Incidence of newly detected atrial arrhythmias via implantable devices in patients with a history of thromboembolic events.

BACKGROUND AND PURPOSE: Evidence of atrial tachycardia/atrial fibrillation (AT/AF) is often sought in patients with ischemic stroke or transient ischemic attack. We studied patients with previous thromboembolic events (TE) who were implanted with devices capable of continuous arrhythmia monitoring to comprehensively quantify the incidence and duration of newly detected AT/AF. METHODS: This study represents a subgroup analysis of the TRENDS trial, which included patients with clinical indications for pacemakers or defibrillators and >or=1 stroke risk factors (heart failure, hypertension, age 65 or older, diabetes, or previous TE). A history of AF was not required. All implanted devices were capable of continuously monitoring the cumulative time spent in AT/AF each day. This analysis focuses primarily on the incidence and duration of newly detected AT/AF (defined as >or=5 minutes of AT/AF on any day) in patients with previous TE, no documented history of AF, and no warfarin or antiarrhythmic drug use. RESULTS: A total of 319 patients had a history of TE and >or=1 day of device data. Patients with a documented history of AF (n=80), warfarin use (n=56), or antiarrhythmic drug use (n=20) were excluded from analysis. Of the remaining 163 patients, newly detected AT/AF was identified via the device in 45 patients (28%) over a mean follow-up of 1.1+/-0.7 years. AT/AF recurred infrequently, with only 12 patients experiencing AT/AF on >10% of follow-up days. CONCLUSIONS: Newly detected episodes of AT/AF were found via continuous monitoring in 28% of patients with previous TE. Most episodes would not have been detected by standard intermittent monitoring techniques.

Rationale and design of a prospective study of the clinical significance of atrial arrhythmias detected by implanted device diagnostics: the TRENDS study.

BACKGROUND: Sustained atrial fibrillation (AF) is a common risk factor for stroke. While intermittent AF also appears to pose a substantial stroke risk, the quantitative relationship between the percentage of time spent in AF and stroke risk is poorly specified and "intermittent" AF is not the same as paroxysmal AF. Improved assessment of the impact of AF burden on stroke risk will allow more targeted and safer use of antithrombotic therapy. METHODS AND RESULTS: The primary objective of this study is to determine if AT/AF (all device detected atrial tachyarrhythmias, including atrial flutter, atrial fibrillation, and atrial tachycardia) burden over a 30 day period is an independent predictor of the occurrence of ischemic stroke, transient ischemic attack (TIA) and/or systemic embolism in subjects not receiving anticoagulation therapy. TRENDS is a prospective, post-market, non-randomized, multicenter study designed to enroll 3100 subjects who have an independent Class I/II indication for cardiac rhythm device implantation and who have demographic features suggestive of an increased risk for thromboembolic complications related to AT/AF. All implanted devices will have the ability to collect long-term AT/AF burden trending data and will be equivalently programmed to ensure consistent data collection. All subjects will be followed with device interrogations every 3 months and clinic visits every 6 months for 1 year. Subjects with a documented history of AT/AF prior to enrollment and those who develop AT/AF during the 12-month follow-up will be followed until the last subject enrolled in the study has completed their 24-month follow-up. CONCLUSIONS: The results of the TRENDS study should help clarify the implications of data retrieved from an implantable device with regard to the risk for thromboembolic complications from atrial arrhythmias, even in the absence of symptoms.

Experimental determination of adult and pediatric neck scale factors.

The purpose of this study was to determine scale factors for small, mid-size and large adults using a caprine model. In a previous study conducted in our lab, scaling relationships were developed to define cervical spine tolerance values of children using caprine specimens. In that study, tolerances were normalized with respect to an average adult. Because airbag-related injuries are associated with out-of-position children and small adult females, additional experimental data are needed to better estimate human tolerance. In the present study, cervical spine radiographs from the 5th, 50th and 95th percentile human adults were used to determine vertebral body heights for small, mid-size and large anthropometries. Mean human vertebral body heights were computed for each anthropometry and were normalized with respect to mid-size anthropometry. Similar measurements were calculated from caprine cervical spine radiographs and each caprine specimen was grouped into one of the three categories based upon vertebral body size. Seventy-two motion segments (OC-C2, C3-C4, C5-C6 and C7-T1) from 18 adult caprine cadavers were subjected to pure moment and distraction loads. Pure moment testing resulted in bending stiffness, and distraction testing resulted in failure force and linear stiffness. Data were normalized with respect to the mid-size anthropometric category. For the small, mid-size and large adult categories, tensile failure force yielded scaling ratios of 0.74, 1.00 and 1.13, linear stiffness yielded ratios of 0.78, 1.00 and 1.10 and bending stiffness resulted in ratios of 0.89, 1.00 and 1.03. For the one-year-old, three-year-old, six-year-old and 12-year-old, scaling ratios were 0.10, 0.16, 0.30 and 0.62 for the tension force, 0.13, 0.18, 0.38 and 0.66 for the linear stiffness and 0.13, 0.19, 0.42 and 0.76 for the bending stiffness. These scale factors are compared with FMVSS 208.