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Josh Grimes: Discussion

Josh's symptoms of lightheadedness suggest diminished cerebral perfusion. The differential diagnosis is broad and includes intravascular plasma and/or red blood cell depletion, primary cardiac disorders, and cerebro-vascular disease.

The physical examination reveals bradycardia without evidence of structural heart disease such as cardiomegaly or murmur. The EKG confirms bradycardia with ventricular rate of about 38 beats per minute. The interpretation is complete heart block with junctional rhythm as evidenced by:

Fixed P-P intervals and R-R intervals
Lack of relationship between P waves and QRS complexes (the P waves "march through" the QRS complexes)
Narrow (supraventricular) QRS complexes originating in the AV node.

Normal lab tests help to rule out dehydration and anemia making it likely that Josh's symptoms result from the bradycardia associated with heart block. In older individuals heart block is usually associated with underlying coronary artery disease or idiopathic degenerative change in the conduction system. In younger people heart people heart block may be congenital or result from inflammation at the base of the heart associated with infections or collagen vascular diseases such as ankylosing spondylitis.

Dr. Grey felt that Josh probably had Stage 1 disseminated Lyme disease because the disease is prevalent in Coastal Connecticut and because Josh is exposed to deer ticks on his walks through the woods and salt marshes on his way to the Pox House. When Dr. Grey asked Josh if he recalled having had a tick bite or a rash, he did remember having a large red round spot on his thigh for two weeks beginning about 6 weeks ago.

Based on observations of untreated patients, it is believed to be self-limited. However treatment is considered prudent and the current recommendation is for doxycycline 100 mg BID for 4 weeks. Dr. Grey recommended that Josh be admitted to the hospital for cardiac monitoring during treatment. A Lyme antibody test was positive in the IGM and IGG fractions.

The heart block persisted for a week with a heart rate of about 40. The following week complete heart block gave way to the less worrisome Mobitz Type 1 and 2 block, and eventually sinus rhythm. Josh was discharged after10 days and returned to work soon after.

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