Demand Pacemaker Research Articles

Transvenous demand Pacemaker Treatment for intermittent complete Heart Block in a Cat

Abstract A 13-year-old male neutered domestic shorthaired cat had repeated syncopal episodes over a 6 month period, which had variable duration and continued to increase in frequency. Intermittent ventricular asystole, due to complete heart block, and hyperthyroidism were documented. As the syncopal episodes did not respond to a 4-week medical treatment and symptoms became severe, a transvenous ventricular demand pacemaker system (VVIM) was implanted via the external jugular vein. The unipolar lead was tunneled subcutaneously and connected with the generator in a preformed ventral abdominal muscle pocket. During follow up of 18-months there were no recurrences of the syncopal episodes.

Three cases of pacemaker-mediated tachycardia

Pacemaker-mediated tachycardia (PMT) is a well-known complication of dual-chamber pacemaker with atrioventricular sensing and pacing (DDD) or atrial synchronous, ventricular demand pacemaker (VDD). PMT usually starts with sensing a retrograde P waves linked to ventricular extrasystole with retrograde ventriculoatrial conduction and forms reentrant or circus movement tachycardia with the pacemaker itself as an antegrade limb and the conducting tissue of the heart as a retrograde limb. Recently, a number of pacemaker manufactures have incorporated in their devices a variety of relatively complex algorithms to prevent PMT. Despite these measures, PMT may still occur because of inappropriate programming or unpredictable variations of ventri-culoatrial conduction. We report two cases of PMT in 78 year-old man and 60 year-old man who received DDD type pacemakers due to sick sinus syndrome, and a case of PMT in 69 year-old man who had suffered complete heart block and received a VDD type pacemaker. In these cases, we investigate symptoms, mechanism of PMT, programed parameters of pacemaker and treatments of PMT. (Korean Circulation J 2000;30(3):334-338) KEY WORD:Pacemaker-mediated tachycardia.

Surgical management of the patient with an implanted cardiac device: implications of electromagnetic interference.

To identify the sources of electromagnetic interference (EMI) that may alter the performance of implanted cardiac devices and develop strategies to minimize their effects on patient hemodynamic status. Since the development of the sensing demand pacemaker, EMI in the clinical setting has concerned physicians treating patients with such devices. Implanted cardiovertor defibrillators (ICDs) and ventricular assist devices (VADs) can also be affected by EMI. All known sources of interference to pacemakers, ICDs, and VADs were evaluated and preventative strategies were devised. All devices should be thoroughly evaluated before and after surgery to make sure that its function has not been permanently damaged or changed. If electrocautery is to be used, pacemakers should be placed in a triggered or asynchronous mode; ICDs should have arrhythmia detection suspended before surgery. If defibrillation is to be used, the current flow between the paddles should be kept as far away from and perpendicular to the lead system as possible. Both pacemakers and ICDs should be properly shielded if magnetic resonance imaging, positron emission tomography, or radiation therapy is to be used. The effect of EMI on VADs depends on the model. Magnetic resonance imaging adversely affects all VADs except the Abiomed VAD, and therefore its use should be avoided in this population of patients. The patient with an implanted cardiac device can safely undergo surgery as long as certain precautions are taken.

Influence of Cardiac Pacing Mode on Left Atrial Appendage Flow Velocity: Implication to Systemic Embolism During VVI Pacing.

Previous studies have shown that the incidence of thromboembolism is higher in patients with single-chamber ventricular demand (VVI) pacemakers than in patients with dual-chamber (DDD) pacemakers. However, data on left atrial appendage flow velocity in pacing patients are limited. To investigate the influence of the pacing mode on the left atrial appendage flow velocity, we studied 19 patients with permanent DDD pacemakers and measured the left atrial appendage flow velocity by transesophageal echocardiography at baseline (during DDD pacing) and after switching to VVI pacing. The indications for pacemaker implantation were second- and third-degree atrioventricular block (AVB group, n = 11) and sick sinus syndrome (SSS group, n = 8). Compared with the DDD pacing mode, there was a significant decrease in the left atrial appendage flow velocity during VVI pacing in both the SSS group (43 +/- 14 vs 23 +/- 7 cm/sec, P < 0.05) and the AVB group (59 +/- 18 vs 41 +/- 18 cm/sec, P < 0.05). In eight patients with persistent retrograde ventriculoatrial conduction during VVI pacing, the left atrial appendage flow velocity was markedly decreased (from 43 +/- 16 to 25 +/- 9 cm/sec, P < 0.05). In five (63%) of the eight patients, left atrial appendage flow velocity was less than 25 cm/sec. A reduction in left atrial appendage flow velocity when switching from DDD to VVI pacing may account for an increased risk of thrombus formation in the left atrial appendage (an increased thromboembolic risk in patients in sinus rhythm with VVI pacemakers).

Recombinant Tissue Plasminogen Activator Therapy for Pacemaker-Induced Thrombosis

A 50-year-old male who developed subclavian vein thrombosis following insertion of a demand pacemaker was treated with a short period of high-dose recombinant tissue plasminogen activator (100 mg over 3 hours). Total thrombolysis was achieved without complications.

Die Bedeutung des Langzeit-EKG für die Schrittmacherambulanz

Reports from the literature show that Holter monitoring is more sensitive in detecting pacemaker dysfunction than 12-lead ECG. Holter monitoring is, therefore, an additional useful tool in the pacemaker follow-up clinic. Data from the literature show that pacemaker dysfunctions are more frequent than patients‘ history and common standard techniques of the pacemaker follow-up clinic may suggest. All patients, therefore, should undergo Holter monitoring during follow-up. The following indications for Holter monitoring in pacemaker patients are commonly accepted: detection of pacemaker dysfunctions or spontaneous arrhythmias in symptomatic patients, surveillance of asymptomatic patients at least after implantation of complex multiprogrammable pacemakers, assessment of spontaneous heart rate in pacemaker patients, and sensor function in rate adaptive pacemakers. In patients with dual-chamber pacemakers Holter monitoring is useful in detecting atrial arrhythmias, especially atrial fibrillation affecting adequate pacemaker function, and pacemaker-mediated tachycardias. Diagnostic sensitivity of Holter monitoring in detecting transient pacemaker dysfunctions can be further improved by computer-aided analysis, which is still limited to the evaluation of ventricular inhibited demand pacemakers. In many cases only visual analysis is possible. The prognostic value of transient pacemaker dysfunctions detected by Holter monitoring should be clarified by long-term follow-up studies.

Exercise intolerance in Kearns-Sayre syndrome

Exercise intolerance is a common finding in mitochondrial diseases, including Kearns-Sayre syndrome (KSS), characterised by progressive external ophthalmoplegia, cardiac conduction defects and atypical pigmentary degeneration of the retina. Exercise studies were performed in a 32 year old woman with KSS who had received an atrio-ventricular sequential pacemaker because of continuing breathlessness, having presented with complete heart block requiring a fixed rate demand pacemaker 6 years earlier. Minute ventilation, oxygen consumption, and carbon dioxide production were measured at different workloads on 3 consecutive days by collecting expired air. Compared to controls, after exercise at a subanaerobic workload, heart rate and ventilation were exaggerated relative to both oxygen consumption and carbon dioxide production. The findings are consistent with the hypothesis that, in mitochondrial disorders, impaired oxidative phosphorylation leads to uncoupling of cardiac ouput and ventilation relative to muscle metabolic rate.

Relation Between Postpacing T Wave Changes and Myocardial Scintigraphic Characteristics in Patients with Ventricular Demand Pacemaker

The aim of this study was to elucidate the cause of T wave changes after ventricular pacing using thallium 201 single photon emission computed tomography (Tl-SPECT). Tl-SPECT was performed in 20 patients with sick sinus syndrome who had negative T wave after ventricular pacing and had had a ventricular demand pacemaker (VVI) implanted. Patients who have stenotic coronary arteries were excluded from the study. From the analysis of Tl-SPECT, extent score was calculated as the ischemic region. Data in patients with SSS were compared with those in 20 normal controls (NC). Thallium perfusion defects in patients with VVI were observed and distributed mainly in apex and inferior regions on the polar map. The extent score in patients with VVI was significantly higher than that in NC (56.4 +/- 21.6% vs 3.2 +/- 6.4%, P < 0.01). The washout rate of thallium 201 in the defect area was significantly lower in patients with VVI than in NC (27.4 +/- 10.2% vs 46.8 +/- 12.3%, P < 0.01). These results suggest that T wave changes after ventricular pacing are closely related to myocardial ischemia.

Permanent cardiac pacing and thromboembolic risk in elderly patients.

In patients undergoing permanent cardiac pacing, the maintenance of atrial contractility is important to ensure adequate ventricular filling and to guarantee an optimal ventricular ejection capacity. The appropriate pacing mode, assuring a suitable mechanical atrioventricular coupling, prevents the onset of atrial fibrillation and contributes to reduction of the risk of subsequent systemic and pulmonary thromboembolic episodes. We examined 461 patients (266 males and 195 females, aged between 52 and 97 years, average age 76.5 +/- 18) paced for conduction disturbances of various degrees and etiology. Of them, 323 patients received ventricular demand pacemaker (VVI group, average age 77.9 years); 138 underwent dual chamber pacing (DCP group, average age 75.2 years), 117 of the latter received universal demand pacing (DDD) and 21 atrial synchronous ventricular demand pacing (VDD). The patients were subsequently divided into two age-groups: Group A (</= 75 years, 174 patients), and Group B (>/= 75 years, 287 patients). According to pacing mode and successive development of stable atrial fibrillation (AF), we analysed the occurrence of systemic and/or pulmonary thromboembolic episodes and the incidence of fatal events. During our study, performed from January 1986 to August 1993, 70 embolic episodes were observed in the VVI group and six in the DCP group. Eighty-four patients with VVI units developed AF during follow-up, compared with only five patients in the DCP group. Our data indicate that VVI patients have a higher incidence of AF, embolic complications and cerebrovascular mortality, in comparison with the DCP group. VVI pacing should be avoided, especially in older patients, when atrial rhythmical activity is present.

Extracorporeal Shock Wave Lithotripsy in Patient with Cardiac Pacemaker in an Abdominal Location: Case Report and Review of the Literature

A 75-year-old man with complete heart block and a ventricular demand pacemaker with the generator in a left upper-quadrant subcutaneous pouch underwent extracorporeal shock wave lithotripsy (SWL) for a 2-cm proximal right ureteral calculus, receiving 2000 shocks at 24 kV. There was no damage or malfunction of the pacemaker, and the Dornier HM3 lithotripter had no difficulty sensing all paced ventricular complexes. The patient had excellent fragmentation of his calculus. Extracorporeal shock wave lithotripsy may be performed safely on patients with pacemakers directly in the path of the shock waves at maximal kilovoltage when appropriate peri-SWL guidelines are followed. Specifically, the treatment should be approved by a cardiologist knowledgeable about the patient and the pacemaker, and a cardiologist should be nearby with the equipment necessary to deal with any problems. Dual-chamber pacemakers should be reprogrammed to the single-chamber mode, and single-chamber rate-responsive devices should have the activity mode programmed off. Patients with the latter type of pacemaker implanted in the abdomen should not have SWL if the device will be close to F2.

Benefits of the advances in cardiac pacemaker technology.

Pacemaker technology has expanded rapidly in the last thirty years. Each phase of development has been marked by both improvements in clinical benefit and disadvantageous interactions of physiology and technology. Each phase of development has led to smaller, more reliable devices with greater programmability. Advances in generator technology and battery design have increased longevity of devices. The first devices used asynchronous pacing which had a significant effect in reducing the mortality of surgically induced complete heart block. Ventricular demand pacemakers overcame the problems of asynchronous competitive pacing, but exposed the pacemaker syndrome. Atrioventricular sequential pacing restored atrioventricular synchrony, resulting in hemodynamic improvement, but created the phenomenon of pacemaker-mediated tachycardia. Alternative dual chamber modes and algorithms have largely resolved this. Adaptive-rate devices have been of benefit to patients with chronotropic incompetence, and are now incorporating an increasing variety of biosensors. Almost all the problems of pacing have been overcome, but the increasing complexity of pacemaker technology is now a major limitation to its proper use.

"Subclinical" pacemaker syndrome: a randomised study of symptom free patients with ventricular demand (VVI) pacemakers upgraded to dual chamber devices.

To determine whether symptom free patients with single chamber pacemakers benefit from dual chamber pacing. A randomised double blind crossover comparison of ventricular demand (VVI), dual chamber demand (DDI), and dual chamber universal (DDD) modes after upgrading from a VVI device. Cardiology outpatient department. Sixteen patients aged 41-84 years who were symptom free during VVI mode pacing for three or more years. Pacemaker upgrade during routine generator change. Change in subjective (general health perception, symptoms) and objective (clinical assessment, treadmill exercise, and radiological and echocardiographic indices) results between pacing modes before and after upgrading. 75% preferred DDD, 68% found VVI least acceptable with 12% expressing no preference. Perceived general well-being and exercise capacity (p less than 0.01) and treadmill times (p less than 0.05) were improved in DDD mode but VVI and DDI modes were similar. Clinical, echocardiographic, radiological, and electrophysiological indices confirmed the absence of overt pacemaker syndrome, although mitral and tricuspid regurgitation was greatest in VVI mode (p less than 0.01). Most patients who were satisfied with long term pacing in VVI mode benefited from upgrading to DDD mode pacing suggesting the existence of "subclinical" pacemaker syndrome in up to 75% of such patients. The DDI mode offered little subjective or objective benefit over VVI mode in this population and should be reserved for patients with paroxysmal atrial arrhythmias. VVI mode pacing should be used only for patients with very intermittent symptomatic bradycardia or atrial fibrillation with a good chronotropic response during exercise.

Myopotential inhibition of unipolar demand pacemakers: utility of provocative manoeuvres in assessment and management

Fifty patients with permanent unipolar pacemakers (48 multiprogrammable, 2 non programmable) with protective insulating sheath placed against the muscular side of the pacemaker pocket were studied to determine the occurrence of inhibition of pacing by sensing of the myopotentials. All the patients were subjected to a combination of different provocative manoeuvres at their nominal R wave sensitivity settings. Myopotential inhibition was exhibited in 35 (70%) patients. Only 3 patients however had reported symptoms suggesting loss of pacing. The most useful provocative manoeuvre was shoulder flexion with adduction against resistance (94.3% positivity). Appropriate sensitivity adjustments resulted in amelioration of the problem in 86% of the patients while still retaining R wave sensing. Myopotential interference continues to be a frequently observed problem even in the present generation of unipolar pacemakers. Provocative tests and appropriate reprogramming should be done in all such patients as a routine.

Disturbed secretion of atrial natriuretic peptide in patients with persistent atrial standstill: Endocrinologic silence

Persistent atrial standstill is a very rare pathophysiologic condition whose diagnosis is established when both electrical and mechanical silence of the atria are confirmed. To test the hypothesis that secretion of atrial natriuretic peptide is disturbed in patients with persistent atrial standstill, the response of atrial natriuretic peptide secretion and other neurohormonal factors during exercise was investigated in three patients with a rate-responsive ventricular demand (VVI) pacemaker implanted for confirmed persistent atrial standstill. The results were compared with those observed in eight normal subjects and patients with a rate-responsive VVI (Group A) or atrial demand (AAI) (Group B) pacemaker implanted for confirmed sick sinus syndrome.Patients in Group A displayed significant elevation of alpha-human atrial natriuretic peptide secretion both before and during exercise (122.5 ± 14.8 and 207.5 ± 8.3 pg/ml, respectively) compared with those in Group B (55 ± 14.1 and 116.4 ± 51.5 pg/ml, respectively) and the normal subjects (18.9 ± 9.8 and 30.8 ± 19.2 pg/ml, respectively). This indicated development of a nonphysiologic increase in atrial volume or pressure overload, or both, in rate-responsive VVI pacing because of lack of atrioventricular synchrony. However, patients with persistent atrial standstill had undetectable (<10 pg/ml) or almost undetectable secretion of atrial natriuretic peptide as well as lower levels of cyclic guanosine monophosphate in the circulation both before and during exercise. Changes in plasma catecholamines during exercise were similar in patients with persistent atrial standstill compared with the other groups.This study indicates that “endocrinologic silence” accompanies electrical and mechanical silence of the atria, which may constitute a third diagnostic clue to persistent atrial standstill.

The Natural Course of Cardiac Conduction Disturbances in Myotonic Dystrophy

In this study we noninvasively followed for a mean period of 46 months 21 patients with different grades of myotonic dystrophy to evaluate the course of the involvement of the cardiac conducting system. Six patients (28.6%), 1 affected by a mild and 5 by a severe form of the neuromuscular disorder, showed appearance or deterioration of conduction disturbances suggesting a serious derangement of the specialized tissue; in 3 of them a permanent demand pacemaker was implanted. Conduction defects are the most frequent cardiac manifestations in myotonic dystrophy and become worse with time, mainly in patients with higher degrees of the disease. Furthermore, first-degree atrioventricular block may represent an early sign of developing of more advanced conduction defects.

Stability of Pacing Threshold, Impedance, and R Wave Amplitude at Rest and During Exercise

The pacing threshold of the human heart may be altered by physiological factors such as physical exercise. These changes may influence the individual programming of a pacemaker, since pacemakers can be programmed at pulse amplitudes of 2.5 volts and less. We investigated 22 patients with a multiprogrammable ventricular demand pacemaker 3 months after implantation; 16 patients had received a steroid-eluting lead and six patients had an Elgiloy lead. Parameters measured at rest and immediately after exercise were: Voltage threshold at pulse durations between 0.05 and 0.6 ms, impedance, R wave amplitude and energy consumption for the pacing threshold at 0.5 ms pulse duration. All patients performed a symptom limited supine bicycle exercise test. None of the investigated parameters showed a significant difference between rest and exercise, neither for the steroid eluting lead nor for the Elgiloy lead. The data suggest that the individual programming of a pacemaker adapted to the measurements at rest is also reliable and safe during exercise.

Rate‐Adaptive Cardiac Pacing in Children Using a Minute Ventilation Biosensor

Chronotropic integrity is required for a normal cardiac output response to exercise. We evaluated a rate-adaptive ventricular demand pacemaker (Telectronics, META-MV) which uses minute ventilation as the sensed physiological variable for adjusting pacing rate, in seven young patients with a mean age of 11.4 years. All patients had clinically significant bradycardia related to complete heart block (n = 4) or sinus node dysfunction (n = 3). For the entire group, paced heart rates increased from 70 +/- 10 beats/min to 151 +/- 19 beats/min with exercise testing. The onset of rate adaptation took less than 30 seconds. Changes in paced rate were linearly related to workload, VO2 (5.9 to 20.7 mL/min/kg) and minute ventilation (8-65 L/min). The decline in pacing rate after exercise was related directly to the gradual decrease in minute ventilation and VO2. Our data show that minute ventilation closely and accurately reflects the metabolic demands of varying workloads in children and can be used to achieve physiological, rate-adaptive pacing.

The nuclear pacemaker: Is renewed interest warranted?

From 1973 through 1987, 155 radioisotope-powered “nuclear” pacemakers were implanted in 132 patients at the Newark Beth Israel Medical Center. The longevity of the first 15 devices, all of which were fixed-rate (VOO) pacemakers, was significantly better than that of 15 lithium-chemistry demand (VVI) pacemakers used as control devices (p = 0.0002). Of the entire cohort of 155 nuclear pacemakers, 136 were VVI devices and 19 were VOO units. The patients with VOO pacemakers needed reoperations more often than did those with VVI pacemakers, chiefly for mode change (p < 0.001). Power-source failure was observed in only 1 case, but 47 nuclear pacemakers were removed for other reasons, including component malfunction (15 units), mode change (12 units), high pacing thresholds (8 units) and lead or connector problems (5 units). The actuarial survival at 15 years was 99% for power sources and 82% for the entire pacing systems (pulse generators plus leads). The frequency of malignancy was similar to that of the population at large and primary tumor sites were randomly distributed. Deaths most commonly were due to cardiac causes (68%). Thus, nuclear pacemakers are safe and reliable and their greater initial cost appears to be offset by their longevity and the resulting decrease in the frequency of reoperations. It is reasonable to suggest that further use be made of long-lasting nuclear power sources for modern pacemakers and other implantable rhythm-management devices.

Pacemaker Syndrome Evaluated by Cardiopulmonary Exercise Testing

Two patients who presented with dyspnea on effort, persisting after insertion of a fixed rate ventricular demand pacemaker (VVI) for sick sinus syndrome, were evaluated by cardiopulmonary exercise testing. During VVI pacing a heightened ventilatory response to exercise and a fluctuation of ventilation occurred. The high ventilatory equivalent for CO2 throughout exercise with VVI pacing suggests that the patients had ventilation-perfusion mismatching due to an increase in the pulmonary capillary wedge pressure caused by 1:1 ventriculoatrial conduction. Rate responsive ventricular (VVIR) pacing associated with intact 1:1 ventriculoatrial conduction exaggerated the exertional dyspnea, while rate responsive atrial (AAIR) pacing improved the ventilatory response to exercise. We suggest that a heightened ventilatory response to exercise due to ventilation-perfusion mismatching may be an important factor causing the pacemaker syndrome, and that cardiopulmonary exercise testing is useful in identifying the exercise-induced symptoms with ventricular pacing.

Choosing the pacemaker; a rational approach to the use of modern pacemaker technology

Sophisticated pacemakers now afford greater benefit than only relief of syncope for patients with symptomatic bradyarrhythmia. For clinical reasons it is inappropriate to implant ventricular demand (VVI) pacemakers in every patient, but for both clinical and economic reasons it is also undesirable to use dual-lead or rate-responsive systems indiscriminately. However, the published guidelines for pacemaker choice and investigation are inadequate. We have analysed the clinical assessment and the investigations required in a series of 150 patients with various electrophysiological disorders, considered consecutively for pacemaker implantation using an algorithm to assist decisions. Holter electrocardiography in 77.3%, exercise testing--formal (in 9.3%) or informal (during Holter electrocardiography), electrophysiology study (EPS)--full in 15.3% and partial in 29.3%, and trial of pacing (10.7%) were all used to characterize dysfunction and to define appropriate pacing mode. 142 patients were paced--57.0% with single lead modes (12.7%) AAI, 44.3% VVI) and 43.0% dual-lead (2.8% DVI, 23.9% VDD or VAT, 16.2% DDD). Three patients received rate-responsive systems (VVIR) which, if available, would have been used in nine; four would have been suitable for AAIR and four for dual-lead responsive pacing (DVIR, DDIR or DDDR). We offer a rational approach based on published data for investigation and pacemaker choice in the management of patients with bradyarrhythmia.