Safe procedures despite ultra low radiation doses during catheter ablations of atrial and ventricular arrhythmias-A multicenter experience.

INTRODUCTION: Despite the development of non-fluoroscopic catheter visualization options, fluoroscopy is still used in most ablation procedures. The aim of this multicenter study was to evaluate the safety and efficacy of a new ultra-low dose radiation protocol for EP procedures in a large number of patients. METHODS AND RESULTS: A total of 3462 consecutive patients (male 1926 (55.6%), age 64.4 ± 14.0 years, BMI 26.65 ± 4.70) undergoing radiofrequency ablation (left atrial (n = 2316 [66.9%], right atrial (n = 675 [19.5%], or ventricular (n = 471 [13.6%]) in three German centers were included in the analysis. Procedures were performed using a new ultra-low dose protocol operating at 8nGy for fluoroscopy and 36nGy for cine-loops. Additionally a very low framerate (2-3FPS) was used. Using the new protocol very low Air kerma-area product (KAP) values were achieved for left atrial ablations (104.25 ± 84.22 µGym2 ), right atrial ablations (70.98 ± 94.79 µGym2 ) and ablations for ventricular tachycardias or PVCs (78.62 ± 66.59 µGym2 ). Acute procedural success was achieved in 3289/3388 (97.1%) while the rate of major complications was very low compared to previously published studies not using low dose settings (n = 20, 0.6%). CONCLUSION: The ultra-low dose, low framerate protocol leads to very low radiation doses for all EP procedures while neither procedural time, fluoroscopy time nor success or complication rates were compromised. When compared to current real-world Air KAP data the new ultra-low dose fluoroscopy protocol reduces radiation exposure by more than 90%.

Limiting esophageal temperature in radiofrequency ablation of left atrial tachyarrhythmias results in low incidence of thermal esophageal lesions.

BACKGROUND: Atrio-esophageal fistula formation following radiofrequency ablation of left atrial tachyarrhythmias is a rare but devastating complication. Esophageal injuries are believed to be precursors of fistula formation and reported to occur in up to 47% of patients. This study investigates the incidence of esophageal lesions when real time esophageal temperature monitoring and temperature limitation is used. METHODS: 184 consecutive patients underwent open irrigated radiofrequency ablation of left atrial tachyarrhythmias. An esophageal temperature probe consisting of three independent thermocouples was used for temperature monitoring. A temperature limit of 40°C was defined to interrupt energy delivery. All patients underwent esophageal endoscopy the next day. RESULTS: Endoscopy revealed ulcer formation in 3/184 patients (1.6%). No patient developed atrio-esophageal fistula. Patient and disease characteristics had no influence on ulcer formation. The temperature threshold of 40°C was reached in 157/184 patients. A temperature overshoot after cessation of energy delivery was observed frequently. The mean maximal temperature was 40.8°C. Using a multiple regression analysis creating a box lesion that implies superior- and inferior lines at the posterior wall connecting the right and left encircling was an independent predictor of temperature. Six month follow-up showed an overall success rate of 78% documented as sinus rhythm in seven-day holter ECG. CONCLUSION: Limitation of esophageal temperature to 40°C is associated with the lowest incidence of esophageal lesion formation published so far. This approach may contribute to increase the safety profile of radiofrequency ablation in the left atrium.

Brief antecedent anoxia preserves mitochondrial function after sustained undersupply: a subcellular correlate to ischemic preconditioning?

BACKGROUND: There is increasing evidence that mitochondria - owning a high degree of autonomy within the cell - might represent the target organelles of the myocardial protection afforded by ischemic preconditioning. It was the aim of the study to investigate a possible subcellular correlate to ischemic preconditioning at the mitochondrial level. In addition, we tested whether this protection depends on mitochondrial ATP-dependent potassium channels (K (ATP)) and an might involve an attenuation of mitochondrial ATP hydrolysis during sustained anoxia. METHODS AND RESULTS: Sustained anoxia (A, 14 min) and reoxygenation (R) completely inhibited state 3 and state 4 respiration of isolated ventricular mitochondria from Wistar rats. An antecedent brief anoxic incubation (4 min) followed by reoxygenation (2 min) prevented this loss of mitochondrial function. The protection afforded by anoxic preconditioning could be mimicked by the K (ATP) opener diazoxide (30 micromol/l) and was completely inhibited by the K (ATP) blocker 5-hydroxydecanoic acid (300 micromol/l). Structural mitochondrial integrity, as estimated from externalization of the mitochondrial enzymes creatine kinase and glutamateoxalacetate transaminase, remained unchanged between the groups, as did mitochondrial ATP loss during anoxia. CONCLUSION: For the first time, we provide direct evidence for a subcellular preconditioning-like functional mitochondrial adaptation to sustained anoxia. This effect apparently depends on opening of K(ATP) but is independent of ATP preservation.