Atrial Demand Pacing Research Articles

Abnormally high Patient State Index associated with epicardial pacing: a case report

BackgroundAnesthesiologists monitor electroencephalography (EEG) intraoperatively to maintain adequate depth of anesthesia. However, the EEG signal is affected by noise and interference. The SedLine® is a brain function monitor with which the Patient State Index (PSI) is calculated. In this study, we report abnormally high PSI values associated with epicardial pacing during open heart surgery.Case presentationA 50-year-old man was scheduled for total arch replacement. Atrial demand pacing was started before weaning from cardiopulmonary bypass. The PSI increased from 30 to 80 soon after the start of pacing, and the EEG waveform showed spikes synchronized with the pacing. As the pacing output was lowered, the spikes on the EEG attenuated and disappeared, and the PSI decreased to < 40. When the pacing output was increased again, the spikes recurred, and the PSI increased again.ConclusionsPacemaker spikes may cause contamination of the EEG, resulting in abnormally high PSI values.

Assessment of Left Ventricular Dyssynchrony and Cardiac Function in Patients with Different Pacing Modes Using Real-Time Three-Dimensional Echocardiography: Comparison with Tissue Doppler Imaging

Background: Previous studies revealed that right ventricle apex pacing with different modes may yield abnormal electrical activity and left ventricle dyssynchrony.Aim of the work: To evaluate systolic function of left ventricle and mechanical dyssynchrony with different modes of pacing using real time three dimensional echocardiography [the RT3DE] and tissue Doppler imaging [TDI].Patients and Methods: The study included thirty-five individuals with permanent dual chamber pacemaker with atrial leads placed in right atrial appendage and right ventricular leads placed in right ventricular apex, the pacemakers were programmed to different modes. Imaging parameters were obtained following pacing for 24 hours in each mode.Results: The results revealed that the RT3DE and TDI-derived dyssynchrony indices in the atrial demand pacing [AAI] mode were significantly lower than those in the dual chamber demand pacing [DDD] and ventricular demand pacing [VVI] modes; however, there was no significant difference between the DDD and VVI modes. Also, left ventricular ejection fraction [LVEF] during AAI and DDD modes was significantly higher than that during VVI mode; however, there was no significant difference between the DDD and AAI modes. There were negative correlations between LVEF and Ts-MD and Ts-SD, and there was positive strong correlation between RT3DE and TDI-derived dyssynchrony indices.Conclusions: Left ventricular systolic synchronicity in AAI mode was superior to that in DDD and VVI modes. Left ventricular ejection fraction in the AAI and DDD pacing modes are superior to that in the VVI mode.

Strategies for Temporary Cardiac Pacing in Pediatric Patients With Postoperative Junctional Ectopic Tachycardia.

POSTOPERATIVE JUNCTIONAL ectopic tachycardia (JET) occurs in 6% to 14% of all pediatric patients after surgery for repair of congenital heart defects. In combination with postoperative systolic and diastolic ventricular dysfunction, the tachycardia and the absence of synchrony of atrial and ventricular contraction result in relevant hemodynamic compromise. Without adequate treatment, such rhythm disorder is associated with increased morbidity and mortality. Therapy for JET comprises administration of antiarrhythmic drugs, deep sedation, and induced hypothermia. Temporary pacing is a further important pillar of treatment. Different techniques of temporary pacing exist that aim either to reduce the effective heart rate or to resynchronize atrial and ventricular contraction. The aim of this article is to describe 4 different strategies of external cardiac pacing in pediatric patients with postoperative JET (atrial demand pacing [AAI], dual-chamber pacing [DDD], paired ventricular pacing [PVP], and ventricular-triggered atrial pacing [AVT]). Advantages and disadvantages of the described strategies will be discussed.

Single-centre experience on endocardial and epicardial pacemaker system function in neonates and infants

Endocardial (ENDO) or epicardial (EPI) pacing systems are implanted in infants but it remains unclear which system should be preferred. We evaluated the results of children <or=1 year who underwent pacemaker (PM) implantation at our centre with a retrospective analysis. Between 1992 and 2004, 56 patients, 37 of whom had other congenital heart defects (CHDs), received a PM at 4.4 +/- 3.8 months of age for atrioventricular block (n = 52) and sinus node dysfunction. Rate-responsive ventricular demand pacing (VVIR) PMs were implanted in 25 patients (19 ENDO), dual-chamber demand pacing (DDD) in 29, and rate-responsive atrial demand pacing (AAIR) in 2 (all EPI). Follow-up (FU) was 4.5 +/- 3.5 (range 0.3-13) years: 15 pacing system failures occurred among the 56 patients (26%) after 4.5 +/- 3.2 years, with a significantly reduced success rate for EPI (21-fold increase of the risk of failure) and complex CHD. Also in patients without surgery for CHD, EPI showed a worse outcome. Among the 91 leads implanted, failures occurred more significantly in EPI (18% of atrial, 24% of ventricular leads) than in ENDO (5% of ventricular leads). No venous occlusion was found at FU. Single-lead, VVIR ENDO pacing had higher efficiency and safety than EPI, and it might be the best choice for PM implantation in infants. However, because of small patient numbers and lack of longer FU, these findings should be treated with caution.

Disorders of Sinus Function.

Sinus node dysfunction is a common entity with significant clinical implications. Establishing a diagnosis may, on occasion, tax the skills of the clinician. Many causes have been cited, but no single factor appears to be established. Immunologic abnormalities may play a part in the etiologic process. Clinical invasive electrophysiology studies may be used to establish a diagnosis. In general, medical therapy must be integrated. Controversy exists regarding the best method of permanent pacing. Treatment may need to be individualized to the type of arrhythmia noted. Long-term prognosis is a large factor in choice of therapy, related to the underlying disease. Prevention of atrial fibrillation may occur with dual-chamber pacing; however, anticoagulation appears essential in this patient subgroup. The 5-year mortality rate in these patients is high and does not appear to be significantly improved with artificial pacing. Mortality is prominently influenced by the coexistence of cardiovascular and valvular heart disease. Patients who die do not differ substantially from survivors with regard to type of sinus dysfunction, occurrence of tachyarrhythmia, or distal conduction abnormalities. The survival rate in patients with sick sinus syndrome and congestive heart failure is significantly lower, and the incidence of embolic events remains high in patients with permanent pacing and the sick sinus syndrome. Thus, it has been proposed that all patients exhibiting the bradycardia-tachycardia syndrome be fully anticoagulated. The incidence of atrial fibrillation is significantly lower in patients with atrial demand pacing (22.3% versus 3.9%) than in patients with ventricular pacing and is accompanied by a decreased incidence of systemic embolization (13% versus 1.6%). Reports comparing survival with use of dual-chamber pacing versus ventricular pacing are encouraging in patients with congestive heart failure. At present, the natural history of the disease is unknown; furthermore, clinical risk factors for the development of symptoms have not been defined, and no electrophysiologic measure of sinus node function has been demonstrated to have reliable predictive value. Therefore, common practice has been to withhold pacemaker therapy in the asymptomatic patient.

Atrial demand pacing in patients with symptomatic sick sinus syndrome.

Atrial demand pacing provides a physiological, simply implemented, and less costly alternative of cardiac stimulation in symptomatic sick sinus syndrome (SSS) patients. Hindrance from widespread use stems mainly from the potential development of high degree AV block and persistent atrial fibrillation. A reappraisal of atrial pacing is now justified as we gain more clinical information. In this study we examined retrospectively the clinical course of 22 well-selected SSS patients paced in AAI mode for 30 +/- 29 months. Two patients had infrequent short-run atrial tachyrhythmia before implantation. There was an early lead dislodgement which required repositioning later. Three acute threshold increments were noted which necessitated a change in atrial pacing site in one and short-term steroid use in the other two. No other sensing, pacing or operative complication occurred and all pacing systems performed well. AII patients survived during follow-up and no patient developed congestive heart failure, though depressed left ventricular function was found in three preoperatively. No high degree AV block was encountered. Four patients presented paroxysmal atrial fibrillation (PAF) 25 +/- 16 months after the procedure, of whom one developed chronic atrial fibrillation. No single factor predicted the development of PAF. Resumption of normal pacemaker function always occurred immediately in the pause following cessation of PAF and no revision of pacing mode was required in the patient with chronic AF. Symptomatic relief was obtained in all patients. In summary, single chamber, single rate atrial pacing remains a physiologic, reliable, economic and easily implemented pacing modality affordable to a number of sick sinus patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Systematic nocturnal atrial demand pacing results in high-output heart failure.

Beat-to-beat parameters of heart rate (HR), intra-arterial blood pressure (BP), central venous pressure, and derived indexes of cardiac output and total peripheral resistance were recorded 18 h/day (from 1800 to 1200 h the following day) in four monkeys (Macaca mulatta) during 20 control days followed by 20 days of atrial demand pacing. The pacing rate was set at approximately 10 beats/min above the fastest hourly average HR recorded during the control period, i.e., sufficient to prevent the normal nocturnal fall in HR. Nocturnal pacing resulted in progressive weekly increases in central venous BP and arterial BP. Analyses of levels and diurnal trends in hemodynamic parameters and cardiac function curves across consecutive 5-day periods of nocturnal pacing revealed a hemodynamic pattern characteristic of high-output heart failure, which progressively increased (week by week) during the early morning hours (0500-0700). Sustained elevated left ventricular work resulting from the prevention of a nocturnal fall in HR may have been responsible for the reduction in cardiac function seen in this experimental model.

Effect of nocturnal atrial demand cardiac pacing on diurnal hemodynamic patterns.

Heart rate (HR), stroke volume (SV), intra-arterial blood pressure, and central venous pressure were recorded on a beat-to-beat basis, 18 h/day (1800-1200 h the following day), for approximately 2 mo in four monkeys (Macaca mulatta). Cardiac output, left ventricular work, and total peripheral resistance were derived from these primary measurements. During the 1st mo we measured these parameters under control conditions, and during the 2nd mo the animals were studied while HR was paced by atrial demand pacing sufficient to prevent the normal nocturnal fall in HR (approximately 10 beats/min above the fastest hourly average rate recorded during the control condition). The main hypothesis of this study was that when HR is prevented from falling, SV, which normally does not fall overnight, would fall; this hypothesis was confirmed. In addition, we observed that, during the period of pacing, relative to the control period, SV was approximately 14% greater during the early evening and 4% lower during the early morning; total peripheral resistance was similar during the early evening but was 13% higher by morning. Throughout the night, systolic pressure was approximately 4% greater, diastolic pressure was 17% higher, central venous pressure was 43% greater, and left ventricular work was 27% higher. These findings show that when HR is prevented from falling overnight by atrial demand pacing, even to a relatively modest degree, there can be very significant sustained changes in cardiovascular function.

Relative importance of activation sequence compared to atrioventricular synchrony in left ventricular function

This study evaluated the relative hemodynamic importance of a normal left ventricular (LV) activation sequence compared to atrioventricular (AV) synchrony with respect to systolic and diastolic function. Twelve patients with intact AV conduction and AV sequential pacemakers underwent radionuclide studies at rest and Doppler echocardiographic studies at rest and during submaximal exercise, comparing atrial demand pacing (AAI) to sequential AV sensing pacing (DDD) and ventricular demand pacing (VVI). Studies at rest were performed at a constant heart rate between pacing modes, and the exercise study was performed at a constant heart rate and work load. Cardiac output was higher during AAI than during both DDD and VVI (6.2 ± 1 vs 5.6 ± 1 and 5.3 ± 1 liters/min, p < 0.05). LV ejection fraction was likewise higher during AAI (55 ± 12 vs 49 ± 11 vs 51 ± 13, p < 0.05). VVI with or without AV synchrony was associated with a paradoxical septal motion pattern, resulting in a 25% impairment of regional septal ejection fraction. In addition, LV contraction duration was more homogenous during AAI. Peak filling rate during AAI and VVI was higher than during DDD (2.86 ± 1 and 2.95 ± 1 vs 2.25 ± 1 end-diastolic volume/s; p < 0.05). During VVI, the time to peak filling was significantly shorter than during both AAI and DDD (165 ± 34 vs 239 ± 99 and 224 ± 99 ms; p < 0.05). Doppler echocardiographic evaluation of cardiac systolic function (peak aortic blood velocity, mean aortic blood acceleration and systolic ventricular time integral) during rest and submaximal exercise showed improved LV performance with AAI compared to both DDD and VVI. VVI with or without AV synchrony resulted in an altered activation pattern of the left ventricle, associated with delayed onset, asynchronous contraction, interventricular septal motion abnormalities and an impaired LV systolic function. These changes persisted during submaximal exercise. Peak filling rate depended more on a normal LV activation pattern than on AV synchrony. It is concluded that normal ventricular activation is a prerequisite for optimal LV function. Pacing systems allowing a normal ventricular activation pattern (AAI or DDD with a long AV delay) are preferred for patients who have intact AV conduction but require artificial pacing.

Problems with Permanent Atrial Pacing in the Fontan Patient

Transvenous atrial pacing is the preferred method for control of both brady and tachyarrhythmias in the postoperative pediatric patient with normal atrioventricular conduction. We reviewed our experience with the use of permanent atrial pacing for the control of bradycardia and tachycardia in the Fontan patient. We then compared this pacing experience to atrial pacing data compiled for postop Transposition of the Great Arteries (TGA) patients. Out of twenty-five Fontan patients followed at the Medical University of South Carolina, six patients have had atrial arrhythmias necessitating pacing (24%). Underlying congenital heart disease included tricuspid atresia physiology in three and single ventricle in three. The indications for atrial pacing was brady-tachy syndrome in four patients and sick sinus syndrome in two. Pacers were inserted immediately post-op in three patients and 1.5 years, 2 years, and 8 years post Fontan in the other three. These six patients have required a total of nine pulse generator implantations. Five of the nine pacers were inserted transvenously and four via thoracotomy. In contrast to our experience with permanent atrial pacing in post TGA patients, dysrhythmia control with atrial pacing in the Fontan patient has been more difficult to achieve. The Fontan patients have a higher incidence of symptomatic dysrhythmias, hospitalizations, and antidysrhythmic medication requirements after pacer insertion. Implantation thresholds of the Fontan patients are higher than those of the transposition group. While successful atrial demand pacing is attainable in both groups, antitachycardia pacing is more reliable in the post-op TGA patient. The Fontan procedure seems to present a new set of obstacles for successful atrial pacing in the pediatric post-op patient.

The Natural History of Sick Sinus Syndrome

A literature review has addressed the two major factors in disease progression in sick sinus syndrome: atrioventricular block and atrial fibrillation. An incidence of atrioventricular block of 8.4 percent in a follow-up period of 34.2 months is considered clinically significant and sufficient to justify use of a ventricular lead in pacemaker management. Atrial fibrillation occurs much more commonly (22.3%) in ventricular pacing than with atrial demand pacing (3.9%) in a 2 1/2 year observation period. Coincident with the reduction in arrhythmia achieved by atrial demand pacing is a significant reduction in systemic embolism (1.6% vs. 13%). This is considered largely to be due to the improved rhythm control with AAI pacing but also possibly to the avoidance of retrograde atrioventricular conduction. The benefits of AAI pacing in terms of mortality in sick sinus syndrome have not yet been fully assessed. In the future, DDI pacing is recommended with, in some patients, the addition of another sensor to provide rate responsiveness on exercise.

Reflex Cardiac Asystole

In this report we present the case of a patient with recurrent syncopal episodes. During one of the attacks the patient was monitored by telemetry and the ECG lead showed asystole for more than 7 seconds. As in cases of the cardioinhibitory type of hypersensitive carotid sinus syndrome (HCSS), asystole may represent suppression of the sinus node or suppression of both sinus and atrioventricular (AV) node. Unfortunately, in contrast to HCSS, there is no maneuver that can reproducibly induce episodes of asystole. Consequently, very little is known about the occurrence of AV block in the presence of sinus arrest. In the patient described in this report, we were able to demonstrate that suppression of sinus and AV nodes occurred simultaneously. It is interesting to note that in this type of syncope data from noninvasive and invasive techniques in assessing sinus nodal and AV nodal conduction may not be conclusive. In the group of patients with this type of syncope, permanent atrial demand pacing is contraindicated.

Long-term endocardial atrial pacing in children with postoperative bradycardia-tachycardia syndrome and limited ventricular access

Permanent pacing in children, including those with postoperative bradycardia-tachycardia syndrome, has been compromised by the availability of pulse generators, electrode leads and implantation techniques designed for the adult patient. Recent technologic improvements and simplified implantation techniques have reduced many of these barriers and have made endocardial as well as epicardial ventricular pacing more feasible. However, in some children, ventricular pacing may be impeded by anatomic abnormalities due to congenital anomalies or prior cardiac operations. In these instances, endocardial atrial pacing may provide an alternative therapeutic approach in selected patients. This report describes the use of endocardial atrial demand pacing in four children with postoperative bradycardia-tachycardia syndrome and restricted ventricular access. This approach controls symptomatic bradycardia, helps prevent and convert paroxysmal intraatrial tachycardia and overcomes the problem of limited ventricular access.

Permanent pervenous atrial pacing from the coronary vein. Long-term follow-up.

This report details our clinical experience during a 12 to 63 month follow-up period in 30 patients with permanent pervenous atrial pacemakers implanted in the coronary vein prior to May 1972. Indications for permanent atrial pacing included 20 patients with symptomatic sinus bradycardia, seven with atrial brady-tachy syndrome refractory to pharmacologic therapy, and three patients with atrial overdrive suppression for intractible ventricular arrhythmias. The average duration of atrial pacing was 29.2 ± 2.4 ( sem ) months, median 24 months. A bipolar electrode was used in 28 patients and a unipolar system in two. The atrial signal was of sufficient amplitude (&gt;1.5 mV) to permit atrial demand pacing when required. The atrial pacing threshold averaged 2.0 ± 0.2 ma initially and increased by less than 1.0 ma at the time of battery replacement 20 months later. Only four of 30 patients (13%) developed pacemaker related problems during the 879 pacing months of this follow-up period. Coronary vein perforation or thrombosis was not observed, and there were no pacemaker related deaths. The coronary vein provides a safe and effective electrode location for long-term permanent pervenous atrial pacing.