N.A. Mark EstesIII

Complications of Dual Chamber Pacemaker Implantation in the Elderly

Pacemakers are frequently implanted, yet accurate prospective data on implant complications are limited. Elderly patients may be at increased risk of implant complications and are increasingly being referred for pacemaker implantation. The purpose of the present analysis was to define the incidence and possible predictors of serious complications of dual chamber permanent pacemaker implantation in the elderly. Therefore, we sought to prospectively identify the incidence and predictors of pacemaker implant complications in a large multicenter trial involving patients receiving a dual chamber pacemaker. The Pacemaker Selection in the Elderly (PASE) study was a prospective trial designed to evaluate quality of life in dual chamber pacemaker recipients age 65 years or older randomized to DDDR versus VVIR programming. In addition to being age 65 years or older, patients enrolled in this study were in normal sinus rhythm, and had standard indications for permanent pacemaker implantation. All patients received dual chamber pacemakers and were randomized to DDDR versus VVIR pacing. Pacemaker implant complications were collected on standardized forms which were completed at pacemaker implantation and during follow-up appointments. In this study of 407 patients, there were 26 complications occurring in 25 patients (6.1%). The most frequent complication was lead dislodgment which occurred in 9 patients. This was followed by pneumothorax (8 patients) and cardiac perforations (4 patients). In 18 patients (4.4%) repeat surgical procedures (including chest tubes) were required. Complications were noted prior to discharge in only 18 patients. There were no significant predictors of overall complications. Pneumothorax was more frequent in patients ≤75 years old, and was observed only in patients with subclavian venous access. In conclusion, complications from pacemaker implantation in the elderly are seen in 6.1% of patients and 4.4% of patients require a repeat surgical procedure. Other than advanced age and lower weight predicting for pneumothorax, there are no significant clinical predictors of complications

Cryoablation of the pulmonary veins using a novel balloon catheter.

Introduction. Pulmonary vein (PV) isolation has emerged as a promising technique for the treatment of patients with drug-refractory atrial fibrillation, however, the achievement of transmural lesions has remained a challenge. We evaluated the ability of a novel balloon-based cryogenic catheter system in achieving transmural lesions for PV isolation.Methods. Six pulmonary vein ostia from three excised ovine hearts and lungs were used in this study. The balloon catheter was deployed and positioned at the ostia of the PVs and a full 8-minute ablation was then performed, while the heart was bathed in a circulating bath of normal saline at 37∘. Thermocouples positioned on the endocardial (balloon surface—tissue interface) and epicardial surfaces of the ostia were used to determine whether transmural freezing was achieved.Results. The mean temperatures measured on the endocardial and epicardial tissue in six PV ablations were −38.8∘ ± 6.9∘C and −10.0∘ ± 7.5∘C, respectively. The average pulmonary vein thickness was 3.3 ± 1.4 mm.Conclusions. A novel cryoablation balloon catheter is capable of achieving transmural freezing of the pulmonary vein. The catheter has promise for future clinical therapy of atrial fibrillation.

Microwave radiometric thermometry and its potential applicability to ablative therapy.

Introduction: Current techniques for estimating catheter tip temperature in ablative therapy for cardiac arrhythmias rely on thermocouples or thermistors attached to or embedded in the tip electrode. These methods may reflect the electrode temperature rather than the tissue temperature during electrode cooling so that the highest temperature away from the ablation site may go undetected. A microwave radiometer is capable of detecting microwave radiation as a result of molecular motion. In this study, we evaluated microwave radiometric thermometry as a new technique to monitor temperature away from the electrode tip during ablative therapy utilizing a saline model.Methods and Results: A microwave radiometer antenna and fluoroptic thermometer were inserted in a test tube with circulating room temperature saline kept constant at 23.5°C while the surrounding saline bath was heated from 37°C to 70°C. For every degree rise in the warm saline bath placed either 5mm or 8mm from the radiometer antenna, the radiometer temperature changed 0.26°C and 0.14°C respectively while the fluoroptic temperature probe remained constant at 23.5°C. The radiometer temperature was highly correlated with the warm saline bath temperature (R2=0.997 for warm saline 5mm from the antenna, R2=0.991 for warm saline 8mm from the antenna).Conclusions: Microwave radiometry can estimate distant temperatures by detecting microwave electromagnetic radiation. The sensitivity of the microwave radiometer is also distance-dependent. The microwave radiometer thus serves as a promising instrument for monitoring temperatures at depth away from the catheter-electrode tip in ablative therapy for cardiac arrhythmias.

Frequent ICD Shocks due to Double Sensing in Patients with Bi-Ventricular Implantable Cardioverter Defibrillators

Biventricular pacing has emerged as a modality for treatment of patients with heart failure. Combined biventricular pacers and implantable cardioverter defibrillators offer treatment of heart failure as well as protection from sudden cardiac death. However, inappropriate ICD shocks as a result of double sensing due to widely spaced ventricular bipoles may pose a significant problem in these patients.We examined the ICD records of twenty-three patients with biventricular ICDs, and evaluated all episodes of double sensing that resulted in aborted or delivered therapy.In follow-up of 3.7 ± 2.6 months, thirty-three shocks in fifteen episodes occurred in five patients (21.7%) due to double sensing. Four patients (17.4%) had aborted shocks due to double sensing. All episodes resulting in shock occurred because of sinus tachycardia or supraventricular tachycardia above the upper programmed pacing rate of the device with resultant AV conduction and double sensing of the nonpaced ventricular depolarization.In conclusion, double sensing of the R-wave is a common and clinically important cause of inappropriate ICD detection and shock in patients with biventricular ICDs. Appropriate programming of the ICD can prevent episodes of inappropriate shocks.

Neonatal radiofrequency catheter ablation of junctional tachycardias

Junctional tachycardias comprise several arrhythmia types with differing mechanisms, principally involving the region of the atrioventricular (A-V) junction. Neonatal radiofrequency catheter ablation has typically been reserved for life-threatening, drug-refractory cases due to the unique concerns regarding patient size and development. We performed radiofrequency catheter ablation on two neonates with incessant, rapid junctional tachycardias and hemodynamic compromise after failing conventional medical therapy. This report describes 2 neonates who underwent emergent radiofrequency catheter ablation, and compares these two patients to a larger pediatric catheter ablation patient cohort. Both neonates had an acutely successful outcome and were able to be discharged within a week of the ablation procedure. Fluoroscopy time and total procedure time were shorter in these two patients than in the course of the average pediatric catheter ablation. Though long-term developmental consequences of neonatal catheter ablation are yet unknown, in unique extreme situations, radiofrequency catheter ablation can be performed in neonates, as in older children and adults, without excessive acute morbidity.

Clinical results with catheter ablation: AV junction, atrial fibrillation and ventricular tachycardia.

With the limitations of pharmacologic and device therapies for atrial fibrillation and ventricular tachycardia, catheter ablation is assuming a larger role in the management of patients with these common arrhythmias. Multiple case series and clinical trials have helped to define the evolving role of these techniques for ablation of the atrioventricular node, atrial fibrillation, and ischemic ventricular tachycardia. Based on very low complication rates, excellent efficacy and proven outcomes with radiofrequency ablation of the atrioventricular node, this approach with permanent pacing should play a larger role in the treatment of symptomatic patients with permanent atrial fibrillation. While linear ablation of atrial fibrillation has limited clinical utility for the treatment of this common arrhythmia, the results of multiple case series of focal atrial fibrillation ablation indicate the potential for an expanding role of this curative technique. Catheter ablation techniques for ventricular tachycardia in the setting of coronary artery disease have a role as supplemental therapy to the implantable cardioverter defibrillator in patients with recurrent pharmacologically refractory ventricular arrhythmias requiring frequent device interventions.

Assessment of atrioventricular nodal physiology in the mouse.

Transgenic mice are increasingly being utilized for understanding cardiac electrophysiologic abnormalities. However, little is known about the normal atrioventricular nodal and infraHisian physiology in the mouse because of the prior inability to record a His-bundle deflection. We present the first comprehensive examination of the murine atrioventricular nodal and His-Purkinje systems employing His-bundle recordings. Normal, healthy, male C57BL/6J mice (n = 48) underwent an in vivo electrophysiology study using a 2 F octapolar electrode catheter. Effective refractory periods were determined during premature atrial and ventricular stimulation. The PR interval measured 44 ± 6 ms with a mean sinus cycle length of 185 ± 42 ms. Baseline AH intervals were 36 ± 5 ms and HV intervals were 10 ± 2 ms. At a pacing cycle length of 140 ms the atrioventricular nodal effective refractory period (AVNERP) and atrial effective refractory period (AERP) were 86 ± 19 ms and 57 ± 17 ms, respectively. The mean AV Wenckebach and 2:1 paced cycle length were 103 ± 14 ms and 84 ± 13 ms, respectively. Premature atrial stimulation curves were asymptotic without discontinuity. A subset of nine mice was studied after administration of isoproterenol. The sinus cycle length, AVNERP and AERP decreased significantly from baseline measurements. This method establishes a practical and feasible technique to record in vivo His-bundle electrograms in the mouse to assess atrioventricular nodal and infraHisian physiology. Use of this model will allow for the examination of abnormalities of atrioventricular nodal and infraHisian conduction in transgenic murine models.

The impact of defibrillator discharges on psychological functioning of implantable cardioverter defibrillator recipients.

A lag exists with respect to our understanding of the psychological demands and rehabilitation needs of individuals who have undergone implantable cardioverter defibrillator (ICD) implantation. The ICD is designed to transmit an electric shock to the heart to treat a potentially life-threatening arrhythmia. This study specifically examined the impact of defibrillator discharges on the psychological functioning of ICD recipients. A questionnaire was self-administered to 33 individuals who have been living with the ICD for at least 6 months. Results revealed that levels of anger and depression were significantly higher in those subjects who reported a lower discharge rate, while sense of well-being was significantly higher in those subjects who reported a greater discharge rate. Possible explanations for our findings were proposed as well as implications for clinical intervention were discussed.

Surgery for atrial fibrillation: current state-of-the-art.

Surgery for atrial fibrillation has been performed for two decades. In 1987, James Cox first introduced the Cox–Maze procedure. Since this time, there has been startling progress in the field of interventional therapy for atrial fibrillation. Over the last 5 years, there has been enormous renewed interest in the surgical treatment of atrial fibrillation. In large part, this has been a result of the introduction of new ablation technology, which has greatly simplified the operative approach and allowed surgeons to develop less invasive surgical techniques and more widely applicable procedures. Because of this progress, the number of surgical procedures performed for atrial fibrillation annually in the United States has skyrocketed. This special issue of the Journal of Interventional Cardiac Electrophysiology is meant to provide a summary of the current state-of-the-art of surgical therapy for atrial fibrillation. Although it is admittedly incomplete because of space limitations, it will provide the reader with a reasonable overview of the field. The first two articles deal with the lessons learned from the historical surgical experience. Dr. Richard Schuessler, who was involved in the development of the Cox–Maze procedure with Drs. Cox and Boineau, discusses mechanisms of human atrial fibrillation based on the human mapping experience. Dr. Ad then summarizes the history of the Cox–Maze procedure, and the predictors of failure. The third article has a brief overview of the different ablation devices. The rest of the issue is divided into discussions of the surgical treatment of lone atrial fibrillation, and atrial fibrillation concomitant with mitral valve, coronary artery, and congenital heart disease. Finally, a summary statement has been co-authored by us entitled “Curing Atrial Fibrillation: Two Decades of Progress.” It is hoped that this issue will advance us all toward safe and successful techniques for curing atrial fibrillation. J Interv Card Electrophysiol (2007) 20:57 DOI 10.1007/s10840-007-9174-1

The Challenge of Prediction and Prevention of Sudden Cardiac Death in Congestive Heart Failure

Congestive heart failure (CHF) is one of the few cardiovascular conditions with a clear increase in incidence and prevalence [1±4]. Multiple nonantiarrhythmic therapies have been demonstrated to prolong survival in patients with CHF including ACE inhibitors, beta-blockers and spironolactone [5±11]. With the exception of beta-blockers, most of the survival prolongation in CHF patients with pharmacological agents is secondary to nonarrhythmic risk reduction. Despite these advances, one-year mortality remains as high as 25% for those with moderately symptomatic (NYHA Class II±III) and 60% for severely symptomatic (NYHA Class IV) patients. It is estimated that up to 50% of total mortality in patients with heart failure is attributable to sudden death [1±4]. By de®nition, this refers to unexpected natural death from a cardiac cause within 1 hour from the onset of symptoms in a patient without any prior condition [4]. Some studies indicate that a higher proportion of mortality in CHF patients is attributable to sudden death in milder forms of heart failure (NYHA Class I and II) with heart failure deaths causing a greater proportion of morality in the more advanced stages of the disease [1±4]. With this background it is appropriate to consider whether completed or ongoing trials evaluating antiarrhythmic drugs or implantable cardioverter de®brillators (ICDs) in patients with CHF are likely to improve survival at an acceptable cost. Because most of the patients who experience sudden cardiac arrest are not successfully resuscitated, primary prevention of sudden death in patients with CHF remains a particular challenge. Although primary prevention generally refers to prevention of an underlying cardiovascular condition, when used in the context of prediction and prevention of sudden cardiac death it refers to prevention of ventricular tachycardia or ventricular ®brillation. By contrast, secondary prevention of arrhythmias refers to prevention of recurrent cardiac arrest. Risk strati®cation to identify those most susceptible to arrhythmic death lacks precision. The major predictors of cardiovascular death in CHF patients are primarily related to clinical status, ventricular function and ventricular arrhythmias [12±14]. A number of noninvasive risk strati®cation techniques have been suggested as providing useful information in patients with CHF. Among these are left ventricular ejection fraction (LVEF) [12±16], presence of nonsustained ventricular tachycardia (NSVT), and inducible sustained ventricular tachyarrhythmias in the presence of coronary artery disease. Based on several recent trials, the best established prognostic test in patients with CHF in the setting of ischemic heart disease, is inducible sustained ventricular tachycardia [17±19]. Unfortunately, the positive predictive valve of noninvasive testing is limited in patients with CHF of ischemic or nonischemic origin. The signal-averaged electrocardiogram has a poor positive predictive valve for sudden cardiac death in patients with heart failure due to ischemic or nonischemic causes [15]. Despite the better negative predictive value of the technique, especially for patients with ischemic heart disease, most clinicians do not use this technique of risk strati®cation due to the absence of any bene®cial intervention based on the results. Heart rate variability has also been assessed as a potential marker risk for sudden death in patients with heart failure [15,16]. This technique assesses the beat-to-beat variation in heart rate, which is determined by the status of the autonomic nervous system. Heart rate variability has been shown to change inversely with the degree of heart failure [15,16]. It also predicts total mortality in this condition but does not have