Sensing performance of a new wireless implantable loop recorder: a 12-month follow up study.

BACKGROUND: The implantable loop recorder (ILR) is a cost-effective tool with a high diagnostic yield in the evaluation of unexplained recurrent syncope. The Sleuth ILR (Transoma Medical, St. Paul MN, USA) is a new-generation ILR with wireless transmission capability approved by the Food and Drug Administration. We report the feasibility of achieving appropriate sensing over 1-year follow-up at the traditional midclavicular and alternative inframammary implantation sites without preimplant electrocardiogram (ECG) mapping. METHODS AND RESULTS: We studied 32 patients with unexplained syncope, aged 58.4+/-18.44 years, with an ILR implanted at the left midclavicular location (n = 17) or the left inframammary site (n = 15) over 1-year post implant. No preimplant electrocardiogram (ECG) mapping was performed. The highest R-wave amplitudes were observed at the inframammary site, but over the entire follow-up period, amplitudes were not significantly different from those at the midclavicular site. At both sites, R-wave amplitudes at the 6-month follow-up were significantly higher than those measured at 1 week. P-waves were visible in 80-90% of the patients. There was no discernible difference in P-waves (amplitude) relative to implant location. Body mass index, left ventricular ejection fraction, and age did not significantly influence the R-wave amplitude or the ability to discern P-waves. CONCLUSION: Our findings show that the Sleuth ILR implanted at both the midclavicular and inframammary locations without preimplant ECG mapping achieves acceptable "R" waves. This may simplify implantation procedures and improve patient satisfaction.

Hemodynamic and surface electrocardiographic effects of a new aqueous formulation of intravenous amiodarone.

Intravenous amiodarone is an effective antiarrhythmic agent. However, the standard formulation (Cordarone IV) frequently causes hypotension. Hemodynamic studies have attributed this adverse effect to the solvents employed. A newly developed aqueous formulation (Amio-Aqueous) lacks solvents and thus may not causes hypotension. This study evaluated the hemodynamic effects in a cardiac catheterization laboratory. Two boluses of 150-mg aqueous amiodarone were administered via a peripheral vein to 32 hemodynamically stable patients who underwent cardiac catheterization. Boluses were administered initially over 2 to 5 minutes and in the last 9 patients over 2 minutes. Hemodynamic evaluation was performed and 12-lead electrocardiograms were obtained at baseline, immediately after each bolus, and following 30 minutes of observation. No patient developed hypotension. There were no significant changes in systolic and diastolic blood pressure (BP) following the boluses. Compared with baseline, heart rate (HR) significantly decreased 5 minutes after the second bolus (73 +/- 12 vs 67 +/- 11 beats/min, p <0.05). Mean arterial BP increased (90 +/- 14 vs 100 +/- 16 mm Hg, p <0.05) and dp/dt decreased (1,599 +/- 645 vs 1,294 +/- 531 mm Hg/s p <0.05), whereas the PR, QT, and JT intervals increased (174 +/- 30 vs 182 +/- 33; 402 +/- 32 vs 424 +/- 35; 317 +/- 37 vs 336 +/- 32 ms, p <0.05, respectively) by the end of the 30-minute observation period. Amio-Aqueous possesses pharmacodynamic effects that have been attributed to amiodarone, whereas it lacks the hypotensive effect of the standard intravenous amiodarone formulation. Amio-Aqueous appears to be a safer alternative to Cordarone IV when rapid administration is indicated.