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heart attack

SEE: under attack.


The rhythmic contraction of the heart.

heart block

Interference with the normal transmission of electrical impulses through the conducting system of the heart. The condition is seen on electrocardiogram as a prolongation of the P-R interval, a widening of the QRS complex, a delay in the appearance of an expected beat, the loss of synchrony of atrial and ventricular beats, or dropped (missing) beats.

ETIOLOGY: Heart block may be produced by temporary changes in vagal tone, drugs or toxins (such as some antiarrhythmics or antihypertensives), infections (such as infective endocarditis or Lyme disease), fibrosis or other degenerative diseases of the conducting system, ischemia or infarction, or other mechanisms.

atrioventricular h.b. SEE: atrioventricular block.

bilateral bundle branch h.b. SEE: atrioventricular block.

bundle branch h.b. Bundle branch block.

complete h.b. A condition in which there is a complete dissociation between atrial and ventricular systoles. Ventricles may beat from their own pacemakers at a rate of 30 to 40 beats per minute while atria beat independently. SYN: third-degree h.b.

congenital h.b. Heart block present at birth, caused by faulty cardiac development in the womb, autoimmune diseases, or other causes.

fascicular h.b. A conduction defect in either or both of the subdivisions of the left bundle branch.

first-degree h.b. First-degree atrioventricular block.

interventricular h.b. Bundle branch block.

second-degree h.b. A form of atrioventricular block in which only some atrial impulses are conducted to the ventricles. Two variants exist: Mobitz I (Wenckebach) and Mobitz II. In Mobitz I, the P-R intervals become progressively longer until a QRS complex is dropped. Because of the dropped beats, the QRS complexes appear to be clustered (grouped beating) on the electrocardiogram. In Mobitz II, P-R intervals have a constant length, but QRS complexes are dropped periodically, usually every second, third, or fourth beat.

sinoatrial h.b. A partial or complete heart block characterized by interference in the passage of impulses from the sinoatrial node. SYN: sinoatrial block. SEE: sick sinus syndrome.

third-degree h.b. Complete h.b.


A burning sensation felt in the mid-epigastrium, behind the sternum, or in the throat caused by reflux of the acid contents of the stomach into the esophagus and usually related to reduced lower esophageal sphincter action, hiatal hernia, or increased abdominal pressure. SYN: brash; pyrosis. SEE: gastroesophageal reflux disease.

TREATMENT: Antacids, H2-receptor antagonists, e.g., famotidine, and proton pump inhibitors, e.g., esomeprazole are potentially effective remedies.


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