Demand Pacemaker Research Articles

Management of Spinal Cord Stimulators in Patients with Cardiac Pacemakers

We report a case of spinal cord stimulation (neurostimulation) as treatment for angina pectoris pain in a patient with a demand pacemaker. The precautions to avoid inhibition of the demand pacemaker by the neurostimulator are discussed.

Immunoblastic lymphoma presenting with syncope due to sinoatrial node disease

A 68 year old man presented with syncope associated with episodes of sinus arrest. He responded to insertion of a demand pacemaker. During investigation he was noted to have generalized lymphadenopathy and biopsy revealed that he had an immunoblastic lymphoma. Before further assessment could be made, he developed rapid atrial fibrillation, resistant to several anti-arrhythmic agents and died several days after admission. At autopsy a nodular plaque of lymphoma was found to overly the sinoatrial node which was markedly fibrosed with evidence of lymphomatous infiltration of the surrounding microvasculature.

Intraoperative Use of Dual-Chamber Demand Pacemakers for Open Heart Operations

The availability of external atrioventricular sequential pacemakers has improved the management of patients with sinus bradycardia, junctional rhythm, and atrioventricular block. However, these pacemakers are of less value in patients with postoperative heart block and accelerated atrial rhythms. The temporary use of a modified explanted dual-chamber demand pacemaker may counteract that problem by providing atrially triggered, P-wave-synchronous ventricular pacing. We report 2 patients in whom the temporary use of the dual-chamber demand pacemaker greatly facilitated weaning from cardiopulmonary bypass after coronary artery bypass grafting.

Chronobiological study of heart rate and ventricular extrasystole in the course of acute myocardial infarction (AMI)

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.

Pacemaker-induced ventricular tachycardia in normally functioning ventricular demand pacemakers

Pacemaker-induced ventricular tachycardia (VT) or fibrillation is a rare event. 1–5 These episodes were mostly found to be initiated by stimulation during the vulnerable period of the myocardium in asynchronous pacemakers (WO), 1–3 in malfunctioning ventricular demand pacemakers (VVI), in an atrioventricular sequential demand pacemaker (DVI) 4 and in an atrial synchronous ventricular inhibited pacemaker (VDD). Pacemaker-induced VT has also been reported during the acute phase of myocardial infarction, during the first 2 days after implantation of the electrode or during hypoxia or electrolyte imbalance. To the best of our knowledge, initiation of VT by a normally functioning pacemaker in the setting of chronic stable coronary heart disease has not yet been described.

Combined automatic implantable cardioverter-defibrillator and pacemaker systems: Implantation techniques and follow-up

The automatic implantable cardioverter-defibrillator (AICD) effectively prevents death due to ventricular tachycardia or ventricular fibrillation. Some patients who need an AICD also require cardiac pacing to treat symptomatic bradycardia, bradycardia after defibrillation, or to provide a rate floor to reduce the frequency of bradycardia-related ventricular arrhythmias. Some patients also can benefit from antitachycardia pacing. A mapping technique to implant a pacemaker and AICD sensing leads is presented. For patients with a pacemaker who later need an AICD, the left ventricle is mapped with use of the AICD rate-sensing electrodes to identify a site at which the minimal pacemaker stimulus and maximal ventricular electrogram amplitudes are recorded. An external cardioverter-defibrillator that has amplifiers similar to those in the AICD is used to monitor the rate-sensing electrogram. For patients with an implanted AICD, pacemaker implantation is undertaken by mapping the right ventricle with the pacemaker lead while the AICD is in standby mode; the AICD beep monitor is then used to determine a site where pacemaker stimulus detection by the AICD does not occur.Eight patients underwent implantation of a combined AICD-pacemaker system (four ventricular antitachycardia pacemakers, three ventricular demand pacemakers and one atrial demand pacemaker). Neither inhibition of AICD arrhythmia detection nor double counting occurred. Satisfactory AICD-pacemaker function was shown in all patients postoperatively, and no pacemaker malfunction was observed. Thus, with currently available technology, a combined AICD-pacemaker system can be implanted with satisfactory function of both devices and without adverse device-device interactions.

External cardiac programmed stimulation for noninvasive termination of sustained supraventricular and ventricular tachycardia

To examine the feasibility of using a noninvasive temporary pacemaker for termination of well-tolerated supraventricular (SVT) and ventricular tachycardia (VT), a standard external demand pacemaker was modified to allow stimulation with single or multiple extrastimuli and overdrive pacing. To evaluate the efficacy, safety and tolerance of external cardiac programmed stimulation, a standard arrhythmia termination protocol was used in 223 tachycardias in 22 patients. The technique of external cardiac programmed stimulation was used in 209 episodes of SVT in 13 patients. It terminated 95% of the episodes with success in 19 of 20 episodes of atrioventricular nodal reentrant tachycardia and 179 of 189 episodes of atrioventricular reciprocating tachycardia. Of 198 episodes of SVT terminated by the technique 168 (85%) were terminated by a single extrastimulus and 28 (14%) by double extrastimuli. Only 2 episodes of SVT required overdrive pacing for termination. External cardiac programmed stimulation did not result in atrial fibrillation or arrhythmia acceleration. Of 14 episodes of sustained monomorphic VT 5 were terminated by external cardiac programmed stimulation. One tachycardia was terminated by a single extrastimulus, 1 by double extrastimuli and 3 by overdrive pacing. Arrhythmia acceleration occurred once and was terminated by endocardial pacing. On 27 separate occasions patient evaluation of maximal discomfort included 4 ratings of mild, 10 of moderate, 11 of severe and 2 of intolerable discomfort. External cardiac programmed stimulation is effective and safe in patients with well-tolerated sustained supraventricular or ventricular arrhythmias.

Use of the esophageal pill electrode for pacing inhibition of bipolar VVI pacemakers

Inhibition of pacing is often needed to analyze the underlying cardiac rhythm and to interpret the 12-lead electrocardiogram (ECG) under various conditions, including acute myocardial ischemia or suspected infarction. Permanent bipolar demand pacemakers are generally more difficult to inhibit than unipolar demand pacemakers using the chest wall stimulation technique. 1 Chest wall twitching and pain may occur at higher stimulation currents and pulse widths. Recently, an easy to swallow pill electrode has become available to record atrial activities to assist in the diagnosis of complex cardiac arrhythmias, in which P waves are not discernible on the surface ECG. 2–4 The pill electrode has been further used for transesophageal atrial pacing with a high current output (≥25 mA). 5 We explored the possibility of using the esophageal pill electrode to deliver stimuli at a lower current (≤20 mA) and pulse width (≤10 ms) to inhibit permanent bipolar VVI pacemakers.

Intermittent Ventricular Standstill During Chronic Atrial Fibrillation in Patients with Dizziness or Syncope

Thirty-two patients with atrial fibrillation and normal ventricular rates who complained of dizziness or loss of consciousness underwent 24-hour ambulatory electrocardiographic monitoring. A control group of 25 patients in atrial fibrillation but without symptoms of dizziness or loss of consciousness was likewise investigated. All patients remained in atrial fibrillation; periods of ventricular standstill (mean, 2.9; range, 1.8-8.0) were present in 31 symptomatic patients but in only three of the control patients (mean, 1.9 s; range, 1.7-2.4). Twenty-three symptomatic patients with pauses greater than or equal to 2.0 s received a demand pacemaker. Following pacing, nineteen became completely asymptomatic; four patients continued to have dizziness but three of these, who also experienced syncope, no longer did so (mean follow-up, 13 months; range, 6-30). It is suggested that ventricular standstill may commonly occur in patients with controlled atrial fibrillation who complain of dizziness or syncope and that the majority will benefit from permanent cardiac pacing.

Noninvasive Conversion of a Fixed-Rate Demand Pacemaker to Activity Mode: A Method for Assessing the Clinical Effect of Rate-Responsiveness

Some patients with fixed-rate demand pacemakers may benefit from conversion to a rate-responsive pacing system. In this report, we describe a technique by which the effect of rate-responsive pacing can be assessed before replacing the pacemaker system. An externally positioned activity-mode physiologic pulse generator was used to drive a previously implanted ventricular demand pacemaker programmed to the triggered mode. Comparison of exercise capacity under both conditions suggested a substantial benefit from rate-responsiveness.

Permanent cardiac pacing in patients with the long QT syndrome

A permanent pacemaker was inserted in eight patients with the long QT syndrome. All had recurrent syncope or seizures, six had documented torsade de pointes and four had aborted sudden death. Among the eight patients, permanent pacing was instituted in three who were unsuccessfully treated with both a beta-adrenergic blocking agent and left cardiothoracic sympathectomy, and in two who proved refractory or intolerant to beta-blockers. Another three patients had pacemaker implantation and long-term beta-blocker therapy because of spontaneous atrioventricular (AV) block in one, aborted sudden death in one and patient preference in one. After pacing (70 to 85 beats/min), there was no significant change in the mean corrected QT interval, but the mean QT interval decreased significantly (534.4 +/- 51.4 to 425.6 +/- 18.9 ms, p less than 0.0001). Over a mean follow-up period of 35.1 +/- 18.9 months, all patients are alive and currently free of syncope. One patient without a history of stress-induced syncope had two syncopal episodes (believed to be due to hyperventilation) while under severe emotional stress, but has been symptom free for the past 5 years. One patient with an atrial demand (AAI) pacemaker developed dizziness due to documented episodes of AV block, but remains asymptomatic after conversion to atrial rate-responsive dual chamber (DDD) pacing. Either atrial or ventricular pacing combined with beta-blocker therapy appears to be effective treatment for a subset of patients with the long QT syndrome, by either preventing episodes of torsade de pointes or alleviating symptoms due to bradycardia from beta-blocker therapy.

Quantification of atrial contribution to left ventricular filling by pulsed Doppler echocardiography and the effect of age in normal and diseased hearts

Atrial filling fraction, or the fraction of stroke volume resulting from atrial contraction, was measured by Doppler echocardiography from the time-velocity integral of mitral anulus inflow with a method that allows separation of conduit or passive flow from flow resulting from the atrial contraction. The method was validated in 17 patients with externally programmable ventricular demand pacemakers by showing that the time-velocity integral of passive flow (excluding the A wave) during sinus or sequential atrioventricular pacing was almost identical to the time-velocity integral during ventricular pacing. Atrial filling fractions were then measured in 41 normal subjects, aged 20 to 80 years; 28 patients with echocardiographic evidence of concentric left ventricular hypertrophy; 24 with dilated cardiomyopathy (13 of whom had an ischemic origin); and 19 with acute myocardial infarction. Atrial filling fraction increased significantly with age in normal subjects (r = 0.77; p < 0.001) and ranged from 12% in a 20-year-old man to 46% in a normal 80-year-old woman. In the hypertrophy group, atrial filling fraction had a weak relation with age (r = 0.47; p = 0.006), and the values were significantly higher than in normal subjects. In patients with cardiomyopathy or infarction, atrial filling fraction varied over a wide range and showed no relation to age. Thus, atrial filling fraction as determined by Doppler echocardiography is significantly altered by both age and left ventricular disease. Age-corrected nomograms are essential when assessing atrial filling fraction in individual patients.

The carotid sinus syndrome: A frequently overlooked cause of syncope in the elderly

Exaggerated carotid sinus reflexes may account for alterations in consciousness responsible for significant disability and injury in elderly patients. Nonspecificity of symptoms and concomitant medical conditions frequently delay diagnosis and therapy. During a recent 9-year period, 82 patients were identified as having symptomatic carotid sinus hypersensitivity (CSH). Fifty-nine patients described complete syncope, 73 patients had multiple syncopal or near-syncopal episodes, and 40 patients related cervical pressure or motion as provocative events. Electrophysiologic testing demonstrated that 47% had cardioinhibitory CSH, 26% had vasodepressor CSH, and 27% had combined vasodepressor and cardioinhibitory CSH. The mean follow-up period of all patients was 36 months. Surgical therapy included ventricular demand pacemaker implantation in 33 patients and carotid sinus denervation in seven patients. Medical therapy was used in 32 patients, 11 mildly symptomatic patients were not treated, and 3 patients had carotid sinus irradiation. Pacemaker implantation relieved symptoms in 53%; however, 11 patients (33%) had significant postoperative complications. Carotid sinus denervation relieved symptoms in 86%, medical therapy in 54%, and carotid sinus irradiation in 33% of patients. Because of its demonstrated effectiveness in all variants of CSH and negligible perioperative morbidity, carotid sinus denervation should be offered to acceptable operative candidates when the diagnosis of CSH is confirmed.

Spontaneous Rupture of a Pacemaker Battery

To the Editor.— Rupture of pacemaker batteries is rare. Mercury-zinc batteries, used to power early pacemakers, have largely been replaced because their warranties lasted only three years. We believe ours is the first reported case of spontaneous rupture of an implanted mercury-zinc pacemaker battery. Report of a Case.— A 62-year-old man who had a ventricular-inhibited demand pacemaker placed in August 1978 for complete heart block arrived at the emergency department complaining of sudden swelling and pain over the pacemaker site. At 2 AM the patient was awakened by what he described as an explosion in his chest. Physical examination showed an elderly man in mild distress. His vital signs were normal except for a temperature of 38 °C (101 °F). The pacemaker site was swollen and erythematous, and the overlying skin was warm. Physical examination showed no other remarkable findings. A chest x-ray film showed fragments outside the epoxy casing

Ambulatory blood pressure and assessment of pacemaker function.

Ten patients in sinus rhythm with ventricular demand (VVI) pacemakers implanted for the sick sinus syndrome underwent 24 hour ambulatory blood pressure and electrocardiographic recording by a modified version of the Oxford system. Five patients had symptoms of dizziness or presyncope at the time of study and five were symptom free. The onset of pacing was associated with a fall in arterial blood pressure in both groups which was larger in the patients with symptoms, and in these patients the blood pressure recovery consequent on baroreflex activation was delayed by up to fifteen beats. In three of the patients with symptoms the original pacemaker was replaced by an atrioventricular pacing (DVI) device. This abolished symptoms and the initial fall and delayed recovery of blood pressure. Thus it appears that the development of symptoms of hypotension after the onset of ventricular pacing is determined by the rate of the baroreflex response. These symptoms and the haemodynamic consequences may be alleviated by dual chamber pacing.

Pacemakers of the 1980s. An overview.

Methods and devices for permanent cardiac pacing remained relatively stable for over two decades with use of the single-chamber ventricular demand (VVI) pacemaker. However, changes have occurred in the 1980s and are expected to continue with the availability of more advanced technology and with increasing knowledge about cardiac pacing. The physiologic benefit of the newer dual-chamber atrial synchronous (VDD) and fully automatic, universal (DDD) pacemakers over the VVI pacemaker in patients with permanent complete heart block and normal sinus node function has been established. These newer units not only reestablish atrioventricular synchrony but also are physiologically rate-responsive. The VDD pacemaker is expected to be phased out in favor of the DDD pacemaker. When the atrial rate or interval is lower than the lower rate limit, the VDD pacemaker functions as a VVI, whereas the DDD pacemaker functions as an atrioventricular sequential (DVI) pacemaker to maintain continuous atrioventricular synchrony. Contrary to general belief, patients with complete heart block and normal sinus node function may gain very little physiologic benefit, if any, from DVI pacing. The sinus node will compete with the pacemaker's atrial stimulation when the sinus rate is faster than the DVI pacemaker rate (which usually occurs during activity). Also, the ventricular pacing rate will not vary with physiologic change. The DVI and atrial demand (AAI) pacemakers have been used in some patients with sinus node dysfunction. Increasing exercise tolerance should not be expected in the majority of patients because they are not pacemaker-dependent during activity, ie, their heart rate is higher than the pacemaker rate. However, these pacemakers appear to help in eliminating pacemaker syndrome, which does not infrequently occur with VVI pacemakers. Patients with sinus node dysfunction but without atrioventricular block do not gain more physiologic benefit with a DDD than with a DVI pacemaker. Whether these patients have severe sinus node dysfunction all the time or adequate sinus node function most of the time during follow-up, the DDD pacemaker will function as a noncommitted DVI with atrial sensing (DDI). The early report of DVI pacemaker-induced atrial fibrillation during follow-up has been refuted by more recent works. If the DDD pacemaker is significantly more expensive than the DVI pacemaker, the latter type may be a good alternative for this condition.

Familial sinus node disease and degenerative myopia--a new hereditary syndrome?

A family is reported in which the father and both offspring suffered from sick sinus syndrome (SSS) accompanied by degenerative myopia in the two elder of the three family members. In all three individuals, the basic manifestations of the SSS were total sinus arrest with secondary AV junctional rhythm at a normal rate. Only the 7-year-old boy also exhibited paroxysmal atrial flutter and ventricular asystole lasting up to almost 7 s. Since he had, furthermore, recently sustained a left hemiparesis, a ventricular demand pacemaker was implanted. Chronic atrial fibrillation was eventually established in the father in whom observations were available for 16 years. Myopia of -11 D and -4.5 D, respectively, existed in the father and his 14-year-old daughter. The familial association of this defect with SSS suggests a hitherto undescribed genetic syndrome, presumably with underlying autosomal dominant transmission of the two traits.

Dysautonomie en deux temps au cours d'un syndrome de Guillain-Barré

Autonomic dysfunction is described in a 63 year old woman suffering from Guillain-Barré syndrome. Bradyarrhythmias occurred during the convalescent phase, whereas neurologic and respiratory symptoms were improving; they were not related to bronchial aspirations. Their severity and the inefficiency of medical treatment led to the insertion of a demand pace-maker. Cardiac monitoring by the Holter method in severe cases of Guillain-Barré syndrome may detect potentially lethal arrhythmias, that may then be avoided by a demand pace-maker.

Identification of pacemaker dependent patients by serial decremental rate inhibition.

In a study of the concept of pacemaker dependence, 86 patients who had permanent ventricular demand (VVI) pacemakers implanted for more than six months and were in predominantly paced rhythm underwent repeated interruption of pacing both abruptly and after gradual reduction of paced rate. Non-invasive pace slowing was accomplished by timed inhibiting pulses applied to the chest wall. The results identified a small group (A) of patients, 8% of those tested, who consistently failed to develop an adequate escape rhythm and may thus be considered highly pacing dependent. A second group B, 26%, developed an adequate intrinsic rhythm with serial decremental rate inhibition (SDRI) but suffered symptoms with abrupt complete inhibition (ACI). The remaining 66%, group C, developed no symptoms in any test. Analysis of clinical pre-test data showed that syncope, atrioventricular block and a low rate prior to implant, and a long duration of pacing were associated with a higher degree of pacing dependence, but were not reliably predictive. The clinical significance and value of the results are discussed. We conclude that SDRI is a reliable test for the high degree of pacemaker dependence and can be helpful especially in planning a procedure which may involve interruption of pacing.

Vagotonia in infants, children, adolescents and young adults

Twenty-four patients with various manifestations of increased vagal tone were seen between 1975 and 1981. Three distinct groups could be identified by clinical characteristics and to some extent by age. The first group showed evidence of prolonged atrioventricular conduction on their electrocardiograms but were asymptomatic. The others presented with syncope, the etiology of which was determined to be vasovagal. Some patients were older and more athletic. They suffered from syncope associated with exercise or heavy exertion. The youngest patients, however, experienced frequent prolonged episodes of syncope often mistaken for seizures. Treatment for the older patients with syncope consisted mainly of behavior modification, while 5 out of 6 younger patients required the implantation of a ventricular demand pacemaker to prevent repeated and problematic recurrences of syncope.