Abstract-Atrial fibrillation is associated with increased expression of ventricular myosin isoforms in atrial myocardium, regarded as part of a dedifferentiation process. Whether reexpression of ventricular isoforms in atrial fibrillation is restricted to transcripts encoding for contractile proteins is unknown. Therefore, this study compares atrial mRNA expression in patients with permanent atrial fibrillation to atrial mRNA expression in patients with sinus rhythm and to ventricular gene expression using Affymetrix U133 arrays. In atrial myocardium, we identified 1434 genes deregulated in atrial fibrillation, the majority of which, including key elements of calcium-dependent signaling pathways, displayed downregulation. Functional classification based on Gene Ontology provided the specific gene sets of the interdependent processes of structural, contractile, and electrophysiological remodeling. In addition, we demonstrate for the first time a prominent upregulation of transcripts involved in metabolic activities, suggesting an adaptive response to increased metabolic demand in fibrillating atrial myocardium. Ventricular-predominant genes were 5 times more likely to be upregulated in atrial fibrillation (174 genes upregulated, 35 genes downregulated), whereas atrial-specific transcripts were predominantly downregulated (56 genes upregulated, 564 genes downregulated). Overall, in fibrillating atrial myocardium, functional classes of genes characteristic of ventricular myocardium were found to be upregulated (eg, metabolic processes), whereas functional classes predominantly expressed in atrial myocardium were downregulated (eg, signal transduction and cell communication). Therefore, dedifferentiation with adoption of a ventricular-like signature is a general feature of the fibrillating atrium. Key Words: atrial fibrillation Ⅲ gene expression Ⅲ atrial myocardium Ⅲ functional genomics A trial fibrillation (AF), the most common sustained arrhythmia, is associated with extensive structural, contractile, and electrophysiological remodeling, 1 stabilizing AF in the long run. Because current pharmacological treatment of AF is limited by ventricular proarrhythmia and inefficacy to prevent recurrences of AF, understanding the molecular events of these remodeling processes is essential for the development of new targeted therapeutic interventions. Even though knowledge of genes involved in remodeling processes exists on a gene-by-gene basis including transcripts of the extracellular matrix compartment, 2 ion channels, 1,3 and signal transduction molecules, 4 microarray analysis offers a broader and unbiased approach to identify pathophysiologically relevant pathways. Therefore, we performed a systematic functional analysis of gene expression in permanent atrial fibrillation (pmAF) based on information from the Gene Ontology (GO) database to relate expression changes of single transcripts to known remodeling processes.Moreover, atrial fibrillation has been shown to be associated with an atrial-to-ventricular switch by expr...

This large international radiation dose survey demonstrates considerable reduction of radiation exposure in coronary CTA during the last decade. However, the large inter-site variability in radiation exposure underlines the need for further site-specific training and adaptation of contemporary cardiac scan protocols.

The purpose of our investigation was to identify the transcriptional basis for ultrastructural and functional specialization of human atria and ventricles. Using exploratory microarray analysis (Affymetrix U133A+B), we detected 11,740 transcripts expressed in human heart, representing the most comprehensive report of the human myocardial transcriptome to date. Variation in gene expression between atria and ventricles accounted for the largest differences in this data set, as 3.300 and 2.974 transcripts showed higher expression in atria and ventricles, respectively. Functional classification based on Gene Ontology identified chamber-specific patterns of gene expression and provided molecular insights into the regional specialization of cardiomyocytes, correlating important functional pathways to transcriptional activity: Ventricular myocytes preferentially express genes satisfying contractile and energetic requirements, while atrial myocytes exhibit specific transcriptional activities related to neurohumoral function. In addition, several pro-fibrotic and apoptotic pathways were concentrated in atrial myocardium, substantiating the higher susceptibility of atria to programmed cell death and extracellular matrix remodelling observed in human and experimental animal models of heart failure. Differences in transcriptional profiles of atrial and ventricular myocardium thus provide molecular insights into myocardial cell diversity and distinct region-specific adaptations to physiological and pathophysiological conditions. Moreover, as major functional classes of atrial- and ventricular-specific transcripts were common to human and murine myocardium, an evolutionarily conserved chamber-specific expression pattern in mammalian myocardium is suggested.

DEBR provides significant advantages, even over manually corrected SBBR. As it works completely automatically, it can effectively help to cope with the data load of CT angiography exams. Furthermore, it enables the removal of intraluminal plaques, which provides a benefit for the estimation of the residual lumen.

The goal of our study was to compare a prospective triggering (PT) CT technique with retrospectively gated (RG) CT techniques in coronary computed tomographic angiograms (CCTA) with respect to image quality and radiation dose. Sixty consecutive patients were enrolled. CCTAs using the RG technique were obtained with a dual-source 64-slice CT system in 40 patients, using ECG-triggered tube current modulation, with either a broad pulsing window at 30-80% of the RR interval (group RGb, 20 patients, heart rate > 70 bpm) or a small pulsing window at 70% (group RGs, 20 patients, heart rate < 70 bpm). The other 20 patients underwent CCTA using the PT technique on a 128-slice CT system (group PT, heart rate < 70 bpm). All images were evaluated by two observers for quality on a three-point scale, with 1 being excellent and 3 being insufficient. The effective radiation dose was calculated for each patient. The average image quality score was 1.5 +/- 0.6 for PT, 1.35 +/- 0.5 for RGs and 1.65 +/- 0.5 for RGb. The mean effective dose for RGb was 9 +/- 4 mSv, for RGs 7 +/- 3 mSv and for PT 3 +/- 1 mSv. This represents a 57% dose reduction for PT compared with RGs and a 67% dose reduction for PT compared with RGb. In conclusion, in selected patients CCTA with the PT technique offers adequate image quality with a significantly lower radiation dose compared with CCTA using RG techniques.

The image quality of coronary CT angiograms obtained with a DSCT is satisfactory in most patients with AF. In the majority of patients with high and irregular heart rate, the absolute forward approach with end-systolic reconstruction 300 milliseconds after the R-peak yield a higher image quality than diastolic reconstructions. As a result of a significant improvement in temporal resolution, DSCT coronary angiography is feasible in patients with AF and can be used to exclude coronary artery disease in this patient cohort.

Compared with QCA, the automated detection algorithm evaluated has relatively high accuracy for diagnosing significant coronary artery stenosis at cCTA. If used as a second reader, the high negative predictive value may further enhance the confidence of excluding significant stenosis based on a normal or near-normal cCTA study.

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