| 释义 |
heart block
heart blockn. A condition in which faulty transmission of the impulses that control the heartbeat results in a lack of coordination in the contraction of the atria and ventricles of the heart.heart block n (Pathology) impaired conduction or blocking of the impulse that regulates the heartbeat, resulting in a lack of coordination between the beating of the atria and the ventricles. Also called: Adams-Stokes syndrome or atrioventricular block heart′ block`
n. a defect in the electrical impulses of the heart resulting in any of various arrhythmias or irregularities in the heartbeat. heart blockA condition in which the electrical impulses in the heart are blocked at points in the conduction system.Thesaurus| Noun | 1. |  heart block - recurrent sudden attacks of unconsciousness caused by impaired conduction of the impulse that regulates the heartbeatAdams-Stokes syndrome, atrioventricular block, Stokes-Adams syndromearrhythmia, cardiac arrhythmia - an abnormal rate of muscle contractions in the heart |
Heart Block
heart block[′härt ‚bläk] (medicine) The cardiac condition resulting from defective transmission of impulses from atrium to ventricle. Heart Block disruption of the conductivity of the nerve impulse along the conductive system of the heart. Types of heart blocks—intra-auricular (sinoauricular) blocks, au-riculoventricular (atrioventricular) blocks, and blocks of the peduncles of the bundle of His and of the terminal branches—are distinguished depending on the site of the disruption. Heart block may be caused by organic diseases of the myocardium (rheumocarditis, coronary cardiosclerosis), more rarely by intoxications, and also by functional disturbances of the nervous system (neuroses). It may be temporary or permanent, complete or partial. Bradycardia (slowing of the pulse to 18–10 beats per minute) is noted in cases of complete heart block; this leads to severe anemia of the brain accompanied by dizziness, loss of consciousness, and sometimes convulsions. Treatment is directed at eliminating the causes of the heart block. O. F. BORDIUG heart block
Heart Block DefinitionHeart block refers to a delay in the normal flow of electrical impulses that cause the heart to beat. They are further classified as first-, second-, or third-degree block.DescriptionThe muscles of the heart contract in a rhythmic order for each heart beat, because electrical impulses travel along a specific route called the conduction system. The main junction of this system is called the atrioventricular node (AV node). Just as on a highway, there are occasionally some delays getting the impulse from one point to another. These delays are classified according to their severity.In first-degree heart block, the signal is just slowed down a little as it travels along the defective part of the conduction system so that it arrives late traveling from the atrium to the ventricle.In second-degree heart block, not every impulse reaches its destination. The block may affect every other beat, every second or third beat, or be very rare. If the blockage is frequent, it results in an overall slowing of the heart called bradycardia.Third-degree block, also called complete heart block, is the most serious. When no signals can travel through the AV node, the heart uses its backup impulse generator in the lower portion of the heart. Though this impulse usually keeps the heart from stopping entirely, it is too slow to be an effective pump.Causes and symptomsFirst-degree heart block is fairly common. It is seen in teenagers, young adults and in well-trained athletes. The condition may be caused by rheumatic fever, some types of heart disease and by some drugs. First-degree heart block produces no symptoms.Some cases of second-degree heart block may benefit from an artificial pace-maker. Second-degree block can occasionally progress to third-degree.Third-degree heart block is a serious condition that affects the heart's ability to pump blood effectively. Symptoms include fainting, dizziness and sudden heart failure. If the ventricles beat more than 40 times per minute, symptoms are not as severe, but include tiredness, low blood pressure on standing, and shortness of breath.Young children who have received a forceful blunt chest injury, can experience first-, or second-degree heart block.DiagnosisDiagnosis of first-, and second-degree heart block is made by observing it on an electrocardiograph (ECG).Third-degree heart block usually results in symptoms such as fainting, dizziness and sudden heart failure, which require immediate medical care. A physical exam and ECG confirm the presence of heart block.TreatmentSome second- and almost all third-degree heart blocks require an artificial pacemaker. In an emergency, a temporary pacemaker can be used until an implanted device is advisable. Most people need the pacemaker for the rest of their lives.PrognosisMost people with first- and second-degree heart block don't even know they have it. For people with third-degree block, once the heart has been restored to its normal, dependable rhythm, most people live full and comfortable lives.ResourcesOrganizationsAmerican Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. http://www.americanheart.org.Key termsAtrioventricular node (AV node) — Highly specialized area of the heart muscle which transmits electrical impulses.Bradycardia — A slow heart rate, usually under 60 beats per minute.heart block impairment of conduction in heart excitation; often applied specifically to block" >atrioventricular block. See types listed at block.
When isolated impulses from the atria fail to reach the ventricles, heartbeats are missed and the block is called incomplete. When no impulses reach the ventricles from the atria the heart block is complete, with the result that the atria and the ventricles beat at separate rates. In this case the beats of the atria and ventricles remain regular but the rate of the ventricular beats is much slower.
Heart block can occur with various forms of heart disease and as a result of excessive dosages of certain medications such as digitalis. A particularly severe form of heart block is stokes-adams disease, in which sudden unconsciousness results from the slowed heartbeat. It may be accompanied by convulsions.
The treatment for heart block caused by digitalis overdosage is to stop the medication. When there is hemodynamic instability, an antidote, Fab (ovine)" >digoxin immune Fab (ovine) (Digibind), can be administered intravenously for more rapid reduction of serum levels. If there is no response, temporary pacing" >cardiac pacing is indicated.a·tri·o·ven·tric·u·lar block , AV blockpartial or complete block of electrical impulses originating in the atrium or sinus node, preventing them from reaching the AV node and ventricles. In first-degree AV block, there is prolongation of AV conduction time (PR interval); in second-degree AV block, some but not all atrial impulses fail to reach the ventricles, thus some ventricular beats are dropped; in complete AV block (third degree), complete atrioventricular dissociation (2) occurs; atria and ventricles beat independently. Synonym(s): block (3) , heart blockheart blockn. A condition in which faulty transmission of the impulses that control the heartbeat results in a lack of coordination in the contraction of the atria and ventricles of the heart.heart block Cardiology An arrhythmia in which an impulse is not conducted normally from the atria to the ventricles due a damaged cardiac conduction system Types 1st, 2nd, 3rd degree; various HBs can occur in the bundle of His or bundle branches Heart block First-degree Prolonged interval ≥ 200 ms/0.2 sec between atrial and ventricular depolarizations Second-degree A block of some, but not all, impulses traveling from the atria to the ventricles. It can take 2 forms • Mobitz Type I or Wenckebach phenomenon–successive prolongation of the P-R interval until one P-wave does not elicit a QRS response • Mobitz Type II block–occurs when occasional P-waves are blocked from ventricles Third-degree Complete Heart Block Condition in which all impulses from the atria are blocked; usually an ectopic focus in the ventricles takes over
heart block A functional dissociation between the contractions of the upper chambers of the heart and those of the lower, due to interruption of the specialized conducting muscle fibres in the heart that normally coordinate this relationship. Such damage is usually due to inadequate coronary blood supply to the heart muscle but may be due to other causes such as rheumatic fever, syphilis or tumour. In heart block the pulse is generally very slow, as the lower chambers can only beat at their intrinsically low rate. Heart block is one of the major indications for the implantation of an artificial PACEMAKER.LegalSeeBlockFinancialSeeblockAcronymsSeeHBheart block
Related to heart block: Complete heart block, First degree heart block, Second degree heart blockSynonyms for heart blocknoun recurrent sudden attacks of unconsciousness caused by impaired conduction of the impulse that regulates the heartbeatSynonyms- Adams-Stokes syndrome
- atrioventricular block
- Stokes-Adams syndrome
Related Words- arrhythmia
- cardiac arrhythmia
|