Demosthenes Iskos

Usefulness of pindolol in neurocardiogenic syncope

We prospectively studied the efficacy of pindolol, a beta-adrenergic blocker with intrinsic sympathomimetic activity (ISA), for the prevention of syncope recurrences in 31 patients with recurrent neurocardiogenic syncope. Pindolol proved to be an effective treatment, even in patients who had previously failed treatment with conventional beta blockers, suggesting a clinical benefit from addition of ISA to beta blockade in this setting.

Efficacy of biphasic waveform cardioversion for atrial fibrillation and atrial flutter compared with conventional monophasic waveforms

B on extensive experience with implantable cardioverter-defibrillators and automatic external defibrillators, the utility of biphasic transthoracic shock has been demonstrated in the setting of lifethreatening ventricular tachyarrhythmias. These observations have led to the application of biphasic waveforms during elective transthoracic cardioversion for atrial fibrillation (AF). The present report compares cardioversion outcomes in 2 sequential groups of patients with AF undergoing transthoracic cardioversion. It was undertaken in an attempt to ascertain the extent to which biphasic waveform technique enhances transthoracic AF cardioversion success rates. • • • Records of 145 patients were reviewed. The patients were referred to our center for elective transthoracic cardioversion between January 1999 and September 2001, and had undergone this procedure in the electrophysiologic laboratory. Patients with atrial flutter (20 patients, 14%) were also included because of the similarity of the arrhythmia and the treatment required. Demographic and clinical data—including arrhythmia type and duration, underlying disease, and concomitant medications—were documented, along with echocardiographic data including left atrial diameter and left ventricular ejection fraction. Procedural data—including the number of cardioversion attempts made, energy levels used, and anesthetic employed— were documented. Similarly, complications were recorded, particularly skin irritation. A successful cardioversion procedure was defined as restoration of sinus rhythm for 1 cycle after energy application. Recurrence of the arrhythmia 2 hours after a successful cardioversion (i.e., before the patient left the observation unit) was deemed an “early recurrence.” The statistical significance of the efficacy of biphasic waveform cardioversion compared with monophasic waveform shock cardioversion was evaluated using chi-square and Fisher’s exact tests. A p value of 0.05 was considered statistically significant. Data were obtained in 145 sequential patients who underwent elective electrical cardioversion for AF or atrial flutter. Eighty-two patients (mean age 67 15 years) received biphasic waveform cardioversion, and the remaining 63 patients (mean age 66 14 years) underwent cardioversion with a monophasic waveform device. The ratio of men to women was 1.8:1 and 2:1 for the biphasic and monophasic waveform cardioversion study groups, respectively. The presenting arrhythmia was AF in 70 patients (85%) in the biphasic group and in 55 patients (87%) in the monophasic group. Atrial flutter was present in 12 patients (15%) in the biphasic group and in 8 patients (13%) in the monophasic group. The mean duration of patients’ treatment for the arrhythmia event was 36 56 and 60 106 days (p NS) for the biphasic and monophasic groups, respectively. Baseline clinical characteristics for patients in each treatment group are listed in Table 1. Underlying disease processes (i.e., cardiomyopathy, coronary artery disease, valvular heart disease, lung disease, and other structural heart disease) were found to be similarly prevalent in both treatment groups. Patients in the monophasic waveform group tended to use more digoxin, amiodarone, and other antiarrhythmic medications compared with biphasic group patients. The frequencies of usage of blockers, calcium channel blockers, and angiotensin-converting enzyme inhibitors were similar in both groups. The mean left atrial diameter was 46 10 mm in the biphasic group and 45 12 mm in the monophasic waveform group. Mean left ventricular ejection fraction was similar for the biphasic and monophasic groups (49 13% and 49 15%, respectively). Procedure success rate was 99% (81 patients) in the biphasic waveform cardioversion group compared with 81% (51 patients) in the group treated with monophasic waveform (p 0.001). The mean energy required for procedural success was 126 46 J and 228 83 J for the biphasic and monophasic waveform groups, respectively (p 0.001). The mean number of attempts before achieving procedural success was 1.3 0.8 for the biphasic cardioversion group and 1.2 0.4 for the monophasic cardioversion group. The treated arrhythmia recurred in 10 biphasic group patients (12%) and in 6 monophasic group patients (12%). All recurrences were in patients with AF. Skin irritation was not observed in any of the patients who received biphasic waveform shock, whereas 2 patients (3%) who received monophasic waveform shock required topical treatment for irritation at patch sites. • • • From the Cardiac Arrhythmia Center, Cardiovascular Division, Department of Medicine, Minneapolis, Minnesota. Dr. Ermis is supported in part by a grant from the Midwest Arrhythmia Research Foundation, Minneapolis, Minnesota. Dr. Benditt’s address is: Cardiac Arrhythmia Center, MMC 508, 420 Delaware Street, Minneapolis, Minnesota 55455. Manuscript received April 9, 2002; revised manuscript received and accepted June 7, 2002.

Resumption of motor vehicle operation in vasovagal fainters

This study surveyed current practice patterns with respect to the manner by which cardiac arrhythmia specialists advise patients with vasovagal syncope regarding resumption of motor vehicle operation. Among 66 physician-respondents from 9 countries, 98% indicated that they rely on tilt-table testing to establish a diagnosis, and, if an effective treatment is found based on serial tilt-table testing, they recommend a 6- to 7-week symptom-free waiting period before advising return to driving.

Prehospital Discharge Defibrillation Testing in ICD Recipients: A Prospective Study Based on Cost Analysis

Prehospital discharge defibrillation testing is often performed to verify the function of newly implanted cardioverter defibrillators (ICDs). To determine whether elimination of predischarge testing could reduce costs without placing patients at additional risk, 31 patients were randomized in this prospective clinical evaluation to either receive or not receive a predischarge ICD defibrillation test. Expenses associated with postimplant care was the primary endpoint. All patients underwent induction of ventricular fibrillation after 6 months to evaluate ICD function. The groups were well matched in terms of patient characteristics, initial lead implant parameters, and defibrillation thresholds. Elimination of prehospital discharge testing resulted in a savings of

Effect of parenteral d-sotalol on transvenous atrial defibrillation threshold in a canine model of atrial fibrillation

1,800/patient after 6 months, with no difference between groups in terms of ICD complication rates or unanticipated hospital admissions. Further studies are needed to better define the most appropriate time to assess defibrillation thresholds in the first year after implantation.

Termination of implantable pacemaker therapy: experience in five patients.

In an effort to reduce energy requirements for atrial defibrillation to a level low enough to perform painless electrical cardioversion with an implantable atrial defibrillator, we tested the hypothesis that drug therapy with the class III agent d-sotalol, when used concurrently with a low-energy shock, reduces atrial defibrillation threshold. In a nonthoracotomy canine model of atrial fibrillation, intracardiac shocks were delivered between the distal coronary sinus and the mid-right atrium. Based on a step-up energy delivery protocol the atrial defibrillation threshold was defined as the least amount of energy that resulted in a >10% and <90% rate of successful defibrillation. At a dose associated with class III antiarrhythmic effects (5 mg/kg), d-sotalol significantly reduced atrial defibrillation threshold from 1.72 +/- 1.12 J to 0.59 +/- 0.60 J (p < 0.01). These results support the feasibility of using antiarrhythmic drug therapy with d-sotalol to minimize energy requirements for intracardiac electrical cardioversion of atrial fibrillation.

Submuscular Versus Subcutaneous Pectoral Implantation of Cardioverter-Defibrillators: Effect on High Voltage Pathway Impedance and Defibrillation Efficacy

In the United States, approximately 120 000 new permanent pacemakers are implanted and 40 000 are replaced annually [1-3]. Guidelines for the implantation of new permanent pacemakers have been established by a task force from the American College of Cardiology and the American Heart Association [4] and by the British Pacing and Electrophysiology Group [5]. On the basis of specific clinical findings, these guidelines direct physicians to divide patients who are being considered for a permanent pacemaker into three classes: class I (patients in whom pacing is considered necessary), class II (patients in whom pacing is controversial), and class III (patients in whom pacing is unnecessary) [4]. However, no guidelines currently address if, when, and how cardiac pacing should be terminated. If the battery of a pacemaker becomes depleted or the device malfunctions, the conventional practice has been to replace the pacemaker or pacemaker lead without questioning the need for continued cardiac pacing. However, the clinician occasionally encounters patients referred for pacemaker replacement in whom the original indication for cardiac pacing is unclear or the pathologic process that resulted in the need for a pacemaker seems to have resolved. Moreover, pacemakers are sometimes implanted in patients who do not meet class I or class II specifications. Pacemaker replacement has the potential to cause illness. In particular, reported infection rates have ranged from 1% to 7% in patients receiving pacemakers (although rates are currently toward the lower end of this range) and are higher with reoperation [6-8]. Young patients who receive a permanent pacemaker have to undergo pacemaker replacement and lead revisions several times during their lifetime. Such patients are exposed to cumulative health risks and a substantial financial burden. Therefore, it may be appropriate to consider that some patients may not need lifelong cardiac pacing. Methods In an effort to characterize clinical scenarios in which the discontinuation of cardiac pacing might be reasonable, we retrospectively examined medical records at the University of Minnesota Hospital and attempted to identify patients in whom permanent cardiac pacing had been terminated. Five such patients were identified. These patients had been selected from approximately 80 patients who had been referred for pacemaker replacement or lead revision between 1992 and 1995. It was determined that pacemaker replacement was not necessary because of young age, presence of sinus rhythm with a narrow QRS complex on the electrocardiogram at admission, and improvement or reversal of the rhythm disturbance that led to the original implantation of the device. Results Table 1 summarizes the demographic and clinical characteristics of the five patients who were identified. These patients had a mean age of 43 years and had had cardiac pacing for a mean of 10 years (range, 9 months to 18 years). Table 1. Demographic and Clinical Characteristics of Patients Undergoing Pacemaker Removal* During removal of the pacemaker, extraction of the leads was attempted in four of the five patients (patient 1 had epicardial leads). Only gentle traction was used. The leads were easily removed in patient 4, but the leads in the other three patients had been present for several years and had adhered to the endocardium. As a result, we elected not to remove the leads from these patients because more aggressive attempts to remove them carried an unjustifiable risk. No complications related to the procedures occurred. The mean hospital stay was 2.6 days. All patients have been reassessed regularly for at least 18 months since the pacemaker was removed. No patient has had symptomatic bradycardia to warrant the reinstitution of cardiac pacing. Case Highlights Patient 1 At 34 years of age, patient 1 had patching of a ventricular septal defect. The procedure was complicated by third-degree atrioventricular block, and a dual-chamber pacemaker was implanted. Atrioventricular conduction subsequently improved. When the patient was 44 years of age, loss of capture in the ventricle was noted. The patient was referred at 45 years of age because of depletion of the pacemaker battery and frequent episodes of atrial flutter despite therapy with antiarrhythmic agents. During our evaluation, suboptimal sensing of the atrial lead was also noted. We were concerned that this suboptimal sensing, followed by inappropriate atrial pacing, might be contributing to the triggering of atrial flutter. Moreover, the patient had done well without a functioning ventricular lead for 1 year. The pacemaker was removed. In the next 2 years, the patient did not have symptoms of bradycardia but atrial flutter continued to recur. The patient eventually had successful transcatheter ablation of the flutter circuit. Patient 3 At 19 years of age, patient 3 developed third-degree atrioventricular block after cardiac surgery for the correction of complex congenital heart disease. At 37 years of age, he presented with twitching of the pectoral muscle. Electrophysiologic evaluation was done to assess the conduction system. With the patient sedated, 1:1 atrioventricular conduction was present, but conduction block in the atrioventricular node occurred during atrial pacing at a relatively slow heart rate (75 beats/min). The HV interval was 53 ms, suggesting normal conduction of the His-Purkinje system at baseline (normal range, 35 to 55 ms). Later in the study, when the patient was not sedated, conduction of the atrioventricular node improved. While the patient was receiving isoproterenol (1 g/min), 1:1 atrioventricular conduction was sustained at 180 beats/min. Conduction block in the His-Purkinje system was not seen, even after protocols with bursts of rapid atrial pacing and intravenous procainamide (1000 mg) were used concomitantly to uncover possible dysfunction of the distal conduction system. The pacemaker was subsequently removed. Patient 4 A permanent pacemaker had been implanted in patient 4 after he presented with third-degree atrioventricular block and narrow-complex escape rhythm associated with fatigue. Nine months later, at 53 years of age, the patient sought a second opinion because of rapid depletion of the pacemaker battery. An electrophysiologic evaluation was done. While the patient was sedated, atrioventricular-node block occurred at 110 beats/min during atrial pacing. The HV interval was normal (50 ms). When the effects of the sedative subsided and atropine was administered to diminish vagal effects on conduction properties, conduction of the atrioventricular node substantially improved; 1:1 conduction was sustained at 175 beats/min. Conduction block in the His-Purkinje system did not occur, even after procainamide was administered. The pacemaker was electively removed. Discussion Review of Findings The experience that we report suggests that in certain patients, long-term cardiac pacing can be safely discontinued. Despite differences in underlying cardiovascular disease, the patients in our series shared certain features. They were all relatively young and were referred because of battery depletion or a pacing-related complication. At the time of evaluation, all patients had sinus rhythm and a narrow QRS complex. Several techniques were used to confirm the presence of an appropriate natural rhythm before and after removal of the pacemaker. Ambulatory electrocardiography (using event and Holter monitors) was done before the procedure when the pacing rate had been reduced to a safe minimum (30 to 40 beats/min) and after the procedure; using this method, recurrent symptoms could be correlated with the underlying heart rate. Electrophysiologic assessment of the conduction system was done in patients 3 and 4. Patients 2 and 5 had pacemakers that could keep track of the number of times a pacing stimulus was released or a native complex was sensed. This feature permitted an assessment of the degree to which the device was used for a specific time. All patients were followed closely after pacemaker removal for symptoms that suggested recurrence of bradycardia. Terminating Cardiac Pacing The decision to discontinue long-term cardiac pacing is difficult to make for several reasons. Available clinical tools for evaluating dysfunction of the sinus and atrioventricular nodes are not optimally sensitive for detecting the progression or regression of electric disease. Moreover, the natural history of some bradyarrhythmias that require cardiac pacing may be unpredictable. Finally, recurrence of bradycardia after pacemaker removal carries the risk for substantial illness and perhaps even death. Thus, when compared with the termination of other long-term therapies (such as digoxin in patients with heart failure), discontinuation of cardiac pacing may have a smaller margin for error and greater exposure to legal risk. On the other hand, the cost and health risks of long-term cardiac pacing can be substantial. Therefore, our challenge is to identify the patients who would be least served by the replacement of a permanent pacemaker. Although our data are limited by referral bias and a relatively small patient population, we estimate that 2% to 4% of patients whose pacemakers are being replaced may not require permanent cardiac pacing. Reassessment of the need for permanent cardiac pacing may be considered in patients who received their device for a class III indication [4], who continue to have the same symptoms despite an appropriately functioning pacemaker, or who seem to have had a reversal of the process that originally led to the need for cardiac pacing. Reversible dysfunction of the sinus or atrioventricular nodes has been described in various disease states. Potentially reversible causes of bradycardia that have been reported [9-19] include electrolyte disturbances, severe hypoxia, use of pharmacologic agents (almost all antiarrhythmic agents), cardiac su

'Sagging heart syndrome': A cause of acute lead dislodgment in two patients

Implantable cardioverter-defibrillator (ICD) pulse generators are now routinely positioned in a pectoral location, either submuscularly (under the pectoralis muscles) or subcutaneously (over the pectoralis muscles). Furthermore, in current ICDs, the generator shield usually participates in the defibrillation energy pathway (“hot can”). Consequently, the precise generator location could affect defibrillation system efficacy. To assess this issue, we compared high voltage pathway impedance and defibrillation threshold (DFT) in 20 patients undergoing submuscular and 46 patients undergoing subcutaneous pectoral implantation of an Angeion Sentinel>® ICD and an AngeFlex® dual-coil defibrillation lead. Measurements were performed at time of ICD implant, pre-hospital discharge, and 1, 3 and/or 6 months later. Following induction of ventricular fibrillation, 569 biphasic waveform shocks were delivered between the generator shield and either the distal defibrillation coil (RV/can configuration) or both proximal and distal coils (RV/SVC/can configuration). Impedance differences between submuscular and subcutaneous implants were approximately 3–4 Ohms (p value of 0.132 to <0.001 depending on time of follow-up and lead configuration). A significant increase in impedance over time was noted independent of implant location and lead configuration. The DFT at implant or pre-discharge was assessed in 27 individuals, and was 9.9±3.8 J in 8 patients in the submuscular group, and 7.4±3.3 J in 19 patients in the subcutaneous group (p = 0.057). In conclusion, anatomic location of a hot can ICD generator (submuscular versus subcutaneous) influences impedance to defibrillation current, but the impact is of small magnitude and does not appear to result in clinically important differences in DFT.

Alternative Mechanical Methods of Cardiopulmonary Resuscitation.

Acute passive fixation atrial lead dislodgment occurred due to an unexpected and marked postural descent of the heart after permanent pacemaker implantation in two patients. Sagging of the heart in these two individuals may have been related to a history of morbid obesity followed by weight loss of over 100 pounds. Lead replacement with active fixation leads was required in both cases. The term “sagging heart syndrome” is proposed to describe this clinical entity. In certain adult populations, such as in patients with a history of significant weight loss, the “sagging heart syndrome” may represent a previously unrecognized cause of acute lead dislodgment.

Unusual Cause of Supraventricular Tachycardia After Acute Myocardial Infarction

Cardiopulmonary resuscitation (CPR) has become the standard of care for providing circulatory support to victims of cardiac arrest. However, despite its widespread acceptance, few victims ever survive to hospital admission and even fewer to hospital discharge. In hopes of improving survival rates of those suffering cardiac arrest, investigators have suggested and tested several modifications to standard CPR to optimize its hemodynamic effects. In this review, we discuss the important chest compression techniques that have been used over the past 3.5 decades which have mirrored our evolving understanding of the mechanisms underlying CPR.