Current status of the implantable cardioverter-defibrillator

Innovations in the Neurosurgical Management of Epilepsy

Technical limitations and clinical challenges have historically limited the diagnostic tools and treatment methods available for surgical approaches to the management of epilepsy. By contrast, recent technological innovations in several areas hold significant promise in improving outcomes and decreasing morbidity. We review innovations in the neurosurgical management of epilepsy in several areas, including wireless recording and stimulation systems (particularly responsive neurostimulation [NeuroPace]), conformal electrodes for high-resolution electrocorticography, robot-assisted stereotactic surgery, optogenetics and optical imaging methods, novel positron emission tomography ligands, and new applications of focused ultrasonography. Investigation into genetic causes of and susceptibilities to epilepsy has introduced a new era of precision medicine, enabling the understanding of cell signaling mechanisms underlying epileptic activity as well as patient-specific molecularly targeted treatment options. We discuss the emerging path to individualized treatment plans, predicted outcomes, and improved selection of effective interventions, on the basis of these developments.

Applications of Electrical Pacing in the Body

Gastric electrostimulation by a pulse generator is an area of intense interest for the treatment of obesity. The concept of a rhythmic electrical current applied to neural or myal tissues has been established for the treatment of major problems in many areas of the body or is being investigated.

Postoperative Care of the Cardiac Surgical Patient

The subspecialty of interventional cardiology began in 1977. Since then, the discipline of interventional cardiology has matured rapidly, particularly with regards to ischemic heart disease. As a result, more patients are undergoing percutaneous catheter interventional therapy for ischemic heart disease and fewer patients are undergoing surgical myocardial revascularization. Those patients referred for surgical revascularization are generally older and have more complex problems. Furthermore, as the population ages more patients are referred to surgery for valvular heart disease. The result of these changes is a population of surgical patients older and sicker than previously treated.

A covariance-based algorithm: a novel technique for rhythm discrimination in ICDs

Inappropriate shocks due to misclassification of supraventricular and ventricular arrhythmias remain a major problem in the care of patients with Implantable Cardioverter defibrillators (ICDs). In this study we have investigated the ability of a new covariance-based algorithm, to distinguish Ventricular Tachycardia from other rhythms such as Supraventricular Tachycardia. The proposed algorithm has a low computational demand and with a small adjustment is applicable on both single-chamber and dual-chamber ICDs. The results are promising and suggest that the new covariance-based algorithm may be an effective method for ICD rhythm classification and may decrease inappropriate shocks.

A new approach for ICD rhythm classification based on support vector machines

Inappropriate shocks due to misclassification of supraventricular and ventricular arrhythmias remain a major problem in the care of patients with Implantable Cardioverter Defibrillators (ICDs). The purpose of this study was to investigate the ability of a new covariance-based support vector machine classifier, to distinguish ventricular tachycardia from other rhythms such as supraventricular tachycardia. The proposed algorithm is applicable on both single and dual chamber ICDs and has a low computational demand. The results demonstrate that suggested algorithm has considerable promise and merits further investigation.

Stability and cause of anxiety in patients with an implantable cardioverter-defibrillator: A longitudinal two-year follow-up

OBJECTIVE

Several investigations have found that anxiety disorders often develop in patients with an implantable cardioverter-defibrillator (ICD). This study investigated the inter--and intraindividual stability of anxiety and its relation to ICD activity in patients with an ICD.

METHODS

Changes in the psychopathology of 35 patients with an ICD were assessed at the beginning of the trial period and 2.5 years later. Psychometric measures of anxiety were collected. During this period, shocks and antitachycardia pacing were assessed.

RESULTS

Anxiety was found to be interindividually stable. We also found a slight, but statistically significant, reduction in trait anxiety and avoidance behavior over time. Patients who experienced shocks or antitachycardia pacing did not differ on psychometric or demographic variables from patients without those events.

CONCLUSIONS

Anxiety seems to be interindividually stable in patients with an ICD. We found no connection between anxiety and tachycardia episodes in patients with an ICD.

Implantable cardioverter defibrillator algorithms: status review in terms of computational cost

In recent decades, implantable cardioverter defibrillators (ICDs) have improved substantially, becoming the treatment of choice for patients at high risk of life-threatening arrhythmias. Nevertheless, inappropriate shock therapy for non-ventricular arrhythmias is still a problem. Extending the ICD battery lifetime demands very low power consumption, which is obtained at very low microprocessor clock frequencies. Currently, some high-performance algorithms remain beyond the computational capabilities of ICDs. Future ICDs with higher computing power will permit the implementation of computationally intensive algorithms, enhancing the discrimination performance and preventing inappropriate shock therapies. An ICD algorithm status review is presented from the point of view of signal processing techniques and their computational costs. Several examples of discrimination algorithms with increasing computational cost are analyzed. Whereas some of them are already used in commercial ICDs, other algorithms cannot be implemented yet in current ICDs. A solution based on dynamic adaptation of microprocessor power consumption to meet algorithm computational requirements is proposed. This solution allows implementation of complex discrimination algorithms in ICDs without significantly increasing the power consumption.

Follow-up X rays play a key role in detecting implantable cardioverter defibrillator lead fracture: a case of incessant inappropriate shocks due to lead fracture

A patient with an implantable cardioverter defibrillator (ICD) received incessant inappropriate shocks due to a lead fracture 3 years after implantation. Routine lead measurements at 3-month intervals had shown no abnormal findings even at the most recent measurement performed 2 months prior to the event. In contrast, serial observation of chest X rays clearly disclosed progressive lead narrowing starting 11 months prior to the event. This case indicates the importance of the routine chest X rays in long-term follow-up of ICDs and sets a precedent for interpreting lead narrowing in such X rays.

Algorithms for better arrhythmia discrimination in implantable cardioverter defibrillators

The discrimination of concomitant atrial tachyarrhythmias and sinus tachycardias in patients with malignant ventricular tachyarrhythmias is a major challenge for new defibrillator devices. Different algorithms have now been established to distinguish between atrial and ventricular tachyarrhythmias. Furthermore, new dual-chamber implantable defibrillators are capable of tiered atrial therapies for both regular and irregular atrial and ventricular tachyarrhythmias. The increasingly complex and subtle dual-chamber detection algorithms have proven to be safe and effective for the detection of ventricular tachycardia, and also in terms of an increase in specificity and a reduction in inappropriate ventricular therapies for supraventricular tachyarrhythmias. Stable electrode position, and a continuous and correct atrial signal quality, are prerequisites for atrial therapies and algorithms for arrhythmia discrimination.