A condition in which the reversal of electrical charge is delayed or blocked at the atrioventricular (A-V) node or a more distal site. A-V block can be partial or complete and can occur in various degrees.

Etiologic factors related to first-, second- and third-degree heart block are as follows:

• First-degree atrioventricular heart block: It occurs often without symptoms, and may be physiologic. It is often seen in well-trained athletes. This block is characterized by a prolonged PR interval which can also occur with acute rheumatic fever, inferior myocardial infarctions (MIs [heart attacks that occur in the lower section of the heart]), hypothyroidism, and sarcoid heart disease. In addition, the condition is a common symptom of the effect of digitalis toxicity or potassium imbalance.

• Second-degree atrioventricular heart block: It is characterized by P waves that are not always followed by QRS complexes. There are three variations of this type of block. They are based on the characteristics of the PR interval, and when in the cycle, the QRS is dropped. The importance of this type of block is related to the risk of it developing into complete heart block. The types of second-degree A-V block that have been regarded as more serious are identified as the high-grade and the Mobitz II blocks.

• Third-degree atrioventricular heart block: It is characterized by no electrical communication between the atria and the ventricles.

First-degree heart block usually occurs without symptoms. In second-degree heart block, symptoms may or may not occur. Finally, in third-degree heart block, syncope, dizziness, and acute heart failure are more common, but may or may not occur. Depending on the set rate of the pacemaker, patients usually experience less acute symptoms, e.g., lethargy, postural hypotension, and breathlessness. In addition, asystole is a continual threat.

Tests for the condition include: an electrocardiogram (EKG) which reveals a record of the electrical activity of the heart, and a Holter monitor. Laboratory tests to evaluate for drug toxicity may be used to diagnose A-V blocks. In addition, electrophysiology studies may be necessary for precise localization of the block.

Treatment depends on the underlying cause or the associated diagnosis or both. Discontinuing digitalis and careful re-institution of the drug at a lower dose can treat complete heart block due to digitalis; temporary pacing may be needed in the meantime. As a complication of an inferior MI, third-degree heart block may respond to the drug, atropine, and the condition usually resolves spontaneously. However, when the condition is associated with anterior MI, it indicates an extensive MI with serious implications. A temporary pacemaker usually maintains cardiac output in this instance. Long-term management involves the use of a permanent pacemaker unless the heart heals after an inferior MI, which is rare, and the block resolves spontaneously.

Patients who are treated on a long-term basis with implanted pacemakers require follow-up, usually telephonically, to check the pacemaker's function. Failure rate for pacemaker equipment is now below 5%. The life expectancy rate of these devices varies from 4 to 10 years.

• Unusual cases of arrhythmia such as atrioventricular block associated with a supraventricular arrhythmia or pathological bradycardia should be submitted to the Director, Compensation and Pension Service. Simple delayed P-R conduction time, in the absence of other evidence of cardiac disease, is not a disability. (38 CFR 4.104 [Schedule of ratings-cardiovascular system])

• May be entitled to special monthly compensation where the Veteran has a single service-connected disability rated as 100% with additional service-connected disability or disabilities independently ratable at 60% or more, which are separate and distinct from the 100% service-connected disability and involves different anatomical segments or bodily systems. See  38 CFR 3.350(i)(1) – Special Monthly Compensation (SMC).

Note

• Evaluate cor pulmonale, which is a form of secondary heart disease, as part of the pulmonary condition that causes it.

• One MET (metabolic equivalent) is the energy cost of standing quietly at rest and represents an oxygen uptake of 3.5 milliliters per kilogram of body weight per minute. When the level of METs at which breathlessness, fatigue, angina, dizziness, or syncope develops is required for evaluation, and a laboratory determination of METs by exercise testing cannot be done for medical reasons, a medical examiner may estimate the level of activity (expressed in METs and supported by specific examples, such as slow stair climbing or shoveling snow) that results in those symptoms.

• For this general formula, heart failure symptoms include, but are not limited to, breathlessness, fatigue, angina, dizziness, arrhythmia, palpitations, or syncope. (Benign (First-Degree and Second-Degree, Type I)

• Evaluate under DC 7018 (implantable cardiac pacemakers). (Non-Benign (Second-Degree, Type II and Third-Degree)

• For DCs 7009, 7010, 7011, and 7015, a single evaluation will be assigned under the diagnostic code that reflects the predominant disability picture.

• The rating criteria for cardiovascular conditions underwent full-scale revision effective on November 14, 2021 and January 12, 1999.  A regulatory change was effective August 13, 1998, updated criteria for cold injury residuals under 38 CFR 4.104, DC 7122.  The changes are not considered liberalizing and should not be used as the basis for reduction unless the disability has actually improved.