Search

MR is a progressive disease, and patients may remain asymptomatic even when the condition has become severe, as compensatory mechanisms develop.

While SA node disease is a problem of impulse generation, atrioventricular (AV) conduction disease is one of impulse propagation. This manifests electrocardiographically with conduction delay or conduction block and results in bradycardia and pauses. TYPES OF ATRIOVENTICULAR BLOCKS   FIRST-DEGREE ATRIOVENTRICULAR BLOCK This is defined as a lag between the time that the SA node fires and actual depolarization of the atria. This rhythm is not recognizable on an ECG strip because a strip does not denote when the SA node fires.   SECOND-DEGREE ATRIOVENTRICULAR BLOCK Second degree SA blocks are broken down into two subcategories just like AV blocks are: Second degree type I (Wenckebach block): an irregular rhythm, and an R-R interval that gets progressively smaller, while the P-R interval remains constant, until a QRS segment is dropped Second degree type II (sinus exit block): A regular rhythm that may be normal or slow. It is followed by a pause that is a multiple of the P-P interval usually (2-4). Conduction across the SA node is normal until the time of the pause when it is blocked.   THIRD-DEGREE ATRIOVENTRICULAR BLOCK Third degree block is caused by failure to conduct them. The rhythm is irregular and either normal or slow. It is followed by a long pause that is not a multiple of the P-R interval. The pause ends with a P wave, instead of a junctional escape beat the way a sinus arrest would.   LEARN MORE: DIAGNOSIS  TREATMENT

MR is a progressive disease, and patients may remain asymptomatic even when the condition has become severe, as compensatory mechanisms develop.