ICD clinical update: first decade, initial 10,000 patients

Implantable cardioverter-defibrillator placement in patients with mild-to- moderate left ventricular dysfunction: hemodynamics and recovery profile with two different anesthetics used during deep sedation

OBJECTIVE

To compare the effects of thiopental and propofol during defibrillation threshold testing (DFT) on hemodynamics and recovery profile in patients requiring automatic internal cardioverter-defibrilator placement.

DESIGN

Prospective clinical investigation.

SETTING

University hospital.

PARTICIPANTS

Thirty-four adult patients.

INTERVENTIONS

After administration of midazolam, 0.025 mg/kg, and fentanyl, 0.5 to 1 mug/kg, surgery was performed under topical infiltration with 1% lidocaine. In group I (GI) (n = 17), patients received thiopental by slow injection and patients in group II (GII) (n = 17) received propofol before induction of ventricular fibrillation (VF).

MEASUREMENTS AND MAIN RESULTS

Patients received 4.1 +/- 1.4 mg of midazolam, 114 +/- 34 mug of fentanyl, and 280 +/- 78 mg of thiopental in GI; and 4.6 +/- 1.7 mg of midazolam, 119 +/- 62 mug of fentanyl, and 147 +/- 40 mg of propofol in GII (p > 0.05). Hemodynamics did not show significant differences between the groups at any recording time. Average time needed to regain the pretest sedation level was 16.4 +/- 8.8 minutes in GI and 10.9 +/- 5.5 minutes in GII (p = 0.03). Time required to achieve a score of 10 using a modified Aldrete score was 26.4 +/- 9.3 minutes in GI and 17.4 +/- 4.9 in GII (p = 0.001). Seven patients in GII (41%) and 1 patient in GI (6%) became hypotensive after DFT (p = 0.04).

CONCLUSIONS

Deepening the sedation level by slow injection of thiopental or propofol before DFT provided satisfactory conditions during brief episodes of VF. Delay in recovery of arterial pressure after DFT with propofol and delay in arousal and discharge of patients with thiopental are major disadvantages of the regimens.

Geographic differences in implantable cardioverter defibrillator usage

Despite the demonstrated efficacy of implantable cardioverter defibrillators (ICDs) in reducing sudden and total mortality in selected patients, their implantation rates vary greatly among countries. In the United States, the implantation rate is 185 implants per million inhabitants compared with only 31 implants per million in western Europe. The differences in ICD use may be explained by the following factors: manner in which sudden cardiac death is perceived by politicians and physicians (sudden cardiac death is perceived as a "nice way of dying"); differences in indications; physicians' information; prevalence of coronary artery disease; sudden cardiac death survival rates; perceived reliability of alternative treatment (namely, antiarrhythmics including amiodarone); economic backgrounds; and health care politics. Furthermore, the cost of this treatment strategy must be considered. This issue has been raised because generalization of ICD use in patients matching clinical characteristics of patients enrolled in the primary prevention trials may represent a significant economic burden to be added to the already overloaded health care system. This low acceptance may not be entirely related to budget constraint but also to the perceived efficacy of ICDs by physicians and health authorities.

Temporal and geographical trends in indications for implantation of cardiac defibrillators in Europe 1993-1998. Medtronic ICD System Investigators

Despite the demonstrated efficacy of implantable cardioverter defibrillators (ICDs) in reducing sudden and total mortality in selected populations, their implantation rates vary greatly between countries. The aim of our study was to analyze temporal and geographical trends in ICD implantations in countries with similar health related expenditure in Western Europe. A total of 2,257 patients from ten European evaluation studies of Medtronic defibrillators and defibrillation electrodes, conducted between 1993 and 1998, representing 12 countries, was included in this analysis. Rates of implantation and clinical characteristics were compared between countries and years of implantation. Rates of implantation differed greatly between Western European countries and did not correlate with indices of health related expenditure (i.e., number of patients per physician and number of patients per hospital bed). However, there was a strong and statistically significant negative correlation between the use of amiodarone and the rates of implantation (r = -0.66, P = 0.02). Temporal trends showed a significant increase in the age of the patients receiving an ICD between 1993 and 1998 (57 +/- 14 vs 61 +/- 12 years, mean +/- SD, P < 0.001). There was also a temporal trend towards an increased incidence of coronary artery disease and a significant decrease in the incidence of cardiomyopathy. There was a temporal increase in implantations in patients with a history of ventricular tachycardia. Despite a general scientific agreement that ICDs are a first line treatment for patients at high risk of sudden cardiac death, their acceptance remains low in several developed countries. This low acceptance may not be entirely related to budget constraint but may also be related to their perceived efficacy by physicians and health authorities.

Influence of anaesthesia on defibrillation threshold

Internal cardioverter-defibrillator implantation can be performed under local or general anaesthesia. Whether the technique of general anaesthesia influences the defibrillation threshold remains a matter of debate. We therefore compared, in a prospective, randomised clinical study, the effect of intravenous anaesthesia using propofol with inhalational anaesthesia using isoflurane on the defibrillation threshold in 68 patients scheduled for transvenous single-lead internal cardioverter-defibrillator implantation. Defibrillation threshold was measured at implantation and at device testing 1 week and 1 month after implantation. Patients acted as their own controls. Neither the anaesthetic technique nor the duration of anaesthesia was associated with significant changes in the defibrillation threshold. We conclude that in this group of high-risk patients, both types of anaesthesia are acceptable techniques for internal cardioverter-defibrillator implantation and testing.

Effects of early defibrillation by ambulance personnel on short- and long-term outcome of cardiac arrest survival: the Munich experiment

OBJECTIVES

This study evaluates the feasibility of implementing early defibrillation of out-of-hospital cardiac arrest patients for basic life-support providers (EMT-D) in a two-tier emergency system in the city of Munich, Germany.

DESIGN

Retrospective consecutive analysis of all EMT-D attempts during a 5-year initiation phase (1990 to 1994) and prospective follow-up of all cardiac arrest survivors discharged from hospital.

SETTING

A strictly defined inner-city and suburban area of 978 km2 and a residential population of 1,530,000 inhabitants with 22 ICUs in urban hospitals. One dispatching center to alert a two-tier emergency system with 56 EMT-D-staffed ambulances and physician-staffed mobile ICUs stationed at the nearest of nine hospitals.

METHODS

AH EMT-D cases were identified and data on patients were documented in a standardized manner from patients' records, including the resuscitation protocol in the hospitals to which the patients were referred. For those patients discharged from the hospital, a standardized telephone interview was undertaken with the physician in charge of the patient and with the patient/relative leading to an assessment of the patient's status according to the Glasgow-Pittsburgh cerebral performance categories.

INTERVENTION

None.

RESULTS

During the 5-year initiation phase of the EMT-D program in the two-tier emergency system in Munich, there were 243 resuscitation attempts by EMTs, using the semiautomated defibrillator; 125 patients died immediately on the scene. In 118 patients, spontaneous circulation was reestablished and these patients were admitted to an ICU in 1 of the 22 urban hospitals. Median call-response interval for the EMT-D was 5 min (interquartile range, 3 to 6) and was 10 min (interquartile range, 7 to 13) for the second tier (p < or = 0.0001). In 34 cases (28.8%), EMT-D staff had reestablished spontaneous circulation (ROSC) before the second tier arrived on the scene. Patients with ROSC on the arrival of the second tier were more frequently discharged alive from hospital than were patients without ROSC at that time (p < or = 0.0001). The hospital discharge rate of initially successful resuscitated patients presenting with out-of-hospital ventricular fibrillation was 38.1% (45/118). Overall success rate of all EMT-D attempts was 18.5% (45/243). After a mean follow-up time of 39 (range, 22 to 64) months, 29 (66%) patients were still living. Twenty-five (56.8%) were neurologically not disabled or mildly disabled (CPC 1/2); disability was moderate in 3 (6.8%) patients and was severe in 1 (2.3%) patient. One case was lost to follow-up.

CONCLUSION

The present study demonstrates that the upgrading of basic life support providers with semiautomated defibrillators has a significant benefit for cardiac arrest victims outside the hospital in an urban environment.

Automatic internal cardioverter-defibrillator patch erosion into the upper airway presenting as a cavitary lesion

Erosion of an automatic internal cardioverter-defibrillator (AICD) patch into the lingular bronchus occurred 4 years after implantation; the erosion presented as a cavitary mass associated with hemoptysis and weight loss. On bronchoscopy to evaluate for suspected carcinoma, a cavity was entered through a bronchial defect and the AICD patch clearly identified. The complication was successfully treated with patch removal and fistula closure.

Electrosurgery and cardiac devices

The increased number of patients with implantable cardiac devices presents a unique challenge to physicians performing office-based electrosurgical procedures. Electrosurgery can be performed safely if the electrosurgical techniques and potential risks from these devices are understood. We present an overview of the most common types of implantable cardiac devices, potential complications associated with them, and recommendations for preoperative evaluation, intraoperative monitoring, and postoperative follow-up.

Derivation of a defibrillator implant criterion based on probability of successful defibrillation

Common criteria for implant of a cardioverter defibrillator include verification of a 2:1 energy safety margin or a fixed safety margin of 10 joules. These criteria have been established empirically. We present a statistically model based on defibrillation efficacy curves which may be used to establish a criterion which would meet a predetermined target. As an example, an implant criterion is derived based on a goal of 1-year sudden cardiac death survival of at least 99% by selecting an expected first-shock efficacy to meet that target. Logistic regression was performed on data from over 1,500 defibrillator implants including successful epicardial and transvenous electrode system implants as well as data from unsuccessful implants. A random sample from these curves was used to generate a representative sample of 1,000 potential implant candidates. By assuming successful defibrillation using a series of shocks at specified energies, i.e., choosing an implant criterion, the probability of successful defibrillation of the patient by a single shock at a predetermined maximum output can be established. Independent data are used to validate the model's accuracy in predicting defibrillation efficacy within the derived example.

Undersensing of ventricular fibrillation in a noncommitted nonthoracotomy cardioverter defibrillator system

OBJECTIVE

Evaluation of the impact of undersensing on VF detection time and the relationship of undersensing to the programmed shock energy.

BACKGROUND

Failure to reconfirm an ongoing arrhythmia due to undersensing by a noncommitted ICD might prolong the time to therapy.

METHODS

We measured initial detection times and redetection times at predischarge and at 2 and 6 months in 29 patients (22 men, mean age 60 years) with a noncommitted nonthoracotomy ICD. Telemetry data and output markers were used to analyze each induction.

RESULTS

Undersensing leading to failure to reconfirm was present in 44 (11.1%) of 398 episodes of sustained VF and prolonged significantly the median initial detection time from 2.3 seconds (25th and 75th percentiles: 2 and 2.6 s, respectively) to 5.45 seconds (4.3 and 7.35 s, P < 0.0001). One episode required external defibrillation after reconfirmation failure occurred during charging; the total detection time prior to shock was 46 seconds. In a subset of 87 episodes with failed first shocks, the initial detection time was 2.3 seconds (2.1 and 2.8 s) and the redetection time 3 seconds (2.5 and 4.77 s, P < 0.0001). The presence of undersensing prolonged the redetection from 2.6 seconds (2.35 and 3.1 s) to 5.4 seconds (4.53 and 7.35 s, P < 0.0001). Undersensing was more prevalent during the redetection period (P = 0.004) and in episodes of sustained VF in which the first shock energy was higher than 15 J (19.7% vs 5.8%, P < 0.0001).

CONCLUSIONS

In this automatic defibrillator system, undersensing occurs in 11% of the sustained VF inductions and prolongs detection time significantly. Redetection is longer than initial detection mostly due to the presence of undersensing, the frequency of which is proportional to the programmed energy. The clinical significance of this finding is unknown.

Complete infrahisian atrioventricular block after endocavitary shock delivered by an automatic implantable cardiac defibrillator

Transient reproducible complete infrahisian atrioventricular block occurred after endocavitary cardioversion of ventricular tachycardia and ventricular fibrillation by an automatic implantable cardiac defibrillator in a patient with left bundle branch block and baseline borderline H-V interval. Six months later, a permanent complete atrioventricular block occurred after repetitive endocavitary shocks. Several hypothetical mechanisms may explain this infrahisian atrioventricular block a "fatigue" phenomenon of the His-Purkinje system, vagally mediated atrioventricular block, and/or ablation of the His conduction system. The last seems to be the most probable, which would justify implantation of an automatic implantable cardiac defibrillator with backup pacing in all patients, especially in the presence of bundle branch block.

Medical devices and attachment: holistic healing in the age of invasive technology

The environment is filled with wonderful examples of medical technology that provide emergency life support, improve well-being, and offer the possibility of a longer and more productive life. But these devices are no longer only a part of the external environment. As technology advances, more devices are becoming a part of the internal environment (i.e., our bodies) as well. For some people an implanted mechanical device, such as a cardiac pacemaker or a cardioverter defibrillator, is readily accepted; for others it may be seen as an encroachment. It may be a symbol of loss and debilitation or of independence and resilience. What makes the difference? How can nurses facilitate a healthy adjustment and healing in an era permeated with technology? A discussion of the symbolism, related theory, and nursing implications is provided.

Incidence and clinical significance of multiple consecutive, appropriate, high-energy discharges in patients with implanted cardioverter-defibrillators

BACKGROUND

Some patients with an automatic implantable cardioverter-defibrillator (ICD) suffer multiple appropriate, consecutive, high-energy discharges (MCDs) during follow-up. Such events might represent resistant ventricular arrhythmias and might have prognostic significance.

METHODS AND RESULTS

Eighty consecutive patients with an ICD were followed up for up to 82 months (mean, 21 +/- 19 months). Thirty-eight patients had survived an out-of-hospital cardiac arrest and 42 had recurrent ventricular tachycardia. During follow-up, 16 patients had MCD (group A), 26 patients had episodes of single appropriate discharges (group B), and 38 patients had no appropriate discharges (group C). Group A patients had worse functional status (P = .001), lower left ventricular ejection fractions (LVEFs) (P = .001), and lower survival rates (log rank, P = .003) than the remaining two groups of patients. Cox analysis showed LVEF (P = .001) to be an independent predictor of MCD. Independent predictors of death or heart transplant were MCD (P = .001), female sex (P = .001), age (P = .001), history of cardiac arrest (P = .003), and functional status (P = .003). The only independent predictor of total mortality was female sex (P = .002). Independent predictors of cardiac death were MCD (P = .007) and female sex (P = .018). Independent predictors of arrhythmic death were age (P = .001), female sex (P = .02), and MCD (P = .023).

CONCLUSIONS

In patients with an ICD, the development of MCD is an independent predictor of cardiac and arrhythmic mortality. If this finding is confirmed in larger studies, it may help to identify patients in whom other therapeutic alternatives, ie, heart transplantation, should be considered during follow-up after ICD implantation.

Gender bias in the diagnosis and treatment of coronary artery disease

Women are at high risk for cardiovascular disorders, but referrals for both diagnostic and therapeutic procedures seem to reflect a gender bias. Procedures and therapies currently used have been developed predominantly or exclusively for men. Medical history demonstrates a disregard of women's health problems that still may be operative today. Women are older and sicker when they have angioplasty or bypass grafting, and they receive far fewer implantable cardioverter defibrillators and heart transplantations. They have more hypertension, diabetes, longer stays in intensive care units, and poorer outcomes. This may be the result of a problem with referral or a difference in the way women experience cardiac symptoms. It may also be related to the way women perceive themselves and their illness. Efforts are being made to provide equitable and relevant health care for women and to conduct research that will describe women's cardiac symptoms and their responses to cardiovascular technology.

The impact of the implantable cardioverter defibrillator on quality-of-life

The implantable cardioverter defibrillator (ICD) is an established treatment for patients with life-threatening ventricular arrhythmias. While it clearly reduces the incidence of death from recurrent arrhythmia, little is known about the impact on patients' quality-of-life. In this prospective study, quality-of-life was assessed by questionnaire before and after ICD implantation. The "Sickness Impact Profile" (SIP), which evaluates physical, psychosocial, and other activities, as well as functions of daily life, was used. Employment and rehospitalization rates were also examined. Twenty-one of 23 consecutive patients, aged 58 +/- 11 years, undergoing ICD implantation at Royal Perth Hospital were studied. During the 14 +/- 8 month follow-up, 4 patients died. Functional capacity was unchanged in all but one of the survivors in whom it improved from New York Heart Association Class III to II. Four of 8 survivors employed before implant have since retired. Six patients required rehospitalization on 13 occasions, problems related to arrhythmias or the ICD. Overall SIP scores preimplant (11.2 +/- 9.3; P < 0.05) were significantly worse at 6-month follow-up (21.7 +/- 18.2), but returned to preimplant levels by 12-month follow-up (8.8 +/- 10.8; NS). This was primarily due to transient problems in the areas of emotional behavior, alertness, and social interaction. SIP psychosocial dimension scores: preimplant: 7.2 +/- 9.0; 6-month: 17.8 +/- 18.1 (P < 0.05); and 12-month: 8.6 +/- 10.3 (NS). Early retirement and hospitalizations due to arrhythmias may still be expected even after implantation of an ICD; however, quality-of-life appears only to temporarily decline.

Italian multicenter clinical experience with endocardial defibrillation: acute and long-term results in 307 patients. The Italian Endotak Investigator Group

This study presents the acute and long-term results of 307 patients (267 men, mean age 57.5 years, 205 suffering from coronary artery disease, mean left ventricular ejection fraction 33.3%) with malignant ventricular tachyarrhythmias who underwent attempted transvenous ICD implantation with the CPI Endotak lead system in 37 Italian centers. Transvenous ICD implantation was ultimately accomplished in 306 (99.7%) patients. These included 19 subjects with high (< 10 J below output energy of implanted device) defibrillation threshold (DFT) at implant. One hundred sixty-four patients (53%) were implanted with the endocardial lead alone, while 142 also received an SQ patch or SQ array. The mean DFT (not always step-down DFT) at implant was 16.9 +/- 5.7 joules; 15.3 +/- 5.2 joules with biphasic shock and 19.6 +/- 5.4 joules with monophasic shock; P < 0.0001. A significantly higher percentage of patients tested with a biphasic shock could be implanted with adequate safety margin and without an additional SQ patch or SQ array (98% and 81%, respectively). No perioperative deaths occurred. During the mean follow-up of 14.5 +/- 10.2 months, 140 patients (52%) received at least one appropriate shock. An inappropriate shock was observed in 26% of episodes. The 1- and 3-year actuarial incidence of sudden death was 2% and 4%, respectively, and that of total death was 10% and 20%, respectively. A pocket infection requiring ICD explantation occurred in 4 patients (1.4%) and an endocardial lead dislodgment in 11 patients (3.6%). Two patients (0.3%) showed a sensing pin disconnection and six patients (2.3%) had a lead insulation break. The results of this Italian multicenter trial indicate that the CPI Endotak lead system is a simple, safe, and reliable system for endocardial defibrillation. When compared to epicardial leads, it clearly reduces the perioperative mortality and morbidity, while maintaining a similar efficacy in preventing sudden death and terminating ventricular arrhythmias.

Description and evaluation of the Res-Q Arrhythmia Control Device

The Res-Q Arrhythmia Control Device (Intermedics Inc.) is one of the latest entries into the growing implantable cardioverter defibrillator (ICD) market. Dysrhythmias are classified according to their zone of detection, with a bradycardia zone, up to 3 tachycardia zones, and a fibrillation zone. Detection criterion, therapies, and redetection criterion within each zone are independently programmable, tailoring the setup to each individual's needs. In a hierarchical manner, this allows efficacy, urgency, and patient comfort to be appropriately balanced. Tachycardia therapy options include antitachycardia pacing (ATP), low-energy cardioversion, and high-energy shock, while VVI pacing provides bradycardia therapy. ATP programming is extremely flexible. Biphasic waveform and a maximum output of 700 V have yielded a high rate of successful implantation. Unique features include the multiprogrammable sensing autogain, which tracks evoked T waves during pacing, as well as the use of the pulse generator to perform implant testing. Major strengths include programming flexibility and individualized therapy for multiple dysrhythmias. The major shortcoming relates to a lack of stored electrograms. Although long-term follow-up is not yet available, the Res-Q appears to be a capable challenger to a peer group of advanced generation ICDs.

Management of electrical instability after ICD implantation

Postoperative ventricular arrhythmias were studied in 52 patients receiving implantable cardioverter defibrillators (ICDs). A group of 9 patients was identified who experienced electrical instability (EI). The lead approach was thoracotomy in 6 and nonthoracotomy in 3 patients. In 8 of 9 patients VTs started soon after surgery. There was no evidence of ischemia, cardiac failure, electrolyte imbalance, or drug intoxication. The severity of ventricular arrhythmias varied from a considerable increase in incidence of well-tolerated VTs in 3 patients (1 incessant) to poorly tolerated frequent VTs in 6 patients (2 incessant). In 4 patients VTs led to cardiac failure. Ventricular arrhythmias during EI were refractory to antiarrhythmic drugs (AAD) in 7 of 9 patients. In 3 patients VTs accelerated into fast VT or VF with antitachycardia pacing (ATP) or cardioversion. The successful management of EI was: sedation in 4 patients (3 with midazolam 1 with temazepam), ATP and AAD in 2 patients, AAD and hemodynamic support in 2 patients, spontaneous resolution in 1 patient. All patients survived the period of postoperative EI. Two patients had a relapse of EI at 2- and 9-months postimplantation, respectively, one of whom eventually died.

CONCLUSIONS

EI occurred in 17% of patients after ICD implantation, had a varying degree of severity and required an individualized approach. Control of EI with AAD was successful in only 2 of 9 patients. Sedation with midazolam was useful in the management of EI.

Implantable defibrillation and thromboembolic events

In ICD patients thromboembolic events (TEEs) are described as possible complications at implant or during the follow-up. We report four cases of TEEs (two peripheral and two cerebral; 6.5% of patients) that occurred in our series during a mean follow-up of 19.4 months. The patients had chronic postinfarction LV aneurysm (3) and idiopathic dilated cardiomyopathy (1). None had previous embolisms nor evidence of left atrial or LV clots at standard preoperative transthoracic echocardiography. No paroxysms of atrial fibrillation were documented prior or after ICD implant. We discuss the possible causes of embolization and the suitability of anticoagulant therapy in ICD patients.

Predictors of device activation for ventricular arrhythmias and survival in patients with implantable pacemakers/defibrillators. CADENCE Investigators

Predictors of survival and arrhythmia recurrence for patients with implanted defibrillators have been reported but patients with sustained, well-tolerated ventricular tachycardia were often excluded from these trials. Arrhythmia recurrence and survival in populations including these patients have been less well studied. The purpose of the present study was to examine predictors of spontaneous ventricular arrhythmias and mortality in patients who received a tiered therapy antitachycardia pacemaker/defibrillator for ventricular tachycardia, fibrillation, or both. Three hundred thirty-seven patients who received a Ventritex CADENCE tiered therapy antitachycardia device at one of 19 participating centers between July 11, 1989 and March 4, 1991 are included in this retrospective analysis. Diagnostic summary data and stored electrograms telemetered from the implanted device were assessed to determine characteristics of recurrent arrhythmias. Mean follow-up was 360 +/- 10 (SEM) days. Thirty-three patients died during follow-up. At least one recurrent ventricular arrhythmia was observed in 205 patients (61%). A total of 7,539 episodes were observed with a mean of 37 +/- 5 per patient. Patients with recurrent ventricular arrhythmias were slightly but significantly older (64 +/- 0.7 vs 59 +/- 1.2 years; P < 0.001) but were not distinguished by gender or underlying structural disease. Patients whose presenting arrhythmia was monomorphic ventricular tachycardia were more likely to experience recurrent ventricular arrhythmias (69% recurrence rate) than patients presenting with ventricular fibrillation or polymorphic ventricular tachycardia (46% recurrence rate; P < 0.001). Cycle length of spontaneous tachycardia was also a predictor of arrhythmia recurrence. Patients having slower ventricular arrhythmias were less likely to remain recurrence free. Mean left ventricular ejection fraction was similar for patients with and without recurrences. Younger age and absence of arrhythmia recurrence but not presenting arrhythmia were predictors of survival. We conclude that age and presentation with monomorphic ventricular tachycardia are important predictors of arrhythmia recurrence for this patient population. Exclusion of patients with monomorphic ventricular tachycardia underestimates the rate of recurrent ventricular arrhythmias and utilization of device therapy.

Nonthoracotomy defibrillator implantation: a single-center experience with 200 patients

Nonthoracotomy leads for defibrillator implantation and biphasic shocking devices are under investigation. Implantation success and mortality and morbidity of the procedure determine the operative course. Lead-associated complications, late infection, and freedom of sudden cardiac death characterize the follow-up period with respect to the implanted device. From October 1989 to March 1993 in 200 patients, 205 (including five infections caused by reimplantations) transvenous or transvenous-subcutaneous lead systems were tested. Mean ejection fraction was 0.40 +/- 0.16. In 62.5% (125/200) coronary artery disease and in 19% (38/200) cardiomyopathy was the underlying disease (59 patients with prior cardiac operations). Leads were implanted with defibrillation thresholds less than 25 J in 195 patients, whereas 10 patients received intrathoracal patches. Since biphasic shocks became available, no nonthoracotomy lead system has failed in the last 115 consecutive patients. Perioperative mortality in the nonthoracotomy group was 1% (2/195). In 6.2% (12/193) of the surviving patients, perioperative complications occurred. Major problems were bleeding from the device or patch pocket (n = 6) and early infection (n = 2). During the follow-up of 20 +/- 10 months, lead-associated complications (dislocation, lead fracture, insulation defect, loss of sensing) occurred in 9 patients and in 5 patients late infection appeared. Within the follow-up period no patient died suddenly, and 134 patients received therapeutic interventions by the device. Defibrillator implantation using nonthoracotomy leads, especially combined with biphasic shocking devices, is applicable in almost every patient. During the operative course and follow-up, the defibrillator-associated morbidity and mortality is at the same level as or lower than when using patch lead systems.

Predicting and preventing sudden death from cardiac causes

Sudden cardiac death usually occurs secondary to a ventricular tachyarrhythmia. Even under ideal circumstances only 20% of patients who have an out-of-hospital cardiac arrest survive to hospital discharge. Therefore, aggressive treatment and screening of high-risk patients are mandatory to improve survival rates. Risk stratification of high-risk patients, such as the post-myocardial infarction (MI) population, has been of limited value. Between 70% and 85% of "high-risk" post-MI patients, as defined by these screening tests, will not have a sustained ventricular tachyarrhythmia over several years of follow-up. The use of beta-blockers and possibly amiodarone may have some benefit in reducing mortality in high-risk patients after an MI. Several ongoing trials are studying the use of serial drug testing, amiodarone, and implantable cardioverter-defibrillators in reducing the incidence of sudden cardiac death in patients with potentially lethal ventricular arrhythmias. Although implantable cardioverter-defibrillators appear to be superior to antiarrhythmic drugs in reducing sudden cardiac death, total mortality may not be altered. In sustained ventricular tachyarrhythmias, sotalol and amiodarone appear to be superior to other drugs in preventing arrhythmia recurrence. Ongoing trials, such as the Antiarrhythmic Drug versus Implantable Device (AVID) trial may define the best strategy in these high-risk patients.

Clinical experience with a new cardioverter defibrillator capable of biphasic waveform pulse and enhanced data storage: results of a prospective multicenter study. European Ventak P2 Investigator Group

A recently introduced cardioverter defibrillator was implanted in 162 patients with refractory ventricular tachyarrhythmias and/or aborted sudden cardiac death. The new device is capable of delivering monophasic and biphasic defibrillation waveform pulses, arrhythmia detection, and therapy in two independently programmable zones, antibradycardia and postshock pacing. Additionally, the device enhanced data logs by storing intracardiac "far-field" electrograms of spontaneous arrhythmic episodes. One hundred sixty-two patients (mean age 55.5 years; mean left ventricular ejection fraction 36%) were enrolled in this multicenter investigation; coronary artery disease was the primary cardiac disease in 63.6% of the patients, idiopathic cardiomyopathy in 23.8%. Ventricular fibrillation was present in 49.7% of the patients; 29.3% of the patients experienced ventricular fibrillation and ventricular tachycardia; monomorphic ventricular tachycardia alone was present in 19.1% of the patients. In 26 patients the device was implanted with standard epicardial defibrillation leads (mean defibrillation threshold 11.5 +/- 3.7 J). One hundred thirty-nine patients underwent testing for implantation of a nonthoracotomy system and in 136 (98%), a nonthoracotomy system could be implanted. Defibrillation thresholds with a biphasic waveform (mean 10.2 +/- 4.3 J) were lower than with a monophasic waveform (mean 17.4 +/- 5.7 J). Two patients (1.2%) died perioperatively (< 30 days). During study time period follow-up, there were 338 device discharges in 49 patients. Analysis of stored electrograms classified 25% of discharges as inappropriate and due to supraventricular tachyarrhythmias. At a mean follow-up of 10.8 months, cumulative survival from sudden cardiac death was 98.8%, and survival from all-cause mortality was 96.3%. This study demonstrates the effectiveness of a new implantable cardioverter defibrillator in preventing arrhythmic death and the superior defibrillation efficacy of biphasic waveform pulses, which results in a higher implantation rate of nonthoracotomy systems, as well as the accurate arrhythmia classification made possible by the stored electrograms.

Perioperative complications of cardioverter-defibrillator implantation: the Emory experience

Over a 5-year period, 110 cardioverter-defibrillators (109 epicardial, 1 transvenous) were implanted consecutively in selected patients with ventricular tachyarrhythmias. The perioperative course of this patient population was examined to determine the associated morbidity and mortality of the procedure. Patients were predominantly male, with coronary artery disease and a decreased left ventricular ejection fraction. Most underwent median sternotomy for implantable cardioverter defibrillator implantation. The incidence of perioperative mortality was found to be 2.7%. New-onset atrial fibrillation or flutter occurred in 17.3% of the patients during the postoperative period and aggravation of ventricular tachyarrhythmias in 19.1%. The ICD system became infected in 2.7% of the patients and the mediastinal incision site infected in 2.4%. Pneumonia developed in 4.5%. Other complications included significant blood loss, ICD pocket hematomas, and lead dislodgement. There is an appreciable incidence of morbidity and mortality associated with ICD implantation.

Future developments in implantable cardioverter defibrillators: the optimal device

Despite recent therapeutic advances, SCD remains the leading cause of mortality in industralized nations. The most frequent cause of SCD is ventricular tachyarrhythmias in the setting of advanced structural heart disease due to chronic coronary heart disease or idiopathic dilated cardiomyopathy. Although high-risk groups can be prospectively identified, attempts at primary prevention have been largely unsuccessful. Effective treatment strategies for SCD survivors include antiarrhythmic drug therapy guided by programmed stimulation, endocardial resection, and ICDs. Device therapy has proven extremely effective in preventing recurrent sudden death from ventricular tachyarrhythmias. Widespread application of ICD therapy, perhaps even to include members of high-risk populations that have not experienced cardiac arrest, will depend on many factors including the demonstration that device therapy improves total mortality, not just arrhythmia-related mortality, reduction in cost, and improvements in the devices themselves. Some of the important characteristics of the optimal ICD of the future are nonthoracotomy lead placement; subpectoral generator placement; multiprogrammable, tiered therapy; improved diagnostic specificity, whether based on electrogram or hemodynamic-sensing algorithms; improved integration of brady- and tachy-sensing systems; and enhanced electrogram storage capability with trans-telephonic retrieval of electrogram recordings. The creation of this ideal ICD will obviously require continued technological advances; however, given the tremendous improvements realized over the first three generations of ICD systems, optimism for the future seems warranted.

Use of a regional wall motion score to enhance risk stratification of patients receiving an implantable cardioverter-defibrillator

OBJECTIVES

We postulated that preoperative assessment of both regional wall motion and left ventricular ejection fraction would serve as an accurate prognostic indicator of long-term cardiac mortality and functional outcome in patients treated with an implantable cardioverter-defibrillator.

BACKGROUND

Long-term cardiac mortality has remained high in patients receiving an implantable cardioverter-defibrillator. The ability to risk stratify patients before defibrillator implantation is becoming increasingly important from a medical and economic standpoint.

METHODS

The hypothesis was retrospectively tested in 74 patients who had received an implantable cardioverter-defibrillator. Left ventricular ejection fraction and regional wall motion score, derived from centerline chord motion analysis, were calculated for each patient from the preoperative right anterior oblique contrast ventriculogram. Wall motion score was the only significant independent predictor of long-term cardiac mortality and functional status by multivariate analysis because of its enhanced prognostic capability in patients with an ejection fraction in the critical range of 30% to 40%.

RESULTS

Patients with an ejection fraction > 40% had a 3-year cardiac mortality rate of 0% compared with 25% for those with an ejection fraction of 30% to 40% and 48% for those with an ejection fraction < 30% (p < 0.05). Similarly, 75% of patients with an ejection fraction > 40% were in New York Heart Association functional class I or II during long-term follow-up compared with 59% of those with an ejection fraction 30% to 40% and 29% of those with an ejection fraction < 30%. Among patients with an ejection fraction of 30% to 40%, those with a wall motion score > 16% had a 3-year cardiac mortality rate of 0% compared with 71% of those with a wall motion score < or = 16% (p = 0.002). In addition, 86% of patients with a wall motion score > 16% were in functional class I or II during long-term follow-up compared with 13% of those with a wall motion score < or = 16% (p = 0.001).

CONCLUSIONS

Long-term cardiac mortality and functional outcome in patients receiving an implantable cardioverter-defibrillator can be predicted if the left ventricular ejection fraction and regional wall motion score are measured preoperatively.

Comparison of the usefulness of the implantable cardioverter-defibrillator and subendocardial resection in patients with sustained ventricular arrhythmias and poor regional wall motion associated with coronary artery disease

The implantable cardioverter-defibrillator (ICD) and subendocardial resection are effective forms of therapy for sustained ventricular arrhythmias associated with coronary artery disease in selected patients. The relative efficacy of these 2 treatments in equivalently matched patients is not known. A regional wall motion score has been shown to be a powerful predictor of long-term outcome after both ICD implantation and subendocardial resection. This study retrospectively analyzed the long-term outcome of patients with coronary artery disease and ventricular arrhythmias treated during the same period with an ICD (n = 53) or by subendocardial resection (n = 65). Treatment outcomes were compared in subgroups determined by preoperative regional wall motion scores of either < or = 16 or > 16%. The 3-year cardiac mortality of the 2 therapies was not significantly different among patients with a wall motion score of > 16% (0% ICD vs 11% endocardial resection) or of < or = 16% (41% ICD vs 35% endocardial resection). Similarly, the 3-year sudden cardiac death mortality was similar among patients with a score of > 16% (0% for both ICD and endocardial resection) or of < or = 16% (9% ICD vs 14% endocardial resection, p = NS). At 24 months after hospital discharge, the percentage of patients who were in New York Heart Association functional class I or II was similar among patients with a wall motion score of > 16% (75% ICD vs 86% endocardial resection, p = NS) or with a wall motion score of < or = 16% (26% ICD vs 45% endocardial resection, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Sudden cardiac death and the use of implantable cardioverter-defibrillators in pediatric patients. The Pediatric Electrophysiology Society

BACKGROUND

During the past decade, the implantable cardioverter-defibrillator (ICD) has emerged as the primary therapeutic option for survivors of sudden cardiac death (SCD). Investigation of the clinical efficacy of these devices has primarily assessed outcome in adults with coronary artery disease. The purpose of this cooperative, international study was to evaluate the impact of ICDs on the pediatric population of SCD survivors, based on an analysis of the clinical characteristics and outcomes of young patients who underwent ICD implantation following an episode of life-threatening ventricular tachycardia or resuscitation from SCD.

METHODS AND RESULTS

An initial data base, established by contacting the manufacturers of the various commercially and investigationally available devices, identified 177 patients who were less than 20 years of age at the time of initial implantation of an ICD. With this data base as a reference, detailed responses were subsequently obtained from physicians involved in the care of 125 (71%) of these patients. The patients ranged in age from 1.9 to 19.9 years (mean, 14.5 +/- 4 years) and weighted 9.7-117 kg (mean, 44.6 +/- 14 kg). Of the 125 patients, 76% were survivors of SCD, 10% had drug refractory ventricular tachycardia, and 10% had syncope with heart disease and inducible sustained ventricular tachyarrhythmias. The most common types of associated cardiovascular disease were hypertrophic and dilated cardiomyopathies (54%), primary electrical diseases (26%), and congenital heart defects (18%). Ventricular function was abnormal in 46% of the patients. During a mean follow-up of 31 +/- 23 months, at least one ICD discharge occurred in 85 of the 125 (68%) patients. Seventy-three patients (59%) received at least one appropriate ICD discharge, and 25 patients (20%) had one or more spurious or indeterminate discharges. Duration of follow-up > 24 months (p = 0.001) and inducibility of a sustained ventricular arrhythmia (p = 0.05) were correlated with appropriate ICD discharges. There were nine deaths during the study period: five sudden, two due to recurrent ventricular arrhythmias, and two related to congestive heart failure. Abnormal ventricular function (p = 0.002) and prior ICD discharge (p = 0.01) were univariate correlates of patient mortality; by multivariate logistic regression, abnormal ventricular function was the only significant correlate of death (p = 0.005). By actuarial analysis, the estimated overall post-ICD implant survival rates at 1, 2, and 5 years were 95%, 93%, and 85%, respectively. The corresponding sudden death-free survival rates were 97%, 95%, and 90%.

CONCLUSIONS

Pediatric patients resuscitated from SCD appear to remain at risk for recurrence of life-threatening tachyarrhythmias. During a mean follow-up of 31 months, the ICD provided an effective therapy for such arrhythmias in the majority of patients in this study. Following ICD implant, impaired ventricular function was the primary factor correlated with mortality. The patterns of ICD discharge observed in young patients and, thus, inferred risk of recurrent life threatening arrhythmias are similar to those of adult survivors of SCD. Thus, the use of ICDs in pediatric patients, with implant selection criteria similar to adults, appears valid.

ICD implantation via thoracoscopy without the need for sternotomy or thoracotomy

After development of the technique in mongrel dogs, implantable cardioverter defibrillator (ICD) patch and sensing lead implantation was attempted via thoracoscopy, without sternotomy or thoracotomy, in three patients. Two large titanium mesh defibrillator patches and two "screw-in" epicardial sensing leads were applied without difficulty in each of two patients. In a third patient, satisfactory placement of the defibrillator patches could not be achieved via thoracoscopy, necessitating thoracotomy. Defibrillation threshold (DFT), cardioversion energy requirement (CER), and rate and morphology signals in those patients with successful thoracoscopic implantation were comparable to those achieved by open technique. We conclude that ICD patch and sensing lead implantation via thoracoscopy is feasible.

Implications for present and future applications of the implantable cardioverter-defibrillator resulting from the use of a simple model of cost efficacy

OBJECTIVE

To develop a model to assess the cost-efficacy of the implantable cardioverter defibrillator to prevent sudden death. The model must be sufficiently flexible to allow the use of cost and survival figures derived from different sources.

SETTING

The study was conducted in a teaching hospital department of cardiology with experience of 40 implantable cardioverter defibrillator implants and a large database of over 500 survivors of myocardial infarction.

PROCEDURE

The basic costs of screening tests, stay in hospital, and purchase of implantable cardioverter defibrillators were derived from St George's Hospital during 1991. To assess the cost-efficacy of various strategies for the use of implantable cardioverter defibrillators, survival data taken from published studies or from our own database. Implications of the national cost of the various strategies were calculated by estimating the number of patients a year requiring implantation of a defibrillator if the strategy was adopted.

RESULTS

Use of implantable cardioverter defibrillators in survivors of cardiac arrest costs between 22,400 pounds and 57,000 pounds for each year of life saved. Most of the strategies proposed by the current generation of implantable cardioverter defibrillator trials have cost efficacies in the same range, and adoption of any one of these strategies in the United Kingdom could cost between 2 million pounds and 100 million pounds a year. Future technical and medical developments mean that cost-efficacy may be improved by up to 80%. Due to the limitations of screening tests currently available restriction on the use of implantable cardioverter defibrillators to those groups where it seems highly cost-effective will result in a small impact on overall mortality from sudden cardiac death.

CONCLUSION

Present and possible future applications of the implantable cardioverter defibrillator seem expensive when compared with currently accepted treatments. Technical and medical developments are, however, likely to result in a dramatic improvement in cost efficacy over the next few years.

Clinical characteristics and outcome of patients with high defibrillation thresholds. A multicenter study

BACKGROUND

Successful defibrillation by an implantable cardioverter-defibrillator (ICD) depends on its ability to deliver shocks that exceed the defibrillation threshold. This study was designed to identify clinical characteristics that may predict the finding of an elevated defibrillation threshold and to describe the outcome of patients with high defibrillation thresholds.

METHODS AND RESULTS

The records of 1,946 patients from 12 centers were screened to identify 90 patients (4.6%) with a defibrillation threshold greater than or equal to 25 J. Excluding three patients who received ICDs that delivered greater than 30 J, there were 81 men and six women with a mean age of 59.5 +/- 10.1 years, a mean left ventricular ejection fraction of 0.32 +/- 0.14, and a 76% prevalence of coronary artery disease. Sixty-one patients (70%) were receiving antiarrhythmic drugs, and 45 (52%) were receiving amiodarone. Seventy-one patients (82%) received an ICD. Death occurred in 27 patients--19 of the 71 (27%) with an ICD (eight arrhythmic), and eight of the 16 (50%) without an ICD (four arrhythmic). Actuarial survival for all patients at 5 years was 67%. Actuarial survival rates at 2 years for patients with and without an ICD were 81% and 36%, respectively (p = 0.0024). Actuarial survival at 5 years for the ICD patients was 73%; no patient without an ICD has lived longer than 32 months. Actuarial survival free of arrhythmic death in the ICD patients at 5 years was 84%. Although the only variable to predict survival was ICD implantation (p = 0.003), it is entirely possible that in this retrospective analysis, clinical selection decisions to implant or to not implant an ICD differentiated patients destined to have better or worse outcomes, respectively.

CONCLUSIONS

Antiarrhythmic drug use may be causally related to the finding of an elevated defibrillation threshold. When patients with high defibrillation thresholds receive an ICD, arrhythmic death remains an important risk (42% of deaths in these patients were arrhythmia related, with 16% actuarial incidence at 5 years). Vigorous testing to optimize patch location can potentially benefit patients by enhancing the margin of safety for effective defibrillation.

Implantable cardioverter defibrillators: current status and future directions

Sudden cardiac death remains the most common mode of mortality in the United States, accounting for up to 450,000 deaths per year. Survivors of cardiac arrest and patients who have recurrent ventricular tachycardia have a high mortality rate with or without antiarrhythmic therapy. The implantable cardioverter defibrillator (ICD) was introduced in 1980 by Mirowski as a potential treatment for these patients. There are presently over 24,000 implants worldwide and the device has proved to be an effective means of preventing sudden death. The components of an ICD include a generator, defibrillation patches or leads, and pacing/sensing leads. The devices can be implanted with acceptable mortality and morbidity either by median sternotomy, left anterior thoracotomy, subxiphoid, or left subcostal approaches. The long-term results have been excellent with an actuarial incidence of sudden cardiac death of 3% at 5 years. Improvements in battery and capacitor technology, lead design, and tachycardia recognition, combined with the addition of hemodynamic sensors and a better understanding of the science of defibrillation, should lead to further improvements over the next several years in the ICD.