Coronary computed tomography angiography (CTA) is an increasingly utilized, highly accurate noninvasive test for the diagnosis of coronary artery disease. Accumulating data have convincingly demonstrated that the presence, extent, and location of both obstructive and nonobstructive coronary atherosclerosis visualized on coronary CTA conveys powerful prognostic information, incremental to that provided by clinical variables and coronary calcium scoring. Proposed markers of future plaque instability and coronary risk, such as the degree of vessel remodeling and low-attenuation plaque volume, as well as measures of CT myocardial perfusion, may further improve the prognostic value of CTA. Ultimately, studies are needed to assess whether the prognostic information provided by coronary CTA testing results in sustained changes in patient and provider behaviors that cost effectively improve patient outcomes.
Electrical alternans is an electrocardiographic phenomenon defined as an alternating amplitude or axis of the QRS complexes in any or all leads. It is most commonly associated with a large pericardial effusion and impending threat of cardiac tamponade; however, a literature review showed that this electrocardiographic finding can be seen in a variety of other clinical scenarios with varying etiologies and prognoses. Several electrocardiogram examples are presented with a brief review of the potential mechanisms and clinical significance and demonstrate that electrical alternans is more correctly considered an electrocardiographic sign, rather than a diagnosis, with a broad differential for potential etiologies. For some causes, the clinical significance is well known, but for others, further research is needed.
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