Complete heart block: Rx

Clinical - Cardiovascular

Also known as third-degree AV block, complete heart block is a condition where there is dissociation between the electrical activity of the atria and ventricles. As a result, the two chambers contract independently with the ventricle in its own rhythm. The ventricular escape rhythm is typically bradycardic, with heart rates usually less than 40 beats/min. This may result in a low cardiac output state with symptoms such as angina or pre-syncope.

The mainstay of treatment for complete heart block is pacing the ventricle . Depending on the acuity of the situation, transcutaneous, transvenous endocardial, or an epicardial pacemaker would be appropriate. Intravenous drugs may be used with caution as a temporizing measure while instituting pacing therapy. Atropine can be used for a very slow idioventricular escape rhythm or block from the AV node. Also, catecholamines (ex: isoproterenol) can be used transiently to increase heart rate.

According to ACE8B question 32: “Most commonly, patients with significant AV nodal dysfunction (including third-degree AV block and Mobitz type-II second-degree block) are paced with mode DDD following cardiac surgery.” The VOO mode is not recommended if the patient has an underlying ventricular rhythm as VOO increases the risk of V-fib due to R-on-T.


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