Cooled tip RF current delivery at high power is associated with increased myocardial lesion size which may facilitate successful ablation of ventricular tachycardia associated with acquired structural heart disease. Catheter-tip temperature should be maintained below 45 degrees C to prevent popping and abrupt impedance rise during RF energy delivery.

Sufentanil, a lipophilic opioid, is the most frequently used clinical drug for ischemic heart disease. The effects of sufentanil on MAPK signaling in ischemic heart disease were explored. The effects of sufentanil on ischemia-reperfusion (IR)-induced myocardial injury in a rat model were examined. The serum levels of CK, LDH, MDA and SOD, and the activities of Na-K-ATPase and Ca-Mg-ATPase were measured. The levels of total and phosphorylated ERK1/2, JNK, and p38 were measured by western blotting in the heart, and the myocardial H9C2 cell line was studied. Using the Cell Counting Kit-8, the growth rate of H9C2 cells affected by sufentanil was studied. The serum levels of CK, LDH and MDA were higher in the IR group than in the SO and SUF groups. The SOD level, as well as the activities of Na-K-ATPase and Ca-Mg-ATPase, were lower in the SO and SUF groups than in the IR group. The phosphorylated ERK1/2 level was lower in the IR group than in the SO and SUF groups. The growth rate of H9C2 cells increased with the concentration of sufentanil and the exposure time. The phosphorylated ERK level was upregulated by 4-12 h of sufentanil exposure, indicating that the effects were time-dependent. Furthermore, an inhibition of ERK signaling by chemical inhibition suppressed the sufentanil-mediated increase in the growth rate of H9C2 cells. Sufentanil appears to be beneficial for cases of worsening ischemic heart disease. Further studies are necessary before a clinical application is considered.

SummarySteam pop and intramural charring have been reported during cooled-tip radiofrequency catheter ablation (RFCA). We studied the feasibility of temperature-controlled cooled-tip RFCA in the canine heart.An internally cooled ablation catheter was inserted into the left ventricle. A custom-made radiofrequency (RF) generator capable of controlling the tip-temperature at the preset level by slow increases in the power was used. Temperature-controlled cooled-tip RF applications were performed at a target temperature of 40°C for 90 seconds. Acute study: Intramyocardial temperature was measured at the ablation site in 10 dogs by inserting a fluoroptic probe. Chronic study: Lesion depth and volume were measured in 5 dogs after 3 weeks of survival. In the acute study, no pop or abrupt impedance rise was observed. Maximum intramyocardial temperature was 72.4 ± 14.4°C at 2-4 mm above the endocardium. No coagulum formation, craters, or intramural charring were observed. Maximum lesion depth was 6.7 ± 1.5 mm, and lesion volume was 404 ± 219 mm 3 . In the chronic study, maximum lesion depth was 5.9 ± 1.1 mm, and lesion volume was 281 ± 210 mm 3 . Temperature controlled RFCA is feasible with a cooled-tip catheter and an RF generator that slowly increases the RF power until the preset catheter-tip temperature is reached. (Int Heart J 2010; 51: 193-198)

SummaryDue to the difficulty in producing a transmural linear lesion and the possibility of complications such as thrombus formation leading to thromboembolism, the catheter-based maze procedure remains problematic.We tested, in pigs, the possibility of using a temperature-controlled cooled-tip radiofrequency (RF) ablation system together with a realtime position management (RPM) system to create a transmural linear lesion uncomplicated by thrombus formation.Nine pigs underwent insertion of two electrode catheters (each with two ultrasound electrodes), one into the coronary sinus (CS) and one into the right ventricular apex (references for ultrasound-based non-fluoroscopic three-dimensional mapping). A cooled-tip catheter (with two ultrasound electrodes) was introduced into the right atrium. Linear right atrial ablation was performed with a custom radiofrequency (RF) generator. The catheter was perfused with 0.66 mL/ second of saline. RF was delivered for 60 seconds at a target temperature of 40°C. A linear ablation line was created between the superior vena cava and inferior vena cava. Three-dimensional isochronal maps were created during CS pacing before and after ablation.In 4 of the 9 pigs, a transmural linear ablation line was confirmed by three-dimensional mapping and postmortem macroscopic examination. No endocardial thrombus formation was noted.Temperature-controlled cooled-tip RF linear ablation guided by an RPM system appears to have potential for creating linear lesions in the atria. Further studies are needed to determine whether such an ablation technique and the parameters used will facilitate successful completion of the catheter-based maze procedure. (Int Heart J 2011; 52: 50-55) Key words: Cooled-tip ablation, Atrium, Three-dimensional mapping, Linear ablation P ulmonary vein (PV) isolation is an established treatment for paroxysmal atrial fibrillation (AF), and the success rate is relatively high.1,2) However, persistent AF often requires atrial linear ablation.3,4) Irrigated-tip catheter ablation has been shown to facilitate bidirectional conduction block in the atria.5,6) However, there is greater discrepancy between measured electrode tip temperature and actual tissue temperature than with a standard ablation catheter; thus, there is greater potential for excessive but unrecognized heating within the myocardium. 7,8) This overheating results in the boiling of any water in the tissues and the creation of steam, which erupts through the tissue surface and is heard as a pop. We have shown the feasibility of temperature-controlled cooled-tip radiofrequency (RF) ablation in in vivo experiments. 9) However, precise positioning of the ablation catheter by fluoroscopy only is difficult and time consuming, resulting in long fluoroscopy times. RF catheter ablation procedures may be facilitated using additional endocardial mapping techniques; however, current available techniques are limited. Single electrode mapping or the use of multiple catheters is time consuming, and geometric reconstruction is di...

Right atrial monophasic action potentials were recorded before and after 60 minutes of rapid atrial pacing (pacing cycle length (CL); 127 +/- 10 ms) in 12 closed-chest dogs. The right atrial (RA) monophasic action potential (MAP) duration at 90% repolarization (RAMAPD) was measured at CLs of 400 ms and 250 ms. CL-dependent changes in RAMAPD (CL 400 ms - 250 ms) before and after rapid atrial pacing were 24 +/- 1 ms and 16 +/- 5 ms, respectively (p < 0.02). RAMAP was recorded at each atrial pacing CL starting at 240 ms decreasing by 10-ms increments. RAMAPD alternans was observed in 10 of 12 dogs at a CL of 163 +/- 17 ms before and in 10 of 12 dogs at s CL of 198 +/- 29 ms (p < 0.01) after rapid atrial pacing. Sustained atrial fibrillation (AF) (>5 minutes) was induced in 1 of 12 dogs at a pacing CL of 130 ms before rapid atrial pacing and in 4 of 12 dogs at a pacing CL of 135 +/- 17 ms after rapid atrial pacing. Onset of AF was always preceded by the RAMAPD alternans. Sixty minutes of rapid atrial pacing leads to diminution of rate adaptation of atrial action potential duration (APD) and appearance of APD alternans of greater magnitude at longer CL, both of which may contribute to the initiation and perpetuation of AF during its early phase.