Anatomic guidance for ablation: atrial flutter, fibrillation, and outflow tract ventricular tachycardia

Abstract

After initial documentation of excellent efficacy with radiofrequency ablation, this procedure is being performed increasingly in more complex situations and for more difficult arrhythmia. In these circumstances, an accurate knowledge of the anatomic basis for the ablation procedure will help maintain this efficacy and improve safety. In this review, we discuss the relevant anatomy for electrophysiology interventions for typical right atrial flutter, atrial fibrillation, and outflow tract ventricular tachycardia. In the pediatric population, maintaining safety is a greater challenge, and here again, knowing the neighboring and regional anatomy of the arrhythmogenic substrate for these arrhythmias may go a long way in preventing complications.

Keywords: ablation; anatomy; atrial fibrillation; atrial flutter; electrophysiology.

Figure 1

What the ablationist sees in his/her eyes when picturing the cavotricuspid isthmus. Note the electrically inert tricuspid valve and what we expect to be a relatively flat terrain between the tricuspid valve and inferior vena cava. TV - tricuspid valve; isth - isthmus; ABL - ablation; CS - coronary sinus; IVC - inferior vena cava.

Figure 2

A more realistic view from an actual autopsied heart. The complex regional anatomy of the cavotricuspid isthmus. The arrow points to the sub-Eustachian pouch. Note the prominent Thebesian valve guarding the opening of the coronary sinus (CS). A prominent Eustachian ridge (ER) and valve associated with the Eustachian ridge are also visualized.

Figure 3

Dissection of an autopsied heart showing left anterior oblique-like view looking through the tricuspid valve into the right atrium with an ablation catheter and guiding sheath placed across the CVTI. Note the large pectinate muscles emanating from the crista terminalis (CT). Many pectinates are seen encroaching onto the CVTI and traversing the isthmus into the coronary sinus (CS).

Figure 4

Computerized-tomographic images illustrating pulmonary vein stenosis. Note the abrupt stenosis just into the pulmonary vein. The lower images represent three-dimensional reconstructions. Pulmonary vein stenosis will not result if ablation delivery is kept proximal to the pulmonary vein ostium. Arrow points to pulmonary vein stenotic areas.

Figure 5

Intracardiac ultrasound image showing the circumferential mapping catheter (arrow) exactly at the ostium of the pulmonary vein. Especially for the left-sided veins, ultrasound imaging can be helpful in approximating where the pulmonary vein ostium is located. LA - left atrium

Figure 6

Intracardiac electrograms obtained from a left-sided pulmonary vein. The lasso, a circumferential mapping catheter, has been placed into the vein. Note the far-field atrial signals, isoelectric period, and the sharp near-field pulmonary vein potentials. If an ablation catheter shows such a signal, then it is likely located inside the pulmonary vein. Coronary sinus pacing is being performed. CS - coronary sinus; HBE - His bundle recorded catheter; HRA - right atrial catheter; RV - right ventricular catheter; V1 and II - electrocardiographic leads.

Figure 7

Arterial damage may occur at several locations when ablating in the left atrium for atrial fibrillation. The circumflex artery may be damaged during left atrial isthmus ablation or attempts at coronary sinus isolation. Anterior mitral annular tachycardia ablation or coronary cusp atrial tachycardia ablation may injure the proximal left coronary arterial system. Finally, when ablating in the proximal coronary sinus, distal branches of the right coronary artery are at risk.

Figure 8

Computerized-tomographic image showing a sagittal view supposing the esophageal/left atrium relationship. Note in this patient, a large left atrium abuts and indents into the anterior wall of the esophagus. LA - left atrium; ESO - esophagus

Figure 9

Anterior view of the heart showing the important overlapping nature of the outflow tract course. Note the right ventricular outflow tract and pulmonary artery lie anterior and to the left of the left ventricular outflow tract and aorta. LV - left ventricle; RV - right ventricle; PA - pulmonary artery; Ao - aortic valve. (Figure courtesy of Dr. William D. Edwards)

Figure 10

12-lead electrocardiogram from a young female with frequent ventricular ectopy and likely resulting cardiomyopathy. At first glance, the electrocardiogram appears typical of right ventricular outflow tract tachycardia. However, this patient had three failed prior ablations. Note the small r wave in lead V1. An R wave in V1 also results when ectopy origin is from the posterior right ventricular outflow tract or right coronary cusp. Constant correlation between anatomy, electrocardiography, and fluoroscopy are essential for safe ablation in this region, particularly in children.