| atrioventricular block | <cardiology> A conduction disturbance that results in the inappropriate delay (or complete inability) of a electrical impulse, generated in the atria, to reach the ventricles (via the atrioventricular node). Clinical types are divided into first (nonserious), second and third degree (most serious). Some drugs may precipitate atrioventricular block (for example clonidine, methyldopa, verapamil). A permanent pacemaker may be required for a third degree (complete) heart block. (02 Jan 1998) |
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| atrioventricular bundle | The bundle of modified cardiac muscle fibres that begins at the atrioventricular node as the trunk of the atrioventricular bundle and passes through the right atrioventricular fibrous ring to the membranous part of the interventricular septum where the trunk divides into two branches, the right crus of the atrioventricular bundle and the left crus of the atrioventricular bundle; the two crura ramify in the subendocardium of their respective ventricles. Synonym: fasciculus atrioventricularis, atrioventricular band, Gaskell's bridge, His' band, His' bundle, bundle of His, Keith's bundle, Kent's bundle, Kent-His bundle, ventriculonector. (05 Mar 2000) |
| atrioventricular canal | The canal in the embryonic heart leading from the common sinuatrial chamber to the ventricle. (05 Mar 2000) |
| atrioventricular canal cushions | A pair of mounds of embryonic connective tissue covered by endothelium, bulging into the embryonic atrioventricular canal; located one dorsally and one ventrally, they grow together and fuse with each other and with the lower edge of the septum primum, dividing the originally single canal into right and left atrioventricular orifices. Synonym: endocardial cushions. (05 Mar 2000) |
| atrioventricular conduction | Forward conduction of the cardiac impulse from atria to ventricles via the A-V node or any bypass tract, represented in the electrocardiogram by the P-R interval. P-H conduction time is from the onset of the P wave to the first high frequency component of the His bundle electrogram (normally 119 ± 38 msec); A-H conduction time is from the onset of the first high frequency component of the atrial electrogram to the first high frequency component of the His bundle electrogram (normally 92 ± 38 msec); P-A conduction time is from the onset of the P wave to the onset of the atrial electrogram (normally 27 ± 18 msec). (05 Mar 2000) |
| atrioventricular conduction abnormalities | <cardiology, physiology> Any condition which involves abnormal (blocked, delayed or aberrant) electrical conduction through the atrioventricular node (for example atrioventricular block). Some medications may precipitate atrioventricular conduction abnormalities. (02 Jan 1998) |
| atrioventricular connections | The five distinct and discrete ways in which the atrial chambers may be connected to the ventricles are concordant, discordant, ambiguous, double inlet, and univentricular. (05 Mar 2000) |
| atrioventricular dissociation | Any situation in which atria and ventricles are activated and contract independently, as in complete A-V block, more specifically, the dissociation between atria and ventricles that results from slowing of the atrial pacemaker or acceleration of the ventricular pacemaker at nearly equal (rarely equal) rates, each depolarising its own chamber, thus interfering with depolarisation by the other (interference-dissociation). (05 Mar 2000) |
| atrioventricular extrasystole | An extrasystole arising from the "junctional" tissues, either the A-V node or A-V bundle. Synonym: junctional extrasystole. (05 Mar 2000) |
| atrioventricular gradient | The diastolic pressure difference between the atrium and ventricle. (05 Mar 2000) |
| atrioventricular groove | A groove on the outer surface of the heart marking the division between the atria and the ventricles. Synonym: sulcus coronarius, atrioventricular groove, atrioventricular sulcus, auriculoventricular groove, coronary sulcus. (05 Mar 2000) |
| atrioventricular interval | The time between depolarisation of the atria and of the ventricle. Synonym: atrioventricular interval. (05 Mar 2000) |
| atrioventricular nodal branch | The atrioventricular branches or the nodal branches, the small arteries supplying the atrioventricular node; they usually arise from the right coronary artery where it starts to descend the posterior interventricular sulcus. Synonym: ramus nodi atrioventricularis, atrioventricular nodal branch, branch to atrioventricular node. (05 Mar 2000) |
| atrioventricular nodal extrasystole | A premature beat arising from the A-V junction and leading to a simultaneous or almost simultaneous contraction of atria and ventricles. (05 Mar 2000) |
| atrioventricular node | <cardiology> The location in the heart's conduction system, between the atria and the ventricles, which conducts the normal electrical impulse from the atria to the ventricles. (27 Sep 1997) |