Impression:
First Study :
- Shortly after admission.
Mild increased RV uptake (1+) at rest and stress (arrows with "RV").
Small apical-inferior-lateral perfusion defect at rest, consistent with but not diagnostic of myocardial injury.
Extensive and severe ischemia in apex, apical-anterior, inferior, and posterior septum segments (small lines).
Coronary angiography :
LAD - 30-40% stenosis
RCA (dominant) - 40-50% stenosis
Contrast injection in RCA was associated with catheter-induced spasm that resolved following intracoronary nitroglycerine
Second Study :
- Post 1 week treatment with calcium channel blockers and abstinence from cocaine.
Small fixed apical-inferior-lateral perfusion defect at rest (arrows) -- consistent with, but not diagnostic of a small MI.
No evidence of stress-induced perfusion abnormalitis detected at the cardiac workload achieved.
Compared with previous study one week before, the stress-induced ischemia are no longer present.
Comments :
- The catheter-induced vasospasm of the RCA reflects the labile vasospasm often seen in cocaine abuse. The initial stress-induced ischemia in the RCA territory (with only 40-50% stenosis) likely represents vasospasm during stress.
- Notice the fall in BP during the stress study (after treatment and abstinence)
Possible explanation: cocaine abuse leads to norepinephrine depletion, resulting in an imbalance between epinephrine and norepinephrine control of the vascular tonus. Since epinephrine has a greater effect on the beta receptors in the blood vessels, and blood levels of epinephrine increase considerably during exercise, it leads to a five to sixfold increase in the blood flow to the muscle mass. This is followed by a decrease in the peripheral resistance and a fall in BP during stress.
