Unusual variants of pre-excitation: From anatomy to ablation: Part I-Understanding the anatomy of the variants of ventricular pre-excitation.

The famous quotation of Winston Churchill, made in his radio broadcast of 1939 regarding Russia's next move, specifically "A riddle wrapped up in a mystery, inside an enigma," perfectly fits the current understanding of unusual accessory atrioventricular pathways, including the variants producing ventricular pre-excitation. It was many decades after their original descriptions that we came better to begin to understand most of their structure-function relationships. Their mysterious pathophysiology was sometimes unveiled after invasive treatments, such as surgical ablation of the atrioventricular conduction axis instead of the accessory pathway itself. Speculations made on this basis have largely been validated by subsequent clinical experience. Most of the names suggested for description of the pathways have stood well the test of time. For some of them, however, this is not the case, with the initial names becoming confusing. In a series of reviews, we re-visit those accessory pathways producing ventricular pre-excitation other than classical Wolff-Parkinson-White syndrome. To set the scene, in this initial review, we describe the development and anatomy of the normal atrioventricular conduction axis, along with the insulating tissues of the atrioventricular junctions. We have sought to illustrate our explanations by using virtual dissection of computerized tomographic datasets, since they retain the intact heart within the setting of the body. These images illustrate well the value of attitudinally appropriate terminology. Thereafter, we discuss the electrophysiological manifestations of the abnormal anatomical pathways which provide the potential for both accessory atrioventricular and intraventricular conduction.

Percutaneous Catheter Ablation of Epicardial Accessory Pathways.

Radiofrequency (RF) catheter ablation is the treatment of choice in patients with accessory pathways (APs) and Wolff-Parkinson-White syndrome. Endocardial catheter ablation has limitations, including the inability to map and ablate intramural or subepicardial APs. Some of these difficulties can be overcome using an epicardial approach performed through the epicardial venous system or by percutaneous catheterisation of the pericardial space. When a suspected left inferior or infero-paraseptal AP is refractory to ablation or no early activation is found at the endocardium, a transvenous approach via the coronary sinus is warranted because such epicardial pathways can be in close proximity to the coronary venous system. Associated congenital abnormalities, such as right atrial appendage, right ventricle diverticulum, coronary sinus diverticulum and absence of coronary sinus ostium, may also hamper a successful outcome. Percutaneous epicardial subxiphoid approach should be considered when endocardial or transvenous mapping and ablation fails. Epicardial mapping may be successful. It can guide and enhance the effectiveness of endocardial ablation. The finding of no epicardial early activation leads to a more persistent new endocardial attempt. When both endocardial and epicardial ablation are unsuccessful, open-chest surgery is the only option to eliminate the AP.

Accessory atrioventricular pathways refractory to catheter ablation: role of percutaneous epicardial approach.

BACKGROUND: Epicardial mapping and ablation of accessory pathways through a subxiphoid approach can be an alternative when endocardial or epicardial transvenous mapping has failed. METHODS AND RESULTS: We reviewed acute and long-term follow-up of 21 patients (14 males) referred for percutaneous epicardial accessory pathway ablation. There was a median of 2 previous failed procedures. All patients were highly symptomatic, 8 had atrial fibrillation (3 with cardiac arrest) and 13 had frequent symptomatic episodes of atrioventricular reentrant tachycardia. Six patients (28.5%) had a successful epicardial ablation. Five patients (23.8%) underwent a successful repeated endocardial mapping, and ablation after epicardial mapping yielded no early activation site. Epicardial mapping was helpful in guiding endocardial ablation in 2 patients (9.5%), showing that the earliest activation was simultaneous at the epicardium and endocardium. Four patients (19%) underwent successful open-chest surgery after failing epicardial/endocardial ablation. Two patients (9.5%) remained controlled under antiarrhythmic drugs after unsuccessful endocardial/epicardial ablation. Two patients had a coronary sinus diverticulum and one a right atrium to right ventricle diverticulum. Three patients acquired postablation coronary sinus stenosis. There was no major complication related to pericardial access. CONCLUSIONS: Percutaneous epicardial approach is an alternative when conventional endocardial or transvenous epicardial ablation fails in the elimination of the accessory pathway. A new attempt by endocardial approach was successful in a significant number of patients. Open-chest surgery may be required in symptomatic cases refractory to endocardial-epicardial approach.

Postablation-acquired short atrioventricular Mahaim-type fibers: observations on their clinical, electrocardiographic, and electrophysiologic profile.

BACKGROUND: The electrophysiologic characteristics of decrementally conducting accessory pathways (APs) are well described; however, little is known about decrementally conducting APs caused by the radiofrequency ablation of a rapidly conducting AP. OBJECTIVE: To report the clinical, electrocardiographic, and electrophysiologic characteristics of 6 patients who developed a decremental AP after an attempt at ablation. METHODS: We compared the clinical and electrophysiologic characteristics of 295 consecutive patients with the Wolff-Parkinson-White syndrome who underwent radiofrequency ablation of 311 manifest APs (group A) with those of 6 patients with the Wolff-Parkinson-White syndrome in whom a decrementally conducting AP was detected after an attempt at ablation. RESULTS: The AP ablation site in group B patients was at the coronary sinus ostium region in 3 patients, middle cardiac vein in 2 patients, and left posteroseptal region in 1 patient. Sixty-two bypass tracts in group A patients and all 6 in group B patients were ablated at these locations, while 249 bypass tracts in group A patients and none in group B patients were ablated elsewhere (P = .0001). Five of the 6 patients (83%) with acquired Mahaim physiology had an AP located in the venous system. The odds for developing an acquired decremental antegrade atrioventricular AP when it was located inside the venous system were 1 in 6. All group B decremental APs were sensitive to adenosine, but none in 85 group A patients (P <.0001). CONCLUSIONS: The risk for developing decremental conduction after the ablation of a rapidly conducting AP is greater for APs inside the coronary venous system. Acquired decremental antegrade atrioventricular APs are electrophysiologically similar to de novo ones. They are capable of being part of an arrhythmia circuit and, therefore, should be targeted for ablation.