This study included a total of 110 patients with drug-refractory AF (82 paroxysmal and 28 persistent) who underwent first PVI by CA in our laboratory between March 2010 and February 2011. Patient characteristics are shown in Table 1. All patients gave their written informed consent and antiarrhythmic drugs (AADs) were discontinued 7 d before the ablation session. All patients were effectively anticoagulated for > 4 wk, and a 64-slice multidetector computed tomography (MDCT) scan of the left atrium (LA) and/or transesophageal echocardiography was performed before the CA to exclude any atrial thrombi.

Transthoracic echocardiography was performed on all patients to measure LA diameter. MDCT was performed for electroanatomical mapping integration, pulmonary vein anatomy delineation, LA thrombi exclusion, measuring the PV ostium diameter, and LA volume estimation.

The procedures were performed during deep sedation/analgesia with the administration of propofol and dexmedetomidine with preservation of spontaneous breathing and continuous monitoring of the systemic arterial pressure and oxygen saturation.

A 6 Fr duo-decapolar three-site mapping catheter (EPstar SAC, Japan Lifeline Inc., Tokyo, Japan) was positioned in the coronary sinus for pacing, recording and internal cardioversion. Four venous sheaths (5, 8, 8 and 8.5 Fr) and one arterial sheath (4 Fr) were placed in the femoral veins/arteries. A 5 Fr catheter was introduced into the right ventricle. A single trans-septal puncture was performed. After the trans-septal puncture, two non-steerable long sheaths (LAMP 45; St Jude Medical, St Paul, MN, United States; Preface; Biosense-Webster, Diamond Bar, CA, United States) and a steerable introducer (Agilis NxT Steerable Introducer Small Curl; St Jude Medical) were introduced into the left superior pulmonary vein, left inferior pulmonary vein (LIPV) and right superior pulmonary vein, respectively. Left arteriography by injection of contrast medium via the three long sheaths was simultaneously performed to obtain the anatomical relationship between the area around the PV ostium and the esophagus (Figure 1).

Open in New Tab   Full Size Figure   Download Figure

Figure 1 Left arteriography. Fluoroscopy of left arteriography using the trans-septal sheath after short iatrogenic complete AV-block using high-frequency right ventricular stimulation. The relationship is shown of the eso-temperature probe (Eso) with three thermistor electrodes (T1-T3) to the ostium of the pulmonary veins. Upper: Right anterior oblique; Lower: Left anterior oblique. LSPV: Left superior pulmonary vein; LIPV: Left inferior pulmonary vein; RSPV: Right superior pulmonary vein; RIPV: Right inferior pulmonary vein.

A 5000-U intravenous bolus of heparin was administered after the successful trans-septal puncture. The activated clotting time (ACT) was measured every 30 min, and the heparin dose was adjusted to maintain a target ACT of 300 s.

Two circular mapping catheters (EPstar Libero; Japan Lifeline Inc.) were placed in the superior and inferior pulmonary veins, respectively, and the left- and right-sided ipsilateral PVs were circumferentially and extensively ablated, respectively, with use of an electromagnetic mapping system (CARTO, Biosense Webster, United States) and electrophysiologic guidance. The LA posterior wall, at a distance of 1 to 3 cm from the left- or right-sided ostia of the PVs, was anatomically ablated. The distal edges of the anterior aspect of the PVs with early PV potentials or continuous PV and LA potentials were targeted for ablation. Isolation of the left sided PVs was performed during distal coronary sinus pacing and isolation of the right-sided PVs during sinus rhythm.

Ablation was performed with an open irrigated tip catheter (ThermoCool; Biosense Webster). A generator was used to deliver 25 W of RF energy to the catheter tip and finished delivery in 20-25 s at all sites. The irrigation flow rate was set to 17 mL/min. For safety, the generator was set to reduce the power if the temperature of the catheter exceeded 43 °C. The ablation catheter was irrigated for 2 s just before and just after delivering the energy. A cut-off LET of 42 °C was defined for the termination of the energy delivery. Even if an ablation catheter was near to the temperature probe in fluoroscopy, we delivered energy if the LET did not rise. After the LET normalized, the ablation was continued with less power and/or an alternative ablation course was chosen to prevent further temperature rises. The endpoint of the ablation was the elimination of all PV potentials and pacing maneuvers performed inside the PVs to test for any remaining PV conduction or complete PVI with bidirectional block[14].

After completing the PVI, the cavotricuspid isthmus was also ablated to create bidirectional conduction block[15]. Following the PVI and cavotricuspid isthmus ablation, decremental pacing was performed from the coronary sinus or LA appendage starting at a cycle length of 300 ms and ending with loss of 1:1 atrial capture, which was repeated two times. If burst pacing from the coronary sinus or LA appendage was able to induce sustained AF lasting > 5 min, the LA roof line and the mitral isthmus between the LIPV and mitral annulus were also ablated to achieve bidirectional conduction block. Finally, in the presence of sustained AF induced by burst pacing, ablation-targeting complex fractionated atrial electrography (CFAE) was performed within the LA including the coronary sinus.

In all patients, an LET monitoring probe (Esotherm; FIAB SpA, Florence, Italy) with three olive-shaped metal thermocouple electrodes (distance 10 mm) was placed within the esophagus under fluoroscopic guidance directly posterior to the LA. The temperature probe was adjusted to equal heights of the PV ostium after left arteriography and selective cannulation of the PVs with the ablation catheter. The temperature probe was connected to three precision thermometers allowing continuous measurement, recording and display of the LET.

We measured the number of times the LET reached the cut-off temperature, the time when the LET reached the cut-off temperature, the maximum temperature (T max) of the LET, the time to reach T max after the LET reached the cut-off temperature, and the time for the temperature to decrease to the following values after stopping delivery of energy: 42, 41, 40, 39, 38 and 37 °C and the temperature before the delivery of energy. We also measured the temperature before the delivery of energy at the site where the LET reached the cut-off temperature (Figure 2).

Open in New Tab   Full Size Figure   Download Figure

Figure 2 Position of ablation catheter (A) (left: right anterior oblique, right: left anterior oblique) and luminal esophageal temperature monitoring graph (B). We measured the time when luminal esophageal temperature (LET) reached the cut-off temperature (a), the maximum temperature (T max) of LET, the time to reach T max after the LET reached 42 °C (b) and the time to come back from the delivery of energy end to 42 °C (c), 41 °C (d), 40 °C (e), 39 °C (f), 38 °C (g) and 37 °C (h), and the temperature before the delivery of energy (i). LSPV: Left superior pulmonary vein; LIPV: Left inferior pulmonary vein; RSPV: Right superior pulmonary vein; RIPV: Right inferior pulmonary vein.

After 3-6 mo, in the absence of any AF recurrence, anticoagulant treatment was discontinued unless other major risk factors were present. AADs were not prescribed for patients with paroxysmal AF, but were prescribed for 3 mo following the ablation in patients with persistent AF. All patients were scheduled to visit our clinic at 1, 3 and 6 mo after discharge. In the case of nonappearance at the follow-up dates, patients were contacted by telephone. A recurrence of AF was defined according to the patient’s symptoms and electrocardiogram. All patients took proton pump inhibitors (PPIs) after ablation for at least 2 wk.

Continuous variables are expressed as the mean ± SD except for the count and time variables. Statistical significance was assessed using the unpaired Student’s t test or Mann-Whitney test if necessary. Categorical variables, expressed as numbers or percentages, were analyzed with the χ² test or Fisher’s exact test. All tests were two-tailed and a P value < 0.05 was considered statistically significant.

The study was approved by the Institutional Review Board of Takeda Hospital (Kyoto, Japan).

Twenty-nine patients underwent a second ablation procedure and eight underwent a third involving treatment for reconduction of the PVs, the LA roof line, the mitral isthmus line, ablation of new atrial premature contraction foci, or additional CFAE ablation. The final success rate, evaluated at 6 mo after the first session, was 89% (73 of 82, including eight patients with AADs) for the paroxysmal AF patients and 79% (22 of 28, including 10 with AADs) for the persistent AF patients.

A left atrial esophageal fistula due to thermal injury to the esophagus is a devastating complication after pulmonary vein isolation (PVI). A report exists that illustrates the potential for esophageal damage during the application of radiofrequency (RF) energy, and the ability to monitor luminal esophageal temperature (LET) by inserting a temperature probe in the esophagus. However, there have been no reports on the detailed examination of the progress of the LET in PVI for atrial fibrillation (AF).

This study reports on the detailed examination of the progress of the LET in PVI for AF. Specifically, this is the first study to report on transient drop in the LET (TDLET) just before the delivery of energy.

A report exists that illustrates the potential for esophageal damage during the application of RF energy, and the ability to monitor LET by inserting a temperature probe in the esophagus. However, nobody was able to anticipate whether LET increased before delivering energy. The TDLET before energy delivery may be useful to distinguish a high risk of esophageal injury before delivery of energy.

Detecting TDLET before energy delivery is useful for identifying a higher risk of esophageal injury. Therefore, the lower limit of LET in PVI is important to prevent esophageal injury by discovering TDLET.

The study shows a new aspect of the LET monitoring during AF ablation. It shows, that the esophageal sites with the highest increase of temperature during ablation can be predicted by measuring the degree of lowering the intraluminal temperature shortly prior starting ablation. The decrease of LET is caused by proximity of the irrigated catheter tip in the posterior left atrium. It seems to be evident, that the cooling effect of the catheter is more pronounced on sites that are anatomically closer, than on sites that are more distant. This finding has not been described yet in a peer reviewed journal. This is an interesting manuscript with considerable merit.