Influence of cardiac-resynchronization therapy on heart rate and blood pressure variability: 1-year follow-up

BACKGROUND: Several studies have shown that cardiac-resynchronization therapy (CRT) improves haemodynamic function, cardiac symptoms, and heart rate variability (HRV) and reduces the risk of mortality and sudden death in subjects with chronic heart failure (CHF). In subjects with CHF, power spectral values for the low-frequency (LF) component of RR variability < or =13 ms2, are associated with an increased risk of sudden death. AIMS AND METHODS: To assess whether spectral indexes obtained by power spectral analysis of HRV and systolic blood pressure (SBP) variability could predict malignant ventricular arrhythmias in patients with severe CHF treated with an implantable cardioverter-defibrillator (ICD) alone or with ICD+CRT. In addition, changes in non-invasive spectral indices using short-term power spectral analysis of HRV and SBP variability during controlled breathing in 15 patients with CHF treated with an ICD alone and 16 patients receiving ICD+CRT, were assessed pre-treatment and at 1 year. RESULTS: Arrhythmias necessitating an appropriate ICD shock were more frequent in subjects who had low LF power. CRT improved all spectral components, including LF power. CONCLUSIONS: Low LF power values predict an increased risk of malignant ventricular arrhythmias; after 1 year of CRT most non-spectral and spectral data, including LF power, improved. Whether these improvements lead to better long-term survival in patients with CHF remains unclear.     

Circadian and seasonal variation of malignant arrhythmias in a pediatric and congenital heart disease population

INTRODUCTION: Recent studies in adult populations have revealed seasonal variation in the frequency of acute cardiovascular events, including life-threatening arrhythmias, demonstrating increased events during winter and early spring. Trends in the time of day that arrhythmias occur also were noted. We sought to establish whether pediatric and young adult congenital heart disease implantable cardioverter defibrillator (ICD) recipients have circadian or seasonal variability in shock frequency, similar to adult populations. METHODS AND RESULTS: Data from ICD patients at six pediatric centers in North America were analyzed to assess the timing of life-threatening arrhythmias. The populations consisted of children and adults with congenital heart disease and ICDs placed for malignant arrhythmias. Data were considered in 46 patients who received appropriate therapy (total 139 episodes) for ventricular tachycardia or ventricular fibrillation. Multiple variables were analyzed, including time of day, day of week, and month of year. In contrast to previously studied adult patients, fewer events occurred in the early morning (7.5%), with the most therapies occurring between 6 P.M. and midnight (35%). An increased frequency of therapies was observed in the fall and winter (September-January), representing 60% of all appropriate shocks. Unlike adult populations, Mondays did not have an increased frequency of malignant arrhythmias. CONCLUSION: Pediatric and adult congenital heart disease populations have moderate seasonal and 24-hour variation in ICD event rate, with some distinctly different peaks than those seen in typical adult ICD populations. These findings suggest circadian variation in arrhythmia vulnerability that may differ from conventional occupational, physical, or emotional stressors. (J Cardiovasc Electrophysiol, Vol. 13, pp.     

Relation between heart rate variability and spontaneous and induced ventricular arrhythmias in patients with coronary artery disease

Objectives. The aim of this study was to determine the relation between autonomic control of heart rate and the spontaneous occurrence and inducibility of ventricular arrhythmias in patients with coronary artery disease.Background. Low heart rate variability increases the risk of arrhythmic events. It is not known whether impaired autonomic heart rate control reflects alterations in functional factors that contribute to the initiation of spontaneous arrhythmias or whether it is the consequence of an anatomic substrate for reentrant tachyarrhythmias.Methods. Fifty-four patients with coronary artery disease with a history of sustained ventricular tachycardia (n = 25) or cardiac arrest (n = 29) were studied by 24-h ambulatory electrocardiographic recording and by programmed electrical stimulation. Heart rate variability was compared among the patients with and without spontaneous ventricular arrhythmias and with and without inducibility of sustained ventricular tachyarrhythmias.Results. Eight patients had a total of 21 episodes of sustained ventricular tachycardia on Holter recordings. Standard deviation of RR intervals and low frequency and very low frequency components of heart rate variability were significantly blunted in patients with sustained ventricular tachycardias compared with those without repetitive ventricular ectopic activity (p < 0.05, p < 0.01 and p < 0.05, respectively). However, no significant alterations were observed in heart rate variability before the onset of 21 episodes of sustained ventricular tachycardia. Heart rate variability did not differ between the patients with or without nonsustained episodes of ventricular tachycardia. In patients with frequent ventricular ectopic activity, low frequency and very low frequency power components were significantly blunted compared with those with infrequent ventricular ectopic activity (p < 0.01 and p < 0.001, respectively). Heart rate variability did not differ significantly between the patients with and without inducible sustained ventricular tachyarrhythmias.Conclusions. Impaired very low and low frequency oscillation of heart rate reflects susceptibility to the spontaneous occurrence of ventricular arrhythmias but may not reflect the instantaneous triggers for life-threatening arrhythmias or a specific marker of the arrhythmic substrate for ventricular tachyarrhythmias.     

Single-center experience with implantable cardioverter-defibrillators in adults with complex congenital heart disease

Adults with congenital heart disease are at risk of lethal ventricular arrhythmias and are candidates for implantable cardiac defibrillator (ICD) therapy, yet implant risks, long-term outcomes, and rates of appropriate and inappropriate ICD therapies are not well characterized. We reviewed clinical, implantation, and follow-up data on all transvenous ICDs in adults with congenital heart disease at the Mayo Clinic from 1991 through 2008. Seventy-three adults with congenital heart disease received 85 ICDs. Implantation diagnoses included tetralogy of Fallot (44%) and congenitally corrected transposition of the great arteries (17%). Implantation indication was occurrence of sustained ventricular arrhythmias (secondary prevention) in 36% and prophylactic (primary prevention) in the remainder. There were no major implant-related complications. During follow-up (2.2 ± 2.8 years, range 0 to 15) 11 patients died and 4 patients received heart or heart/lung transplants. An appropriate shock for a ventricular arrhythmia was observed in 19% of patients and an inappropriate shock was observed in 15% of patients. Likelihood of an appropriate shock was associated with increased subpulmonic ventricular pressure. In conclusion, implantation of transvenous ICDs in adults with congenital heart disease is associated with a low risk of implant complications. In this high-risk adult population the rate of inappropriate ICD shocks is low, whereas the likelihood of appropriate therapy for potentially lethal ventricular arrhythmias is high. These data suggest overall benefit of ICD therapy in adults with congenital heart disease.     

Heart rate variability and its relation to ventricular arrhythmias in congestive heart failure.

BACKGROUND--It has been shown that heart rate variability is decreased in patients with congestive heart failure and that depressed heart rate variability is associated with a propensity to ventricular arrhythmias. Little is known, however, about heart rate variability in patients with both congestive heart failure and ventricular arrhythmias. METHODS--Spectral heart rate variability was analysed from 24 hour ambulatory electrocardiograms in 15 controls, 15 patients with non-sustained ventricular tachycardia associated with clinically normal hearts (NHVT group), and 40 patients with congestive heart failure (CHF group) secondary to either ischaemic heart disease (n = 15) or idiopathic dilated cardiomyopathy (n = 25). Of the 40 patients with congestive heart failure 15 had no appreciable ventricular arrhythmias (ventricular extrasystoles < 10 beats/h and no salvos) and formed the CHF-VA- group. Another 15 patients with congestive heart failure and non-sustained ventricular tachycardia formed the CHF-NSVT group. RESULTS--Heart rate variability was significantly lower in the CHF group than in controls (mean (SD) total frequency 23 (12) v 43 (13) ms; low frequency 12 (8) v 28 (9) ms; high frequency 8 (5) v 14 (7) ms; p < 0.001). The differences in heart rate variability between controls and the NHVT group, between ischaemic heart disease and dilated cardiomyopathy, and between the CHF-VA- and CHF-NSVT groups were not significant. In the CHF group heart rate variability was significantly related to left ventricular ejection fraction but not associated with ventricular arrhythmias. The frequency of ventricular extrasystoles was significantly related to the high frequency component of heart rate variability (r = 0.54, p < 0.05) in the NHVT group. Stepwise multiple regression analysis showed that in the CHF group, heart rate variability was predominantly related to left ventricular ejection fraction (p < 0.05). There was no significant difference in heart rate variability between survivors (n = 34) and those who died suddenly (n = 6) at one year of follow up in the CHF group. CONCLUSION--In patients with congestive heart failure, heart rate variability is significantly decreased. The depressed heart rate variability is principally related to the degree of left ventricular impairment and is independent of aetiology and the presence of ventricular arrhythmias. The data suggest that analysis of heart rate variability does not help the identification of patients with congestive heart failure at increased risk of sudden death.     

Benefit of combined resynchronization and defibrillator therapy in heart failure patients with and without ventricular arrhythmias.

OBJECTIVES: We attempted to assess the efficacy of combined cardiac resynchronization therapy-implantable cardioverter-defibrillator (CRT-ICD) in heart failure patients with and without ventricular arrhythmias. BACKGROUND: Because CRT and ICDs both lower all-cause mortality in patients with advanced heart failure, combination of both therapies in a single device is challenging. METHODS: A total of 191 consecutive patients with advanced heart failure, left ventricular ejection fraction <35%, and a QRS duration >120 ms received CRT-ICD. Seventy-one patients had a history of ventricular arrhythmias (secondary prevention); 120 patients did not have prior ventricular arrhythmias (primary prevention). During follow-up, ICD therapy rate, clinical improvement after 6 months, and mortality rate were evaluated. RESULTS: During follow-up (18 +/- 4 months), primary prevention patients experienced less appropriate ICD therapies than secondary prevention patients (21% vs. 35%, p < 0.05). Multivariate analysis revealed, however, no predictors of ICD therapy. Furthermore, a similar, significant, improvement in clinical parameters was observed at 6 months in both groups. Also, the mortality rate in the primary prevention group was lower than in the secondary prevention group (3% vs. 18%, p < 0.05). CONCLUSIONS: As 21% of the primary prevention patients and 35% of the secondary prevention patients experienced appropriate ICD therapy within 2 years after implant, and no predictors of ICD therapy could be identified, implantation of a CRT-ICD device should be considered in all patients eligible for CRT.     

Holter EKG for the hypertensive heart disease

During chronic mechanical overload induced by hypertension, left ventricular hypertrophy predisposes to atrial and ventricular arrhythmias. Atrial arrhythmias, mainly atrial fibrillation, decrease cardiac output and increase the risk of embolism whereas ventricular arrhythmias remain the major cause of sudden death. In hypertensive patients, Holter EKG recordings frequently detect atrial or ventricular premature beats and more rarely atrial or ventricular tachycardia. In these patients, the presence of non-sustained ventricular tachycardia is considered as an independent predictor of mortality. Moreover, this non invasive method through the assessment of heart rate variability allows the study of the autonomic control of the heart, known to modulate occurrence of arrhythmias.     

Repolarization variability in the risk stratification of MADIT II patients.

AIMS: QT variability has been reported to be associated with ventricular arrhythmias and sudden cardiac death. There is limited data regarding variability in T-wave morphology and its prognostic value. In this study, we present a novel approach for the measurement of T-wave variability (TWV) reflecting changes in T-wave morphology, and we investigate the prognostic significance of Holter-derived TWV in patients with and without ventricular arrhythmias requiring appropriate implantable cardioverter defibrillator (ICD) therapy from the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II). Methods Study population consisted of 275 ICD patients from MADIT II after excluding patients with intraventricular conduction abnormalities or atrial fibrillation. TWV was measured based on amplitude variance of T-wave amplitude. Results During 2-year follow-up, 58 (21%) patients had appropriate ICD therapy for ventricular tachycardia or fibrillation. Patients with appropriate ICD therapy had higher levels of TWV measures than those without arrhythmic events. After adjustment for heart rate, ejection fraction, and significant clinical predictors of arrhythmic events, a Cox proportional-hazards regression model revealed that dichotomized TWV values were predictive for ventricular tachyarrhythmias requiring appropriate ICD therapy (hazard ratio, 2.0; 95% CI; 1.2-3.5; P=0.01). On the basis of the comprehensive testing, TWV value >59 microV was found predictive for arrhythmic events in MADIT II population. CONCLUSION: Our newly designed method for the assessment of repolarization variability in ambulatory Holter recordings detected transient variability of T-wave morphology, which was predictive for ventricular tachyarrhythmias in the MADIT II population.     

老老年高血压病患者左心室肥厚与心律失常及心率变异性的关系研究

目的：研究老老年高血压患者左心室肥厚(LVH)与心律失常及心率变异性(HRV)的关系。方法：纳入2012年10月至2014年7月于中国中医科学院广安门医院心内科住院的303例老老年高血压病患者,根据是否合并左心室肥厚分为2组,检测24小时动态心电图心率变异性时域分析及超声心动图,观察2组之间相关指标的差异。结果：老老年高血压合并LVH组较不合并LVH组房性、室性心律失常检出率增高,差异具有统计学意义(P<0.05),二组PNN50、RMSSD、SDNN、SDANN差异无统计学意义。结论：老老年高血压合并LVH心律失常的发生率明显增高,而二者心率变异性无明显差异。     

Impact of sleep-disordered breathing on life-threatening ventricular arrhythmia in heart failure patients with implantable cardioverter-defibrillator

It was recognized that sleep-disordered breathing (SDB) is associated with cardiac arrhythmia and sudden cardiac death. However, it was unclear whether the presence of SDB increased the risk of life-threatening ventricular arrhythmia in patients with heart failure (HF) with an implantable cardioverter-defibrillator (ICD). Seventy-one patients with HF and an ICD who were followed up for 180 days after a sleep study were prospectively studied. All patients had an ejection fraction or=10 events/hour on the sleep study. The frequency of appropriate ICD therapy and the day-night pattern of ICD therapies were compared between patients with and without SDB. SDB was diagnosed in 47 of 71 patients (66%). There were no statistical differences between patients with and without SDB in baseline cardiac function. However, appropriate ICD therapies occurred more frequently in patients with (43%) than without SDB (17%; p = 0.029). On multivariate analysis, the presence of SDB was an independent predictor for appropriate ICD therapy (hazard ratio 4.05, 95% confidence interval 1.20 to 13.65, p = 0.015). Moreover, the rate of total ICD therapy from midnight to 6 A.M. was significantly higher in patients with (34%) than without SDB (13%; p = 0.046). In conclusion, in patients with HF with an ICD, the presence of SDB was common and an independent predictor of life-threatening ventricular arrhythmias that were more likely to occur during sleep.     

Use of the implantable cardioverter-defibrillator in long-term survivors of orthotopic heart transplantation

BACKGROUND: Orthotopic heart transplantation is considered an effective treatment for patients with refractory heart failure. The long-term survival of orthotopic heart transplantation recipients has increased over the last several decades, but many long-term survivors of orthotopic heart transplantation develop graft atherosclerosis and associated left ventricular dysfunction. The risk of sudden cardiac death in long-term survivors of orthotopic heart transplantation with these complications is believed to be high. There are no data on the usefulness of implantable cardioverter-defibrillators (ICDs) in this population; therefore, we report our early experience with ICD placement in such patients. OBJECTIVES: The purpose of this study was to examine the use of ICDs in adults who are long-term survivors of heart transplantation. METHODS: We retrospectively reviewed all adult patients who underwent orthotopic heart transplantation at Stanford University Hospital (Stanford, CA, USA) from 1980 to 2004. All patients who received an ICD after transplant were included in this study. We reviewed demographic data, medical history, ejection fraction, presence of graft atherosclerosis, indication for ICD placement, and any device therapy delivered. RESULTS: Of the 925 patients who had orthotopic heart transplantation during this time period, 493 patients were alive at the beginning of the year 2000. Of these patients, 10 ( approximately 2%) had subsequent placement of an ICD. All 10 patients were male. The average age at orthotopic heart transplantation was 37.8 years. The average age at ICD placement was 50.5 years. The average time from orthotopic heart transplantation to ICD placement was 14.6 years. The average ejection fraction at the time of implant was 46.5%. Five of the 10 patients had a low ejection fraction (within this subgroup, the average ejection fraction was 31%, range 15%-45%) and graft atherosclerosis. ICDs were placed because of symptomatic episodes of ventricular tachycardia (3 patients), low ejection fraction and severe graft atherosclerosis without symptoms (3 patients), and after thorough evaluation for otherwise unexplained syncope (4 patients). The average follow-up after device implantation was 13 months. Complications related to ICD placement were an infected ICD system requiring explant in one patient and a lead fracture in another patient. Three patients had subsequent appropriate shocks for ventricular arrhythmias, and one patient underwent a second orthotopic heart transplantation. One patient died of malignancy. CONCLUSION: Use of the ICD in long-term survivors of orthotopic heart transplantation should be considered in appropriately selected patients. Further data are needed regarding ICD use in this population.     

Clusters of life-threatening ventricular arrhythmias in patients with implanted cardioverter-defibrillators: prevalence, characteristics, and risk stratification

BACKGROUND: Series of discharges from an implanted defibrillator (ICD) to terminate life-threatening ventricular tachyarrhythmias are one particular aspect of energy use and success of ICD therapy. Little is known about prevalence. characteristics, and risk stratification of so-called "cluster arrhythmias." HYPOTHESIS: The objective of this study was to examine the frequency of cluster arrhythmias, to characterize the temporal relationship precisely, and to assess the accompanying circumstances of their occurrence, whereby risk stratification was to be made if appropriate. METHODS: In all, 63 consecutive patients were followed prospectively over 727 +/- 684 days to determine the presence and characteristics of cluster arrhythmias (45,801 patient days). In 30 patients, 374 ICD episodes of ventricular tachyarrhythmias were analyzed for their temporal relationship. After a first successfully terminated ventricular tachyarrhythmia, further ICD discharges within 3 h were observed during 145 of 374 (39%) episodes; mean time interval between these arrhythmias was 25 +/- 32 min. RESULTS: Arrhythmia clusters occurred in 19 of 30 (63%) patients. In multivariate analysis, only underlying heart disease was predictive for accumulation of ventricular tachyarrhythmias. Cluster arrhythmias were more frequent among patients with ischemic heart disease than among those with nonischemic heart disease (40.0 vs. 29.2%, p < 0.05). Ejection fraction, age, gender, and other parameters were not predictive for occurrence of arrhythmia clusters. In 4 of 19 patients, accumulation of ICD discharges was predictive for new onset of myocardial ischemia elicited by exercise test. CONCLUSIONS: Cluster arrhythmias are most common in patients with ICDs with coronary heart disease and may indicate disease progression and increasing instability, for example, due to new onset of myocardial ischemia.     

Implications of implantable cardioverter defibrillator therapy in congenital heart disease and pediatrics

INTRODUCTION: The incidence of appropriate and inappropriate discharges, indicators of system failure, and clinical implications of implantable cardioverter defibrillator (ICD) therapy in children and young adults with heart disease is poorly defined. METHODS AND RESULTS: In a retrospective study at a single medical center, a total of 90 ICD procedures were performed in 76 patients younger than age 30 years (median 16 years, range 1-30): 42% with congenital heart disease, 33% with primary electrical disease, 17% with hypertrophic cardiomyopathy, and 8% with idiopathic dilated cardiomyopathy. Indications for ICD included arrest or sustained ventricular tachycardia (n = 27), and combinations of syncope (n = 32), palpitations (n = 17), spontaneous ventricular arrhythmia (n = 40), inducible ventricular tachycardia (n = 36), or severe hypertrophic cardiomyopathy. Transvenous dual-chamber ICDs were implanted in 29 patients. Subcutaneous arrays or epicardial patches were used in 9 patients. Over a median 2-year follow-up, 28% of patients received appropriate shocks for ventricular tachycardia (median 13 months to first shock) and 25% experienced inappropriate shocks for multiple causes (median 16 months). With multivariate analysis, growth strongly correlated with lead failure (odds ratio 73, 3.5-1530, P = 0.006). Complications occurred in 29 patients, including lead failure in 16 (21%), ICD "storm" with sequential shocks in 5, and infection in 2 patients. No deaths were attributable to ICD placement or subsequent device failure. CONCLUSION: ICD therapy can effectively manage malignant arrhythmias in selected pediatric and congenital heart patients. Spurious shocks or ICD storm may increase morbidity and emphasize the need for concomitant medical and ablative therapy. ICD lead failure was relatively frequent in this population.     

His bundle ablation for supraventricular arrhythmias to avoid spurious shocks of an implanted defibrillator

Atrial fibrillation with fast ventricular response remains a matter of concern in patients treated with an implantable cardioverter defibrillator (ICD). A patient with dilated cardiomyopathy, suffering from atrial arrhythmias and recurrent cardiac arrest due to both ventricular tachycardia and ventricular fibrillation, is presented. Ablation of the AV node by means of low-energy direct-current shocks with subsequent pacemaker implantation was performed before ICD implantation. The patient received shocks after four months, when he had recurrence of AV conduction with a slow ventricular rate. Pacemaker interaction was excluded, and no short ventricular arrhythmias were observed. During electrophysiologic study after electrical conversion of atrial fibrillation, persistent second degree heart block was documented, giving further evidence that atrial arrhythmias were not responsible for the shocks. The patient's functional status remains good after more than 18 months of follow-up.     

Wavelet transform for analysis of heart rate variability preceding ventricular arrhythmias in patients with ischemic heart disease

INTRODUCTION: Studies evaluating changes in HRV preceding the onset of ventricular arrhythmias using conventional techniques have shown inconsistent results. Time-frequency analysis of HRV is traditionally performed using short-term Fourier transform (STFT). Wavelet transform (WT) may however be better suited for analyzing non-stationary signals such as heart rate recordings. METHODS AND RESULTS: We studied patients with a history of myocardial infarction implanted with a defibrillator with an extended memory. The RR intervals during the 51 min preceding ventricular events requiring electrical therapy were retrieved, and HRV studied by WT and STFT. 111 episodes of ventricular arrhythmia were retrieved from 41 patients (38 males, age 64 +/- 8 years). Heart rate increased significantly before arrhythmia. There was no significant variation in low frequency / high frequency components (LF/HF) observed for the group as a whole, probably due to a great degree of heterogeneity amongst individuals. A subset of 30 patients also had heart rate recordings performed during normal ICD follow-up. WT did not show any difference in HRV before arrhythmia onset and during control conditions. CONCLUSION: Variations in HRV before onset of ventricular arrhythmias were not apparent in this large dataset, despite use of optimal tools for studying time-frequency analysis.     

The use of implantable cardioverter-defibrillators in pediatric patients awaiting heart transplantation

BACKGROUND: This multicenter study evaluated experience with implantable cardioverter defibrillators (ICD) as a bridge to orthotopic heart transplantation (OHT) in children. METHODS: The application of ICD therapy continues to expand in pediatric populations, due in part to improved technology and new indications, including the prevention of sudden death while awaiting OHT. METHODS: We performed a retrospective review of ICD databases at 9 pediatric transplant centers. RESULTS: Twenty-eight patients (16 males) underwent implantation or had a preexisting ICD while awaiting OHT between 1990 and 2002. The median age at implant was 14.3 years (11 months to 21 years) with a median weight of 49 kg (11.7-88 kg). Diagnoses included cardiomyopathy (n=22), and congenital heart disease (n=6). Indications for ICD implantation included ventricular tachycardia/fibrillation (n=23), syncope (n=5), aborted sudden death with no documentation of rhythm disturbance (n=5), ventricular ectopy (n=1), and poor function (n=5). Of the 28 ICDs, 23 were implanted by a transvenous approach and 5 by epicardial route. There were 55 defibrillator discharges in 17 patients, 47 (85%) of which (in 13 patients) were appropriate. The 8 inappropriate discharges (in 6 patients) were triggered by sinus tachycardia, inappropriate sensing, and atrial flutter. The mean time from implantation to first appropriate shock was 6.9 months (1 day to 2.6 years). Twenty-one patients underwent transplantation during the study period, whereas 2 died while awaiting a donor. Morbidity included a lead fracture, 3 episodes of electromechanical dissociation, and 1 episode of electrical storm. CONCLUSIONS: ICD implantation represents an effective bridge to transplantation in pediatric patients. The complication rate is low, with inappropriate device discharge due primarily to sinus tachycardia or atrial flutter. There is a high incidence of appropriate ICD therapy for malignant ventricular arrhythmias in this highly selected group of patients.     

Effect of sotalol on heart rate variability assessed by Holter monitoring in patients with ventricular arrhythmias

Reduced vagal activity has been demonstrated to be associated with an increased risk of sudden death. Assessing the heart rate variability as a measure of the autonomic control of the heart has been established as a useful tool for the risk stratification of patients after myocardial infarction. In the current study, heart rate variability assessed by time- and frequency-domain measures was determined from Holter recordings before and during treatment with sotalol in 28 patients wtth chronic ventricular arrhythmias. The heart rate variability at baseline was independent of the presence or absence of spontaneous arrhythmias and of left ventricular function. Therapy with sotalol produced a significant improvement over control values in indices of parasympathetic tone (root mean square of the difference in successive RR intervals, proportion of adjacent RR intervals different by > 50 msec, high-frequency power spectrum). This improvement was not related to drug-induced changes in the mean heart rate or the suppression of ventricular ectopic activity. These effects on heart rate variability may contribute significantly to the overall efficacy profile of sotalol.     

Value of programmed ventricular stimulation for prophylactic internal cardioverter-defibrillator implantation in postinfarction patients preselected by noninvasive risk stratifiers

OBJECTIVES: The aim of this prospective study was to evaluate the role of programmed ventricular stimulation (PVS) after noninvasive risk stratification to identify a subgroup of acute myocardial infarction (AMI) survivors considered at risk for ventricular arrhythmias and whether these patients could benefit from internal cardioverter-defibrillators (ICDs). BACKGROUND: The predictive value of noninvasive and invasive risk stratifiers after AMI has been questioned. The question of whether the group of patients with inducible monomorphic ventricular tachycardia (VT) after AMI could profit from ICD implantation is unanswered. METHODS: A consecutive series of 1,436 AMI survivors was screened noninvasively by Holter monitoring, heart rate variability, ventricular late potentials, and ejection fraction. A subgroup of 248 patients (17.3%) were identified as high-risk patients and scheduled for PVS. Due to the study design, 54 patients >75 years were excluded; thus, 194 patients were eligible for PVS. Triple extrastimuli at two paced cycle lengths (600 ms and 400 ms) were applied. RESULTS: In a subgroup of 98 (51%) high-risk patients, PVS was performed; 21 patients had an abnormal response, and in 20 patients an ICD was implanted. During a mean follow-up of 607 days the arrhythmic event rate (sudden cardiac death, symptomatic VT, cardiac arrest) was 33% with a positive electrophysiological test versus 2.6% (p < 0.0001) with a negative electrophysiological test. A subgroup of 96 high-risk patients declined electrophysiological study. In this nonconsent group, cardiac mortality (combined sudden and nonsudden) was significantly higher (log-rank chi-square 9.38, p = 0.0022, relative risk 4.7, 1.6 to 13.9) compared to the group guided by electrophysiological testing and consecutive ICD implantation. CONCLUSIONS: After a two-step risk stratification, PVS is helpful in selecting a subgroup of AMI survivors without spontaneous ventricular arrhythmias who benefit from prophylactic ICD implantation.     

植入型心律转复除颤器治疗冠心病伴室性心律失常疗效观察

目的 观察冠心病伴恶性室性心律失常患者植入心律转复除颤器(ICD)治疗后的长期预后.方法 23例冠心病患者,其中男性18例,女性15例,年龄(71.56±10.38)岁.心功能不良16例.22例行血运重建术(经皮冠状动脉介入术20例,冠状动脉搭桥术2例).术后发生晕厥9例,持续性室性心动过速(VT)发作22例,心室颤动(VF)发作5例.植入单腔ICD(VVI)15例,双腔ICD(DDDR)1例,三腔ICD(CRT-D)7例.随访时间平均为(33.37±25.39)个月.结果 (1)死亡2例,因急性心肌梗死和急性左心衰竭死亡各1例.(2)4例患者术后再次住院.原因:1例为心功能不良,3例为ICD多次放电住院.(3)13例(56.5%)发生持续性VT或VF事件.持续性VT发作434次,386次(98.6%)经抗心动过速起搏(ATP)治疗成功.FVT发作25次,ATP治疗FVT总的成功率为84.0%.(4)ICD电风暴3例.(5)ICD误识别及误治疗2例.结论 冠心病伴恶性室性心律失常患者血运重建后用ICD治疗,可防止由于心肌的慢性的瘢痕产生室性心律失常而导致猝死的风险.     

Arrhythmias in heart failure: current concepts of mechanisms and therapy

About one half of deaths in patients with heart failure are sudden, mostly due to ventricular tachycardia (VT) degenerating to ventricular fibrillation or immediate ventricular fibrillation. In severe heart failure, sudden cardiac death also may occur due to bradyarrhythmias. Other dysrhythmias complicating heart failure include atrial and ventricular extrasystoles, atrial fibrillation (AF), and sustained and nonsustained ventricular tachyarrhythmias. The exact mechanism of the increased vulnerability to arrhythmias is not known. Depending on the etiology of heart failure, different preconditions, including ischemia or structural alterations such as fibrosis or myocardial scarring, may be prominent. Reentrant mechanisms around scar tissue, afterdepolarizations, and triggered activity due to changes in calcium metabolism significantly contribute to arrhythmogenesis. Furthermore, alterations in potassium currents leading to action potential prolongation and an increase in dispersion of repolarization play a significant role. Treatment of arrhythmias is necessary either because patients are symptomatic or to reduce the risk for sudden cardiac death. The individual history, left ventricular function, electrophysiologic testing, and the signal-averaged ECG give useful information for identifying patients at risk for sudden cardiac death. The implantable cardioverter defibrillator (ICD) has evolved as a promising therapy for life-threatening arrhythmias. A potential role may exist for antiarrhythmic drugs, mainly amiodarone. There is growing evidence that patients with sustained VT or a history of resuscitation have the best outcome with ICD therapy regardless of the degree of heart failure. Many of these patients require additional antiarrhythmic therapy because of AF or nonsustained VTs that may activate the device. Catheter ablation or map-guided endocardial resection are additional options in selected patients but seldom represent the only therapeutic strategy.