blood urea nitrogen: a measurement of nitrogen in the form of urea in the blood, usually reported as mg/dl, in common usage in the USA (each molecule of urea has two nitrogen atoms, each of molar mass 14 g/mol). Elsewhere, the concentration of urea in the serum is reported as mmol/L:
BUN or serum urea is used as a measure of kidney function but is less precise than the serum creatinine or estimates of glomerular filtration rate based on the serum creatinine (see eGFR). A disproportionate rise in blood urea nitrogen (or serum urea) compared with creatinine may be seen with volume depletion, cardiac failure, high protein diets, gastrointestinal bleeding, loss of muscle (the classic example is the bilateral amputee), and catabolic states associated with severe burns and fevers.
An abnormality of the conduction of electrical impulses through the ventricles of the HEART, resulting in delayed depolarisation of the ventricular muscle. The electrocardiograph (see ELECTROCARDIOGRAM (ECG)) shows characteristic widening of the QRS complexes. Abnormalities of the right and left bundle branches cause delayed contraction of the right and left ventricles respectively.... bundle branch block
Bundle of His, or atrioventricular bundle, is a bundle of special muscle ?bres which pass from the atria to the ventricles of the HEART and which form the pathway for the impulse which makes the ventricles contract, the impulse originating in the part of the atria known as the sinuatrial node.... bundle of his
(AV bundle, bundle of His) a bundle of modified heart muscle fibres (Purkinje fibres) passing from the *atrioventricular node forward to the septum between the ventricles, where it divides into right and left bundles, one for each ventricle. The fibres transmit contraction waves from the atria, via the AV node, to the ventricles.... atrioventricular bundle
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