1,721,359 research outputs found
Rate-control drugs affect variability and irregularity measures of rr intervals in patients with permanent atrial fibrillation
Full text linkHeart Rate Variability and Irregularity During AF IntroductionIrregularity measures have been suggested as risk indicators in patients with atrial fibrillation (AF); however, it is not known to what extent they are affected by commonly used rate-control drugs. We aimed at evaluating the effect of metoprolol, carvedilol, diltiazem, and verapamil on the variability and irregularity of the ventricular response in patients with permanent AF. Methods and ResultsSixty patients with permanent AF were part of an investigator-blind cross-over study, comparing 4 rate-control drugs (diltiazem, verapamil, metoprolol, and carvedilol). We analyzed five 20-minute segments per patient: baseline and the 4 drug regimens. On every segment, heart rate (HR) variability and irregularity of RR series were computed. The variability was assessed as standard deviation, pNN20, pNN50, pNN80, and rMSSD. The irregularity was assessed by regularity index, approximate (ApEn), and sample entropy. A significantly lower HR was obtained with all drugs, the HR was lowest using the calcium channel blockers. All drugs increased the variability of ventricular response in respect to baseline (as an example, rMSSD: baseline 171 47 milliseconds, carvedilol 229 +/- 58 milliseconds; P < 0.05 vs. baseline, metoprolol 226 +/- 66 milliseconds; P < 0.05 vs. baseline, verapamil 228 +/- 84; P < 0.05 vs. baseline, diltiazem 256 +/- 87 milliseconds; P < 0.05 vs. baseline and all other drugs). Only -blockers significantly increased the irregularity of the RR series (as an example, ApEn: baseline 1.86 +/- 0.13, carvedilol 1.92 +/- 0.09; P < 0.05 vs. baseline, metoprolol 1.93 +/- 0.08; P < 0.05 vs. baseline, verapamil 1.86 +/- 0.22 ns, diltiazem 1.88 +/- 0.16 ns). ConclusionModification of AV node conduction by rate-control drugs increase RR variability, while only -blockers affect irregularity
Clinical Use And Limitations Of Non-Invasive Electrophysiological Tests In Patients With Atrial Fibrillation
No full textAtrial fibrillation (AF) is a complex arrhythmia, that has been studied non-invasively assessing atrial refractory period, atrioventricular node (AV) node refractory period, and ventricular response. The AV node plays a fundamental role as it filters many of the numerous irregular atrial impulses bombarding the node. Despite its importance, the electrophysiological (EP) characteristics of the AV node are not routinely evaluated since conventional EP techniques for assessment of refractory period or conduction velocity of the AV node are not applicable in AF. Since rate-control drugs control ventricular response through their effect on the AV node, noninvasive assessment of AV node electrophysiology may be useful. The RR series, though being highly irregular, contains information that can be used for risk stratification and prediction of outcome. In particular, RR irregularity measures during AF have been shown to be related to clinical outcome. This paper reviews the attempts done to noninvasively characterize the AV node and the ventricular response, highlighting clinical applications and limitations of the noninvasive techniques
Atrial fibrillatory rate in the clinical context: natural course and prediction of intervention outcome
Full text linkShortening of atrial refractory period during atrial fibrillation has been considered a hallmark of atrial electrical remodelling. The atrial fibrillatory cycle length, which is intimately related to the atrial fibrillatory rate (AFR), is generally accepted as a surrogate marker for local refractoriness. The value of using AFR to monitor the progress of atrial ablation therapy has been demonstrated and gradual slowing of AFR has consistently been observed to precede arrhythmia termination during paroxysmal or permanent atrial fibrillation ablation. Today, AFR is the key characteristic of the fibrillatory process, repeatedly validated against intracardiac recordings and extensively studied in clinical contexts. This paper provides an overview of clinical data accumulated since the method was introduced in 1998, and to present the current state of knowledge regarding ECG-derived AFR: its time course and dynamics, clinical factors affecting AFR, and available evidence of its value in the clinical context. We conclude that AFR is a promising, easily available AF characteristic that can be derived from the conventional surface ECG. It is clearly a useful tool for monitoring drug effects. Reference values for predicting intervention effect, however, are likely to be population- and context-specific and related to age, clinical types of atrial fibrillation, as well as to presence and advancement of underlying structural heart disease. Prospective studies in homogeneous patient populations are still needed to establish the clinical value of AFR
Autonomic influence on atrial fibrillatory process: Head-up and head-down tilting
Full text linkBackground: Changes in the autonomic nervous system (ANS) tone are present before, during, and after episodes of atrial fibrillation (AF). Atrial fibrillatory rate (AFR, the inverse of the atrial cycle length) has been used as a surrogate marker for local refractoriness and is a key characteristic of the fibrillatory process in patients with AF. Aim of this study is to assess changes in AFR, as an effect of autonomic balance change. Methods: Forty patients undergoing cardiac cardioversion for symptomatic persistent AF were included in the study. Surface ECG was recorded during rest, head-down (HDT, -30°), and head-up tilt (HUT, +60°). A median value of AFR was computed in each phase of the protocol. Results: AFR decreased during HDT compared to the baseline (B) condition in all patients but three (median AFR_B = 391 fpm vs. AFR_HDT = 377 fpm, p < .0001). HUT increased AFR, making it significantly higher than HDT and baseline conditions (median AFR_HUT = 396 fpm, p < .0001 vs. B and HDT). Heart rate (HR) increased during HUT, but had a heterogeneous behavior in the population during HDT: about one third of the patients had an HR lower during HDT than during baseline, whereas the remaining two third had an increase in HR during HDT. Conclusions: Dominant sympathetic/vagal tone during HUT/HDT significantly affects AFR, increasing/decreasing in respect to baseline. It may be worth exploring the possibility that patients with AF of shorter duration can convert to sinus rhythm during HDT
Non-invasive assessment of the effect of beta blockers and calcium channel blockers on the AV node during permanent atrial fibrillation
No full textWe aimed at assessing changes in AV nodal properties during administration of the beta blockers metoprolol and carvedilol, and the calcium channel blockers diltiazem and verapamil from electrocardiographic data
High interobserver variability in the assessment of epsilon waves: Implications for diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia
Full text linkRevision of the Task Force diagnostic criteria (TFC) for arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) has increased their sensitivity for diagnosis of early and familial forms of the disease. Epsilon wave (EW) is a major diagnostic criterion in the context of ARVC/D, which, however, remains not quantifiable and therefore may leave room for substantial subjective interpretation
Prediction of mortality benefit based on periodic repolarisation dynamics in patients undergoing prophylactic implantation of a defibrillator: a prospective, controlled, multicentre cohort study
No full textThe Role of Impaired Interatrial Conduction in Paroxysmal Atrial Fibrillation
No full textThe aim of this thesis was to evaluate the role of interatrial conduction defects in the genesis of lone paroxysmal atrial fibrillation (AF) using combined approach of non-invasive signal-averaged P-wave ECG, invasive electrophysiological (EP) studies, anatomical studies and animal experiments. Non-filtered signal-averaged P-wave ECG revealed irregularities in orthogonal P-wave morphology and the presence of double-peaked configurations of P-wave spatial magnitude in patients with lone paroxysmal AF compared with healthy individuals (I), suggesting the presence of interatrial conduction delays localised in the posterior-inferior interatrial route. The interpretation of human P-wave ECG was supported by the experimental study (V), in which similar configurations of P-wave spatial magnitudes were reproduced by the interruption of conduction over the posterior interatrial route in pigs. In a series of endocardial EP studies (II), predominant conduction disturbances within the right atrium causing localised inferior-posterior interatrial conduction delays were found in a group of patients with lone paroxysmal AF during sinus rhythm and atrial stimulation. In AF patients, induction of the arrhythmia paroxysms was associated with conduction disturbances in the posterior septal region (III), suggesting that the initial re-entry occurs there. In the pathology study (IV), we showed that in addition to the anteriorly located Bachmann's bundle, numbers of muscle bundles connect the right and the left atria across the posterior interatrial groove. These posterior interatrial routes are non-uniform structures subjected to substantial variability, which may be an anatomical prerequisite for interatrial conduction defects and explain why some patients are more prone to developing interatrial conduction blocks and atrial fibrillation than others
Interatrial conduction in the mechanisms of atrial fibrillation: from anatomy to cardiac signals and new treatment modalities.
No full textAreas of slow conduction and conduction block are important prerequisites for re-entry known to underlie atrial fibrillation (AF). Experimental and clinical data show that AF is associated with global lowering of atrial propagation velocity and the presence of defects in the interatrial conduction routes. The increasing data from anatomical studies demonstrate the possible prerequisites for conduction disturbances that could be primarily because of anatomical variability in interatrial connections or because of age-related development of fibrotic changes in the atrial musculature. More detailed descriptions of the structure and function of the interatrial connections other than Bachmann's bundle have become available and, as a result, the role of these connections in the mechanisms of AF is increasingly appreciated. Interatrial pacing studies show promising results, but further studies on larger amounts of materials are required in order to identify the population of patients who would benefit more effectively from this treatment as well as the optimal pacing technique. Therefore, more extensive documentation is required before therapeutic modalities aimed at improving interatrial conduction will become a part of the clinical routine in the management of AF patients
P-wave morphology: underlying mechanisms and clinical implications.
No full textIncreasing awareness of atrial fibrillation (AF) and its impact on public health revives interest in identification of noninvasive markers of predisposition to AF and ECG-based risk stratification. P-wave duration is generally accepted as the most reliable noninvasive marker of atrial conduction, and its prolongation has been associated with history of AF. However, patients with paroxysmal AF without structural heart disease may not have any impressive P-wave prolongation, thus suggesting that global conduction slowing is not an obligatory requirement for development of AF. P-wave morphology is therefore drawing increasing attention as it reflects the three-dimensional course of atrial depolarization propagation and detects local conduction disturbances. The factors that determine P-wave appearance include (1) the origin of the sinus rhythm that defines right atrial depolarization vector, (2) localization of left atrial breakthrough that defines left atrial depolarization vector, and (3) the shape and size of atrial chambers. However, it is often difficult to distinguish whether P-wave abnormalities are caused by atrial enlargement or interatrial conduction delay. Recent advances in endocardial mapping technologies have linked certain P-wave morphologies with interatrial conduction patterns and the function of major interatrial conduction routes. The value of P-wave morphology extends beyond cardiac arrhythmias associated with atrial conduction delay and can be used for prediction of clinical outcome of a wide range of cardiovascular disorders, including ischemic heart disease and congestive heart failure
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