First in Human Validation of Impedance‐Based Catheter Tip‐to‐Tissue Contact Assessment in the Left Atrium

Background: In this study, a new method of contact assessment based on the measurement of the local electrical properties at the catheter tip‐to‐tissue interface was validated in a blinded fashion in vivo in the human left atrium. Methods: Using a 3‐terminal circuit model, local resistance and reactance between catheter tip and tissue surface were measured and combined in an electrical coupling index (ECI). Twelve patients undergoing atrial fibrillation (AF) catheter ablation were included in this study. The catheter was placed in the left atrium at various levels of contact. Blinded to the physician, measurements of electrogram amplitudes, pacing thresholds, and impedances at the catheter tip‐to‐tissue interface were performed. Results: As the catheter went from noncontact to contact, ECI increased from 118 ± 15 to 145 ± 24 (P < 0.0001), electrogram amplitudes increased from 0.14 ± 0.16 to 2.0 ± 1.9 mV (P < 0.0001), and pacing thresholds decreased from 13.9 ± 3.1 to 3.1 ± 2.0 mA (P < 0.0001). ECI was significantly higher in vascular tissue as compared with trabeculated and smooth myocardium. Patch orientation, operator, body mass index, or clinical type of AF had no influence on ECI values. On a patient‐by‐patient analysis, true contact/noncontact locations showed a mean ECI difference of 32.7 ± 11.6 units (95% CI 25.8–39.6). A cut‐off value of 5 ECI units was able to separate contact from noncontact with 97% sensitivity and 95% specificity. Conclusion: Measurement of local impedances between catheter tip and tissue is feasible to reproducibly describe electrical catheter contact within the left atrium in a clinical setting of AF catheter ablation.     

Superiority of gold versus platinum irrigated tip catheter ablation of the pulmonary veins and the cavotricuspid isthmus: a randomized study comparing tip temperatures and cooling flow requirements

Gold versus Platinum Irrigated Tip Ablation Catheters. Introduction: In order to optimize power delivery into the myocardium during radiofrequency ablation (RFA) without overheating the electrode tip, active cooling of the tip electrode as well as electrode tips made of gold have evolved. Recently, an externally irrigated gold tip electrode ablation catheter has been developed to combine the advantages of these 2 technologies. We sought to investigate the procedural parameters tip temperature, delivered power and cooling flow requirements of the irrigated gold tip catheter in comparison to the conventional irrigated platinum iridium (Pt) tip catheter in pulmonary vein isolation (PVI) and cavotricuspid isthmus (CTI) ablation. Methods and Results: Sixty patients referred for first PVI were randomized into ablation with irrigated gold tip catheter versus irrigated Pt tip catheter. Forty‐nine patients received ablation of CTI following PVI. Mean and standard deviation from all measurements were calculated for each patient. During RFA of pulmonary veins, mean catheter tip temperature was significantly lower in the gold group (35.4 ± 0.9 °C vs 38.2 ± 0.8 °C, P < 0.001), and total amount of delivered energy was higher (1303.1 ± 81.1 W vs 1223.7 ± 115.6 W, P = 0.004). During CTI ablation, necessary saline flow was almost 2.5‐fold lower in the gold group (22.5 ± 5.9 mL/min vs 52.5 ± 9.7 mL/min, P < 0.001), accompanied by significantly lower tip temperature (39.1 ± 0.6 °C vs 40.5 ± 1.4 °C, P < 0.001). Conclusion: The irrigated gold tip electrode allows to deliver significantly more energy at a lower electrode tip temperature in RFA of PV and CTI in comparison to the irrigated Pt tip electrode. The required saline flow during CTI ablation is much lower than in Pt. (J Cardiovasc Electrophysiol, Vol. 23, pp. 717‐721, July 2012)     

Novel Collagen Vascular Plug for Femoral Arteriotomy Sealing: Acute and Chronic In Vivo Studies

Background: The current use of collagen vascular hemostasis devices to percutaneously seal femoral arteriotomy sites is limited by a significant incidence of vascular complications. The purpose of the present study was to assess the efficacy of new collagen plug specifically designed to avoid these complications by accurately gauging the depth of the femoral artery and by minimizing the risk of intra-arterial collagen deployment. Methods: The hemostasis device used in this study consists of a multicomponent collagen plug with an external rigid collagen tube lined by an inner layer of absorptive sponge collagen. Placement of this plug is facilitated with a specialized two-lumen dilator, which localizes the arterial surface using a “bleedback” mechanism from one of the lumens, and prevents the placement of collagen through the arteriotomy site. The acute efficacy of this device was assessed in 26 adult dogs in which 36 collagen plugs were used to seal 8Fr femoral arteriotomies. An additional 16 arteriotomies treated with standard manual compression served as study controls. Following plug placement or manual compression, all puncture sites were observed for bleeding and hematoma formation over a 45-minute period. Patency of each instrumented artery was assessed with serial femoral angiography and localization of each plug was confirmed with surgical cutdown at the puncture site. The chronic efficacy of this device was assessed in three pigs in which three collagen plugs were used to seal 8Fr femoral arteriotomies. The three animals were subsequently sacrificed at 7,14, and 30 days, respectively, for histologic analysis. Results: In acute animals, all 36 plugs were successfully placed without evidence of vascular compromise or intra-arterial collagen deployment. In nonanticoagulated animals, hemostasis was achieved within 5 minutes in 10 of 10 plugs placed with a skin-to-arlery distance > 1.8 cm, in 4 of 7 plugs with a skin-to-artery distance of 1.2–1.7 cm, and in 0 of 9 plugs with a skin-to-artery distance < 1.2 cm. In anticoagulated animals, hemostasis within 5 minutes was demonstrated with 8 of 10 plugs with a skin-to-artery distance > 1.8 cm; small hematomas occurred in the remaining two animals in the setting of a PTT > 100 seconds. Time to hemostasis was significantly less for collagen plugs than manual compression in both nonanticoagulated animals (plug 17 ± 16 minutes; manual compression 28 ± 5 minutes; P < 0.03) and anticoagulated animals (plug 6 ± 2 minutes; manual compression 42 ± 4 minutes; P < 0.01). Chronic studies demonstrated femoral artery patency in all three pigs. Histologic analysis demonstrated progressive collagen resorption with no difference between collagen plug placement or manual compression at 30 days. Conclusions: The local hemostasis device utilized in this study resulted in accurate placement of a collagen plug immediately adjacent to the arteriotomy site with no evidence of acute or chronic vascular compromise or intra-arterial collagen deposition. Hemostasis with shorter compression times than with standard manual techniques was achieved at puncture sites in which the skin-to-artery distance was > 1.8 cm and the anticoagulation profile was not excessive. At 1 month postplacement, there is no histologic difference between plug use and standard manual compression. (J Interven Cardiol 1996;9:25–33)     

Robotically Assisted Ablation Produces More Rapid and Greater Signal Attenuation Than Manual Ablation

Introduction: Robotic remote catheter ablation potentially provides improved catheter‐tip stability, which should improve the efficiency of radiofrequency energy delivery. Percentage reduction in electrogram peak‐to‐peak voltage has been used as a measure of effectiveness of ablation. We tested the hypothesis that improved catheter‐tip stability of robotic ablation can diminish signals to a greater degree than manual ablation. Methods: In vivo NavX? maps of 7 pig atria were constructed. Separate lines of ablation were performed robotically and manually, recording pre‐ and postablation peak‐to‐peak voltages at 10, 20, 30, and 60 seconds and calculating signal amplitude reduction. Catheter ablation settings were constant (25W, 50°, 17 mL/min, 20–30 g catheter tip pressure). The pigs were sacrificed and ablation lesions correlated with NavX maps. Results: Robotic ablation reduced signal amplitude to a greater degree than manual ablation (49 ± 2.6% vs 29 ± 4.5% signal reduction after 1 minute [P = 0.0002]). The mean energy delivered (223 ± 184 J vs 231 ± 190 J, P = 0.42), power (19 ± 3.5 W vs 19 ± 4 W, P = 0.84), and duration of ablation (15 ± 9 seconds vs 15 ± 9 seconds, P = 0.89) was the same for manual and robotic. The mean peak catheter‐tip temperature was higher for robotic (45 ± 5°C vs 42 ± 3°C [P < 0.0001]). The incidence of >50% signal reduction was greater for robotic (37%) than manual (21%) ablation (P = 0.0001). Conclusion: Robotically assisted ablation appears to be more effective than manual ablation at signal amplitude reduction, therefore may be expected to produce improved clinical outcomes.     

In vivo evaluation of virtual electrode mapping and ablation utilizing a direct endocardial visualization ablation catheter

Visualization Catheter with Virtual Electrode Ablation. Background: Radiofrequency (RF) ablation utilizing direct endocardial visualization (DEV) requires a “virtual electrode” to deliver RF energy while preserving visualization. This study aimed to: (1) examine the virtual electrode RF ablation efficacy; (2) determine the optimal power and duration settings; and (3) evaluate the utility of virtual electrode unipolar electrograms. Methods and Results: The DEV catheter lesions were compared to lesions formed using a 3.5 mm open irrigated tip catheter within the right atria of 12 sheep. Generator power settings for DEV were titrated from 12W, 14W and 16W for 20, 30 and 40 seconds duration with 25 mL/min saline irrigation. Standard irrigated tip catheter settings of 30W, 50°C for 30 seconds and 30 mL/min were used. The DEV lesions were significantly greater in surface area and both major and minor axes compared to irrigated tip lesions (surface area 19.43 ± 9.09 vs 10.88 ± 4.72 mm, P<0.01) with no difference in transmurality (93/94 vs 46/47) or depth (1.86 ± 0.75 vs 1.85 ± 0.57 mm). Absolute electrogram amplitude reduction was greater for DEV lesions (1.89 ± 1.31 vs 1.49 ± 0.78 mV, P = 0.04), but no difference in percentage reduction. Pre‐ablation pacing thresholds were not different between DEV (0.79 ± 0.36 mA) and irrigated tip (0.73 ± 0.25 mA) lesions. There were no complications noted during ablation with either catheter. Conclusions: Virtual electrode ablation consistently created wider lesions at lower power compared to irrigated tip ablation. Virtual electrode electrograms showed a comparable pacing and sensing efficacy in detecting local myocardial electrophysiological changes. (J Cardiovasc Electrophysiol, Vol. 23, pp. 88‐95, January 2012)     

New technique for retrograde left heart catheterization in aortic stenosis

Retrograde catheterization of the left ventricle in patients with aortic stenosis is frequently difficult and occasionally impossible. We have developed a new technique to facilitate this problem. A standard #8 “pigtail” catheter is preformed with a 145° angle 7 cm from the catheter tip. With this catheter in the ascending aorta, the preformed angle lifts the catheter tip leftward and superiorly, allowing a straight guidewire a direct approach to the orifice of the stenotic aortic valve. Utilizing this technique, we were able to cross the stenotic aortic valve in 26-29 consecutive patients with isolated aortic stenosis (mean gradient ± 0.22 cm₂, mean fluoroscopy time for crossing: 32 ± 40 seconds). The 145° angle also lifts the catheter off the posterior wall of the left ventricle and allows a more parallel alignment of the catheter with the long axis of the left ventricle, leading to a more stable position with less ventricular dysrhythmias during angiography. Thus a preformed angle in the “pigtail” catheter facilitates crossing of the stenotic aortic valve and produces a more stable position in the left ventricle.     

Transcatheter closure of the patent ductus arteriosus: A comparative study between occluding coils and the Rashkind umbrella device

This study was performed to evaluate the efficacy of transcatheter coil closure of the patent ductus arteriosus in comparison to our experience with the Rashkind umbrella device. Transcatheter coil closure of the patent ductus arteriosus has been reported with encouraging results. We present our experience with ducti up to 5.0 mm in diameter and report the short-term follow-up. We compare the results with our previous experience with the Rashkind umbrella device. Seventy-one patients underwent transcatheter coil closure. Median age was 3.1 years, and median weight was 13.6 kg. Mean ductus diameter was 2.0 ± 1.1 mm. These were compared with 105 patients who underwent transcatheter closure using a single Rashkind umbrella device. The median age was 3.2 years and the median weight was 14.0 kg. The mean ductus diameter for this group was 2.1 ± 0.6 mm. The ductus murmur in the coil group disappeared in all patients. Immediate (≤24 h), complete closure was achieved in 89% of the coil group as compared to 71% for the Rashkind umbrella device group (P < 0.005). Closure rate for the coil group was 97% at the 6-month follow-up, vs. 82% for the Rashkind umbrella device group at the 6–12-month follow-up (P ≤ 0.05). In almost all patients requiring more than one coil, the ductus was crossed serially from the aortic end. All patients with ductus diameter ≥3.0 mm required two or more coils. Eleven coils in six patients embolized to the pulmonary arteries. All coils except one were retrieved with subsequent successful coil placement. Sixty-seven patients (94%) in the coil group were discharged in ≤24 h. Transcatheter closure of the patent ductus arteriosus using multiple coils is a more effective technique than the Rashkind umbrella closure and has excellent short-term results. This can be performed safely as an outpatient procedure. © 1996 Wiley-Liss, Inc.     

Novel vascular sealing device for closure of percutaneous vascular access sites

To investigate the hemostatic capabilities of a novel vascular sealing device consisting of a balloon catheter and procoagulant, vascular sheaths were placed percutaneously in the femoral arteries of dogs. The sealing device was evaluated using the balloon catheter alone in six femoral arteries and with the addition of a procoagulant, in 21 femoral arteries. The balloon catheter alone was successfully deployed in six of six femoral arteries achieving immediate hemostasis. In a second study in which the procoagulant was delivered following balloon placement, the sealing device was successfully deployed and hemostasis was achieved in 20 of 21 attempts (95%) despite removal of the balloon catheter. In a subset of fully anticoagulated animals, hemostasis was achieved in the sealing device-treated arteries at 6.5 ± 3.4 minutes, but in none of the controls (P < 0.001). This novel vascular sealing device successfully achieves rapid hemostasis in normal and anticoagulated dogs following percutaneous vascular procedures. Cathet. Cardiovasc. Diagn. 45:82–88, 1998. © 1998 Wiley-Liss, Inc.     

Radiofrequency Delivery Through a Cooled Catheter Tip Allows the Creation of Larger Endomyocardial Lesions in the Ovine Heart

RF Lesions From Cooled Electrode. Introduction: The delivery of radiofrequency (RF) energy through conventional catheter electrodes is often associated with coagulation necrosis at the tissue-electrode interface, with resultant impedance rise and limited lesion size. This study was performed to examine the effects of catheter tip cooling during RF delivery, to test the hypothesis that such cooling would decrease the likelihood of impedance rise and allow the creation of larger endomyocardial lesions. Methods and Results: The experiments were performed in eight open chest, anesthetized sheep. RF lesions were created within both ventricular chambers of each animal through a catheter tip that could he cooled with a saline perfusate. Assignment of cooled versus non-cooled RF delivery to either ventricle was alternated from one animal to the next. In each set of experiments, lesion volumes relative to the mode of RF delivery were compared. The mean power delivered via the cooled electrode (22.04 ± 4.51 W) was significantly higher than that delivered via the noncooled electrode (6.10 ± 2.47 W; P < 0.001). The mean duration of RF delivery was 42.7 ± 11.2 sec for noncooled lesions versus 49.2 ± 6.8 sec for cooled lesions (P < 0.01). Mean lesion volume was 436.07 ± 177.00 mm³ for noncooled RF delivery versus 1247.78 ± 520.51 mm³ for cooled RF delivery (P < 0.001). This significantly larger lesion size with cooled RF delivery was associated with no instance of impedance rise in 27 attempts versus 11 impedance rises in 28 attempts with noncooled RF (P < 0.001). Conclusions: Delivery of RF energy through a cooled catheter tip allows the creation of larger endomyocardial lesions by limiting the occurrence of impedance rise despite the delivery of greater energy. These observations suggest that, under certain conditions, resistive tissue heating at a distance from the site of current delivery may play an important role in RF ablation therapy.     

Effect of stent design on reduction of elastic recoil: A comparison via quantitative intravascular ultrasound

The increase in minimum lumen diameter achieved by coronary stent placement can be further enhanced by reducing the immediate recoil that occurs after stent deployment. The effect of various stent designs—flexible coils, slotted tubes, and a locking stent—on minimization of postdilation stent recoil was evaluated using an in vitro model of circumferential compression. The stents were expanded to 7 atm (3.82 ± 0.02 mm); as pressure was reduced, lumen diameter and cross-sectional area (CSA) were determined by on-line intravascular ultrasound imaging (30 MHz) positioned inside the dilating balloon (n = 10–15 inflation-deflation cycles). Stent recoil was assessed by calculation of percent change in CSA from 7 atm to negative balloon pressure: −33.1 ± 5.6%(GR-II) and −22.4 ± 3.8%(Wiktor) in the coil stents; −20.0 ± 4.2%(JJIS coronary), −8.4 ± 2.6%(JJIS biliary), and −6.9 ± 1.5%(Multilink) in the slotted tube stents; and −1.9 ± 3.2%in the Navius ZR1 locking stent (P<0.05 vs. Multilink, P<0.0001 vs. others). A range of resistances to recoil is demonstrated by this model, with coil stent designs undergoing greater elastic recoil than slotted tube stent designs. The locking stent design demonstrated the greatest radial strength and the most reduction in elastic recoil. Cathet. Cardiovasc. Intervent. 47:251–257, 1999. Published 1999 Wiley-Liss, Inc.     

Normal esophageal high‐resolution manometry and impedance values in the supine and sitting positions in the population of Northern China

The aim of this study was to investigate the normal high‐resolution manometry and impedance (HRiM) values in the supine and sitting positions in the population of Northern China, and to investigate the influence of different body positions and bolus consistency on esophageal HRiM findings. In this study, healthy volunteers in the supine position underwent esophageal HRiM examination of 10 swallows of 5 mL normal saline solution and 10 swallows of 5 mL synthetic gel of known viscosity, and in the sitting position of an additional five swallows of a synthetic gel of known viscosity. Total bolus transit time (TBTT), complete bolus transit rate (CBTR), distal contractile integral (DCI), distal esophageal amplitude (DEA), and integrated relaxation pressure (IRP) were measured. Sixty‐two healthy volunteers were examined in the supine position and 45 of these performed additional swallows of the viscous gel in the sitting position. In the supine position, normal values for swallowing the liquid and viscous boli were as follows: TBTT 6.9 ± 0.9 and 8.0 ± 1.2 s (P < 0.001), CBTR 90.3 ± 14.0 and 77.9 ± 20.3% (P < 0.001), DCI 1891.5 ± 1131.9 and 1967.8 ± 1140.1 mmHg.s.cm (P = 0.227), DEA 95.3 ± 35.4 and 98.7 ± 37.5 mmHg (P = 0.148), and IRP 10.4 ± 4.9 and 9.0 ± 4.2 mmHg (P < 0.001), respectively. For swallows of the viscous boli in the sitting position, TBTT, DCI, DEA, and IRP were significantly decreased, while CBTR was unchanged (P = 0.075). Normal HRiM values of the population of Northern China were established. Esophageal transit times of viscous boli were significantly slower, more often incomplete and produced less normal peristalsis in the supine position than swallows of liquid boli. Independent reference values for different manometric systems, body positions, and population need to be established before clinical application.     

Selective left endobronchial suctioning in the intubated patient

Suctioning of secretions from the left endobronchial tree is frequently necessary but often difficult in intubated patients. We examined the effectiveness of a catheter designed expressly for this purpose. Special curved tip (Bronchitrac-L) suction catheters were fitted with thin, radiopaque tubing to facilitate x-ray visualization. Eight-one attempts at left endobronchial placement were made on 74 stable adult intensive care unit patients. The suction catheter was inserted into the oral endotracheal tube or tracheostomy tube just prior to an x-ray filming of the chest. In 15 of 66 patients, the tip of the oral endotracheal tube was too distal (less than 2 cm above the carina) to allow proper functioning of the catheter. Patients with a properly positioned oral endotracheal tube were analyzed separately and showed 56 percent of the catheters went to the left bronchus. When the head was turned to the left prior to placement, successful left bronchus placement occurred in 65 percent. When the catheter was placed through a tracheostomy tube, 100 percent went into the left bronchus (n = 15). There were no catheter-induced complications in this study. The curved tip catheter is an effective means of suctioning the left bronchial tree in patients with tracheostomy tubes. Its reliability in patients with oral endotracheal tubes is reduced but more effective than current methods.     

Randomized Comparison of Multipolar,Duty‐Cycled,Bipolar‐Unipolar Radiofrequency Versus Conventional Catheter Ablation for Treatment of Common Atrial Flutter

Comparison of Radiofrequency Versus Conventional Catheter Ablation. Introduction: Radiofrequency (RF) catheter ablation has been established as an effective and curative treatment for atrial flutter (AFL). Approved methods include a drag‐and‐drop method, as well as a point‐by‐point ablation technique. The aim of this study was to compare the acute efficacy and procedural efficiency of a multipolar linear ablation catheter with simultaneous energy delivery to multiple catheter electrodes against conventional RF for treatment of AFL. Methods: Patients presenting to our department with symptomatic, typical AFL were enrolled consecutively and randomized to conventional RF ablation with an 8‐mm tip catheter (ConvRF) or a duty‐cycled, bipolar‐unipolar RF generator delivering power to a hexapolar tip‐versatile ablation catheter (T‐VAC) group. For both groups, the procedural endpoint was bidirectional cavotricuspid isthmus block. Results: Sixty patients were enrolled, 30 patients each assigned to ConvRF and T‐VAC groups. Total procedure time (40.2 ± 15.8 min vs 60.5 ± 12.7 min), energy delivery time (8.5 ± 3.7 min vs 14.7 ± 5.2 min), radiation dose (14.5 ± 3.5 cGy/cm² vs 31.7 ± 12.1 cGy/cm²), and the minimum number of RF applications needed to achieve block (4.2 ± 2.4 vs 8.9 ± 7.2) were significantly lower in the T‐VAC group. In 7 patients treated with the T‐VAC catheter, bidirectional block was achieved with less than 3 RF applications, versus no patients with conventional RF energy delivery. Conclusion: The treatment of typical AFL using a hexapolar catheter with a multipolar, duty‐cycled, bipolar‐unipolar RF generator offers comparable effectiveness relative to conventional RF while providing improved procedural efficiency. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1109‐1113)     

Initial clinical experience with cardiac resynchronization therapy utilizing a magnetic navigation system

Introduction: The placement of left ventricular (LV) leads during cardiac resynchronization therapy (CRT) involves many technical difficulties. These difficulties increase procedural times and decrease procedural success rates. Methods and Results: A total of 50 patients with severe cardiomyopathy (mean LV ejection fraction was 21 ± 6%) and a wide QRS underwent CRT implantation. Magnetic navigation (Stereotaxis, Inc.) was used to position a magnet‐tipped 0.014″ guidewire (Cronus? guidewire) within the coronary sinus (CS) vasculature. LV leads were placed in a lateral CS branch, either using a standard CS delivery sheath or using a “bare‐wire” approach without a CS delivery sheath. The mean total procedure time was 98.1 ± 29.1 minutes with a mean fluoroscopy time of 22.7 ± 15.1 minutes. The mean LV lead positioning time was 10.4 ± 7.6 minutes. The use of a delivery sheath was associated with longer procedure times 98 ± 32 minutes vs 80 ± 18 minutes (P = 0.029), fluoroscopy times 23 ± 15 minutes vs 13 ± 4 minutes (P = 0.0007) and LV lead positioning times 10 ± 6 minutes vs 4 ± 2 minutes (P = 0.015) when compared to a “bare‐wire” approach. When compared with 52 nonmagnetic‐assisted control CRT cases, magnetic navigation reduced total LV lead positioning times (10.4 ± 7.6 minutes vs 18.6 ± 18.9 minutes; P = 0.005). If more than one CS branch vessel was tested, magnetic navigation was associated with significantly shorter times for LV lead placement (16.2 ± 7.7 minutes vs 36.4 ± 23.4 minutes; P = 0.004). Conclusions: Magnetic navigation is a safe, feasible, and efficient tool for lateral LV lead placement during CRT. Magnetic navigation during CRT allows for control of the tip direction of the Cronus? 0.014″ guidewire using either a standard CS delivery sheath or “bare‐wire” approach. Although there are some important limitations to the 0.014″ Cronus? magnetic navigation can decrease LV lead placement times compared with nonmagnetic‐assisted control CRT cases, particularly if multiple CS branches are to be tested.     

Usefulness of catheterless radiotelemetry pH monitoring system to examine the relationship between duodenal acidity and upper gastrointestinal symptoms

Background and Aim: To clarify the usefulness of a newly designed method for measuring intraduodenal pH to examine the relationship between duodenal acidity and upper gastrointestinal symptoms during intragastric acid infusion. Methods: The study subjects were six healthy volunteers. A Bravo pH capsule with thread fixed to the gastric wall was endoscopically introduced into the second portion of the duodenum, and intraduodenal acidity was measured during intragastric infusion of 300 mL of 0.1 mol/L hydrochloric acid or pure water through an elemental diet tube. The severity of several upper gastrointestinal symptoms were assessed by using a 10‐cm visual analogue scale every 2 min for up to 30 min, and the area under the severity scale‐time curve (cm × min.) were calculated. Results: The percentage time during 30 min when the intraduodenal pH was < 4.0 and was significantly greater than during water infusion (61.4 ± 6.1% vs 24.8 ± 6.5%). Several upper gastrointestinal symptoms were observed during acid infusion (acid vs water epigastric heaviness, 29.1 ± 12.0 vs 2.7 ± 1.4; dull epigastric pain, 8.8 ± 4.9 vs 0.7 ± 0.7 cm × min/30 min). Intraduodenal pH below 4.0 was correlated with the severity of dull pain in the stomach (R² = 0.342, P = 0.044). Conclusion: The newly designed intraduodenal pH monitoring by using catheterless radiotelemetry system is useful to examine the relationship between duodenal acidity and upper gastrointestinal symptoms.     

Transhepatic therapeutic cardiac catheterization: A new option for the pediatric interventionalist

We evaluate the efficacy and safety of percutaneous transhepatic (TH) venous access for interventional cardiac catheterization. A retrospective review of all TH therapeutic catheterizations between January 1994 and September 1998 was performed. Patient demographics, pre- and postcatheterization hemoglobin and liver function studies, and complications were evaluated. TH access was performed for 30 interventional catheterizations in 25 patients with a median age of 39 months (range, 1 day to 41 years) and weight of 13.2 kg (3.1–87.0 kg). Indications for TH access were bilateral obstructed femoral veins (n = 15), obstructed femoral veins and superior vena cava (n = 3), Greenfield filter (n = 2), and presumptive improved route for intervention via TH access (n = 5). TH interventions were successful in 29/30 procedures (97%). Interventions via TH sheath sizes of 4–14 Fr included pulmonary angioplasty ± stent (n = 11), radiofrequency ablation (n = 4), atrial septal defect device occlusion (n = 2), coil occlusion of pulmonary artery pseduoaneurysm (n = 2), Fontan fenestration device occlusion (n = 2), pulmonary valvuloplasty (n = 2), stent dilation of the superior vena cava (n = 2), and one each of device retrieval, Fontan baffle stent placement and subsequent redilation, Fontan fenestration dilation, transseptal mitral valvuloplasty, and cardiac biopsy. There were no changes in pre- and post-TH hemoglobin levels (mean ± SD, 12.9 ± 2.2 vs. 11.9 ± 1.9 gm/dL; P = NS) or alanine transferase (34.0 ± 27.5 vs. 43.4 ± 18.2 IU/L; P = NS). One patient developed important intraperitoneal bleeding and required exploratory laporatomy. Percutaneous TH access is safe and effective as a route for interventional catheter procedures for patients with limited venous access. Cathet. Cardiovasc. Intervent. 47:41–45, 1999. © 1999 Wiley-Liss, Inc.     

Temperature-controlled Radiofrequency Catheter Ablation of Accessory Pathways and Atrioventricular Nodal Reentrant Tachycardia: The 5-French Catheter Approach

Ablation with Temperature-Controlled 5-French Catheters. Introduction: In the present study, we assessed the feasibility of radiofrequency (RF) ablation of accessory pathways and AV nodal reentrant tachycardias with novel 5-French catheters with 4-mm tip electrodes using established mapping criteria and temperature-controlled power output control. Methods and Results: In this prospective study, 60 consecutive adult patients (mean age 36 ± 20 years) with accessory pathways (n = 37; 24 left-sided) or AV nodal reentrant tachycardia (n = 23) underwent RF catheter ablation. A 5-French catheter with a 4-mm tip electrode and an embedded thermistor was used for RF application. The surface of the tip electrodes was 26 mm2 compared to 38 mm² of 7-French catheters with 4-mm tip electrodes from the same catheter series. Power output was automatically and continuously adjusted according to the preset catheter tip temperature of 60° to 70°C. Pulse duration was 90 seconds. For left-sided accessory pathways, the retrograde route via the femoral artery was used. After removing the 5-French sheaths, only 4 hours of bed rest were advised. For ablation of AV nodal reentrant tachycardia, the so-called slow pathway was targeted for ablation. Acute success was achieved in 34 (92%) of 37 patients with accessory pathways and 23 (100%) of 23 patients with AV nodal reentrant tachycardia. A mean of 3 ± 4 RF pulses (median 2 pulses; range 1 to 20 pulses) was applied. The mean fluoroscopy time was 26 ± 21 minutes. No complete AV block or other procedure-related complications were observed. Recurrences occurred in 2 patients with accessory pathways and in 2 patients with AV nodal reentrant tachycardia during a follow-up of 9 ± 4 months. Conclusions: Temperature-controlled RF ablation of accessory pathways and AV nodal reentrant tachycardia in adults using 5-French catheters is feasible, effective, and safe. Ablation with 5-French catheters might help to reduce the complication rate of catheter ablation techniques.     

Placement of endoscopic naso-biliary drainage does not preclude subsequent percutaneous transhepatic biliary drainage

We prospectively investigated whether the placement of endoscopic naso-biliary drainage (ENBD) precluded percutaneous transhepatic biliary drainage (PTBD). In 40 patients, the caliber of the intrahepatic bile duct was measured prior to ENBD by ultrasonography. When PTBD was required after ENBD, the ENBD catheter was clamped for 1 to 2 h before PTBD, and its caliber was again measured at the time of PTBD. When PTBD was performed within 7 days (mean, 1.8 days) after ENBD (n = 27), the size of the intrahepatic bile duct was 5.0 ± 2.3 mm before and 4.6 ± 2.3 mm after ENBD. There was no significant difference between these values (P > 0.5). When PTBD was performed 8 to 40 days (mean, 17.8 days) after ENBD (n = 13), the bile duct diameter was significantly reduced, from 4.2 ± 1.5 mm (pre-ENBD) to 1.8 ± 1.7 mm (post-ENBD) (P < 0.05). When PTBD was conducted within 7 days (mean, 1.8 days) after ENBD, previous ENBD did not induce collapse of the bile duct, if the ENBD catheter was clamped for 1 to 2 h before the puncture of the bile duct. Received: July 30, 1999 / Accepted: November 26, 1999     

Comparison of epicardial cryoablation and irrigated radiofrequency ablation in a Swine infarct model

Epicardial Cryoablation in Swine. Introduction: Cryoablation is an alternative to radiofrequency (RF) energy used in some ablation procedures. Its role and effectiveness compared to irrigated RF in epicardial tissue and epicardial substrates is not yet fully established. Methods and Results: Using a swine chronic infarct model, we compared RF lesions produced by an open‐irrigated 3.5 mm tip catheter with those produced by an 8 mm tip cryocatheter in epicardial infarct border zone, epicardial normal tissue, and normal endocardium. In the infarct border zone, cryolesions were larger than RF lesions in maximum diameter (9.3 ± 2.9 mm vs 6.2 ± 2 mm, P < 0.001) and volume (171.7 ± 173.1 mm³ vs 77 ± 53.5 mm³, P = 0.021). In normal epicardial tissue, cryolesions were larger in maximum diameter (11.2 ± 4.3 mm vs 7.7 ± 3.1 mm, P = 0.012), depth (5.8 ± 1.6 mm vs 4.7 ± 1.4 mm, P = 0.034), and volume (274.7 ± 242.2 mm³ vs 112 ± 102.9 mm³, P = 0.002). In normal endocardium, no significant differences were found. Conclusions: Epicardial cryoablation with an 8 mm tip cryocatheter led to larger lesion volume in infarcted myocardium compared to a 3.5 mm irrigated RF catheter. This is likely related to a combination of cryoadherence, more efficient energy delivery with horizontal orientation, and lack of warming by circulating blood. Cryoablation merits further investigation as a modality for treating ventricular tachycardia of epicardial origin in humans. (J Cardiovasc Electrophysiol, Vol. 23, pp. 1016‐1023, September 2012)     

Low-Energy Transvenous Cardioversion of Atrial Fibrillation Using a Single Atrial Lead System

Atrial Cardioversion Using a Single Atrial Lead System. Introduction: Clinical studies have shown that electrical conversion of atrial fibrillation (AF) is feasible with transvenous catheter electrodes at low energies. We developed a single atrial lead system that allows atrial pacing, sensing, and defibrillation to improve and facilitate this new therapeutic option. Methods and Results: The lead consists of a tripolar sensing, pacing, and defibrillation system. Two defibrillation coil electrodes are positioned on a stylet-guided lead. A ring electrode located between the two coils serves as the cathode for atrial sensing and pacing. We used this lead to cardiovert patients with acute or chronic AE. The distal coil was positioned in the coronary sinus, and the proximal coil and the ring electrode in the right atrium. R wave synchronized biphasic shocks were delivered between the two coils. Atrial signal detection and pacing were performed using the proximal coil and the ring electrode. Eight patients with acute AF (38 ± 9 min) and eight patients with chronic AF (6.6 ± 5 months) were included. The fluoroscopy time for lead placement was 3.5 ± 4.3 minutes. The atrial defibrillation threshold was 2.0 ± 1.4 J for patients with acute AE and 9.2 ± 5.9 J for patients with chronic AF (P < 0.01). The signal amplitude detected was 1.7 ± 1.1 mV during AF and 4.0 ± 2.9 mV after restoration of sinus rhythm (P < 0.001). Atrial pacing was feasible at a threshold of 4.4 ± 3.3 V (0.5-msec pulse width). Conclusions: Atrial signal detection, atrial pacing, and low-energy atrial defibrillation using this single atrial lead system is feasible in various clinical settings. Tbis system might lead to a simpler, less invasive approach for internal atrial cardioversion.