| intra-atrial block | Impaired conduction through the atria, manifested by widened and often notched P waves in the electrocardiogram. (05 Mar 2000) |
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| intraventricular block | Delayed conduction within the ventricular conducting system or myocardium, including bundle-branch, peri-infarction blocks, the fascicular blocks, excitation, and the W-P-W (pre-expectation) syndrome. (05 Mar 2000) |
| entrance block | An incompletely understood mechanism whereby a pacemaker is protected from being discharged by the impulse from another centre; the mechanism, usually conceived as an encircling zone of unidirectionally refractory tissue permitting egress of impulses from the centre but preventing access to the centre, is seen in operation in ventricular parasystole where the parasystolic centre is protected from discharge by the sinus pacemaker and so is able to maintain its intrinsic rhythm undisturbed. Synonym: entrance block, protection. (05 Mar 2000) |
| epidural block | An obstruction in the epidural space; used inaccurately to refer to epidural anaesthesia. (05 Mar 2000) |
| exit block | Inability of an impulse to leave its point of origin, the mechanism for which is conceived as an encircling zone of refractory tissue denying passage to the emerging impulse. (05 Mar 2000) |
| fascicular block | A condition based on the concept that the left branch of the bundle of His provides two of three major fascicles of a system of conduction, of which the right bundle branch constitutes the third, for the transmission of the cardiac impulse from the atrium above to the ventricles below the A-V node; block may occur in any or all fascicles, all three together producing complete A-V block. See: hemiblock. (05 Mar 2000) |
| unidirectional block | Block that prevents passage of an impulse when it approaches from one direction but not from the other, as when block in the A-V node prevents anterograde conduction to the ventricles while retrograde conduction to the atria remains intact. (05 Mar 2000) |
| field block | Regional anaesthesia produced by infiltration of local anaesthetic solution into tissues surrounding an operative field. (05 Mar 2000) |
| field block anaesthesia | Conduction anaesthesia in which small nerves are not anaesthetised individually, as in nerve block anaesthesia, but instead are blocked en masse by local anaesthetic solution injected to form a barrier proximal to the operative site. (05 Mar 2000) |
| first degree A-V block | See: atrioventricular block. (05 Mar 2000) |
| fish-block | See Fish-tackle. Source: Websters Dictionary (01 Mar 1998) |
| local nerve block | Infiltration of a local anesthetic around a peripheral nerve so as to produce anesthesia in the area supplied by the nerve. (16 Dec 1997) |