Prevalence and Management of Inappropriate Detection and Therapies in Patients with First-Generation Biventricular Pacemaker-Defibrillators

Upgrade to biventricular pacing in patients with pacing-induced heart failure: can resynchronization do the trick?

Dyssynchrony imposed on ventricular function by right ventricular (RV) apical pacing may lead in some cases to worsening or appearance of heart failure (HF) symptoms. This is a result of an altered pattern of activation, leading to several histological and functional adjustments of the left ventricle, including inhomogeneous thickening of the ventricular myocardium and myofibrillar disarray, fibrosis, disturbances in ion-handling protein expression, myocardial perfusion defects, alterations in sympathetic tone and mitral regurgitation. Studies of mid- and long-term effects of RV apical pacing on left ventricular (LV) function have demonstrated a progressive decline in ejection fraction and other indices of LV functional competence. Upgrading RV pacing systems to biventricular resynchronization modalities is a theoretically promising option for paced patients with worsening HF. The potentially favourable effect of upgrading on LV functional indices and patient clinical status has been demonstrated in few, non-randomized trials. Apart from the scantiness of existing clinical data, issues concerning technical aspects of the procedure and selection of eligible patients are raised. Is pacing-induced dyssynchrony equivalent to the indigenous dyssynchrony in unpaced patients with HF? What selection criteria should be applied in order to identify potential responders to cardiac resynchronization therapy in this patient population? Answers to these and more questions are still lacking.

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.

Progress in Cardiovascular Disease: Technical Considerations in Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) has been shown to improve symptoms, ventricular function, and survival in patients with left ventricular systolic dysfunction and ventricular conduction delay. Patients with moderate to severe drug-refractory heart failure symptoms along with ventricular dyssynchrony, manifested as prolongation of the QRS duration on the surface electrocardiogram, benefit from CRT. Owing to the growing awareness and application of CRT, a large number of patients have been identified as candidates for this therapy, making it necessary for clinicians involved in the care of such patients to be adequately knowledgeable of various aspects of CRT implementation. In particular, clinicians involved in the care of these patients must be aware of the practical considerations in preparing patients for the implantation procedure, careful surveillance for early or late procedure-related complications, and knowledge of the fundamental device features so as to tailor therapeutic and programming techniques to improve long-term response to CRT. This review addresses the technical considerations of the implantation procedure and device function with emphasis on the initial and long-term programming to ensure optimal delivery of CRT.

Cardiac Resynchronization Therapy: Strategies for Device Programming, Troubleshooting and Follow-Up

Cardiac resynchronization therapy (CRT) improves symptoms, exercise performance, ventricular function, and survival in patients with left ventricular dysfunction, prolonged QRS, and drug-refractory moderate to severe CHF. The growing application of CRT has created a large number of patients with complicated devices that need follow-up care from general practitioners, cardiologists, heart failure specialists and electro-physiologists. Optimal care of the CRT patient includes recognition and management of peri-implantation complications, optimal programming of atrio-ventricular and sequential ventricular timing, and troubleshooting device-related problems during long-term follow-up. A basic awareness of fundamental device features, the techniques to maximize the response to CRT, and an understanding of stored device data to track the response to therapy provide clinicians the ability to maximize clinical outcomes in the CHF patient. As evolving technology continues to increase the complexity of device therapies, clinicians must understand these therapies in order to properly treat heart failure patients. This work summarizes many of the issues involving early complications of CRT device implant, the strategies to optimize device function, and suggests a scheme for follow-up care of patients with CRT devices.