PubMed Health⌕ Search

Biomedical subjects

J W Harthorne

Publications and source records attributed to J W Harthorne.

At least 19 recordsLinked to original sources
PubMed1995

Ventricular pacing induced ventricular tachycardia in patients with implantable cardioverter defibrillators.

Appropriately timed noncompetitive ventricular pacing potentially may initiate ventricular tachycardia in patients prone to these arrhythmias. The combination of bradycardia pacing and stored electrograms in a currently available cardioverter defibrillator provides an opportunity to evaluate the occurrence of such pacing induced ventricular tachycardia. During a surveillance period of 18.7 +/- 11.4 months, stored electrograms documented 302 episodes of ventricular tachycardia in 77 patients. Five patients (6.5%) demonstrated 25 episodes (1-16 per patient) of ventricular tachycardia that were immediately preceded by an appropriately paced ventricular beat (8.3% of all episodes of ventricular tachycardia). All five patients had prior myocardial infarctions and a history of monomorphic ventricular tachycardia occurring both spontaneously and in response to programmed electrical stimulation. Antitachycardia pacing terminated pacing induced ventricular tachycardia in 22 episodes; in one episode antitachycardia pacing accelerated ventricular tachycardia. In two cases shock therapy was aborted for nonsustained ventricular tachycardia. We conclude that, in selected nonsustained ventricular tachycardia. We conclude that, in selected postinfarction patients with recurrent sustained monomorphic ventricular tachycardia treated with implantable cardioverter defibrillators, appropriately timed ventricular pacing may induce ventricular tachycardia.

Aged↗
PubMed1995

Subclavian crush syndrome complicating transvenous cardioverter defibrillator systems.

UNLABELLED: Subclavian crush syndrome, described with pacemaker leads implanted via subclavian puncture, may occur when conductor fractures and insulation breaches develop by compression of a lead between the first rib and clavicle. We reviewed our experience in 164 patients who underwent intended implantation of transvenous defibrillator systems to determine the clinical relevance of subclavian crush syndrome in defibrillator patients. Venous access was obtained via subclavian puncture in 114 patients (70%) and via cephalic cut-down in 50 patients (30%). Nonthoracotomy lead systems, with or without subcutaneous patch, were successfully implanted in 131 of 164 patients (79.9%). Thoracotomy was required in 32 patients (19.5%) and subxiphoid patch in 1 patient (0.6%). Over a mean of 12.9 months (range 1-62 months), 3 patients (1.8%) required revision of the rate sensing lead/coil or superior vena cava coil after development of lead compression fractures in the region of the clavicle and first rib. In all 3 patients the leads had been implanted via subclavian puncture (2.6% of patients in whom the subclavian technique was utilized). Two patients presented with spurious shocks. One patient was asymptomatic. CONCLUSIONS: When venous access is obtained via subclavian puncture, subclavian crush syndrome may develop in patients with transvenous defibrillator systems. Patients may be asymptomatic and lead fractures may go unrecognized. When implanting transvenous defibrillator systems, strong consideration should be given to obtaining venous access primarily via the cephalic cut-down technique.

Aged↗
PubMed1994

Submammary pacemaker implantation: a unique tunneling technique.

Submammary pacemaker implantation offers women a cosmetically acceptable alternative to the standard pectoral implant. We present a novel method of submammary implantation performed on ten women aged 13-54 years. The lead electrodes are tunneled from the infraclavicular to the inframammary incision using a long needle, guidewire, and introducers/dilators in a manner analogous to the retained guidewire technique used for standard lead insertion. The procedure can generally be performed under local anesthesia. All patients tolerated the procedure well without acute complications. Over 2- to 23-month follow-up, there were no lead dislodgments. No patients developed mastitis or incisional complications, and all have been extremely satisfied with the cosmetic results. With proper technique, submammary pacemaker implantation can be performed under local anesthesia with minimal patient discomfort and optimal cosmesis.

Adolescent↗
PubMed1994

A comparison of VVIR and DDDR pacing following cardiac transplantation.

UNLABELLED: We compared the clinical course of patients paced in VVIR versus DDDR mode to determine the most appropriate method of pacing following cardiac transplantation. Pacemaker implantation was required in 9 of 90 orthotopic cardiac transplants (10%). Indications included sinus bradycardia or sinus arrest (8 patients) and AV node dysfunction (1 patient). VVIR pacemakers were implanted in four patients and DDDR in five patients. DDDR patients: The mean P wave was 1.7 mV and the mean atrial stimulation threshold was 0.8 V (at 0.5 msec). During follow-up of 20 months, two atrial lead complications developed (29% of leads in 33% of patients). No lead complications were directly related to endomyocardial biopsy. VVIR patients: All four patients developed VA conduction with mean VA time 180 msec (160-240 msec). Two patients developed pacemaker syndrome. CONCLUSIONS: VA conduction and pacemaker syndrome may develop in cardiac transplant recipients paced in the VVIR mode. Dual chamber pacing is technically feasible and preferable following cardiac transplantation.

Adult↗
PubMed1988

Clinical and hemodynamic comparison of VVI versus DDD pacing in patients with DDD pacemakers.

To identify better those subgroups of pacemaker recipients who will benefit from dual chamber pacing, 19 patients with DDD pacemakers that were physiologically paced were entered into a blinded, randomized protocol comparing long-term VVI versus DDD pacing. Patients were evaluated in each of the pacing modes for exercise performance, cardiac chamber size, cardiac output, functional status and health perception. Eight patients (42%) insisted on early crossover, from VVI to DDD pacing, after only 1.8 +/- 1.4 weeks because of symptoms consistent with pacemaker syndrome. Overall, 12 patients preferred DDD pacing and no patient preferred VVI pacing (p = 0.001). Percent fractional shortening (30 +/- 8 vs 24 +/- 6%, p = 0.009) and cardiac output (6.3 +/- 2.6 vs 4.4 +/- 2.2 liters/min, p = 0.0001) where significantly greater in the DDD mode. Exercise duration was greater during DDD compared with VVI pacing (11.3 +/- 3.7 vs 10.1 +/- 3.7 minutes, p = 0.006). However, it was only in the crossover subgroup that DDD pacing resulted in significant improvement in exercise performance and health perception compared with VVI pacing. This subgroup of patients was characterized by an intrinsic sinus rate of less than 60 beats/min (4/8 vs 0/11, p = 0.006), ventriculoatrial (VA) conduction (4/8 vs 1/11, p = 0.048), greater increase in exercise peak systolic blood pressure from VVI to DDD mode (21 +/- 12 vs 4 +/- 13 mm Hg, p = 0.02) and greater improvement in exercise capacity from VVI to DDD pacing (2.2 +/- 1.2 vs 0.6 +/- 1.4 minutes, p = 0.03) compared with the other 11 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

The automatic implantable cardioverter-defibrillator: efficacy, complications and survival in patients with malignant ventricular arrhythmias.

Ninety-four patients underwent surgery for automatic implantable cardioverter-defibrillator implantation. Ninety patients were discharged from the hospital with the device and were followed up for a mean period of 17 +/- 10 months. Forty-six patients experienced at least one discharge of the device under circumstances consistent with a malignant ventricular arrhythmia. One sudden death occurred. Complications included perioperative death (3 patients), post-operative ventricular tachycardia (12 patients) and atrial fibrillation (8 patients), perioperative myocardial infarction (1 patient) and device discharges for sinus tachycardia and supraventricular arrhythmias (17 patients). Six and 12 month survival rates by life table analysis were 98.7 and 95.4%, respectively. Thus, the automatic implantable cardioverter-defibrillator is a highly effective and relatively low risk treatment modality for patients with refractory life-threatening ventricular arrhythmias.

Adolescent↗
PubMed1988

Performance of implantable cardiac rhythm management devices.

Our data represent use, follow-up, and management decisions from eight independently functioning centers and most importantly, actuarial survival of ICRMD's that have been implanted for a sufficient time period to allow assessment of time versus failure. General patterns of possible target durations for adequate performance for present or future generations of similar clinical devices may be suggested by the data that we have presented. However, it would be inappropriate to conclude from these data that any presently implanted ICRMD would have a particular functional reliability. Furthermore, these data only summarized device hardware performance and cannot and must not be used to determine either short-term or long-term individual patient status, management, or outcome.

Electric Countershock↗
PubMed1987

Performance of implantable cardiac rhythm management devices.

Our data represent use, follow-up, and management decisions from seven independently functioning centers and most importantly, actuarial survival of ICRMDs that have been implanted for sufficient time period to allow assessment of time versus failure. General patterns of possible target durations for adequate performance for present or future generations of similar clinical devices may be suggested by the data that we have presented. However, it would be inappropriate to conclude from these data that any presently implanted ICRMD would have a particular functional reliability. These data, furthermore, only summarized device hardware performance and cannot and must not be used to determine either short-term or long-term individual patient status, management, or outcome.

Actuarial Analysis↗
PubMed1986

Single-chamber and dual-chamber cardiac pacemakers. A formal cost comparison.

Dual-chamber pacemakers, more sophisticated and costly than single-chamber pacemakers, are being used with increasing frequency, often with unclear indications. Proponents of dual-chamber devices have focused on initial differences in cost without considering additional induced costs. We examined the incremental cost of dual-versus single-chamber pacemakers over the expected lifetime of a pacemaker recipient. In addition to initial costs, we included the costs of pacemaker malfunction, reimplantation, generator replacement, and follow-up. Expected differences in cumulative costs per patient were calculated over a 12-year period. Dual-chamber pacing is $2500 more costly at implantation. The difference in cumulative cost increases to $5100 by year 12, reflecting shorter functional life for dual-chamber pacemaker generators and increased cost of follow-up. The incremental cost of dual-chamber pacemaking is neither short-term nor trivial. Dual-chamber pacemakers should be reserved for those who clearly benefit from its advanced technology.

Costs and Cost Analysis↗
PubMed1984

Doppler ultrasound measurement of cardiac output in patients with physiologic pacemakers. Effects of left ventricular function and retrograde ventriculoatrial conduction.

Dual-chamber cardiac pacing (DDD) offers obvious theoretical advantages over traditional ventricular demand (VVI) pacing. Nevertheless, no widely agreed upon criteria exist for the selection of patients for physiologic DDD pacemakers compared with the simpler VVI systems. Accordingly, a non-invasive method for measuring cardiac output (Doppler ultrasound) was used to identify candidates for pacing who would derive the greatest hemodynamic benefit from DDD vs VVI pacing. Among 29 patients studied at rest during VVI-mode pacing, the average cardiac output by Doppler ultrasound was 4.3 +/- 0.3 liters/min (mean +/- standard error of the mean). In the DDD mode, the average cardiac output was 5.0 +/- 0.3 liters/min (p less than 0.001). Baseline left ventricular ejection fraction did not identify a group that improved more with DDD pacing. Patients who showed either retrograde ventriculoatrial conduction or described symptoms consistent with the "pacemaker syndrome" during VVI pacing, however, showed greater increases in cardiac output during DDD pacing. In these patients, the mean improvement in cardiac output was 30.4 +/- 8.6% with DDD vs VVI pacing, as opposed to an average increase of only 14.4 +/- 3.4% in the remaining 20 patients (p = 0.02). Thus, Doppler ultrasound can be used to quantitate the change in cardiac output at rest that occurs with DDD vs VVI pacing. The change is independent of the level of left ventricular function but is substantially higher when there is evidence of ventriculoatrial conduction or the pacemaker syndrome.

Adult↗
PubMed1984

Pacemaker leads.

Present day pacemaker leads are far superior in every respect to those of the past. Modification of fixation characteristics has reduced displacement rates to 1% or less in most centers. Fracture of multifilar leads is a rarity. Biodegradation of polyurethane insulation appears to be an isolated problem specific to individual lead models and may be related to physical stresses incurred during manufacture or lead insertion. Recent evidence has incriminated an interaction of polyurethane with silver which arises from the drawn braised strand conductor substrate of those leads in which this problem has been noted. This may explain why the problem has been restricted to specific lead models of one manufacturer to date. Lack of uniformity of lead terminal size between manufacturers and even within the same manufacturer's product line continues to baffle this observer. Although past problems of lead displacement have been markedly reduced, the difficulty of removing chronic leads which have become septic appears to have worsened. Modification of existing leads to ensure that the interface between electrode tip and proximal shaft is unidiametric is essential.

Cardiac Pacing, Artificial↗
PubMed1984

Pacemaker-mediated tachycardias: an unresolved problem.

The advent of dual chamber pacing systems that restore atrioventricular synchrony and allow rate variability in response to physiologic stress has provided a major advance in pacing therapy. Undesirable pacemaker-mediated tachycardias may arise when the atrial sensing amplifier of a VDD or DDD device detects a retrogradely conducted P-wave, ectopic atrial tachycardia, myopectoral contractions, or environmental electromagnetic interference. The rate of the resultant tachycardia is determined by the programmed upper tracking rate of the pacemaker. Although seldom life-threatening, troublesome myocardial ischemia may ensue in patients with coronary artery disease. In most instances, the incidence and rate of pacemaker-mediated tachycardias may be minimized by judicious programming.

Cardiac Pacing, Artificial↗
PubMed1984

Physiological pacemakers.

It has long been possible to prevent death from bradycardia by using single-chamber ventricular pacemakers. Important advances in dual-chamber pacemaker technology now make physiological control of cardiac output during pacing almost a reality. These pacemakers have properly timed atrial contraction and rate variability and have significant hemodynamic advantages over ventricular pacemakers. The pathophysiology of bradycardia and the current status of physiological pacemakers are reviewed in this article.

Bradycardia↗
PubMed1983

Effect of ventricular pacing on left ventricular function assessed by radionuclide angiography.

Radionuclide angiography was used to evaluate left ventricular contraction on and off ventricular pacing in 35 patients. Twenty patients had permanent rate-adjustable ventricular demand pacemakers whose rate could be programmed to below an underlying sinus rhythm. In these patients there was no difference in left ventricular ejection fraction on and off pacing whether or not heart failure was present (n = 7) or whether or not ventriculoatrial conduction (n = 10) developed during pacing. Eight of the 20 patients also underwent supine bicycle exercise, and rest and exercise ejection fraction values were not significantly different at a similar heart rate and workload when on and off pacing were compared. During pacing, there appeared to be abnormal motion in septal, apical, and inferior walls. In addition, dysynchrony developed, consisting of early right ventricular and anterobasal and posterobasal left ventricular motion with subsequent contraction of the apex. Conversion to atrioventricular pacing produced a clinical improvement in all seven patients with heart failure and reduced ejection fraction and also in one of the remaining 13 patients without heart failure. Fifteen other patients were studied early after cardiac surgery. Temporary ventricular epicardial pacing resulted in a significant increase in right and left atrial pressure and a significant reduction in stroke volume, end-diastolic volume, and end-systolic volume with no significant change in ejection fraction. Conversion from sinus rhythm to ventricular pacing produces a deterioration in cardiac performance and severe regional left ventricular wall motion abnormalities, but no significant change in ejection fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗