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.

Electroanatomic magnetic mapping during ablation of isthmus-dependent atrial flutter.

INTRODUCTION: Although recent studies have demonstrated that the endpoint of isthmus conduction block is superior to that of termination and subsequent inability to induce atrial flutter (AFl), the optimal method for determining isthmus conduction block has not been determined. Electroanatomic magnetic mapping during coronary sinus (CS) pacing may provide a reliable endpoint for AFl ablation. METHODS AND RESULTS: Catheter mapping and ablation was performed in 42 patients with isthmus-dependent AFl. The patients were divided into two groups, based on procedural endpoint: Group I (28 patients) - isthmus conduction block was determined based on multipolar catheter recordings and electroanatomic mapping, and Group II (14 patients) - isthmus conduction block was determined by electroanatomic mapping during CS pacing alone. In Group I, ablation procedures were acutely successful in 25 of 28 patients (89 %). A 100 % concordance between the data presented by multipolar catheter recordings and electroanatomic mapping was noted in determining the presence or absence of isthmus conduction block. In Group II, ablation procedures were acutely successful in 13 of 14 patients, 13 (93 %). After a mean of 16.3+/-3.7 months follow up, there was 1 atrial flutter recurrence in the 38 patients (2.6 %) with demonstrated isthmus block at the end of the procedure. CONCLUSIONS: Electroanatomic magnetic mapping during CS pacing is comparable to the multipolar catheter mapping technique for assessing isthmus conduction block as an endpoint for AFl ablation procedures.

Antidromic reciprocating tachycardia in patients with paraseptal accessory pathways: importance of critical delay in the reentry circuit.

Previous studies in patients with antidromic reciprocating tachycardia (ART) have observed a critical anatomic requirement (> 4 cm) between an antegrade bypass tract limb and a retrograde AV nodal limb. We report two patients with ART utilizing a paraseptal accessory pathway. In both cases, a critical degree of slow conduction within the circuit provides unusual electrophysiologic substrate to overcome the expected anatomical constraints.

Type I atrial flutter ablation guided by a basket catheter.

Bidirectional isthmus conduction block has been associated with a low recurrence rate after atrial flutter ablation. We present the case of a type I, typical or "counterclockwise" atrial flutter ablation guided by stimulation and recordings obtained from a basket catheter, which allowed for constant electrogram recording from splines positioned along the right lateral free wall and septum. After atrial flutter termination with radiofrequency application, the ability to record and stimulate from multiple sites in the atrium using the basket catheter was useful to detect residual bidirectional slow conduction through the isthmus. Complete isthmus block could be documented after additional radiofrequency energy applications.

Implantable cardioverter defibrillator oversensing during periods of rate-related bundle branch block.

A patient with an implantable cardioverter defibrillator (ICD) and a dual chamber pacemaker experienced inappropriate ICD therapies only during periods of rate-dependent right bundle branch block. Analysis of both stored and real-time ICD electrograms was critical to correctly diagnosing the problem and offering a solution.

Sustained bundle branch reentry in a patient with hypertrophic cardiomyopathy and nondilated left ventricle.

Ventricular tachycardia is a well-known complication in patients with hypertrophic cardiomyopathy. We report the case of a patient with hypertrophic cardiomyopathy with easily inducible monomorphic ventricular tachycardia. Electrophysiology study demonstrated that bundle branch reentry was the mechanism of the tachycardia. The tachycardia was rendered non-inducible by radiofrequency ablation of the right bundle branch.