| block vertebrae | Congenitally fused and hypoplastic vertebral bodies which, on radiographs, give the appearance of a more or less solid bony mass. See: Klippel-Feil syndrome. (05 Mar 2000) |
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| bone block | A surgical procedure in which the bone adjacent to the joint is modified to limit the motion of the joint mechanically; e.g., at the ankle joint to correct foot-drop by preventing extension below 90 |
| bundle-branch block | <cardiology, physiology> Abnormal conduction through one of the conductive branches which normally supply the right and left ventricles. Usually results in delayed conduction though either the right or left bundle branches where one ventricle is excited before the other because of absence of conduction in one of the branches of the bundle of His. Intraventricular block due to interruption of conduction in one of the two main branches of the bundle of His and manifested in the electrocardiogram by marked prolongation of the QRS complex; block of each branch has distinctive QRS morphology. (05 Mar 2000) |
| paracervical block anaesthesia | Regional anaesthesia of the cervix uteri by injection of local anaesthetic solution into tissues adjacent to the cervix. (05 Mar 2000) |
| genetic block | <biochemistry, molecular biology> An obstruction in a biochemical pathway caused by a mutation that has crippled production of an enzyme critical to the pathway. (07 May 1998) |
| partial heart block | Impulses penetrate the atrioventricular junction in some relation to the ventricular rate. Synonym: incomplete atrioventricular block. (05 Mar 2000) |
| retrograde block | Impaired conduction backward from the ventricles or A-V node into the atria. (05 Mar 2000) |
| peri-infarction block | An electrocardiographic abnormality associated with an old myocardial infarct and caused by delayed activation of the myocardium in the region of the infarct; characterised by an initial vector directed away from the infarcted region with the terminal vector directed toward it. (05 Mar 2000) |
| phase I block | Inhibition of nerve impulse transmission across the myoneural junction associated with depolarisation of the motor endplate, as in the muscle paralysis produced by succinylcholine. (05 Mar 2000) |
| phase II block | Inhibition of nerve impulse transmission across the myoneural junction unaccompanied by depolarisation of the motor endplate, as in the muscle paralysis produced by tubocurarine. (05 Mar 2000) |
| Mobitz block | Second degree atrioventricular block in which there is a ratio of two or more atrial deflections (P waves) to ventricular responses. Mobitz types of atrioventricular block, type I, the dropped beat of the Wenckebach phenomenon; type II, a dropped cardiac cycle that occurs without alteration in the conduction of the preceding intervals. (05 Mar 2000) |
| Wenckebach block | A form of block in any cardiac tissue (most often the atrioventricular junction) in which there is progressive lengthening of conduction until the beat is dropped. (05 Mar 2000) |
| complete A-V block | complete atrioventricular dissociation, complete A-V dissociation |
| Wilson block | The commonest form of right bundle-branch block, characterised in lead I by a tall slender R wave followed by a wider S wave of lower voltage. (05 Mar 2000) |
| Wolff-Chaikoff block | Blocking of the organic binding of iodine and its incorporation into hormone caused by large doses of iodine; usually a transient effect, but in large doses in susceptible individuals it can be prolonged and cause iodine myxoedema. Synonym: Wolff-Chaikoff effect. (05 Mar 2000) |