2011 ACCF/AHA/HRS Focused Update on the Management of Patients With Atrial Fibrillation (Updating the 2006 Guideline)

Atrial fibrillation

Atrial fibrillation is the most common arrhythmia affecting patients today. Disease prevalence is increasing at an alarming rate worldwide, and is associated with often catastrophic and costly consequences, including heart failure, syncope, dementia, and stroke. Therapies including anticoagulants, anti-arrhythmic medications, devices, and non-pharmacologic procedures in the last 30 years have improved patients' functionality with the disease. Nonetheless, it remains imperative that further research into AF epidemiology, genetics, detection, and treatments continues to push forward rapidly as the worldwide population ages dramatically over the next 20 years.

In silico investigation of a KCNQ1 mutation associated with familial atrial fibrillation

Mutations in transmembrane domains of the KCNQ1 subunit of the I(Ks) potassium channel have been associated with familial atrial fibrillation. We have investigated mechanisms by which the S1 domain S140G KCNQ1 mutation influences atrial arrhythmia risk and, additionally, whether it can affect ventricular electrophysiology. In perforated-patch recordings, S140G-KCNQ1+KCNE1 exhibited leftward-shifted activation, slowed deactivation and marked residual current. In human atrial action potential (AP) simulations, AP duration and refractoriness were shortened and rate-dependence flattened. Simulated I(Ks) but not I(Kr) block offset AP shortening produced by the mutation. In atrial tissue simulations, temporal vulnerability to re-entry was little affected by the S140G mutation. Spatial vulnerability was markedly increased, leading to more stable and stationary spiral wave re-entry in 2D stimulations, which was offset by I(Ks) block, and to scroll waves in 3D simulations. These changes account for vulnerability to AF with this mutation. Ventricular AP clamp experiments indicate a propensity for increased ventricular I(Ks) with the S140G KCNQ1 mutation and ventricular AP simulations showed model-dependent ventricular AP abbreviation.

Adherence to guideline recommendations for antiarrhythmic drugs in atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) guideline recommendations for antiarrhythmic drugs (AADs) are based on the effectiveness and safety of the AAD in patients with selected, concomitant heart disease. It is unknown to what extent these recommendations are being implemented in clinical practice.

METHODS

Using commercial health claims, patients with AF were identified and then categorized into mutually exclusive, guideline-established subgroups based on their most serious concurrent heart disease: heart failure, coronary artery disease (CAD), hypertension, and no heart disease. Antiarrhythmic drug use after the first AF encounter and the identified concurrent heart disease encounter was determined from prescription claims, and this was compared with guideline recommendations.

RESULTS

From January 2006 through December 2010, a total of 331,274 patients with AF aged < 65 years were identified: 18%, heart failure; 23%, CAD; 33%, hypertension; and 25%, no heart disease. Of these, 78,877 (24%) patients filled ≥ 1 qualifying AAD prescription. The median age was 57 years (interquartile range 52-61), and 69% were male. A total of 74,191 patients had AADs after both the AF and concurrent heart disease encounters: 27% with heart failure, 25% with CAD, 21% with hypertension, and 19% with no heart disease. In the heart failure and CAD subgroups, 45% and 31% of AADs were inconsistent with first- or second-line guideline recommendations, respectively.

CONCLUSION

More than one-third of the AADs used in patients with AF and CAD or heart failure did not conform to guideline recommendations. This highlights the potential need for increased clinician education and intervention to improve the safe use of AADs for AF management.

Exploiting intracardiac and surface recording modalities for atrial signal extraction in atrial fibrillation

During atrial fibrillation (AF), atrial activity (AA) on the surface ECG consists of a pattern of quasi-periodic oscillations (f-waves), which are related to the electrical activation of the atrial substrate. However, to date no direct comparison between the extracted f-wave pattern in surface recordings and specific activation sites within the atria has been carried out. In the present study, one reference intracardiac modality consisting of a bipolar electrogram (EGM) recorded from the left atrial appendage (LAA) is exploited for the first time to guide the extraction of LAA electrical activity from standard 12-lead ECG recordings. A periodic component analysis (πCA) technique is employed for this task. The performance of the proposed multimodal extraction technique is compared to that obtained employing a noninvasive, fully blind approach, namely, independent component analysis (ICA). On a database of 31 AF patients, results suggest that the estimation of LAA activity is indeed possible, even though its contribution to the ECG total power is relatively low. Interestingly, ICA seems to provide a slightly better estimation of LAA activation rate, expressed in terms of dominant frequency (DF). On the other hand, the multimodal invasive approach performs better QRST complex suppression and provides AA waveforms with narrower spectra.