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PubMed2006

Real-time assessment of acute myocardial ischaemia by an intra-thoracic 6-lead ECG: evaluation of a new diagnostic option in the implantable defibrillator.

AIM: In the presence of coronary artery disease, implantable cardioverter-defibrillators (ICD) are used effectively for treating life-threatening tachyarrhythmias. Continuous monitoring of myocardial ischaemia would provide a new diagnostic option in future ICD generations. METHODS AND RESULTS: In 22 selected patients undergoing coronary angioplasty, percutaneous transluminal coronary angioplasty (PTCA), three electrodes, similar to those used in the ICD, were inserted aiming to create six intra-thoracic ECG (IT-ECG) leads according to Einthoven and Goldberger. In total, 27 PTCA were conducted. The diagnostic efficacy for ischaemia assessment was compared with the surface ECG. The IT-ECG proved to be more sensitive than conventional ECG in early and overall ischaemia assessment. At 30 s of coronary artery occlusion, ischaemic ST-segment alterations (> or =0.25 mV) were present in the IT-ECG 2.3 times more often (23 vs. 10/27 PTCA attempts, P<0.01) and at 90 s 1.4 times more often compared with conventional ECG leads (18 vs. 26/27, P<0.05). Intra-thoracic Einthoven 2 (SVC+RVA vs. ICD-housing) and Goldberger 3 (SVC+ICD-housing vs. RVA) had the highest sensitivity (88/85%). Using > or =4 IT-ECG, ischaemia monitoring was independent of severity and site of origin. IT-ECG signals showed double ST-T signal amplitude (4.19+/-0.6 vs. 2.15+/-0.3 mV, ratio: 1.95, P<0.01) at a QRS/ST amplitude ratio similar in the two ECG techniques. CONCLUSION: This study provides strong evidence that the ICD-based IT 6-lead ECG would provide a new and efficient means of assessing a patient's daily ischaemic burden.

Computer Systems↗
PubMed2001

Electrical storm presages nonsudden death: the antiarrhythmics versus implantable defibrillators (AVID) trial.

BACKGROUND: Electrical storm, multiple temporally related episodes of ventricular tachycardia (VT) or ventricular fibrillation (VF), is a frequent problem among recipients of implantable cardioverter defibrillators (ICDs). However, insufficient data exist regarding its prognostic significance. METHODS AND RESULTS: This analysis includes 457 patients who received an ICD in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial and who were followed for 31 +/- 13 months. Electrical storm was defined as > or = 3 separate episodes of VT/VF within 24 hours. Characteristics and survival of patients surviving electrical storm (n = 90), those with VT/VF unrelated to electrical storm (n = 184), and the remaining patients (n = 183) were compared. The 3 groups differed in terms of ejection fraction, index arrhythmia, revascularization status, and baseline medication use. Survival was evaluated using time-dependent Cox modeling. Electrical storm occurred 9.2 +/- 11.5 months after ICD implantation, and most episodes (86%) were due to VT. Electrical storm was a significant risk factor for subsequent death, independent of ejection fraction and other prognostic variables (relative risk [RR], 2.4; 95% confidence interval [CI], 1.3 to 4.2; P = 0.003), but VT/VF unrelated to electrical storm was not (RR, 1.0; 95% CI, 0.6 to 1.7; P = 0.9). The risk of death was greatest 3 months after electrical storm (RR, 5.4; 95% Cl, 2.4 to 12.3; P = 0.0001) and diminished beyond this time (RR, 1.9; 95% CI, 1.0 to 3.6; P=0.04). CONCLUSIONS: Electrical storm is an important, independent marker for subsequent death among ICD recipients, particularly in the first 3 months after its occurrence. However, the development of VT/VF unrelated to electrical storm does not seem to be associated with an increased risk of subsequent death.

Aged↗
PubMedDate not supplied

Outcome criteria for patients with implantable defibrillators.

Specific outcome criteria that the implantable cardioverter defibrillator (ICD) patient needs to demonstrate before discharge are the basis for independent and collaborative nursing interventions. The authors describe specific outcome criteria for teaching ICD patients.

Electric Countershock↗
PubMed2004

Implications of cardiac resynchronization therapy and prophylactic defibrillator implantation among patients eligible for heart transplantation.

This study analyzed the relations and time-related changes in eligibility for cardiac resynchronization therapy and prophylactic defibrillator implantation in 161 potential candidates for heart transplantation. Although up to 62% of patients who fulfilled the severity criteria for heart transplantation were eligible for either device, this percentage increased as clinical/instrumental parameters of heart failure severity worsened.

Adult↗
PubMed2006

A fiber optic sensor system for control of rate-adaptive cardiac pacemakers and implantable defibrillators.

Commercially available cardiac pacemakers and implantable cardioverters/defibrillators (ICDs) predominantly use an intracardiac-derived electrocardiogram (ECG) for the detection of arrhythmias. To achieve automatic control of the heart frequency in accordance with cardiovascular strain and improved detection of life-threatening arrhythmias, it is desirable to monitor the heart by an input signal correlated with the hemodynamic state. One possible approach to derive such a signal is to measure the inotropy (mechanical contraction strength of the heart muscle). For this purpose, an optoelectronic measurement system has been designed. The fundamental function of the system has been shown in earlier investigations using an isolated beating pig heart. In this paper the design of two algorithms for use in pacemakers and ICDs based on a fiber optic sensor signal is presented.

Algorithms↗
PubMed1988

Absence of significant postdefibrillation bradyarrhythmias in patients with automatic implantable defibrillators.

Because postdefibrillation bradycardia or asystole is of clinical concern in patients with implanted automatic cardioverter defibrillators, we analyzed the cardiac rhythm after 157 intraoperative defibrillations in 50 patients undergoing implantation of the device. Factors that could influence the heart rhythm immediately after defibrillation were also analyzed. The postdefibrillation heart rate and the duration of postdefibrillation asystole did not correlate with age, conduction abnormalities, type or duration of arrhythmia before defibrillation, delivered energy, lead system, or left ventricular ejection fraction, but they did correlate with the resting preoperative heart rate and the concomitant performance of coronary artery bypass surgery at the time of defibrillator implantation. Temporary pacing (for prolonged asystole) was required in only two patients, both of whom had also undergone bypass surgery. Fourteen patients being treated with amiodarone had slower resting and postdefibrillation heart rates, but the mean duration of posdefibrillation asystole was similar to that seen in patients not receiving any antiarrhythmic medication. On follow-up, 25 monitored and 178 unmonitored automatic defibrillator discharges occurred in 24 patients, without evidence of symptomatic postdefibrillation bradyarrhythmias. Thus significant postdefibrillation bradyarrhythmias were uncommon, but when such a propensity existed it could not be predicted reliably on clinical grounds alone.

Adult↗
PubMed2003

Eligibility for biventricular pacing in patients with an implantable cardioverter defibrillator.

Implantable cardioverter defibrillator (ICD)-therapy prevents sudden death in patients at high risk, but incidence of death due to heart failure remains unaltered. Recent data suggest that biventricular (BV) pacing is useful in patients with heart failure. It is unclear, how many patients with an ICD indication may have an indication for BV pacing. Therefore all patients who received an ICD were analyzed for eligibility of BV pacing using the following criteria: NYHA class III or IV, QRS duration >120 ms, depressed LVEF. Three hundred and ninety consecutive patients received an ICD from June 1996 to March 2001. Underlying disease was ischemic heart disease in 66%. In the 390 patients the mean LVEF was 36+/-17%, 20% were in NYHA class III-IV and 16% were in NYHA class II with an LVEF <30%. Of these 140 patients, 79 had a QRS duration >120 ms. Thus, 79 (20%) patients were eligible for BV pacing in addition to ICD-therapy. Patients who received a BV pacemaker in addition to ICD-therapy had a superior survival, improved in NYHA class and showed a significantly lower hospitalization rate as compared to patients who received an ICD only. Screening for eligibility of BV pacing may be considered in patients with CHF scheduled for ICD implantation.

Aged↗
PubMed2005

Pre-procedure duplex ultrasonography to assist cephalic vein isolation in pacemaker and defibrillator implantation.

BACKGROUND: Difficulty in isolating the cephalic vein contributes to failed pacemaker and intracardiac cardioverter-defibrillator (ICD) implantation via the cephalic venous approach. The deltopectoral groove is used as a rough landmark, but the vein is often not found here. We evaluated the benefit of pre-procedural duplex ultrasonography in isolating the cephalic vein. METHODS: We enrolled 80 consecutive patients undergoing new pacemaker or defibrillator implantation and performed duplex ultrasonography to localize the cephalic vein before implantation. The corresponding surface location in the infraclavicular region and the depth of the cephalic vein were identified and recorded if the vein was well visualized. Using the imaging results, we dissected the skin over the predicted location until the cephalic vein was isolated. We determined the depth and corresponding surface location of the proximal cephalic vein during surgery. Afterward, we compared localization of the vein using imaging, surgery, and the deltopectoral-groove method. The relationship between cephalic vein depth and body parameters was also evaluated after the procedure. RESULTS: All proximal cephalic veins were successfully isolated under the assistance of pre-procedural duplex ultrasonography. When the corresponding surface locations were compared, the location depicted on sonograms was closer to the surgical finding than the location determined by using the deltopectoral-groove method (0.5 +/- 3.9 vs. 4.9 +/- 9.6 mm; P < .001). The depth of the cephalic vein derived from duplex sonograms showed excellent correlation with the surgical findings (r = 0.93, P < 0.001). The cephalic vein depth and body mass index (BMI) also showed a linear relationship with good correlation (r = 0.70, P < 0.001). CONCLUSION: Pre-procedural duplex ultrasonography helped in localizing the proximal cephalic vein and isolating the cephalic vein. Surface localization of the proximal cephalic vein was superior with sonography than with the deltopectoral-groove method. There was a linear relationship with good correlation between BMI and cephalic vein depth.

Adult↗
PubMed2000

Subpectoral cardioverter-defibrillator implantation using a lateral approach.

INTRODUCTION: Third-generation cardioverter-defibrillators have revolutionized management of ventricular tachyarrhythmias. Implantation can be performed in the electro-physiology laboratory, with minimal morbidity. Generator size has shrunk to the point that subcutaneous implantation is feasible and safe, even under local anesthesia. The prepectoral technique, however, is associated with increased mechanical stress to the subcutaneous tissue and can predispose to device erosion or infection. These complications may be avoided by submuscular placement. Among subpectoral techniques, the lateral approach offers unrestricted ability to deploy patches or array electrodes, should the need arise, and may represent the optimal implant technique under some circumstances. METHODS: We studied 29 male patients, aged 29-78 years, who presented with syncope or sustained ventricular tachycardia, and underwent subpectoral defibrillator implantation under general anesthesia or conscious sedation. All devices were third-generation active can systems with biphasic shock capability. Six dual-chamber defibrillators were used. RESULTS: Subpectoral implantation was successful in all cases, with an estimated blood loss of 28+/-17 mL and no immediate complications. Except for one patient who developed twiddler's syndrome and ultimately required revision to a subcutaneous pocket, the implant site was tolerated well, and no limitation in the range of motion of the upper limb was observed during 20 months of follow-up. CONCLUSIONS: Subpectoral implantation using a lateral approach is technically straightforward and can be applied globally, with modest additional resource and equipment requirements. Familiarity with this approach can maximize the likelihood of successful defibrillator implantation in the electrophysiology laboratory.

Adult↗
PubMed2006

Implantable defibrillator early after primary percutaneous intervention for ST-elevation myocardial infarction: rationale and design of the Defibrillator After Primary Angioplasty (DAPA) trial.

BACKGROUND: It has been shown that an implantable cardioverter defibrillator (ICD) may be beneficial when added to optimal drug treatment in patients with reduced left ventricular function who survive a myocardial infarction (MI). However, it is not known whether patients with increased risk of death after primary percutaneous coronary intervention (PCI) for ST-elevation MI also have benefit of prophylactic ICD therapy to reduce sudden cardiac death. METHODS AND STUDY DESIGN: The DAPA trial is designed to evaluate the efficacy and safety of ICD in high-risk patients after primary PCI for ST-elevation MI. In this randomized multicenter controlled study, a total of 700 patients will be included. Enrolment started in October 2004. Inclusion criteria are thrombolysis in myocardial infarction flow less than 3 after primary PCI or left ventricular ejection fraction lower than 30% as measured short after admission for the index MI. Patients will be randomized between 30 and 60 days after their MI. The primary end point will be total death during the follow-up period of at least 3 years for each patient. CONCLUSIONS: This multicenter trial of patients at high risk of death after primary angioplasty for ST-elevation MI will evaluate prophylactic ICD therapy in addition to the current standard of care.

Adult↗
PubMed1993

Failure of one conductor in a nonthoracotomy implantable defibrillator lead causing inappropriate sensing and potentially ineffective shock delivery.

We describe how a single defect in a new model transvenous lead for an implantable cardioverter defibrillator can result in malfunction of the sensing and defibrillation circuits. The patient had received shocks during atrial fibrillation without premonitory symptoms. At least one shock was delivered and not felt by the patient. In addition, late in the course, a shock was delivered during atrial fibrillation documented to be with a slow ventricular response. In the transvenous lead, a distal spring functions as the anode for rate sensing and the cathode for defibrillation. The wire from this spring bifurcates near the proximal end of the catheter. One wire from the bifurcation leads to the positive (anode) rate-sensing socket of the pulse generator, and the other wire leads to the negative (cathode) high voltage output socket of the defibrillator for defibrillation and cardioversion. After the inappropriate and unperceived shocks were documented, intraoperative and postoperative electrical testing indicated that intermittent discontinuity of the distal spring system within the proximal yoke of the catheter caused faulty sensing and potentially unreliable defibrillation. This dual malfunction was possible because the distal spring of the lead functions in the high-voltage output and the rate-sensing low-voltage input circuits of the implantable defibrillator.

Defibrillators, Implantable↗
PubMed1995

Transvenous defibrillator implantation in patients with persistent left superior vena cava and right superior vena cava atresia.

In this report a transvenous cardioverter defibrillator implantation is described in two patients with a persistent left-sided superior vena cava and right SVC atresia. In the first case, manoeuvring of the guide wire inserted through the left subclavian vein into the SVC proved impossible, revealing a left SVC originating from the left brachiocephalic vein with an acute corner. Changing the side of implantation and inserting a CPI Endotak catheter through the right subclavian vein, the lead was easily advanced through the left SVC into the coronary sinus and then into the right atrium with the tip abutting the lateral atrial wall. Subsequent manoeuvres allowed passage of the tip of the catheter into the right ventricular apex with the proximal defibrillation coil of the Endotak lead in the low left SVC, with its distal limit at the junction with the coronary sinus. A biphasic waveform single pathway RV - > left SVC successfully defibrillated with a stored energy of 5 J. In the second patient, implantation of a transvenous Medtronic system was possible from a left infraclavicular approach. A tripolar RV coil was inserted into the right ventricle via the persistent left SVC and contiguous coronary sinus. Because of the acute angle required to enter the RV in this second case, the RV lead was looped in the right atrium in order to enter the RV in a satisfactory, albeit atypical RV location. This patient was successfully defibrillated with a 5 J monophasic waveform delivered between the RV coil, a CS/left SVC coil, and a subcutaneous patch. In conclusion, both of these patients illustrate the ability to use transvenous ICDs successfully in patients with persistent left superior vena cava although the implantation technique deviates substantially from traditional methods.

Adolescent↗
PubMed2003

[Treatment with implantable defibrillator].

About 20 years ago the first patient received an implantable cardioverter defibrillator (ICD), and since then the number of implants have increased dramatically. The ICD can terminate ventricular fibrillation and ventricular tachycardia. Studies of secondary prophylaxis show that ICD treatment can improve the prognosis of patients who have survived cardiac arrest. Prophylactic ICD treatment in patients who have not had cardiac arrest is only recommended for selected groups. Patients with poor left ventricular function seem to benefit the most and ongoing trials should elucidate the possible benefit from prophylactic ICD treatment in heart failure patients. The purpose of this article is to describe the development in ICD treatment and give a survey of the present indications for ICD treatment.

Defibrillators, Implantable↗
PubMed1993

The implantable defibrillator and antiarrhythmic drugs--competitive and complementary treatment for severe ventricular arrhythmia.

Most patients with a history of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) are at high risk of recurrence. Implanted defibrillators (ICDs) are highly effective in sensing and converting VT or VF to a perfusing rhythm. "Conventional" antiarrhythmic agents, which primarily block cardiac sodium channels, are relatively ineffective in preventing arrhythmia recurrence; amiodarone and sotalol appear to be effective in reducing recurrence and mortality rates, although the extent of benefit is not well understood. Despite the apparent advantage of ICDs, they have short- and long-term complications, are costly, and their benefit in prolonging the quantity or quality of life remains unproven. Randomized clinical trials which compare the effect of ICDs with that of antiarrhythmic drugs on mortality, cost, and quality of life will be necessary to understand how patients with malignant arrhythmias ought to be treated. If an ICD is implanted, adjunctive therapies need to be considered to treat the underlying heart disease and to derive optimum benefit from the device. Drugs may have beneficial or adverse interactions with devices, and the full understanding of these interactions requires further study.

Amiodarone↗
PubMed1998

Implantable defibrillator diagnostic storage capabilities: evolution, current status, and future utilization.

There has been a rapid and significant evolution in the stored diagnostic information available from implantable cardioverter defibrillators (ICDs). The diagnostic information available in current generation ICDs has greatly enhanced the clinicians' ability to determine the rhythm triggering device therapy as well as to identify potential problems with the ICD system. Furthermore, this information may be useful in identifying triggers of ventricular arrhythmias in patients at high risk for sudden death. The history, evolution, value, and limitations of the stored diagnostic capabilities of implantable defibrillators are discussed.

Arrhythmias, Cardiac↗
PubMed1999

Implantable cardioverter-defibrillators.

Implantable defibrillators have become the dominant therapeutic modality for patients with life-threatening ventricular arrhythmias. Current defibrillators are small (<60 mL) and implanted with techniques similar to standard pacemakers. They provide high-energy shocks for ventricular fibrillation and rapid ventricular tachycardia, antitachycardia pacing for monomorphic ventricular tachycardia, as well as antibradycardia pacing. Newer devices incorporating an atrial lead allow dual-chamber pacing and better discrimination between ventricular and supraventricular tachyarrhythmias. Randomized controlled trials have shown superior survival with implantable defibrillators than with antiarrhythmic drugs in survivors of life-threatening ventricular tachyarrhythmias and in high-risk patients with coronary artery disease. Complications associated with implantable defibrillator therapy include infection, lead failure, and spurious shocks for supraventricular tachyarrhythmias. Most patients adapt well to living with an implantable defibrillator, although driving often has to be restricted. Limited evidence suggests that implantable defibrillator therapy is cost-effective when compared with other widely accepted treatments. The use of implantable defibrillators is likely to continue to expand in the future. Ongoing clinical trials will define further prophylactic indications of the implantable defibrillator and clarify its cost-effectiveness ratio in different clinical settings.

Clinical Trials as Topic↗
PubMed1998

Can implantable defibrillators reduce non-arrhythmic mortality?

Several authors have made the intriguing observation that Implantable Cardioverter Defibrillators (ICD) appear not only to reduce sudden deaths, but also mortality due to non-arrhythmic causes. Studies have shown that this observation can not be attributed to patient selection bias. In trying to explain this apparent anomaly, it should be noted that two treatment strategies are being compared. Thus, it might be that, under certain circumstances, antiarrhythmic drugs contribute to non-arrhythmic deaths, not that ICDs reduce them. There appear to be some plausible explanations for this phenomenon, e.g., the long-term effect on cardiac function of episodes of ventricular tachycardia lasting for several hours for patients treated solely by antiarrhythmic drugs, compared to their quick termination by an ICD. However, further research into this curious mode of death issue is needed, and may provide further insights into patient populations deriving greatest benefit from one therapy or the other.

Anti-Arrhythmia Agents↗