Available online at www.sciencedirect.com
ScienceDirect Journal of Electrocardiology xx (2015) xxx – xxx www.jecgonline.com
Torsade de pointes in a patient with complete atrioventricular block and pacemaker failure, misdiagnosed with epilepsy Si-Yu Cai, MD,⁎ Shen-Feng Ye, MD, Xiang Wu, MD, Mei-Xiang Xiang, MD, Jian-An Wang, MD Department of Cardiology, 2nd Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China
Abstract
A case of torsade de pointes (TdP) with complete atrioventricular block and pacemaker failure that was misdiagnosed as epilepsy is presented herein. An 82-year-old female with recurrent seizure-like attacks showed epileptiform discharge during an electroencephalogram recording. A long QT interval and severe hypokalemia induced runs of TdP, which was related to pacemaker lead fracture, was detected during Holter recording and accompanied with episodes of seizures. After a DDD pacemaker with a new ventricular lead was replaced, there was no recurrence of any seizure-like attacks. Bradycardia-mediated TdP associated with complete atrioventricular block should not be missed in patients with recurrent seizure-like attacks even after pacemaker implantation. © 2015 Elsevier Inc. All rights reserved.
Keywords:
Complete atrioventricular block; Pacemaker; Torsade de pointes; Seizures
Torsade de pointes (TdP) may be a significant complication of atrioventricular (AV) block associated with QT prolongation. TdP and associated long QT syndrome (LQTS) can precipitate syncope, seizures or sudden cardiac death. Patients may be misdiagnosed with a seizure disorder or epilepsy and treated with antiepileptic drug medication. We report a case initially diagnosed as having epilepsy, but Holter recording revealed runs of TdP tachycardia, connected with episode of seizure-like activities, leading to a further diagnosis of AV block associated LQTS and TdP. Case An 82-year-old woman was admitted to the emergency room after suffering several seizure-like episodes. Family members reported that she had sudden loss of consciousness accompanied by jerking of the upper left limb, paroxysm of involuntary mouth twitching and upward gazing. Her consciousness recovered spontaneously without postictal confusion, and the episode subsided within 10 seconds. The patient had no tongue biting or incontinence with the episode. The long-term electroencephalogram (EEG) recorded in the local hospital documented the presence of right frontal and central epileptiform discharges (Fig. 1). Consequently, the patient was diagnosed with partial seizure disorder and was treated with levetiracetam combined with valproate, which ⁎ Corresponding author at: Department of Cardiology, 2nd Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China. E-mail address: [email protected] http://dx.doi.org/10.1016/j.jelectrocard.2015.03.007 0022-0736/© 2015 Elsevier Inc. All rights reserved.
was later substituted by carbamazepine. The seizure-like attacks continued despite adequate doses of anticonvulsant drugs. The patient ate less and less, and suffered from nausea and fatigue. Her past medical history included a VVI pacemaker implantation due to third-degree atrioventricular (AV) block in a different hospital 13 years ago. The generator was replaced 5 years ago and she often missed her follow-up appointments. She denied history of hypertension or diabetes. There is no family history of seizures, early cardiac disease, or sudden death. When the patient arrived at the emergency department, she was awake, alert, and oriented, with no complaints of headache, chest pain, or palpitations. Her blood pressure was 108/75 mmHg, a heart rate of 65 beats per minute (bpm), and a respiratory rate of 20 breaths per minute. Her physical and neurologic examinations were unremarkable. Laboratory studies were normal, with the exception of serum potassium concentration of 3.21 mEq/L. Computed tomography of her head showed lacunar infarction. Echocardiography showed normal cardiac structure and function. Electrocardiogram (ECG) on admission showed sinus rhythm with complete AV block and ventricular paced rhythm at a rate of 65 pulses per minute (ppm) and the QT interval was 0.60 seconds (QTc 0.53 seconds) (Fig. 2). The patient was admitted to the neurology service for further evaluation of her presumed seizures. On the third day of hospitalization, an ambulatory ECG was performed, during which several episodes of seizure-like attacks were witnessed. The 24-hour Holter monitoring revealed a sinus rhythm with third-degree AV block and ventricular paced
2
S.-Y. Cai et al. / Journal of Electrocardiology xx (2015) xxx–xxx
Fig. 1. Ambulatory electroencephalogram recording with bursts of high amplitude sharp waves over the right frontal and central regions.
rhythm (Fig. 3a). Intermittent loss of ventricular capture (Fig. 3b), which resulted in a very slow junction escape rhythm at the rate of 18–30 bpm, was detected, accompanied with a prominent TU abnormality and an extremely prolonged QTU interval (QT 0.88 seconds) (Fig. 3c). A ventricular premature beat initiated runs of TdP with repeated cycles of 10–20 beats and terminated spontaneously, with the longest lasting 10.4 seconds (Fig. 3d), coinciding with the symptomatology. Blood samples showed severe hypokalemia (2.52 mEq/L) and normal serum magnesium level (0.83 mEq/L). She was immediately treated with parenteral magnesium sulfate and potassium chloride. Battery depletion, lead fracture, or dislodgment resulting in intermittent pacemaker failure was suspected. The interrogation of the device revealed that the battery status was within normal ranges (voltage 2.78 V, impedance 474 Ω). A ventricular pacing threshold test was performed showing the right ventricular capture threshold of 2.65 V at 0.4 milliseconds. The ventricular pacing lead impedance was 419 Ω. A chest radiograph revealed fracture and insulation breaks at the angulation of the lead (Fig. 4). A detailed real-time fluoroscopy along the course of the lead further confirmed
the abnormality. On the next day, a pacemaker replacement was performed and a DDD generator (Medtronic RELIA RED01, USA) with a new ventricular lead (Medtronic 5076-58 cm, USA) was implanted (Fig. 5). After 2 days of potassium supplementation, the serum potassium level rose to 4.13 mEq/L. The patient was discharged the following day and the ECG showed VAT mode with a shortened QT interval of 0.48 seconds. No symptoms were noted by the patient at the follow-up evaluation despite that she had discontinued antiepileptic drugs since her discharge.
Discussion In the case reported herein, epileptic seizure was considered first based on the patient’s presenting symptoms. However, although the patient showed epileptiform discharge during ambulatory EEG, no symptoms had improved after anticonvulsant therapy. Holter recording documented episodes of TdP tachycardia leading to seizure-like attacks. The interrogation of pacemaker and the chest X ray indicated lead angulation and insulation breaks, which are commonly
Fig. 2. Electrocardiogram obtained during initial evaluation. Note the complete atrioventricular block, ventricular paced rhythm and prolonged QT interval of 0.60 seconds (QTC 0.53 seconds).
S.-Y. Cai et al. / Journal of Electrocardiology xx (2015) xxx–xxx
3
Fig. 3. Ambulatory 24-hour ECG recording (MV5 lead). (a) Sinus rhythm with complete atrioventricular block, ventricular paced rhythm at 65 ppm, QT interval of 0.48 seconds. (b) Sinus rhythm with complete atrioventricular block, the pacemaker spikes consistently failed to capture the ventricle, and no escape rhythm appeared. (c) The spikes still failed to capture the ventricle, but showing very slow junction escape rhythm at 18 bpm, markedly inverted, wide TU wave, and QT interval of 0.88 seconds (QTC 0.50 seconds). (d) Continuous recording (MV5 and MV1) showing torsade de pointes (TdP) ventricular tachycardia at a rate of about 250 bpm, which was preceded by a premature ventricular contraction (PVC) and self-terminated after 10.4 seconds. It was characterized by irregular wide QRS tachycardia with undulating QRS axis and changing QRS configuration, during which the patient underwent a seizure-like attack. (e) 60 seconds compacted 2-lead Holter tracing showing episodes of TdP tachycardia preceded by the typical short-long-short initiating ventricular sequence in a bigeminal pattern. PVC (first asterisk) followed by a long compensatory pause. Then an escape beat (second asterisk) was followed by a short interval and PVC (third asterisk) which initiated the tachydysrhythmia.
manifested by reduced lead impedance and elevated pacing threshold. But, in this case normal lead impedances could not rule out this problem and the manifestations of lead failure may be intermittent initially. Since there were no episodes
of seizure-like attacks after the implantation of a new ventricular lead and the withdrawal of anticonvulsant agents, we can exclude epileptiform discharge due to epileptic seizure, confirming that the seizure-like activity was
4
S.-Y. Cai et al. / Journal of Electrocardiology xx (2015) xxx–xxx
Fig. 4. Chest radiograph revealed angulation and fracture of the ventricular electrode (arrow indicates the lead abnormality).
arrhythmia-related. The lead insulation breaks resulted in increased pacing threshold, intermittent pacing failure and recurrence of complete AV block, which in combination with hypokalemia induced LQTS and TdP. Though some drugs may cause TdP, it seems that antiepileptic drugs the patient took did not contribute to significant QT interval prolongation. Therefore, we could exclude the presence of drug mediated TdP. TdP is a distinct form of typical ventricular tachycardia that was initially described in detail by Dessertenne [1]. It is characterized by short bursts of ventricular tachycardia, during which the QRS axis undulates over runs of several beats with a complete twisting of the points around an isoelectric line. TdP occurs in settings of prolonged cardiac repolarization known as LQTS. Prolonged myocardial
Fig. 5. A DDD pacemaker was implanted in the other side and the fractured lead was left inside the patient.
repolarization facilitates early afterdepolarizations, which initiates the onset of TdP. It also increases transmural dispersion of repolarization and induces functional re-entry, which is responsible for the maintenance of TdP. The acquired LQTS has been reported to occur in association with AV block and bradycardia, which increases the risk of TdP, especially in patients with underlying conditions such as hypokalemia. Bradyarrhythmias caused by high-grade AV block are common. However, AV block is infrequently associated with QT interval prolongation and TdP. Onset of TdP has been described in 5%–30% of patients with complete AV block [2]. Schwartz and Hallinger firstly pointed out the importance of TdP as a cause of syncope in patients with complete AV block [3]. In these patients, complete AV block might provide the unstable circumstances which, in turn, increase the transmural dispersion of repolarization and facilitate the development of extrasystoles, thus playing a major role in producing TdP. Although the pacemaker had been implanted for 13 years, our patient with complete AV block developed TdP due to intermittent pacemaker failure. Similar cases with AV block after pacemaker implantation have been reported. Palanca et al. described episodes of syncope due to TdP in 3 patients with complete AV block after a single-lead VDD pacemaker implantation [4]. An intermittent atrial sensing malfunction led to bradycardia and sudden RR-interval oscillations, which acted as a trigger for the initiation of TdP. In our case, the rhythm changed from VVI mode to slow escape rhythm during intermittent pacing failure, as well as premature ventricular contraction that induced short-long-short ventricular sequences. These occurrences may have combined to result in RR interval irregularity, subsequently reduced the repolarization reserve and initiated TdP. In complete AV block when the escape rhythm is slow, the more irregular the RR interval, the greater the range of refractory periods and action potential duration results, which increase the possibility for the generation of reentrant TdP arrhythmias. It is still unclear why obviously prolonged repolarization occurs only in some patients with bradycardia. Kurita et al. compared patients with complete AV block with a history of TdP to those without it, and observed that patients with TdP had abnormally prolonged QT intervals before pacemaker implantation [5]. Patients with complete AV block who developed TdP had a bradycardia-sensitive repolarization abnormality, which may be genetically predisposed. Chevalier et al. identified 4 mutations on genes encoding potassium channels (HERG) in 29 patients with complete AV block and acquired LQTS, which were not found among patients with AV block and a QT interval b 600 ms or in healthy volunteers [6]. Oka et al. revealed different heterozygous mutations in 4 of 14 AV block-related TdP cases on genetic analysis and showed loss of function associated with decreased current densities on slowly or rapidly activating delayed rectifier potassium current (IKs or IKr), which were similar to those in congenital LQTS [7]. AV block-related TdP might share a similar genetic background with congenital LQTS. Mutations on cardiac ion channel genes could be partially causative in both cases. Although gene analysis had not been performed,
S.-Y. Cai et al. / Journal of Electrocardiology xx (2015) xxx–xxx
we could not exclude that our patient had latent congenital LQTS and reduced repolarization reserve, which might be unmasked in the setting of AV block and hypokalemia, manifested as QT interval prolongation and TdP. It has been 30 years since the first case report of LQTS misdiagnosed as epilepsy was published [8]. Seizures are one of the most common symptomatic triad stemming from TdP. Many patients manifest abnormal movements of the limbs and loss of consciousness, and the differential diagnosis between syncope and epilepsy is not always easy, particularly when the syncope is associated with seizures. It is estimated that as many as 20%–30% of epileptics may have been misdiagnosed. The consequences of an incorrect diagnosis of epilepsy are severe, including unnecessary use of anticonvulsant drugs and their adverse effects and the psychological burden of this diagnosis. Misdiagnosis is not uncommon as EEG changes appear after abnormal cardiovascular events. Our case had documented EEG evidence of epileptiform activity, which increased the difficulty of diagnosis. Prolonged cerebral hypoperfusion secondary to cardiac dysrhythmia can manifest as syncope, sometimes with seizures. It is reasonable to assume that such circulatory impairment can result in a localized ischemic lesion and subsequently turn into an epileptic focus, which may be related to epileptiform discharges seen on EEGs, as in our case. Simultaneous ECG and EEG recordings may provide accurate correlation of symptoms with cardiac rhythm and brain waves, and may be helpful in the pathogenic diagnosis of seizures. In conclusion, the case report emphasizes the importance of a detailed and comprehensive examination to the differential diagnosis of seizures. Judgment based solely on an EEG, which was interpreted as epileptiform, contributed to being misdiagnosed as epilepsy. When an implanted pacemaker system fails,
5
seizures secondary to bradycardia may recur and mimic epilepsy. Such a clinical sequence, in our 82-year-old patient, led to anti-epileptic drug therapy before the correct diagnosis was made from Holter recordings which demonstrated episodes of TdP. Bradycardia-mediated TdP associated with complete AV block should not be missed in patients with recurrent episodes of seizure-like attacks even after pacemaker implantation. References [1] Dessertenne F. La tachycardia ventriculaire a deux foyers opposes variable. Arch Mal Coeur Vaiss 1966;59(2):263–72. [2] Guize L, Iliou MC, Bayet G, Lavegne T, Le Heuzey JY. Les torsades de pointes. Arch Mal Coeur Vaiss 1993;86(5 Suppl):769–76. [3] Schwartz SP, Hallinger LN. Transient ventricular fibrillation. VI. Observation on peripheral arterial pulse pressures in the course of transient ventricular fibrillation during established auriculoventricular dissociation. Am Heart J 1954;48(3):390–404. [4] Palanca V, Navarro A, Jiménez J, Quesada A, Morell S, Roda J. Intermittent atrial undersensing in single-lead VDD pacemakers in patients with bradycardia-sensitive repolarization: a possible mechanism for ventricular arrhythmia. Rev Esp Cardiol 2010;63(2):229–32. [5] Kurita T, Ohe T, Marui N, Aihara N, Takaki H, Kamakura S, et al. Bradycardia-induced abnormal QT prolongation in patients with complete atrioventricular block with torsades de pointes. Am J Cardiol 1992;69(6):628–33. [6] Chevalier P, Bellocq C, Millat G, Piqueras E, Potet F, Schott JJ, et al. Torsades de pointes complicating atrioventricular block: evidence for a genetic predisposition. Heart Rhythm 2007;4(2):170–4. [7] Oka Y, Itoh H, Ding WG, Shimizu W, Makiyama T, Ohno S, et al. Atrioventricular block-induced torsades de pointes with clinical and molecular backgrounds similar to congenital long QT syndrome. Circ J 2010;74(12):2562–71. [8] Ballardie FW, Murphy RP, Davis J. Epilepsy: a presentation of the RomanoWard syndrome. Br Med J (Clin Res Ed) 1983;287(6396):896–7.
ScienceDirect Journal of Electrocardiology xx (2015) xxx – xxx www.jecgonline.com
Torsade de pointes in a patient with complete atrioventricular block and pacemaker failure, misdiagnosed with epilepsy Si-Yu Cai, MD,⁎ Shen-Feng Ye, MD, Xiang Wu, MD, Mei-Xiang Xiang, MD, Jian-An Wang, MD Department of Cardiology, 2nd Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China
Abstract
A case of torsade de pointes (TdP) with complete atrioventricular block and pacemaker failure that was misdiagnosed as epilepsy is presented herein. An 82-year-old female with recurrent seizure-like attacks showed epileptiform discharge during an electroencephalogram recording. A long QT interval and severe hypokalemia induced runs of TdP, which was related to pacemaker lead fracture, was detected during Holter recording and accompanied with episodes of seizures. After a DDD pacemaker with a new ventricular lead was replaced, there was no recurrence of any seizure-like attacks. Bradycardia-mediated TdP associated with complete atrioventricular block should not be missed in patients with recurrent seizure-like attacks even after pacemaker implantation. © 2015 Elsevier Inc. All rights reserved.
Keywords:
Complete atrioventricular block; Pacemaker; Torsade de pointes; Seizures
Torsade de pointes (TdP) may be a significant complication of atrioventricular (AV) block associated with QT prolongation. TdP and associated long QT syndrome (LQTS) can precipitate syncope, seizures or sudden cardiac death. Patients may be misdiagnosed with a seizure disorder or epilepsy and treated with antiepileptic drug medication. We report a case initially diagnosed as having epilepsy, but Holter recording revealed runs of TdP tachycardia, connected with episode of seizure-like activities, leading to a further diagnosis of AV block associated LQTS and TdP. Case An 82-year-old woman was admitted to the emergency room after suffering several seizure-like episodes. Family members reported that she had sudden loss of consciousness accompanied by jerking of the upper left limb, paroxysm of involuntary mouth twitching and upward gazing. Her consciousness recovered spontaneously without postictal confusion, and the episode subsided within 10 seconds. The patient had no tongue biting or incontinence with the episode. The long-term electroencephalogram (EEG) recorded in the local hospital documented the presence of right frontal and central epileptiform discharges (Fig. 1). Consequently, the patient was diagnosed with partial seizure disorder and was treated with levetiracetam combined with valproate, which ⁎ Corresponding author at: Department of Cardiology, 2nd Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China. E-mail address: [email protected] http://dx.doi.org/10.1016/j.jelectrocard.2015.03.007 0022-0736/© 2015 Elsevier Inc. All rights reserved.
was later substituted by carbamazepine. The seizure-like attacks continued despite adequate doses of anticonvulsant drugs. The patient ate less and less, and suffered from nausea and fatigue. Her past medical history included a VVI pacemaker implantation due to third-degree atrioventricular (AV) block in a different hospital 13 years ago. The generator was replaced 5 years ago and she often missed her follow-up appointments. She denied history of hypertension or diabetes. There is no family history of seizures, early cardiac disease, or sudden death. When the patient arrived at the emergency department, she was awake, alert, and oriented, with no complaints of headache, chest pain, or palpitations. Her blood pressure was 108/75 mmHg, a heart rate of 65 beats per minute (bpm), and a respiratory rate of 20 breaths per minute. Her physical and neurologic examinations were unremarkable. Laboratory studies were normal, with the exception of serum potassium concentration of 3.21 mEq/L. Computed tomography of her head showed lacunar infarction. Echocardiography showed normal cardiac structure and function. Electrocardiogram (ECG) on admission showed sinus rhythm with complete AV block and ventricular paced rhythm at a rate of 65 pulses per minute (ppm) and the QT interval was 0.60 seconds (QTc 0.53 seconds) (Fig. 2). The patient was admitted to the neurology service for further evaluation of her presumed seizures. On the third day of hospitalization, an ambulatory ECG was performed, during which several episodes of seizure-like attacks were witnessed. The 24-hour Holter monitoring revealed a sinus rhythm with third-degree AV block and ventricular paced
2
S.-Y. Cai et al. / Journal of Electrocardiology xx (2015) xxx–xxx
Fig. 1. Ambulatory electroencephalogram recording with bursts of high amplitude sharp waves over the right frontal and central regions.
rhythm (Fig. 3a). Intermittent loss of ventricular capture (Fig. 3b), which resulted in a very slow junction escape rhythm at the rate of 18–30 bpm, was detected, accompanied with a prominent TU abnormality and an extremely prolonged QTU interval (QT 0.88 seconds) (Fig. 3c). A ventricular premature beat initiated runs of TdP with repeated cycles of 10–20 beats and terminated spontaneously, with the longest lasting 10.4 seconds (Fig. 3d), coinciding with the symptomatology. Blood samples showed severe hypokalemia (2.52 mEq/L) and normal serum magnesium level (0.83 mEq/L). She was immediately treated with parenteral magnesium sulfate and potassium chloride. Battery depletion, lead fracture, or dislodgment resulting in intermittent pacemaker failure was suspected. The interrogation of the device revealed that the battery status was within normal ranges (voltage 2.78 V, impedance 474 Ω). A ventricular pacing threshold test was performed showing the right ventricular capture threshold of 2.65 V at 0.4 milliseconds. The ventricular pacing lead impedance was 419 Ω. A chest radiograph revealed fracture and insulation breaks at the angulation of the lead (Fig. 4). A detailed real-time fluoroscopy along the course of the lead further confirmed
the abnormality. On the next day, a pacemaker replacement was performed and a DDD generator (Medtronic RELIA RED01, USA) with a new ventricular lead (Medtronic 5076-58 cm, USA) was implanted (Fig. 5). After 2 days of potassium supplementation, the serum potassium level rose to 4.13 mEq/L. The patient was discharged the following day and the ECG showed VAT mode with a shortened QT interval of 0.48 seconds. No symptoms were noted by the patient at the follow-up evaluation despite that she had discontinued antiepileptic drugs since her discharge.
Discussion In the case reported herein, epileptic seizure was considered first based on the patient’s presenting symptoms. However, although the patient showed epileptiform discharge during ambulatory EEG, no symptoms had improved after anticonvulsant therapy. Holter recording documented episodes of TdP tachycardia leading to seizure-like attacks. The interrogation of pacemaker and the chest X ray indicated lead angulation and insulation breaks, which are commonly
Fig. 2. Electrocardiogram obtained during initial evaluation. Note the complete atrioventricular block, ventricular paced rhythm and prolonged QT interval of 0.60 seconds (QTC 0.53 seconds).
S.-Y. Cai et al. / Journal of Electrocardiology xx (2015) xxx–xxx
3
Fig. 3. Ambulatory 24-hour ECG recording (MV5 lead). (a) Sinus rhythm with complete atrioventricular block, ventricular paced rhythm at 65 ppm, QT interval of 0.48 seconds. (b) Sinus rhythm with complete atrioventricular block, the pacemaker spikes consistently failed to capture the ventricle, and no escape rhythm appeared. (c) The spikes still failed to capture the ventricle, but showing very slow junction escape rhythm at 18 bpm, markedly inverted, wide TU wave, and QT interval of 0.88 seconds (QTC 0.50 seconds). (d) Continuous recording (MV5 and MV1) showing torsade de pointes (TdP) ventricular tachycardia at a rate of about 250 bpm, which was preceded by a premature ventricular contraction (PVC) and self-terminated after 10.4 seconds. It was characterized by irregular wide QRS tachycardia with undulating QRS axis and changing QRS configuration, during which the patient underwent a seizure-like attack. (e) 60 seconds compacted 2-lead Holter tracing showing episodes of TdP tachycardia preceded by the typical short-long-short initiating ventricular sequence in a bigeminal pattern. PVC (first asterisk) followed by a long compensatory pause. Then an escape beat (second asterisk) was followed by a short interval and PVC (third asterisk) which initiated the tachydysrhythmia.
manifested by reduced lead impedance and elevated pacing threshold. But, in this case normal lead impedances could not rule out this problem and the manifestations of lead failure may be intermittent initially. Since there were no episodes
of seizure-like attacks after the implantation of a new ventricular lead and the withdrawal of anticonvulsant agents, we can exclude epileptiform discharge due to epileptic seizure, confirming that the seizure-like activity was
4
S.-Y. Cai et al. / Journal of Electrocardiology xx (2015) xxx–xxx
Fig. 4. Chest radiograph revealed angulation and fracture of the ventricular electrode (arrow indicates the lead abnormality).
arrhythmia-related. The lead insulation breaks resulted in increased pacing threshold, intermittent pacing failure and recurrence of complete AV block, which in combination with hypokalemia induced LQTS and TdP. Though some drugs may cause TdP, it seems that antiepileptic drugs the patient took did not contribute to significant QT interval prolongation. Therefore, we could exclude the presence of drug mediated TdP. TdP is a distinct form of typical ventricular tachycardia that was initially described in detail by Dessertenne [1]. It is characterized by short bursts of ventricular tachycardia, during which the QRS axis undulates over runs of several beats with a complete twisting of the points around an isoelectric line. TdP occurs in settings of prolonged cardiac repolarization known as LQTS. Prolonged myocardial
Fig. 5. A DDD pacemaker was implanted in the other side and the fractured lead was left inside the patient.
repolarization facilitates early afterdepolarizations, which initiates the onset of TdP. It also increases transmural dispersion of repolarization and induces functional re-entry, which is responsible for the maintenance of TdP. The acquired LQTS has been reported to occur in association with AV block and bradycardia, which increases the risk of TdP, especially in patients with underlying conditions such as hypokalemia. Bradyarrhythmias caused by high-grade AV block are common. However, AV block is infrequently associated with QT interval prolongation and TdP. Onset of TdP has been described in 5%–30% of patients with complete AV block [2]. Schwartz and Hallinger firstly pointed out the importance of TdP as a cause of syncope in patients with complete AV block [3]. In these patients, complete AV block might provide the unstable circumstances which, in turn, increase the transmural dispersion of repolarization and facilitate the development of extrasystoles, thus playing a major role in producing TdP. Although the pacemaker had been implanted for 13 years, our patient with complete AV block developed TdP due to intermittent pacemaker failure. Similar cases with AV block after pacemaker implantation have been reported. Palanca et al. described episodes of syncope due to TdP in 3 patients with complete AV block after a single-lead VDD pacemaker implantation [4]. An intermittent atrial sensing malfunction led to bradycardia and sudden RR-interval oscillations, which acted as a trigger for the initiation of TdP. In our case, the rhythm changed from VVI mode to slow escape rhythm during intermittent pacing failure, as well as premature ventricular contraction that induced short-long-short ventricular sequences. These occurrences may have combined to result in RR interval irregularity, subsequently reduced the repolarization reserve and initiated TdP. In complete AV block when the escape rhythm is slow, the more irregular the RR interval, the greater the range of refractory periods and action potential duration results, which increase the possibility for the generation of reentrant TdP arrhythmias. It is still unclear why obviously prolonged repolarization occurs only in some patients with bradycardia. Kurita et al. compared patients with complete AV block with a history of TdP to those without it, and observed that patients with TdP had abnormally prolonged QT intervals before pacemaker implantation [5]. Patients with complete AV block who developed TdP had a bradycardia-sensitive repolarization abnormality, which may be genetically predisposed. Chevalier et al. identified 4 mutations on genes encoding potassium channels (HERG) in 29 patients with complete AV block and acquired LQTS, which were not found among patients with AV block and a QT interval b 600 ms or in healthy volunteers [6]. Oka et al. revealed different heterozygous mutations in 4 of 14 AV block-related TdP cases on genetic analysis and showed loss of function associated with decreased current densities on slowly or rapidly activating delayed rectifier potassium current (IKs or IKr), which were similar to those in congenital LQTS [7]. AV block-related TdP might share a similar genetic background with congenital LQTS. Mutations on cardiac ion channel genes could be partially causative in both cases. Although gene analysis had not been performed,
S.-Y. Cai et al. / Journal of Electrocardiology xx (2015) xxx–xxx
we could not exclude that our patient had latent congenital LQTS and reduced repolarization reserve, which might be unmasked in the setting of AV block and hypokalemia, manifested as QT interval prolongation and TdP. It has been 30 years since the first case report of LQTS misdiagnosed as epilepsy was published [8]. Seizures are one of the most common symptomatic triad stemming from TdP. Many patients manifest abnormal movements of the limbs and loss of consciousness, and the differential diagnosis between syncope and epilepsy is not always easy, particularly when the syncope is associated with seizures. It is estimated that as many as 20%–30% of epileptics may have been misdiagnosed. The consequences of an incorrect diagnosis of epilepsy are severe, including unnecessary use of anticonvulsant drugs and their adverse effects and the psychological burden of this diagnosis. Misdiagnosis is not uncommon as EEG changes appear after abnormal cardiovascular events. Our case had documented EEG evidence of epileptiform activity, which increased the difficulty of diagnosis. Prolonged cerebral hypoperfusion secondary to cardiac dysrhythmia can manifest as syncope, sometimes with seizures. It is reasonable to assume that such circulatory impairment can result in a localized ischemic lesion and subsequently turn into an epileptic focus, which may be related to epileptiform discharges seen on EEGs, as in our case. Simultaneous ECG and EEG recordings may provide accurate correlation of symptoms with cardiac rhythm and brain waves, and may be helpful in the pathogenic diagnosis of seizures. In conclusion, the case report emphasizes the importance of a detailed and comprehensive examination to the differential diagnosis of seizures. Judgment based solely on an EEG, which was interpreted as epileptiform, contributed to being misdiagnosed as epilepsy. When an implanted pacemaker system fails,
5
seizures secondary to bradycardia may recur and mimic epilepsy. Such a clinical sequence, in our 82-year-old patient, led to anti-epileptic drug therapy before the correct diagnosis was made from Holter recordings which demonstrated episodes of TdP. Bradycardia-mediated TdP associated with complete AV block should not be missed in patients with recurrent episodes of seizure-like attacks even after pacemaker implantation. References [1] Dessertenne F. La tachycardia ventriculaire a deux foyers opposes variable. Arch Mal Coeur Vaiss 1966;59(2):263–72. [2] Guize L, Iliou MC, Bayet G, Lavegne T, Le Heuzey JY. Les torsades de pointes. Arch Mal Coeur Vaiss 1993;86(5 Suppl):769–76. [3] Schwartz SP, Hallinger LN. Transient ventricular fibrillation. VI. Observation on peripheral arterial pulse pressures in the course of transient ventricular fibrillation during established auriculoventricular dissociation. Am Heart J 1954;48(3):390–404. [4] Palanca V, Navarro A, Jiménez J, Quesada A, Morell S, Roda J. Intermittent atrial undersensing in single-lead VDD pacemakers in patients with bradycardia-sensitive repolarization: a possible mechanism for ventricular arrhythmia. Rev Esp Cardiol 2010;63(2):229–32. [5] Kurita T, Ohe T, Marui N, Aihara N, Takaki H, Kamakura S, et al. Bradycardia-induced abnormal QT prolongation in patients with complete atrioventricular block with torsades de pointes. Am J Cardiol 1992;69(6):628–33. [6] Chevalier P, Bellocq C, Millat G, Piqueras E, Potet F, Schott JJ, et al. Torsades de pointes complicating atrioventricular block: evidence for a genetic predisposition. Heart Rhythm 2007;4(2):170–4. [7] Oka Y, Itoh H, Ding WG, Shimizu W, Makiyama T, Ohno S, et al. Atrioventricular block-induced torsades de pointes with clinical and molecular backgrounds similar to congenital long QT syndrome. Circ J 2010;74(12):2562–71. [8] Ballardie FW, Murphy RP, Davis J. Epilepsy: a presentation of the RomanoWard syndrome. Br Med J (Clin Res Ed) 1983;287(6396):896–7.
