The implantable cardioverter-defibrillator

Effects and Complications of Subcutaneous Implantable Cardioverter-Defibrillator in the Prevention of Sudden Cardiac Death: A Narrative Review

An implantable cardioverter-defibrillator (ICD) is one of those devices that is a big boom for the prevention of sudden deaths due to heart failure. This particular device has been in use for just a couple of years, but its impact in the domain has brought about a considerable change in the way a specific issue of the cardiovascular system is tackled. Although subcutaneous or hypodermic implantable cardioverter-defibrillator (S-ICD) is considered to be a better alternative as far as transvenous implantable cardioverter-defibrillator (TV-ICD) is concerned, the former, being a newer introduction in the market, needs to be assessed in depth to clearly understand its effects and complications. Various types of research have been conducted on the efficacy of this device, and in most of the studies, the supremacy of this device is clearly evident when compared with other devices that are used for the same purpose. Better innovations in subcutaneous or hypodermic implantable cardioverter-defibrillators would enable them to be manufactured in a more efficient and cost-effective way so that a huge lot of people are benefited from this device. This review article is a whole peep into the various studies done in this domain, thereby providing adequate scientific insights about subcutaneous or hypodermic implantable cardioverter-defibrillators in a very simple and comprehensive manner.

Implantable Cardioverter Defibrillator Therapy and the Need for Concomitant Antiarrhythmic Drugs

Implantable cardioverter defibrillators (ICDs) are increasingly used for the prevention of sudden cardiac death in patients with life-threatening ventricular arrhythmias (VAs); however, there is a potential for severe and debilitating anxiety caused by symptoms associated with ICD therapy and anticipation of shocks. Anxiety is a psycho-logic stressor, including physiologic components that may lead to adrenergic excitation triggering new arrhythmias and ICD therapies. This often requires concomitant antiarrhythmic medication to reduce the frequency of shocks and symptomatic arrhythmias treated by anti-tachycardia pacing. Although published studies have documented the efficacy of currently available antiarrhythmics, they have limitations in patients with heart failure, may affect the defibrillation threshold, and/or have been associated with major side-effects. In conclusion, for the patient with an ICD experiencing symptomatic ventricular tachycardia (VTs) episodes or ICD shocks, there is a need for pharmacologic therapy to reduce the incidence of such events without affecting the performance of the ICD or causing major side-effects.

Safety of electronic apex locators and pulp testers in patients with implanted cardiac pacemakers or cardioverter/defibrillators

The purpose of this study was to determine if electronic apex locators (EAL) or electric pulp testers (EPT) interfere with the function of implanted cardiac pacemakers (ICP) or cardioverter/defibrillators (ICD). Twenty-seven patients with ICPs or ICDs had continuous electrocardiogram monitoring and device interrogation to detect interferences during the use of two types of EALs and one EPT. No interferences were detected by any ICP or ICD. In six patients, with intermittent pacing, a significant increase in pacing was observed during EAL/EPT stimulation (p < 0.05). Examination of RR intervals (a measure of intrinsic heart rate) demonstrated significantly longer RR intervals (slower intrinsic heart rate) during EAL/EPT stimulation (p < 0.05). Evaluation of the electrocardiograms for each patient failed to show any abnormalities in pacing during testing. These findings led us to conclude that the increased pacing frequency observed was related to a slower intrinsic heart rate and not electrical interference with the cardiac devices. In conclusion, the two EALs and one EPT used in this study did not interfere with the functioning of any of the cardiac devices tested.

Ventricular arrhythmias after LV remodelling: surgical ventricular restoration or ICD?

Ventricular arrhythmias cause ~50% of deaths in remodeled ventricles after myocardial infarction, and the Multicenter Automatic Defibrillator Implantation Trial (MADIT II) showed that the Implantable Cardioverter Defibrillator (ICD) saved lives in high risk coronary patients with advanced left ventricular dysfunction. We studied 382 patients with remodeled hearts by preoperative Ventricular stimulation (PVS) to evaluate surgical ventricular restoration (SVR) that excludes scar and lower ventricular volume alters the early and late arrhythmia process without ICD utilization.

METHODS

Clinical and hemodynamic results before and after SVR in post-infarction patients, are compared to contrast spontaneous and/or inducible ventricular tachycardia to patients without arrhythmias. Study arrhythmia groups included: Spontaneous in 87 patients with clinical documented ventricular arrhythmias and inducible or not inducible ventricular tachycardia: Inducible in 105 patients without clinical ventricular arrhythmias but PVS inducible ventricular tachycardia; and No arrhythmias in 190 patients without spontaneous or PVS inducible ventricular tachycardia.

RESULTS

Preoperative LV end systolic volume index helped define preoperative arrythmia potential: Spontaneous > 120/m(2), inducible > 100 ml/m(2), and none < 100ml/m(2). Overall operative mortality rate was 7.6% (29/382). Sudden cardiac death rate was 2.5% causing 18.7% of all deaths. Surgical management reduced inducible ventricular tachycardia, from 41% preoperatively (144/352) to 8% (26/307) at early study, and 8% (14/177) one year later. Cardiac mortality was low at 5-years and not different between groups, despite use of only one late ICD device.

CONCLUSIONS

Favorable electrical success rate and low mortality always included volume reduction to interrupt functional re-entry circuits, but also added endocardiectomy, cryoablation, CABG and mitral repair when needed. Overall SVR findings show volume and shape alteration limits ventricular arrhythmias that impair prognosis, and suggests ICD devices are not needed.

Shock Coil Failure Secondary to External Irradiation in a Patient with Implantable Cardioverter Defibrillator

The use of implantable cardioverter defibrillator (ICD) in the management of malignant ventricular arrhythmia is well established. Radiation treatment is common in malignant neoplasms, but the direct effect of irradiation in ICD is largely not well understood. We describe a case where radiation treatment probably led to shock coil failure.

Sudden cardiac death

Sudden cardiac death (SCD) due to ventricular tachyarrhythmias is a leading cause of death in the United States. This phenomenon is associated with coronary artery disease, valvular heart disease, nonischemic cardiomyopathies, congenital heart disease, primary electrical abnormalities, autonomic nervous system abnormalities, and other less common disorders. Evaluation and management of patients at risk for SCD (primary prevention) and of patients who have survived at least 1 episode of SCD (secondary prevention) have evolved in recent years because clinical trials have shown consistent benefit from implantation of cardioverter-defibrillators in appropriately selected patients. An evidence-based approach to primary and secondary prevention of SCD is presented.

Psychosocial impact of the implantable cardioverter defibrillator: nursing implications

Sudden cardiac death (SCD) remains a significant problem despite an overall reduction in other cardiac related deaths in recent years. Research supports the use of the implantable cardioverter defibrillator (ICD) as an effective means of treating dangerous ventricular tachydysrhythmias to prevent SCD. The issue that demands increasing attention is the psychologic experience of ICD recipients. Although the ICD is clearly a technological success, there is evidence that recipients experience strong physical and emotional reactions to the device. Such quality of life issues are worthy of a multidisciplinary effort directed at facilitating patient acceptance and adaptation to technology that although potentially life-saving, may also be unpredictable and anxiety provoking.

Surgical ventricular restoration in patients with postinfarction coronary artery disease: effectiveness on spontaneous and inducible ventricular tachycardia

Surgical ventricular reconstruction (SVR) involves resection of scar, septal exclusion, cavity reduction by endoventricular patch, and complete coronary grafting. At the Cardiothoracic Centre of Monaco, ventricular stimulation (PVS) is performed before SVR, unless contraindicated. In patients with spontaneous and/or inducible ventricular arrhythmias, nonguided endocardiectomy and cryosurgery are added. We report clinical and hemodynamic results after SVR in postinfarction patients, to compare management of patients with spontaneous and/or inducible ventricular tachycardia, with those without arrhythmias. The 3 subsets were: Group A, 87 patients with clinical documented ventricular arrhythmias and inducible or not inducible ventricular tachycardia (Spontaneous); Group B, 105 patients without clinical ventricular arrhythmias but with inducible ventricular tachycardia at PVS (Inducible); and Group C, 190 patients without spontaneous arrhythmias and not inducible ventricular tachycardia at PVS (No arrhythmias). Overall surgical mortality rate was 7.6% (29 of 382). Sudden death mortality was only 18.7% of all deaths. Surgical management caused marked reduction of inducible ventricular tachycardia, from 144 of 352 inducible ventricular tachycardia before surgery (41%), to 26 of 307 (8%) at early study, and 14 of 177 (8%) one year later. Cardiac mortality was low at 5 years, and not different among groups; this indicates that the surgical procedure limits the ventricular arrhythmias that normally impair prognosis in postinfarction dilated cardiomyopathy. We believe the favorable electrical success rate and low mortality are not linked to one aspect of the surgical procedure, but to an integrated approach that relieves ischemia (coronary bypass graft), and reduces left ventricular volumes (SVR) to improve pump function, and nonguided endocardiectomy plus cryoablation, to interrupt functional reentry circuits.