Patients Undergoing Radiofrequency Catheter Ablation Research Articles

Shifting of puncture site in the fossa ovalis during radiofrequency catheter ablation: intracardiac echocardiography-guided transseptal left heart catheterization.

Intracardiac echocardiography (ICE) serves as an adjunct to fluoroscopy for electrophysiological procedures by identifying critical anatomic landmarks and confirming catheter-endocardial contact. In the present study, we investigated the usefulness of ICE for radiofrequency catheter ablation. ICE was utilized to guide transseptal puncture in 19 patients undergoing radiofrequency catheter ablation. The fossa ovalis, which was one critical anatomic landmark, had an average vertical diameter of 18.5 +/- 6.9 mm and an average horizontal diameter of 10.0 +/- 2.4 mm, as measured by ICE and fluoroscopy. Although there was only a small shift of the puncture site in the horizontal direction, the puncture site shifted towards the upper edge of the fossa ovalis for 17 patients (89%). Furthermore, we could verify that the distance between the apex of the tent-shape formed by the pressure of the puncture needle in the fossa ovalis and the left atrial wall opposing it was sufficient to carry out the procedure safely. Confirming the puncture site using ICE is useful in carrying out transseptal left heart catheterization safely.

Ablation of atrial tachycardia originating from the vicinity of the atrioventricular node: significance of mapping both sides of the interatrial septum

OBJECTIVES The purpose of the study was to examine the value of right- and left-sided mapping to identify the site of tachycardia origin. BACKGROUND Focal atrial tachycardia may originate from the vicinity of the atrioventricular node from either side of the interatrial septum. METHODS In 16 patients undergoing radiofrequency catheter ablation of perinodal atrial tachycardia, activation mapping of the right and left side of the interatrial septum was performed. RESULTS Atrial tachycardia originated from the right side of the interatrial septum in 10 patients (group A) and from the left side in 6 patients (group B). On the right side, earliest atrial activity preceded the onset of the P-wave by 49 ± 15 ms in group A and by 38 ± 8 ms in group B (NS), and it preceded the signal recorded from the right atrial appendage by 59 ± 19 ms in group A and by 60 ± 13 ms in group B (NS). On the left side, earliest activity preceded the onset of the P-wave by 27 ± 16 ms in group A and by 51 ± 6 ms in group B (<0.01), and it preceded the signal obtained from the right atrial appendage by 38 ± 19 ms in group A and by 73 ± 9 ms in group B (<0.01). Atrial tachycardias were successfully eliminated in all patients without impairment of atrioventricular conduction. During follow-up, two patients had a recurrence of tachycardia. CONCLUSIONS Mapping of only the right side cannot exclude a left-sided origin. Therefore, mapping of both sides of the interatrial septum is required prior to ablation of focal atrial tachycardia originating from the vicinity of the atrioventricular node.

Radiofrequency catheter ablation of left-sided accessory pathways in pediatric patients

In many cases, radiofrequency catheter ablation has replaced the long-term use of antiarrhythmic medication for symptomatic tachycardia, and has all but eliminated arrhythmia surgery. The most common substrate for radiofrequency catheter ablation in pediatric patients is atrioventricular (AV) reentry tachycardia due to a concealed or manifest accessory pathway. Accessory pathways are distributed unevenly along the right and left atrioventricular valve annuli, and left-sided accessory pathways are most common. Although some centers advocate an abbreviated diagnostic and mapping approach to both concealed and manifest left-sided accessory pathways, most still use a complete electrophysiological evaluation and complex catheter manipulation for mapping, followed by the application of radiofrequency energy. Left-sided accessory pathways may be approached from the transatrial approach, the retrograde aortic approach, or less commonly from within the coronary sinus. Each approach has proven to be associated with success, but also with a distinct set of risks. Possibly because left-sided accessory pathways are most common, catheter ablation of this substrate has proven highly successful and has the lowest risk of recurrence. However, recent data also suggest that this substrate is associated with greater risk of complications than of right-sided accessory pathways or pathways located in the posteroseptal region. The following report reviews some of the recently described diagnostic and mapping techniques, success rates, risks and follow-up data in pediatric patients undergoing radiofrequency catheter ablation of left-sided accessory pathways.

Electrocardiographic predictors of successful ablation of tachycardia or bigeminy arising in the right ventricular outflow tract

Among various electrocardiographic variables, the QRS duration in V2 was found to be the best discriminator of outcome in patients undergoing radiofrequency catheter ablation of the right ventricular outflow tract tachycardia and/or bigeminy. If the QRS duration is <160 ms in lead V2, the probability of successful ablation is lower than if the QRS duration is longer.

Safety and Feasibility of Same Day Discharge in Patients Undergoing Radiofrequency Catheter Ablation

We retrospectively analyzed outcomes of radiofrequency catheter ablation in patients who were discharged the same day and compared them with patients staying overnight. For most tachyarrhythmias, it is safe and feasible to discharge patients undergoing radiofrequency ablation on the same day.

Nausea and vomiting in patients undergoing radiofrequency catheter ablation

Radiofrequency catheter ablation is a technique for curing cardiac arrhythmias by destroying tissue that is a critical part of the targeted electrical circuit. Nausea and vomiting have been observed after use of this technique, but no study to date has examined these complications. To determine the incidence of nausea and vomiting after radiofrequency catheter ablation, determine factors related to nausea and vomiting, and evaluate the antiemetic efficacy of promethazine given during the procedure. Medical records for 369 cases of radiofrequency catheter ablation performed in a 4-year period at a university medical center were reviewed. Nausea after the procedure was documented in 22% of cases. Logistic regression analysis based on variables significant in bivariate analysis revealed that younger age, female sex, and longer procedure duration were significantly and independently related to nausea. Vomiting after the procedure occurred in 13% of cases. Logistic regression revealed that younger age and longer procedure duration were significantly and independently related to vomiting. Further analysis showed that patients who received larger doses of promethazine relative to the dose of fentanyl had a significantly lower incidence of vomiting. Nausea and vomiting occurred in a considerable number of cases. Female sex, younger age, and longer procedure duration increased the risk of nausea, whereas only age and procedure duration were associated with vomiting. This study may guide clinicians to use a prophylactic antiemetic in patients undergoing radiofrequency catheter ablation, especially patients at increased risk for nausea and vomiting.

Pretreatment With Aspirin and Ticlopidine Confers Lower Thrombogenic Potential of Radiofrequency Catheter Ablation

In the present study we pretreated 31 patients undergoing radiofrequency catheter ablation (RFA) with combined aspirin and ticlopidine for 3 days before the procedure, whereas 37 patients did not receive pretreatment. D-dimer levels reflecting the thrombogenic potential of RFA were significantly lower in the pretreated group at each stage before, during, and after the procedure, whereas there were no significant differences between the 2 groups in the number of RFA lesions or duration of the procedure.

Alterations in heart rate following radiofrequency ablation in the treatment of reentrant supraventricular arrhythmias: relation to alterations in autonomic tone.

To determine the relation between the creation of endocardial lesions and alterations in autonomic tone, we analyzed heart rate variability in patients undergoing radiofrequency catheter ablation for symptomatic supraventricular tachycardia. Elevated heart rates are frequently noted after radiofrequency catheter ablation for supraventricular arrhythmias. It has been postulated that this elevation may be secondary to alterations in cardiac autonomic tone. Since heart rate variability is a measure of autonomic nervous system activity, we used this technique to examine the heart rate elevation and to characterize postablation autonomic changes. Thirty-eight patients undergoing 44 radiofrequency catheter ablation procedures were included in the study. Total arrhythmic substrates treated included 34 accessory pathways and 13 AV nodes with dual physiology. Twenty-four hour ambulatory electrocardiographic recordings were obtained in a drug-free state prior to, ablation early postablation, and late postablation. Spectral and nonspectral analyses of heart rate variability were performed. Subgroup analyses were also done on specific cohorts. Subgroups included patients undergoing accessory pathway ablations, AV node modifications, and ablation of septal and nonseptal targets. To determine whether the amount of tissue damage was related to changes in heart rate variability, we analyzed the relation between the total energy delivered to the endocardium and the peak change in creatine kinase and heart rate variability. In this population, a significant transient increase in heart rate was noted following radiofrequency ablation. All time and frequency domain parameters of heart rate variability showed significant reversible decreases. These changes were independent of target site and arrhythmia substrate. There was no correlation noted between the changes in heart rate variability and either the total amount of energy applied to the endocardium or the change in creatine kinase. Increased heart rates and decreased heart rate variability occur following radiofrequency catheter ablation for supraventricular tachycardia. Clinically, the predominant effect is that of decreased parasympathetic tone. Since these transient changes are independent of arrhythmic substrate or ablation site in the atria, a rich parasympathetic innervation of the heart is proposed.

Influence of radiofrequency catheter ablation on myocardial metabolism

We investigated the change of the arterial-coronary sinus lactate difference before and after radiofrequency ablation to assess the influence of radiofrequency ablation on myocardial metabolism. Sixteen patients underwent radiofrequency catheter ablation and blood sampling. The patients were further divided into two groups according to the energy received, group 1 ( n = 8) with lower energy and group 2 ( n = 8) with higher energy. The postpacing arterial-coronary sinus lactate difference was significantly higher than that 1 min after ablation (0.18 ± 0.16 vs. −0.08 ± 0.14 mmol/l, P < 0.01). The mean arterial-coronary sinus lactate difference obtained at 3 min, 5 min and 10 min increased gradually and finally approximated the postpacing lactate difference. The arterial-coronary sinus lactate difference 1 min after ablation of group 2 was significantly lower than that of group 1 (−0.03 ± 0.14 vs. −0.13 ± 0.14 mmol/l, P < 0.01). The arterial coronary sinus lactate differences of group 2 obtained at 3 min, 5 min and 10 min were also lower than those of group 1. However, the difference between the two groups decreased with time. This finding suggests that radiofrequency energy has an influence on the myocardial metabolism and higher energy causes more metabolic alteration than lower energy.

Electrophysiologic significance of discrete slow potentials in dual atrioventricular node physiology: Implications for selective radiofrequency ablation of slow pathway conduction

Atrioventricular (AV) node reentrant tachycardia is now routinely cured by selective radiofrequency ablation of slow AV node pathway conduction. However, debate remains concerning the optimum method for localizing the site at which radiofrequency energy should be delivered to eliminate slow-pathway conduction. Some investigators have proposed simple anatomy-guided ablations posteriorly near the ostium of the coronary sinus, whereas others suggest an electrophysiology-guided ablation using either recorded “slow potentials” or mapping of the retrograde atrial exit site of slow AV node pathway conduction when possible. To examine these issues, we systematically studied slow potentials recorded in the AV junction of patients undergoing radiofrequency catheter ablation for medically refractory AV node reentrant tachycardia. In 67 patients with the slow-fast form of AV node reentrant tachycardia, we performed detailed atrial mapping along the tricuspid annulus within the triangle of Koch. Two types of slow potentials were identified. Low-amplitude, low-frequency potentials, found in 48% of patients, were localized to the mid to posterior portions of the triangle of Koch, whereas high-amplitude, high-frequency potentials, observed in 22% of patients, were located only posteriorly near the ostium of the coronary sinus. In response to a bolus infusion of adenosine or incremental atrial pacing-induced AV node Wenckebach periodicity, the low-amplitude, low-frequency potentials showed an increased duration and further reduction in amplitude and frequency and often totally disappeared. In contrast, in spite of these maneuvers, the high-amplitude and high-frequency potentials remained unchanged. Of the 25 (37%) of 67 patients in whom the earliest retrograde atrial activation during ventriculoatrial slow AV nodal pathway conduction could be recorded, no patient exhibited low-amplitude, low-frequency potentials, and only 7 (28%) of 25 of these patients showed high-amplitude, high-frequency potentials. High-amplitude, high-frequency potentials persisted after successful radiofrequency ablation of slow pathway conduction. Fewer applications of radiofrequency energy were required for successful elimination of slow pathway conduction in patients in whom the retrograde atrial exit site of slow-pathway conduction could be localized, compared with those patients who only exhibited retrograde fast AV nodal pathway conduction. We conclude that high-amplitude, high-frequency potentials are part of atrial activity, whereas the origin of low-amplitude, low-frequency potentials is unclear and may represent either true intranodal biophysical electrical activity or merely artifact or far-field potentials. Regardless, the recording of high-amplitude or low-amplitude potentials is not required for successful ablation of slow-pathway conduction, although the ability to localize the retrograde atrial exit of slow-pathway conduction may assist in the ablation procedure.

Comfort issues in patients undergoing radiofrequency catheter ablation

The introduction of RFCA of accessory pathways offers an invasive yet safe cure for the potentially lethal arrhythmias associated with reentrant SVT. This lengthy procedure challenges nurses in providing patient comfort. It cannot be overemphasized how much these seemingly simple comfort measures can humanize an otherwise frighteningly "high-tech" atmosphere. Physical comfort as well as psychological well being will be enhanced with "high-touch" care. As RFCA becomes more common, further research must be directed toward maximizing comfort and minimizing complications.

Effect of accessory pathway location on the efficiency of heating during radiofrequency catheter ablation

During radiofrequency catheter ablation of accessory pathways there is a poor correlation between applied power and temperature at target sites for catheter ablation. This study was designed to examine the relation between power and temperature during radiofrequency catheter ablation in patients with accessory pathways and to identify the factors that affect the efficiency of heating, defined as the ratio of applied power and temperature. Twenty-nine patients underwent radiofrequency catheter ablation of an accessory pathway. Among 257 energy applications, 108 were applied for ablation of a right-sided accessory pathway, 105 for a left-sided accessory pathway, and 44 for a posteroseptal accessory pathway. During each application of radiofrequency energy, temperature was continually monitored by use of an ablation catheter with a thermistor embedded in the tip of the distal electrode. During some applications of energy, fluctuations in temperature were observed. The average power, impedance, temperature, and efficiency of heating for all applications of radiofrequency energy was 37 ± 11 W, 100 ± 9 ohms, 53 ± 9° C, and 1.7 ± 0.8° C W (range 0.9° to 6.6° C W ), respectively. The efficiency of heating varied by location ( p < 0.0001), with the greatest efficiency of heating for posteroseptal energy applications (2.3 ± 1.2° C W , which were significantly greater than for left-sided (1.8 ± 0.8° C W ; p < 0.01) or right-sided (1.2 ± 0.4° C W ; p < 0.0001) applications. Phasic fluctuation in temperature was observed during 127 (49%) energy applications, and the efficiency of heating was 1.5 ± 0.7° C W . For the 130 applications with a stable temperature curve, the efficiency was 1.8 ± 0.9° C W ( p < 0.02). The mean impedance during energy applications correlated weakly with efficiency ( r = 0.2, p = 0.0012). In conclusion, the efficiency of heating varies according to the location of the application of radiofrequency energy. Inadequate contact, as manifested by fluctuating temperature during ablation, results in less efficient heating.

Analysis of body surface area as a determinant of impedance during radiofrequency catheter ablation in adults and children

Since most radiofrequency (RF) generators used for catheter ablation approximate a constant voltage output, applied power is inversely proportional to the impedance load of the system. Knowledge of the expected impedance load for a patient may facilitate selection of safer and more effective voltage output. Preliminary observations suggest that in adults, impedance is directly proportional to body surface area (BSA), thus prompting this study to determine whether this relation was maintained in smaller patients undergoing RF catheter ablation. Prospective analysis of impedance from 949 RF deliveries in 76 patients (BSA, 0.69–2.3 m 2) revealed the mean impedance for all deliveries to be 103 ± 8 ohms. Two-phase linear regression analysis revealed a significant, direct correlation between impedance and BSA in patients with a BSA ≥ 1.5 m 2 ( P = .001); however, for patients with a BSA < 1.5 m 2 there was no correlation. These results indicate that as patient size decreases below 1.5 m 2, impedance is constant. Radiofrequency catheter ablation procedures in children may require selection of a voltage output similar to that used in adults in order to produce effective RF lesions.

Design and clinical application of a low-pass input filter for the evaluation of intracardiac electrograms during radiofrequency catheter ablation

Successful ablation of an accessory pathway using radiofrequency current may be defined by the elimination of ventricular preexcitation or the loss of eccentric retrograde atrial activation. 1 Because of the low voltages of intracardiac electrograms (0.1 to 5.0 mV) compared with the high voltages applied during radiofrequency ablation (30 to 50 V), monitoring of local electrograms during ablation may not be feasible with conventional biopotential amplification and filtering systems 2. However, given the fundamental differences in signal frequencies between intracardiac electrograms (10 to 230 Hz) and radiofrequency current (550 to 750 KHz), selective attenuation of high-frequency radiofrequency signals and amplification of the lower frequency intracardiac electrograms may allow continuous monitoring of intracardiac electrograms during ablation. 3 The purpose of this study was to evaluate the feasibility and clinical use of an input bandpass filter, selective for frequencies < 1 KHz, which allowed continuous monitoring of intracardiac electrograms in patients undergoing radiofrequency catheter ablation of accessory pathways.

Safety, feasibility and cost of outpatient radiofrequency catheter ablation of accessory atrioventricular connections

Objectives. The purpose of this study was to evaluate prospectively the safety, feasibility and cost of performing radiofrequency catheter ablation of accessory atrioventricular (AV) connections on an outpatient basis in 137 cases.Background. The efficacy and low complication rate of radiofrequency ablation as performed in the hospital suggested that it might be feasible to perform it on an outpatient basis.Methods. In 100 cases (73%) performed between September 1, 1991 and April 20, 1992, patients met criteria for treatment as outpatients. Reasons for exclusion were age <13 or >70 years (4), anteroseptal location of the accessory AV connection (5 patients), obesity (>30% of ideal body weight) (4 patients) or clinical indication for hospitalization (24 patients). Patients with only venous punctures had a recovery period of 3 h and those with arterial punctures had a recovery period of 6 h. There were 63 men and 32 women (5 patients underwent two ablation procedures >1 month apart), with a mean age ± SD of 36 ± 13 years. The pathway was left-sided in 67 cases and right-sided or posteroseptal in 33.Results. The procedure was successful in 97 of 100 cases, with a mean procedure duration of 99 ± 42 min. In 70 cases the patient was discharged the day of ablation, and in 30 cases the patient required a short (≤18-h) overnight stay because the procedure was completed too late in the day for recovery in the outpatient facility. The mean duration of observation was 4.8 ± 1.5 h for outpatients and 15 ± 1.4 h for patients who underwent overnight hospitalization. At follow-up study, two patients had a clinically significant complication; both had a femoral artery pseudoaneurysm detected ≥1 week after the procedure and both required surgical repair. Thirty consecutive patients (22 outpatients and 8 hospitalized overnight) undergoing catheter ablation after January 1, 1992 were chosen for a cost analysis. The mean cost of the procedure was $10,183 ± $1,082.Conclusions. The majority of patients undergoing radiofrequency catheter ablation of an accessory AV connection can be treated safely on an outpatient basis.

Impedance monitoring during radiofrequency catheter ablation in humans.

Radiofrequency catheter ablation of accessory pathways and the atrioventricular junction often requires multiple applications of energy. The inability to determine the effects of any given application on the underlying tissue may contribute to this problem. In the present study, impedance was monitored in 20 patients undergoing radiofrequency catheter ablation, and the relationship between an initial decrease in impedance and subsequent effects were examined. An initial fall in impedance of more than 10 omega was 78% sensitive and 88% specific for predicting subsequent evidence of tissue heating (interruption of conduction or an abrupt rise in impedance due to coagulum formation). In contrast, initial values of voltage, current, or impedance did not distinguish between effective and ineffective applications of radiofrequency energy. Continuous monitoring of impedance may facilitate radiofrequency catheter ablation.