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Todd Hunter: Discussion

A 64 year-old man develops chest pain on exertion. Risk factors for coronary disease include male sex over 45 years of age, and a positive family history with Todd's father first myocardial infarction at age 54 and death at age 60. The physical examination is normal. The EKG shows regular sinus rhythm and right bundle branch block (RBBB).

Diagnostic characteristics of the RBBB include widening of the QRS complex to .12 seconds or more, rsr' or rabbit ears configuration in leads V1 through V3, and a wide S wave in leads 1 and V6. Causes of RBBB include a normal variant present at birth, coronary disease, hypertension, and idiopathic conduction system fibrosis usually associated with advancing age.

Presumably the RBBB is new and may be a reflection of coronary artery disease. Given the classic symptoms and Todd's age the probability of significant coronary disease is approximately 93% (1). The goals of evaluation would be to identify any additional risk factors such as elevated homocysteine, type 2 diabetes, or abnormal lipid levels and to assess risk from CAD with a stress test.

It is important to note that left bundle branch block (LBBB) can interfere with EKG interpretation during exercise and calls for a stress imaging study. RBBB on the other hand does not mask exercise induced EKG change and does not require imaging for interpretation. If the stress test were markedly abnormal, a subsequent stress test with imaging could help clarify the risk for myocardial infarction or death.

The mainstays of medical treatment of chronic stable angina pectoris are aspirin and beta or calcium channel blocking drugs (2). One approach would be to start the aspirin 75-325 mg right away and prescribe nitroglycerine grains 1/150 sublingually as needed for severe or lasting chest pain (with instructions to call at once). The beta-blocker could be deferred until after the stress test as it may prevent the heart rate from rising to the target level (approximately 200-age in years).

If Todd were felt to be at high risk because of his stress test results or progressive symptoms, angiography (cardiac catheterization) would help determine if revascularization with angioplasty or surgery would be of benefit.

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