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Published on: December 2, 2014
Effects of coronary artery narrowing, collaterals, and left ventricular function on the pattern of myocardial
Insights
Coronary artery disease severity impacts exercise thallium-201 perfusion patterns. Significant narrowing, especially in multiple vessels, generally causes abnormal perfusion, with collaterals not preventing this. ECG and ventricular function do not reliably predict perfusion defects.
Area of Science:
- Cardiology
- Nuclear Cardiology
- Diagnostic Imaging
Background:
- Exercise thallium-201 scintigraphy is a key diagnostic tool for assessing coronary artery disease (CAD).
- Understanding how coronary artery narrowing, disease extent, collaterals, and left ventricular function influence perfusion patterns is crucial for accurate interpretation.
Purpose of the Study:
- To evaluate the impact of coronary artery diameter narrowing (50-69%, 70-89%, ≥90%), extent of CAD (1VD, 2VD, 3VD), collaterals, and left ventricular function on exercise thallium-201 perfusion patterns.
Main Methods:
- Analysis of exercise thallium-201 perfusion patterns in 121 patients, categorized by coronary angiogram findings.
- Inclusion of data on degree of arterial narrowing, number of diseased vessels, presence of collaterals, ECG Q waves, and left ventriculogram findings.
Main Results:
- Patients with 50-69% narrowing in one vessel showed normal perfusion.
- Abnormal perfusion was common in 1VD (≥90% narrowing) and 2VD/3VD, unless narrowings were <90% or confined to the right coronary artery (RCA).
- Collaterals did not prevent abnormal perfusion; they supplied the most narrowed vessels, and abnormalities appeared in their distribution. ECG Q waves and akinetic segments did not correlate with perfusion defects.
Conclusions:
- Coronary artery stenosis severity and extent significantly dictate exercise thallium-201 perfusion abnormalities.
- Collateral circulation does not abolish perfusion defects in the territory of severely stenosed vessels.
- Myocardial infarction indicators (Q waves, akinetic segments) lack direct correlation with perfusion redistribution defects on thallium-201 imaging.
Abstract:
We evaluated effects of the degree of diameter narrowing of the coronary arteries (50-69%, 70-89%, greater than or equal to 90%); extent of coronary disease [one-vessel disease (1VD), two-vessel (2VD), three-vessel (3VD)]; collaterals; and left ventricular function on the pattern of exercise thallium-201 perfusion in 121 patients; 30 patients with normal coronary angiograms, 37 with 1VD, 24 with 2VD, and 30 with 3VD. Fifteen patients had Q waves on ECG, 29 patients had akinetic segments on the left ventriculogram, and 46 patients had collaterals. The results suggest the following: 1) Patients with 59-69% narrowing of one vessel have normal exercise perfusion. 2) All patients with 1VD have abnormal exercise perfusion if the degree of narrowing is greater than or equal to 90%, unless the right coronary artery (RCA) is the vessel involved. 3) Patients with 2VD and 3VD generally have abnormal exercise perfusion unless all the narrowings are < 90%, or the RCA is the only vessel with greater than or equal to 90% narrowing, or the stress is submaximal. 4) Collaterals do not protect against development of abnormal exercise perfusion; they feed the most severely narrowed vessel, and perfusion abnormalities are ordinarily seen in the distribution of such severely narrowed vessels. 5) Neither the presence of Q waves on the ECG nor an akinetic segment on the left ventriculogram correlates with defects in the redistribution images; residual defects may be seen in the delayed images despite the absence of prior myocardial infarction, and normal images may be seen despite the presence of akinetic segments in the left ventriculogram.
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