T-wave amplitude variability and the risk of death in Chagas disease.

INTRODUCTION: Measurement of beat-to-beat T-wave amplitude variability (TWV) has been described as a promising new technique for the stratification of arrhythmic risk in postmyocardial infarction and dilated cardiomyopathy patients. Chagas disease (ChD) can lead to a potentially lethal cardiopathy that can present with ventricular arrhythmias, heart blocks, heart failure, and sudden death. The aim of the study was to evaluate the prognostic value of TWV in ChD patients in addition to traditional prognostic predictors. METHODS AND RESULTS: The study enrolled 113 ambulatory ChD patients (62 men; age: 42 ± 9 years) in sinus rhythm and without other systemic diseases, evaluated by a standard clinical protocol. We computed TWV in 10-minute ECG recordings obtained in controlled resting conditions. TWV was defined as the median values among 8 consecutive 50-ms T-wave segments and dichotomized as either ≤ or > 30 µV(2). The association of TWV and death was evaluated by Cox proportional-hazards analysis, considering other established predictors. During mean follow-up time of 106 ± 28 months, 14 patients died. A value of median TWV > 30 µV(2) predicts increased risk of death in a multivariate analysis (HR = 5.76, 95% CI 1.31-25.23, P = 0.014), in addition to depressed left ventricular function, presence of nonsustained ventricular tachycardia and QRS duration >133 ms. CONCLUSION: Repolarization variability, evaluated by TWV, is independently related to the risk of death in ChD. This noninvasive methodology could facilitate the identification of patients who may benefit from more aggressive therapeutic strategies.

Prognostic implications of stress-induced transient ischemic dilation of the left ventricle in patients with systolic dysfunction and fixed perfusion defects.

PURPOSE: To verify whether stress-induced transient ischemic dilation (TID) of the left ventricle may help refine prognostic assessment of patients with resting systolic dysfunction and fixed perfusion defects. METHODS: Two hundred seventy patients with resting ejection fraction

Low frequency component in systolic arterial pressure variability in patients with persistent atrial fibrillation.

Atrial fibrillation (AF) is a common arrhythmia characterized by irregular ventricular response. During AF, beat-to-beat variability of arterial pressure (AP) is increased because of continuous changes in filling time, stroke volume and contractility. Only a few studies have analyzed short-term AP variability during AF but they were mainly focused on the effects of respiration. We therefore analyzed short-term systolic (S), diastolic (D) and mean (M) AP variability by autoregressive method and an FFT-based spectral estimation (Welch periodogram) in 26 patients with persistent AF before and after restoration of sinus rhythm by electrical cardioversion. A low frequency (LF) component (central frequency 0.07+/-0.02 Hz, mean+/-standard deviation) of SAP variability was observed in 23 out of 26 patients during AF. Frequency analysis of DAP and MAP also showed a LF component with a central frequency of 0.08+/-0.03 Hz (20 patients) and 0.07+/-0.03 Hz (25 patients), respectively. After recovery of sinus rhythm, we found significant reduction in mean SAP, DAP and MAP variability in all frequency bands. Squared coherence between SAP and heart rate variability after recovery of sinus rhythm revealed a weak and strong coupling within, respectively, LF and HF frequency bands. These data indicate that in patients with AF, in spite of an absence of rhythmical oscillation in RR interval time series, it is possible to observe a LF component in SAP, DAP and MAP variability signals. These 0.1 Hz fluctuations reflect the influence of the sympathetic fibres acting on the cardiovascular system.

Anti-arrhythmic properties of N-3 poly-unsaturated fatty acids (n-3 PUFA).

Omega-3 fatty acids (Poly-Unsaturated Fatty Acids or PUFA n-3) have been initially found to reduce plasma levels of triglycerides and to increase levels of high-density lipoprotein in patients with marked hypertriglyceridemia. However, in both bench research studies and clinical trials, omega-3 fatty acid intake has recently been associated with an anti-arrhythmic efficacy. At experimental level, n-3 PUFA administration produces several actions on ionic channels regulating transmembrane action potential. At clinical level, the most significant finding was the reduction in the incidence of sudden death in survivors of MI in the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI)-Prevention trial and the subsequent recommendation for administration of fish oil as part of the post-infarction regimen in European guidelines. More recently, Omega-3 fatty acids administration has been associated with a lower incidence of atrial fibrillation in patients who underwent cardiac surgery. Contrasting results have been instead reported in patients with implantable cardioverter defibrillators. This article reviews in detail the basic and clinical research studies of fish oil as an anti-arrhythmic entity, the types of arrhythmias that have been beneficially affected by fish oil administration, and the presumed and known mechanisms by which the beneficial actions are exerted.

Atrial Fibrillation and Revascularization Procedures: Clinical and Prognostic Significance. Incidence, Predictors, Treatment, and Long-Term Outcome.

[This retracts the article on p. 50 in vol. 7.].

Early outcomes of out-of-hospital cardiac arrest after early defibrillation: a 24 months retrospective analysis.

INTRODUCTION: Cardiovascular disease remains the most common cause of death in the United States and most other Western nations. Among these deaths, sudden, out-of-hospital cardiac arrest claims approximately 1000 lives each day in the United States alone. Most of these cardiac arrests are due to ventricular fibrillation. Though highly reversible with the rapid application of a defibrillator, ventricular fibrillation is otherwise fatal within minutes, even when cardiopulmonary resuscitation is provided immediately. The overall survival rate in the United States is estimated to be less than 5 percent. Recent developments in automated-external-defibrillator technology have provided a means of increasing the rate of prompt defibrillation after out-of-hospital cardiac arrest. After minimal training, nonmedical personnel (e.g., flight attendants and casino workers) are also able to use defibrillators in the workplace, with lifesaving effects. Nonetheless, such programs have involved designated personnel whose job description includes assisting persons who have had sudden cardiac arrest. Data are still lacking on the success of programs in which automated external defibrillators have been installed in public places to be used by persons who have no specific training or duty to act. MATERIALS AND METHODS: All patients who had an out-of-hospital cardiac arrest between January 2003 and December 2004 and who received early defibrillation for ventricular fibrillation were included. We conducted a 24 months retrospective population-based analysis of the outcome in our population. RESULTS: Over a 24 month period, 446 people had non-traumatic cardiac arrest, and in all of them it was observed to be ventricular fibrillation. In a very few cases, the defibrillator operators were good Samaritans, acting voluntarily. Eighty-nine patients (about 19%) with ventricular fibrillation were successfully resuscitated, including eighteen who regained consciousness before hospital admission. CONCLUSION: Automated external defibrillators deployed in readily accessible, well-marked areas, are really very effective in assisting patients with cardiac arrest. However, it's quite true that, in the cases of survivors, most of our users had good prior training in the use of these devices.

Pacemaker prevention therapy in drug-refractory paroxysmal atrial fibrillation: reliability of diagnostics and effectiveness of prevention pacing therapy in Vitatron selection device.

INTRODUCTION: Atrial fibrillation (AF), the most common and rising disorder of cardiac rhythm, is quite difficult to control and/or to treat. Non pharmacological therapies for AF may involve the use of dedicated pacing algorithms to detect and prevent atrial arrhythmia that could be a trigger for AF onset. Selection 900E/AF2.0 Vitatron DDDRP pacemaker (1) keeps an atrial arrhythmia diary thus providing detailed onset reports of arrhythmias of interest, (2) provides us data about the number of premature atrial contractions (PACs) and (3) plots heart rate in the 5 minutes preceding the detection of an atrial arrhythmia. Moreover, this device applies four dedicated pacing therapies to reduce the incidence of atrial arrhythmia and AF events. AIM OF THE STUDY: To analyze the reliability to record atrial arrhythmias and evaluate effectiveness of its AF preventive pacing therapies. MATERIAL AND METHODS: We enrolled 15 patients (9 males and 6 females, mean age of 71+/-5 years, NYHA class I-II), with a DDDRP pacemaker implanted for a "bradycardia-tachycardia" syndrome, with advanced atrioventricular conduction disturbances. We compared the number and duration of AF episodes' stored in the device with a contemporaneous 24h Holter monitoring. After that, we switched on the atrial arrhythmias detecting algorithms, starting from an atrial rate over 180 beats per minute for at least 6 ventricular cycles, and ending with at least 10 ventricular cycles in sinus rhythm. Thereafter, in order to evaluate the possible reduction in PACs number and in number and duration of AF episodes, we tailored all the four pacing preventive algorithms. Patients were followed for 24+/-8 months (from 20 to 32 months). RESULTS: All 59 atrial arrhythmia episodes occurred in the first part of this trial, were correctly recorded by both systems, with a correlation coefficient (r) of 0.96. During the follow-up, we observed a significant reduction not only in PACs number (from 83+/-12/day to 2.3+/-0.8/day) but also in AF episodes (from 46+/-7/day to 0.12+/-0.03/day) and AF burden (from 93%+/-6% to 0.3%+/-0.06%). An increase in atrial pacing percentages (from 3%+/-0.5% to 97%+/-3%) was also contemporaneously observed. CONCLUSION: In this pacemaker, detection of atrial arrhythmia episodes is highly reliable, thus making available an appropriate monitoring of heart rhythm, mainly suitable in AF asymptomatic patients. Moreover, the significant reduction of atrial arrhythmia episodes indicates that this might represent a suitable therapeutic option for an effective preventive therapy of AF in paced brady-tachy patients.

Atrial fibrillation and pacing algorithms.

Pacing prevention algorithms have been introduced in order to maximize the benefits of atrial pacing in atrial fibrillation prevention. It has been demonstrated that algorithms actually keep overdrive atrial pacing, reduce atrial premature contractions, and prevent short-long atrial cycle phenomenon, with good patient tolerance. However, clinical studies showed inconsistent benefits on clinical endpoints such as atrial fibrillation burden. Factors which may be responsible for neutral results include an already high atrial pacing percentage in conventional DDDR, non-optimal atrial pacing site and deleterious effects of high percentages of apical ventricular pacing. Atrial antitachycardia pacing (ATP) therapies are effective in treating spontaneous atrial tachyarrhythmias, mainly when delivered early after arrhythmia onset and/or on slower tachycardias. Effective ATP therapies may reduce atrial fibrillation burden, but conflicting evidence does exist as regards this issue, probably because current clinical studies may be underpowered to detect such an efficacy. Wide application of atrial ATP may reduce the need for hospitalizations and electrical cardioversions and favorably impact on quality of life. Consistent monitoring of atrial and ventricular rhythm as well as that of ATP effectiveness may be extremely useful for optimizing device programming and pharmacological therapy.

Pharmacological treatment of atrial fibrillation: mechanisms of action and efficacy of class III drugs.

Atrial fibrillation represents a major clinical, social and economical matter, and its importance is expected to increase even more in the near future. The progressive ageing of population is associated with an inevitable rising in incidence and prevalence of this rhythm disorder, which limits functional capability, favours occurrence of cerebrovascular events and increases people's request for emergency room visits and hospital recovery. In spite of the increasing successes of the interventional non-pharmacological therapies, drug treatment of patients with atrial fibrillation in relation to conversion to sinus rhythm and prevention of recurrences, maintains a critical role. Several antiarrhythmic drugs are nowadays available, but their efficacy is limited by the high rate of arrhythmias recurrences and by side effects during acute and chronic treatment. Drugs interfering with potassium channels (Class III drugs) have been proposed and used in patients with atrial fibrillation. Aim of this review is to discuss the most recent data on the efficacy and feasibility of class III drugs in atrial fibrillation. Experimental and clinical data on dronedarone, ibutilide, dofetilide, azimilide, ersentilide and ambasilide will be hereby discussed.

Renin-angiotensin system block and atrial fibrillation.

Atrial fibrillation is the most common disorder of cardiac rhythm. In spite of diagnosis simplicity, patients with atrial fibrillation are difficult to treat. In the recent years with the description of the phenomenon called remodelling, it has been possible to better define the principle mechanisms responsible for initiation, maintenance and, in some instances, termination of atrial fibrillation. Electrical, mechanical and anatomical remodelling indicate those alterations that, once established, may vanish any attempt to restore sinus rhythm. Atrial fibrosis is probably the most critical component of the remodelling process and appears to be largely mediated by the activation of the Renin-Angiotensin-Aldosterone System. Both experimental and clinical data have confirmed the pro-arrhythmic role of the Renin-Angiotensin-Aldosterone System and demonstrated an anti-arrhythmic effects of ACE-inhibitors and AT(1) receptor blockers. Regarding atrial fibrillation, it has been recently reported that the adjunction of AT(1) receptor blocker to amiodarone was more effective than the anti-arrhythmic drug alone, in reducing arrhythmia recurrence after electrical cardioversion. This and subsequent clinical observations indicate that pharmacological interventions capable of interfering with the electrical and structural remodelling process are of critical importance in the management of patients with atrial fibrillation. ACE inhibitors and AT(1) receptor blockers represent new and efficient therapeutical options to contrast the nearly inevitable progression of this arrhythmia towards its permanent form.

Prognostic value of C-reactive protein in patients with stress induced myocardial ischemia.

OBJECTIVE: Inflammation plays a critical role in the pathogenesis of atherosclerosis. Possible association between C-reactive protein (CRP), stress-induced myocardial ischemia and clinical outcome was investigated. DESIGN, PATIENTS AND RESULTS: We correlated scintigraphic scan and CRP values of 101 consecutive out-patients who performed an exercise stress test for evaluation of chest pain (n=49) or scheduled control after myocardial infarction (n=52). CRP levels were determined before and after exercise. Twenty-three patients had reversible defects and presented CRP levels [mean (S.D.) 5.6 (3.3) mg/l] greater than subjects with fixed [mean (S.D.) 4.6 (4.5) mg/l] or no [mean (S.D.) 2.8 (2.9) mg/l] defects. Odds ratio for the association between high (3rd, tertile, >4.7 mg/l) CRP levels and reversible defects was 5.6 (95% CI 1.6 to 20; p=0.009). During a follow-up of 2.3 (0.7) years, 18 patients reached a clinical end-point consisting in one Q-wave myocardial infarction, eight non-Q-wave myocardial infarction or unstable angina and nine percutaneous coronary interventions. When the impact of different risk factors on the development of clinical endpoint was evaluated, the hazard ratio associated with high CRP levels was 11.0 (95% CI 3.0 to 41; p<0.001). CONCLUSIONS: These findings suggest that in ambulatory patients, high CRP levels may predict exercise-induced ischemia and patient outcome.

Hypertension and concurrent arrhythmias.

Hypertension and cardiac arrhythmias commonly coexist in many patients. In this review, we will initially discuss arrhythmogenesis in hypertension, with particular emphasis on atrial and ventricular tachyarrhythmias and sudden cardiac death, whilst in the final part, we will focus our attention on the effects of anti-hypertensive therapies on supra-ventricular and ventricular arrhythmias and on sudden cardiac death prevention. Many patients with atrial fibrillation or frequent premature ventricular contractions have hypertension, and both need to be managed appropriately. Furthermore, hypertensive left ventricular hypertrophy could cause a wide variety of ventricular arrhythmias, which could end in sudden cardiac arrest. Most anti-hypertensive therapies, such as the beta blockers or ACE inhibitors, by slowing or interrupting the progression towards atrial and ventricular remodelling might exert some anti-arrhythmic effect, thus reducing the risk of sudden cardiac death in these patients.