Episodes Of Monomorphic Ventricular Tachycardia Research Articles

P105: Pre-Emptive Use of Mechanical Circulatory support in sudden cardiac death- A contrasting case series

Life-threatening ventricular tachycardia(VT) and fibrillation(VF) are the most important causes of sudden cardiac death(SCD). Patients who survive are often predisposed to recurrent VT secondary to scar tissue and require definitive ablation therapies. However given the unpredictable nature of arrhythmias, patients can degenerate into VT storm even as outpatient and become hemodynamically unstable which precludes ablation therapies. Using preemptive mechanical circulatory support in such patients as a bridge to ablation can be a game changer, especially in the event of a fresh VT. We present two contrasting cases, where preemptive use of Impella showed better outcomes in neurological status post cardiac arrest. Our patient is a 16-year-old competitive basketball player who suffered an out-of-hospital VT arrest during match practice requiring bystander CPR and multiple shocks. He was stabilized in an outside hospital and brought to us intubated, paralyzed, on multiple pressors and maintained on IV amiodarone and lidocaine. ECHO demonstrated a very large right ventricle (RV) with severe left ventricle(LV) dysfunction, ejection fraction(EF) 10-15% with basal RV diameter 6.8cm. Cardiac MRI(CMRI) showed an area of late gadolinium enhancement (LGE) of the RV-free wall near the apex. Endomyocardial biopsy, Cardiac catheterization, and CT angiogram were unremarkable. With improvement in volume status, he was weaned off all inotropes and antiarrhythmics, received an AICD, and maintained only on sotalol and lisinopril. On outpatient follow-up, repeat CMRI confirmed Arrhythmogenic RV dysplasia. Unfortunately, four months later, the patient had another episode of cardiac arrest secondary to a VT storm with 20 minutes of downtime. He was deemed too unstable for VT ablation and thus emergently underwent a stellate ganglion block. The patient remained encephalopathic post-cardiac arrest with very slow neurologic recovery. He subsequently underwent cardiac transplantation The second case is that of a 63-year-old male with a past medical history of nonischemic cardiomyopathy with LVEF of 10% status post-ICD placement, and VT on amiodarone who presented with episodes of monomorphic VT followed by ICD shocks and syncope. Heart catheterization showed diffuse three-vessel disease. Due to recurrent VT patients, he received an Impella CP as a bridge to VT ablation. Interestingly during ablation, the patient goes into cardiac arrest requiring CPR for 90 minutes. He had successful VT ablation and with no neurological deficit post-procedure. Multiple trials have shown an improved 30-day survival rate without neurological sequelae with early implantation of Impella during ongoing CPR for cardiac arrest. Impella has several favorable properties by unloading the LV which limits the infarct size and maintains cerebral perfusion during the arrest. Preemptive Impella use is often used as a bridge to transplant, however using it as a bridge to ablation is yet to gain prominence.

P11 QUICK PREVENTION OF THE POTENTIALLY SERIOUS CONSEQUENCES OF ELECTROMAGNETIC INTERFERENCE ON A ICD PATIENT THANKS TO THE REMOTE MONITORING SYSTEM OF THE DEVICE

Abstract Clinical Case We report the case of a 84–year–old female patient suffering from post–infarct heart disease with severe systolic dysfunction, wearing a dual–chamber defibrillator in secondary prevention because she had previously presented an episode of monomorphic ventricular tachycardia. After the implant, the patient was enrolled in the remote monitoring service of the device and constantly followed by our team. After a few months, at the remote control we found repeated episodes of very short duration of an alarm recognized by the device as ventricular arrhythmia in the VF window. Contrary to the arrhythmic interpretation of the device, the analysis of the EGM by the medical and nursing staff highlighted an electromagnetic interference defined by the type of signal, the presence of the same in all channels and by the lack of correlation with the underlying heart rhythm. The sensing of the ventricular lead was 5–6 mV, at the lower limits but stable over time, the other parameters were optimal. The patient was promptly contacted and questioned about the circumstances and symptoms: she was asymptomatic and we found that the interference came in conjunction with the use of a cordless telephone. The alarm was related to the electromagnetic field generated by the phone and the woman was asked to stop using the device with subsequent absence of device alarms. Electromagnetic interference in defibrillators can be a cause of potentially serious inappropriate therapies (ATP, pacing and shock), the analysis and correct interpretation of the EGM by the clinician is essential for the prevention of the same. Thanks to the efficiency of the remote monitoring service, the risk of serious consequences for our patient was avoided. Subsequently the lead was repositioned due to a worsening of the sensing, but even before the re–intervention there was no longer any false alarm thanks to the absence of the environmental source of interference. The remote monitoring service applied to implantable defibrillation systems is a valuable tool for identifying lead problems or, as in this case, environmental problems, and toprevent, thanks to rapid intervention, further potentially serious complications.

Continuous Heart Rate Monitoring for Automatic Detection of Life-Threatening Arrhythmias With Novel Bio-Sensing Technology.

Aims: Assessing the effectiveness of novel bio-sensing technology (CardiacSense), for accuracy and reliability of automatic detection of life-threatening arrhythmias.Methods and Results: This prospective study consisted of Eighteen patients (13 males and 5 females, mean age 59.4 ± 21.3 years) undergoing induction of ventricular tachycardia/fibrillation or provocation of transient ventricular asystole. We tested the detection of provoked ventricular arrhythmias by a wrist-worn watch-like device which uses photoplethysmography (PPG) technology to detect the cardiac rhythm. We used simultaneous electrocardiographic (ECG) recordings as gold standard for arrhythmia definition and confirmation of beat-to-beat detection. A total of 1,527 QRS complexes were recorded simultaneously by ECG and PPG. The overall correlation between the ECG (R-R intervals) and the PPG (G-G intervals) was high, with a correlation coefficient of R = 0.949 (p < 0.001). The device accurately detected all events of mimicked life endangering arrhythmias, including five events of transient (adenosine-induced) ventricular asystole as well as seven episodes of monomorphic ventricular tachycardia and 6 events of ventricular fibrillation.Conclusion: This proof-of-concept study suggests that wearable devices using PPG technology, currently used to detect atrial fibrillation, may also have a role as automatic detectors of life-threatening arrhythmias.

Inherited heart rhythm and conduction disorders in children with infectious diseases

Introduction. One of the causes of sudden cardiac death in children is inherited arrhythmias. In view of the links between the increase in body temperature and the manifestation of some inherited cardiac arrhythmias (including typical electrocardiographic changes), the frequency of inherited cardiac arrhythmias in children with infectious diseases have been analyzed.The relevance of the study: is initiated by the necessity of timely diagnosis of inherited cardiac arrhythmias and conduction in children in order to prevent sudden cardiac death in them.The purpose of the study: to determine the frequency of inherited arrhythmias in children with infectious diseases based on clinical and electrocardiographic analysis.Materials and methods: 3584 electrocardiograms (ECGs) of children with infectious diseases (average age 8.5 ± 5.3 years old; boys – 57.5%, girls – 42.5%) hospitalized in the Pediatric Research and Clinical Center for Infectious Diseases were analyzed. Patients with changes in the ECGs were given additional examination depending on the intended diagnosis (inherited arrhythmias): 24-Hour Holter ECG monitoring, stress test, echocardiography. The family history was also clarified, and the parents’ ECG was analyzed.Results and conclusions. ECG changes, which are typical for Brugada syndrome (type 1), were detected in two children (0.05%) at first. Long QT syndrome was also detected in two children (0,05%). Mutations in the SCN5A gene were identified in children with Brugada syndrome, and in the KCNQ1 gene with long QT syndrome. An episode of monomorphic ventricular tachycardia was recorded at night in a 5-year-old girl with atrioventricular block 1 degree, hypoadaptation of the QT interval with repeated Holter ECG monitoring during sleep. Cases of life-threatening ventricular arrhythmias have previously been described in the literature in patients with Brugada syndrome. An increase in body temperature leads to disruption of the sodium ion channels which underlie the development of this syndrome, thereby, on the one hand, increasing the risk of life-threatening arrhythmias and sudden cardiac death, on the other hand, to the clinical manifestation of the disease, allowing the diagnosis to be made in time. In the cases of long QT syndrome, in our study, the increase in the corrected QT interval (QTc) is most likely due to a change in heart rate rather than a direct effect of an increase in body temperature on the ion channels.

Management of ventricular tachycardia in the ablation era: results of the European Heart Rhythm Association Survey.

Patients with sustained ventricular tachycardia (VT) are at risk of sudden death. Treatment options for VT include antiarrhythmic drug therapy, insertion of an implantable cardioverter-defibrillator, and catheter ablation. Evidence on indications for VT ablation, timing, ablation strategies, and periprocedural management is sparse. The aim of this European Heart Rhythm Association (EHRA) survey was to evaluate clinical practice regarding management of VT among the European countries. An electronic questionnaire was sent to members of the EHRA Electrophysiology Research Network. Responses were received from 88 centres in 12 countries. The results have shown that management of VTs is very heterogeneous across the participating centres. Indications, periprocedural management, and ablation strategies vary substantially. This EP Wire survey has revealed that catheter ablation is the first-line therapy for the treatment of recurrent monomorphic stable VT in patients without structural heart disease as well as in patients with ischaemic cardiomyopathy and impaired left ventricular ejection fraction in the majority of centres. Furthermore, in patients with ischaemic cardiomyopathy and the first episode of monomorphic VT, most centres (62.0%) performed catheter ablation. On the contrary, in patients with non-ischaemic cardiomyopathy, amiodarone (41.4%) and catheter ablation (37.1%) are used in a very similar proportion. Ablation strategies, endpoints, and post-ablation antithrombotic management vary substantially among European centres.

Is something hidden during tachycardia?

A 61-year-old male patient was referred to our electrophysiology lab for ventricular tachycardia (VT) ablation. The patient had a history of ischaemic cardiomyopathy with impaired left ventricular function and received a dual chamber implantable cardioverter-defibrillator (ICD) after he survived a cardiac arrest. During the past months, the patient suffered from recurrent episodes of monomorphic VT with appropriate ICD therapies. Electrocardiogram suggested an apical origin of the VT. Prior to VT ablation, device interrogation showed a stored supraventricular tracing (Fig. 1).

Abstract 17547: Syncope and Inferior ST Elevations: A Diagnosis Within the Heart

A 53 year old woman with a history of diabetes and hypertension presented with syncope, hypotension, and electrocardiography demonstrating inferior ST elevations. The week prior to admission she treated an episode of left knee pain with an admixture of Chinese herbs. Two days prior to presentation she noted the onset of fevers, myalgias and dizziness culminating in syncope the day of admission. Initial electrocardiogram demonstrated complete heart block and junctional escape with inferior ST elevations. Cardiac catheterization demonstrated no epicardial coronary disease. Laboratory studies revealed acute kidney injury, elevated cardiac biomarkers, and a normal white blood cell count with normal differential. Upon transfer to our hospital, the patient was hypotensive requiring temporary ventricular pacing and vasopressor support. Echocardiogram demonstrated severe systolic dysfunction with LVEF of 31%. On arrival, she was noted to have episodes of monomorphic ventricular tachycardia. Etiologies of fulminant myocarditis considered included viral (lymphocytic), giant cell myocarditis, and sarcoid a well as acute eosinophilic myocarditis given recent ingestion of novel herbal mixture. Given the potential for steroid-responsive etiologies, endomyocardial biopsy was performed with institution of mechanical support ( intra-aortic balloon pump) and administration of parenteral steroids. Inotropic and mechanical support were weaned within 72 hours of administration of steroids and she demonstrated normalization of electrical conduction. Biopsy demonstrated acute necrotizing eosinophilic myocarditis (ANEM). Cardiac MRI demonstrated acute myocarditis, subacute inferior infarct, and no LV thrombus. ANEM represents an often fatal, fulminant form of eosinophilic heart disease and can present without systemic eosinophilia. Triggers can include antecedent viral illness and drug hypersensitivity (including herbal mixtures). Eosinophilic proteins can stimulate platelet aggregation and coronary vasoconstriction. Considered mechanisms of inferior infarct included LV thrombus with coronary embolism. The patient was treated with steroids and anticoagulation with recovery of baseline cardiopulmonary function.

Mitral Subvalvular Aneurysm in a Patient with Chagas Disease and Recurrent Episodes of Ventricular Tachycardia.

Subvalvular left ventricular aneurysm is a rare disease of obscure origin suggesting unique causes such as congenital, traumatic, and inflammatory or infectious diseases. Its mortality is closely related to heart failure, mitral insufficiency, thromboembolic phenomena, and cardiac arrhythmias. Although association with coronary artery disease is not described, the compression of epicardial vessels by the aneurysm may lead to ischemic manifestations. We report here a case of mitral subvalvular left ventricular aneurysm of probable chagasic origin, in a patient with normal left ventricular function evolving with repeated episodes of monomorphic ventricular tachycardia, despite noninducible electrophysiological testing and the use of optimal medical treatment, including amiodarone. The indication for implantable cardioverter-defibrillator in patients with Chagas cardiomyopathy and segmental wall motion abnormalities but without global systolic dysfunction remains unclear in literature, even in the presence of complex ventricular arrhythmias. A brief review of the literature on morphological features, diagnosis, prognosis, and treatment will be also discussed.

Hemodialysis Treatment of Monomorphic Ventricular Tachycardia Associated with Chronic Lithium Toxicity

A patient with chronic lithium toxicity developed a life-threatening ventricular arrhythmia that resolved during removal of lithium by hemodialysis. Chronic lithium toxicity commonly results from diminished elimination and can produce neurotoxicity. Cardiovascular complications have been reported and generally affect the sinoatrial node and produce bradyarrhythmias. The majority of these arrhythmias require no emergent intervention. Ventricular arrhythmias associated with lithium toxicity are occasionally mentioned in the literature, but actual cases are rarely reported. A 74-year-old man was brought into the emergency department with a 3-day history of progressive encephalopathy, tremor, and weakness. The lithium level was elevated at 2.2mmol/L, with a normal serum potassium. Electrocardiography revealed nonsustained monomorphic ventricular tachycardia (120-130 beats/min) lasting up to 1min, alternating with sinus bradycardia and wandering atrial pacemaker. Episodes of monomorphic ventricular tachycardia recurred >100 times. The patient required a norepinephrine infusion for hypotension. Emergent hemodialysis was initiated to remove lithium and to treat the monomorphic ventricular tachycardia, which was felt to be secondary to lithium toxicity. Episodes of monomorphic ventricular tachycardia abated as hemodialysis progressed. The episodes resolved completely within 4h of initiating hemodialysis. The patient was discharged home in sinus rhythm on day 5. Lithium was not reinstated. Monomorphic ventricular tachycardia associated with chronic lithium toxicity is exceptionally rare. Hemodialysis is a treatment option.

Procainamide and lidocaine produce dissimilar changes in ventricular repolarization and arrhythmogenicity in guinea‐pig

Procainamide is class Ia Na(+) channel blocker that may prolong ventricular repolarization secondary to inhibition of IK r , the rapid component of the delayed rectifier K(+) current. In contrast to selective IN a blockers such as lidocaine, procainamide was shown to produce arrhythmogenic effects in the clinical setting. This study examined whether pro-arrhythmic responses to procainamide may be accounted for by drug-induced repolarization abnormalities including impaired electrical restitution kinetics, spatial gradients in action potential duration (APD), and activation-to-repolarization coupling. In perfused guinea-pig hearts, procainamide was found to prolong the QT interval on ECG and left ventricular (LV) epicardial monophasic APD, increased the maximum slope of electrical restitution, enhanced transepicardial APD variability, and eliminated the inverse correlation between the local APD and activation time values determined at distinct epicardial recording sites prior to drug infusion. In contrast, lidocaine had no effect on electrical restitution, the degree of transepicardial repolarization heterogeneities, and activation-to-repolarization coupling. Spontaneous episodes of monomorphic ventricular tachycardia were observed in 57% of procainamide-treated heart preparations. No arrhythmia was induced by lidocaine. In summary, this study suggests that abnormal changes in repolarization may contribute to pro-arrhythmic effects of procainamide.

Flecainide-Induced Proarrhythmia Is Attributed to Abnormal Changes in Repolarization and Refractoriness in Perfused Guinea-Pig Heart

Flecainide is nonselective Na(+) channel blocker which may also inhibit I(Kr), the rapid component of the delayed rectifier. This study was designed to explore if proarrhythmic responses to flecainide noted in cardiac patients may be partly attributed to abnormal changes in repolarization and refractoriness. Monophasic action potential duration (APD) and effective refractory periods (ERP) were assessed at distinct epicardial and endocardial sites along with volume-conducted ECG recordings in isolated perfused guinea-pig heart preparations. Flecainide was found to prolong ventricular repolarization, with effect being greater at the left ventricular compared with the right ventricular epicardium. This change translated to reversal of the normal right ventricular-to-left ventricular transepicardial APD difference determined before drug infusion. An inverse correlation between local epicardial APD and corresponding activation time values seen at baseline was eliminated in flecainide-treated hearts, indicating the activation-to-repolarization uncoupling. Over transmural plane, flecainide produced a greater ERP lengthening at endocardium than epicardium, thus markedly increasing ERP dispersion across ventricular wall. Spontaneous short-lasting episodes of monomorphic ventricular tachycardia were observed in 45% of heart preparations upon flecainide infusion. In conclusion, in nonischemic guinea-pig heart, flecainide-induced proarrhythmia may be partly attributed to abnormal spatial gradients in repolarization and refractoriness and impaired transepicardial activation-to-repolarization coupling.

Dofetilide Promotes Repolarization Abnormalities in Perfused Guinea-pig Heart

Dofetilide is class III antiarrhythmic agent which prolongs cardiac action potential duration because of selective inhibition of I (Kr), the rapid component of the delayed rectifier K(+) current. Although clinical studies reported on proarrhythmic risk associated with dofetilide treatment, the contributing electrophysiological mechanisms remain poorly understood. This study was designed to determine if dofetilide-induced proarrhythmia may be attributed to abnormalities in ventricular repolarization and refractoriness. The monophasic action potential duration and effective refractory periods (ERP) were assessed at distinct epicardial and endocardial sites along with volume-conducted ECG recordings in isolated, perfused guinea-pig heart preparations. Dofetilide was found to produce the reverse rate-dependent prolongation of ventricular repolarization, increased the steepness of action potential duration rate adaptation, and amplified transepicardial variability in electrical restitution kinetics. Dofetilide also prolonged the T peak-to-end interval on ECG, and elicited a greater prolongation of endocardial than epicardial ERP, thereby increasing transmural dispersion of refractoriness. At epicardium, dofetilide prolonged action potential duration to a greater extent than ERP, thus extending the critical interval for ventricular re-excitation. This change was associated with triangulation of epicardial action potential because of greater dofetilide-induced prolonging effect at 90 % than 30 % repolarization. Premature ectopic beats and spontaneous short-lasting episodes of monomorphic ventricular tachycardia were observed in 44 % of dofetilide-treated heart preparations. Proarrhythmic potential of dofetilide in guinea-pig heart is attributed to steepened electrical restitution, increased transepicardial variability in electrical restitution kinetics, amplified transmural dispersion of refractoriness, increased critical interval for ventricular re-excitation, and triangulation of epicardial action potential.

Impact of Na+ channel blockers on transmural dispersion of refractoriness and arrhythmic susceptibility in guinea-pig left ventricle

Clinically, class Ib antiarrhythmic agents (selective INa blockers) are considered to be safe drugs, whereas class Ia and Ic agents (non-selective blockers of both INa and IKr, the rapid component of the delayed rectifier) may evoke proarrhythmia. I hypothesized that this difference is accounted for by differential drug effects on transmural dispersion of refractoriness, in the presence of the reciprocal distribution profile of INa and IKr across ventricular wall, as determined in previous studies. Specifically, less epicardial than endocardial INa reserve would likely contribute to a greater prolongation of the effective refractory period (ERP) at epicardium by the INa blocker, thereby reducing epicardial-to-endocardial ERP dispersion, with resulting antiarrhythmic effect. In contrast, less endocardial than epicardial IKr reserve would likely contribute to a greater prolongation of repolarization at the endocardium by the IKr blocker, thereby amplifying transmural ERP dispersion and inducing arrhythmia. In perfused guinea-pig hearts, dofetilide, a specific IKr blocker, as well as class Ia (quinidine, procainamide) and class Ic agents (flecainide), were found to prolong the QT interval and monophasic action potential duration, and elicited greater endocardial than epicardial ERP prolongation, thus markedly increasing transmural ERP dispersion. These changes were associated with episodes of monomorphic ventricular tachycardia in 30–40% of experiments. In contrast, class Ib agents (lidocaine, mexiletine) evoked greater epicardial than endocardial ERP lengthening, thereby decreasing transmural ERP dispersion, and produced no tachyarrhythmia. These findings suggest that transmural ERP dispersion is the electrophysiological determinant which may shape the profile of class I agent effects on arrhythmic susceptibility.

Multiple morphologies of ventricular tachycardia assessed by implantable cardioverter-defibrillator electrograms in a patient with Chagas disease, successfully treated with catheter ablation: modern problems, old solutions

A 60-year-old man with Chagas disease, implanted with an implantable cardioverter defibrillator (ICD), experienced electrical storm. The ICD-stored electrograms revealed several ventricular tachycardia (VT) episodes with two different morphologies, confirmed thereafter by surface electrocardiogram. Both VTs originated from two different re-entry circuits and were successfully ablated. This case highlights the usefulness of ICD electrograms in identifying two VTs as having different sites of origin. Analysis of implantable cardioverter-defibrillator electrograms (ICD-EG) showed that monomorphic ventricular tachycardia (VT) with different QRS morphologies during different episodes (multiple morphologies, MM) predicted higher mortality. 1 A 60-year-old man implanted with an ICD (Medtronic Maximo-VR7232) for secondary prevention of death, with Chagas disease and left ventricular ejection fraction (LVEF), 0.45 was hospitalized for electrical storm. The ICD interrogation revealed 62 episodes of monomorphic VT. Analysing ICD-EG, a difference in morphology was seen only in the HVA/HVB electrogram (a QS complex in Figure 1A; a Qr complex in Figure 1B). During hospitalization he experienced several VT episodes and surface-electrocardiogram Figure 1 Schematic representation of the endocardial surface of the left ventricle. (A) and (B) Implantable cardioverter defibrillator- stored electrograms showing two different morphologies of the HVA/HVB electrogram. Note that this difference is not evident in the Vtip-Vring electrogram. (C) and (D) Twelve-lead surface electrocardiogram from two different spontaneous episodes of monomorphic ventricular tachycardia. (E) and (F) Surface and endocardial recordings from the two ventricular tachycardias induced at electrophysio- logicalstudy.NotethatQRSconfigurationsofinducedventriculartachycardiasmatchthoseofthespontaneousventriculartachycardias. There is a mismatch in lead V6 from ventricular tachycardia 1, probably due to different electrode position.

Case report: Arrhythmia à deux: A poisonous salad for two

Aconitum known as aconite or monkshood is a genus of flowering plants belonging to the buttercup family. The most common plant in this genus, Aconitum napellus (Monkshood) is of toxicological and possible therapeutic importance. Despite its known toxicity, Aconite roots are often sold freely and are commonly used in Chinese and Japanese herbal medicine for treating musculoskeletal pains. All parts of this plant, but especially the roots, contain various terpenoid alkaloids with aconitine being the most dangerous, causing neuroand cardiotoxicity. Aconitine blocks conduction of voltage-sensitive sodium channels in the exons of cardiac and nerve tissue. This may result in the rapid onset of various gastro-intestinal, neurological and cardiac symptoms. If untreated, shock, coma and death may ensue. Aconite poisoning is extremely rare in Europe. It may occur because of confusion with an edible plant, accidental ingestion by children, or deliberate intoxication in suicide attempts. Intoxication requires strict surveillance and treatment. Treatment is mainly symptomatic, but use of hemoperfusion, or intravenous amiodarone and magnesium has been successfully used in combating ventricular tachycardias [1–9]. An 81 year old, previously healthy man, arrived at our Emergency Department with cardiorespiratory arrest. ECG showed polymorphic ventricular tachycardia, interrupted by episodes of monomorphic ventricular tachycardia (Figs. 1 and 2). Resuscitation was started. During more than 2 h, arrhythmias were incessant and refractory to

Repetitive Monomorphic Ventricular Tachycardia as a Manifestation of Suboptimally Treated Thyrotoxicosis

Monomorphic ventricular tachycardia (VT) is a unique manifestation of hyperthyroidism. We present the case of a 41-year-old male with a history of hyperthyroidism presenting with palpitations secondary to non-sustained episodes of monomorphic VT. Cardiac arrhythmias due to thyrotoxicosis are perpetually supraventricular in origin. Monomorphic VT in the setting of thyrotoxicosis in the absence of structural heart disease is exceedingly rare. After starting propranolol and increasing the dose of methimazole, the patient had no further episodes of VT. It is important to recognize repetitive monomorphic VT as an understated but important manifestation of thyrotoxicosis. Propranolol is associated with an excellent response in these patients and anti-thyroid medications such as methimazole effectively reverse thyrotoxicity.

Increased Sensitivity to Local Anesthetic Drugs

See related article, pages 396–404 This issue of Circulation Research contains the surprising report of a middle-aged African American with Brugada syndrome associated with 2 widely separated missense mutations in the Na channel gene and with dramatically increased lidocaine sensitivity.1 Following a seizure in the emergency room, the patient developed an episode of monomorphic ventricular tachycardia terminated by electric shock. After IV lidocaine was started, the patient quickly developed the ECG characteristics of Brugada phenomenon. Although local anesthetics (LAs) with slow off rates typically induce such ECG changes, this has not been reported for lidocaine. After identifying the 2 mutations in the Na channel α subunit gene of this individual, Barajas-Martinez et al1 exposed the mutated channel to lidocaine and found markedly increased sensitivity to block. The finding of 2 unrelated mutations in the same Na channel gene is unusual. Ackerman et al2 reported that 1 of these mutations, L1308F, is a rare polymorphism (seen once in 319) in an African-American population but not in white, Asian, or Hispanic populations. Barajas-Martinez et al1 indicated that they have seen this polymorphism in 1% of their white population. No previous studies of lidocaine sensitivity have been reported for this polymorphism, but it now seems possible that individuals with the L1308F polymorphism are at risk of local anesthetic toxicity. This question deserves follow-up. Why should we care much about rare syndromes such as Brugada when they are a mere drop in the bucket of total cardiac arrhythmic death? They are a window into mechanisms of lethal arrhythmia and their study can lead to preventive or corrective therapy. Although these monogenetic diseases are rare, the conditions can be reproduced in the laboratory, an invaluable tool that is very difficult to achieve with multifactorial diseases such as regional ischemia. Indeed, …

Electrophysiologic Manifestations of Ventricular Tachyarrhythmias Provoking Appropriate Defibrillator Interventions in High‐Risk Patients with Hypertrophic Cardiomyopathy

Our objective was to determine features of ventricular tachyarrhythmias triggering appropriate implantable cardioverter-defibrillator (ICD) interventions in hypertrophic cardiomyopathy (HCM). The study cohort was 68 high-risk HCM patients who received ICDs for primary sudden cardiac death prevention from 1995 to 2003. All episodes of sustained ventricular tachyarrhythmias identified by stored intracardiac electrograms were analyzed. Nine patients had 51 episodes of sustained ventricular tachyarrhythmic events that required device therapy (mean follow-up, 3.4 +/- 2.2 years; cumulative event rate, 3.2% per year): five had 47 episodes of monomorphic ventricular tachycardia (VT); four each had one episode of ventricular fibrillation (VF). Sinus tachycardia or atrial fibrillation was the initiating rhythm in five of nine patients and in 43 of 51 episodes of events. Of the 17 episodes of monomorphic VT detected in the VT zone, 16 (94%) were terminated by antitachycardia pacing. Thirty episodes of monomorphic VT were detected in the VF zone and were terminated by defibrillation. Sustained monomorphic VT is common in a high-risk cohort with HCM. Sinus tachycardia is often the initiating rhythm, suggesting that high sympathetic drive may be proarrhythmic when a susceptible substrate is present. Antitachycardia pacing is highly effective in terminating VT in this patient population.

Syncopal monomorphic ventricular tachycardia with pleomorphism, sensitive to antitachycardia pacing in a patient with Brugada syndrome

Polymorphic ventricular tachycardia and ventricular fibrillation are the most common arrhythmias in Brugada syndrome, causing syncope or sudden death. Sustained monomorphic ventricular tachycardias are rare in this context. We report the case of a 41-year-old man with repetitive syncopal episodes and an ajmaline-induced characteristic Brugada ECG pattern, in whom episodes of monomorphic ventricular tachycardia with pleomorphism and response to ventricular pacing were documented.

Impact of sympathetic innervation on recurrent life-threatening arrhythmias in the follow-up of patients with idiopathic ventricular fibrillation

Idiopathic ventricular fibrillation (IVF) is defined as VF in the absence of any identifiable structural or functional cardiac disease. The underlying pathophysiological mechanisms are unknown. This study was performed to investigate the potential impact of sympathetic dysfunction, assessed by (123)I-meta-iodo-benzylguanidine scintigraphy ((123)I-MIBG SPECT), on the long-term prognosis of patients with IVF. (123)I-MIBG SPECT was performed in 20 patients (mean age 37+/-13 years) with IVF. Mean follow-up of patients after study entry was 7.2+/-1.5 years (range 4.9-10.5 years). Ten patients (five men, five women; mean age 43+/-12 years; p=NS versus study group) with medullary carcinoma of the thyroid gland served as an age-matched control group. Abnormal (123)I-MIBG uptake was observed in 13 patients (65%). During follow-up, 18 episodes of VF/fast polymorphic ventricular tachycardias occurred in four IVF patients with abnormal (123)I-MIBG uptake whereas only two episodes of monomorphic ventricular tachycardia (and no VF) occurred in a single IVF patient with normal (123)I-MIBG uptake. Impairment of sympathetic innervation may indicate a higher risk of future recurrent episodes of life-threatening ventricular tachyarrhythmias in patients with IVF. Studies in larger cohorts are required to validate the significance of (123)I-MIBG SPECT during the long-term follow-up of these patients.