Localization of Left Free-Wall and Posteroseptal Accessory Atrioventricular Pathways by Direct Recording of Accessory Pathway Activation

With the advent of catheter ablation techniques, precise localization of accessory AV pathways (AP) assumes greater importance. In an efort to define the course of AP fibers, we attempted to record activation of 56 left free-wall and 23 posteroseptal APs in 62 patients undergoing eiectrophysiological study. The coronary sinus (CS) and great cardiac vein (GCV) were mapped using orthogonal catheter electrodes, which provide a recording dipole perpendicular to the AV groove. The tricuspid annulus (TA) was mapped using a 2 mm spaced octapolar electrode catheter. Potentials were considered to represent AP activation only if they could be dissociated from both atrial and ventricular activation by programmed stimulation. Orthogonal catheter electrodes in the CS and GCV were advanced heyond the site of earliest retrograde atrial activation and/or earliest antegrade ventricular activation in 45 of the 56 left free-wall APs, and AP potentials were recorded from 42 (93%). An oblique course was identified in 36 APs, with the ventricular insertion being recorded 4–30 mm (median 15 mm) distal or anterior to the atrial insertion. In three patients, antegrade and retrograde conduction proceeded over different (but close) parallel fibers. AP potentials were recorded from 19 of 23 posteroseptal pathways. Ten pathways (left posteroseptal) were recorded from the CS, beginning 5–11 mm (median 9 mm) distal to the os, with potentials extending 8–18 mm (median 11 mm) distally. Four pathways (midseptal) were recorded along the TA, anterior to the CS ostium and posterior to the His bundle catheter. Five pathways (right posteroseptal) were recorded along the TA, directly opposite or immediately posterior to the CS ostium. One of the patients had both midseptal and left posteroseptal pathways and three patients had both right posteroseptal and left posteroseptal pathways. We conclude: 1) left free-wall APs transit the AV groove obliquely and may be comprised of multiple, closely spaced, parallel fihers; 2) the anatomical location of “posteroseptal” pathways is variable and the presence of fibers at multiple sites is common; and 3) direct recordings of AP activation facilitate tracking of the accessory pathway along its course from atrium to ventricle and help identify the presence of multiple fibers.     

Radiofrequency Ablation of Left-Sided Accessory Atrioventricular Pathways in Patients with Unusual Coronary Sinus

Four patients with left-sided accessory pathways (APs)and unusual coronary sinus (CS)received radiofrequency ablation. Unusual CS included occlusion of CS (patient 1), acute anguJation of proximal CS (patients 2 and 3), and narrowing of CS orifice and proximal segment (patient 4). CS catheterization and AP mapping along the CS could not be performed in the four patients. Radiofrequency ablation by left ventricular retrograde technique for the manifest left posteroseptal AP (patient 1), concealed left posterior AP (patient 2), and transseptai left atrial technique for the manifest left posteroseptal AP (patient 3)and manifest left posterior AP (patient 4)were performed successfully without CS catheter guidance. This study suggests that radiofrequency ablation of left-sided AP with unusual CS is feasible by some special techniques.     

A Technique for Rapid Transfemoral Catheterization of the Coronary Sinus with Multielectrode Catheters

To minimize procedural and fluoroscopic times and avoid the risks of vascular injury and pneumothorax, some investigators have advocated elimination of routine placement of a coronary sinus (CS) catheter during electrophysiological procedures. We hypothesized that expedient and reproducible CS catheterization could be performed with minimal patient risk by utilizing a femoral vein approach. Fifty consecutive patients referred for radiofrequency ablative procedures underwent attempted CS catheterization using a 6-French steerable, quadripolar catheter via a femoral vein. Procedures were performed utilizing single-plane fluoroscopy without contrast angiographic aid by operators experienced in the technique. Successful catheterization was defined by the attainment, in < 15 minutes, of a stable catheter position with the distal electrode at or beyond the lateral margin of the heart. Successful catheterization of the CS was achieved in 47 (94%) patients. Selective pacing of the left atrium without patient discomfort was possible in all, eliminating the need for a right atrial pacing catheter. The median time to successful catheterization was 1.4 minutes (range 0.3–14.7). Only six patients required > 5 minutes. The median fluoroscopic time required was 1.2 minutes (range 0.3–12.7). No clinical variable was predictive of catheterization failure or time to successful catheterization. No complications were observed as a result of this technique. This prospective evaluation demonstrates that catheterization of the CS via a femoral vein approach is highly successful, expedient, and safe. The ability to selectively pace the left atrium may eliminate the requirement for a right atrial catheter.     

Mapping the Coronary Sinus and Great Cardiac Vein

GIUDICI, M., et al. : Mapping the Coronary Sinus and Great Cardiac Vein. The purpose of this study was to develop a better understanding of the pacing and sensing characteristics of electrodes placed in the proximal cardiac veins. A detailed mapping of the coronary sinus (CS) and great cardiac vein (GCV) was done on 25 patients with normal sinus rhythm using a deflectable electrophysiological catheter. Intrinsic bipolar electrograms and atrial and ventricular pacing voltage thresholds were measured. For measurement purposes, the GCV and the CS were each subdivided into distal (D), middle (M), and proximal (P) regions, for a total of six test locations. Within the CS and GCV, the average atrial pacing threshold was always lower (  P < 0.05  ) than the ventricle with an average ventricular to atrial ratio > 5, except for the GCV-D. The average atrial threshold in the CS and GCV ranged from 0.2– to 1.0-V higher than in the atrial appendage. Diaphragmatic pacing was observed in three patients. Atrial signal amplitude was greatest in the CS-M, CS-D, and GCV-P and smaller in the CS-P, GCV-M, and GCV-D. Electrode spacing did not significantly affect P wave amplitude, while narrower electrode spacing attenuated R wave amplitude. The average P:R ratio was highest with 5-mm-spaced electrodes compared to wider spaced pairs. The P:R ratio in the CS was higher (P < 0.05) than in all positions of the GVC. It is possible to pace the atrium independent of the ventricle at reasonably low thresholds and to detect atrial depolarization without undue cross-talk or noise using closely spaced bipolar electrode pairs. The areas of the proximal, middle, and distal CS produced the best combination of pacing and sensing parameters.     

Fulguration for AV Nodal Tachycardia: Results in 42 Patients with a Mean Follow-Up of 23 Months

HAISAGUERRE, M., ET AL.: Fulguration for AV Nodal Tachycardia: Results in 42 Patients with a Mean Follow-Up of 23 Months. This report describes a catheter ablation technique to treat atrioventricular nodal reentrant tachycardia while preserving anterograde conduction, and its application in 42 patients with drug-refractory repetitive episodes of tachycardia. One of these patients had common and reverse forms of tachycardia. Using atrial activation in the His-bundle lead as a reference, the optimal ablation site was selected by positioning an electrode catheter to obtain a synchronous or earlier atrial activation than the reference during tachycardia. At this site, His-bundle deflection was completely absent, or was present at a low amplitude (< 0.1 mV). In the majority of patients, these criteria were found in the immediate vicinity of the site of proximal His-bundle recording (adjacent to the reference catheter). Shocks of 160 or 240 joules (J) were delivered at this site (mean ± SD = 518 ± 392 J/session) with a resulting preferential abolition of impairment of fast retrograde conduction. Anterograde conduction, though modified, was preserved in all patients, except for four (10%) patients who remained in complete heart block. Thirty patients (70%) remained free of arrhythmia without medication or pacemaker for a mean follow-up period of 23 ± 13 (2–63) months. Six other patients (15%) were controlled with a previously ineffective medication.     

Electrophysiologic characteristics and radiofrequency catheter ablation in children with Wolff-Parkinson-White syndrome

BACKGROUND: The majority of cardiac arrhythmias in children are supraventricular tachycardia, which is mainly related to an accessory pathway (AP)-mediated reentry mechanism. The investigation for Wolff-Parkinson-White (WPW) syndrome in adults is numerous, but there is only limited information for children. This study was designed to evaluate the specific electrophysiologic characteristics and the outcome of radiofrequency (RF) catheter ablation in children with WPW syndrome. METHODS: From December 1989 to August 2005, a total of 142 children and 1,219 adults with atrioventricular reentrant tachycardia (AVRT) who underwent ablation at our institution were included. We compared the clinical and electrophysiologic characteristics between children and adults with WPW syndrome. RESULTS: The incidence of intermittent WPW syndrome was higher in children (7% vs 3%, P=0.025). There was a higher occurrence of rapid atrial pacing needed to induce tachycardia in children (67% vs 53%, P=0.02). However, atrial fibrillation (AF) occurred more commonly in adult patients (28% vs 16%, P=0.003). The pediatric patients had a higher incidence of multiple pathways (5% vs 1%, P<0.001).Both the onset and duration of symptoms were significantly shorter in the pediatric patients. The antegrade 1:1 AP conduction pacing cycle length (CL) and antegrade AP effective refractory period (ERP) in children were much shorter than those in adults with manifest WPW syndrome. Furthermore, the retrograde 1:1 AP conduction pacing CL and retrograde AP ERP in children were also shorter than those in adults. The antegrade 1:1 atrioventricular (AV) node conduction pacing CL, AV nodal ERP, and the CL of the tachycardia were all shorter in the pediatric patients. CONCLUSION: This study demonstrated the difference in the electrophysiologic characteristics of APs and the AV node between pediatric and adult patients. RF catheter ablation was a safe and effective method to manage children with WPW syndrome.     

Pacemaker-mediated Tachycardias: A New Modality of Treatment

Three Patients with pacemaker interactive drug resistant tachycardia underwent invasive electrophysiological studies. In the first patient, the retrograde conduction of the artificial reciprocating tachycardia was provided by two right-sided accessory pathways and the antegrade conduction by an atrial synchronous plus generator. In addition, AV nodal tachycardia occurred alternately. In the second patient with intermittent atrial flutter, the AV node and, coincidentally, an AV sequential pulse generator provided high-rate antegrade conduction to the ventricles. In the third patient with surgical complete heart block, intermittent AV-nodal tachycardia induced retrograde atrial activation while an atrial synchronous pacemaker provided the antegrade conduction. Electrode catheter exploration of the heart allowed localization and closed-chest ablation of the accessory pathways or AV node by delivering two to seven 200-Joule direct-current shocks through the appropriate electrode of the exploring catheter, Thereby, pacemaker-mediated arrhythmias could be controlled in these patients in the follow-up of 6 to 8 months.     

Radiofrequency Catheter Ablation of Concealed Atrio-His Bypass Tract Involved in Paroxysmal Supraventricular Tachycardia

In a patient with paroxysmal supraventricular tachycardia and without any evidence for preexcitation syndrome or dual atrioventricular (AV) nodal pathways, the tachycardia reentry circuit consisted of the AV node as an antegrade limb of the circuit and a concealed atrio-His bypass tract located in the posterior septum as a retrograde limb. During the tachycardia, the atrial potentials in the septal region and coronary sinus were inscribed in the QRS complex, and the earliest atrial activation site was located in the posterior septum. Ventricular extrastimulation at critically short intervals reproducibly demonstrated a ventriculo-His-atrial activation sequence with the same earliest retrograde atrial activation site as that during the tachycardia. Radiofrequency energy (20 W) was applied to this earliest activation site during ventricular pacing, which resulted in complete ventriculo-atrial block within 2 seconds after energy application. The antegrade AV conduction property was not affected and the tachycardia was no longer induced. The patient has been free from tachycardia attack for a follow-up period of 8 months. Therefore, radiofrequency catheter ablation for an atrio-His bypass tract is feasible without inducing any AV conduction disturbance.     

New Observations on Decremental Atriofascicular and Nodofascicular Fibers: Implications for Catheter Ablation

Introduction: The purpose of this study was to characterize the anatomy and physiology of accessory pathways that exhibit anterograde decremental conduction. Results: Among 100 consecutive patients with an accessory pathway undergoing electrophysiological study, six individuals with decremental anterograde accessory pathway conduction were identified. Anterograde accessory pathway effective refractory periods and conduction curves were assessed by atrial extrastimulus testing. Atrial pace mapping and ventricular activation sequence mapping were used to define accessory pathway origin and insertion. Surgical ablation (N = 1) or radiofrequency catheter ablation (N = 3) was performed based on accessory pathway anatomy as determined during electrophysiological study. Four of 6 patients had gaps in anterograde accessory pathway conduction. Two patients had evidence of functional longitudinal dissociation in the accessory pathway. Five of 6 patients had atriofascicular fibers with an atrial rather than AV nodal site of origin of their decrementally conducting accessory pathway and with distal insertions in the right bundle branch. Among these five patients, a right posterior atrial origin was nearly as common as a right anterior atrial origin. One patient had a true nodofascicular fiber that arose from the AV node, inserting distally into the left bundle branch. Conclusion: Most accessory pathways with anterograde decremental conduction arise from the right anterior or right posterior atrium, not the AV node. A gap in anterograde accessory pathway conduction and functional longitudinal dissociation are common in such accessory pathways. Surgical or catheter ablation of such pathways is effective when directed at the atrial origin of the accessory pathway. True nodofascicular fibers arising from the AV node are rare. These may insert distally in the left ventricle. Catheter ablation of the proximal origin of such fibers is likely to result in complete AV block.     

Atrioventricular Node Reentry: Physiology and Radiofrequency Ablation

Atrioventricular (A V) node reentry has heen recognized as a clinical arrhythmia for many years. Earlier basic investigations identified a dual AV conduction system, and atrial echo beats occurred when the refractory period of the slow conduction pathway was shorter than the fast pathway. Subsequent studies in humans confirmed the concept of dual AV node physiology and AV node reentry. Slow-fast AV node reentry (anterograde conduction over the slow pathway and retrograde conduction over the fast pathway) occurs most frequently. The fast-slow and intermediate varieties are much less common. A high (> 95%) cure rate occurs with radiofrequency catheter ablation with experienced electrophysiologists. Most electrophysiologists prefer the posterior approach, which results in absence or very poor conduction over the slow AV node pathway; the PR interval is minimally changed. This approach is highly successful for all three forms of AV node reentry and associated with a 1%–2% incidence of heart block in most experienced laboratories.     

Electrophysiological characteristics of junctional rhythm during ablation of the slow pathway in different types of atrioventricular nodal reentrant tachycardia

BACKGROUND: Junctional rhythm (JR) is commonly observed during radiofrequency (RF) ablation of the slow pathway for atrioventricular (AV) nodal reentrant tachycardia. However, the atrial activation pattern and conduction time from the His-bundle region to the atria recorded during JR in different types of AV nodal reentrant tachycardia have not been fully defined. METHODS: Forty-five patients who underwent RF ablation of the slow pathway for AV nodal reentrant tachycardia were included; 27 patients with slow-fast, 11 patients with slow-intermediate, and 7 patients with fast-slow AV nodal reentrant tachycardia. The atrial activation pattern and HA interval (from the His-bundle potential to the atrial recording of the high right atrial catheter) during AV nodal reentrant tachycardia (HA(SVT)) and JR (HA(JR)) were analyzed. RESULTS: In all patients with slow-fast AV nodal reentrant tachycardia, the atrial activation sequence recorded during JR was similar to that of the retrograde fast pathway, and transient retrograde conduction block during JR was found in 1 (4%) patient. The HA(JR) was significantly shorter than the HA(SVT) (57 +/- 24 vs 68 +/- 21 ms, P < 0.01). In patients with slow-intermediate AV nodal reentrant tachycardia, the atrial activation sequence of the JR was similar to that of the retrograde fast pathway in 5 (45%), and to that of the retrograde intermediate pathway in 6 (55%) patients. Transient retrograde conduction block during JR was noted in 1 (9%) patient. The HA(JR) was also significantly shorter than the HA(SVT) (145 +/- 27 vs 168 +/- 29 ms, P = 0.014). In patients with fast-slow AV nodal reentrant tachycardia, retrograde conduction with block during JR was noted in 7 (100%) patients. The incidence of retrograde conduction block during JR was higher in fast-slow AV nodal reentrant tachycardia than slow-fast (7/7 vs 1/11, P < 0.01) and slow-intermediate AV nodal reentrant tachycardia (7/7 vs 1/27, P < 0.01). CONCLUSIONS: In patients with slow-fast and slow-intermediate AV nodal reentrant tachycardia, the JR during ablation of the slow pathway conducted to the atria through the fast or intermediate pathway. In patients with fast-slow AV nodal reentrant tachycardia, there was no retrograde conduction during JR. These findings suggested there were different characteristics of the JR during slow-pathway ablation of different types of AV nodal reentrant tachycardia.     

Computer Model of the Atrioventricular Node Predicts Reentrant Arrhythmias

Introduction: Following atrial premature beats, the AV node may exhibit sustained reentrant tachyarrhyth-mias, isolated echo beats, or discontinuities in the recovery curve (the plot of conduction time versus atrial cycle length). A computer model was used to examine the hypothesis that spatial variation of AV nodal passive electrical resistance may account for these phenomena. Methods and Results: A computer model of a rectangular lattice of elecirotonically linked elements whose ionic kinetics simulated nodal ionic flux was developed. the model showed that there exists a resistance value that minimizes the effective refractory period, because high resistance prevents depolarization of distal elements, while low resistance allows leakage of depolarizing current by electrotonic transmission, preventing activation of proximal elements. High resistances stabilized reentry by slowing conduction. Simulations incorporating equal resistance values between elements predicted increased AV nodal conduction times with increasing prematurity of atrial impulses. A model with a gradual change in resistance between fibers produced discontinuities and tachycardia, but not both simultaneously. Uniform anisotropy produced preferential transverse block, leading to echo beats and “fast-slow” tachycardia, but not recovery curve discontinuities. Nonuniform anisotropy could produce reentry, but tachycardia often occurred without discontinuities. Dividing the lattice into two electrotonically linked parallel pathways with different resistance values (“dual pathway model”) predicted recovery curve discontinuities, echo beats, and tachycardia. At critical atrial cycle lengths, only the (high resistance) slow pathway conducted antegradely, while the fast pathway conducted retrogradely, to generate the typical “slow-fast” tachycardia. Responses of the dual pathway model to ablation were consistent with clinical data, including the previous observation of a decrease in fast pathway effective refractory period after slow pathway ablation. Conclusion: Differences in passive electrical resistance of electrotonically linked dual pathways within the AV node may account for functional longitudinal dissociation, reentrant arrhythmias, and responses to catheter ablation therapy.     

Nonfluoroscopic Guidance for Catheter Placement into the Coronary Sinus under Direct Vision Using a Balloon-Tipped Cardioscope

The right atrial posterior septum, including the coronary sinus (CS) ostium, is an important landmark in radio frequency catheter ablation therapy for supraventricular tachycardia or atrial flutter. The anatomical findings around the CS ostium would be useful to determine a target site or line during catheter ablation. The aim of the study was to test the ability of the imaging catheter to identify structures in the posterior septal area of the right atrium and to evaluate the feasibility of guidance for catheter placement in the CS using a cardiosccpe that we recently developed. In 12 anesthetized dogs, the Cardioscope, consisting of a deflectable 7 Fr fiberoptic endoscope with an inflatable and transparent balloon, was introduced into the right atrium via the femoral vein. The cardioscope was manipulated to observe the right atrial posterior septum. A deflectable electrode catheter was inserted via the jugular vein and positioned in the CS under cardioscopic guidance. In 10 of 12 dogs, the right atrial posterior septum, including the CS ostium, and the tendon of Todaro could be anatomically identified by cardioscopy. It was possible to position an electrode catheter in the CS in all 10 dogs under direct vision without fluoroscopy. But the CS ostium could not be detected in the remaining two dogs, although the cardioscope was placed at as many sites as possible. No complication occurred. The balloon-tipped cardioscope appears to be useful in observing the right atrial posterior septum and in guiding an electrode catheter into the CS.     

Direct Angiography of the Coronary Sinus: Impact on Left Posteroseptal Accessory Pathway Ablation

The purpose of this study was to determine the incidence and types of venous branches and anomalies in posteroseptal accessory pathways (APs) and whether these findings are indicative for successful ablation sites. Some posteroseptal APs may be located epicardially, or may be associated with venous anomalies or related to the middle cardiac vein. These APs account for many of the failures encountered during endocardial ablation. Direct coronary sinus (CS) angiography was performed in 43 consecutive patients with left posteroseptal APs (n - 23) and in 20 patients with A V nodal reentrant tachycardia prior to catheter ablation. In 14 (61%) of 23 APs, a venous branch or an anomaly of the CS was found in the posteroseptal region (6 with middle cardiac vein, 2 with other ventricular venous branches, and 6 had a diverticulum). Eleven (48%) of 23 APs were successfully abolished from within that demonstrated venous system, with a median of four radio frequency impulses. In the remaining 12 (52%) patients, ablation was attempted from the endocardial site of the mitral annulus. Repeat angiography after energy delivery revealed no major complications in any patient. One (5%) patient with AV nodal reentrant tachycardia had evidence of a CS anomaly (P < 0.01). Various types of venous branches and anomalies are associated with the majority of patients with left posteroseptal APs. The APs are directly related to these complex findings, and AP conduction can easily be eliminated from within the venous branches. CS angiography is suggested prior to catheter ablation of left posteroseptal APs to facilitate the ablation procedure.     

Diffuse Conduction Abnormalities in an Adolescent with Familial Sinus Node Disease

We report a case of familial sinus node disease with associated conduction abnormalities in the atrioventricular node and distal conduction system Spontaneous atrial pacemaker activity was absent though the atrium could be depolarized. The pacemaker activity of the heart resided in the atrioventricular junction. The AV node showed impaired automaticity and abnormal conduction properties which partially improved after vagal blockage.     

Right-Sided Versus Left-Sided Radiofrequency Ablation of the His Bundle

Radiofrequency (RFJ ablation of the His bundle was attempted in 30 consecutive patients with atrial flutter or fibrillation. A 7 French quadripolar catheter with a 4-mm distal electrode was advanced from the right femoral vein (21 patients), or subclavian vein (two patients) and positioned across the tricuspid valve. Adequate His-bundle potentials were obtained in all patients. However, in six patients atrioventricular (AV) block could not be obtained after multiple (mean = 8) applications of RF energy from the conventional right-sided approach. In these patients the same catheter was advanced to record a His potential through a retrograde arterial approach. AV block was created in all patients with one to three applications of RF energy. The duration of the procedure was 22 to 90 minutes for the right-sided approach and 5 to 10 for the left-sided approach (P < 0.005). Subsequently, in seven patients a left-sided approach was used first. One to six applications of RF energy were required to create AV block. The radiation exposure time was 3 to 20 minutes. No complications occurred. Conclusions: RF ablation of the His bundle seems easier using a left-sided than a right-sided approach, reduces procedure and radiation time, and avoids recovery of conduction. These data suggest that a left-sided approach, in spite of requiring arterial catheterization, may be preferable to a right-sided approach.     

Using Intracardiac Catheter Recordings from the His and Proximal Coronary Sinus to Distinguish Isthmus Conduction Block During Catheter Ablation of Type I Atrial Flutter

Isthmus conduction block, demonstrated with the use of multipolar catheter recordings, is considered the preferred endpoint for ablation of type I atrial flutter. This study investigated the feasibility of using recordings from the His and coronary sinus (CS) to document isthmus conduction block. Isthmus conduction block was produced with linear radiofrequency (RF) ablation in 27 patients with type I atrial flutter. In 13 patients (group I), RF was delivered until bidirectional isthmus conduction block was demonstrated with multipolar Halo catheter recordings. In 14 patients (group II), RF was delivered during pacing from the lateral isthmus at 600 ms until a reversal in activation of the proximal CS and His occurred. At this point, data from the Halo recordings were reviewed to see if reversal correlated with conduction block; if not, further ablation was performed until block was demonstrated. The initial reversal in His and CS activation during RF energy delivery correlated with isthmus block in only 4 (28.6%) of 14 patients in group II. Additional RF delivery produced isthmus block in the other ten patients resulting in a further increase in the St-CS interval of 35 ± 20 ms. A His-CS interval of at least -40 ms signified isthmus block with a sensitivity and specificity of 48% and 100%, respectively. Reversal in His-CS activation during pacing from the lateral margin of the isthmus is not specific for the creation of isthmus block. While activation of the proximal CS bipole > 40 ms after activation of the His appears specific for isthmus block, the low sensitivity of this finding limits its clinical use.     

Nonuniformity of AH Intervals During Stimulation at Different Left Atrial Sites

Studies in humans have found left atrial stimulation via the coronary sinus (CS) to elicit significantly shorter atrium-His (AH) intervals as compared to right atrial stimulation, but whether pacing at dijferent left atrial sites (anterior vs posterior left atrium, i.e., far distal vs proximal CSJ affects the AH interval has not been studied. Hence, in 22 patients, we compared the effects of stimulation from various atriai sites, including anterior high right atrium (HRA), distal CS, mid-CS, and proximal CS, on; stimulus-atrium (SA), AH, and stimuIus-His intervals on the His bundle electrogram. Paced cycle length differed for each patient (range 900–350 msec, mean 532 ± 140 msec), but conduction intervals from different atrial sites were compared using identical cycle length in each patient. The mean SA intervals were 34 ± 10 msec, 57 ± 10 msec, 44 ± 11 msec, and 32 ± 8 msec with stimulation, respectively, from HRA, distal CS, mid-CS. and proximal CS (each significantly different except for HRA vs proximal CSJ. The mean AH intervals were 123 ± 23 msec, 104 ± 28 msec, 95 ± 15 msec, and 90 ± 18 msec with stimulation, respectively, from HRA, distal CS, mid-CS, and proximal CS (each significantly different except for mid-CS vs proximal CSJ. In 13 patients, the discrepancy in AH intervals during distal versus proximal CS stimulation was > 15 msec; in 9 patients this difference was only < 10 msec, considered within the range of measurement error. Thus, in a significant portion of patients, discrepant AH intervals were demonstrated during stimulation from the distal versus proximal CS. These previously undescribed observations suggest that electrophysiological studies on atrioventricular nodal conduction that involve left atrial stimulation must take into account actual location of the stimulation site (anterior or posterior) in order to properly interpret the findings.     

The annular fat stripe as a fluoroscopic guide to anatomic sites during diagnostic and interventional electrophysiology studies

Few radiographic landmarks are visible during electrophysiology procedures to aid in catheter positioning other than the catheters themselves. In the 35 degrees -45 degrees RAO projection, a linear radio-opacity corresponding to the rings of fat surrounding both annuli can be easily identified. This "fat stripe" can serve as a useful landmark for several important anatomic sites. Intracardiac catheters positioned left of (posterior) the fat stripe lie within an atrial cavity while those positioned to the right (anterior) lie within a ventricular cavity. The superior third of the stripe corresponds to the region of the right and left atrial appendages while the inferior end identifies the site of the coronary sinus os. The middle third serves as a reference for the fast AV nodal pathway and compact AV node. The region corresponding to the slow AV nodal pathway superimposes on the lower third of the fat stripe. Electrophysiological recordings from catheters positioned along the fat stripe always exhibit both an atrial and ventricular component consistent with an annular recording, whether the catheter is septal or free wall in its location. Coronary sinus os engagement and catheterization can be simplified by using the fat stripe as an anatomic guide. In addition to facilitating catheter positioning for evaluating normal AV conduction, the fat stripe can serve as an excellent guide for targeting the majority of structures intended for ablation because of their annular location. These include the compact AV node, the slow AV nodal pathway, the subeustachian isthmus and any accessory pathway. Good ablation catheter tip contact with annular structures is confirmed by observing its movement in unison with the fat stripe.     

Atrial Septal Pacing to Synchronize Atrial Depolarization in Patients with Delayed Interatrial Conduction

The current method of pacing the right atrium from the appendage or free wall is often the source of delayed intraatrial conduction and discoordinate left and right atrial mechanical function. Simultaneous activation of both atria with pacing techniques involving multisite and multilead systems is associated with suppression of supraventricular tachyarrhythmias and improved hemodynamics. In the present study we tested the hypothesis that pacing from a single site of the atrial septum can synchronize atrial depolarization. Five males and two females (mean age 58 ± 6 years) with drug refractory paroxysmal atrial fibrillation (AF) were studied who were candidates for AV junctional ablation. All patients had broad P waves (118 ± 10 ms) on the surface ECG. Multipolar catheters were inserted and the electrograms from the high right atrium (HRA) and proximal, middle, and distal coronary sinus (CS) were recorded. The atrial septum was paced from multiple sites. The site of atrial septum where the timing between HRA and distal CS (d-CS) was ≤ 10 ms was considered the most suitable for simultaneous atrial activation. An active fixation atrial lead was positioned at this site and a standard lead was placed in the ventricle. The interatrial conduction time during sinus rhythm and AAT pacing and the conduction time from the pacing site to the HRA and d-CS during septal pacing were measured. Atrial septal pacing was successful in all patients at sites superior to the CS os near the fossa ovalis. During septal pacing the P waves were inverted in the inferior leads with shortened duration from 118 ± 10 ms to 93 ± 7 ms (P < 0.001), and the conduction time from the pacing site to the HRA and d-CS was 54.3 ± 6.8 ms and 52.8 ± 2.5 ms, respectively. The interatrial conduction time during AAT pacing was shortened in comparison to sinus rhythm (115 ± 18.9 ms vs 97.8 ± 10.3 ms, P < 0.05). In conclusion, simultaneous activation of both atria in patients with prolonged interatrial conduction time can be accomplished by pacing a single site in the atrial septum using a standard active fixation lead placed under electrophysiological study guidance. Such a pacing system allows proper left AV timing and may prove efficacious in preventing various supraventricular tachyarrhythmias.