Macroscopic T wave alternans in long QT syndrome
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《印度儿科学杂志》
Abstract
A 6 year old girl was admitted with recurrent episodes of loss of consciousness. ECG showed prolonged QT interval and macroscopic T Wave alternans. Identification of this ECG pattern is important since it can lead to potentially lethal arrhythmias.
Keywords: Long QT syndrome; T wave alternans
How to cite this article:
Jayakrishnan MP, Krishnakumar P. Macroscopic T wave alternans in long QT syndrome. Indian J Pediatr 2006;73:539-540
How to cite this URL:
Jayakrishnan MP, Krishnakumar P. Macroscopic T wave alternans in long QT syndrome. Indian J Pediatr [serial online] 2006 [cited 2006 Jul 14];73:539-540. Available from: http://www.ijppediatricsindia.org/article.asp?issn=0019-5456;year=2006;volume=73;issue=6;spage=539;epage=540;aulast=Jayakrishnan
Long QT syndrome (LQTS) is a congenital disorder characterized by prolongation of QT interval in the electrocardiogram (ECG) and a propensity to develop ventricular arrhythmias, which may lead to syncope, cardiac arrest or sudden death. T wave alternans (TWA), defined, as a beat-to-beat variation in the amplitude or polarity of the T wave, is one of the pointers suggestive of the diagnosis of LQTS[1]. TWA may be visible to the naked eye (macroscopic TWA) or only detected by special equipments that detect minute changes in the T wave voltages not visible to the naked eye (micro volt TWA). The importance of macroscopic TWA is that, it is usually followed by dangerous arrhythmias like polymorphic ventricular tachycardia (torsade de pointes) and ventricular fibrillation.[2], [3]
There have been reports of varying clinical presentations of LQTS in Indian children.[4],[5] So far, no case of macroscopic TWA in LQTS has been reported from India. We report a case of LQTS with macroscopic TWA in the ECG.
Case Report
A 6-year-old girl, first born of nonconsanguineous parents, was admitted with history of repeated episodes of loss of consciousness. The illness started I month prior to hospitalization, when she suddenly woke up from sleep early in the morning, crying, as though following a nightmare. This was immediately followed by loss of consciousness, which lasted for about half an hour. There were three episodes of loss of consciousness, each lasting for few minutes after the initial episode.
There was no history of head trauma or drug ingestion. She did not have syncope or seizures in the past. There was no family history of syncope, seizures or sudden death.
At the time of admission, she was drowsy, with no other positive physical findings. Seizure disorder was considered as the first possibility. Her blood sugar, serum sodium, potassium, calcium and magnesium were normal. Electroencephalogram, echocardiogram and a CT scan of the brain were normal.
Electrocardiogram on the day of hospitalization revealed marked prolongation of corrected QT interval [Figure - 1]. A second ECG taken 2 hours later revealed prolonged QTc along with macroscopic T wave alternans [Figure - 2]. Her younger sister's ECG had a QTc of 0.44 seconds. Screening ECGs of her parents were normal.
Based on the symptoms and ECG findings a diagnosis of LQTS was made and the child was started on oral propranolol. On follow up she had no further episodes of loss of consciousness for the last five months.
Discussion
In the present case the ECGs taken two hours apart showed marked prolongation of the corrected QT interval. There was no cause for the recurrent episodes of loss of consciousness other than the pronged QT interval and the clinical features were suggestive of the diagnosis of long QT syndrome as per the diagnostic criteria[1]. The second ECG showed macroscopic TWA.
T wave alternans is uncommon and is often overlooked, except when it is of large amplitude as in this case. T wave alternans results when there is heterogeneity of repolarization, which means a variation in the rate of repolarization. Sometimes the myocytes repolarize synchronously and sometimes less synchronously resulting in the wave of repolarization changing from one direction to the other. Thus the repolarization swings like a pendulum from one direction to the other resulting in the T wave becoming alternately upright and inverted.[6]
Association of TWA with long QT syndrome is well documented and the presence of TWA increases the chance of developing potentially lethal arrhythmias.[7],[8] It is important that the pediatricians should be able to identify this pattern in the ECG sufficiently early so that appropriate treatment could be initiated.
References
1. Schwartz PJ, Moss AJ, Vincent GM, Crampton RS. Diagnostic criteria for the long QT syndrome. An update. Circulation 1993; 88 : 782-784.
2. El-Sherif N, Turitto G. Torsade de pointes. Curr Opin Cardiol 2003; 18 : 6-13.
3. Harris S, O'Neill M, Oliver N, Dubrey S. An unusual electrocardiographic abnormality. Postgrad Med J 2003; 79: 539-540.
4. Shanbag P, Govindakumar PT, Vaidya M, Joshi V, Shahid SK The congenital long QT syndrome. Indian J Pediatr 2002; 69: 141-144.
5. Raja Jai Sundar S, Parvathy CS, Thomas JM, Sudarsana G. Congenital long QT syndrome presenting as epilepsy. Indian Pediatr 2003; 40 : 1201-1203.
6. Shimizu W, Antzelevitch C. Cellular and ionic basis for T wave alternans under long QT conditions. Circulation 1999; 99: 1499-507.
7. Grabowski M, Karpinski G, Filipiak KJ, Opolski G. Drug induced long QT syndrome with macroscopic T wave alternans. Circulation 2004; 110:e 459-460.
8. Goldman DS, Zarebo W, Moss AJ.Malignant T wave alternans. Circulation 2000; 102: e 46-47.(Jayakrishnan MP, Krishnak)
A 6 year old girl was admitted with recurrent episodes of loss of consciousness. ECG showed prolonged QT interval and macroscopic T Wave alternans. Identification of this ECG pattern is important since it can lead to potentially lethal arrhythmias.
Keywords: Long QT syndrome; T wave alternans
How to cite this article:
Jayakrishnan MP, Krishnakumar P. Macroscopic T wave alternans in long QT syndrome. Indian J Pediatr 2006;73:539-540
How to cite this URL:
Jayakrishnan MP, Krishnakumar P. Macroscopic T wave alternans in long QT syndrome. Indian J Pediatr [serial online] 2006 [cited 2006 Jul 14];73:539-540. Available from: http://www.ijppediatricsindia.org/article.asp?issn=0019-5456;year=2006;volume=73;issue=6;spage=539;epage=540;aulast=Jayakrishnan
Long QT syndrome (LQTS) is a congenital disorder characterized by prolongation of QT interval in the electrocardiogram (ECG) and a propensity to develop ventricular arrhythmias, which may lead to syncope, cardiac arrest or sudden death. T wave alternans (TWA), defined, as a beat-to-beat variation in the amplitude or polarity of the T wave, is one of the pointers suggestive of the diagnosis of LQTS[1]. TWA may be visible to the naked eye (macroscopic TWA) or only detected by special equipments that detect minute changes in the T wave voltages not visible to the naked eye (micro volt TWA). The importance of macroscopic TWA is that, it is usually followed by dangerous arrhythmias like polymorphic ventricular tachycardia (torsade de pointes) and ventricular fibrillation.[2], [3]
There have been reports of varying clinical presentations of LQTS in Indian children.[4],[5] So far, no case of macroscopic TWA in LQTS has been reported from India. We report a case of LQTS with macroscopic TWA in the ECG.
Case Report
A 6-year-old girl, first born of nonconsanguineous parents, was admitted with history of repeated episodes of loss of consciousness. The illness started I month prior to hospitalization, when she suddenly woke up from sleep early in the morning, crying, as though following a nightmare. This was immediately followed by loss of consciousness, which lasted for about half an hour. There were three episodes of loss of consciousness, each lasting for few minutes after the initial episode.
There was no history of head trauma or drug ingestion. She did not have syncope or seizures in the past. There was no family history of syncope, seizures or sudden death.
At the time of admission, she was drowsy, with no other positive physical findings. Seizure disorder was considered as the first possibility. Her blood sugar, serum sodium, potassium, calcium and magnesium were normal. Electroencephalogram, echocardiogram and a CT scan of the brain were normal.
Electrocardiogram on the day of hospitalization revealed marked prolongation of corrected QT interval [Figure - 1]. A second ECG taken 2 hours later revealed prolonged QTc along with macroscopic T wave alternans [Figure - 2]. Her younger sister's ECG had a QTc of 0.44 seconds. Screening ECGs of her parents were normal.
Based on the symptoms and ECG findings a diagnosis of LQTS was made and the child was started on oral propranolol. On follow up she had no further episodes of loss of consciousness for the last five months.
Discussion
In the present case the ECGs taken two hours apart showed marked prolongation of the corrected QT interval. There was no cause for the recurrent episodes of loss of consciousness other than the pronged QT interval and the clinical features were suggestive of the diagnosis of long QT syndrome as per the diagnostic criteria[1]. The second ECG showed macroscopic TWA.
T wave alternans is uncommon and is often overlooked, except when it is of large amplitude as in this case. T wave alternans results when there is heterogeneity of repolarization, which means a variation in the rate of repolarization. Sometimes the myocytes repolarize synchronously and sometimes less synchronously resulting in the wave of repolarization changing from one direction to the other. Thus the repolarization swings like a pendulum from one direction to the other resulting in the T wave becoming alternately upright and inverted.[6]
Association of TWA with long QT syndrome is well documented and the presence of TWA increases the chance of developing potentially lethal arrhythmias.[7],[8] It is important that the pediatricians should be able to identify this pattern in the ECG sufficiently early so that appropriate treatment could be initiated.
References
1. Schwartz PJ, Moss AJ, Vincent GM, Crampton RS. Diagnostic criteria for the long QT syndrome. An update. Circulation 1993; 88 : 782-784.
2. El-Sherif N, Turitto G. Torsade de pointes. Curr Opin Cardiol 2003; 18 : 6-13.
3. Harris S, O'Neill M, Oliver N, Dubrey S. An unusual electrocardiographic abnormality. Postgrad Med J 2003; 79: 539-540.
4. Shanbag P, Govindakumar PT, Vaidya M, Joshi V, Shahid SK The congenital long QT syndrome. Indian J Pediatr 2002; 69: 141-144.
5. Raja Jai Sundar S, Parvathy CS, Thomas JM, Sudarsana G. Congenital long QT syndrome presenting as epilepsy. Indian Pediatr 2003; 40 : 1201-1203.
6. Shimizu W, Antzelevitch C. Cellular and ionic basis for T wave alternans under long QT conditions. Circulation 1999; 99: 1499-507.
7. Grabowski M, Karpinski G, Filipiak KJ, Opolski G. Drug induced long QT syndrome with macroscopic T wave alternans. Circulation 2004; 110:e 459-460.
8. Goldman DS, Zarebo W, Moss AJ.Malignant T wave alternans. Circulation 2000; 102: e 46-47.(Jayakrishnan MP, Krishnak)