Guidelines for implantation of cardiac pacemakers and antiarrhythmia devices. A report of the American College of Cardiology/American Heart Association Task Force on Assessment of Diagnostic and Therapeutic Cardiovascular Procedures (Committee on Pacemaker Implantation)

[History of the implantable cardioverter-defibrillator in Germany]

The implantable cardioverter-defibrillator (ICD) was a breakthrough in the prevention of sudden cardiac death. After years of technical development in the USA, Michel Mirowski succeeded in proving reliable automatic defibrillation of ventricular tachyarrhythmias through initial human implantations in 1980, despite many obstacles. Nearly 4 years later, the first patients received ICDs at multiple centers in Germany. Subsequently, outside the USA, Germany became the country with highest implantation rates. The absolute number of implantations remained small as long as implantations required epicardial defibrillation electrodes and therefore thoracotomy by cardiac surgeons. Pacemaker-like implantation using a transvenous defibrillation electrode with a pectoral ICD became feasible in the early 1990s pushing implantation rates to the next level. Technical advancements were accompanied by clinical research in Germany, and often, the first-in-human studies were conducted in Germany. In 1991, the first guidelines for indications were established in the USA and Germany. Several randomized studies on indications were published between 1996 and 2009, mostly led by American teams with German participation, but also under German leadership (CASH, CAT, DINAMIT, IRIS). The DANISH study in 2016 questioned the results of these long-standing studies. Instead of providing ICDs to patients using a broad indication, future efforts aim to identify patients who, despite optimal medical therapy, cardiac resynchronization therapy (CRT), and/or catheter ablation, need protection against sudden cardiac death. Risk scores incorporating myocardial scars in magnetic resonance imaging (MRI) and genetic information are expected to contribute to more individualized and effective indications.

Biomedical Implants with Charge-Transfer Monitoring and Regulating Abilities

Transmembrane charge (ion/electron) transfer is essential for maintaining cellular homeostasis and is involved in many biological processes, from protein synthesis to embryonic development in organisms. Designing implant devices that can detect or regulate cellular transmembrane charge transfer is expected to sense and modulate the behaviors of host cells and tissues. Thus, charge transfer can be regarded as a bridge connecting living systems and human-made implantable devices. This review describes the mode and mechanism of charge transfer between organisms and nonliving materials, and summarizes the strategies to endow implants with charge-transfer regulating or monitoring abilities. Furthermore, three major charge-transfer controlling systems, including wired, self-activated, and stimuli-responsive biomedical implants, as well as the design principles and pivotal materials are systematically elaborated. The clinical challenges and the prospects for future development of these implant devices are also discussed.

Consecutive electrocardiographic changes during percutaneous coronary intervention for acute coronary syndrome with high-grade atrioventricular block: a case report

Background

Acute coronary syndrome (ACS) with high-grade atrioventricular block (HAVB) still has a poor mortality risk, even in the current percutaneous coronary intervention (PCI) era. However, early PCI for ACS with HAVB is associated with improved in-hospital survival and a 6-month survival similar to that of ACS without HAVB.

Case presentation

A 70-year-old man was admitted to our hospital for ACS with HAVB. ECG showed complete AV block, complete right bundle branch block (CRBBB), and left axis deviation. Cardiac enzymes were elevated. He underwent temporary pacemaker insertion and coronary angiography, which showed severe stenosis of the proximal right coronary artery (RCA), 99% stenosis of the distal RCA with Thrombolysis in Myocardial Infarction (TIMI) grade 2 flow, and total occlusion of the proximal left anterior descending artery (LAD). We performed primary PCI in both the RCA and LAD, which resulted in TIMI grade 3 flow in both. After PCI, the HAVB recovered to normal sinus rhythm with CRBBB; a normal QRS interval returned within three days. The patient was discharged from the hospital without complications.

Conclusion

In this case of ACS with HAVB, early intensive coronary artery reperfusion resulted in long-term patient survival. The blood supply to the AV node and bilateral bundle branches is complex. Multivessel ischemia may compromise both primary and collateral blood flows to the AV node and septum, resulting in severe conduction impairment. Clinicians performing PCI should be aware of this anatomy and physiology.

Surgery in older people: an update

In the past two decades, the rate of surgery in older people has increased more rapidly than the rate of aging of the population, so both a larger proportion and a greater number of older people are now undergoing surgery. This may partly reflect a cultural change in surgery and anaesthesia with respect to a greater willingness to undertake elective procedures in older people, although there remain areas where they have less access to surgery than do younger patients. For instance, older people are less likely to undergo operative procedures after a cancer diagnosis. Furthermore, in those who do have surgery, resection rate (i.e. curative therapy) is lower than in younger people with equivalent tumour stages, and even more so in older patients with COPD, cardiovascular disease or diabetes. This article explores the complex relationship between age and surgical outcome, provides an evidence-based overview of risk assessment and common postoperative problems in older people, and summarizes good practice points (at times necessarily pragmatic) for clinical management of the older surgical patient. There has been a substantial expansion in the literature examining risks, outcomes and interventions in older surgical patients since the previous review article of this subject published in this journal. Although we do not cover anaesthesia in older people, the review of that topic remains relevant. The American Society of Anaesthesiologists' Classification of Risk which illustrates that risk is disease- rather than age- based, is shown in Table 1. Most publications examine elective rather than emergency surgery in older people (with the exception of hip fracture), and this is reflected in the content of the paper.

Long-Term Effects of Atrial Synchronous Ventricular Pacing on Systolic and Diastolic Ventricular Function in Patients with Normal Left Ventricular Ejection Fraction

BACKGROUND

Atrial synchronous right ventricular pacing (VP) may compromise ventricular function in patients undergoing pacemaker implantation for atrioventricular block. We assessed the usefulness of tissue Doppler imaging (TDI) and color M-mode echocardiography in evaluating patients with VP, and examined the long-term effects of VP on ventricular function by echocardiographic indices and B-type natriuretic peptide (BNP) measurements.

METHODS

We studied 60 clinically stable elderly dual-chamber pacemaker recipients (mean age: 74 +/- 9 years) who had normal left ventricular (LV) systolic function and on the long term the same cardiac rhythm, either intrinsic normal ventricular activation (IA) (n = 20), or VP (n = 40).

RESULTS

Paced patients, compared to patients with IA, had decreased stroke volume (p < 0.05) and a more depressed relaxation pattern, as indicated by decreased peak early mitral velocity (E)/peak atrial contraction velocity ratio and tissue Doppler imaging (TDI)-early transmitral diastolic velocity (Ea) measures (p < 0.05). Both groups presented similar BNP levels and LV filling pressures, as assessed by E/Ea and E/early diastolic transmitral flow propagation velocity. In VP patients, age (beta = 0.31), Ea (beta = -0.28) and E/Ea (beta = 0.32) emerged as independent predictors of BNP levels.

CONCLUSIONS

VP is associated with reduced LV systolic function and signs of impaired relaxation. Elevated BNP levels in elderly VP patients with normal ejection fraction may be predicted by TDI signs of LV diastolic dysfunction.

Management of the Pediatric Postoperative Cardiac Surgery Patient

Optimal management of the postoperative pediatric cardiac surgical patient requires a thorough understanding of patient anatomy, physiology, surgical repair or palliation, and clinical condition. This necessitates a dedicated team of clinicians including skilled nurses, physicians, and respiratory therapists specialized in the care of patients who have complex congenital heart disease. This article provides an overview of the multisystemic risk factors and consequences associated with cadiopulmonary bypass and cardiac surgery. An evaluation of cardiac hemodynamics and a review of major organ systems are included. Essential assessment information and interventional strategies for managing the pediatric postoperative cardiac surgery patient are detailed.

Chronotropic Incompetence in Patients with an Implantable Cardioverter Defibrillator: Prevalence and Predicting Factors

Chronotropic incompetence (CI), which has not been systematically examined in the ICD patient population, may have implications for device programming. A total of 123 ICD patients were classified into three groups: single-chamber ICD with sinus rhythm, dual-chamber ICD with sinus rhythm, and single-chamber ICD with permanent atrial fibrillation. Heart rate response, maximum oxygen uptake, and oxygen uptake at the anaerobic threshold were measured during treadmill exercise testing. In addition, clinical variables such as antiarrhythmic drug therapy, underlying heart disease, and left-ventricular (LV) ejection fraction were recorded. Of the patients studied, 38% were chronotropically incompetent (47/123). Significant predictors of CI were as follows: presence of a coronary disease (P = 0.036), prior cardiac surgery (P = 0.037), chronic drug therapy with beta-blockers (P = 0.032), administration of amiodarone (P = 0.025), and a combination of these two forms of treatment (P = 0.01). Spiroergometry revealed reduced exercise capacity (P = 0.041) and lessened VO2max (P = 0.034) among chronotropically incompetent patients. A large percentage of ICD patients demonstrates CI with subsequently reduced physical stress tolerance. In light of the DAVID study, we believe that a closer examination of rate-adaptive modes for ICD patients is warranted under enhanced conditions: (1) optimized AV interval programming; (2) utilization of new algorithms to reduce ventricular pacing in combination with rate-adaptive atrial pacing, with the goal of addressing CI while minimizing ventricular pacing; and (3) an optimized upper heart-rate limit.

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.

Paroxysmal atrioventricular block in young patients

We describe 17 patients (8 girls, and 9 boys), aged 9.6 +/- 5.7 years, with paroxysmal atrioventricular block (PAVB), a condition rarely described in children. Holter monitoring documented the PAVB in 15 patients, and tilt test was performed in 4 patients (positive in 1). The electrocardiograph (ECG) was normal in 7 patients. Two patients had acquired and 11 patients had congenital heart disease (CHD). Syncope or presyncope were present in 7 patients. A normal ECG was significantly more frequent in symptomatic patients. Pauses were significantly longer in girls and in children <5 years. PAVB was recorded only during nocturnal hours in 6 patients and throughout the day in the others. The sinus rate decreased during PAVB in 6 patients and increased in 4 (generally younger girls with symptoms). Permanent pacemakers were implanted in 13 patients, including 7 asymptomatic patients with CHD and severe bradycardia. During follow-up (3.7 +/- 2.5 years), 1 patient developed complete AVB. Although PAVB was still present in 91% of paced patients, symptoms did not recur because pacing prevented the pauses. In conclusion, PAVB is a rare arrhythmia. Autonomic nervous system dysfunction seems to play an etiological role and permanent pacing was an effective treatment.

Is Mobitz type I atrioventricular block benign in adults?

OBJECTIVE

To assess the need for pacing in adults with chronic Mobitz type I second degree atrioventricular block (Mobitz I).

DESIGN

Prospective study.

SETTING

District general hospital.

PATIENTS

147 subjects aged > or = 20 years (age cohorts 20-44, 45-64, 65-79, and > or = 80) with chronic Mobitz I without second degree Mobitz II or third degree (higher degree) block on entry, seen from 1968 to 1993 and followed up to 30 June 1997. Sixty four had organic heart disease. The presence of symptomatic bradycardia was defined as highly likely in 47 patients (class 1); probable in 14 (class 2); and absent in 86 (class 3).

INTERVENTIONS

Pacemakers were implanted in 90 patients for the following indications: symptoms in 74 and prophylaxis in 16.

MAIN OUTCOME MEASURES

The main outcome measure was death, with conduction deterioration to higher degree block or symptomatic bradycardia the alternative measure.

RESULTS

Five year survival to death was reduced in unpaced patients relative to that expected for the normal population (overall mean (SD) 53.5 (6.7)% v 68.6%, p < 0.001; class 3, 54.4 (7.3)% v 70.1%, p < 0.001). Paced patients fared better than unpaced (overall (mean (SD) five year survival 76.3 (4.5)% v 53.5 (6.7)%, p = 0.0014; class 3, 87.2 (5.4)% v 54.4 (7.3)%, p = 0.020; and organic heart disease, 68.2 (7.6)% v 44.0 (9.9)%, p < or = 0.0014). There were no deaths in the < 45 cohort. Survival to first outcome (main or alternative) was further reduced to 31.7 (5.0)% in 102 patients unpaced initially and 34.2 (5.7)% in class 3. Only the 20-44 cohort and patients with sinus arrhythmia had > 50% survival.

CONCLUSION

Mobitz I block is not usually benign in patients > or = 45 years of age. Pacemaker implantation should be considered, even in the absence of symptomatic bradycardia or organic heart disease.

Strategy for the management of vasovagal syncope

The disorders of autonomic control associated with orthostatic intolerance are a diverse group of syndromes that can result in syncope and near-syncope. A basic understanding of the pathophysiology of these disorders is essential to diagnosis and proper treatment. It is especially important to recognise the difference between the effect of prolonged upright posture on a failing autonomic nervous system (a hyposensitive or dysautonomic response) and the vasovagal response (which may be a hypersensitive response). Vasovagal syncope is the most common abnormal response to upright posture and occurs in all age groups. The advent of tilt table testing has helped define a population with an objective finding during provocative testing that has enabled researchers to study the mechanism of vasovagal syncope and to evaluate the efficacy of treatments. In most patients, vasovagal syncope occurs infrequently and only under exceptional circumstances and treatment is not needed. Treatment may be indicated in patients with recurrent syncope or with syncope that has been associated with physical injury or potential occupational hazard. Based on study data, patients with vasovagal syncope can now be risk stratified into a high-risk group likely to have recurrent syncope and a low-risk group. Many patients with vasovagal syncope can be effectively treated with education, reassurance and a simple increase in dietary salt and fluid intake. In others, treatment involves removal or avoidance of agents that predispose to hypotension or dehydration. However, when these measures fail to prevent the recurrence of symptoms, pharmacological therapy is usually recommended. Although many pharmacological agents have been proposed and/or demonstrated to be effective based on nonrandomised clinical trials, there is a remarkable absence of data from large prospective clinical trials. Data from randomised placebo-controlled studies support the efficacy of beta-blockers, midodrine, serotonin reuptake inhibitors and ACE inhibitors. There is also considerable clinical experience and a consensus suggesting that fludrocortisone is effective. Encouraging new data suggest that a programme involving tilt training can effectively prevent vasovagal syncope. For patients with recurrent vasovagal syncope that is refractory to these treatments, implantation of a permanent pacemaker with specialised sensing/pacing algorithms appears to be effective. A number of larger clinical trials are underway which should help further define the efficacy of a number of different treatments for vasovagal syncope.

Late recovery of surgically-induced atrioventricular block in patients with congenital heart disease

OBJECTIVES

To assess the incidence and establish possible predictors of late recovery of post-surgical heart block, treated with pacemaker implantation, in patients with congenital heart defects.

BACKGROUND

The American College of Cardiology/American Heart Association Task Force has recommended pacemaker implantation for advanced second or third degree atrioventricular block which persists for 7 to 14 days after surgery. The incidence of late recovery of post-surgical heart block following pacemaker implantation has not been reported.

METHODS

Records of 44 patients with post-surgical heart block who underwent pacemaker implantation at our institutions since 1976 were reviewed for demographic, anatomic, surgical and surface electrocardiographic data to assess the incidence of, and factors associated with, recovery of atrioventricular conduction on long-term follow-up.

RESULTS

32% (14) of patients recovered atrioventricular conduction at a median follow-up of 5.5 years while 68% (30) remained pacemaker dependent. The groups were similar in age and weight at surgery and period of follow-up p = 0.5). Types of defect and surgical repair were not significantly different (p > 0.1). There was a similar number of patients with second degree-type II block in both groups (p = 0.15). The groups did not differ in timing of pacemaker implantation (<10 days p = 0.14, >14 days p = 0.18).

CONCLUSIONS

Late recovery of atrioventricular conduction following pacemaker implantation for postsurgical heart block is common. However, clinical predictors, with reference to current recommendations, could not be identified. Prospective electrophysiologic evaluations may be warranted to establish guidelines for long term pacemaker dependency and criteria for pacing.

Setting up a falls and syncope service for the elderly

Establishing a neurocardiovascular investigation unit for the investigation of falls and syncope in the elderly is feasible. With the increasing growth in the elderly population, these units will be required to play an equally increasing role in both the clinical management of patients and the ongoing clinical research into the conditions that cause falls and blackouts in the elderly.

Indications for implantable cardioverter defibrillator therapy

The implantable cardioverter defibrillator (ICD) is now an integral therapy for cardiac patient care. More than 20 years have passed since the first ICD implant. Sudden cardiac death from arrhythmia (ventricular tachycardia and fibrillation) has been significantly decreased because of the use of ICD therapy. Primary treatment trials have shown ICD therapy to be superior to drug therapy. Most of these trials compared ICD therapy with amiodarone or sotalol. Prevention trials have also been completed. Patients with nonsustained ventricular tachycardia, low left ventricular ejection fraction, and coronary artery disease were evaluated with electrophysiology studies. Patients with inducible ventricular arrhythmias were treated with ICD or drug suppression therapy. ICD therapy was superior to drug therapy for prevention of fatal arrhythmias. Ongoing trials include evaluation of ICD therapy for patients with high-risk substrates: congestive heart failure, dilated cardiomyopathy, hypertrophic cardiomyopathy, and repolarization syndromes. Factors such as medication inefficacy/side effects, transvenous ICD implantation and overwhelming mortality benefits have expanded ICD usage beyond the original restrictive guidelines.

[Indications of automatic ventricular implantable defibrillator. Implications for daily practice]

The authors were the redactors of the Guidelines of the French Society of Cardiology for the indications of the automatic implantable defibillator, derived from the available indication in USA, and from the ulteriorly performed controlled studies. Three Class-I indications were selected: 1) circulatory arrest due to ventricular tachycardia (VT) or fibrillation (VF) whithout acute curable aetiology. 2) sustained VT with underlying heart disease and contractile alterations. 3) non-sustained VT with prior myocardial infarction and LVEF < 35% with inductible despite maximal drug therapy. Class-II indications were also three: 1) inheritable disease with high risk of sudden death without known effective therapy. 2) Syncope in patients with underlying heart disease and inductible VT or VF during electrophysiologic study. 3) VT or VF in patients in list for heart transplant.

Sinus node dysfunction and atrial tachycardia after the Fontan procedure: The scope of the problem

Similar to other atrial baffling procedures, the Fontan procedure exposes patients to ongoing morbidity and mortality. The development of the bradycardia-tachycardia syndrome can have adverse effects on already-marginal hemodynamics and ventricular function. Patients with Fontan physiology and sinus node dysfunction can be managed with antibradycardic pacemakers. Atrial arrhythmias after "completion Fontan" are difficult to treat and usually require either antiarrhythmic agents, antitachycardic pacemakers, or radiofrequency catheter ablation of the re-entrant circuit. Successful treatment of atrial flutter occurs in only 50% to 70% of patients. There is a high recurrence rate of atrial flutter with any of the accepted management strategies. Copyright 1998 by W.B. Saunders Company

The implantable cardioverter defibrillator

Implantable cardioverter defibrillators (ICDs) have evolved from the treatment of last resort to the gold standard therapy for patients at high risk for ventricular tachyarrhythmias. High-risk patients include those who have survived life-threatening arrhythmias, and individuals with cardiac diseases who are at risk for such arrhythmias, but are symptomless. Use of an ICD will affect the patient's quality of life. Some drugs can substantially affect defibrillator function and efficacy, and possible drug-device interactions should be considered. Patients with ICDs may encounter cell phones, antitheft detectors, and many other sources of potential electromagnetic Interference. In addition to treating ventricular tachyarrhythmias, new defibrillators provide full featured dual chamber pacing, and could treat atrial arrhythmias, and congestive heart failure by means of biventricular pacing.

Cardiac pacing. A review

Pacing is a field of rapid clinical progress and technologic advances. Clinical progress in the 1990s included the refinement of indications for pacing as well as the use of pacemakers for new, nonbradycardiac indications, such as the treatment of cardiomyopathies and CHF and the prevention of atrial fibrillation. Important published data and studies in progress are shedding new light on issues of pacing mode selection, and they may influence future practice significantly. Important technologic advances include development of new rate-adaptive sensors and sensor combinations and the evolution of pacemakers into sophisticated diagnostic devices with the capability to store data and ECGs. Automatic algorithms monitor the patient for appropriate capture, sensing, battery status, and lead impedance, providing better patient safety and pacemaker longevity.

Psychometric properties of Aquarel. a disease-specific quality of life questionnaire for pacemaker patients

In cardiac pacing current clinical practice permits the use of ventricular or atrioventricular-synchronous pacemakers. However, it is not known which type of pacemaker results in superior clinical and patient outcomes. To date, there is no feasible and validated disease-specific questionnaire for pacemaker patients to assess quality of life (QoL) available. The Aquarel questionnaire was developed as a disease-specific extension to the Short-Form-36 (SF-36). A cross-sectional study was carried out in 74 pacemaker patients to evaluate validity and reliability of this instrument. Items were selected and scales constructed based on factorial analysis. Internal consistency, content validity and test-retest reliability were moderate to excellent. Correlations with the SF-36 scales, pacing mode and functional tests were as hypothesized, demonstrating the individual value and distinctiveness of the Aquarel subscales. The results support the feasibility and usefulness of evaluating QoL in pacemaker patients when using Aquarel as an extension to the SF-36.

Diagnostic yield and development of a neurocardiovascular investigation unit for older adults in a district hospital

BACKGROUND

Dizziness, syncope, and falls are common occurrences in elderly people. Neurocardiovascular investigation units aim to detect those patients who fall due to disturbances of blood pressure control or cardiac conduction. Specialist units have a high diagnostic yield in the investigation of these problems. Does this translate to less specialized centers? We report on the diagnostic findings of a district general hospital neurocardiovascular investigation unit.

METHOD

A total of 120 consecutive patients over the age of 65 presenting to a single geriatrician were assessed. After a full history and physical examination, patients underwent neurocardiovascular investigation: blood pressure and heart rate response to active stand, carotid sinus massage, and 30-minute head-up tilt.

RESULTS

The 120 patients assessed had a mean age of 78 years (range 66-94 years); in this group, 85 were women. Of these patients, 23% presented with falls, 14% with blackouts, and 30% with dizziness. The remaining 33% had overlap of symptoms. Neurocardiovascular investigations produced a diagnosis in 57% of the patients: 22% had cardioinhibitory carotid sinus syndrome (CSS): 15% had vasodepressor CSS; 29% had orthostatic hypotension; and 3% had vasovagal syncope. Thirteen percent had more than one neurocardiovascular abnormality, and 18% had benign positional vertigo. Five patients had postural instability causing falls. Hyperventilation syndrome, aortic stenosis, dysrhythmia, cervical spondylosis, and epilepsy each accounted for one case. Seventeen percent of the subjects remained undiagnosed after integrated neurocardiovascular assessment.

CONCLUSION

Management of falls requires access to neurocardiovascular assessment. It is feasible to provide such a service in the district general hospital setting, with a comparable diagnostic yield to tertiary referral centers.

Dual demand pacing using retriggerable refractory periods for ventricular rate control during paroxysmal supraventricular tachyarrhythmias in patients with dual chamber pacemakers

The use of dual chamber pacing in patients with atrioventricular block and paroxysmal supraventricular tachyarrhythmias may present a clinical dilemma because of the rapid and erratic triggering of ventricular pacing. To avoid this, a variety of pacing methods have now been described, including the use of retriggerable atrial refractory periods or dual demand pacing. This review details the use, advantages, and limitations of this poorly understood algorithm referred to as "pseudo-mode switching."

The implantable cardioverter-defibrillator

Ventricular arrhythmias remain a major cause of cardiovascular mortality. Therapy for serious ventricular arrhythmias has evolved over the past decade, from treatment primarily with antiarrhythmic drugs to implanted devices. The implantable cardioverter-defibrillator (ICD) is the best therapy for patients who have experienced an episode of ventricular fibrillation not accompanied by an acute myocardial infarction or other transient or reversible cause. It is also superior therapy in patients with sustained ventricular tachycardia (VT) causing syncope or hemodynamic compromise. Controlled clinical trials have confirmed the utility of these devices. As primary prevention, the ICD is superior to conventional antiarrhythmic drug therapy in patients who have survived a myocardial infarction and who have spontaneous, nonsustained ventricular tachycardia, a low ejection fraction, inducible VT at electrophysiologic study, and whose VT is not suppressed by procainamide. The effect of the ICD on survival of other patient populations remains to be proven. The device is costly, but its price is generally accepted to be reasonable. The ICD has been a major advance in the treatment of ventricular arrhythmias.

Left atrial appendage function in patients with different pacing modes

Many studies suggest that patients who receive a ventricular pacemaker have a higher incidence of systemic thromboembolism compared to patients receiving a physiological pacemaker. However, the exact mechanism regarding the etiology of thromboembolism remains unclear. We evaluated the left atrial appendage (LAA) functions, using multiplane transesophageal echocardiography (TEE), in patients with different pacing modes. In order to evaluate the ejection fraction (EF), peak emptying (V(E)) and filling (V(F)) flow velocities of the LAA by TEE, we studied 31 patients (mean age 63+/-18.5 years) who had been paced for 5.0+/-2.9 years. Patients with atrial fibrillation, left ventricular dysfunction and mitral valve disease were excluded. The pacing indications were complete atrioventricular block (AVB) in 19 patients (9 VVI, 10 VDD or DDD) and sick sinus syndrome (SSS) in 12 patients (5 VVI, 7 DDD). Mean EF, V(E) and V(F) of the LAA were significantly lower in all patients with ventricular pacing (25.5+/-15.6%, 30.4+/-15.6 cm/s and 29. 1+/-19.2 cm/s, respectively) compared to those with physiologic pacing (48.5+/-16.9%, 59.6+/-16.3 cm/s, 57.9+/-18.5 cm/s, respectively) (P<0.01 in all). When patients were further classified with respect to underlying heart disease whether they had SSS or AVB, all measurements of the LAA (EF, V(E) and V(F)) in both subgroup of patients with SSS and AVB were found significantly lower in those with ventricular pacing than in those with physiologic pacing (Tables 3 and 4). This decrease, especially in LAA flow, was much greater in those with SSS (Mean V(E) and V(F) <20 cm/s). In a patient paced with VVI for SSS, a thrombus was detected within the LAA cavity. In conclusion, these results suggest that the pacing modality appeared to influence the LAA functions in paced patients. Patients with asynchronous ventricular pacing modes had a significantly higher incidence of depressed LAA functions than did patients with physiological pacing, especially more marked in patients with sick sinus syndrome. This may be a factor responsible for increased risk of thrombus formation and thromboembolic events in this patient population.

Clinical trials of pacing mode selection

Current recommendations in favor of dual-chamber over single-chamber ventricular pacing for patients with sinus node dysfunction or AV conduction disorders were made largely based on observational data and expert opinions. The first randomized pacing mode selection study was relatively small and suggested survival advantage with physiologic pacing only after an extended follow-up duration of 5.5 years. Preliminary results of the first large-scale multicenter randomized pacing mode selection trial revealed only modest reduction in atrial fibrillation without survival advantage after 3 years of physiologic pacing. Two other large-scale multicenter randomized trials comparing physiologic versus ventricular pacing are currently ongoing. They may provide further scientific evidence based on which more objective recommendations can be made with respect to pacing mode selection.

Pacing to prevent vasovagal syncope

Patients with frequent vasovagal syncope have markedly poor quality of life and are often resistant to treatment with standard pharmacologic approaches. Vasovagal syncope is due to combinations of bradycardia and hypotension. There is accumulating evidence that many of these patients may respond to permanent cardiac pacing. Several controlled open-label studies suggest that about half of paced patients no longer faint, and most of the rest are improved. At this point, we do not know the role of placebo, and specific pacing modes in this improvement are not known. Ongoing trials will clarify how to select patients and how best to pace them.

Role of pacing in the treatment of vasovagal syncope

Patients with frequent vasovagal syncope have a markedly poor quality of life and are often resistant to treatment by standard pharmacologic approaches. Although the evidence is not conclusive, clinical vasovagal syncope is probably associated with some degree of bradycardia. Studies of temporary pacing during tilt-table testing have shown that pacing prevents syncope in more than half of patients who develop a vasovagal response. Three open-label studies of permanent pacing showed that pacing was associated with substantial improvement, and the prospective randomized Vasovagal Pacemaker Study reported an 85% relative risk reduction in patients randomized to pacemaker therapy compared with medical therapy. The roles of specific pacemaker modes in vasovagal syncope have not been determined, although early evidence indicates that rate-drop responsiveness is useful. The second Vasovagal Pacemaker Study may clarify the role of rate-drop responsiveness.

"Rate-drop response" cardiac pacing for vasovagal syncope. Rate-Drop Response Investigators Group

Recent reports suggest that cardiac pacing incorporating a rate-drop response algorithm is associated with a reduction in the frequency of syncopal episodes in patients with apparent cardioinhibitory vasovagal syncope. The detection portion of the algorithm employs a programmable heart rate change-time duration "window" to both identify abrupt cardiac slowing suggestive of an imminent vasovagal event and trigger "high rate" pacing. The purpose of this study was to develop recommendations for programming the rate-drop response algorithm. Pacemaker programming, symptom status, and drug therapy were assessed retrospectively in 24 patients with recurrent vasovagal syncope of sufficient severity to warrant consideration of pacemaker treatment. In the 53 +/- 19 months prior to pacing, patients had experienced an approximate syncope burden of 1.2 events/month. During follow-up of 192 +/- 160 days, syncope recurred in 4 patients (approximate syncope burden, 0.3 events/month, p < 0.05 vs. pre-pacing), and pre-syncope in 5 patients. In these patients, rate-drop response parameters were initially set based on electrocardiographic and/or tilt-table recordings, and were re-programmed at least once in 14 (58%) individuals. A 20 beat/min window height (top rate minus bottom rate), a window width of 10 beats (61% of patients), and 2 or 3 confirmation beats (79% of patients) appeared to be appropriate in most patients. Treatment intervention rate was set to > 100 beats/min in 89% of patients, with a duration of 1 to 2 min in 79%. In conclusion, a narrow range of rate-drop response parameter settings appeared to be effective for most individuals in this group of highly symptomatic patients.

Preliminary single center clinical experience of the use of a new implantable cardioverter defibrillator

We report a single center's preliminary clinical experience of the Sentinel (Angeion, Minneapolis, MN) implantable cardioverter defibrillator (ICD), which employs novel technologies that offer the potential for significant reduction in ICD size. Thirty-three patients have received Sentinel ICDs with a mean follow-up of 450 (range 150-1023) days. Device shock therapy has been used to defibrillate/cardiovert 43 spontaneous episodes of malignant ventricular arrhythmia and 510 episodes of hemodynamically well tolerated ventricular arrhythmia have been pace-terminated (pace-termination failed in 6 episodes with subsequent delivery of appropriate shock therapy). There has been no arrhythmic death in this patient population. There have been 9 inappropriate shocks in 6 patients (in 2 patients for atrial fibrillation which had satisfied the algorithm detection criteria for high zone ventricular arrhythmia, in 3 for sinus tachycardia [rate greater than 180 beats per min] and in 1 due to device capacitor malfunction). Device replacement has been required for component malfunction in 3 patients. There have been no other major complications. Follow-up time to date is short and longterm device efficacy and performance remain unproven. However, our early clinical experience suggests that the innovations used to manufacture the Sentinel ICD have facilitated reduction in ICD size without compromising therapeutic efficacy.

Pharmacological stress testing of the His-Purkinje system in patients with bifascicular block

This literature review, based mainly on the English-language literature, focuses on pharmacological stress testing of the His-Purkinje system as part of an invasive electrophysiological study. The main target group for this investigation is patients with bifascicular block and syncope in which intermittent high grade AV block is suspected. Several drugs have been used for this purpose, mainly Class I antiarrhythmic agents such as ajmaline, procainamide, disopyramide, and flecainide. Most studies, unfortunately, suffer from limited patient numbers, lack of adequate control groups, and/or adequate follow-up. The sensitivity of the disopyramide stress test has been shown to be 75%-100% for prediction of impending high grade AV block. The specificity was > 90%. Studies on procainamide have shown a sensitivity of 60% but the specificity has not been assessed. There are no studies allowing a strict comparison of the diagnostic value of pharmacological provocation with different drugs. Based on the similarities of the electrophysiological effects on the His-Purkinje system of the above Class I agents, it is reasonable to assume that all of them might be of diagnostic value in the present clinical context, provided atrial and ventricular stimulation after drug is included in the protocol.

Duration of complete atrioventricular block after congenital heart disease surgery

Children with complete heart block following surgery for congenital heart diseases were prospectively followed to assess the timing for recovery of atrioventricular conduction, and to determine if there were clinical variables that reliably predict permanent heart block. Recovery of atrioventricular conduction occurred by postoperative day 9 in 97% of patients with transient heart block.

Intracardiac QRS electrogram width--an arrhythmia detection feature for implantable cardioverter defibrillators: exercise induced variation as a base for device programming

Delivery of inappropriate therapy of implantable cardioverter defibrillators (ICD) due to inaccurate arrhythmia detection represents a major clinical problem. Different arrhythmia detection criteria such as the "stability" of the cycle length or the suddenness of "onset" of tachycardia have been implemented in ICD software to prevent inappropriate therapy. The new Medtronic model 7223Cx ICD offers an additional detection parameter (QRS width), which reflects changes in the duration of ventricular depolarization as a tool to distinguish supraventricular from ventricular tachycardias. Although this criterion can be programmed based on ECG parameters derived from resting ECGs, this may not be sufficient since QRS width is subject to considerable changes due to transient myocardial ischemia, changes in autonomic tone, or frequency dependent effects of antiarrhythmic drugs. The present study aimed to determine frequency dependent changes in QRS width in individual patients at rest and during symptom-limited exercise testing in 16 patients with documented ventricular tachycardia (N = 13) or ventricular fibrillation (N = 3). The optimal EGM slew threshold and the individual variation of QRS width were determined. Measurements obtained at the end of the implantation procedure were compared to those performed at hospital discharge. The majority of patients showed a wider variation in QRS duration as measured from 30 consecutive cycles during exercise as compared to rest. For example, the QRS range (i.e., the difference between the maximal and the minimal QRS width measured) averaged 7 +/- 3 ms at rest and increased to 11 +/- 3 ms during exercise (P = 0.004) with an increase of > or = 4 ms observed in 11 (69%) of 16 patients. In 13 (81%) of 16 patients a reprogramming of at least one QRS width parameter from its value at the time of implantation was necessary. Thus, the QRS width measured from the intracardiac EGM shows significant intraindividual variations in different physiological conditions. For optimal programming of the QRS width parameter, measurements obtained during exercise are important.

Sudden Wenckebach periods and their relationship to neurocardiogenic syncope

Throughout a 9-month period during which 1,125 Holter tapes were reviewed prospectively we identified 13 nonmedicated patients with an arrhythmia, which for the purposes of this presentation was categorized, because of their mode of initiation, as sudden Wenckebach periods (WP). The episodes emerged abruptly from a normal (< or = 200 ms) PR interval with sudden prolongation of PR and PP intervals (and reversed PR-RP relationship) that took place over 1-8 cycles. The postpaced PR interval was shorter than that of the last conducted beat. The episodes were separated into two groups. Group I included 11 patients with symptoms other than syncope and Group II included 2 patients with syncope. There were 26 episodes of sudden WP in Group I. Twenty-five terminated in a single (and one in double) blocked P waves. Most episodes occurred between 10 PM and 7 AM. Symptoms did not correlate with the episodes. Mean 24-hour rates were < 90. In Group II there were 22 episodes, all occurring between 6 AM and 10 PM. The mean sinus cycle lengths before the phenomenon started to occur in Group I (861 +/- 185 ms) as well as the cycle lengths at the onset of block (1,096 +/- 215 ms) were statistically longer than those in Group II (591 +/- 40 ms and 747 +/- 63 ms, respectively, P < 0.0001). Although the mode of onset in the episodes in Group II was similar to Group I, 16 episodes terminated in 2-6 blocked P waves. Thus, the entire number of episodes could be categorized as an unusual type (because of the PR prolongation) of paroxysmal, or advanced second degree AV block. Because these patients had negative electrophysiological studies, positive tilt tests, and absent syncope after oral propranolol therapy, they were considered as having neurocardiogenic syncope. In addition, the faster than normal (> 100) mean 24-hour rates) suggested that they also had so-called inappropriate sinus tachycardia. In summary, Group I consisted of patients with a normal, benign, vagal-induced second-degree AV block, whereas the Holter findings in Group II appeared to reflect unusual (but natural, i.e., nonprovoked) electrocardiographic manifestations of certain patients with neurocardiogenic syncope.

The development of sinoatrial dysfunction in pacemaker patients with isolated atrioventricular block

The purpose of this paper is the assessment of sinus node competence over time in patients with isolated atrioventricular block (AV block). Patients implanted with AV synchronous pacemakers for isolated AV block between December 1993 and June 1995 were prospectively evaluated at predischarge, 6 weeks, and subsequent 6 months follow-up with respect to atrial rate monitors/24-hour Holter and modified exercise test. Patients unable to maintain AV synchronous pacing or complete a modified exercise test were excluded. Sinus node competency is interpreted as: (1) absence of atrial brady- or tachyarrhythmia, (2) ability to achieve a minimum heart rate of 100 beats/min with modified exercise test or during daily activities. There were 58 patients (22 women), mean age 71.0 +/- 13.8 with an average follow-up of 30.4 months (11-40). Three patients did not complete a modified exercise test, 4 patients were lost to follow-up, and 2 patients were unable to maintain AV synchronous pacing. Of the remaining 49 patients, 3 developed chronic or paroxysmal atrial fibrillation. No patient developed significant bradyarrhythmias. All patients achieved a heart rate of > or = 100 beats/min modified exercise test. In our group of patients with isolated AV block within a moderate follow-up period, development of sinoatrial dysfunction was rare (6%). A longer follow-up is required to delineate the natural history of sinoatrial dysfunction in patients with isolated AV block.

Sex differences in selection of pacemakers: retrospective observational study

OBJECTIVE

To evaluate the effect of patients' sex on selection of pacemakers.

DESIGN

Retrospective univariate and multivariate analysis of a large database.

SETTING

German central pacemaker register.

SUBJECTS

Records collected at the register for 1992 and 1993 (n=31 913), covering 64% of all implantations in Germany.

MAIN OUTCOME MEASURE

Probability of receiving a single chamber, dual chamber, or rate responsive pacemaker in relation to sex.

RESULTS

Univariate analysis showed that women were more likely to receive single chamber pacemakers and less likely to receive dual chamber or rate responsive systems than men. After demographic and clinical variables were controlled for, women were still more likely to receive a single chamber system (atrial pacing: odds ratio 0.89, 95% confidence interval 0.74 to 1.07; ventricular pacing: 0.85, 0.80 to 0.92) and less likely to receive a dual chamber (1.20, 1.12 to 1.30) or a rate responsive system (1.26, 1.17 to 1.37) than men.

CONCLUSIONS

The data suggest sex differences in the selection of a pacemaker system which cannot be explained by the underlying cardiac disorder. Further research is needed to evaluate why guidelines for implanting pacemakers are not better adhered to.

[National Registry of Automatic Implantable Defibrillators in 1996]

The results of the Spanish Registry of Automatic Defibrillators implanted between February 1996 and January 1997 are reported. A questionnaire per patient was completed by every implanting physician, in every center. The questionnaire was designed by the Section of Electrophysiology and Arrhythmias of the Spanish Society of Cardiology. The data from 306 automatic defibrillators implanted were reported. The percentage of defibrillators per inhabitant in Spain is close to 1 per 100,000. Eighty-five percent were first implants, while a 13% were replacements. Most of the electrodes used were endocardial. Chronic ischemic heart disease was found in 54% of the patients. Forty-six percent of the patients had syncopal ventricular tachycardia, 31% ventricular fibrillation and 23% sustained monomorphic ventricular tachycardia. The generator pocket was pectoral in 87% of the patients and abdominal in 13%. The implant of the defibrillator was associated with other cardiac surgery in only 3% of the patients.

Implantable cardioverter defibrillators

Implantable cardioverter defibrillators have proven to be an effective therapy for life-threatening ventricular arrhythmias. Given the ever-increasing number of patients who have these devices, increasing numbers of patients are likely to present to emergency departments with defibrillator-related problems. This article discusses normal device function, indications for implantation, and technique of implantation. It also focuses on the evaluation and management of patients with these devices presenting to the emergency department.

Permanent cardiac pacing

Implantation of a permanent pacemaker is the most commonly performed surgical operation involving the heart. The modern cardiac pacemaker is a complex device that can sense and pace in both the atrium and ventricle. It also modulates the pacing rate based on sensed physiologic parameters. This article reviews the fundamental principles of pacemaker technology and provides the emergency physician with approaches to common pacemaker problems.

[Current indications for implantable automatic defibrillators]

Since the first implantation in man in 1980 implantable cardioverter defibrillator technology has greatly improved and the number of devices implanted has increased considerably in recent years. Non-thoracotomy lead systems and biphasic shocks are now the approach of choice, offering nearly a 100% success rate. This paper version reviews the current indications for the implantation of implantable cardioverter defibrillator and is an upgraded of an article previously published by the Arrhythmia's Section of the Spanish Society of Cardiology. Recommendations for qualification of centres implanting defibrillators and follow up are also addressed.

Effect of dual-chamber pacing with automatic rate-drop sensing on recurrent neurally mediated syncope

We tested the hypotheses that a dual-chamber pacemaker that paces when intrinsic rate drops abruptly would reduce the number of syncopal spells and improve the quality of life in patients with highly recurrent neurally mediated syncope. Twelve patients with highly frequent neurally mediated syncope and at least 1 syncopal spell after tilt testing received dual-chamber pacemakers with automatic rate-drop sensing. The pacemakers were implanted 17+/-26 months after tilt testing, and the patients then were followed for 12+/-2 months. We compared the time to the first recurrence of syncope, syncope frequency, and quality of life for the 2 periods between tilt testing and pacemaker implantation, and between implantation and last follow-up. Only 6 of 12 patients fainted after pacemaker insertion. The median time to syncope recurrence before and after pacing was 7 days and 5.3 months, respectively. The geometric mean frequency of faints before and after pacing was 5.0 spells/month (95% confidence interval 2.7 to 9.2) and 0.30 spells/month (95% confidence interval 0.2 to 0.4), p <0.001. After 6 months the mean perception of health on the 100-point EuroQol scale rose from 55 to 82 (p = 0.003), and the general health perception on the SF-36 scale rose from 51 to 72 (p = 0.005). Permanent dual-chamber pacing with automatic rate-drop sensing in patients with highly frequent syncope is associated with a marked reduction in the likelihood of syncope and a marked improvement in quality of life.