruction often first becomes apparent during pacemaker lead revision, when difficulty passing the new pacing lead is encountered. In this report, we present two cases of venous stenosis and thrombosis due to permanent transvenous pacemaker electrodes and the use of percutaneous transluminal balloon venoplasty to relieve the venous obstruction.

Aged↗
PubMed1990

Facilitation of the subclavian-introducer technique with contrast venography.

The subclavian-introducer technique is a rapid and easily performed method of obtaining venous access for implanting permanent pacemaker electrodes. Although this technique has facilitated the participation of nonsurgeons in pacemaker implantation, the potential for complications is increased over the venous cutdown approach. This is particularly true in difficult cases, such as those with prior lead implants, venous thrombosis, or anomalous venous return. This article describes the use of contrast venography for facilitating an otherwise "blind" subclavian venipuncture. This method should make use of the subclavian-introducer technique safer.

Catheterization, Peripheral↗
PubMed1990

Quantitative analysis of Wenckebach behavior in DDD pacemakers.

Wenckebach-type behavior in P-synchronous pacing modes allows a gradual transition into 2:1 block. As this behavior is dependent on precise timing intervals, it can be quantitated with mathematical equations. In this report, equations for quantitating the Wenckebach escape rate and the (N + 1)/N block points have been derived. These equations were then used to produce plots of Wenckebach escape rates for given AV intervals, atrial refractory periods, and atrial rates. These equations were validated utilizing a DDD pulse generator interfaced with a patient simulation device. The predicted values for the Wenckebach escape rate and ratio (n = 33) correlated highly with the observed values (r = 0.99, P less than 0.0001, and r = 0.97, P less than 0.0001, respectively) thereby validating the derived equations. This quantitative analysis has allowed a close look at the pacing behavior between the maximum tracking rate and the 2:1 block point. These equations may be clinically useful for assessing whether a nontriggering P wave resulted from Wenckebach type block or atrial undersensing and for the more complicated interval analysis in DDDR pacing with rate responsive AV delays and postventricular atrial refractory periods.

Computer Simulation↗
PubMed1989

Advantage of discrepant upper rate limits in a DDDR pacemaker.

The latest cardiac pacing mode to become available is the dual-chamber, rate-modulated mode (referred to as DDDR), which restores both rate responsiveness and atrioventricular synchrony in patients with sinus node dysfunction and atrioventricular block. This pacing mode combines dual-chamber and single-chamber rate-modulated technologies. Thus, it is necessary to program both a maximum tracking rate and a maximum sensor rate, as in dual-chamber and single-chamber rate-modulated devices, respectively. These two upper rate limits are usually programmed to equivalent values. The case described herein illustrates one advantage of programming discrepant upper rate limits. The rapid tracking of supraventricular tachycardias was prevented by lowering the maximum tracking rate to 100 ppm. A maximum sensor rate of 140 ppm still allowed an adequate rate response during activity.

Aged↗
PubMed1989

Utility of rate histograms in programming and follow-up of a DDDR pacemaker.

Dual-chamber, rate-modulated pacing (DDDR) is the newest available pacing mode. To optimize programming of the rate response options for such a pacemaker, the physician must adopt an organized follow-up method, including use of some type of exercise testing to assess the programmed options of the pacemaker. Because the patient may achieve a substantial "training effect" after a rate-modulated pacing device has been implanted, the device probably should be reprogrammed at 1 month or after implantation. Programming and follow-up can be considerably facilitated by the use of pacemaker-generated "rate histograms," which conveniently display the distribution of rate responses to various levels of activity.

Adult↗
PubMed1989

Follow-up of an activity-sensing, rate-modulated pacing device, including transtelephonic exercise assessment.

Single-chamber rate-modulated (ventricular or atrial demand [VVIR or AAIR]) pacemakers are now an accepted and frequently used pacing modality. Although several sensor-driven pacemakers are currently under investigation, activity-sensing pacemakers have been used most frequently to date. We assessed our implantation and follow-up experience with 156 activity-sensing pacemakers. Analysis of the patient population revealed an age range of 6 to 91 years and a variety of indications for pacing, the most common being atrioventricular block. Specific programming techniques were adopted for assessing these pacemakers. Although several episodes of reprogramming may be necessary to identify the optimal sensor settings for an individual patient, once optimal programming has been achieved, the sensing characteristics seem to have long-term stability. An important part of our follow-up procedure involves transtelephonic exercise, which allows some degree of long-term assessment of the sensor. All but six patients with pacemakers programmed to the sensor-driven mode (VVIR or AAIR) had evidence of sensor-driven pacing during transtelephonic exercise. Thus, this adjunct seems helpful for follow-up of some rate-modulated pacemakers.

Adolescent↗
PubMed1989

P wave tracking above the maximum tracking rate in a DDDR pacemaker.

Dual-chamber, rate-modulated pacemakers have recently become available. These devices, whose rate response is determined by the combined input from the intrinsic atrial rate and the sensor-driven rate, have led to some unexpected upper rate behaviors. In the case presented, with the maximum sensor pacing rate at 150 ppm, multiple episodes of apparent P wave tracking occurred above the maximum P wave tracking rate of 100 ppm. This behavior is explained by P waves that inhibit sensor-driven atrial output; inhibition may result in variable maximum tracking rates that are equal to the current sensor-driven rate. This effect appears to have minimal physiological consequence. Its importance lies in its recognition as normal DDDR function so that searches for pacemaker malfunction will not be made.

Adult↗
PubMed1989

Electrocardiographic manifestations of a dual-chamber, rate-modulated (DDDR) pacemaker.

Dual-chamber, rate-modulated pacing (DDDR) has only recently been made available. During exercise, the pacemaker is capable of tracking not only the patient's intrinsic P wave but also the AV sequential sensor-indicated rate response, which depends on the programmed variables of the specific sensor in the DDDR pulse generator. Programmed options that affect the operation of a rate-modulated DDDR device are slope, threshold, reaction time, and recovery time. In addition, one is required to program a base or minimum pacing rate and a maximum tracking rate, as in any DDD device, as well as a maximum sensor rate. It is essential to know and understand all these programmed options if one is to correctly interpret electrocardiograms from a DDDR pacemaker. Interpreting the electrocardiograms also requires an understanding of the sensor-indicated rate of the pacemaker at any given level of exercise, which is determined by the options previously listed and the interaction between the sensor-indicated rate and the patient's intrinsic atrial and ventricular activity. This paper presents electrocardiograms typical of a new DDDR pacemaker undergoing clinical investigation.

Cardiac Pacing, Artificial↗
PubMed1989

Sensor-driven rate smoothing in a DDDR pacemaker.

DDD pacemakers may have large cycle-to-cycle variations in rate at the upper rate limit because of 2:1 block or Wenckebach-type block. Rate smoothing was introduced as an option to eliminate these large variations. Now, DDDR pacemakers can produce similar electrocardiographic displays through a different mechanism that uses an activity sensor. This is termed "sensor-driven rate smoothing" because it occurs only when the activity sensor is driving the pacemaker. In the case described, as the atrial rate exceeded the maximum tracking rate and reverted to Wenckebach-type block, the RR interval varied only from 600 msec to 680 msec (13.3% rate-smoothing value) because of sensor-driven pacing. Maximal sensor-driven rate smoothing requires optimal programming of the rate response indicators. This sensor-driven rate-smoothing effect is an electrocardiographic manifestation that will undoubtedly be seen more frequently as DDDR devices come into widespread clinical use.

Adult↗