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A Surprise Wireless Remote Transmission
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Heart Rhythm, Vol 5, No 7, July 2008
left ventricular wedge preparations to either pinacidil or the IKr agonist PD-118057,5,6 despite a major abbreviation of APD and QT interval, we failed to observe a U wave in the electrocardiogram. The end of the T wave was always coincident with the repolarization of the myocardium. The disparity between our results in canine wedge preparations and those of Wu and coworkers in Langendorff-perfused rabbit hearts may be due to species differences. However, it is noteworthy that despite the appearance of an apparent U wave after the administration of pinacidil, Wu and coworkers4 failed to observe a sustained late phase 3 early afterdepolarization or a deflection of any kind in the ventricular action potential. The relation between action potential duration and the calcium transient is known to vary among species (rabbit, guinea pig, dog).4,7,8 Whereas in rabbits and guinea pigs the duration of the calcium transient is similar to that for the action potential, in dogs the calcium transient appears to be longer than the action potential. Because the calcium transient extends beyond the end of the action potential in the dog, the hypothesis suggested by Chen and Lin would predict the appearance of a late phase 3 afterdepolarization, yet this is not observed under normal conditions. Of note, neither the dog nor the rabbit display U waves under either normal or pathophysiologic conditions. Moreover, because in the human heart the U wave typically extends 160 –230 ms beyond the end of the T wave,9 the hypothesis in question would require that the calcium transient under normal conditions extend approximately 200 ms beyond the end of the longest ventricular action potential. To our knowledge, this is not the case. We are grateful to Drs. Chen and Lin for their interesting ideas and discussion, but we feel that further studies are needed to sort out the responsible mechanisms. Rainer Schimpf, MD First Department of Medicine-Cardiology University Hospital Mannheim Mannheim, Germany Charles Antzelevitch, PhD Masonic Medical Research Laboratory Utica, New York Dariush Haghi, MD First Department of Medicine-Cardiology University Hospital Mannheim Mannheim, Germany Carla Giustetto, MD Department of Cardiology Cardinal Massaia Hospital, Asti University of Torino, Italy Alfredo Pizzuti, MD Division of Cardiology Ospedale Mauriziano Umberto I University of Torino Torino, Italy
Fiorenzo Gaita, MD Department of Cardiology Cardinal Massaia Hospital, Asti University of Torino Torino, Italy Christian Veltmann, MD Christian Wolpert, MD Martin Borggrefe, MD First Department of Medicine-Cardiology University Hospital Mannheim Mannheim, Germany
References 1.
2.
3. 4.
5.
6. 7.
8. 9.
Schimpf R, Antzelevitch C, Haghi D, et al. Electromechanical coupling in patients with the short QT syndrome: further insights into the mechanoelectrical hypothesis of the U wave. Heart Rhythm 2008;5:241–245. Ter Keurs HE, Wakayama Y, Sugai Y, et al. Role of sarcomere mechanics and Ca2⫹ overload in Ca2⫹ waves and arrhythmias in rat cardiac muscle. Ann N Y Acad Sci 2006;1080:248 –267. Burashnikov A, Antzelevitch C. Late-phase 3 EAD. A unique mechanism contributing to initiation of atrial fibrillation. PACE 2006;29:290 –295 Wu S, Hayashi H, Lin SF, et al. Action potential duration and QT interval during pinacidil infusion in isolated rabbit hearts. J Cardiovasc Electrophysiol 2005; 16:872– 878. Extramiana F, Antzelevitch C. Amplified transmural dispersion of repolarization as the basis for arrhythmogenesis in a canine ventricular-wedge model of short QT syndrome. Circulation 2004;110:3661–3666. Patel C, Antzelevitch C. Pharmacological approach to the treatment of long and short QT syndromes. Pharmacol Ther 2008;118:138 –151. Cordeiro JM, Greene L, Heilmann C, et al. Transmural heterogeneity of calcium activity and mechanical function in the canine left ventricle. Am J Physiol Heart Circ Physiol 2004;286:H1471–H1479. Laurita KR, Katra R, Wible B, et al. Transmural heterogeneity of calcium handling in canine. Circ Res 2003;92:668 – 675. Surawicz B. U wave: facts, hypotheses, misconceptions, and misnomers. J Cardiovasc Electrophysiol 1998;9:1117–1128.
A Surprise Wireless Remote Transmission A 50-year-old man with nonischemic cardiomyopathy and congestive heart failure underwent implantation of a Medtronic Concerto (C154DWK) biventricular dual chamber implantable cardioverter-defibrillator. He was enrolled in the Carelink (Medtronic Inc, Minneapolis, MN) remote monitoring system of his wireless device. In May 2008, the device reached ERI, and the patient underwent successful generator change with a new Concerto C154DWK generator. The next day, the following alert message was received via the Carelink system (Medtronic Inc, Minneapolis, MN): “Recommended Replacement Time, Lead Warning, VF Detection Off, Wireless Alert, Patient Alert.” The transmission showed that ventricular fibrillation detection was programmed off, the battery was at ERI (2.59 V), and all lead impedances were ⬎2500 ohms. The patient’s physicians were puzzled until further investigation revealed that the patient had taken his old generator home and placed it in his bedroom, where the wireless monitor had detected it. Patients should be instructed not to place their wireless explanted generators near their remote transmitters. Elizabeth S. Kaufman, MD, FHRS Alberto N. Diaz, MD From the Heart and Vascular Research Center MetroHealth Campus of Case Western Reserve University Cleveland, Ohio
Heart Rhythm, Vol 5, No 7, July 2008
left ventricular wedge preparations to either pinacidil or the IKr agonist PD-118057,5,6 despite a major abbreviation of APD and QT interval, we failed to observe a U wave in the electrocardiogram. The end of the T wave was always coincident with the repolarization of the myocardium. The disparity between our results in canine wedge preparations and those of Wu and coworkers in Langendorff-perfused rabbit hearts may be due to species differences. However, it is noteworthy that despite the appearance of an apparent U wave after the administration of pinacidil, Wu and coworkers4 failed to observe a sustained late phase 3 early afterdepolarization or a deflection of any kind in the ventricular action potential. The relation between action potential duration and the calcium transient is known to vary among species (rabbit, guinea pig, dog).4,7,8 Whereas in rabbits and guinea pigs the duration of the calcium transient is similar to that for the action potential, in dogs the calcium transient appears to be longer than the action potential. Because the calcium transient extends beyond the end of the action potential in the dog, the hypothesis suggested by Chen and Lin would predict the appearance of a late phase 3 afterdepolarization, yet this is not observed under normal conditions. Of note, neither the dog nor the rabbit display U waves under either normal or pathophysiologic conditions. Moreover, because in the human heart the U wave typically extends 160 –230 ms beyond the end of the T wave,9 the hypothesis in question would require that the calcium transient under normal conditions extend approximately 200 ms beyond the end of the longest ventricular action potential. To our knowledge, this is not the case. We are grateful to Drs. Chen and Lin for their interesting ideas and discussion, but we feel that further studies are needed to sort out the responsible mechanisms. Rainer Schimpf, MD First Department of Medicine-Cardiology University Hospital Mannheim Mannheim, Germany Charles Antzelevitch, PhD Masonic Medical Research Laboratory Utica, New York Dariush Haghi, MD First Department of Medicine-Cardiology University Hospital Mannheim Mannheim, Germany Carla Giustetto, MD Department of Cardiology Cardinal Massaia Hospital, Asti University of Torino, Italy Alfredo Pizzuti, MD Division of Cardiology Ospedale Mauriziano Umberto I University of Torino Torino, Italy
Fiorenzo Gaita, MD Department of Cardiology Cardinal Massaia Hospital, Asti University of Torino Torino, Italy Christian Veltmann, MD Christian Wolpert, MD Martin Borggrefe, MD First Department of Medicine-Cardiology University Hospital Mannheim Mannheim, Germany
References 1.
2.
3. 4.
5.
6. 7.
8. 9.
Schimpf R, Antzelevitch C, Haghi D, et al. Electromechanical coupling in patients with the short QT syndrome: further insights into the mechanoelectrical hypothesis of the U wave. Heart Rhythm 2008;5:241–245. Ter Keurs HE, Wakayama Y, Sugai Y, et al. Role of sarcomere mechanics and Ca2⫹ overload in Ca2⫹ waves and arrhythmias in rat cardiac muscle. Ann N Y Acad Sci 2006;1080:248 –267. Burashnikov A, Antzelevitch C. Late-phase 3 EAD. A unique mechanism contributing to initiation of atrial fibrillation. PACE 2006;29:290 –295 Wu S, Hayashi H, Lin SF, et al. Action potential duration and QT interval during pinacidil infusion in isolated rabbit hearts. J Cardiovasc Electrophysiol 2005; 16:872– 878. Extramiana F, Antzelevitch C. Amplified transmural dispersion of repolarization as the basis for arrhythmogenesis in a canine ventricular-wedge model of short QT syndrome. Circulation 2004;110:3661–3666. Patel C, Antzelevitch C. Pharmacological approach to the treatment of long and short QT syndromes. Pharmacol Ther 2008;118:138 –151. Cordeiro JM, Greene L, Heilmann C, et al. Transmural heterogeneity of calcium activity and mechanical function in the canine left ventricle. Am J Physiol Heart Circ Physiol 2004;286:H1471–H1479. Laurita KR, Katra R, Wible B, et al. Transmural heterogeneity of calcium handling in canine. Circ Res 2003;92:668 – 675. Surawicz B. U wave: facts, hypotheses, misconceptions, and misnomers. J Cardiovasc Electrophysiol 1998;9:1117–1128.
A Surprise Wireless Remote Transmission A 50-year-old man with nonischemic cardiomyopathy and congestive heart failure underwent implantation of a Medtronic Concerto (C154DWK) biventricular dual chamber implantable cardioverter-defibrillator. He was enrolled in the Carelink (Medtronic Inc, Minneapolis, MN) remote monitoring system of his wireless device. In May 2008, the device reached ERI, and the patient underwent successful generator change with a new Concerto C154DWK generator. The next day, the following alert message was received via the Carelink system (Medtronic Inc, Minneapolis, MN): “Recommended Replacement Time, Lead Warning, VF Detection Off, Wireless Alert, Patient Alert.” The transmission showed that ventricular fibrillation detection was programmed off, the battery was at ERI (2.59 V), and all lead impedances were ⬎2500 ohms. The patient’s physicians were puzzled until further investigation revealed that the patient had taken his old generator home and placed it in his bedroom, where the wireless monitor had detected it. Patients should be instructed not to place their wireless explanted generators near their remote transmitters. Elizabeth S. Kaufman, MD, FHRS Alberto N. Diaz, MD From the Heart and Vascular Research Center MetroHealth Campus of Case Western Reserve University Cleveland, Ohio