Background— Twelve lead ECGs have limited value in precisely identifying atrial and ventricular activation during arrhythmias, including accessory atrioventricular conduction activation. The aim of this study was to report a single center’s clinical experience validating a novel, noninvasive, whole heart, beat-by-beat, 3-dimensional mapping technology with invasive electrophysiological studies, including ablation, where applicable. Methods and Results— Using an electrocardiographic mapping (ECM) system in 27 patients, 3-dimensional epicardial activation maps were generated from >250 body surface ECGs using heart–torso geometry obtained from computed tomographic images. ECM activation maps were compared with clinical diagnoses, and confirmed with standard invasive electrophysiological studies mapping. (1) In 6 cases of Wolff–Parkinson–White syndrome, ECM accurately identified the ventricular insertion site of an accessory atrioventricular connection. (2) In 10 patients with premature ventricular complexes, ECM accurately identified their ventricular site of origin in 8 patients. In 2 of 10 patients transient premature ventricular complex suppression was observed during ablation at the site predicted by ECM as the earliest. (3) In 10 cases of atrial tachycardia/atrial flutter, ECM accurately identified the chamber of origin in all 10, and distinguished isthmus from nonisthmus dependent atrial flutter. (4) In 1 patient with sustained exercise induced ventricular tachycardia, ECM accurately identified the focal origin in the left ventricular outflow tract. Conclusions— ECM successfully provided valid activation sequence maps obtained noninvasively in a variety of rhythm disorders that correlated well with invasive electrophysiological studies.
Atrial fibrillation (AF) is the most common clinically encountered arrhythmia affecting 0.4% of the general population. Its prevalence increases with age, affecting more than 6% of people over 80 years of age. The annual risk of ischemic stroke in patients with lone AF is approximately 1.3%. This annual risk increases up to 10% -12% in patients with a prior stroke or transient ischemic attack. Randomized clinical trials (RCT) comparing adjusted-dose oral anticoagulation and placebo showed a risk reduction of 61% (95% CI 47% to 71%). The absolute risk reduction for stroke with oral anticoagulants is about 3% per year. Aspirin has been shown in meta-analyses to have on average a 20-25% relative risk reduction, and is inferior to oral anticoagulants. In high risk patients with AF warfarin is a class I ACC/AHA indication unless there is a contraindication for anticoagulation. Unfortunately, this therapy requires frequent monitoring with blood samples and the interaction with food and several medications makes its use difficult and sometimes unreliable. It requires strict patient compliance and its use is also linked to potentially serious bleeding complications. In clinical practice, less than 60% of patients who do not have contraindications to oral anticoagulation are actually receiving them. Additionally, of those that receive oral anticoagulation, less than 50% are consistently within therapeutic targets. As such, the "real world" efficacy of a strategy towards prescribing oral anticoagulants is likely significantly lower than that demonstrated in clinical trials. As such, the need to discover other methods of anticoagulation with oral bioavailability, predictable pharmacokinetics, and minimal interactions with diet and other pharmacological agents is imperative. Low molecular weight heparin has a more predictable bioavailability and a longer half-life, but its subcutaneous mode of administration and long-term risks, in particular, osteoporosis makes the chronic use of this medication non-feasible. Antiplatelet agents such as clopidogrel have proven efficacy and superiority compared to aspirin to prevent systemic vascular events in at-risk patient populations, but currently they do not play an important role in the prevention of AF related thromboembolic events. The ACTIVE study is a randomized trial comparing the combination of clopidogrel and aspirin therapy to oral anticoagulation with warfarin in patients with AF, and was unfortunately terminated prematurely by the data safety and monitoring board because of increased events in the antiplatelet arm. Direct thrombin inhibitors, such as ximelagatran, may be as effective as warfarin for stroke-risk reduction in patients with AF. No anticoagulation monitoring is needed and it has excellent bioavailability, with a twice-daily oral dose. Elevation of liver enzymes was an initial concern regarding the use of this new drug, which is not available for general use. Ongoing pharmacological research and future clinical trials may one day leave the "warfarin days" behind....
Given the increasing prevalence of atrial fibrillation, the need for safe and effective stroke prophylaxis will continue to rise. Warfarin has been around for many years and has proven efficacy in preventing stroke, but it has major limitations due to its variable dosing, food and drug interactions, and requirement for regular monitoring. Newer agents which include dabigatran, rivaroxaban, and apixaban have recently or will soon be available and may provide an improved efficacy in stroke prevention, an improved safety profile, and improved user-friendliness. Dabigatran was the first of the agents to be widely available, and in the RE-LY study, dabigatran (150 mg dose) showed superiority to warfarin in preventing ischemic stroke and a significant reduction in intracranial bleeding. Rivaroxaban was studied in the ROCKETAF trial, and with once daily dosing, it showed noninferiority to warfarin in preventing stroke with a significant reduction in intracranial bleeding. The ARISTOTLE trial showed apixaban was superior to warfarin for stroke prevention, significantly reduced all major bleeding, and resulted in a significant reduction in all-cause mortality. While all three trials have important limitations, they were very large randomized trials with more than 14,000 patients each and show a clear overall net clinical benefit when compared with warfarin. Key features of the drugs as well as an individual's preferences and stability on warfarin will help guide the ultimate drug choice for any given patient, but these newer anticoagulant agents are likely to usher in a new era in stroke prevention in atrial fibrillation.
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