New implantable cardiac monitor with three-lead ECG and active noise detection.

BACKGROUND: A new implantable cardiac monitor (BioMonitor, Biotronik) with a continuous remote monitoring option was prospectively implanted in patients with suspected arrhythmias or for therapy control after atrial fibrillation (AF) ablation. A three-lead ECG detection was intended to make the implantation more independent of the implantation site and the electrical heart axis. Because noise is a frequent problem in implantable cardiac monitors, an active noise detection algorithm was implemented. The aim of the trial was to evaluate the clinical performance of the device. METHODS: The device performance was evaluated in a prospective nonrandomized multicenter study with a follow-up of 12 months. Study endpoints were device-related serious adverse events at 3 months, appropriate QRS detection in direct comparison with synchronized Holter ECG recordings, sensitivity and positive predictive value of arrhythmia detection in comparison with Holter ECG and independent of it, and noise burden during the entire follow-up period. RESULTS: The implantation was successful in all 152 patients. Two device-related serious adverse events (pocket infections) occurred by 3 months. The mean QRS amplitude of 0.3 ± 0.2 mV at implantation remained stable over 12 months. QRS sensing performance indicated little over- and undersensing in most patients. More than 80 % of the patients had more than 22 h of noise-free monitoring per day. CONCLUSION: BioMonitor effectively detects patients with bradycardia, tachycardia, AF, or asystole. Active noise detection seems to reduce the transmission of meaningless data without diminishing the positive predictive value of the device.

[Treatment of syncope]. / Therapie der Synkope.

The therapy of patients with syncope is oriented to the underlying pathophysiological mechanisms. Patients with reflex syncope require careful education regarding recognition of warning signs and the avoidance of trigger factors. Treatment with beta blockers is nowadays obsolete. Even other drugs have failed to show any benefit. Pacemaker therapy should only be considered if syncope attacks are frequent and if there is a correlation between symptoms and the electrocardiogram (ECG). Because autonomic failure in patients with orthostatic hypotension is often drug-induced, reduction of the dosage or the complete elimination is the treatment of choice in these patients. A higher than normal salt and fluid intake as well as general measures to avoid delayed venous backflow, e.g. elastic stockings, may also be helpful. A change in blood pressure medication can be decisive for therapy success, especially in elderly patients with arterial hypertension. Pacemaker and defibrillator therapy is the treatment of choice in patients with bradycardia and tachycardia arrhythmias, respectively. Although these measures are simple but effective, in individual cases it is still difficult to find clinical proof that arrhythmic disorders are the causal factors for the syncope. However, also in these patients cardiac pacing should be based on a symptom ECG correlation. The recently conducted market release of the injectable miniaturized ECG recorder will alleviate the diagnostic process. The limits of this approach, however, become obvious when there is the suspicion of a life-threatening rhythm disorder, because the only difference between syncope and sudden cardiac death is that in one case the patient wakes up again.

Republished: Improving hand hygiene in a paediatric hospital: a multimodal quality improvement approach.

BACKGROUND: Effective hand hygiene has long been recognised as an important way to reduce the transmission of bacterial and viral pathogens in healthcare settings. However, many studies have shown that adherence to hand hygiene remains low, and improvement efforts have often not delivered sustainable results. The Children's Hospital at Westmead is the largest tertiary paediatric hospital in Sydney, Australia. The hospital participated in a state-wide 'Clean hands save lives' campaign which was initiated in 2006. INTERVENTION: Strong leadership, good stakeholder engagement, readily accessible alcohol-based hand rub at the point of patient care, a multifaceted education programme, monitoring of staff, adherence to recommended hand hygiene practices and contemporaneous feedback of performance data have significantly improved and maintained compliance with hand hygiene. RESULTS: Hand hygiene compliance has increased from 23% in 2006 to 87% in 2011 (p<0.001). Sustained improvement in compliance with hand hygiene has been evident in the last 4 years. A decline in a set of hospital-acquired infections (including rotavirus, multiresistant organism transmission, and nosocomial bacteraemia) has also been noted as hand hygiene rates have improved. Monthly usage of alcohol-based hand rub has increased from 16 litres/1000 bed days to 51 litres/1000 bed days during this same period. CONCLUSION: This project has delivered sustained improvement in hand hygiene compliance by establishing a framework of multimodal evidence-based strategies.

Use of empiric antimicrobial therapy in neutropenic fever. Australian Consensus Guidelines 2011 Steering Committee.

Administration of empiric antimicrobial therapy is standard practice in the management of neutropenic fever, but there remains considerable debate about the selection of an optimal regimen. In view of emerging evidence regarding efficacy and toxicity differences between empiric treatment regimens, and strong evidence of heterogeneity in clinical practice, the current guidelines were developed to provide Australian clinicians with comprehensive guidance for selecting an appropriate empiric strategy in the setting of neutropenic fever. Beta-lactam monotherapy is presented as the treatment of choice for all clinically stable patients while early treatment with combination antibiotic therapy is considered for patients at higher risk. Due consideration is given to the appropriate use of glycopeptides in this setting. Several clinical caveats, accounting for institution- and patient-specific risk factors, are provided to help guide the judicious use of the agents described. Detailed recommendations are also provided regarding time to first dose, timing of blood cultures, selection of a first-line antibiotic regimen, subsequent modification of antibiotic choice and cessation of therapy.

A close shave? Performance of P2/N95 respirators in healthcare workers with facial hair: results of the BEARDS (BEnchmarking Adequate Respiratory DefenceS) study.

P2/N95 filtering face piece respirators (FFRs) protect healthcare workers (HCWs) from airborne infections. This study assessed the impact of facial hair on quantitative respirator fit in 105 male HCWs, of whom 38 were clean shaven, and assessed the prevalence of male facial hair at the study facility. Only 34 (32%) male HCWs overall achieved an adequate FFR fit, including 47% of clean-shaven men. No full-bearded HCWs achieved a fit. Adequate respirator fit decreased significantly with increasing facial hair (P<0.01 for trend). Facial hair was present on 49% of male employees. This study supports quantitative fit testing prior to P2/N95 respirator use.

Persistent histone modifications at the BDNF and Cdk-5 promoters following extinction of nicotine-seeking in rats.

Drugs of addiction lead to a wide range of epigenetic changes at the promoter regions of genes directly implicated in learning and memory processes. We have previously shown that the histone deactylase inhibitor, sodium butyrate (NaB), accelerates the extinction of nicotine-seeking and provides resistance to relapse. Here, we explore the potential molecular mechanisms underlying this effect. Rats received intravenous nicotine or saline self-administration, followed by 6 days of extinction training, with each extinction session followed immediately by treatment with NaB or vehicle. On the last day of extinction, rats were killed and the medial ventral prefrontal cortex retained for chromatin immunoprecipitation and quantitative polymerase chain reaction (qPCR). A history of nicotine exposure significantly decreased H3K14 acetylation at the brain-derived neurotrophic factor (BDNF) exon IV promoter, and this effect was abolished with NaB treatment. In contrast, nicotine self-administration alone, resulted in a significant decrease in histone methylation at the H3K27me3 and H3K9me2 marks in the promoter regions of BDNF exon IV and cyclin-dependent kinase 5 (Cdk-5). Quantitative PCR-identified changes in several genes associated with NaB treatment that were independent of nicotine exposure; however, an interaction of nicotine history and NaB treatment was detected only in the expression of BDNF IV and BDNF IX. Together these results suggest that nicotine self-administration leads to a number of epigenetic changes at both the BDNF and Cdk-5 promoters, and that these changes may contribute to the enhanced extinction of nicotine-seeking by NaB.

Venous thromboembolism in a general hospital. An update with low molecular weight heparin prophylaxis.

BACKGROUND: Patients admitted to hospital for surgery or acute medical illnesses have a high risk for venous thromboembolism (VTE). Today's widespread use of low molecular weight heparins (LMWH) for VTE prophylaxis is supposed to have reduced VTE rates substantially. However, data concerning the overall effectiveness of LMWH prophylaxis is sparse. PATIENTS AND METHODS: We prospectively studied all patients with symptomatic and objectively confirmed VTE seen in our hospital over a three year period. Event rates in different wards were analysed and compared. VTE prophylaxis with Enoxaparin was given to all patients at risk during their hospital stay. RESULTS: A total of 50 464 inpatients were treated during the study period. 461 examinations were carried out for symptoms suggestive of VTE and yielded 89 positive results in 85 patients. Seventy eight patients were found to have deep vein thrombosis, 7 had pulmonary embolism, and 4 had both deep venous thrombosis and pulmonary embolism. The overall in hospital VTE event rate was 0.17%. The rate decreased during the study period from 0.22 in year one to 0,16 in year two and 0.13 % in year three. It ranged highest in neurologic and trauma patients (0.32%) and lowest (0.08%) in gynecology-obstetrics. CONCLUSIONS: With a simple and strictly applied regimen of prophylaxis with LMWH the overall rate of symptomatic VTE was very low in our hospitalized patients. Beside LMWH prophylaxis, shortening hospital stays and substantial improvements in surgical and anesthesia techniques achieved during the last decades probably play an essential role in decreasing VTE rates.

Predictors of Atrial Fibrillation Recurrence after Catheter Ablation: Data from the German Ablation Registry.

Catheter ablation (CA) for atrial fibrillation (AF) has emerged as a widespread first or second line treatment option. However, up to 45% of patients (pts) show recurrence of AF within 12 month after CA. We present prospective multicenter registry data comparing characteristics of pts with and without recurrence of AF within the first year after CA. This study comprises all pts with complete follow-up one year after CA (1-y-FU; n = 3679). During 1y-FU in 1687 (45.9%) pts recurrence of AF occurred. The multivariate analysis revealed female sex and AF type prior to the procedure as predictors for AF recurrence. Furthermore, comorbidities such as valvular heart disease and renal failure as well as an early AF relapse were also predictors of AF recurrence during 1-y-FU. However, despite an AF recurrence rate of 45.9%, the majority of these pts (72.4%) reported a significant alleviation of clinical symptoms. In conclusion in pts with initially successful CA for AF female sex, AF type, in-hospital AF relapse and comorbidities such as renal failure and valvular heart disease are independent predictors for AF recurrence during 1-y-FU. However, the majority of pts deemed their interventions as successful with significant reduction of symptoms irrespective of AF.

Effect of oxprenolol on ventricular arrhythmias: the European Infarction Study experience.

In 736 patients, 24 hour electrocardiographic recordings were performed 14 to 36 days after acute myocardial infarction before the start of randomized treatment with 320 mg of slow release oxprenolol (n = 358) or placebo (n = 378). Follow-up 24 hour electrocardiographic recordings were obtained 5 to 12 days (median 10) and 3, 6 and 12 months after the first administration of the study medication. Oxprenolol-treated patients had a significantly lower daytime heart rate as compared with the placebo group, whereas no difference was found at night. At baseline, 22.1% of the patients allocated to oxprenolol treatment and 29.6% of the placebo group had more than 30 ventricular extrasystoles in 1 hour at least once during 24 hour monitoring; multiform ventricular extrasystoles were present in 58.4 and 62.7%, ventricular couplets in 29.6 and 33.9% and ventricular tachycardia (3 or more consecutive ventricular extrasystoles) in 21.5 and 20.9% of the oxprenolol-treated and placebo-treated patients, respectively. During the 1 year follow-up period, the prevalence of these arrhythmias did not change significantly in either treatment group. There was a trend toward a reduction in the daytime frequency of ventricular couplets in the oxprenolol group. After 3 and 6 months, only multiform ventricular extrasystoles were significantly less frequent in the oxprenolol group than in the placebo group (47.4 and 42.7% versus 59.7 and 57.9%, respectively). Twelve months after the acute event, however, multiform ventricular extrasystole frequency was the same in both groups of patients (52.1 versus 51.0%, respectively). Thus, oxprenolol had a weak suppressant effect on ventricular tachyarrhythmias in survivors of myocardial infarction.

Risk stratification following myocardial infarction in the thrombolytic era: a two-step strategy using noninvasive and invasive methods.

OBJECTIVES: We prospectively performed a two-step risk assessment in patients in the early phase after acute myocardial infarction (MI). BACKGROUND: Noninvasive methods like Holter electrocardiographic monitoring (HM) and determination of the left ventricular ejection fraction (EF) as well as the invasive technique of programmed ventricular stimulation (PVS) have been used to identify patients in the late phase after MI as candidates for prophylactic implantation of a cardioverter/defibrillator. However, it is unclear whether these results can be transferred to patients following acute MI. METHODS: A series of 657 patients with acute MI (< or = 75 years) underwent HM and EF. If one of the two methods yielded abnormal findings (HM > or = 20 ventricular ectopic beats/h/> or =10 ventricular pairs/day/ventricular tachycardia; EF < or = 40%), PVS was done (abnormal PVS: induction of monomorphic ventricular tachycardia, duration >10 s, cycle length > or = 230 ms). RESULTS: Of 657 patients, 304 (46%) had either an abnormal HM or EF. The PVS performed in 146 of 304 patients was abnormal in 22. During a mean follow-up of 37 months, there were 106 (16%) deaths, being sudden in 24 (3.6%), nonsudden cardiac in 45 (6.8%). The incidence of arrhythmic events (sudden cardiac death, symptomatic ventricular tachycardia, cardiac arrest) was 18% (4/22) with an abnormal PVS and only 4% (5/124) with a normal PVS (odds ratio 4.0, p=0.032). CONCLUSIONS: The rate of arrhythmic events is low in post-MI patients in the 1990s. Nevertheless, a two-step risk stratification is helpful in selecting candidates for a defibrillator trial aiming at primary prevention of sudden cardiac death after MI.

[Epidemiology of sudden cardiac death]. / Epidemiologie des akuten Herz-Kreislaufstillstandes.

Sudden cardiac death remains a major challenge that we are still facing today. The complexity of the trigger mechanisms makes it difficult to achieve a reliable identification of high-risk patients. Three suggestions are made that might help to overcome this epidemiological catastrophe "Sudden Cardiac Death". 1. In patients with known heart disease risk stratification has to be improved by developing new methods to identify specifically those individuals, who are at risk for sudden rather than non-sudden cardiac death. 2. The general population contains an unknown proportion of individuals with advanced coronary disease, which is commonly asymptomatic. In these so called "normal population" classical risk stratification does not work. However, since there is a close relationship between the prevalence of risk factors for coronary disease and sudden death, a consequent treatment of risk factors should have a positive effect on sudden death rate as well. 3. The success rate of resuscitation has to be improved by strengthening each single link of the "chain of survival". Laypersons trained in basic and advanced life support techniques have to play a much major role on this scene.

Beta blockers: evidence versus wishful thinking.

Catecholamines and ischemia play an important role in the induction of ventricular tachyarrhythmias. Beta blockers antagonize the effect of catecholamines and have anti-ischemic properties. Several controlled studies performed in the early 1980s in patients after myocardial infarction have shown that beta-blocker therapy clearly decreases sudden and nonsudden cardiac death. Despite the lack of recent randomized trials, data from uncontrolled studies suggest that the beneficial effect of beta blockers is still present in the thrombolytic era. Thus, it is incomprehensible that today in the United States and in most parts of Europe, < 40% of post-myocardial infarction patients are treated with beta blockers. Even in patients with documented sustained ventricular tachycardias (VTs) or ventricular fibrillation (VF), clinical studies indicate that beta blockers improve survival. Thus, even in the thrombolytic era, beta blockers should be used as a basic therapy in patients who are at risk of sudden cardiac death.

Prognostic value of ischemia during Holter monitoring and exercise testing after acute myocardial infarction.

Exercise testing is generally accepted for prognostic assessment of patients after infarction, but the prognostic value of transient myocardial ischemia during ambulatory electrocardiographic monitoring remains controversial. Of 281 consecutive postinfarction patients, 173 patients (132 men, 41 women) were prospectively studied with 24-hour Holter monitoring 14 +/- 5 days after acute myocardial infarction, and with submaximal exercise testing after 15 +/- 7 days. Patients with either conduction disturbances or pacemaker rhythm and 71 patients with digitalis medication were excluded. Myocardial ischemia was defined as horizontal or descending ST depressions or transient ST elevations > or = 0.1 mV with or without angina pectoris. The follow-up period was 1 year. Myocardial ischemia was observed in 40 patients (23%) during Holter monitoring, and 96% of the episodes were asymptomatic. Ischemia occurred during exercise testing in 46 patients (27%), two thirds of whom had no symptoms. Ischemia was detected by both methods (group A) in 19 patients (11%), with exercise testing only (group B) in 27 patients (16%), and with Holter monitoring only (group C) in 21 patients (12%). In 106 patients (61%), ischemia could not be ascertained at all. The 4 groups were comparable with regard to sex and age distribution, coronary risk factors, and medication. During follow-up, 50 patients (29%) experienced clinical cardiac events: 6 patients died, 7 had recurrent myocardial infarction, 14 developed unstable angina pectoris and required immediate revascularization, and 23 patients had recurrent but stable angina.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognosis of patients with sustained ventricular tachycardia and of survivors of cardiac arrest not inducible by programmed stimulation.

The aim of this study was to analyze the long-term clinical outcome of 60 prospectively studied patients with documented sustained ventricular tachyarrhythmia that was not inducible during baseline programmed ventricular stimulation: 39 with cardiac arrest due to noninfarction ventricular fibrillation (VF) and 21 with mild hemodynamically compromising sustained ventricular tachycardia (VT). Left ventricular ejection fraction was 55 +/- 14% in the VF group and 50 +/- 13% in the VT group (difference not significant). Patients were discharged without conventional antiarrhythmic drugs and received only empirical beta-blocker therapy. During a mean follow-up period of 21 +/- 16 months (mean +/- SD), 10 of 60 patients (17%) died suddenly. The actuarial incidence of sudden death at 1 and 4 years was similar in both groups (VF group, 10 and 20%; VT group, 16 and 16%) (p = 0.48). The actuarial incidence of sudden cardiac death was significantly higher in patients with left ventricular ejection fraction < or = 40% than in those with > 40% (1-year incidence in VF group, 40 vs 0%; VT group, 50 vs 0%) (p = 0.005 and p = 0.01, respectively). Multivariate regression analysis identified left ventricular ejection fraction < or = 40% and previous myocardial infarction as the only independent predictor of sudden cardiac death. The occurrence of frequent ventricular pairs during Holter monitoring was the only independent predictor of sustained VT recurrences. It is concluded that patients with sustained ventricular tachyarrhythmia in whom arrhythmia was non-inducible during baseline ventricular stimulation and not treated with antiarrhythmic therapy have a favorable outcome if left ventricular ejection fraction is high.(ABSTRACT TRUNCATED AT 250 WORDS)

First- or second-degree atrioventricular block as a risk factor in idiopathic dilated cardiomyopathy.

To evaluate the significance of clinical, hemodynamic and electrocardiographic risk factors in idiopathic dilated cardiomyopathy 94 patients were followed prospectively for 49 +/- 37 months. During follow-up, 30 patients died, 13 died suddenly, 13 died of congestive heart failure and 4 of other causes. Follow-up was completed in 85 patients, and overall cardiac mortality was 31%. Univariate analysis revealed left ventricular ejection fraction among 20 variables as the major indicator of risk of both cardiac death of all causes and sudden cardiac death separately. Multivariate overall analysis determined 3 independent risk factors in the following order for all causes of cardiac death: Ventricular pairs > 40/24 hours (RR 7.2, p < 0.0001), left ventricular ejection fraction < or = 35% (RR 6.5, p < 0.001) and first- or second-degree atrioventricular (AV) block (RR 3.1, p < 0.05). In the subset of patients with ejection fraction < or = 35% ventricular pairs > 40 per 24 hours (RR 10.7, p < 0.001), AV block (RR 3.9, p < 0.05), and the missing administration of vasodilators (RR 3.3, p < 0.05) were the most important. The chief risk factors for sudden cardiac death were age (RR 7.4, p < 0.01) and AV block (RR 4.6, p < 0.05) by adjustment for age, and ejection fraction < or = 35% (RR 7.1, p < 0.01) and AV block (RR 4.2, p < 0.05) if not adjusted for age. A differentiation into 4 risk groups was attempted. The additional independent prognostic importance of AV block was shown, especially in combination with reduced ejection fraction or a high incidence of ventricular pairs.(ABSTRACT TRUNCATED AT 250 WORDS)

Significance of ventricular arrhythmias in idiopathic dilated cardiomyopathy.

The incidence and prognostic significance of ventricular arrhythmias identified by 24-hour ambulatory electrocardiography (Holter) was prospectively assessed in 74 patients with idiopathic dilated cardiomyopathy (IDC). The criteria for diagnosis of IDC were based on clinical and cardiac catheterization findings. Holter monitoring was performed at the time of entry into the study. Patients were followed for 2 to 21 months (mean 11 +/- 3). Frequent ventricular premature complexes (VPCs) (greater than 1,000/24 hours) were seen in 35%, and complex VPCs (Lown grade III and IV) in 87% of the patients. Forty-nine percent of the patients had nonsustained ventricular tachycardia (VT) consisting of 3 to 32 beats with rates from 110 to 230 beats/min, and 20% had ventricular pairs. No correlation was found between clinical symptoms or the degree of left ventricular (LV) impairment and the number of ventricular pairs or episodes of VT. During follow-up, 19 patients died, 7 from congestive heart failure (CHF) and 12 suddenly. Patients who died suddenly had significantly more episodes of VT, ventricular pairs or total VPCs (p less than 0.01 each) compared with survivors and those who died from CHF. No significant differences were found between patients who died from CHF or suddenly with respect to LV end-diastolic pressure, LV end-diastolic volume index, LV ejection fraction (EF) and cardiac index. A linear stepwise discriminant function analysis using hemodynamic (LVEF and cardiac index) and arrhythmic (number of VT episodes and ventricular pairs) variables resulted in a meaningful separation between survivors and patients who died from CHF or suddenly.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the effect of isosorbide-5-mononitrate and isosorbide dinitrate in a slow-release form on exercise-induced myocardial ischemia.

A randomized, double blind, placebo-controlled crossover study on 20 patients with exercise-induced angina pectoris and reproducible ST-segment depression during exercise-stress test was performed to compare the effect of a single dose of 120 mg of isosorbide dinitrate in a slow-release form with that of a twice-daily application of 20 mg of isosorbide-5-mononitrate. Symptom-limited exercise tests were done, and nitrate plasma levels were measured in the subjects 6, 10, and 24 hours after the first administration of the drug. Both drugs produced a highly significant reduction in the size of exercise-induced ST-depressions (P less than .001) 6 and 10 hours after the first administration of isosorbide dinitrate as well as 6 hours after the first and 4 hours after the second dose of isosorbide-5-mononitrate. The effect was still significant (P less than .05) 24 hours after the administration of isosorbide dinitrate in a slow-release form and 18 hours after the second dose of isosorbide-5-mononitrate. In the case of the drug isosorbide dinitrate, nitrate plasma levels for its metabolite, isosorbide-5-mononitrate, were highest 10 hours after first application. In the case of the drug isosorbide-5-mononitrate, nitrate plasma levels were highest 4 hours after the second dose. Two 20 mg doses of isosorbide-5-mononitrate and a single dose of 120 mg isosorbide dinitrate in a slow release form have a comparable effect on the reduction of exercise-induced ST-segment depressions.

Comparison of 6-min "all-out" and incremental exercise tests in elite oarsmen.

A high aerobic capacity is an important criterion for rowing success. Two exercise protocols, the 6-min "all-out" (6M-AO) and progressive incremental (PI) tests, have been used to evaluate physiological performance in rowers and to select team members. We measured heart rate (HR), minute ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2) every 30 s, and obtained ratings of perceived exertion (RPE) from 12 candidates for the 1983 United States Men's Lightweight Rowing Team. Testing was randomized and each oarsman performed a different test on the rowing ergometer on consecutive days. For the group, age was 23 +/- 2 yr (mean +/- SD), height was 183 +/- 3 cm, and weight was 72.2 +/- 1.4 kg. Peak physiological values were achieved in the first 2 min of exercise for the 6M-AO test, but in the last 2 min for the PI test. There were no statistically significant differences among peak values for HR, VE, VO2, VCO2, and RPE with each test. The peak ventilatory equivalent for oxygen (VE/VO2) was also similar. The onset of anaerobic metabolism was observed at 83 +/- 4% of peak VO2 during the PI test, while anaerobic metabolism has been shown to occur within the first minute of the 6M-AO test. We conclude that physiological values at peak exercise were similar for the 6M-AO and PI tests. Because the onset of anaerobic metabolism can only be determined by noninvasive means using the PI test, this method of testing is preferable for the physiological assessment of rowing performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Modification of the circadian pattern of ventricular tachyarrhythmias by beta-blocker therapy.

BACKGROUND: Sudden cardiac death exhibits a circadian variation and predominantly occurs during morning hours, Beta-adrenergic antagonists have shown to blunt this morning peak. However, previous reports studying the effects of beta blockers on the circadian variation did not analyze the underlying cause of sudden cardiac death. It thus remains unclear whether ventricular tachyarrhythmias are influenced by beta-blocker therapy. HYPOTHESIS: This study tested the hypothesis that beta-blocking agents blunt the morning peak of life-threatening ventricular tachyarrhythmias. METHODS: In 87 patients who were treated and monitored with an implantable cardioverter defibrillator, the circadian distribution of ventricular tachyarrhythmias terminated by appropriate shocks was analyzed and compared in those receiving beta blockers versus those not receiving beta-blocker therapy. RESULTS: Tachyarrhythmic episodes in the absence of beta-blocker therapy (n = 344) exhibited a circadian variation with a distinct morning peak (16, 38, 28, and 18% of episodes at 0-6, 6-12, 12-18, and 18-24 h, respectively, p < 0.001). In contrast, tachyarrhythmic episodes during beta-blocker therapy (n = 104) were equally distributed over time (22, 27, 24, and 27% of episodes at 0-6, 6-12, 12-18, and 18-24 h, respectively, p = 0.95). The circadian distribution of episodes was significantly different in patients with and those without beta blockade (p < 0.05). CONCLUSION: Beta-adrenergic antagonists influence the circadian distribution of malignant ventricular tachyarrhythmias in patients with an implantable cardioverter defibrillator. The blunted morning peak of tachyarrhythmic events during beta blockade supports the hypothesis that a sympathetic surge is involved in the circadian pattern of malignant arrhythmias.