Adenosine-Insensitive Focal Atrial TachycardiaEvidence for De Novo Micro–Re-Entry in the Human Atrium
Steven M. Markowitz, MD, FACC*,
Dmitry Nemirovksy, MD,
Kenneth M. Stein, MD, FACC,
Suneet Mittal, MD, FACC,
Sei Iwai, MD, FACC,
Bindi K. Shah, MD, FACC,
David P. Dobesh, MD and
Bruce B. Lerman, MD, FACC
Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, New York
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Figure 1 Termination With Adenosine of Focal AT Arising From the Anteroseptal Left Atrium
Shown are surface leads I, aVF, and V1, intracardiac bipolar recordings from the His bundle (HIS), coronary sinus (CS), and a multipolar catheter around the tricuspid annulus (RA-Halo). After adenosine 6 mg, the tachycardia cycle length slows before termination of the arrhythmia. AT = atrial tachycardia; d = distal; SR = sinus rhythm.
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Figure 2 Site of Origin of the Same Adenosine-Sensitive AT From Figure 1, Localized to the Anteroseptal LA Near the Mitral Annulus
(A) Shown are same surface and intracardiac electrograms as in Figure 1, and recordings from the mapping catheter at the site of successful ablation. The electrogram at site of successful ablation is relatively narrow (58 ms) and high amplitude (0.86 mV). (B) An isochronal electroanatomic map of the left atrium (LA) in the left anterior oblique projection demonstrates a focal site of early activation in the region of the anteroseptal mitral annulus with centrifugal propagation in the LA. LAT = lateral; MV = mitral valve; p = proximal; other abbreviations as in Figure 1.
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Figure 3 Adenosine-Insensitive Focal Atrial Tachycardia From a Patient With Muscular Dystrophy (Patient #5, Table 2)
After adenosine 12 mg, high-grade atrioventricular block occurs, but the tachycardia cycle length and activation sequence are unchanged. The earliest activation in the coronary sinus (CS) appears in the mid-posterior poles (CS 5,6). The right atrium (RA) is activated by wave fronts that fuse in the lateral wall. Note that conduction delay from the left atrium to lateral RA approximates the tachycardia cycle length.
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Figure 4 LA Electroanatomical Maps of the Adenosine-Insensitive Focal AT From Patient #5
Posterior views are shown for both isochronal and voltage maps. (A) The isochronal map demonstrates an early site of activation in the posterior left atrium (LA) near the ostium of the left inferior pulmonary vein. (B) In the voltage map, voltages >0.3 mV are purple. A small region of lower voltage is present near the site of early activation, with a minimum voltage of 0.13 mV. (C) Electrogram recorded at successful ablation site is low amplitude, wide, and highly fractionated, as recorded in the Carto system (left) and conventional recording system (right). (D) Termination of atrial tachycardia (AT) by applying 1.6 s of radiofrequency (RF) energy at site of fractionated electrogram. ABL d = ablation distal; CS = coronary sinus.
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Figure 5 Entrainment of Adenosine-Insensitive Focal Atrial Tachycardia From Patient #5
Pacing from the early site accelerates the tachycardia, and the post-pacing interval (PPI) approximates the tachycardia cycle length (TCL). Note that the morphology of some electrograms in the coronary sinus (CS) are different during pacing, suggesting activation by an altered wave front. These findings are consistent with pacing from the "outer loop" of the re-entrant circuit. ABL = ablation; d = distal; LA = left atrium; p = proximal; Stim = stimulus marker.
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Figure 6 EGM Characteristics at Tachycardia Origin
(A and B) Ranges of bipolar electrogram (EGM) amplitudes and EGM durations at sites of successful ablation, stratified by response to adenosine. (C) Fraction of tachycardia cycle length (TCL) occupied by the local EGM duration (EGM width/TCL).
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Figure 7 Entrainment of Adenosine-Insensitive Focal Atrial Tachycardia From Patient #1
(A) Pacing from the early site at the ostium of the right superior pulmonary vein results in a post-pacing interval (PPI) equivalent to the tachycardia cycle length (TCL) of 510 ms. The morphology of electrograms in the coronary sinus (CS) and the P-wave are identical during entrainment pacing and tachycardia, consistent with a protected isthmus of a re-entrant circuit. (B) Electrogram at the earliest activation site is displayed at high gain, demonstrating marked fractionation with a duration of 111 ms and amplitude of 0.07 mV. ABL = ablation; d = distal; HIS = His bundle.
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Figure 8 Proposed Schema of the Differential Effects of Adenosine for Atrial Tachycardia
Properties of triggered, automatic, and re-entrant arrhythmias are summarized, as developed in this study and other sources. Adenosine-sensitive atrial tachycardia is typically focal in origin and due to triggered activity or, far less commonly, automaticity. Adenosine-insensitive atrial tachycardia is either macro–re-entrant or micro–re-entrant, depending on circuit size and the resolution of the mapping system. Entrainment with post-pacing interval (PPI) nearly equal to the atrial tachycardia cycle length (ATCL) is typical for "macro" or "micro" re-entrant tachycardias but is not specific for these mechanisms (see text for discussion). Prolonged electrogram durations, >20% of the ATCL, may be recorded at early sites in micro–re-entrant tachycardias but are not typical at the origin of triggered and automatic rhythms. Electrogram durations at sites around a macro–re-entrant circuit might vary depending on local conduction characteristics. N/A = data not available; PES = programmed electrical stimulation.
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