Third degree heart block - The primary concern with this condition is progression to a third-degree heart block. Of the two types of Second Degree Blocks, type II (Wenkebach) is considered MORE serious and MORE likely to progress to a third degree block. Hemodynamic stability determines treatment - When the patient demonstrates an adequate heart rate and hemodynamic stability, treatment is not indicated. However, if the patient demonstrates a slow escape rhythm insufficient to sustain cardiac output, the patient requires pacing. Treatment - Temporary pacing such as transcutaneous or intravenous methods may be indicated if there's an inadequate heart rate and hemodynamic instability. Contrary to a type I second degree block, atropine is typically ineffective. However, as a temporary solution, an isoproterenol (Isuprel) infusion can act as a chemical pacemaker until a pacemaker can be placed (2 to 20mcg/minute continuous infusion).
In general, second degree blocks are those where a P wave is present without a corresponding QRS complex. with Type II Second Degree blocks, a QRS complex is dropped WITHOUT a prolongation of the PR interval. Etiology is traced to complete blockage of the electric impulse below the AV node in the bundle of His or a bundle branch. Symptoms include palpitations and near-syncopal episodes.
