Peter N. Smith

A population-based study of mortality among patients with atrial fibrillation or flutter

PURPOSE To determine the mortality associated with atrial flutter and atrial fibrillation in the general population. SUBJECTS AND METHODS Using the Marshfield Epidemiologic Study Area, a database that captures nearly all medical care and deaths among its 58,820 residents, we identified patients diagnosed with atrial flutter or atrial fibrillation from July 1, 1991, through June 30, 1995. Patients were followed prospectively and compared with a group of controls without these arrhythmias. RESULTS A total of 4775 person-years of follow-up were completed in 577 patients and 577 controls. Compared with controls, mortality among patients with atrial fibrillation or flutter was nearly 7.8-fold higher at 6 months (95% confidence interval [CI]: 4.1 to 15) and 2.5-fold higher (95% CI: 2.0 to 3.1; P < 0.0001) at the last follow-up (mean [+/- SD] of 3.6 +/- 2.3 years; range, 1 day to 7.3 years). At 6 months, mortality among patients with atrial flutter alone was somewhat greater than in controls and less than one third that of those with atrial fibrillation (with or without atrial flutter) (P = 0.02). At the last follow-up, however, mortality was greater among patients with atrial flutter (hazard ratio [HR] = 1.7; 95% CI: 1.2 to 2.6; P = 0.007), atrial fibrillation (HR = 2.4; 95% CI: 1.9 to 3.1; P < 0.0001), or both atrial arrhythmias (HR = 2.5; 95% CI: 1.9 to 3.3; P < 0.0001) when compared with controls in models that adjusted for cardiovascular risk factors. CONCLUSION In the general population, both atrial flutter and atrial fibrillation are independent predictors of increased late mortality. The relatively benign course during the 6-month period after the initial diagnosis of atrial flutter suggests that early diagnosis and treatment of these patients may improve their long-term survival.

Infections with Nonthoracotomy Implantable Cardioverter Defibrillators: Can These Be Prevented?

Nonthoracotomy ICDs are believed to be the best therapeutic modality for treatment of life‐threatening ventricular arrhythmias. Little is known about the risk of infection with initial implantation of these devices. We studied the incidence, clinical characteristics, and risk factors associated with infections in 1,831 patients with nonthoracotomy ICD from the Endotak‐C nonthoracotomy lead registry of Cardiac Pacemakers, Inc. A transvenous lead was implanted in 950 patients (51.9%) and a combination transvenous plus subcutaneous patch was used in 881 patients (48.1%). Nine preselected data variables were studied, and all investigators identified as having patients with infections were personally contacted. Infections occurred in 22 (1.2%) of 1,831 patients receiving this nonthoracotomy ICD system. The mean time to infection was 5.7 ± 6.5 months (range 1–25 months). Staphylococci were isolated in 58% of patients with reported infection. The presence of a subcutaneous defibrillator patch system was associated with the development of infection. Six of 950 patients (0.63%) with a totally transvenous lead system developed infection versus 16 of 838 (1.9%) patients with a transvenous lead plus subcutaneous patch system configuration (P = 0.015, Chi‐square test), with an unadjusted estimated odds ratio of 3.06 (CI 1.19–7.86). The risk of infection encountered with the nonthoracotomy ICD is low, estimated from our data to be 1.2%. Placement of a subcutaneous defibrillator patch appears to be an independent risk factor for development of infection.

Familial Atrioventricular Nodal Reentry Tachycardia

Dual atrioventricular nodal pathways, the substrate responsible for atrioventricular node reentry tachycardia (AVNRT), are thought to be randomly occurring congenital anomalies. This article describes 14 patients in six families, each with two or three first‐degree relatives with paroxysmal supraventricular tachycardia. Electrophysiological evidence of dual atrioventricular nodal pathways was established in all 13 patients studied, AVNRT was induced in 12 (92%), and radiofrequency ablation of the slow pathway was curative in all cases. The data suggest a hereditary contribution to the development of atrioventricular nodal pathways and AVNRT. The pattern of inheritance appears to be autosomal dominant. (PACE 2004; 27:73–76)

Atrial Flutter Versus Atrial Fibrillation in a General Population: Differences in Comorbidities Associated With Their Respective Onset

Objective: Determine and compare the prevalence of known risk factors for cardiovascular disease among unselected individuals presenting with their first ever episode of atrial flutter (AFL) and atrial fibrillation (AF). Study Design and Setting: We evaluated 11 pre-selected clinical variables including age, sex, smoking history and other potential cardiac risk factors. Using the resources of the Marshfield Epidemiologic Study Area, a population-based database, all newly diagnosed cases of either AFL or AF in the region during a 4-year period were identified. Results: Among the 472 incident cases, 76 (16.1%) had AFL and 396 (83.9%) had AF. Compared to those with AF, subjects with AFL were more likely to have had a history of chronic obstructive pulmonary disease (25% vs. 12%, P = 0.006), heart failure (28% vs. 17%, P = 0.05), and smoking (49% vs. 37%, P = 0.06). Hypertension, on the other hand, was more common among individuals with AF (63% vs. 47%, P = 0.01). Conclusion: This study represents the first report to evaluate potential differences in the conditions associated with the development of AFL versus AF. Research into the mechanisms of atrial arrhythmogenesis may lead to improved preventive and therapeutic interventions.

Catheter Ablation in the Elderly in the United States: Use in the Medicare Population from 1991 to 1998

SMITH, P.N., et al.: Catheter Ablation in the Elderly in the United States: Use in the Medicare Population from 1991 to 1998. The safety and efficacy of catheter ablation for the treatment of drug refractory cardiac arrhythmias is well established in young patients. Little is known about its effectiveness or use in the elderly. We determined trends in the use of catheter ablation in the United States Medicare population. Data were obtained from the approximately 30 million patients covered each year by Medicares fee‐for‐service program of the Health Care Financing Administration of the Department of Health and Human Services. From 1991 to 1998, Medicares fee‐for‐service beneficiaries covered 80%–93% of all adults > 65 years old in the United States. All catheter‐based ablative procedures performed in this population were identified through the use of the Current Procedural Terminology codes 93650, 93651, and 93652. Use rate per 1 million beneficiaries grew from 33 in 1991 to 603 in 1998. While during this 7‐year period the Medicare fee‐for‐service population decreased by 8%, ablations increased 16‐fold (1,608%). The use of catheter ablation in the older American grew exponentially during the 1990s. Further research is needed to determine the optimal use of this potentially curative technique in the elderly.

998-61 Population Prevalence of Wolff-Parkinson-White Syndrome

Little is known about the epidemiology of Wolff-Parkinson-White (WPW) syndrome in the general population. Virtually all previous studies have been either case series from tertiary care centers or limited to young adult males screened for military training. To date, there are no detailed studies of the prevalence of WPW in the general population. To determine the prevalence of WPW in the general population, we used the Marshfield Epidemiologic Study Area (MESA), a population laboratory of 50,000 people residing in 12 contiguous zip codes in central Wisconsin. Prevalence was determined as of 7/1/91 among MESA residents who had a diagnosis of WPW between 1/1/79 and 6/30/91. Cases were identified by reviewing the medical records and electrocardiograms of: a) all 32 MESA residents with the WPW diagnosis identified by International Classification of Diseases, 9th Revision (ICD-9) Code 426.7 as a hospital discharge or outpatient clinic diagnosis, b) 600 patients with suspected supraventricular arrhythmias identified by three ICD 9 codes, and c) all patients who had an invasive electrophysiology study for overt WPW syndrome in our institution over the last 10 years. Results We identified 25 prevalent cases of WPW resulting in an overall population prevalence of 5.1/10,000 (95% C.I., 3.1–7.1). Age specific-prevalence rates per 10,000 were: 0–19 years –2.0; 20–39 years –5.5; 40–59 years –9.6; g 60 years –4.8. There was no significant difference in males versus females. Al1 25 verified cases were identified from the 32 potential cases with ICD-9 Code 426.7, indicating that this code is 100% sensitive and has a 78% positive predictive value for WPW syndrome. Conclusions 1) The prevalence of WPW in the general population is lower than that reported in selected populations and appears to be highest in those of late middle-age. 2) Based on the findings of our study, we estimate that there are approximately 130,000 individuals in the United States with electrocardiographic documentation of WPW.

Usefulness of placement of intraoperative epicardial wires during automatic implantable cardioverter-defibrillator insertion to preclude the need for transvenous catheters at the predischarge electrophysiology study

Abstract The management of ventricular tachyarrhythmias and sudden cardiac death has changed remarkably since the advent of the automatic implantable cardioverter-defibrillator (AICD). 1–6 In patients undergoing implantation of the AICD, postoperative testing is used to judge the efficacy of the device. In the past, the predischarge study has required placement of transvenous pacing catheters in order to induce clinical arrhythmias. We evaluated the reliability of induction of ventricular tachyarrhythmias in the postoperative period using temporary epicardial pacing wires placed during AICD implatation.