AV Nodal Reentrant Tachycardia Causing Inappropriate ICD Shocks In A Patient With Arrhythmogenic RV Dysplasia

We report a patient with an implantable cardioverter defibrillator (ICD) for arrhythmogenic right ventricular dysplasia (ARVD) who received inappropriate shocks for atrioventricular node reentry tachycardia (AVRNT). Patient had multiple shocks for tachycardia with EGM characteristics of very short VA interval and CL of 300 msec. An electrophysiologic (EP) study reproducibly induced typical AVNRT with similar features. The slow AV nodal pathway ablation resolved the ICD shocks. Despite increasingly sophisticated discrimination algorithms available in modern ICDs, the ability to differentiate SVT from VT can be challenging. Our patient received inappropriate shocks for AVNRT. When device interrogation alone is not conclusive, an EP study may be necessary to determine the appropriate therapeutic course.     

Dual AV Nodal Nonreentrant Tachycardia Resulting in Inappropriate ICD Therapy in a Patient with Cardiac Sarcoidosis

Dual atrioventricular nodal nonreentrant tachycardia (DAVNNT) occurs due to concurrent antegrade conduction over fast and slow atrioventricular nodal pathways and is treated by slow pathway modification. We describe a unique case of a patient with cardiac sarcoidosis who received inappropriate ICD shocks for DAVNNT. Atrial and ventricular device electrograms satisfied both rate and V>A criteria for ventricular tachycardia. We postulate that alterations in refractoriness and conduction as is seen in cardiac sarcoidosis (CS) may have contributed to occurrence of DAVNNT.     

Inappropriate ICD Shocks - When Monitoring Zones Do More Than Monitor

The ventricular tachycardia (VT) monitoring zone in implantable cardioverter defibrillators (ICDs) is usually programmed to detect slow VTs. However, it is not well known whether programming this zone can affect the ICD arrhythmia redetection or confirmation criteria. We report two cases of inappropriate ICD shocks due to the programming of a slow VT monitoring zone in the same device model.     

A New Single Chamber Implantable Defibrillator with Atrial Sensing: A Practical Demonstration of Sensing and Ease of Implantation

Implantable cardioverter-defibrillators (ICDs) terminate ventricular tachycardia (VT) and ventricular fibrillation (VF) with high efficacy and can protect patients from sudden cardiac death (SCD). However, inappropriate shocks may occur if tachycardias are misdiagnosed. Inappropriate shocks are harmful and impair patient quality of life. The risk of inappropriate therapy increases with lower detection rates programmed in the ICD. Single-chamber detection poses greater risks for misdiagnosis when compared with dual-chamber devices that have the benefit of additional atrial information. However, using a dual-chamber device merely for the sake of detection is generally not accepted, since the risks associated with the second electrode may outweigh the benefits of detection. Therefore, BIOTRONIK developed a ventricular lead called the Linox^SMART S DX, which allows for the detection of atrial signals from two electrodes positioned at the atrial part of the ventricular electrode. This device contains two ring electrodes; one that contacts the atrial wall at the junction of the superior vena cava (SVC) and one positioned at the free floating part of the electrode in the atrium. The excellent signal quality can only be achieved by a special filter setting in the ICD (Lumax 540 and 740 VR-T DX, BIOTRONIK). Here, the ease of implantation of the system will be demonstrated.     

Inappropriate Detection of a Supraventricular Tachycardia as Dual Tachycardia by the PR Logic™ Algorithm

Tachycardia detection and therapy algorithms in Implantable Cardioverter-Defibrillators (ICD) reduce, but do not eliminate inappropriate ICD shocks. Awareness of the pros and cons of a particular algorithm helps to predict its utility in specific situations. We report a case where PR logic™, an algorithm commonly used in currently implanted ICDs to differentiate supraventricular tachycardia (SVT) from ventricular tachycardia resulted in inappropriate detection and shock for an SVT, and discuss several solutions to the problem.     

ICD discrimination of SVT versus VT with 1:1 V-A conduction: A review of the literature

Inappropriate ICD shocks are associated with increased mortality. They also impair patients'' quality of life, increase hospitalizations, and raise health-care costs. Nearly 80% of inappropriate ICD shocks are caused by supraventricular tachycardia. Here we report the case of a patient who received a single-lead dual-chamber sensing ICD for primary prevention of sudden cardiac death and experienced inappropriate ICD shocks. V-A time, electrogram morphology, and response to antitachycardia pacing suggested atrioventricular nodal reentry tachycardia, which was confirmed in an electrophysiology study. Inspired by this case, we performed a literature review to discuss mechanisms for discrimination of supraventricular tachycardia with 1:1 A:V relationship from ventricular tachycardia with 1:1 retrograde conduction.     

Coexistence of atrioventricular nodal reentrant tachycardia and idiopathic left ventricular outflow-tract tachycardia

Double tachycardia is a relatively rare condition. We describe a 21 year old woman with history of frequent palpitations. In one of these episodes, she had wide complex tachycardia with right bundle branch and inferior axis morphology. A typical atrioventricular nodal tachycardia was induced during electrophysiologic study, aimed at induction of clinically documented tachycardia. Initially no ventricular tachycardia was inducible. After successful ablation of slow pathway, a wide complex tachycardia was induced by programmed stimulation from right ventricular outflow tract. Mapping localized the focus of tachycardia in left ventricular outflow tract and successfully ablated via retrograde aortic approach. During 7 month's follow-up, she has been symptom free with no recurrence. This work describes successful ablation of rare combination of typical atrioventricular nodal tachycardia and left ventricular outflow tract tachycardia in the same patient during one session.     

Pseudo loss of capture on 12 lead electrocardiogram in patient with an implantable cardiac defibrillator

This case report presents a 70-year-old-male, brought in by ambulance for assessment of chest pain and presyncope, with a paced ECG showing possible non-capture following ventricular pacing spikes. This was demonstrated to be pseudo non-capture with a 12-lead electrocardiogram performed in emergency and a device interrogation demonstrating ventricular capture.     

Measure twice, cut once: pitfalls in the diagnosis of supraventricular tachycardia

In atrioventricular nodal and atrioventricular reentrant tachycardia, the relative timing of atrial and ventricular activation may sometimes be very similar, even during electrophysiological studies, and this may lead to an erroneous diagnosis and inappropriate treatment. As examples, we describe two cases that were recently referred to our hospital for a second opinion and treatment of paroxysmal supraventricular tachycardia. In both, the original diagnosis of the referring centres was commontype atrioventricular nodal reentrant tachycardia. Catheter ablation in those centres was unsuccessful. During our electrophysiological studies, however, an atrioventricular reentrant tachycardia was demonstrated, using a concealed accessory pathway for retrograde conduction in both patients. The accessory atrioventricular connection was successfully ablated and on follow-up both patients remained free of symptoms without medication. These findings illustrate the importance of complete electrophysiological analysis even for apparently simple supraventricular arrhythmias. (Neth Heart J 2010;18:78–84.)     

A Canadian hospital's experience with the automatic implantable cardioverter/defibrillator.

The automatic implantable cardioverter/defibrillator is a device that can be implanted in patients for treatment of recurrent ventricular tachycardia and ventricular fibrillation. It was recently approved for clinical use in Canada. The authors describe their experience with 12 patients (mean age 51.3 years) who underwent implantation of a defibrillator. All 12 patients had a history of documented ventricular fibrillation, which was idiopathic in 3 and due to ischemic heart disease in 9. Electrophysiologic testing revealed inducible ventricular tachycardia or ventricular fibrillation in 8 of the 10 patients tested. An important criterion for selection for implantation was failure of pharmacologic therapy to suppress ventricular arrhythmias induced during electrophysiologic testing. Of the 12 patients, 1 died within 24 hours after implantation. During a mean follow-up period of 15.5 months there were no further deaths. All the surviving patients expressed satisfaction with the device; five of the seven under the age of 60 years have returned to work, and one has returned to school. This initial favourable experience with the automatic implantable cardioverter/defibrillator suggests that future increases in the availability of the device and improvements in its function will lead to much more widespread use, as the population of patients at risk of sudden cardiac death is large.     

Inappropriate defibrillator shock due to oversensing. What is the mechanism?

Implantable cardioverter defibrillator (ICD) is often advised for secondary prevention of sudden cardiac death. Inappropriate shocks from ICD is uncommon but can seriously affect the quality of life. One of the reasons for inappropriate ICD shock is loose set screw, which may remain undetected by device interrogation and/or fluoroscopy. A 55-year lady presented with multiple inappropriate shocks few hours after an ICD implantation. The discrepancy between near field (NF, tip to ring) and far field (FF, Can to RV coil) signals helped us to suspect noise related to loose set screw, as the underlying problem. Re-exploration of the pocket had to be performed as the last resort to confirm the diagnosis and rectify the problem.     

Normal pacing function with normal impedance trends despite evident lead fracture in an implantable defibrillator – What is the mechanism?

A 63-year-old lady with a high-grade atrioventricular (AV) block and a structurally normal heart underwent permanent pacemaker implantation (dual chamber, Medtronic Ltd) 8 years back. On follow up, she had a recurrence of syncope after 3 years. The device interrogation at that time had revealed ventricular tachycardia (VT) for which she underwent implantable cardioverter defibrillator (ICD, Medtronic Ltd, Egida DR, DF1) upgradation at another center (electrograms not available). Now, she presents with episodes of presyncope after another 5 years. The Echocardiography was unremarkable. The ICD was interrogated & there was a stored ventricular fibrillation (VF) episode. But the electrograms suggested noise over a true VF electrogram noted in both near and far-field. In all probability, the VF was not a true one which might have arisen from some lead noise or from an electromagnetic interference (EMI). Fluoroscopy revealed an evident lead fracture near the superior vena cava (SVC) coil. The stored electrogram (EGM) characteristics also suggested possible lead noise rather than a true VF. She was advised for lead revision. Interestingly, all pacing parameters were normal along with normal impedance despite the evident lead fracture. This happened due to the ICD lead arrangements as there are separate electrodes for the SVC/RV coil and pacing. While the SVC coil was damaged, the pacing electrodes remained unaffected. Since the patient has no episode of true VT/NSVT and the echocardiography was normal, she was managed temporarily by changing the pacemaker to asynchronous (DOO) mode.     

Inhibition of ventricular output in a dual chamber pacemaker with normal pacing and sensing parameters: What is the mechanism?

A 65-year-old gentleman with dual chamber pacemaker presented with presyncope. The ECG raised concerns of oversensing which was confirmed by magnet response. The device interrogation revealed noise in ventricular channel temporally associated with P wave. The pacing thresholds were normal. Although the ventricular lead impedance was within normal limit the impedance trend suggested 100 Ω decline over last 1 year. RV lead insulation failure was speculated and supported by the bipolar and unipolar intracardiac electrogram. Device was programmed to DOO temporarily. He underwent RV lead replacement uneventfully.     

Confounding factors leading to misdiagnosing ventricular tachycardia as supraventricular in the emergency room

Studies conducted during the last 50 years have proposed electrocardiographic criteria and algorithms to determine if a wide QRS tachycardia is ventricular or supraventricular in origin. Sustained ventricular tachycardia is an uncommon reason for consultation in the emergency room. The latter and the complexity of available electrocardiographic diagnostic criteria and algorithms result in frequent misdiagnoses. Good hemodynamic tolerance of tachycardia in the supine position does not exclude its ventricular origin. Although rare, ventricular tachycardia in patients with and without structural heart disease may show a QRS duration <120 ms. Interruption of tachycardia by coughing, carotid sinus massage, Valsalva maneuver, or following the infusion of adenosine or verapamil should not discard the ventricular origin of the arrhythmia. In patients with regular, uniform, sustained broad QRS tachycardia, the presence of structural heart disease or A-V dissociation strongly suggest its ventricular origin. Occasionally, ventricular tachycardia can present with AV dissociation without this being evident on the 12-lead ECG. Cardiac auscultation, examination of the jugular venous pulse, and arterial pulse palpation provide additional clues for identifying A-V dissociation during tachycardia. This paper does not review the electrocardiographic criteria for categorizing tachycardia as ventricular but rather why emergency physicians misdiagnose these patients.     

Entrainment mapping of ventricular tachycardia

A 64-year-old male, with a history of a lateral myocardial infarction, presented with haemodynamically well-tolerated incessant therapy-resistant slow monomorphic ventricular tachycardia (mVT), despite implantable cardioverter defibrillator and antiarrhythmic drugs.     

Misdiagnosing ventricular tachycardia in patients with underlying conduction disease and similar sinus and tachycardia morphologies.

Six patients presented with wide-complex tachycardias with QRS morphologies similar to those seen on their electrocardiograms that showed normal sinus rhythms. During normal sinus rhythm, each patient had an underlying intraventricular conduction abnormality or bundle branch block. Despite the similarity of the QRS complexes to those seen during sinus rhythm, the tachycardias subsequently proved to be ventricular in origin in each patient. It is important not to misdiagnose these disorders as supraventricular tachycardia as an erroneous diagnosis may result in inappropriate management.     

Desynchronization in a cardiac resynchronization device induced by a pacemaker-mediated tachycardia algorithm

This report describes the occurrence of desynchronization in a patient with a cardiac resynchronization device programmed with an active pacemaker-mediated tachycardia algorithm based on AV delay modification. Desynchronization was precipitated by sinus tachycardia and the abrupt return of the prevailing AV delay that followed the periodic prolongation of the AV delay mandated by activity of the algorithm. Prevention of desynchronization in this setting requires programming a right ventricular upper rate interval longer than the sum of the programmed ventriculoatrial interval and the AV delay.     

Unusual cause of cardiomyopathy in a young woman

Dual atrioventricular nodal nonreentrant tachycardia (DAVNNT) is a rare form of supraventricular tachycardia. In some patients, the presence of a dual pathway physiology results in two paths in the atrioventricular (AV) node with different conduction velocities. An atrial impulse arriving at the AV node may unfold and travel along these two pathways simultaneously, causing two ventricular activations. Thus, the ventricular rate will be twice the atrial rate. DAVNNT is less common than AVNRT, but its frequency may be underestimated.The ECG is crucial to suspect the diagnosis. At first glance it looks like an irregular tachycardia, but a more careful look shows a rhythmic pattern. A sinus P wave followed by two QRS complexes (narrow or wide) should raise suspicion of this arrhythmia.It is often unnoticed by the patient, and ventricular dysfunction due to tachycardiomyopathy is not uncommon. The response of DAVNNT to medication, including beta-blockers, flecainide, and amiodarone is very poor or absent, so the treatment of choice is slow pathway ablation. We report a Case of cardiomyopathy caused by this entity.     

Long-Standing Undiagnosed Sheehan Syndrome Presenting as Polymorphic and Monomorphic Ventricular Tachycardia: A Case Series of 2 Patients

ObjectiveTo describe 2 cases of Sheehan syndrome presenting with ventricular tachycardia.MethodsIn this case series, we present 2 cases of Sheehan syndrome presenting with ventricular tachycardia, which is an extremely rare complication of Sheehan syndrome. We review the literature for cases of panhypopituitarism presenting with ventricular tachycardia and also review the pathophysiologic mechanisms underlying development of ventricular tachycardia in these patients.ResultsTwo female patients presented with ventricular tachycardia. One patient had monomorphic and the other had polymorphic ventricular tachycardia. On further workup, both patients were found to have panhypopituitarism. Due to past history of postpartum hemorrhage, both patients were suspected of having Sheehan syndrome as the cause of panhypopituitarism. Electrocardiogram revealed prolonged QT interval. Both patients were started on hormone replacement therapy. Both patients responded well initially and were discharged home. One of the patients is alive and healthy at the time of this report. However, the other patient was readmitted with seizures a few days after discharge and unfortunately died of sudden cardiac arrest.ConclusionUntreated cases of Sheehan syndrome can present with fatal ventricular tachycardia. Hormone replacement in these patients can treat and prevent fatal arrhythmias. (Endocr Pract. 2014;20:e211-e214)     

Morphological detection algorithms for the automatic implantable cardioverter/defibrillator (AICD).

To prevent sudden cardiac death of patients who are at risk from long standing tachyarrhythmia the implantable cardioverter defibrillator (ICD) is the first choice therapy. ICDs use a range of electrostimuli up to defibrillation, which is a non synchronous high energy shock, whereas cardioversion is synchronous with the ECG. In order to know when and how to react, a detection algorithm, which analyses an intracardial electrocardiogram (ECG) and classifies the heart rhythm, is implemented in every ICD. All detection algorithms use the heart rate to classify the different heart rhythms roughly. If a tachycardia is detected, it is important to discriminate between a ventricular tachycardia, which is life threatening and a supraventricular tachycardia, which is much less threatening. To be able to make this distinction the detection algorithms analyse the behaviour of the heart cycle intervals, the ECG-morphology or in addition to the ventricular ECG, an atrial ECG. In this paper morphological algorithms will be evaluated and newly developed algorithms will be presented. Recent algorithms use the mathematical wavelet theory. The evaluation shows that these get better results than all but one of the simpler classical morphological algorithms. A new wavelet based algorithm, developed by the authors, exhibits the best detection results.