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.     

Defibrillator therapy 1997. Prerequisites--results--prospects

BACKGROUND: The first human cardioverter defibrillator implant was performed in 1980. Since then, significant technological improvement has been performed and today, ICDs with multiple diagnostic and therapeutic features are available. We report on 541 patients who underwent ICD implantation between January 1984 and March 1997. Epicardial ICD implant was performed in 209 patients (39%) and 332 patients (61%) received transvenous ICDs. PATIENTS AND RESULTS: Perioperative mortality was 2% (13 patients), significantly more frequent after epicardial (12/209 patients, 6%) than after transvenous implantation (1/332 patients) (p < 0.01). During a mean follow-up of 28 +/- 23 months, 104 patients died (20%), 15 of them (3%) suddenly. 8407 arrhythmic episodes were observed and terminated by antitachycardia pacing in 6655 (79%). Infections occurred in 13 patients (2%), electrode complications in 43 patients (8%) and inappropriate shocks in 84 patients (16%). CONCLUSION: The ICD is an effective approach to treat patients with life-threatening ventricular tachyarrhythmias leading to a low incidence of sudden death. Today, there is a low operative risk and modern ICDs have multiple diagnostic and therapeutic features that allow individual ICD therapy.     

Non-pharmacologic prevention of sudden cardiac death

Non-pharmacologic therapy has revolutionized the management of arrhythmias and prevention of sudden cardiac death (SCD). Of particular importance is the introduction of radiofrequent catheter ablation (RFCA) and implantable cardioverter-defibrillator (ICD). RFCA is effective and useful in the treatment and prevention of SCD, especially in supraventricular tachyarrhythmias related to dual or accessory atrioventricular pathways. There are some limitations in using this method in the prevention of SCD in ventricular tachyarrhythmias. RFCA is very successful, particularly in the treatment of bundle branch reentrant ventricular tachycardia and ventricular tachycardia in patients without structural heart disease. RFCA can be used as a palliative treatment of incessant or frequent VT before and after ICD implantation. Antibradycardia pacing decreases SCD not only by the removal of serious bradyarrhythmias but also by prevention of the occurrence of malignant ventricular tachyarrhythmias induced by bradyarrhythmia. Antitachycardia pacing is used in the prevention of SCD only as a part of ICD device. Implantation of an antitachycardia pacemaker as an isolated permanent treatment of tachycardias is currently almost not used. This method was replaced by RFCA in supraventricular tachyarrhythmias and by ICD in ventricular tachyarrhythmias. ICD is a very perspective non-pharmacologic approach to SCD prevention, particularly as transvenous leads were introduced and device construction was simplified. ICD is indicated especially in patients with spontaneous sustained hemodynamically significant ventricular tachycardia/ventricular fibrillation and when antiarrhythmic drug treatment, RFCA or antitachycardia surgery are ineffective, intolerated, contraindicated or cannot be performed. ICD as the treatment of first choice instead of antiarrhythmic drugs as well as prophylactic ICD implantation in asymptomatic patients at high risk is a subject of discussion. ICD decreases the incidence of SCD significantly. However, the decrease in overall mortality was not verified. Antitachycardia surgery is less frequently used after RFCA, and ICD have been introduced. At present, this therapy is reserved only for the cases of failure of RFCA or the impossibility to use RFCA and ICD. Surgical therapy can be combined also with concommitant surgical correction of associated structural heart disease. Sympathectomy is used in prevention of malignant ventricular tachyarrhythmias and SCD in patients with congenital long Q-T syndrome. Selective left cardiac sympathetic denervation significantly reduces the risk of SCD in these patients but does not remove it completely. Heart transplantation is the last alternative of non-pharmacologic prevention of SCD. It is indicated in cases when all pharmacologic and non-pharmacologic approaches have been exhausted. Heart transplantation is the only effective modality for the improvement of long-term prognosis in patients with malignant ventricular tachyarrhythmias and advanced chronic heart failure.     

Therapy of ventricular tachyarrhythmia with implantable cardioverters/defibrillators--mortality and complications using epicardial electrodes

Technical improvements of third generation implantable cardioverter defibrillators (ICD) like antitachycardia pacing modalities lead to an extended use of ICDs, not only in patients with aborted sudden cardiac death, but also in patients with hemodynamically tolerable ventricular tachycardia. In addition, anticipated results of current prospective studies might indicate the prophylactic use of ICDs in patients with high risk for sudden cardiac death, but without documented ventricular tachyarrhythmias. This report reviews mortality and complications associated with the ICDs with epicardial defibrillation leads. Mortality is separated in cardiac death, sudden cardiac, arrhythmogenic "not so sudden" cardiac death, and overall mortality. Pulmonary complications and infections are related to the underlying disease and the surgical procedure. Device- and lead-related complications, high defibrillation thresholds, pacemaker interactions, inappropriate shocks, arrhythmic effects, syncope, and psychosocial problems are reported, respectively.     

Clinical significance of sleep apnea disorders after implantation of a cardioverter-defibrillator in patients with cardiac disease and sustained ventricular tachyarrhythmia

The purpose of our study was to determine the prevalence of sleep related breathing disorders (SRBD) in patients with an implantable cardioverter-defibrillator (ICD) and to evaluate prospectively the possible influence of SRBD on arrhythmia recurrence and circadian arrhythmia variation as well as on cardiac mortality during long-term follow-up. Forty consecutive ICD recipients with cardiac disease and a documented history of spontaneous, life-threatening, ventricular tachyarrhythmias underwent full-night polysomnography and were followed for 2 years. In 16 of 40 patients (40%), SRBD were diagnosed (Apnea/Hypopnea Index (AHI) > 10); in 9 of these 16 patients (56%) central sleep apneas (CSA) occurred (in 8 of these 9 patients in combination with Cheyne-Stokes respiration). Seven of the 16 patients with SRBD (44%) revealed obstructive sleep apneas (OSA). AHI was 32 +/- 15 (12-60) in patients with CSA and 32 +/- 27 (11-86) in patients with OSA. Patients with and without SRBD were comparable concerning left ventricular ejection fraction, NYHA classification, cardiac disease, ICD indication, and concomitant medication. ICD registered ventricular tachyarrhythmias occurred in 10 of 24 patients (42%) without SRBD, in 4 of 9 patients (44%) with CSA, and in 3 of 7 patients (44%) with OSA. The numbers and circadian variation of episodes registered during follow-up in patients without SRBD, with OSA or CSA were comparable (14 +/- 25, median 4 vs 15 +/- 15, median 7 vs 4 +/- 5, median 2.5). The 2-year cardiac mortality was highest in patients with CSA (4/9 (44%) vs. 0/7 patients (0%) with OSA vs 3/24 patients (12.5%) without SRBD. Thus, the prevalence of SRBD in patients with chronic heart failure and a history of malignant ventricular tachyarrhythmias is high (40%) and the occurrence of CSA seems to be predictive for cardiac mortality in these patients. An influence of moderate SRBD on arrhythmia recurrence and circadian variation of spontaneous sustained tachyarrhythmic events could not be demonstrated.     

The stratification and prevention of the arrhythmia risk in nonischemic dilated cardiomyopathy]

The challenge of preventing arrhythmic sudden death is one of the major issues in today's treatment of heart failure. To achieve this ambitious goal, an accurate selection of the candidates for sudden death is needed on the one hand, while on the other hand, the assessment of the real cost/benefit ratio of the implantable cardioverter-defibrillator in selected patients, as compared to ACE inhibitors, beta-blockers and antiarrhythmic drug therapy, should no longer be delayed. As is well known, the incidence of sudden death is higher in ischemic dilated cardiomyopathy than it is in non-ischemic dilated cardiomyopathy. Moreover, tachyarrhythmic sudden death is prevalent in NYHA classes I and II (80%), whereas its incidence is lower (50%) in NYHA classes III and IV, since bradyarrhythmia, electromechanical dissociation and thromboembolic events characterize the other 50% of sudden deaths in patients in the latter NYHA class. The stratification of arrhythmic risk in non-ischemic dilated cardiomyopathy is questionable from any point of view, considering the poor predictive power of invasive and non-invasive indexes. However, some subgroups of high-risk patients should be selected, such as patients waiting for heart transplant or those with a severe disease but without an extreme degree of ventricular dysfunction, in whom the prognosis in terms of pump failure events is better and life expectancy is longer if the risk of arrhythmia is properly assessed and sudden death prevented. Consequently, the ICD implant may be effective in order to pursue the aim of reducing the tachyarrhythmic and bradyarrhythmic mortality in patients with a more severe disease and of minimizing the tachyarrhythmic risk in those with a less severe disease. Further studies will be developed to identify the ideal candidates for ICD implants.     

Prediction of mortality in mild to moderately symptomatic patients with left ventricular dysfunction. The role of the New York Heart Association classification, cardiopulmonary exercise testing, two-dimensional echocardiography and Holter monitoring

In order to investigate the value of peak oxygen consumption (peak VO2) in predicting mortality in mild to moderately symptomatic patients with left ventricular dysfunction, we studied 103 NYHA II/III class patients with a left ventricular ejection fraction (LVEF) < or = 40%. Heart failure was due to coronary artery disease (CAD) in 39 patients, idiopathic dilated cardiomyopathy in 54, hypertension in eight and surgically corrected valvular disease in two. The following variables were analysed: age, cause of heart failure (CAD vs no CAD), NYHA class, peak VO2, LVEF, left ventricular end-systolic volume index (LVESVI), ventricular tachycardia (VT) on Holter monitoring and the use of antiarrhythmic drugs. Statistical analysis was performed by Cox's proportional-hazards regression model. During a mean follow-up period of 20 months, there were 25 deaths. The estimated cumulative probabilities of survival were 88%, 73% and 58% at 1, 2 and 3 years, respectively. Cox's model identified CAD (P = 0.01), NYHA III class (P = 0.04) and LVEF (P = 0.02) as independent, statistically significant predictors of mortality. Peak VO2 had only a marginal statistical significance (P = 0.07). Age, LVESVI, VT on Holter monitoring and use of antiarrhythmic drugs were not related to mortality. These data can be important in patient clinical management and clinical trial design.     

Implantable cardioverter defibrillator utilization among device recipients presenting exclusively with syncope or near-syncope

INTRODUCTION: Implantable cardioverter defibrillators (ICDs) are occasionally used in presumed high-risk patients with electrocardiographically undocumented syncope, although the incidence of ventricular tachyarrhythmias in this population is not well defined. METHODS AND RESULTS: We studied 33 consecutive patients receiving an ICD (67% nonthoracotomy and 70% tiered therapy) after electrophysiologic testing for unmonitored "syncope" (n = 29) or "near-syncope" (n = 4). Atherosclerotic heart disease was present in 24 (73%); mean left ventricular ejection fraction (LVEF) was 0.39 +/- 0.15; and sustained monomorphic ventricular tachycardia (SMVT) was inducible in 18 (55%). Over a median follow-up of 17 months (range 4 to 61), 12 patients (36%) received > or = 1 appropriate ICD discharge triggered by SMVT (cycle length 230 to 375 msec) in 10 and ventricular flutter or fibrillation in 2--without concomitant antiarrhythmic medication in 8 of 12 cases. Inducible SMVT and LVEF < or = 0.35 were statistically significant, independent predictors of an appropriate ICD discharge (P < 0.02 and P < 0.03, respectively). Estimated 1-year cumulative survival free of appropriate discharge was 34% versus 87%, respectively, in patients with versus without inducible SMVT (P < 0.02), and 18% versus 56%, respectively, in patients with LVEF < or = 0.35 versus LVEF > 0.35 (P < 0.03). CONCLUSION: In this highly select, multicenter population of ICD recipients with electrocardiographically undocumented syncope, a substantial incidence of appropriate device discharges was observed, particularly in patients with inducible SMVT and LVEF < or = 0.35. These findings support the notion that, in patients with LV dysfunction and inducible SMVT, ventricular tachyarrhythmias are likely to account for episodes of syncope or near-syncope.     

Bronchodilator response to salbutamol after chronic dosing with salmeterol or placebo

OBJECTIVES: We report the occurrence of cardiac events during long-term follow-up in patients with hypertrophic cardiomyopathy (HCM) after cardioverter-defibrillator implantation. BACKGROUND: The identification of patients at high risk for sudden death and the prevention of recurrence of sudden death in HCM represents a difficult problem. METHODS: We retrospectively analyzed the occurrence of cardiac events during follow-up of 13 patients with HCM who received an implantable cardioverter-defibrillator (ICD) because of aborted sudden death (n = 10) or sustained ventricular tachycardia (n = 3) (group I). Findings were compared with those in 215 patients with an ICD and other structural heart disease or idiopathic ventricular fibrillation (group II). RESULTS: After a mean (+/-SD) follow-up period of 26+/-18 months, 2 of 13 patients in group I received appropriate shocks. The calculated cumulative incidence of shocks was 21% in group I and 66% in group II after 40 months (p < 0.05). We observed a low incidence of recurrence of ventricular tachycardia/fibrillation during follow-up in patients with HCM. No deaths occurred. CONCLUSIONS: Our data suggest that ventricular tachyarrhythmias may not always be the primary mechanism of syncope and sudden death in patients with HCM. The ICD seems to have a less important impact on prognosis in patients with HCM than in patients with other etiologies of aborted sudden death.     

T wave alternans as a predictor of recurrent ventricular tachyarrhythmias in ICD recipients: prospective comparison with conventional risk markers

INTRODUCTION: The current standard for arrhythmic risk stratification is electrophysiologic (EP) testing, which, due to its invasive nature, is limited to patients already known to be at high risk. A number of noninvasive tests, such as determination of left ventricular ejection fraction (LVEF) or heart rate variability, have been evaluated as additional risk stratifiers. Microvolt T wave alternans (TWA) is a promising new risk marker. Prospective evaluation of noninvasive risk markers in low- or moderate-risk populations requires studies involving very large numbers of patients, and in such studies, documentation of the occurrence of ventricular tachyarrhythmias is difficult. In the present study, we identified a high-risk population, recipients of an implantable cardioverter defibrillator (ICD), and prospectively compared microvolt TWA with invasive EP testing and other risk markers with respect to their ability to predict recurrence of ventricular tachyarrhythmias as documented by ICD electrograms. METHODS AND RESULTS: Ninety-five patients with a history of ventricular tachyarrhythmias undergoing implantation of an ICD underwent EP testing, assessment of TWA, as well as determination of LVEF, baroreflex sensitivity, signal-averaged ECG, analysis of 24-hour Holter monitoring, and QT dispersion from the 12-lead surface ECG. The endpoint of the study was first appropriate ICD therapy for electrogram-documented ventricular fibrillation or tachycardia during follow-up. Kaplan-Meier survival analysis revealed that TWA (P < 0.006) and LVEF (P < 0.04) were the only significant univariate risk stratifiers. EP testing was not statistically significant (P < 0.2). Multivariate Cox regression analysis revealed that TWA was the only statistically significant independent risk factor. CONCLUSIONS: Measurement of microvolt TWA compared favorably with both invasive EP testing and other currently used noninvasive risk assessment methods in predicting recurrence of ventricular tachyarrhythmias in ICD recipients. This study suggests that TWA might also be a powerful tool for risk stratification in low- or moderate-risk patients, and needs to be prospectively evaluated in such populations.     

Surgical treatment of aneurysms of the left ventricle. Immediate and long-term results. Apropos of a consecutive series of 121 cases

From 1978 to 1992, 121 cases of postinfarction left ventricular aneurysm (99 males, 22 females, mean age 60 years) were operated on. The authors insist on a high rate of clinical arhythmogenicity (31.4%) and associated mechanical complications (21%). 76% of patients were in functional NYHA class III or IV. Resection was performed in 90% of patients, plication in 10%. 58% underwent coronary artery bypass grafting (1.7 graft/patient), 16% encircling ventriculotomy, 8% mitral valve replacement and 13% closure of ventricular septal defect. Operative mortality was 14.9% (10% when other mechanical complications where excluded). 5-year survival is 67.9%. Late cardiac deaths are as follow: left ventricular failure (1.8% A/P), Sudden death (1.4% A/P), Myocardial infarction (0.6% A/P). 82% of survivals are in functional NYHA class I or II. Only functional class NYHA III or IV is predictive of late death. We conclude that postinfarction left ventricular aneurysm remains a high risk complication especially when associated with other mechanical complications. When arhythmogenicity is present we suggest rhythmologic surgery and in all cases, complete revascularization.     

Triple chamber pacemaker for end-stage heart failure in a patient with a previously implanted automatic defibrillator

A 63-year-old man with an ischemic dilated cardiomyopathy previously implanted with an implantable cardioverter defibrillator (ICD) received a triple chamber pacemaker as an ultimate therapeutic resort for end-stage congestive heart failure. After implant, the tolerance to physical exercise increased and NYHA class decreased from III to II. Echocardiography assessed ventricular contraction resynchronization during DDD biventricular pacing as compared to VVI pacing. No major pacemaker-ICD interaction was noted during testing or follow-up. We conclude that sequential biventricular pacing is feasible in the presence of an ICD.     

Implantable cardioverter-defibrillator therapy for prevention of sudden cardiac death

Patients with known symptomatic VT or VF are at high risk for sudden cardiac death. Various therapeutic choices can be used to reduce the incidence of arrhythmic sudden cardiac death. These include beta-blockers, class I and III antiarrhythmic agents, VT focal ablations, and ICD therapy. The overall incidence of sudden cardiac death in ICD recipients is less than 2% per year, a rate of survival not achieved with any of the available antiarrhythmic agents. VT surgical therapy can produce comparable survival results, but the minimal operative mortality is higher than that with ICD therapy. In patients with noninducible VT/VF or inducible polymorphic VT, and in those refractory to or intolerant of antiarrhythmic agents and poor left ventricular function, ICD therapy may be the only realistic option.     

RB protein status and chemosensitivity in non-small cell lung cancers

A total of 1,207 patients received a Medtronic Jewel active can ICD (models 7218C, 7219C), with a Transvene lead in 97 centers in Europe and North America. Nineteen implants were from the right pectoral region. Patients with right-sided ICDs did not differ in terms of mean age, % male, left ventricular ejection fraction, New York Heart Association Functional Class, antiarrhythmic drug therapy, indication for the implantable cardioverter defibrillator, and R wave values at implantation, but tended to have slightly higher pacing thresholds (1.2 +/- 0.5 V vs 1.0 +/- 0.6 V, P = 0.012) and higher defibrillation thresholds (14.7 +/- 6.4 J vs 11.5 +/- 6 J, P = 0.11) compared with patients with left sided implants. Patients with right-sided implants had a longer implantation time compared with patients with left-sided implants (118 +/- 70 minutes vs 91 +/- 46 minutes, P = 0.074). In follow-up, 5 patients with right-sided implantation received successful therapy for either ventricular fibrillation, (8 episodes) or ventricular tachycardia (5 episodes). No ineffective therapy from the device was delivered in any patients with right-sided implantation. Right-sided pectoral implants are feasible with the Medtronic Jewel active can ICD.     

Re-examination of the mutagenicity of ethylene glycol monobutyl ether to Salmonella tester strain TA97a

Widespread use of implantable cardioverter defibrillators (ICDs) for the treatment of ventricular tachycardia (VT) and ventricular fibrillation (VF) occurred in the late 1980s and early 1990s. Additionally, there has been increasing appreciation during this time for both the lack of efficacy and proarrhythmic activity of antiarrhythmic drugs to treat these cardiac arrhythmias. We evaluated the use of antiarrhythmic drugs from 1987 to 1991 (5-year period) at the time of ICD implantation in 25,450 patients. The use of all classes of antiarrhythmic agents decreased from 61% to 24% during this time period (P < 0.05). In addition, there was a significant reduction in antiarrhythmic agent use for each drug class (P < 0.05) with the exception of Class II agents (beta blockers). These changes in drug use occurred independent of any changes in age, sex, ejection fraction, prevalence of coronary artery disease, or type of ventricular arrhythmia (VT vs VF).     

Short-term and long-term outcome of left heart function after cardioverter defibrillator implantation

The usefulness and problems of implantable cardioverter defibrillators (ICD) were examined in patients with reduced heart function. Of 36 patients who received ICD for refractory ventricular tachycardia (VT) or ventricular fibrillation (VF), VT and/or VF was associated with underlying heart disease in 26 patients, and VF without underlying heart disease in 10. Of the former 26 patients, 13 with left ventricular ejection fraction (LVEF) of less than 30% were assigned to group A, 13 with LVEF of greater than 30% to group B, and the other 10 with idiopathic VF to group C. Intraoperative death, cardiac death due to heart failure, sudden death, functional status of the ICD, exacerbation of heart failure symptoms and complications were compared between the three groups. There were no intraoperative deaths in any of the groups. During the median follow-up period of 36 +/- 22 months, there was only one sudden death in group A. There were no significant differences between the three groups. There were five cardiac deaths in group A, but none in groups B or C. The cardiac death-free rates 12, 24, and 36 months after implantation in group A were 83%, 60% and 50%, respectively. These values significantly differed from those in groups B and C (p < 0.05). The number of patients who received defibrillation therapy was higher in group A (p < 0.05). Defibrillation therapy was administered earlier in group A than in groups B and C (p < 0.05). The incidence of exacerbation of heart failure after implantation was 69%, 23% and 0% in groups A, B, and C, respectively. In group A, defibrillation therapy was administered in all patients with exacerbation of heart failure. The administration of defibrillation therapy significantly differed from that in patients without exacerbation of heart failure (p < 0.05). Exacerbation of heart failure during the postoperative acute stage occurred in both patients in group A in whom an epicardial lead system was used, but not in the four patients in group B or five in group C (p < 0.05). There were no differences in the incidence of other complications between the three groups. In group A, patients with reduced heart function, ICD greatly decreased the risk of sudden death. However, heart failure mortality remained high. Therefore, ICD may have limitations for improved prognosis. In group A patients, defibrillation therapy was administered in all patients with exacerbation of heart failure or death due to heart failure. In patients with reduced heart function, treatment for heart failure and prophylaxis of VT and/or VF should be administered.     

Comparison of metoprolol and sotalol in preventing ventricular tachyarrhythmias after the implantation of a cardioverter/defibrillator

The purpose of this prospective study was to evaluate, on an intention-to-treat basis, the efficacy of d,l-sotalol and metoprolol with regards to the recurrence of arrhythmic events after implantable cardioverter defibrillator (ICD) implantation. After ICD implantation, 70 patients were randomly assigned to treatment with either metoprolol (mean dosage 104+/-37 mg/day in 35 patients) or d,l-sotalol (mean dosage 242+/-109 mg/day in 35 patients). During follow up ventricular tachycardia (VT), fast VT, and ventricular fibrillation (VF) episodes were calculated. Metoprolol treatment led to a marked reduction in the recurrence of arrhythmic events. Actuarial rates for absence of VT recurrence at 1 and 2 years were significantly higher in the metoprolol group compared with the d,l-sotalol group (83% and 80% vs 57% and 51%, respectively, p=0.016). The actuarial rates for absence of fast VT or VF were 80% in the metoprolol group compared with 46% in the d,l-sotalol group (p=0.002). During a follow up of 26+/-16 months, there were 3 deaths in the metoprolol group compared with 6 deaths in the d,l-sotalol group. Actuarial rates of overall survival were not significantly different in the 2 groups (91% vs 83%, p=0.287). In this prospective, randomized, controlled study the recurrence rate of ventricular tachyarrhythmias in patients treated with metoprolol was lower than in patients treated by d,l-sotolol.     

Results of atrioventricular synchronous pacing with optimized delay in patients with severe congestive heart failure

To verify that atrioventricular (AV) synchronous pacing (DDD) with short AV delay improves the condition of patients with severe congestive heart failure, we implanted DDD pacemakers in 10 patients with severe heart failure (New York Heart Association [NYHA] class III to IV). One day after pacemaker implantation, the AV delay was optimized by Doppler echocardiographic measurements over the aortic outflow tract. Patients were evaluated regarding NYHA class, stroke volume, cardiac output, ejection fraction, and quality of life at 1, 3, and 6 months after pacemaker implantation. Although the optimized AV delay was associated with short-term improvement in stroke volume and cardiac output (baseline stroke volume = 22 +/- 7 ml, day 1 = 28 +/- 12 ml; p = 0.03: baseline cardiac output = 1.9 +/- 0.6 L/min, day 1 = 2.2 +/- 1.1 L/min; p = 0.10), the mean stroke volume, cardiac output, NYHA class, and ejection fraction did not change significantly after 1, 3, and 6 months of pacing compared with baseline values. Three patients improved in NYHA class during the follow-up. A consistent improvement in stroke volume, cardiac output, NYHA class, and ejection fraction was observed in only 1 patient. In conclusion, we found no beneficial effects of AV-synchronous pacing with optimized AV delay in patients with severe heart failure.     

Circannual variation of malignant ventricular tachyarrhythmias in patients with implantable cardioverter-defibrillators and either coronary artery disease or idiopathic dilated cardiomyopathy

We studied the possible relation between the frequency of ventricular tachyarrhythmic events and thermal stress in patients with an implantable cardioverter-defibrillator (ICD) living in a locally limited area under homogeneous climatic conditions. The frequency of tachyarrhythmic events was correlated with the thermal stress level according to the "Klima Michel Model," a complete thermophysiologic model that calculates "felt-temperature" values on the basis of the outdoor temperature and further meteorologic data. During a mean follow-up time of 40 +/- 17 months (range 4 to 72), 761 ventricular tachyarrhythmic events occurred in 50 of 138 consecutive ICD recipients. Analysis of the monthly felt-temperature levels and the mean circannual variation of the registered ventricular arrhythmias suggested that very cold and very hot conditions may be associated with an increased frequency of ventricular tachyarrhythmias. This finding was confirmed by calculation of the sum of tachyarrhythmias on all 2,039 days of the follow-up period divided into 5-degree-step felt-temperature classes. Thus, thermal stress may be 1 factor triggering the occurrence of ventricular tachyarrhythmias in patients with cardiac disease and suppressed cardiac function. Part of the increase in cardiac mortality under above-average hot and cold atmospheric conditions may be attributed to ventricular arrhythmic events.