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BENIGN U-WAVE MISTAKEN FOR QTc PROLONGATION
LETTERS TO THE EDITOR
BENIGN U-WAVE MISTAKEN FOR QTc PROLONGATION To the Editor: We present a case report of erroneously diagnosed QTc prolongation in a 12-year-old white male enrolled in a treatment study of fluvoxamine (Research Units on Pediatric Psychopharmacology Anxiety Study Group, 2001). We chose this case of a nonsignificant U-wave that inflated QTc measurement to demonstrate that cardiologists can also be misled during electrocardiogram (ECG) interpretation. Presenting symptoms were social anxiety with irritability, shortness of breath, tachycardia, and poor concentration. No family history of sudden death, drop attacks, or congenital deafness was elicited, but father had complete heart block. Past and present medical history were noncontributory. Pretreatment physical examination, vital signs, ECG, and laboratory tests revealed no abnormalities. After 8 weeks of treatment, no evidence of physiological anxiety was noted. A pediatric cardiologist upheld a computerized calculation of QTc = 609 msec during the week 8 safety assessment. Because the apparent QTc prolongation was unexplained, the patient was hospitalized for cardiac monitoring, the blind was broken, and fluvoxamine was discontinued. Physical examination, vital signs, and serum calcium, potassium, and magnesium levels were normal. Holter monitoring showed no QTc prolongation. Four expert cardiologists were consulted, including an electrophysiologist, who calculated QTc duration and disperTABLE 1 ECG Interpretation of Adolescent Male ECG No.a
VR
QTc (C)
QTc max (EC)
0 1 2 3 4 5
83 94 96 65 73 72
396 610 419 408 397 398
413 454 457 422 414 407
(V2) (V4) (V3) (II) (V1) (V3)
QTc Dispersion 40 23 36 17 07 15
Note: ECG = electrocardiogram; VR = ventricular rate (beats per minute); C = computer calculation; EC = pediatric electrophysiologist; QTc max = the longest QTc from among 12 leads. a 0 = pretreatment; 1 = after 8 weeks of fluvoxamine (FLVX); 2 = 6 hours after final FLVX dose; 3 = 20 hours after final FLVX dose; 4 = 44 hours after final FLVX dose; 5 = 7 days after final FLVX.
J . A M . A C A D . C H I L D A D O L E S C . P S YC H I AT RY, 4 2 : 6 , J U N E 2 0 0 3
sion in all 12 leads of serial ECG tracings (Table 1). The baseline ECG had unusual T- and U-wave morphology, and flattened T-waves and nonsignificant U-waves were evident during fluvoxamine treatment and after discontinuation. Using Bazett’s formula (1920) to correct for the heart-rate dependence of the QT interval, we found that the QTc values ranged from 407 to 457 msec on five occasions during fluvoxamine treatment, compared with the single baseline QTc measurement of 413 msec. While the QTc dispersion appeared highest when the QTc was longest, each value of QTc dispersion was within a safe range determined by studies of children and adults with arrhythmias (Day et al., 1990; Linker et al., 1992). Calculation of QTc duration is part of screening for congenital or acquired risk factors associated with unstable ventricular repolarization pretreatment as well as the monitoring for treatment-emergent arrhythmias (Moss, 1993). The QTc of a child or adolescent must be calculated by hand in the presence of tachycardia, bradycardia, unusual T-wave morphology, arrhythmia (including bundle branch block), and/or presence of U waves as we present in this case. Moreover, child and adolescent psychiatrists should consult a cardiologist familiar with QTc measurement when uncertain about the clinical significance of possible QTc prolongation at baseline, T- or U-wave changes, or QTc prolongation emerging during treatment with drugs that may prolong QTc. Michael J. Labellarte, M.D. John T. Walkup, M.D. Mark A. Riddle, M.D. Division of Child and Adolescent Psychiatry Johns Hopkins University School of Medicine Baltimore See related Special Section, this issue, p. 625. Bazett HC (1920), An analysis of the time-relations of electrocardiograms. Heart 7:353–370 Day CP, McComb JM, Campbell RWF (1990), QT dispersion: an indication of arrhythmia risk in patients with long QT intervals. Br Heart J 63:342 Linker NJ, Colonna P, Kekwick CA, Till J, Camm AJ, Wars DE (1992), Assessment of QT dispersion in symptomatic patients with congenital long QT syndromes. Am J Cardiol 69:634–638 Moss AJ (1993), Measurement of the QT interval and the risk associated with QTc interval prolongation: a review. Am J Cardiol 72:23B–25B Research Units on Pediatric Psychopharmacology Anxiety Study Group (2001), Fluvoxamine for the treatment of anxiety disorders in children and adolescents. N Engl J Med 344:1279–1285 DOI: 10.1097/01.CHI.0000046851.56865.82
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BENIGN U-WAVE MISTAKEN FOR QTc PROLONGATION To the Editor: We present a case report of erroneously diagnosed QTc prolongation in a 12-year-old white male enrolled in a treatment study of fluvoxamine (Research Units on Pediatric Psychopharmacology Anxiety Study Group, 2001). We chose this case of a nonsignificant U-wave that inflated QTc measurement to demonstrate that cardiologists can also be misled during electrocardiogram (ECG) interpretation. Presenting symptoms were social anxiety with irritability, shortness of breath, tachycardia, and poor concentration. No family history of sudden death, drop attacks, or congenital deafness was elicited, but father had complete heart block. Past and present medical history were noncontributory. Pretreatment physical examination, vital signs, ECG, and laboratory tests revealed no abnormalities. After 8 weeks of treatment, no evidence of physiological anxiety was noted. A pediatric cardiologist upheld a computerized calculation of QTc = 609 msec during the week 8 safety assessment. Because the apparent QTc prolongation was unexplained, the patient was hospitalized for cardiac monitoring, the blind was broken, and fluvoxamine was discontinued. Physical examination, vital signs, and serum calcium, potassium, and magnesium levels were normal. Holter monitoring showed no QTc prolongation. Four expert cardiologists were consulted, including an electrophysiologist, who calculated QTc duration and disperTABLE 1 ECG Interpretation of Adolescent Male ECG No.a
VR
QTc (C)
QTc max (EC)
0 1 2 3 4 5
83 94 96 65 73 72
396 610 419 408 397 398
413 454 457 422 414 407
(V2) (V4) (V3) (II) (V1) (V3)
QTc Dispersion 40 23 36 17 07 15
Note: ECG = electrocardiogram; VR = ventricular rate (beats per minute); C = computer calculation; EC = pediatric electrophysiologist; QTc max = the longest QTc from among 12 leads. a 0 = pretreatment; 1 = after 8 weeks of fluvoxamine (FLVX); 2 = 6 hours after final FLVX dose; 3 = 20 hours after final FLVX dose; 4 = 44 hours after final FLVX dose; 5 = 7 days after final FLVX.
J . A M . A C A D . C H I L D A D O L E S C . P S YC H I AT RY, 4 2 : 6 , J U N E 2 0 0 3
sion in all 12 leads of serial ECG tracings (Table 1). The baseline ECG had unusual T- and U-wave morphology, and flattened T-waves and nonsignificant U-waves were evident during fluvoxamine treatment and after discontinuation. Using Bazett’s formula (1920) to correct for the heart-rate dependence of the QT interval, we found that the QTc values ranged from 407 to 457 msec on five occasions during fluvoxamine treatment, compared with the single baseline QTc measurement of 413 msec. While the QTc dispersion appeared highest when the QTc was longest, each value of QTc dispersion was within a safe range determined by studies of children and adults with arrhythmias (Day et al., 1990; Linker et al., 1992). Calculation of QTc duration is part of screening for congenital or acquired risk factors associated with unstable ventricular repolarization pretreatment as well as the monitoring for treatment-emergent arrhythmias (Moss, 1993). The QTc of a child or adolescent must be calculated by hand in the presence of tachycardia, bradycardia, unusual T-wave morphology, arrhythmia (including bundle branch block), and/or presence of U waves as we present in this case. Moreover, child and adolescent psychiatrists should consult a cardiologist familiar with QTc measurement when uncertain about the clinical significance of possible QTc prolongation at baseline, T- or U-wave changes, or QTc prolongation emerging during treatment with drugs that may prolong QTc. Michael J. Labellarte, M.D. John T. Walkup, M.D. Mark A. Riddle, M.D. Division of Child and Adolescent Psychiatry Johns Hopkins University School of Medicine Baltimore See related Special Section, this issue, p. 625. Bazett HC (1920), An analysis of the time-relations of electrocardiograms. Heart 7:353–370 Day CP, McComb JM, Campbell RWF (1990), QT dispersion: an indication of arrhythmia risk in patients with long QT intervals. Br Heart J 63:342 Linker NJ, Colonna P, Kekwick CA, Till J, Camm AJ, Wars DE (1992), Assessment of QT dispersion in symptomatic patients with congenital long QT syndromes. Am J Cardiol 69:634–638 Moss AJ (1993), Measurement of the QT interval and the risk associated with QTc interval prolongation: a review. Am J Cardiol 72:23B–25B Research Units on Pediatric Psychopharmacology Anxiety Study Group (2001), Fluvoxamine for the treatment of anxiety disorders in children and adolescents. N Engl J Med 344:1279–1285 DOI: 10.1097/01.CHI.0000046851.56865.82
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