Leaving out control groups: an internal contrast analysis of gene expression profiles in atrial fibrillation patients--a systems biology approach to clinical categorization

The QT Interval as a Noninvasive Marker of Atrial Refractoriness

BACKGROUND

Atrial refractoriness may be an important determinant of atrial fibrillation (AF) risk, but its measurement is not clinically accessible. Because the QT interval predicts incident AF and the atrium and ventricle share repolarizing ion currents, we investigated the association between an individual's QT interval and atrial effective refractory period (AERP).

METHODS

In paroxysmal AF patients presenting for catheter ablation, the QT interval was measured from the surface 12-lead electrocardiogram. The AERP was defined as the longest S1-S2 coupling interval without atrial capture using a 600-ms drive cycle length.

RESULTS

In 28 patients, there was a positive correlation between QTc and mean AERP. After multivariate adjustment, a 1-ms increase in QTc predicted a 0.70-ms increase in AERP.

CONCLUSIONS

The QTc interval reflects the AERP, suggesting that the QTc interval may be used as a marker of atrial refractoriness relevant to assessing AF risk and mechanism-specific therapeutic strategies.

Modelling of mouse experimental colitis by global property screens: a holistic approach to assess drug effects in inflammatory bowel disease

Preclinical disease models play an important role in the establishment of new treatment paradigms, identification of biomarkers and assessment of drug efficacy and safety. However, the accuracy of these models in context of the human disease are sometimes questioned, e.g. due to trials failing to confirm efficacy in humans. We suggest that one reason behind this gap in predictability may relate to how the preclinical data is analyzed and interpreted. In the present paper, we introduce a holistic approach to analyze and illustrate data in context of one of the most commonly used colitis models, i.e. the mouse dextran sulphate sodium (DSS) colitis model. Diseased mice were followed over time along disease progression and by use of tool pharmacological compounds activating nuclear hormone receptors, respectively. A new multivariate statistics approach was applied including principal component analysis (PCA) with treatment prediction subsequent to establishing the principal component analysis model. Thus, several studies could be overlaid and compared to each other in a new, comprehensive and holistic way. This method, named mouse colitis global property screening, appears applicable not only to any animal modelling series of studies but also to human clinical studies. The prerequisites for the study set up and calculations are delineated and examples of new learnings from the global property screening will be presented.

A clinical cardiology perspective of thrombophilias

Thrombophilias, an inherited and/or acquired predisposition to vascular thrombosis beyond hemostatic needs are common in cardiovascular medicine and include systemic disorders such as coronary atherosclerosis, atrial fibrillation, exogenous obesity, metabolic syndrome, collagen vascular disease, human immunodeficiency virus, blood replacement therapy and several commonly used medications. A contemporary approach to patients with suspected thrombophilias, in addition to a very selective investigation for gain-of-function and loss-of-function gene mutations affecting thromboresistance, must consider prevalent diseases and management decisions encountered regularly by cardiologists in clinical practice. An appropriate recognition of common disease states as thrombophilias will also stimulate platforms for much needed scientific investigation.