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Simultaneous intracoronary ultrasound and Doppler flow studies distinguish flow-mediated from receptor-mediated
S M Hollenberg1, P Tamburro, M R Johnson
1Section of Cardiology, Rush-Presbyterian-St. Luke's Medical Center, Chicago, Illinois 60612, USA. shollenb@rpslmc.edu
Insights
Early detection of atherosclerosis is possible by assessing endothelial dysfunction. This study used intravascular ultrasound and Doppler flow wire to differentiate receptor-mediated and flow-mediated responses, offering insights into coronary endothelial function.
Area of Science:
- Cardiovascular Medicine
- Vascular Biology
- Diagnostic Imaging
Background:
- Endothelial dysfunction is an early sign of atherosclerosis, potentially indicating disease development or extent.
- Decreased endothelium-dependent vasorelaxation is a key characteristic of endothelial dysfunction.
- Distinguishing between receptor-mediated and flow-mediated responses is crucial for accurate characterization.
Purpose of the Study:
- To evaluate coronary endothelial function using simultaneous intravascular ultrasound (IVUS) and Doppler flow measurements.
- To differentiate between receptor-mediated and flow-mediated endothelium-dependent vasodilatory responses.
- To assess the early stages of vascular disease in patients post-heart transplantation.
Main Methods:
- Simultaneous measurement of epicardial lumen area and coronary blood flow using IVUS and a Doppler flow wire.
- Intracoronary administration of adenosine (endothelium-independent), acetylcholine (endothelium-dependent), and nitroglycerin.
- Analysis of temporal changes in flow and lumen area to distinguish response types.
Main Results:
- Adenosine (endothelium-independent) showed peak flow at 18±2 sec and peak lumen area at 43±11 sec (P < 0.001).
- Acetylcholine (endothelium-dependent) induced an immediate increase in flow and area, with a second dilation peak and maximal area occurring 46 sec after maximal flow (54±14 vs. 100±26 sec, P < 0.001).
- The combined techniques successfully distinguished between receptor-mediated and flow-mediated responses.
Conclusions:
- Simultaneous IVUS and Doppler flow measurements effectively differentiate agonist-mediated and flow-mediated endothelial responses.
- This combined approach provides valuable insights into coronary endothelial function and early vascular disease.
- The findings highlight the importance of assessing distinct vasodilatory mechanisms in understanding endothelial dysfunction.
Abstract:
Abnormalities in vascular endothelial function, which occur early in atherosclerosis, may play an etiologic role in the development of the disease or represent a marker for the extent of atherosclerosis. Endothelial dysfunction, usually characterized by demonstration of decreased endothelium-dependent vasorelaxation, may be a sensitive and specific method to detect vascular disease in its earliest stages. In this context, separation of abnormalities in receptor-mediated and flow-mediated endothelium-dependent vasodilatory responses may allow for the most accurate characterization of endothelial dysfunction. In 35 patients undergoing routine annual cardiac catheterization after heart transplantation, changes in epicardial lumen area and coronary blood flow in response to intracoronary administration of adenosine, acetylcholine, and nitroglycerin were measured simultaneously using an intravascular ultrasound (IVUS) catheter positioned over a Doppler flow wire in the left anterior descending coronary artery. The combination of these techniques allowed for distinction between receptor-mediated and flow-mediated endothelium-dependent vascular responses. Peak flow with the endothelium-independent resistance vessel dilator adenosine occurred at 18+/-2 sec; the maximal lumen area response occurred later, at 43+/-11 sec (P < 0.001). Acetylcholine, an endothelium-dependent small- and large-vessel vasodilator, caused an immediate increase in both flow and lumen area, but a second peak of dilation was observed, and maximal area occurred 46 sec after maximal flow (54+/-14 vs. 100+/-26 sec, P < 0.001). Simultaneous IVUS and Doppler flow measurements after infusion of vasoactive agents allows for distinction between and evaluation of the relative contribution of agonist-mediated and flow-mediated responses, which may offer important and unique insights into coronary endothelial function.