Radiological anatomy of the obturator nerve and its articular branches: basis to develop a method of radiofrequency denervation for hip joint pain

OBJECTIVE: A previous study of radiofrequency neurotomy of the articular branches of the obturator nerve for hip joint pain produced modest results. Based on an anatomical and radiological study, we sought to define a potentially more effective radiofrequency method. DESIGN: Ten cadavers were studied, four of them bilaterally. The obturator nerve and its articular branches were marked by wires. Their radiological relationship to the bone structures on fluoroscopy was imaged and analyzed. A magnetic resonance imaging (MRI) study was undertaken on 20 patients to determine the structures that would be encountered by the radiofrequency electrode during different possible percutaneous approaches. RESULTS: The articular branches of the obturator nerve vary in location over a wide area. The previously described method of denervating the hip joint did not take this variation into account. Moreover, it approached the nerves perpendicularly. Because optimal coagulation requires electrodes to lie parallel to the nerves, a perpendicular approach probably produced only a minimal lesion. In addition, MRI demonstrated that a perpendicular approach is likely to puncture femoral vessels. Vessel puncture can be avoided if an oblique pass is used. Such an approach minimizes the angle between the target nerves and the electrode, and increases the likelihood of the nerve being captured by the lesion made. Multiple lesions need to be made in order to accommodate the variability in location of the articular nerves. CONCLUSIONS: The method that we described has the potential to produce complete and reliable nerve coagulation. Moreover, it minimizes the risk of penetrating the great vessels. The efficacy of this approach should be tested in clinical trials.

Steam pops during irrigated radiofrequency ablation: feasibility of impedance monitoring for prevention

BACKGROUND: Steam pops are a risk of irrigated radiofrequency catheter ablation (RFA) and may cause cardiac perforation. Data to guide radiofrequency (RF) energy titration to avoid steam pops are limited. OBJECTIVE: This study sought to assess the frequency and consequence of audible pops and to determine the feasibility of using the magnitude of impedance change to predict pops. METHODS: We reviewed consecutive endocardial open-irrigated RFA for ventricular tachycardia (VT) with continuously recorded ablation data in 142 patients with structural heart disease. Steam pops were defined as an audible pop associated with a sudden spike in impedance. Ablation lesions before or after pops served as controls. RESULTS: From a total of 4,107 ablation lesions, 62 (1.5%) steam pops occurred in 42 procedures in 38 patients. Perforation with tamponade occurred with 1 of 62 (2%) pops. Applications with pops had a greater impedance decrease (22 +/- 7 Omega vs. 18 +/- 8 Omega, P = .001) and a higher maximum power (45 +/- 5 W vs. 43 +/- 6 W, P = .011), but did not differ in maximum catheter tip temperature (40 degrees C +/- 4 degrees C vs. 40 degrees C +/- 4 degrees C, P = .180) from applications without pops. Eighty percent of pops occurred after impedance decreased by at least 18 Omega. CONCLUSION: During VT ablation with open irrigation, audible pops are infrequent and do not usually cause perforation. Limiting RF power to achieve an impedance decrease of <18 Omega is a feasible method of reducing the likelihood of a pop when perforation risk is of concern.

Device-less patent foramen ovale closure by radiofrequency thermal energy

The goal of this study was to assess the feasibility, safety and success of a system which uses radiofrequency energy (RFE) rather than a device for percutaneous closure of patent foramen ovale (PFO). METHODS: Sixteen patients (10 men, 6 women, mean age 50 years) were included in the study. All of them had a proven PFO with documented right-to-left shunt (RLS) after Valsalva manoeuvre (VM) during transoesophageal echocardiography (TEE). The patients had an average PFO diameter of 6 +/- 2 mm at TEE and an average of 23 +/- 4 microembolic signals (MES) in power M-mode transcranial Doppler sonography (pm-TCD), measured over the middle cerebral artery. An atrial septal aneurysm (ASA) was present in 7 patients (44%). Balloon measurement, performed in all patients, revealed a stretched PFO diameter of 8 +/- 3 mm. In 2 patients (stretched diameter 11 and 14 mm respectively, both with ASA >10 mm), radiofrequency was not applied (PFO too large) and the PFO was closed with an Amplatzer PFO occluder instead. A 6-month follow-up TEE was performed in all patients. RESULTS: There were no serious adverse events during the procedure or at follow-up (12 months average). TEE 6 months after the first RFE procedure showed complete closure of the PFO in 50% of the patients (7/14). Closure appeared to be influenced by PFO diameter, complete closure being achieved in 89% (7/8) with a balloon-stretched diameter < or =7 mm but in none of the patients >7 mm. Only one of the complete closure patients had an ASA. Of the remainder, 4 (29%) had an ASA. Although the PFO was not completely closed in this group, some reduction in the diameter of the PFO and in MES was documented by TEE and pm-TCD with VM. Five of the 7 residual shunt patients received an Amplatzer PFO occluder. Except for one patient with a minimal residual shunt, all showed complete closure of PFO at 6-month follow-up TEE and pm-TCD with VM. The other two refused a closure device. CONCLUSIONS: The results confirm that radiofrequency closure of the PFO is safe albeit less efficacious and more complex than device closure. The technique in its current state should not be attempted in patients with a balloon-stretched PFO diameter >7 mm and an ASA.

Statistical analysis of personal radiofrequency electromagnetic field measurements with nondetects

Exposimeters are increasingly applied in bioelectromagnetic research to determine personal radiofrequency electromagnetic field (RF-EMF) exposure. The main advantages of exposimeter measurements are their convenient handling for study participants and the large amount of personal exposure data, which can be obtained for several RF-EMF sources. However, the large proportion of measurements below the detection limit is a challenge for data analysis. With the robust ROS (regression on order statistics) method, summary statistics can be calculated by fitting an assumed distribution to the observed data. We used a preliminary sample of 109 weekly exposimeter measurements from the QUALIFEX study to compare summary statistics computed by robust ROS with a naïve approach, where values below the detection limit were replaced by the value of the detection limit. For the total RF-EMF exposure, differences between the naïve approach and the robust ROS were moderate for the 90th percentile and the arithmetic mean. However, exposure contributions from minor RF-EMF sources were considerably overestimated with the naïve approach. This results in an underestimation of the exposure range in the population, which may bias the evaluation of potential exposure-response associations. We conclude from our analyses that summary statistics of exposimeter data calculated by robust ROS are more reliable and more informative than estimates based on a naïve approach. Nevertheless, estimates of source-specific medians or even lower percentiles depend on the assumed data distribution and should be considered with caution.

Transcatheter closure of patent foramen ovale with radiofrequency: acute and intermediate term results in 144 patients

AIMS: Currently available devices for transcatheter closure of patent foramen ovale (PFO) which rely on a permanent implant have limitations, including late complications. The study objective was to evaluate the safety, feasibility, and effectiveness of the PFx Closure System, the first transcatheter technique for PFO closure without an implantable device. METHODS AND RESULTS: A prospective study of 144 patients was conducted at nine clinical sites from October 2005 through August 2007. All patients had a history of cryptogenic stroke, transient ischemic attack, migraines, or decompression illness. The mean balloon stretched diameter of the PFO was 7.9 +/- 2.5 mm. Technical success (successful application of radiofrequency energy) was achieved in 130 patients. One patient required a transfusion as a result of blood loss during the procedure. There were no other major procedural complications. There were no recurrent strokes, deaths, conduction abnormalities, or perforations following the procedure. At a mean follow-up of 6 months, successful closure was achieved in 79 patients (55%). In PFOs with balloon sized or stretched diameters less than 8 mm, the closure rate was 72% (53/74). CONCLUSION: This study demonstrates that transcatheter closure of a PFO without a permanent implant is technically feasible and safe. Further technique and device modifications are required to achieve higher closure rates.

Feasibility and safety of same-day home discharge after radiofrequency catheter ablation

Interventional cardiology in a day-case setting might reduce logistic constraints on hospital resources. However, in contrast with coronary angioplasty, few data support the feasibility and safety of radiofrequency catheter ablation (RCA). The aim of this prospective, multicenter cohort study was to evaluate the feasibility and safety of RCA in 1,342 patients (814 men; mean age 57 +/- 17 years) considered eligible for ambulatory RCA, according to specific set of criteria, for common atrial flutter (n = 632), atrioventricular nodal reentrant tachycardia (n = 436), accessory pathways (n = 202), and atrial tachycardia (n = 72). Patients suitable for early discharge (4 to 6 hours after uncomplicated RCA) were scheduled for 1-month follow-up. Predictive factors for delayed complications were studied by multivariate analysis. Of the 1,342 enrolled patients, 1,270 (94.6%) were discharged the same day and followed for 1 month; no deaths occurred, and the readmission rate was 0.79% (95% confidence interval 0.30% to 1.27%). Six patients had significant puncture complications, 2 presented with symptomatic delayed pulmonary embolism, and 2 had new onset of poorly tolerated atrial flutter. None of these complications was life threatening. Multivariate analysis did not identify any significant independent predictors for delayed complications. In conclusion, these data suggest that same-day discharge after uncomplicated RCA for routine supraventricular arrhythmias is safe and may be applicable in clinical practice. This approach is known to be associated with significant patient satisfaction and cost savings and can be considered a first-line option in most patients who undergo routine ablation procedures.

Delayed development of pneumothorax after pulmonary radiofrequency ablation

Acute pneumothorax is a frequent complication after percutaneous pulmonary radiofrequency (RF) ablation. In this study we present three cases showing delayed development of pneumothorax after pulmonary RF ablation in 34 patients. Our purpose is to draw attention to this delayed complication and to propose a possible approach to avoid this major complication. These three cases occurred subsequent to 44 CT-guided pulmonary RF ablation procedures (6.8%) using either internally cooled or multitined expandable RF electrodes. In two patients, the pneumothorax, being initially absent at the end of the intervention, developed without symptoms. One of these patients required chest drain placement 32 h after RF ablation, and in the second patient therapy remained conservative. In the third patient, a slight pneumothorax at the end of the intervention gradually increased and led into tension pneumothorax 5 days after ablation procedure. Underlying bronchopleural fistula along the coagulated former electrode track was diagnosed in two patients. In conclusion, delayed development of pneumothorax after pulmonary RF ablation can occur and is probably due to underlying bronchopleural fistula, potentially leading to tension pneumothorax. Patients and interventionalists should be prepared for delayed onset of this complication, and extensive track ablation following pulmonary RF ablation should be avoided.

Endocardial versus epicardial ventricular radiofrequency ablation: utility of in vivo contact force assessment.

BACKGROUND Contact force (CF) is an important determinant of lesion formation for atrial endocardial radiofrequency ablation. There are minimal published data on CF and ventricular lesion formation. We studied the impact of CF on lesion formation using an ovine model both endocardially and epicardially. METHODS AND RESULTS Twenty sheep received 160 epicardial and 160 endocardial ventricular radiofrequency applications using either a 3.5-mm irrigated-tip catheter (Thermocool, Biosense-Webster, n=160) or a 3.5 irrigated-tip catheter with CF assessment (Tacticath, Endosense, n=160), via percutaneous access. Power was delivered at 30 watts for 60 seconds, when either catheter/tissue contact was felt to be good or when CF>10 g with Tacticath. After completion of all lesions, acute dimensions were taken at pathology. Identifiable lesion formation from radiofrequency application was improved with the aid of CF information, from 78% to 98% on the endocardium (P<0.001) and from 90% to 100% on the epicardium (P=0.02). The mean total force was greater on the endocardium (39±18 g versus 21±14 g for the epicardium; P<0.001) mainly because of axial force. Despite the force-time integral being greater endocardially, epicardial lesions were larger (231±182 mm(3) versus 209±131 mm(3); P=0.02) probably because of the absence of the heat sink effect of the circulating blood and covered a greater area (41±27 mm(2) versus 29±17 mm(2); P=0.03) because of catheter orientation. CONCLUSIONS In the absence of CF feedback, 22% of endocardial radiofrequency applications that are thought to have good contact did not result in lesion formation. Epicardial ablation is associated with larger lesions.

Radiofrequency ablation of multiple accessory pathways

The aim of the study was to review the clinical and electrophysiological characteristics and results of radiofrequency catheter ablation in patients with multiple accessory pathways to compare them with those of patients with single accessory pathways. Electrophysiological study and radiofrequency catheter ablation were performed in 1010 consecutive cases with Wolff Parkinson White Syndrome. Presence of multiple accessory pathways was documented in 31 patients (3.1%); 30 had two, and 1 had three accessory pathways. Of the 63 accessory pathways, 42 were manifest and 21 concealed. Nine patients had Ebstein's anomaly associated with atrioventricular bypass tracts. The most common combination was right posteroseptal with right free wall bypass tracts (15 patients with 30 accessory pathways). Fifty-one of the sixty-three accessory pathways (81%) were ablated successfully without complications. The duration of the procedure was 100 +/- 58 min and the fluoroscopic time 40 +/- 17 min. A follow up of 5 +/- 3 years after ablation, demonstrated recurrences of six accessory pathways (9.5%). In conclusion, patients with multiple accessory pathways can be treated by radiofrequency ablation in only one session with a high success rate although slightly less than that in patients with a single accessory pathway (81% vs 93%, P<0.01).

Radiofrequency catheter ablation of idiopathic ventricular tachycardia originating in the main stem of the pulmonary artery.

We report the case of a patient in whom successful radiofrequency catheter ablation of an idiopathic ventricular tachycardia (VT) originating in the main stem of the pulmonary artery was performed. After successful ablation of the index arrhythmia, which was an idiopathic right ventricular outflow tract VT, a second VT with a different QRS morphology was reproducibly induced. Mapping of the second VT revealed the presence of myocardium approximately 2 cm above the pulmonary valve. Application of radiofrequency energy at this site resulted in termination and noninducibility of this VT. After 6-month follow-up, the patient remained free from VT recurrences.

Perception of atrial fibrillation before and after radiofrequency catheter ablation: relevance of asymptomatic arrhythmia recurrence.

BACKGROUND The objective of this study was to assess the incidence and impact of asymptomatic arrhythmia in patients with highly symptomatic atrial fibrillation (AF) who qualified for radiofrequency (RF) catheter ablation. METHODS AND RESULTS In this prospective study, 114 patients with at least 3 documented AF episodes together with corresponding symptoms and an ineffective trial of at least 1 antiarrhythmic drug were selected for RF ablation. With the use of CARTO, circumferential lesions around the pulmonary veins and linear lesions at the roof of the left atrium and along the left atrial isthmus were placed. A continuous, 7-day, Holter session was recorded before ablation, right after ablation, and after 3, 6, and 12 months of follow-up. During each 7-day Holter monitoring, the patients recorded quality and duration of any complaints by using a detailed symptom log. More than 70,000 hours of ECG recording were analyzed. In the 7-day Holter records before ablation, 92 of 114 patients (81%) had documented AF episodes. All episodes were symptomatic in 35 patients (38%). In 52 patients (57%), both symptomatic and asymptomatic episodes were recorded, whereas in 5 patients (5%), all documented AF episodes were asymptomatic. After ablation, the percentage of patients with only asymptomatic AF recurrences increased to 37% (P<0.05) at the 6-month follow-up. An analysis of patient characteristics and arrhythmia patterns failed to identify a specific subset who were at high risk for the development of asymptomatic AF. CONCLUSIONS Even in patients presenting with highly symptomatic AF, asymptomatic episodes may occur and significantly increase after catheter ablation. A symptom-only-based follow-up would substantially overestimate the success rate. Objective measures such as long-term Holter monitoring are needed to identify asymptomatic AF recurrences after ablation.

Electrocardiographic pattern as a guide for management and radiofrequency ablation of idiopathic ventricular tachycardia.

BACKGROUND Idiopathic ventricular tachycardia (VT) often originates from the right ventricular outflow tract (RVOT), but foci deep to the endocardium, in the epicardium, or in the left ventricle are not uncommon. Although these extra-RVOT foci can be targeted with ablation, risks involved are higher and success rates lower. Simple electrocardiographic (ECG) criteria allowing (1) discrimination of RVOT foci from extra-RVOT foci and (2) assessment of the chance of success of a right heart ablation procedure are desirable. METHODS Twenty-five consecutive patients referred for radiofrequency (RF) ablation of idiopathic VT or severely symptomatic idiopathic ventricular premature contractions were included. Localization of VT origin and success rates of VT ablation in the RVOT were analyzed according to the ECG pattern. RESULTS The analysis of the R wave in V2 was the strongest single predictor of whether the VT had an RVOT or an extra-RVOT origin. An R wave amplitude < or =30% of the QRS amplitude designated the VT focus in the RVOT with positive and negative predictive values of 95 and 100%, respectively. Analysis of R wave duration in V2 had similar predictive values, whereas the R/S transition zone in precordial leads had slightly lower predictive values. Seventeen of 20 arrhythmias (85%) with an R wave amplitude < or =30% of the QRS amplitude in V2 could be successfully abolished by an exclusively right heart procedure. CONCLUSIONS The analysis of ECG pattern makes it possible to guide the management of patients with idiopathic VT in predicting the arrhythmias that can be safely targeted with RF ablation from the RVOT with high success rates.

Stable secondary arrhythmias late after intraoperative radiofrequency ablation of atrial fibrillation: incidence, mechanism, and treatment.

INTRODUCTION Intraoperative radiofrequency (RF) ablation is an effective treatment of atrial fibrillation (AF). However, secondary arrhythmias late after ablation may complicate the patient's course. We report on the incidence, mechanisms, and treatment of gap-related atrial flutter and other secondary arrhythmias during long-term follow-up. METHODS AND RESULTS In 129 patients who underwent intraoperative RF ablation with placement of left atrial linear lesions using minimally invasive surgical techniques, secondary arrhythmias were analyzed during long-term follow-up (20 +/- 6 months). Transient atrial arrhythmias during the first 3 postoperative months were excluded. In 8 (6.2%) of 129 patients, sustained stable secondary arrhythmias were documented. Left atrial, gap-related atrial flutter was observed in 4 patients (3.1%). The flutter was treated by percutaneous RF ablation in 3 patients (2.3%) and with drugs in 1 patient (0.8%). In 2 patients (1.6%), right atrial isthmus-dependent atrial flutter occurred and was treated successfully by percutaneous RF ablation. In 2 patients (1.6%), ectopic right atrial tachycardias occurred and were treated with percutaneous RF ablation. CONCLUSION Late after intraoperative RF ablation of atrial fibrillation, three types of stable secondary arrhythmias were observed in 6% of patients: left atrial gap-related atrial flutter, right atrial isthmus-dependent atrial flutter, and ectopic atrial tachycardia. Gaps after intraoperative RF ablation due to noncontinuous or nontransmural linear lesions may lead to stable left atrial macroreentrant tachycardias, requiring new interventional therapy.

The Effect of Open-Irrigated Radiofrequency Catheter Ablation of Atrial Fibrillation on Left Atrial Pressure and B-Type Natriuretic Peptide

Background Open-irrigated radiofrequency catheter ablation (oiRFA) of atrial fibrillation (AF) imposes a volume load and risk of pulmonary edema. We sought to assess the effect of volume administration during ablation on left atrial (LA) pressure and B-type natriuretic peptide (BNP). Methods LA pressure was measured via transseptal sheath at the beginning and end of 44 LA ablation procedures in 42 patients. BNP plasma levels were measured before and after 10 procedures. Results A median of 3,255 (interquartile range [IQR], 2,014)-mL saline was administered during the procedure. During LA ablation, the median fluid balance was +1,438 (IQR, 1,109) mL and LA pressure increased by median 3.7 (IQR, 5.9) mm Hg (P < 0.001). LA pressure did not change in the 19 procedures with furosemide administration (median ΔP = −0.3 [IQR, 7.1] mm Hg, P = 0.334). The correlation of LA pressure and fluid balance was weak (rs = 0.383, P = 0.021). BNP decreased in all four procedures starting in AF or atrial tachycardia and then converting to sinus rhythm (P = 0.068), and increased in all six procedures starting and finishing in sinus rhythm (P = 0.028). After ablation, symptomatic volume overload responding to diuresis occurred in three patients. Conclusions A substantial intravascular volume load during oiRFA can be absorbed with little change in LA pressure, such that LA pressure is not a reliable indicator of the fluid balance. Subsequent redistribution of the volume load imposes a risk after the procedure. Conversion to sinus rhythm may improve ability to acutely accommodate the volume load.