Complex Congenital Heart Disease With Brady-Tachy Syndrome and Antitachycardia Pacing

Case Synopsis

This case involves a 33-year-old woman with complex congenital heart disease consisting of heterotaxy with a single systemic right ventricle, pulmonary artery atresia, and an interrupted inferior vena cava (IVC) with hemiazygous continuation to a persistent left superior vena cava (SVC) ( Fig. 12.1 ). She is status postpulmonary artery banding, creation of bilateral bidirectional cavopulmonary anastomoses (Kawashima procedure), creation of a lateral tunnel Fontan, right atrial plication, and tricuspid valve repair. She presented to the emergency room multiple times for recurrent episodes of tachycardia ( Fig. 12.2 EKG). She was started on amiodarone but continued to have recurrent episodes. She then had an electrophysiologic study where three distinct atrial flutters and a focal atrial tachycardia were induced ( Fig. 12.3 EGM). Subsequently, she underwent a biatrial maze procedure and implantation of a dual chamber antitachycardia pacemaker (Medtronic EnRhythm model P1501DR) with epicardial lead placement and an abdominal generator ( Fig. 12.4 ); however, the initial generator was faulty and required replacement.

During normal operation, the pacemaker delivers ATP if the atrial rate is above the atrial detection rate. However, the device also assesses the atrioventricular (AV) relationship and can only deliver ATP if the atrial rate is faster than the ventricular rate. Therefore ATP would not be delivered for atrial arrhythmias with a 1:1 AV relationship. Because of this software limitation, the pacemaker was loaded with custom software from Medtronic (TPARx) under compassionate use allowing patient-activated ATP. At the onset of symptoms, the patient presses a button on a wireless transmitter that starts a timer (typically 30 min). During this period, the pacemaker suspends the AV relationship criteria and delivers ATP for atrial rhythms above the atrial detection limit. The pacemaker returns to normal operation once the atrial arrhythmia ends or the timer expires. Placing a magnet over the device will also stop delivery of therapy by TPARx.

Following pacemaker implantation, atrial arrhythmias with a 1:1 AV relationship were documented during pacemaker interrogation ( Fig. 12.5 ). The pacemaker did not initially deliver ATP after patient activation because the heart rates were below the atrial detection limit. Once the atrial detection limit was lowered, ATP was able to be delivered with patient activation. The TPARx software has successfully terminated the patient's subsequent atrial arrhythmias ( Figs. 12.6 and 12.7 ).