Evaluating temperature gradients across the posterior left atrium with radiofrequency ablation.

INTRODUCTION: Esophageal injury is a well-known complication associated with catheter ablation. Though novel methods to mitigate esophageal injury have been developed, few studies have evaluated temperature gradients with catheter ablation across the posterior wall of the left atrium, interstitium, and esophagus. METHODS: To investigate temperature gradients across the tissue, we developed a porcine heart-esophageal model to perform ex vivo catheter ablation on the posterior wall of the left atrium (LA), with juxtaposed interstitial tissue and esophagus. Circulating saline (5 L/min) was used to mimic blood flow along the LA and alteration of ionic content to modulate impedance. Thermistors along the region of interest were used to analyze temperature gradients. Varying time and power, radiofrequency (RF) ablation lesions were applied with an externally irrigated ablation catheter. Ablation strategies were divided into standard approaches (SAs, 10-15 g, 25-35 W, 30 s) or high-power short duration (HPSD, 10-15 g, 40-50 W, 10 s). Temperature gradients, time to the maximum measured temperature, and the relationship between measured temperature as a function of distance from the site of ablation was analyzed. RESULTS: In total, five experiments were conducted each utilizing new porcine posterior LA wall-esophageal specimens for RF ablation (n = 60 lesions each for SA and HPSD). For both SA and HPSD, maximum temperature rise from baseline was markedly higher at the anterior wall (AW) of the esophagus compared to the esophageal lumen (SA: 4.29°C vs. 0.41°C, p < .0001 and HPSD: 3.13°C vs. 0.28°C, p < .0001). Across ablation strategies, the average temperature rise at the AW of the esophagus was significantly higher with SA relative to HPSD ablation (4.29°C vs. 3.13°C, p = .01). From the start of ablation, the average time to reach a maximum temperature as measured at the AW of the esophagus with SA was 36.49 ± 12.12 s, compared to 16.57 ± 4.54 s with HPSD ablation, p < .0001. Fit to a linear scale, a 0.37°C drop in temperature was seen for every 1 cm increase in distance from the site of ablation and thermistor location at the AW of the esophagus. CONCLUSION: Both SA and HPSD ablation strategies resulted in markedly higher temperatures measured at the AW of the esophagus compared to the esophageal lumen, raising concern about the value of clinical intraluminal temperature monitoring. The temperature rise at the AW was lower with HPSD. A significant time delay was seen to reach the maximum measured temperature and a modest increase in distance between the site of ablation and thermistor location impacted the accuracy of monitored temperatures.

Development of a novel score to predict the risk of acute kidney injury in patient with acute myocardial infarction.

BACKGROUND: Acute kidney injury (AKI) is common in patients with acute myocardial infarction. AKI in this setting is associated with short- and long-term adverse events. The aim of this study was to develop a simple score to predict AKI in patients presenting with acute myocardial infarction based on data available at time of admission. METHODS: This was a retrospective analysis of data collected as part of the Acute Coronary Treatment and Intervention Outcomes Network (ACTION) registry at a tertiary care center between 1/1/2011 and 12/31/2013. Data were collected prospectively for all patients who presented within 24 h of the onset of myocardial infarction. AKI was defined as an increase in creatinine from admission level to peak level of ≥0.3 mg/dl or by ≥50 %. Patients with history of end-stage renal disease requiring renal replacement therapy were excluded. RESULTS: Of 1107 patients included in the study, 147 (13.3 %) developed AKI. The following factors were independently associated with increased risk for AKI: cardiac arrest, decompensated heart failure on presentation, diabetes mellitus, hypertension, anemia, impaired renal function on presentation, and tachycardia on presentation. These factors were combined to form a new predictive tool. The new score showed excellent discrimination for AKI: the area under the receiver operating characteristic curve (AUROC) was 0.76 (95 % confidence interval 0.72-0.80). CONCLUSION: A simple score using clinical and laboratory data available on admission can predict the risk of AKI in patients presenting with acute myocardial infarction.