M. Zardini

Iterative atrial tachycardia originating from the coronary sinus musculature.

Coronary Sinus Atrial Tachycardia. A case of iterative atrial tachycardia leading to dilated cardiomyopathy is reported. During electrophysiologic study, the tachycardia showed a markedly irregular cycle length associated with changes in atrial activation breakthrough as demonstrated by coronary sinus (CS) recordings and frequently degenerated into self‐terminating atrial fibrillation. Left atrial transseptal mapping demonstrated the earliest endocardial atrial activation close to the posterolateral mitral annulus, but this was invariably later than that recorded within the CS, where low‐energy radiofrequency applications eliminated the tachycardia. No acute vessel damage was observed at postablation CS angiography. In accordance with previously published experimental data, we hypothesized that the muscular sleeves surrounding the CS might be involved in the genesis of this tachycardia. During 6‐month follow‐up, the patient remained asymptomatic without tachycardia recurrences and with complete recovery of left ventricular function, confirming the reversible nature of the tachycardia‐induced cardiomyopathy.

Comparison of single premature versus continuous overdrive stimulation for identification of a protected isthmus in macro-reentrant atrial tachycardia circuits

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Ablation of Antero-Septal and Intermediate Septal Accessory Pathways: How Safe Is It? How Can One Minimize the Risk of AV Block?

The current goal of radiofrequency catheter ablation of supraventricular tachycardias is to cure a large cohort of patients with a primary success rate close to 100% and a complication and recurrence rate close to 0%. In this setting, the ablation of the atrioventricular (A-V) accessory pathway in the triangle of Koch may still represent a grey area, since the strict anatomical relationship between the bypass tract and the A-V node-His bundle may affect the feasibility and safety of the procedure. Consequently, the only rationale for successful ablation with no complication in this area relies on the assumption that the accessory pathway is more sensitive to radiofrequency energy delivery than the normal A-V conduction system [1]. The risk of damaging the normal A-V conduction pathway and of inducing a complete A-V block requiring a permanent pacemaker has been pointed out by both early [2, 3] and recent [4–6] reports, although successful and safe ablation has been described in limited series of cases [7, 8], even with “para-hissian” accessory pathways [1]. Moreover, in the risk/benefit ratio of ablation of by-pass tracts in the Koch’s triangle one must consider not only failure and the risk of permanent complete A-V block, but also the theoretical possibility of creating an incessant reentrant circuit by partially damaging both the accessory pathway and the A-V node conduction.

“Incisional” Reentrant Atrial Tachycardia: How to Prevent and Treat It?

Patients submitted to cardiac surgery for correction of congenital or acquired heart diseases may subsequently experience several types of atrial tachyarrhythmias [1–4]. Most of these are macroreentrant atrial tachycardias strictly related to the presence of scars, prosthetic materials, or conduits and have therefore been named “incisional” or “scar-related” atrial tachycardias. Although their electrocardiographic characteristics may resemble those of atrial flutter, slight differences in P wave morphology and tachycardia cycle length are present and should be identified in order to formulate the correct diagnosis. “Incisional” atrial tachycardia may occur at widely variable times after the operation, most frequently in patients submitted to septal atrial defect repair and Fontan or Mustard procedures for tricuspid atresia or great vessel transposition correction, respectively. The true prevalence of these arrhythmias is unknown; small retrospective series reported a prevalence of 32–57% after the Fontan procedure [4, 6, 7] and about 15% after the Mustard operation [3, 8].

Prolonged or Failed Attempts at RF Ablation of Accessory Pathways: What Are the Causes?

In 1997 almost the entire population with arrhythmias related to the presence of an anomalous AV pathway (AP) is treated successfully by radiofrequency catheter ablation (RF-CA) without excessive difficulty, but in some cases a very prolonged procedure or a second session or both are required to obtain a successful outcome [1].