Noncontact Mapping and Radiofrequency Catheter Ablation of Fast and Hemodynamically Unstable Ventricular Tachycardia After Surgical Repair of Tetralogy of Fallot
Thomas Kriebel, MD*,*,
J. Philip Saul, MD, FACC ,
Heike Schneider, MD*,
Matthias Sigler, MD* and
Thomas Paul, MD, FACC*
* Department of Pediatric Cardiology and Intensive Care Medicine, Georg-August-University Göttingen, Göttingen, Germany
The Children's Heart Program, Medical University of South Carolina, Charleston, South Carolina
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Figure 1 Position of the Multielectrode Balloon Array
Noncontact mapping of ventricular tachycardia in an 18-year-old boy (Patient #2) after surgical repair of tetralogy of Fallot (left: 30° right anterior oblique; right: 60° left anterior oblique). The multielectrode balloon array of the noncontact mapping system (MEA) has been inflated in the right ventricular outflow tract; the steerable mapping and ablation catheter (Map) is positioned at the anterior right ventricular free wall supported by a long precurved sheath. Additional catheters have been placed at the His bundle position (His) and in the coronary sinus (CS).
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Figure 2 Dynamic Substrate Map
Dynamic substrate map (DSM) of the right ventricle (patient as in Fig. 1) during sinus rhythm; geometry of the right ventricle has been reconstructed (30° right anterior oblique view). The scale on the left side shows the ratio of the peak negative voltage through the cardiac cycle. Negative voltage is displayed on the endocardial surface with white illustrating low-peak negative voltage (<25% of the largest unipolar deflection) and purple the most negative peak voltage (>57.5%). The zone between 25% and 57.5% is displayed in intermediate colors. Two areas of low-peak negative voltage (<35%) can be identified between the right anterior wall and the right ventricular outflow tract and between the tricuspid valve annulus and the right ventricular apex. A critical channel of electrical conduction can be suspected between the 2 low-voltage areas (arrows). Aneurysm = right ventricular outflow tract aneurysm; anterior = anterior right ventricular free wall; lateral = right ventricular lateral wall; RVA/Apex = right ventricular apex; TV6 = tricuspid valve annulus at 6 o'clock position; 6 to 10 = localization of virtual catheter electrograms.
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Figure 3 Color-Coded Isopotential Maps of Spontaneous Rhythm
(A to F) The presumed areas of low voltage identified by dynamic substrate map have been encircled (patient, view, and labels as in Fig. 2). Right ventricular activation is displayed in colors on the isoelectric (purple) endocardial surface. The red tracking virtual (yellow arrow in D) reflects the peak negative voltage. Black arrows reflect the propagation pattern of the endocardial activation. Right ventricular depolarization runs from the superior-basal aspect of the right ventricle (A) in a superior and inferior direction, with block of conduction along the presumed areas of low voltage at the anterior aspect of the anterior right ventricular wall (B and C), moves further posteriorly around the right ventricle outflow tract (D) to the septum, and finally reaches again the anterior right ventricle basal wall (E and F). Abbreviations as in Figure 2.
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Figure 4 Ventricular Tachycardia
Sustained ventricular tachycardia #1 with a cycle length of 210 ms (patient as in Figs. 1 to 3); inferior axis and left bundle branch block pattern are evident.
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Figure 5 Color-Coded Isopotential Maps of VT
(A to F) Color-coded isopotential maps of ventricular tachycardia (VT) (patient, view, labels, and arrows as in Figs. 2 and 3); right ventricular depolarization runs from the superior-basal aspect (A) in an inferior and leftward direction. In contrast to basic rhythm, conduction travels through the suspected critical channel and previous area of conduction block toward the anterior right ventricular wall (B). Subsequently, it spreads inferiorly toward the right ventricular apex (C), where it turns around the septum (D) and around the outflow tract (E) and finally returns to the superior-basal aspect of the right ventricle, closing the macro–re-entrant circuit within the right ventricle (F). A second VT could be induced in this patient running in the opposite direction as VT #1. The presumed critical channel as identified by dynamic substrate map at the anterior right ventricle wall was shared by both induced tachycardias. Accordingly, radiofrequency current was delivered to that area in a point-by-point mode perpendicular to the spread of activation. Abbreviations as in Figure 2.
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Figure 6 Color-Coded Isopotential Maps During Pacing Along RF Lesion Line
Superior (top) and inferior (bottom) pacing to the line of radiofrequency (RF) applications (brown points; patient, view, labels, and arrows as in Figs. 2 and 3) showed complete conduction block along the induced RF lesion line. Abbreviations as in Figure 2.
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