Usefulness of remote magnetic navigation for ablation of ventricular arrhythmias originating from outflow regions.

Monomorphic ventricular tachycardia (VT) and symptomatic monomorphic PVCs originating from the region of the right and left outflow tracts are increasingly treated by radiofrequency (RF) catheter ablation. Technical difficulties in catheter manipulation to access these outflow tract areas, very accurate mapping and reliable catheter stability are key issues for a successful treatment in this vulnerable region. VT ablation from the aortic sinus cusp (ASC) in particular carries a significant risk of perforation, of creating left coronary artery injury and of damage to the aorta and the aortic valve.This case series describes RF ablation of VT originating in the outflow region using the remote magnetic navigation system (MNS). Potential advantages of the MNS are catheter flexibility, steering accuracy and reproducibility to navigate to a desired location with a low probability of perforating the myocardium. This report supports the idea of using advanced MNS technology during RF ablation in regions which are difficult to reach and thin walled, such as parts of the outflow tract and the ASC. (Neth Heart J 2009;17:245-9.).

Baffle puncture guided by transoesophageal echocardiography in a patient with dextrocardia and Mustard correction.

A baffle puncture is a challenging procedure but can be safely done using direct visualization of the region of interest. To our knowledge, however, it has never been performed in a patient with dextrocardia. We present a 62-year-old male with dextrocardia, right isomerism, congenitally corrected transposition of the great arteries, persistent left-sided superior and inferior caval veins, atrial septum defect, and pulmonary valve stenosis. The atrial septum defect was surgically closed with a Teflon patch, a variant Mustard operation was performed, and also a prosthetic tricuspid valve was implanted. The patient developed multiple episodes of atrial tachycardia leading to acute heart failure on many occasions. An electrophysiological study was undertaken in order to create a bi-atrial electro-anatomical map. Owing to the presence of a prosthetic tricuspid valve, the femoral venous access was used and a baffle puncture was performed using continuous monitoring with fluoroscopy and transoesophageal echocardiography (TEE). The baffle puncture was successful and the tachycardia was ablated in the systemic venous atrium. To our knowledge, we present the very first case report demonstrating a successful baffle puncture in a patient with dextrocardia and Mustard correction. Direct imaging using TEE seems to be a very useful tool for guiding the puncture.

Acute success and short-term follow-up of catheter ablation of isthmus-dependent atrial flutter; a comparison of 8 mm tip radiofrequency and cryothermy catheters.

OBJECTIVES: To compare the acute success and short-term follow-up of ablation of atrial flutter using 8 mm tip radiofrequency (RF) and cryocatheters. METHODS: Sixty-two patients with atrial flutter were randomized to RF or cryocatheter (cryo) ablation. Right atrial angiography was performed to assess the isthmus. End point was bidirectional isthmus block on multiple criteria. A pain score was used and the analgesics were recorded. Patients were followed for at least 3 months. RESULTS: The acute success rate for RF was 83% vs 69% for cryo (NS). Procedure times were similar (mean 144+/-48 min for RF, vs 158+/-49 min for cryo). More applications were given with RF than with cryo (26+/-17 vs. 18+/-10, p<0.05). Fluoroscopy time was longer with RF (29+/-15 vs. 19+/-12 min, p<0.02). Peak CK, CK-MB and CK-MB mass were higher, also after 24 h in the cryo group. Troponin T did not differ. Repeated transient block during application (usually with cryoablation) seemed to predict failure. Cryothermy required significantly less analgesia (p<0.01), and no use of long sheaths (p<0.005). The isthmus tended to be longer in the failed procedures (p=0.117). This was similar for both groups, as was the distribution of anatomic variations. Recurrences and complaints in the successful patients were similar for both groups, with a very low recurrence of atrial flutter after initial success. CONCLUSIONS: In this randomized study there was no statistical difference but a trend to less favorable outcome with 8 mm tip cryocatheters compared to RF catheters for atrial flutter ablation. Cryoablation was associated with less discomfort, fewer applications, shorter fluoroscopy times and similar procedure times. The recurrence rate was very low. Cryotherapy can be considered for atrial flutter ablation under certain circumstances especially when it has been used previously in the same patient, such as in an AF ablation.

Sarcoidosis mimicking ischaemic ventricular arrhythmia and pulmonary embolism.

Sarcoidosis is a multisystem granulomatous disorder characterised pathologically by the presence of noncaseating granulomas in the organs involved. Cardiac involvement, although well known, is rare. We describe a 72-year-old patient who was admitted to the intensive care unit after coronary artery bypass grafting. She developed refractory right and left ventricular failure complicated by multiple organ failure and died three days later. Postmortem examination revealed extensive sarcoidosis. On hindsight, preoperative ventricular tachycardia and an abnormal perfusion-ventilation scintigraphy of the lungs were manifestations of an underlying sarcoidosis.

Ten year follow-up after radiofrequency catheter ablation for atrioventricular nodal reentrant tachycardia in the early days forever cured, or a source for new arrhythmias?

BACKGROUND: Radiofrequency (RF) catheter ablation is highly effective with a low complication rate. However, lesions created by RF energy are irreversible, inhomogeneous, and therefore potentially proarrhythmic. OBJECTIVES: The aim of this study was to examine the magnitude and importance of long-term proarrhythmic effects of RF energy. METHODS AND RESULTS: Between 1991 and 1995, 120 patients underwent RF ablation for atrioventricular nodal reentrant tachycardia (AVNRT). Patient data were collected by contacting patients and/or filling out a questionnaire, and medical files were screened for recurrent, documented arrhythmias, pharmacological treatment, and repeated EP study. Referring cardiologists were asked about recurrences of tachyarrhythmias. Fourteen patients (11%) were lost to follow-up. During a mean follow-up of 10 years, six patients died. Recurrences of AVNRT were not any more observed after 3 years after ablation. A total of 29 patients (24%) suffered from new arrhythmias, 6 from type 1 atrial flutter, 6 from atrial tachycardia, 9 from atrial fibrillation, and finally 16 from symptomatic premature atrial contractions (PACs), needing medical treatment or a combination of these arrhythmias. Nine patients underwent pacemaker implantation, 4 after developing procedural atrioventricular (AV) conduction disturbances, 2 after His ablation for permanent atrial fibrillation, 1 patient for sick sinus syndrome, and another 2 patients after developing late AV block, respectively, 7 and 9 years after ablation. CONCLUSION: During long-term follow-up after RF ablation for AVNRT, no AVNRT recurrences were observed, but 29 patients (24%) suffered from new arrhythmias or late AV block. This potential proarrhythmic effect of RF energy promotes the application of alternative energy sources for ablative therapies for cardiac arrhythmias.

A randomized study of combining maze surgery for atrial fibrillation with mitral valve surgery.

AIM: Mitral valve surgery seldom suppresses atrial fibrillation (AF), present prior to surgery. Maze III surgery eliminates AF in >80% of cases, the reason why combining this procedure with mitral valve surgery in patients with AF seems worthwhile. We prospectively studied the outcome of combining the Maze III procedure with mitral valve surgery. METHODS: Thirty-five patients with AF and a mean age of 64 years undergoing mitral valve surgery were prospectively randomized according to a 2.5:1 ratio to surgery with (n=25), or without (n=10) maze III and followed for at least 1 year. RESULTS: At discharge and after 12 months freedom from AF was 56% and 92%, respectively, in the maze group, and 0% and 20%, respectively, in patients without maze (group differences at discharge p=0.002, after 12 months p=0.0007). Sinus node incompetence was seen in 1 of 25 maze patients requiring pacing. No in-hospital or late death occurred; stroke was observed in 1 patient (without maze). Quality of life markedly improved after surgery, but did not differ between patients with or without maze surgery. CONCLUSIONS: This first prospective randomized study shows that combining maze III with mitral valve surgery resulted in a significantly better elimination of preoperative AF than mitral valve surgery alone. As the quality of life did not differ between patients with, or without maze surgery, additional maze surgery is primarily recommended in patients in whom anticoagulation therapy can be avoided after surgery, specifically in patients with scheduled mitral valve plasty.

Right atrial modification of maze surgery does not affect refractoriness and conduction patterns of human lone atrial fibrillation.

BACKGROUND: Tissue mass and structure are relevant for initiation and persistence of fibrillation. Modification of the right atrium during maze surgery may change the arrhythmogenic substrate of atrial fibrillation (AF). METHODS AND RESULTS: Epicardial mapping was performed in 9 patients undergoing unmodified maze III surgery for lone paroxysmal AF. Simultaneous recording of AF on the right and left atrium was carried out with two spoon-electrodes each harbouring 64 terminals. Activation maps of AF were made to study AF wavelet organization. The recording position on right and left atria was outside the surgical field and remained unchanged before and after surgery. Before surgery, mean right and left fibrillatory intervals were 174+/-23 ms, and 175+/-26 ms, respectively, and did not differ. After completed right atrial surgery, these fibrillary intervals remained unchanged. Mean right and left atrial dispersion of refractoriness (expressed as the coefficient of variation) were 4.2+/-0.8 and 5.2+/-3.8 ms. Only right atrial dispersion of refractoriness increased significantly after right-sided surgery. Prior to surgery, activation patterns of the left atrium were more complex than that of the right atrium. The left activation patterns became less complex afterwards; the right atrial activation patterns did not change. CONCLUSION: The right atrial modification of maze III surgery neither affects atrial refractoriness during human lone AF nor changes AF wavelet organization. Thus, right atrial surgery does not modify the arrhythmogenic substrate of AF. These findings may imply that maze surgery can be restricted to the left atrium.

Fast and slow narrow complex tachycardia in one patient: two of a kind?

A 35-year-old female was referred to our hospital. For more than ten years, she had had complaints of two types of paroxysmal palpitations, both with a sudden onset. The first type was rapid and often accompanied by light-headedness; the second she described as much less rapid, better tolerated, and often terminated by the Valsalva manoeuvre. The incidence and duration of both types of paroxysms were increasing. In the emergency room of the referring hospital, the tachycardia was terminated with intravenous verapamil. The electrophysiological study revealed normal conduction parameters. Premature atrial beats (due to catheter manipulation) or delivered atrial extra stimuli over a wide range easily induced two types of tachycardia. AV node modification by radiofrequency ablation using the posterior approach was performed. With this approach, RF ablation of the caudal extension of the AV node is performed, which modifies the slow pathway, so that the reentrant circuit is interrupted. After this intervention, no tachycardia whatsoever could be induced and during followup (8 months), no recurrent arrhythmia of any kind occurred.

Successful surgical ablation of sustained ventricular tachycardia associated with mitral valve prolapse guided by a multielectrode basket catheter.

Ventricular tachycardia occurs frequently in patients with mitral valve prolapse. If antiarrhythmic drug therapy fails or mitral valve surgery is indicated, concomitant arrhythmia surgery may be considered. This report describes the first clinical use of an atrial transseptally inserted multielectrode basket catheter, placed across the mitral valve, to guide intraoperative mapping and ablation of monomorphic sustained ventricular tachycardia in association with mitral valve prolapse. Endocardial covering and signal quality of this percutaneous mapping catheter were of good quality, allowing an accurate localization of the site of origin of the tachycardia.

Pace mapping of postinfarction scar to detect ventricular tachycardia exit sites and zones of slow conduction.

INTRODUCTION: The exit site and central common pathway of slow conduction are preferred sites to guide radiofrequency ablation of postinfarction ventricular tachycardia (VT). Both require inducibility of VT. In addition, their low amplitude hampers direct recording of potentials generated by activation in pathways of slow conduction. We hypothesized that pace mapping during sinus rhythm would help to detect the VT exit site and potentials generated by activation in pathways of slow activation. METHODS AND RESULTS: In 13 patients suffering from VT late after anterior (n = 10) or inferior (n = 3) myocardial infarction, stimulation was performed in scarred endocardium at 23.5 (range 13 to 36) sites per patient during arrhythmia surgery. Multielectrode recordings (64 sites) during stimulation at a fixed cycle length of 500 msec were obtained. Endocardial breakthrough sites distant (>2 cm) from the pacing site were found at 4.3 (range 3 to 19) pacing sites per patient. Low-amplitude discrete potentials (LADPs) could be detected between the pacing site and the breakthrough site in 2.3 (range 0 to 13) of 4.3 stimulation sequences. In these patients, 19 VTs were induced and the exit site determined. In 6 patients, the distant pacing breakthrough site was identical to the VT exit site; in 7 patients, no similar exit sites were found. LADPs during VT were found at a median 2.0 (range 0 to 14) sites per patient. CONCLUSION: Pace mapping of the postinfarction endocardial scar during sinus rhythm revealed 50% of the endocardial exit sites of VT and the same number of LADPs observed during VT.

Brugada syndrome: a case report of monomorphic ventricular tachycardia.

A 56-year-old woman without structural heart disease had an ECG typical of Brugada syndrome. Syncope occurred due to monomorphic VT with left bundle branch block (LBBB) morphology. At electrophysiological study, VT with the same morphology was inducible.

Relation between body surface mapping and endocardial spread of ventricular activation in postinfarction heart.

INTRODUCTION: Body surface mapping (BSM) can be used to identify the site of earliest endocardial activation of ventricular tachycardias (VTs). The multielectrode QRS morphology during VT is determined by both the site of earliest activation and the subsequent spread of electrical activation through the ventricles. This study investigated the relationship between the site of earliest endocardial activation, endocardial spread of activation, and the morphology of the multielectrode surface map in patients with remote myocardial infarction. METHODS AND RESULTS: In 14 patients with VT late (8.2+/-5.2 years) after myocardial infarction, BSM and simultaneous left ventricular 64-site basket endocardial mapping was performed during a total of 17 monomorphic VTs. In addition, multisite pacing by sequential use of the 64 basket electrodes was performed in 9 patients. BSM and basket mapping revealed the same endocardial breakthrough sites in 8 (47%) of 17 VTs and 189 (59%) of 322 pacing sites; adjacent sites were found in 2 (12%) of 17 VTs and 36 (11%) of 322 pacing sites. Large zones of conduction block explained the mismatch in localization in 2 (12%) of 17 VTs and 52 (16%) of 322 pacing sites. Regional differences in endocardial electrogram amplitudes were found as a cause for dissimilarity in 3 (18%) of 17 VTs and 73 (23%) of 322 pacing sites. Multiple endocardial breakthrough sites were found in 1 (6%) of 17 VTs and 8 (2%) of 322 pacing sites Finally, an epicardial exit site was suggested in 3 (18%) of 17 VTs as an explanation for mismatch, as no early endocardial activity could be recorded. CONCLUSION: Zones of conduction block, regional differences in signal amplitude, and multiple endocardial breakthrough sites are frequent causes for mismatch between BSM and basket catheter activation mapping.

Mitral valve surgery and atrial fibrillation: is atrial fibrillation surgery also needed?

OBJECTIVE: Atrial fibrillation (AF) persisting after mitral valve surgery reduces survival due to heart failure and thrombo-embolisms, and impairs quality of life. Arrhythmia surgery for AF shows today very satisfying results and therefore mitral valve surgery with AF surgery appears appealing. This study explores whether combined surgery in view of today's results of mitral valve surgery is indicated. METHODS AND RESULTS: An outcome analysis of the arrhythmia outcome of patients undergoing exclusive mitral valve surgery with or without tricuspid repair was done. Preoperative baseline characteristics including arrhythmia pattern, surgical methods and follow-up findings were reviewed. Postoperative management of AF was not protocolized. Between 1990 and 1993, 162 consecutive patients underwent mitral valve surgery; follow-up was a mean of 3.3+/-1.9 years. In-hospital and late mortality were 1 and 9%, respectively. Sinus rhythm was preserved in 40 of 57 (70%) patients with preoperative sinus rhythm whereas AF persisted in 58 of 68 (85%) of patients with preoperative chronic AF (>1 year present). Sinus rhythm without AF was observed in 10 of 29 (34%) patients with preoperative paroxysmal AF. The 4-year Kaplan-Meier survival did not differ between patients with preoperative sinus rhythm (95.2%), paroxysmal AF (89.2%) and chronic AF (82.9%) but AF persisting after surgery tended to determine survival (P=0.05). Gender, age and right ventricular pressure and tricuspid valve repair were risk factors for postoperative recurrence of AF in patients with sinus rhythm at discharge, relative risk 0.35, 1.06, 1. 04 and 2.9, respectively. CONCLUSION: Current mitral valve surgery with or without tricuspid valve repair does not eliminate preoperative paroxysmal or chronic AF. Secondly, because preoperative AF did not determine survival after mitral valve surgery, whereas postoperatively persisting AF was weakly associated with survival, atrial arrhythmia surgery primarily aims to reduce morbidity due to AF. Some characteristics can identify patients with increased propensity for persisting AF after surgery. Randomized studies of AF surgery are needed to identify suitable candidates for combined surgery.

Successful results of a bipolar active fixation lead for atrial application: an interim analysis.

Adequate atrial lead performance consists of stable sensing and pacing properties. To evaluate whether the CPI 4269 bipolar lead, covered with mannitol (Sweet Tip), in the atrial position encounters these properties, we performed a prospective study of this lead. After complete dissolution of the mannitol helix, mapping of the atrium to obtain the highest electrogram and lowest threshold was followed by screw-in into the endocardium. Intraoperative measurements were performed and long-term follow-up was scheduled every 6 to 12 months to measure threshold and perform an intracardial electrogram. Between February 1993 and December 1996, a total number of 73 leads in the atrial position in a consecutive series of patients was implanted. Implantation was performed in 28 patients receiving an AAIR and 45 patients a DDDR pacemaker. Reason for pacemaker implantation was a third-degree AV block in 37% of patients, type II second-degree AV block in 25%, sick sinus syndrome in 35%, and drug refractory paroxysmal atrial fibrillation following His-bundle ablation in 3%. The intraoperative bipolar atrial electrogram had a mean voltage of 4.25 +/- 2.1 mV. The acute atrial bipolar threshold was 0.63 +/- 0.43 V, and current was 1.35 +/- 0.81 mA at a 1.0-ms pulse duration. The mean acute resistance of the lead was 572 +/- 86 Ohm. After a mean follow-up of 18.3 months, the bipolar intracardial electrogram was 3.37 +/- 2.00 mV, the mean atrial threshold measured at the last outpatient clinic visit was 0.99 +/- 0.74 V and the mean impedance was 640 +/- 127 Ohm. A sensing problem due to traction of the atrial lead occurred in only one patient. Acute and late dislodgement did not occur. The CPI 4269 (Sweet Tip) lead is manufactured with a dissolvable capsule covering the helix tip electrode, permitting a safe passage through the venous system. This interim analysis shows that this lead in the atrial position has favorable acute and chronic results.

Results of maze surgery for lone paroxysmal atrial fibrillation.

BACKGROUND: If drug refractoriness to paroxysmal atrial fibrillation (PAF) occurs, arrhythmia surgery that involves channelling and the exclusion of specific atrial areas can abolish atrial fibrillation. The purpose of this study was to establish the effectiveness and safety of maze III surgery to abolish PAF. METHODS AND RESULTS: Surgery was performed in 41 selected patients who had long-standing, symptomatic, drug-refractory, lone PAF. At discharge, 35 patients (85%) were arrhythmia free, and 6 patients (15%) showed PAF and paroxysmal atrial tachycardia. Death or stroke did not occur during a mean follow-up of 31+/-16 months. At the end of follow-up, 39 patients (95%) had no PAF; however, in 2 patients (5%), PAF persisted and eventually required His bundle ablation and pacing. Three months after surgery, nodal escape rhythm was observed in only 1 patient, whereas sick-sinus syndrome emerged late after surgery in 2 patients. Antiarrhythmic drugs were used in 20% of patients during follow-up. The quality of life improved markedly after surgery and remained unchanged afterward. Echocardiographic findings did not alter, but exercise capacity increased. CONCLUSIONS: This pilot study demonstrates the effectiveness and safety of maze III surgery for lone PAF. In patients without sick-sinus syndrome, this intervention offers a sensible alternative to His bundle ablation and lifelong pacemaker dependency.

Temporary pacing after His bundle ablation for drug-refractory atrial fibrillation: a risky enterprise?

AIM: In patients with and without a permanent pacemaker His bundle ablation was performed for symptomatic drug-refractory atrial fibrillation. This study was performed to examine the complications of temporary pacing in patients without an already implanted pacemaker. METHODS AND RESULTS: Between January 1996 and December 1998, 152 consecutive patients, both referred and our own (non-referred), underwent His bundle ablation for drug-refractory atrial fibrillation. Primary end-point complications were temporary lead dislodgement requiring immediate repositioning (1), severe arrhythmia (2), death (3) and persistent damage to an already implanted pacing system (4). Secondary end-points were malsensing and malpacing of the temporary lead, and blood vessel problems. Lead dislodgement of the temporary pacemaker occurred in three patients (2.9%), all of whom were in the referred group. Severe arrhythmia and death did not occur. Persistent damage of the already implanted pacing system was not observed. Secondary end-points occurred in 15.8%) of the patients and were successfully managed by a conservative approach. CONCLUSION: Permanent pacemaker implantation is recommended prior to His bundle ablation in order to avoid haemodynamic deterioration due to dislocation of the temporary pacemaker lead. RF current used for His bundle ablation caused no permanent damage to permanent pacing systems.

Comparison of late results of surgical or radiofrequency catheter modification of the atrioventricular node for atrioventricular nodal reentrant tachycardia.

AIMS: Although arrhythmia surgery and radiofrequency catheter ablation to cure atrioventricular nodal reentrant tachycardia differ in technical concept, the late results of both methods, in terms of elimination of the arrhythmogenic substrate and procedure-related new and different arrhythmias, have never been compared. This constituted the purpose of this prospective follow-up study. METHODS AND RESULTS: Between 1988 and 1992, 26 patients were surgically treated using perinodal dissection or 'skeletonization', and from 1991 up to 1995, 120 patients underwent radiofrequency modification of the atrioventricular node for atrioventricular nodal reentrant tachycardia. The acute success rates of surgery and radiofrequency catheter ablation were 96% and 92%, respectively. Late recurrence, rate in the surgical and radiofrequency catheter ablation groups was 12% and 17%, respectively. Mean follow-up was 53 months in the surgical group and 28 months in the radiofrequency catheter ablation group. The final success rate after repeat intervention was 100% in the surgical group and 98% in the radiofrequency catheter ablation group. Comparison of the initial and recent series of radiofrequency catheter ablated patients showed an increased initial success rate with fewer applications. In the radiofrequency catheter ablation group, a second- or third-degree block developed in three patients (2%), requiring permanent pacing, whereas in the surgical group no complete atrioventricular block was observed. Inappropriate sinus tachycardia needing drug treatment was observed in 13 patients (11%), mostly after fast pathway ablation, but was never observed after surgery. New and different supraventricular tachyarrhythmias arose in 27% of the patients in the surgical group and in 11% of the radiofrequency catheter ablation group, but did not clearly differ. CONCLUSION: This one-institutional follow-up study demonstrated comparable initial and late success rates as well as incidence of new and different supraventricular arrhythmias following arrhythmia surgery and radiofrequency catheter ablation for atrioventricular nodal reentrant tachycardia. Today radiofrequency catheter ablation has replaced arrhythmia surgery for various reasons, but the late arrhythmic side-effects warrant refinement of technique.

VDDR pacing after His-bundle ablation for paroxysmal atrial fibrillation: a pilot study.

His-bundle ablation followed by pacemaker implantation is today a widely accepted therapeutic choice when drug refractoriness of symptomatic AF is evident. The selection of pacing mode in patients suffering from paroxysmal AF is still controversial. Preservation of AV synchrony is an attractive option in patients with paroxysmal AF who undergo His-bundle ablation. The purpose of this study was to examine prospectively the contribution of VDDR pacing for preservation of AV synchrony. After His-bundle ablation a VDDR pacing system was implanted in 17 patients with paroxysmal AF, and all antiarrhythmic drugs were withdrawn. The endpoint of the study was defined as the onset of chronic AF. To document the onset of chronic AF 48-hour Holter recordings were made every 6-8 weeks. After a mean followup of 18.2 (range 14-21) months, VDDR pacing is still operative in 13 patients (77%). Four patients developed chronic AF after a mean follow-up of 6 months. Of several baseline characteristics, only the intraatrial P wave at implantation was significantly smaller in patients developing chronic AF than in patients in whom the VDDR mode is still operative. This pilot study suggests that VDDR pacing is an attractive pacing method for patients with paroxysmal AF after His-bundle ablation. A low intraatrial P wave electrogram at implant was associated with a higher risk for the development of chronic AF.

Body surface mapping during pacing at multiple sites in the human atrium: P-wave morphology of ectopic right atrial activation.

BACKGROUND: The morphology and polarity of the P wave on 12-lead ECG are of limited clinical value in localizing ectopic atrial rhythms. It was the aim of this study to assess the spatial resolution of body surface P-wave integral mapping in identifying the site of origin of ectopic right atrial (RA) impulse formation in patients without structural atrial disease. METHODS AND RESULTS: Sixty-two-lead ECG recordings were obtained during RA pacing at 86 distinct endocardial sites in nine patients with normal biatrial anatomy. After P-wave integral maps were generated for each paced activation sequence, 17 groups with nearly identical map features were visually selected, and a mean P-wave integral map was computed for each group. Supportive statistical analysis to corroborate qualitative group selection was performed by assessment of (1) intragroup pattern uniformity by use of jackknife correlation coefficient analysis of the integral maps contained in each group and (2) intergroup pattern variability by use of the calculation of cross correlations between the 17 mean integral maps. The spatial resolution of paced P-wave body surface mapping in the right atrium was obtained by estimating the area size of endocardial segments with nearly identical P-wave integral maps by use of a biplane fluoroscopic method to compute the three-dimensional position of each pacing site. The latter approach yielded a mean endocardial segment size of 3.5+/-2.9 cm2 (range, 0.79 to 10.75 cm2). CONCLUSIONS: Use of the P-wave morphology on the 62-lead surface ECG in patients with normal biatrial anatomy allows separation of the origin of ectopic RA impulse formation into one of 17 different endocardial segments with an approximated area size of 3.5 cm2. This database of paced P-wave integral maps provides a versatile clinical tool to perform detailed noninvasive localization of right-sided atrial tachycardia before radiofrequency catheter ablation.