Inappropriate discharges from an intravenous implantable cardioverter defibrillator due to T-wave oversensing

Atrial Fibrillation and Ventricular Tachyarrhythmias: Advancements for Better Outcomes

Cardiac arrhythmias are associated with several cardiac diseases and are prevalent in people with or without structural and valvular abnormalities. Ventricular arrhythmias (VA) can be life threating and their onset require immediate medical attention. Similarly, atrial fibrillation and flutter lead to stroke, heart failure and even death. Optimal treatment of VA is variable and depends on the medical condition associated with the rhythm disorder (which includes reversible causes such as myocardial ischemia or pro-arrhythmic drugs). While an implanted cardioverter defibrillator is often indicated in secondary prevention of VA. This review highlights the newest advancements in these techniques and management of ventricular and atrial tachyarrhythmias, along with pharmacological therapy.

Inappropriate shock for myopotential over-sensing in a patient with subcutaneous ICD

Inappropriate ICD shocks are common adverse events; they are mainly due to supraventricular arrhythmias and secondly are related to noise, undersensing, oversensing, device malfunctions. We present a case of inappropriate device therapy due to myopotential oversensing in a patient with a subcutaneous ICD (s-ICD). A 58 years old male with an s-ICD during the device interrogation showed a previous episode of suspected sustained ventricular tachycardia at 210 bpm, which was effectively treated with ICD shock. The patient experienced the electrical shock while holding a big gas-cylinder in his arms. The EGM analysis revealed many irregular ventricular signals of low amplitude lasting for 24 s and interrupted by the shock. The device showed no malfunctions. This is the first case report of inappropriate S-ICD shock related to myopotential over-sensing. By recording intracardiac EGM, we demonstrated that the noise was created by the activity of the pectorals muscles.

Inappropriate pacing inhibition triggered by QT prolongation due to T wave oversensing in an ICD recipient presenting with long QT syndrome

Inappropriate inhibition of atrial pacing due to T-wave oversensing (TWOS) was observed in a patient presenting with congenital long QT syndrome, treated with an implantable cardioverter defibrillator (ICD) and beta-adrenergic blocker. Development of TWOS was associated with further QT interval prolongation in the absence of amplitude changes in the intracardiac T and R waves. Replacement of the ICD generator with a sensing filter designed to attenuate the intracardiac T wave suppressed TWOS and normalized the pacing functions.

Correlation between surface and intracardiac electrocardiogram in a patient with inappropriate defibrillation shocks due to hyperkalemia

A 39-year-old man received implantable cardioverter defibrillator (ICD) shocks during sinus rhythm, triggered by an increase in amplitude and oversensing of intracardiac T waves, caused by hyperkalemia. After treatment of hyperkalemia, the T wave morphology normalized, and oversensing and inappropriate ICD shocks were eliminated. Alteration of the intracardiac electrogram was well correlated to the surface electrocardiogram (ECG) changes. Intracardiac T waves can be altered by hyperkalemia and it seems that this alteration can be estimated by surface ECG analysis.

Non-pharmacological management of ventricular tachycardia

Ventricular tachyarrhythmias (VTA), a major cause of sudden cardiac death, require meticulous management in order to prevent recurrent episodes. Recently, non-pharmacological interventions, including radiofrequency catheter ablation and implantable cardioverter defibrillators (ICD), have become important treatments of VTA. Catheter ablation is curative in a relatively high percentage of patients presenting with idiopathic monomorphic ventricular tachycardia (VT). For VT associated with structural heart disease, however, the efficacy of catheter ablation remains limited, and ICD is the first-line therapy. In a subset of patients presenting with recurrent episodes of ventricular fibrillation (VF), catheter ablation is a therapeutic option when the VF is triggered by specific premature ventricular complexes. In Japan, unlike in the United States and Europe, ICD have not yet been accepted as first-line prevention of sudden cardiac death caused by VTA. The efficacy of ICD is occasionally limited by intolerable complications, such as electrical storm, inappropriate shock delivery and infection. Catheter ablation and ICD therapy might need to be combined for problematic cases.

Resolution of T-Wave Oversensing with Implantable Cardioverter Defibrillator Generator Replacement in an Adolescent

Inappropriate delivery of therapy due to T-wave oversensing is a frequent complication of intracardiac cardioverter defibrillators (ICD). A 16-year-old adolescent with congenital long QT syndrome type 3 underwent single-chamber implantable cardioverter defibrillator (ICD) (EnTrust VR, Medtronic Inc., Minneapolis, MN, USA) implantation.He received two appropriate and four inappropriate shocks. The inappropriate shocks were due to T-wave oversensing. Following the replacement of ICD with a different brand generator (Vitality 2 VR, Boston Scientific Inc., Natick, MA, USA), no more T-wave oversensing is noted. Proper filtering is imperative in ICDs in order to prevent T-wave oversensing-related inappropriate delivery of therapy.

An unusual mechanism causing inappropriate implantable cardioverter defibrillator shocks: transient reduction in R-wave amplitude

Inappropriate shocks delivered by the implantable cardioverter defibrillator (ICD) are an increasingly recognized complication. The most frequent cause is related to supraventricular rhythms associated with fast conduction to the ventricles that are incorrectly detected as ventricular tachycardia leading to inappropriate antitachycardia pacing and/or shocks. Oversensing is a frequent cause of inappropriate shocks usually due to increased amplitude of the T-wave secondary to ischaemia or electrolyte disorders that lead to T-wave double counting. We describe an unusual case of T-wave double counting during sinus rhythm caused by transient reduction in R-wave amplitude with no changes in T-wave amplitude resulting in inappropriate shocks.

Inappropriate ICD discharges due to “triple counting” during normal sinus rhythm

OBJECTIVE

To describe the clinical course of a patient with multiple ICD shocks in the setting of advanced renal failure and hyperkalemia.

METHODS

The patient was brought to the Electrophysiology Laboratory where the ICD was interrogated.

RESULTS

The patient was found to be hyperkalemic (serum potassium 7.6 mg/dl). Analysis of stored intracardiac electrograms from the ICD revealed "triple counting" (twice during his QRS complex and once during the T wave) and multiple inappropriate shocks. Correction of his electrolyte abnormality normalized his electrogram and no further ICD activations were observed.

CONCLUSION

Electrolyte abnormalities can distort the intracardiac electrogram in patients with ICD's and these changes can lead to multiple inappropriate shocks.

Decrease in amplitude of intracardiac ventricular electrogram and inappropriate therapy in patients with an implantable cardioverter defibrillator

Intracardiac electrograms are important for discrimination of tachyarrhythmia by implantable cardioverter defibrillators (ICD). A low R-wave can cause not only undersensing of ventricular tachyarrhythmia but also inappropriate discharges due to oversensing of unexpected signals because of its characteristic sensing algorithm. Therefore, this study aimed to investigate adverse events associated with R-wave amplitude. We included 115 consecutive patients followed-up over one year after implantation of a transvenous ICD system. The status of the ICD was checked every 3 months and intracardiac ventricular electrograms were analyzed. The decrease in R-wave amplitude was high in arrhythmogenic hypertrophy cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy (ARVC), and sarcoidosis. Low R-waves (< 5.0 mV) were observed in 13 patients at a follow-up of 15 +/- 16 months after implantation, and the mean R-wave was 3.0 +/- 0.8 mV. The frequency of low R-waves was high in ARVC (38%), sarcoidosis (33%), and dilated cardiomyopathy (17%). All of the dilated cardiomyopathy patients with low R-waves had severe left ventricular dysfunction. Inappropriate ICD therapy resulting from T-wave oversensing occurred in 7 patients and the R-wave was < 5.0 mV in 6 of the patients. The frequency of inappropriate therapy was high in patients with sarcoidosis. In 3 patients, inappropriate therapy caused ventricular tachyarrhythmia. In conclusion, decreases in R-wave amplitude occurred in some progressive cardiac disorders and caused inappropriate ICD discharges having arrhythmogenicity. Physicians should attempt to obtain a high R-wave amplitude during ICD implantation and careful follow-up is required, especially in patients with ARVC or sarcoidosis.

Inappropriate implantable cardioverter-defibrillator discharges unrelated to supraventricular tachyarrhythmias

AIMS

The development of implantable cardioverter-defibrillators (ICDs) with QRS morphology discrimination and dual-chamber sensing capabilities has improved the differentiation of supraventricular from ventricular tachycardias (VTs). Inappropriate ICD discharges may result from extracardiac signals caused by electromagnetic interference (EMI), because of electric fields and leakage currents from domestic or medical electrical devices, damaged sensing leads, and various cardiac and extracardiac signals that mimic VT and/or ventricular fibrillation. The aim of our study was to determine retrospectively the incidence and clinical relevance of these ICD behaviours and offer possible therapeutic solutions.

METHODS AND RESULTS

We have observed inappropriate discharges unrelated to supraventricular arrhythmias in 13 (3.9%) of the 336 patients implanted with ICDs in our centre from 1989 to 2005. Seven patients received inappropriate shocks following exposure to external EMI: improperly grounded electric stove, electrically powered watering system, hydro-massage bath, electrical pruner, electrocautery current during cardiac surgery, transcutaneous electric nerve stimulation. In four patients, spurious discharges were related to internal noise of the ICD system from inappropriate lead connections. In two cases, erroneous antitachycardia therapy was delivered following different body signals oversensing (T-wave oversensing, wide QRS double-counting and myopotentials). In nine patients, non-invasive solutions prevented further inappropriate therapies (avoidance of EMI, malfunctioning atrial lead exclusion, ventricular sensing reprogramming). In four patients, surgical revision of the system was required (lead connections or position revision).

CONCLUSION

In our experience, inappropriate ICD discharges unrelated to supraventricular arrhythmias occurred in about 4% of ICD patients. A careful evaluation of clinical data and telemetric information (lead impedance, sensed R-wave, stored electrograms) is essential in order to understand the nature of inappropriate ICD discharges and to select the most appropriate solution.

Inappropriate ICD Therapy: Does Device Configuration Make a Difference

INTRODUCTION

Inappropriate implantable cardioverter defibrillator (ICD) therapy (IT) is a common complication in patients with ICD. IT is commonly triggered by supraventricular tachycardias (SVT). Dual chamber ICDs (D-ICDs) may distinguish SVT from ventricular tachycardia/ventricular fibrillation better than single chamber ICDs (S-ICDs) and may be associated with a smaller incidence of IT.

METHODS

We reviewed the charts of 386 patients who had an ICD implanted for an AHA class I indication. Intracardiac electrograms were used to classify shocks as either appropriate or inappropriate.

RESULTS

Of 295 patients with an S-ICD, 66 (22.3%) received IT, compared to 5 (5.4%) of 91 patients with a D-ICD. The likelihood of being event-free at 1, 2, 3, and 4 years was 96.1%, 96.1%, 96.1%, and 89% for patients with D-ICD and 80.7%, 72.7%, 69.6%, and 66.4%, respectively, for patients with S-ICD (P < 0.001). Multivariate analysis showed no significant association with age, sex, history of atrial fibrillation, history of hypertension, or ejection fraction. SVTs were the commonest cause of IT in our patients.

CONCLUSION

Patients with D-ICD are less likely to receive IT as compared to patients with S-ICD.

[Avoidance of intermittent T-wave oversensing with device programming]

We report the case of a 35-year-old man who was suffering from severe heart failure due to cardiomyopathy. He underwent heart transplantation years ago and developed complex ventricular arrhythmias in the following months in combination with recurrent episodes of syncope due to hypertrophic non-obstructive cardiomyopathy in the transplanted heart, so a dual chamber ICD was implanted. Months later repetitive episodes of intermittent T-wave oversensing with consecutive activation of the ICD could be observed. Surgical revision of the electrode was performed and the patient was closely followed up. One year later, further episodes of T-wave oversensing led to multiple inappropriate IDC-shocks. A very short AV-conduction time was programmed to allow ventricular capture whenever possible, because T-wave oversense after ventricular capture would be annotated as single ventricular ectopy not resulting in antitachycardia pacing. As a consequence, the patient was free from inappropriate ICD-shocks, but showed several shorter episodes of T-wave oversensing. They were all initiated by atrial activity that was seen in the refractory period, thus leading to a loss of AV synchrony. Programming a very short post ventricular atrial refractory period (PVARP) in addition to a short AV-delay led to the complete disappearance of T-wave oversensing in this patient. During a 9-month follow-up, no further tachycardia episodes were detected by the device.

Frequency and causes of implantable cardioverter-defibrillator therapies: is device therapy proarrhythmic?

Implantable cardioverter-defibrillator (ICD) shocks diminish patients' quality of life, increase health care resource utilization, and may lead to other adverse sequelae. Better understanding of the factors that lead to ICD therapies, and better strategies to avoid unnecessary therapies, are needed to optimize patient outcomes. Data from major randomized clinical trials involving the use of ICDs and cardiac resynchronization therapy-defibrillator devices were reviewed to determine control group mortality rates, control group sudden death rates, and the frequency of appropriate and inappropriate ICD therapies. In all studies that classified deaths, appropriate ICD therapies outnumbered control group sudden cardiac deaths by a factor of 2 to 3. Some of these episodes can be explained by device programming, by the treatment of potentially unsustained tachycardias, and by errors of episode classification. Another underexplored possibility is that device therapy is proarrhythmic. Reasons for frequent therapies and methods to prevent them are discussed, as well as the notion of device proarrhythmia and the potentially detrimental effects of ICD shocks. These issues clearly affect the overall benefit of device therapy and have important implications for patient management and health care delivery.

Inappropriate ICD discharge due to T-wave oversensing in a patient with the brugada syndrome

Accurate sensing is an essential requirement for appropriate functioning of implantable cardioverter-defibrillator (ICD). T-wave oversensing remains as an annoying problem in currently available ICD. The Brugada syndrome with its inherent dynamic variations in electrophysiologic phenomena may complicate ICD therapy. We report a patient with diagnosis of Brugada syndrome who presented with frequent inappropriate therapy due to intermittent T-wave oversensing. This problem could not be eliminated by device reprogramming and necessitated implantation of a new sense/pace lead.

Congenital Short QT Syndrome and Implantable Cardioverter Defibrillator Treatment:. Inherent Risk for Inappropriate Shock Delivery

INTRODUCTION

A congenital short QT interval constitutes a new primary electrical abnormality associated with syncope and/or sudden cardiac death. We report on the initial use of implantable cardioverter defibrillator (ICD) therapy in patients with inherited short QT interval and discuss sensing abnormalities and detection issues.

METHODS AND RESULTS

In five consecutive patients from two unrelated European families who had structurally normal hearts, excessively shortened QT intervals, and a strong positive family history of sudden cardiac death, ICDs were placed for primary and secondary prevention. Mean QT intervals were 252 +/- 13 ms (QTc 287 +/- 13 ms). Despite normal sensing behavior during intraoperative and postoperative device testing, 3 of 5 patients experienced inappropriate shock therapies for T wave oversensing 30 +/- 26 days after implantation. Programming lower sensitivities and decay delays prevented further inappropriate discharges.

CONCLUSION

The congenital short QT syndrome constitutes a new clinical entity with an increased risk for sudden cardiac death. Currently, ICD treatment is the only therapeutic option. In patients with short QT interval and implanted ICD, increased risk for inappropriate therapy is inherent due to the detection of short-coupled and prominent T waves. Careful testing of ICD function and adaptation of sensing levels and decay delays without sacrificing correct arrhythmia detection are essential.

Inappropriate discharges by fourth generation implantable cardioverter defibrillators in patients with ventricular arrhythmias

The study prospectively investigated the incidence, cause and efficient management of inappropriate discharge by the fourth generation implantable cardioverter-defibrillator (ICD) system in 45 patients (mean age, 57+/-16 years). During the follow-up period of 27+/-17 months, 18 patients (40%) experienced one or more inappropriate therapies: sinus and supraventricular tachycardia (15 patients) and T wave oversensing (3 patients). In the 15 patients, re-programming of the tachycardia detection interval and/or additional treatment with beta-blocking agents were effective. In the 3 patients with T wave oversensing, the arrythmia was associated with an increase in T wave amplitude, change in T wave morphology and decreased R wave amplitude, and re-programming of the sensitivity of the local electrogram or changing the number of intervals to detect ventricular tachycardia decreased the number of inappropriate discharges in all 3 patients. In conclusion, inappropriate therapies are common problems in patients treated with the fourth generation ICD system, but most of them can be resolved using the dual-chamber ICD system. However, in patients with T-wave oversensing, it is difficult to avoid inappropriate discharge completely, even if the dual-chamber ICD system is implanted.