Atsushi Ikeda

Novel Contact Force Sensor Incorporated in Irrigated Radiofrequency Ablation Catheter Predicts Lesion Size and Incidence of Steam Pop and Thrombus

Background—An open-irrigated radiofrequency (RF) ablation catheter was developed to measure contact force (CF). Three optical fibers measure microdeformation of the catheter tip. The purpose of this study was to (1) validate the accuracy of CF sensor (CFS) (bench test); and (2) determine the relationship between CF and tissue temperatures, lesion size, steam pop, and thrombus during RF ablation using a canine thigh muscle preparation. Methods and Results—CFS measurements (total 1409) from 2 catheters in 3 angles (perpendicular, parallel, and 45°) were compared with a certified balance (range, 0 to 50 g). CFS measurements correlated highly (R2≥0.988; mean error, ≤1.0 g). In 10 anesthetized dogs, a skin cradle over the thigh muscle was superfused with heparinized blood at 37°C. A 7F catheter with 3.5-mm saline-irrigated electrode and CFS (Endosense) was held perpendicular to the muscle at CF of 2, 10, 20, 30, and 40 g. RF was delivered (n=100) for 60 seconds at 30 or 50 W (irrigation 17 or 30 mL/min). Tissue temperature (3 and 7 mm depths), lesion size, thrombus, and steam pop increased significantly with increasing CF at each RF power. Lesion size was greater with applications of lower power (30 W) and greater CF (30 to 40 g) than at high power (50 W) with lower CF (2 to 10 g). Conclusions—This novel ablation catheter, which accurately measures CF, confirmed CF is a major determinant of RF lesion size. Steam pop and thrombus incidence also increases with CF. CFS in an open-irrigated ablation catheter that may optimize the selection of RF power and application time to maximize lesion formation and reduce the risk of steam pop and thrombus.

Canine Model of Esophageal Injury and Atrial-Esophageal Fistula After Applications of Forward-Firing High-Intensity Focused Ultrasound and Side-Firing Unfocused Ultrasound in the Left Atrium and Inside the Pulmonary Vein

Background—Left atrial–esophageal fistula is a serious and poorly understood complication of catheter ablation of atrial fibrillation. The purpose of this study was to (1) develop a canine model of esophageal injury and left atrial-esophageal fistula after applications of forward-firing high-intensity focused ultrasound (HIFU) and side-firing unfocused ultrasound (SFU); (2) examine the relationship to esophageal temperature (Eso-temp); and (3) study the evolution of injury/healing. Methods and Results—Twenty dogs were studied. After transeptal puncture, HIFU catheter (ProRhythm Inc; 13 dogs) was positioned close to the esophagus, either outside (n=6) or inside (n=7) the inferior pulmonary vein (PV). In 7 other dogs, an SFU catheter was placed deep inside the PV, close to the esophagus. A balloon (20- to 25-mm diameter) with 7 thermocouples (2-mm separation) was positioned in the esophagus (Eso-balloon). Variable air filling of the Eso-balloon controlled the distance from the esophagus to the sonication source, pressing the esophagus against left atrium/PV. One to 9 (median, 5) HIFU (35 W) and 5 to 7 (median, 5) SFU (40 W) sonications were delivered for 40 seconds. Maximum luminal Eso-temp was closely related to HIFU Eso-balloon distance. For HIFU outside PV, Eso-temp ≥50°C occurred only for HIFU Eso-balloon distance ≤2 mm. For HIFU/SFU inside the PV, Eso-temp was ≥50°C, with HIFU Eso-balloon distance up to 6.8 mm. Endoscopy identified esophageal ulcer immediately after ablation in 11 of 13 HIFU dogs and 7 of 7 SFU dogs, all with Eso-temp ≥50°C. Endoscopy at 2 weeks showed ulcer healing in 5 of 11 chronic dogs and ulcer size progression with relaxation of the lower esophageal sphincter and esophagitis in 6 dogs. Two dogs developed left atrial-esophageal fistula and died at 2 weeks. Conclusions—This model produces esophageal ulcer when Eso-temp is ≥50°C. Eso-temp is higher with HIFU/SFU applications closer to the esophagus and with HIFU/SFU applications inside the PV. Ulcer progression and left atrial-esophageal fistula were associated with reflux esophagitis.

Mitral annular reduction with subablative therapeutic ultrasound: pre-clinical evaluation of the ReCor device.

AIMS To evaluate the potential for mitral annular (MA) size reduction using a novel device utilising therapeutic ultrasound (TU). METHODS AND RESULTS The ReCor device (ReCor Medical, Inc., Ronkonkoma, NY, USA, Investigational device, not for use in human application) was studied in a closed chest canine animal model (35 dogs). Under fluoroscopy, a 12 Fr TU balloon catheter was advanced into the left atrium (transseptal approach). The TU balloon was inflated with contrast-saline, positioned at the MA and energy delivered circumferentially, to heat the tissue locally. Five TU applications were delivered (at least 60W for at least 40 sec). Relative to baseline, mitral valve annular diameter reduction (measured by transthoracic echocardiography) was 8.4% immediately post procedure(p<0.001), 8.6% at one week (p<0.001), 8.8% at two weeks (p<0.001), 9.3% at three weeks (p<0.001), 10.8% at four weeks (p<0.001), 8.6% at three months (p<0.001) and 5.7% at six months (p<0.001). Histology showed an increase in elastin associated with tissue thickening at the annular level. Transmission electron microscopy demonstrated a decrease in diameter of individual collagen fibres in treated regions compared to controls. CONCLUSIONS Therapeutic ultrasound (TU) energy application to the mitral annulus is feasible percutaneously. A reduction in annular dimensions occurs immediately and appears to be durable without peri-annular damage.

Hyperuricemia as a risk factor for progressive renal insufficiency after coronary intervention in patients with chronic kidney disease

The development of renal insufficiency after percutaneous coronary intervention (PCI) is associated with increases in morbidity and mortality. Recent studies have reported that hyperuricemia (HU) results in hypertension, intrarenal vascular disease, and renal injury. We postulated that HU contributes to progressive renal disease after PCI. We studied 139 patients with chronic kidney disease (CKD) undergoing elective PCI including 59 HU patients. We assessed the relationship between HU and the development of renal insufficiency after PCI by estimating traditional contrast-induced nephropathy (CIN) and persistent postprocedural nephropathy (PPN) defined as an increase in creatinine ≥0.2xa0mg/dl of the baseline value 2xa0weeks after procedure. CIN and PPN were seen in 6.5 and 28.8% respectively. The incidence of PPN was higher in HU patients than in non-HU patients (pxa0<xa00.001) although the incidence of CIN was not significantly different between the two groups. PPN was more frequently observed in hyperuricemic patients irrespective of association with hypertension (with and without hypertension, pxa0<xa00.001 and pxa0=xa00.034, respectively). By univariate analysis, HU and hypertension are associated with PPN although there was no significant predictor of CIN in this study. Multivariate analysis showed HU and hypertension were independent predictors of PPN. HU is a predictor of slow and mild development of renal insufficiency after PCI in patients with CKD.

Rapid High Resolution Electroanatomical MappingClinical Perspective: Evaluation of a New System in a Canine Atrial Linear Lesion Model

Background— A canine right atrial (RA) linear lesion model was used to produce a complex pattern of RA activation to evaluate a novel mapping system for rapid, high resolution (HR) electroanatomical mapping. Methods and Results— The mapping system (Rhythmia Medical, Incorporated) uses an 8F deflectable catheter with a minibasket (1.8 cm diameter), containing 8 splines of 8 electrodes (total 64 electrodes, 2.5 mm spacing). The system automatically acquires electrograms and location information based on electrogram stability and respiration phase. In 10 anesthetized dogs, HR-RA map was obtained by maneuvering the minibasket catheter during sinus rhythm and coronary sinus pacing. A right thoracotomy was performed, and either 1 or 2 (to create a gap) epicardial linear lesions were created on the RA free wall (surgical incision or epicardial radiofrequency lesions). RA maps during RA pacing close to the linear lesions were obtained. A total of 73 maps were created, with 44 to 729 (median 237) beats and 833 to 12 412 (median 3589) electrograms (⩽2 to ⩽5 mm from surface geometry), resolution 1.8 to 5.3 (median 2.7) mm, and 2.6 to 26.3 (median 7.3) minutes mapping time. Without manual annotation, the system accurately created RA geometry and demonstrated RA activation, identifying the location of lines of block and presence or absence of a gap in all 10 dogs. Endocardial radiofrequency catheter ablation of a gap (guided by activation map) produced complete block across the gap in all 3 dogs tested. Conclusions— The new HR mapping system accurately and quickly identifies geometry and complex patterns of activation in the canine RA, with little or no manual annotation of activation time.Background— A canine right atrial (RA) linear lesion model was used to produce a complex pattern of RA activation to evaluate a novel mapping system for rapid, high resolution (HR) electroanatomical mapping.nnMethods and Results— The mapping system (Rhythmia Medical, Incorporated) uses an 8F deflectable catheter with a minibasket (1.8 cm diameter), containing 8 splines of 8 electrodes (total 64 electrodes, 2.5 mm spacing). The system automatically acquires electrograms and location information based on electrogram stability and respiration phase. In 10 anesthetized dogs, HR-RA map was obtained by maneuvering the minibasket catheter during sinus rhythm and coronary sinus pacing. A right thoracotomy was performed, and either 1 or 2 (to create a gap) epicardial linear lesions were created on the RA free wall (surgical incision or epicardial radiofrequency lesions). RA maps during RA pacing close to the linear lesions were obtained. A total of 73 maps were created, with 44 to 729 (median 237) beats and 833 to 12 412 (median 3589) electrograms (≤2 to ≤5 mm from surface geometry), resolution 1.8 to 5.3 (median 2.7) mm, and 2.6 to 26.3 (median 7.3) minutes mapping time. Without manual annotation, the system accurately created RA geometry and demonstrated RA activation, identifying the location of lines of block and presence or absence of a gap in all 10 dogs. Endocardial radiofrequency catheter ablation of a gap (guided by activation map) produced complete block across the gap in all 3 dogs tested.nnConclusions— The new HR mapping system accurately and quickly identifies geometry and complex patterns of activation in the canine RA, with little or no manual annotation of activation time.

Rapid High Resolution Electroanatomical MappingClinical Perspective

Background— A canine right atrial (RA) linear lesion model was used to produce a complex pattern of RA activation to evaluate a novel mapping system for rapid, high resolution (HR) electroanatomical mapping. Methods and Results— The mapping system (Rhythmia Medical, Incorporated) uses an 8F deflectable catheter with a minibasket (1.8 cm diameter), containing 8 splines of 8 electrodes (total 64 electrodes, 2.5 mm spacing). The system automatically acquires electrograms and location information based on electrogram stability and respiration phase. In 10 anesthetized dogs, HR-RA map was obtained by maneuvering the minibasket catheter during sinus rhythm and coronary sinus pacing. A right thoracotomy was performed, and either 1 or 2 (to create a gap) epicardial linear lesions were created on the RA free wall (surgical incision or epicardial radiofrequency lesions). RA maps during RA pacing close to the linear lesions were obtained. A total of 73 maps were created, with 44 to 729 (median 237) beats and 833 to 12 412 (median 3589) electrograms (⩽2 to ⩽5 mm from surface geometry), resolution 1.8 to 5.3 (median 2.7) mm, and 2.6 to 26.3 (median 7.3) minutes mapping time. Without manual annotation, the system accurately created RA geometry and demonstrated RA activation, identifying the location of lines of block and presence or absence of a gap in all 10 dogs. Endocardial radiofrequency catheter ablation of a gap (guided by activation map) produced complete block across the gap in all 3 dogs tested. Conclusions— The new HR mapping system accurately and quickly identifies geometry and complex patterns of activation in the canine RA, with little or no manual annotation of activation time.Background— A canine right atrial (RA) linear lesion model was used to produce a complex pattern of RA activation to evaluate a novel mapping system for rapid, high resolution (HR) electroanatomical mapping.nnMethods and Results— The mapping system (Rhythmia Medical, Incorporated) uses an 8F deflectable catheter with a minibasket (1.8 cm diameter), containing 8 splines of 8 electrodes (total 64 electrodes, 2.5 mm spacing). The system automatically acquires electrograms and location information based on electrogram stability and respiration phase. In 10 anesthetized dogs, HR-RA map was obtained by maneuvering the minibasket catheter during sinus rhythm and coronary sinus pacing. A right thoracotomy was performed, and either 1 or 2 (to create a gap) epicardial linear lesions were created on the RA free wall (surgical incision or epicardial radiofrequency lesions). RA maps during RA pacing close to the linear lesions were obtained. A total of 73 maps were created, with 44 to 729 (median 237) beats and 833 to 12 412 (median 3589) electrograms (≤2 to ≤5 mm from surface geometry), resolution 1.8 to 5.3 (median 2.7) mm, and 2.6 to 26.3 (median 7.3) minutes mapping time. Without manual annotation, the system accurately created RA geometry and demonstrated RA activation, identifying the location of lines of block and presence or absence of a gap in all 10 dogs. Endocardial radiofrequency catheter ablation of a gap (guided by activation map) produced complete block across the gap in all 3 dogs tested.nnConclusions— The new HR mapping system accurately and quickly identifies geometry and complex patterns of activation in the canine RA, with little or no manual annotation of activation time.

Contrast media injection into right coronary artery caused thrombus extraction to aorta that may have resulted in left main trunk thrombosis

A 59-year-old man with inferior acute myocardial infarction underwent an urgent coronary angiography and as a result a total occlusion of the ostial right coronary artery (RCA) was observed. Interestingly, the thrombus in the RCA clearly shortened within 2.3xa0s during the contrast media injection. While we prepared for percutaneous coronary intervention (PCI) of the RCA, ventricular fibrillation occurred and pulseless electrical activity continued in spite of repeated cardioversion. Despite no stenosis in the left main trunk (LMT) in the initial coronary angiography, the LMT was totally occluded. Following aspiration therapy on the LMT with percutaneous cardiopulmonary support, PCI of the RCA was performed. A coronary angiography should be carefully performed if a lot of thrombi exist in the coronary ostium because LMT embolism may have been caused by thrombus extraction from the RCA by contrast media injection.