QT interval prolongation during ECG evolution in takotsubo cardiomyopathy poses a threat of torsade de pointes to predisposed patients
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- Sacha, J., Wester, A., Hordynski, G. et al. Herz (2013) 38: 790. doi:10.1007/s00059-013-3756-8
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We report the case of a female patient with congenital complete atrioventricular block who developed torsade de pointes (TdP) in the course of takotsubo cardiomyopathy. On the basis of this case, we show that the electrocardiographic evolutionary changes with QT interval prolongation (in the course of takotsubo cardiomyopathy) may be a TdP threatening period in patients with underlying predispositions. After reviewing the literature, we also present the electrocardiographic similarities between takotsubo cardiomyopathy and other acute heart diseases associated with a large amount of stunned myocardium, i.e., other stress-related cardiomyopathies (e.g., those associated with subarachnoid hemorrhage, pheochromocytoma, or severe illnesses) as well as a reperfused myocardial infarction. QT interval prolongation is a common feature in the subacute phase of these entities; however, excessive QT prolongation may be a sign of predisposition to TdP. In such instances, measures should be taken to monitor cardiac rhythm closely and to prevent or treat TdP appropriately. Taking into account the risk of TdP, it is reasonable to consider takotsubo cardiomyopathy as a potential cause of acquired long QT syndrome.
KeywordsTakotsuboStress-related cardiomyopathyQT prolongationTorsade de pointesAtrioventricular block
Bei QT-Intervall-Verlängerung im EKG-Verlauf bei Takotsubo-Kardiomyopathie droht prädisponierten Patienten eine Torsade de pointes
Berichtet wird über den Fall einer Patientin mit kongenitalem atrioventrikulärem (AV-)Block, bei der eine Torsade de pointes (TdP) im Rahmen einer Takotsubo-Kardiomyopathie auftrat. Auf der Grundlage diese Falls wird gezeigt, dass ein Elektrokardiographie(EKG)-Verlauf mit QT-Intervall-Verlängerung (im Rahmen der Takotsubo-Kardiomyopathie) eine Phase erhöhten Risikos für eine TdP bei Patienten mit entsprechender Prädisposition darstellen kann. Nach einer Übersicht über die Literatur werden auch Ähnlichkeiten im EKG zwischen Takotsubo-Kardiomyopathie und anderen akuten Herzerkrankungen beschrieben, die mit einem hohen Anteil reperfundierten, hypokinetischen Myokards („stunned myocardium“) einhergehen, z. B. andere stressbedingte Kardiomyopathien (wie bei Subarachnoidalblutung, Phäochromozytom oder schweren Erkrankungen) oder ein reperfundierter Herzinfarkt. Die QT-Intervall-Verlängerung tritt häufig in der subakuten Phase dieser Erkrankungen auf, eine ausgeprägte QT-Verlängerung kann jedoch Zeichen der Prädisposition zur TdP sein. In solchen Fällen sollten Maßnahmen zur engmaschigen Überwachung des Herzrhythmus und zur Vorbeugung oder angemessenen Behandlung einer TdP ergriffen werden. Angesichts des Risikos einer TdP sollte die Takotsubo-Kardiomyopathie als potenzielle Ursache eines erworbenen langen QT-Syndroms angesehen werden.
SchlüsselwörterTakotsuboStressbedingte KardiomyopathieQT-VerlängerungTorsade de pointesAtrikoventrikulärer Block
Takotsubo cardiomyopathy (TC) is a transient heart syndrome commonly induced by emotional or physical stress [1, 2]. It is characterized by chest pain, electrocardiographic (ECG) changes, and enzymatic myocardial release suggesting an acute myocardial infarction in patients without obstructive coronary artery lesions. Assessment of left ventricular function usually reveals preserved basal function with apical akinesis or dyskinesis (i.e., apical ballooning), which resolves within weeks after an acute event. The general prognosis in TC is considered to be favorable, although some fatal cases have been reported [3, 4, 5].
In the time course of TC, ECG evolutionary changes can be observed. These changes correspond to the ECG evolution seen in minimal myocardial infarction or in other transient left ventricular dysfunctions associated with excessive catecholamine release such as those in acute neurological disorders, pheochromocytoma, or in critically ill patients [6, 7, 8, 9, 10, 11]. The common ECG feature in the subacute phase of these entities is QT interval prolongation, which constitutes a risk factor for fatal polymorphic ventricular tachyarrhythmia, i.e., torsade de pointes (TdP) [12, 13]. In this report we describe, as far as we know, the first case of a female patient with a congenital complete atrioventricular (AV) block who developed a large QT prolongation in the subacute phase of TC resulting in TdP.
A 42-year-old woman with a congenital third-degree AV block (Fig. 1) was admitted to our department after syncope. On ECG examination, QT interval prolongation and repolarization changes were seen suggesting an acute coronary syndrome (Fig. 2a). Until then she had been asymptomatic with neither any episodes of syncope nor evidence of severe arrhythmias, and she did not require cardiac pacing. The day before presentation she had attended the funeral of her husband, who had died suddenly. Owing to the ECG changes seen on admission (Fig. 2a) and the left ventricular contraction abnormalities seen on echocardiography (i.e., hypo/akinesis of the mid and apical anterolateral segments with an ejection fraction of 45 %) as well as positive cardiac markers (troponin T: 0.166 ug/l, CK-MB mass: 4.73 ng/ml), she was referred for immediate coronary angiography. However, no obstructive lesions were found in both the left and the right coronary artery (Fig. 2b, c); but on ventriculography, contractile abnormalities were seen (Fig. 2d, e). TC was diagnosed and the patient was taken to the intensive care unit. On the next day, the QT interval was considerably prolonged and double T waves (so-called notched T waves)  appeared (Fig. 3a)—the patient was not taking any QT-prolonging drugs and electrolyte abnormalities were not detected. Subsequently, frequent ventricular premature contractions emerged, which triggered TdP requiring defibrillation (Fig. 3b). The arrhythmia recurred several times demanding xylocaine administration and endocavitary cardiac stimulation at a rate of 80 bpm to prevent TdP recurrence. On the 3rd day, the QT interval shortened and no TdP recurred (Fig. 4a)—at the same time, left ventricular contractility was found to be normal on echocardiography. To prevent lethal ventricular arrhythmias and permanent heart pacing, a dual-chamber implantable cardioverter-defibrillator (ICD) was implanted (Fig. 4b). At the 1-year follow-up, no serious event was observed and the left ventricular function remained normal.
In TC, the time course of ECG evolutionary changes can be observed. ST segment changes on admission usually resolve within 3 days; simultaneously, T waves become inverted and deepen along with QT interval prolongation. Then T waves get shallow for several days and may deepen again after approximately 2–3 weeks. As the T wave deepens, the QT interval prolongs but shortens as the T wave becomes shallow. After approximately 6 months, the ECG returns to normal in the majority of patients . A similar time course of evolutionary changes in ECG can be seen in minimal myocardial infarction after successful reperfusion [6, 15]. It was shown that deep inverted T waves may indicate abundantly stunned myocardium in the first days after myocardial infarction . The left ventricular dysfunction in TC and its dramatic resolution in a short time are also compatible with stunned myocardium. Moreover, the similar contractile abnormalities (suggesting a large amount of stunned myocardium) and time course of ECG evolutionary changes may be seen in acute left ventricular dysfunctions associated with intracranial events (e.g., subarachnoid hemorrhage), pheochromocytoma, exogenous catecholamine administration, or acute medical illness including sepsis [7, 8, 9, 10, 16]. All these instances are currently termed“stress-related cardiomyopathies” . It is postulated that the mechanism of ventricular dysfunction in these states is due to catecholamine-mediated myocardial toxicity . Interestingly, the sympathetic nervous system activity also plays a role in the pathophysiology of long QT syndromes , i.e., catecholamines can induce early afterdepolarizations and triggered activity—the arrhythmic stimuli for TdP . Indeed, TdP is relatively rare in stress cardiomyopathies and probably affects patients with underlying predispositions —our patient suffered from a congenital, complete AV block, which along with relative bradycardia are the recognized risk factors of TdP [21, 22]. However, she had not experienced syncope or any other symptoms suggesting lethal arrhythmias until her QT interval was considerably prolonged in the course of TC (Fig. 3); furthermore, TdP did not recur after the QT interval had shortened (Fig. 4). It is also worth noting that a specific feature of T waves emerged, which resembles that seen in the congenital long QT syndrome type 2, i.e., a double-T-wave appearance, also known as “notched T waves,” T-wave “humps,” or “pathologic U waves” (Fig. 3a). Such giant T-U waves may reflect early afterdepolarizations and are associated with a high risk of TdP , especially if the second component of the T wave is higher than the first one . Another risk factor of TdP is female gender, which is associated with a greater susceptibility to TdP related to a complete heart block . Thus, a number of TdP-predisposing factors could be found in our case; however, it was the ECG evolution in TC (resulting in critical QT prolongation) that finally provoked TdP. In such a context this case perfectly demonstrates the concept of“repolarization reserve” , i.e., the patient had impaired repolarization because of long-standing AV block and the additional“QT insult” in the form of TC eventually led to TdP . There is some data showing that severe ventricular arrhythmia may also occur in the early phase of TC before maximal QT interval prolongation ; however, such an early arrhythmia may be distinct from that of the subacute phase, or it could even be that TC might not be the trigger of arrhythmia, but rather the result of the stress associated with arrhythmia symptoms . Nevertheless, the problem of early versus late TdP in TC will certainly require further elucidation. It is also worth mentioning that our patient presented no chest pain associated with TC, stressing that some cases with painless TC may be overlooked.
The TC patients who suffered from TdP usually developed significantly longer QT intervals in the time course of ECG than those without TdP . Interestingly, in 8 out of 434 consecutive myocardial infarction patients who experienced TdP during the subacute phase, the QT interval was also considerably longer than in patients without TdP . Despite these similarities, significant differences of QT interval modulation in patients with TC and acute myocardial infarction have been observed, i.e., rate adaptation of ventricular repolarization (i.e., QT dynamicity) is not altered in TC, as opposed to its absence in myocardial infarction, suggesting a differential effect of autonomic nervous activity on the ventricular myocardium in these two entities . The excessive QT prolongation during the time course of ECG evolutionary changes may be a sign of some predispositions to TdP. If the QTc is prolonged more than 500 ms, measures should be taken to monitor cardiac rhythm closely and to prevent or treat TdP appropriately . Although the QT interval normalizes within several days after the TC onset, one should keep in mind that it may become prolonged for a second time after approximately 2–3 weeks , posing a threat of TdP and sudden cardiac death to the predisposed patients. Our patient underwent cardiac arrest several times during hospitalization when her QT interval was considerably prolonged, and only defibrillation could restore her heart rhythm. Considering her predisposition to severe ventricular arrhythmias and the risk of recurrent TC, as well as all other possible situations where the QT interval could be prolonged (e.g., drugs and electrolyte imbalances), we judged her risk of sudden cardiac death as being high, and therefore we implanted an ICD—the device was set for ventricular fibrillation only.
Taking into account the risk of TdP, it is reasonable to consider the subacute phase of TC as a potential cause of acquired long QT syndrome. All possible measures should be taken to prevent arrhythmia (i.e., avoidance of QT-prolonging drugs, treatment and prevention of electrolyte abnormalities) in all patients, especially in those with bradycardia, previous syncope, or those exhibiting an unusually long QT interval (i.e., QTc longer than 500 ms). T-wave morphology seems to be another predictor of TdP, particularly double T waves (“notched” T waves).
Conflict of interest
On behalf of all authors, the corresponding author states that there are no conflicts of interest.