| septal defect, atrial | A hole in the septum, the wall, between the atria, the upper chambers of the heart. Commonly called an asd. Asds are a major class of heart deformity that is present at birth (congenital cardiac malformation). (12 Dec 1998) |
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| septum, atrial | The wall between the two upper chambers (the right and left atrium) of the heart. (12 Dec 1998) |
| subsidiary atrial pacemaker | Secondary source for rhythmic control of the heart, available for controlling cardiac activity if the sinoatrial pacemaker fails; located within the crista terminalis and atrial free wall near the inferior vena cava. (05 Mar 2000) |
| defect, atrial septal | A hole in the septum, the wall, between the atria, the upper chambers of the heart. Commonly called an ASD. ASDs are a major class of congenital cardiac malformation. (12 Dec 1998) |
| intra-atrial | Within one or both of the atria of the heart. (05 Mar 2000) |
| intra-atrial block | Impaired conduction through the atria, manifested by widened and often notched P waves in the electrocardiogram. (05 Mar 2000) |
| intra-atrial conduction | Conduction of the cardiac impulse through the atrial myocardium, represented by the P wave in the electrocardiogram. (05 Mar 2000) |
| intra-atrial conduction time | The total duration of electrical activity of the atria in one cardiac cycle. (05 Mar 2000) |
| tachycardia, ectopic atrial | A tachycardia originating in the atrial myocardium and characterised by rates between 135 and 175 beats per minute. (12 Dec 1998) |
| tachycardia, paroxysmal atrial | Bouts of rapid, regular heart beating originating in the atrium (upper chamber of the heart). Often due to abnormalities in the av node relay station that lead to rapid firing of electrical impulses from the atrium which bypass the av node under certain conditions. These conditions include alcohol excess, stress, caffeine, overactive thyroid or excessive thyroid hormone intake, and certain drugs. Pat is an example of an arrhythmia where the abnormality is in the electrical system of the heart, while the heart muscle and valves may be normal. (12 Dec 1998) |
| fibrillation, atrial | An abnormal irregular heart rhythm whereby electrical signals are generated chaotically throughout the upper chambers (atria) of the heart. Although many persons with atrial fibrillation have no symptoms, the most common symptom is palpitations, an uncomfortable awareness of the rapid and irregular heartbeat. Atrial fibrillation can cause blood clots that travel from the heart to the brain, causing stroke. Treatment of atrial fibrillation involves controlling the risk factors, medications to slow the heart rate and/or convert the heart to normal rhythm, and preventing complications of blood clotting. (12 Dec 1998) |
| lateral atrial vein | A vein draining deep portions of the temporal and parietal lobes; it runs in the lateral wall of the lateral ventricle to terminate in the superior thalamostriate vein. Synonym: vena ventriculi lateralis lateralis, lateral atrial vein, lateral vein of lateral ventricle. (05 Mar 2000) |
| left atrial pressure | <radiology> 15-20 mm Hg redistribution 20-25 interstitial oedema 25-30 airspace oedema (12 Dec 1998) |
| adrenergic receptors | Reactive components of effector tissues, most of which are innervated by adrenergic postganglionic fibres of the sympathetic nervous system. Such receptor's can be activated by norepinephrine and/or epinephrine and by various adrenergic drugs; receptor activation results in a change in effector tissue function, such as contraction of arteriolar muscles or relaxation of bronchial muscles; adrenergic receptor's are divided into alpha-receptor's and beta-receptor's, on the basis of their response to various adrenergic activating and blocking agents. Synonym: adrenoceptor, adrenoreceptors. (05 Mar 2000) |
| alpha-adrenergic receptors | Adrenergic receptor's in effector tissues capable of selective activation and blockade by drugs; conceptually derived from the ability of certain agents, such as phenoxybenzamine, to block only some adrenergic receptor's and of other agents, such as methoxamine, to activate only the same adrenergic receptor's. Such receptor's are designated as alpha-receptors. Their activation results in physiological responses such as increased peripheral vascular resistance, mydriasis, and contraction of pilomotor muscles. (05 Mar 2000) |