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Coronary flow velocity changes after intravenous dipyridamole infusion: measurements using intravascular Doppler
V Voudris1, A Manginas, V Vassilikos
1Cardiology Department, Onassis Cardiac Surgery Center, Athens, Greece.
Insights
Dipyridamole causes flow inhomogeneity in coronary arteries, leading to perfusion defects seen on thallium-201 imaging. This study directly proves this phenomenon using Doppler guide wires, linking flow reserve to stenosis severity.
Area of Science:
- Cardiovascular Physiology
- Diagnostic Imaging
- Interventional Cardiology
Background:
- Dipyridamole-induced vasodilation can cause significant coronary flow inhomogeneity.
- This inhomogeneity is thought to be responsible for perfusion defects observed in dipyridamole-thallium-201 scintigraphy.
- Intracoronary Doppler guide wires enable direct assessment of coronary flow velocity in normal and stenotic arteries.
Purpose of the Study:
- To assess changes in coronary flow velocity in stenotic and normal coronary arteries after dipyridamole administration.
- To evaluate the relationship between coronary flow velocity reserve, relative flow reserve, and stenosis severity.
- To correlate Doppler-derived flow reserve with thallium-201 perfusion defects.
Main Methods:
- Seventeen patients with stable angina and documented perfusion defects underwent assessment.
- Two Doppler guide wires were used to measure time-averaged peak velocity and diastolic/systolic velocity ratio.
- Measurements were taken at baseline and after dipyridamole infusion (0.56 mg/kg), with subsequent correlation analysis.
Main Results:
- No significant change in distal flow velocity was observed in the stenotic left anterior descending coronary artery.
- A significant increase in flow velocity was noted in the adjacent normal left circumflex coronary artery (162.4 +/- 39.8%).
- Poststenotic coronary flow velocity reserve correlated with lumen diameter stenosis (r = -0.66, p < 0.05), and relative flow reserve correlated with thallium-201 relative perfusion (r = 0.90, p < 0.001).
Conclusions:
- This study provides direct evidence of dipyridamole-induced coronary flow inhomogeneity causing thallium-201 perfusion defects.
- The degree of flow inhomogeneity is directly related to the extent of the perfusion defect observed on scintigraphy.
Objectives:
This study assessed changes in coronary flow velocity measured distal to a significant stenosis of the left anterior descending coronary artery and at the adjacent normal left circumflex coronary artery, produced by intravenous administration of dipyridamole, in patients undergoing coronary angioplasty with a documented perfusion defect on dipyridamole-thallium-201 scintigraphy.
Background:
Significant flow inhomogeneity is believed to develop during coronary vasodilation induced by dipyridamole, causing a defect in the thallium-201 scintigram. The recently developed intracoronary Doppler guide wire permits assessment of flow velocity variables in normal and stenotic arteries.
Methods:
In 17 patients with stable angina we studied changes in time-averaged peak velocity and the diastolic/systolic velocity ratio simultaneously using two 0.014-in. (0.36-mm) Doppler guide wires at baseline and after 4 min of dipyridamole infusion (0.56 mg/kg body weight). Coronary flow velocity reserve and relative flow reserve were correlated with the degree of stenosis on coronary angiography and quantitative analysis of thallium-201 images.
Results:
No changes in distal flow velocity was observed in the stenotic vessel (5.5 +/- 33.7% [mean +/- SD]), in contrast to a significant increase observed in the adjacent normal vessel (162.4 +/- 39.8%). Poststenotic coronary flow velocity reserve correlated with percent lumen diameter stenosis (r = -0.66, p < 0.05). A correlation was also observed between the relative flow reserve/thallium-201 relative perfusion ratio (r = 0.90, p < 0.001).
Conclusions:
To our knowledge, these findings represent the first direct proof of dipyridamole-induced flow inhomogeneity producing a perfusion defect on thallium-201 imaging. The degree of inhomogeneity is related to the extent of the perfusion defect.