Biatrial Tachycardia: Distinguishing Between Active and Passive Activation.

Abstract

The approach to successful ablation of arrhythmias is based on elucidating the underlying mechanism and relative dimensions of the tachycardia circuit. Activation mapping readily distinguishes macroreentry from focal arrhythmias, the latter of which have centrifugal spread. When macroreentrant atrial tachycardia is suspected, entrainment maneuvers with atrial overdrive pacing at various anatomic sites help differentiate right-sided from left-sided circuits. Based on the difference between the postpacing interval (PPI) and tachycardia cycle length (TCL), the proximity of the pacing site to the reentrant circuit can be assessed.1 However, even in a reentrant tachycardia, a short PPI–TCL interval (< 30 ms) may not always reliably identify whether the pacing site is within the tachycardia circuit, particularly when widely disparate locations seem to be “in the circuit”. In these cases, it is important to return to the fundamental principles of entrainment and to recognize the subtle changes in antidromic and orthodromic wavefronts in response to overdrive pacing that help to correctly identify the tachycardia circuit. See Editor’s Perspective by Asirvatham and Stevenson A 57-year-old man with a history of hypertension, hyperlipidemia, coronary artery disease, rheumatic heart disease, and 5 previous surgeries for mechanical aortic and mitral valve replacements and coronary artery bypass grafting presented with 6 months of worsening dyspnea on exertion that correlated with the onset of persistent atrial tachycardia (Figure 1). In the electrophysiology laboratory, the patient’s clinical atrial TCL was 360 ms. Diagnostic catheters were placed to encircle the tricuspid annulus within the coronary sinus (CS) and at the superior margin of the tricuspid annulus to record the His bundle (Figure 2A). Entrainment mapping demonstrated a short PPI–TCL from the cavotricuspid isthmus (CTI; Figure 2B), the proximal CS (Figure 2C), and the superior tricuspid annulus (Figure 2D). Entrainment from the distal CS also showed a PPI–TCL of 0 ms (Figure …