Intracoronary Doppler Research Articles

Cardio-oesophageal reflex in humans as a mechanism for "linked angina'.

The aim of this study was to investigate the hypothesis that oesophageal acid stimulation reduces coronary blood flow in humans as a result of the presence of a cardio-oesophageal reflex which may provide a mechanism for "linked angina'. We studied the effect of oesophageal acid stimulation on coronary blood flow in 35 syndrome X patients and 24 heart transplant patients. A fine tube was positioned into the patient's distal oesophagus. An intracoronary Doppler catheter was positioned in the proximal left anterior descending coronary artery for coronary blood flow measurements. Oesophageal instillation of 0.1 M hydrochloric acid was performed (60 ml over 5 min) and the measurements were repeated. The coronary blood flow was significantly reduced by acid oesophageal stimulation in the syndrome X group [pre-acid 78.9 +/- 36.4 ml. min-1, post-acid 50.8 +/- 32.9 ml.min-1 (P = 0.0001)]. However, coronary blood flow in the heart transplant group, in whom the heart is denervated, was unaffected by acid infusion. We conclude that oesophageal acid stimulation can produce angina and significantly reduce coronary blood flow in humans. The lack of any significant effect in the heart transplant group, in whom the heart is denervated, suggests a neural reflex.

Coronary flow reserve and oesophageal dysfunction in syndrome X.

The relative prevalence of abnormalities of coronary flow reserve and oesophageal function was ascertained in 32 syndrome X patients with typical angina chest pain, a positive exercise test, and normal coronary arteries. Coronary flow reserve in response to a hyperaemic dose of papaverine was measured using an intracoronary Doppler catheter positioned in the left anterior descending coronary artery. An abnormal coronary flow reserve was defined as being < 3.0. Patients were investigated for oesophageal dysfunction by manometry and 24-hour pH monitoring. Thirteen patients had an impaired coronary flow reserve (group 1) and 19 patients had a normal flow reserve (group 2). Eight of the 13 group 1 patients (62%) and 13 of the 19 group 2 patients (68%, p = NS) had evidence of oesophageal dysfunction on either manometry or pH studies. Therefore, a total of 26 (81%) syndrome X patients had either an abnormality of coronary flow reserve or oesophageal dysfunction suggesting that chest pain in these patients may be due to myocardial ischaemia or oesophageal dysfunction, thus confirming the heterogeneous nature of this syndrome. The prevalence of oesophageal abnormalities was independent of any abnormalities of coronary flow reserve.

Dobutamine stress echocardiography results correlate with intracoronary doppler measures of coronary flow reserve

Dobutamine stress echocardiography results correlate with intracoronary doppler measures of coronary flow reserve

Coronary Arterial Flow-Velocity Dynamics in Children With Angiographically Normal Coronary Arteries

There have been few reports about coronary hemodynamics in children during the process of growth. In the present study, to assess the characteristics of coronary flow dynamics in children, we examined the phasic coronary flow-velocity (CFV) patterns at rest and during peak hyperemic responses in children with angiographically normal coronary arteries. Spectral Doppler phasic coronary flow velocity was recorded with a 0.018-in intracoronary Doppler guidewire at rest and during peak responses after intracoronary bolus injection of ATP in 30 patients with Kawasaki's disease (age, 8.2 +/- 5.1 years; 24 boys and 6 girls) without angiographic coronary lesions. Average peak velocity (APV), maximum peak velocity (MPV), and diastolic-to-systolic velocity ratio (DSVR) were evaluated in the left anterior descending coronary artery (LAD), left circumflex artery (LCx), and right coronary artery (RCA). Coronary vasodilator reserve (coronary flow reserve [CFR]) was calculated as the ratio of ATP-induced hyperemic to baseline APV. Flow-velocity parameters in RCA were significantly lower than those in the LAD and LCx in both proximal and distal portions. Although the distal LCx had significantly lower values of APV and MPV than did the proximal LCx, there was no significant difference between the proximal and distal portions of the LAD and RCA for APV and MPV. All three coronary vessels showed a diastolic dominant flow pattern in each segment. This coronary flow pattern was less marked in the RCA than in the LCA. All three coronary vessels showed a significant increase in APV and a significantly decrease in DSVR after ATP administration. CFR was significantly lower in the LCx than in the LAD or RCA (P < .01: 1.93 +/- 0.34 in LCx versus 2.32 +/- 0.42 in LAD and 2.37 +/- 0.44 in RCA). From the view of aging, it was revealed that APV values in three vessels were higher in the younger group than in the older group. CFR values in the LAD and LCx were significantly lower in the younger group than in the older group (P < .001 in LAD: 2.01 +/- 0.28 in the younger versus 2.53 +/- 0.37 in the older; P < .01 in LCx: 1.61 +/- 0.15 in the younger versus 2.06 +/- 0.31 in the older). In addition, intracoronary injection of ATP did not increase the absolute angiographic coronary luminal diameter. With the use of an intracoronary Doppler guidewire, we demonstrated that there are some characteristic findings in CFV dynamics in childhood. These physiological characteristics in CFV dynamics that occur with aging and occur in each vessel must be taken into consideration in the study of the coronary circulation in children.

Novel techniques of coronary artery imaging.

Intravascular ultrasound imaging and intracoronary Doppler flow mapping are two new techniques used to diagnose coronary artery disease. One provides detailed information about coronary morphology; the other assesses coronary function. By combining these two techniques, mechanisms of coronary syndromes that were previously unclear can be elucidated. The preliminary use of electron beam computed tomography in scanning of the coronary arteries has demonstrated the potential to identify severe coronary artery disease noninvasively. Coronary arteries can be imaged by intravenous injection of contrast material. Magnetic resonance imaging and positron-emission tomography are also used for the noninvasive visualization coronary arteries. Both techniques have been tested after interventions, which offers the potential to study myocardial function and perfusion.

Changes in phasic coronary blood flow velocity profile in relation to changes in hemodynamic parameters during stress in patients with aortic valve stenosis.

Alterations in phasic coronary flow profile have been demonstrated at rest in patients with aortic valve stenosis (AVS) but have never been studied under conditions of hemodynamic stress. Thirty-four patients with significant pure AVS (21 with exertional symptoms [group 1], 13 asymptomatic [group 2]) and 9 control subjects (group 3), all with normal coronary arteries, were studied successively at rest, during rapid atrial pacing, and after dobutamine infusion (5 to 30 micrograms.kg-1.min-1 i.v.) by proximal left anterior descending (LAD) intracoronary Doppler flow velocimetry concomitant with hemodynamic measurements. Systolic retrograde coronary flow velocity (CFV) was recorded only in patients with AVS, and its resting peak value was positively correlated with peak aortic pressure gradient (APG) (r = .63, P < .001). In group 1, there was lower aortic valve area (0.58 +/- 0.10 versus 0.75 +/- 0.08 cm2, P < .001) and higher resting APG and peak systolic retrograde CFV than in group 2, and also higher resting peak diastolic and mean CFV than in groups 2 and 3. In the two AVS groups, there were no changes from rest in APG and retrograde CFV at peak pacing rate; however, these parameters increased concomitantly and significantly at peak dobutamine stress. The ratio of the resting systolic to diastolic CFV curve area was inversely correlated with mean APG (r = -.54, P < .001); it was significantly lower in group 1 than in groups 2 and 3 (0.19 +/- 0.07 versus 0.29 +/- 0.10 and 0.30 +/- 0.04, respectively, both P < .005) and increased at peak pacing (group 1, to 0.29 +/- 0.14; group 2, to 0.39 +/- 0.12; group 3, to 0.38 +/- 0.07; all P < .001). At peak dobutamine stress, it decreased in patients with AVS (group 1, to 0.05 +/- 0.05; group 2, to 0.08 +/- 0.03; both P < .001) but did not change in group 3 (0.25 +/- 0.05). From rest to peak dobutamine stress, in both AVS groups there was increased retrograde systolic (group 1, 441 +/- 483%; group 2, 681 +/- 356%; both P < .001), decreased total systolic (group 1, -66 +/- 25%, P < .001; group 2, -19 +/- 24%; P = NS), and increased diastolic (group 1, 33.4 +/- 31.7%; group 2, 197.7 +/- 105.1%; both P < .001; group 1 versus group 2, P < .001) CFV curve area. In contrast, group 3 showed comparable increases in both systolic (143.5 +/- 44.4%) and diastolic (197.1 +/- 75.2%) CFV area (both P < .001). The stress-induced increases in the mean CFV and blood flow exceeded or were comparable with the concomitant increases in the estimated myocardial metabolic demand in groups 2 and 3 but were significantly lower in group 1. Stress-induced changes in LAD phasic CFV profile differ significantly between patients with and without AVS. In AVS, these changes are closely related to the concomitant stress-induced changes in hemodynamic parameters.

Significant Differences Between Side-Mounted and End-Mounted Intracoronary Doppler Flow Probes for the Measurement of Blood Flow Velocity

Use of the intracoronary Doppler flow probe is an established method for the assessment of coronary blood flow velocity. The aim of this study was to perform an in vitro comparison of two commonly used Doppler probes, which differ in the location of the piezoelectric crystal (end-mounted vs side-mounted). Blood flow velocity was measured over a wide range of flow rates in a flow simulator using heparinized whole blood. Measurements were made with both Doppler probes assessed in two positions (supported and unsupported) within the tubing. The results were compared with estimated true velocities. Further measurements were made with six side-mounted probes, correcting for the assumed crystal mounting angle and for the angle calculated from magnified images of the individual crystals. Mean velocities for end- and side-mounted probes correlated highly with predicted velocities (all r > or = 0.99), but the side-mounted probes significantly overestimated velocity by > 100%. Estimation of the true crystal mounting angle of the side-mounted probe revealed considerable variability (range 30-42 degrees) and was lower than the recommended angle correction factor of 60 degrees. Velocities corrected for the individual crystal mounting angles agreed more closely with predicted mean velocities. Although both probes are adequate for the assessment of relative changes in flow, the side-mounted probe considerably overestimates mean velocity, which is partly explained by the variable mounting angle of the crystal. The demonstrated limitations of the side-mounted Doppler flow probe in vitro should be considered in undertaking measurement of intracoronary blood flow velocity.

Differential characterization of blood flow, velocity, and vascular resistance between proximal and distal normal epicardial human coronary arteries: Analysis by intracoronary Doppler spectral flow velocity

To characterize coronary blood flow velocity parameters and to determine the relation among velocity, volumetric flow, and vascular resistance in awake human beings, we performed paired proximal and distal velocity measurements in 28 angiographically normal coronary arteries. Mean velocity, peak velocity, diastolic-to-systolic velocity ratio, and diameter and cross-sectional area of proximal and distal arteries were determined and coronary flow and vascular resistance computed. Mean velocity and coronary vasodilator reserve were similar for all three native arteries and were preserved from proximal to distal segments. Volumetric flow decreased from proximal to distal segments. The demonstrated inverse and curvilinear (polynomial) relation between volumetric flow and vascular resistance agrees with theoretical and animal models of coronary physiologic characteristics and suggests a nadir of coronary vascular resistance below which coronary flow no longer increases.

Intracoronary Doppler flow velocity measurements for the evaluation and treatment of coronary artery disease.

The functional significance of coronary artery disease is often inadequately revealed by the solely anatomic information provided by coronary angiography, especially with respect to intermediate-severity stenoses and the complex lesions that result from percutaneous coronary intervention. The clinical application of coronary flow velocity measurements using the Doppler flow wire during cardiac catheterization represents a promising means for providing immediate physiologic assessment of coronary artery lesion significance. Recent correlations with translesional hemodynamics and noninvasive perfusion imaging have confirmed the accuracy and reliability of Doppler translesional flow velocity assessment. The use of intracoronary flow velocity data for functional assessment can refine the selection of patients for revascularization. Furthermore, measurements of translesional and distal coronary flow velocity dynamics during procedures provide immediate data regarding the physiologic adequacy of the intervention. The information provided by the analysis of coronary blood flow using the Doppler guide wire can serve to improve the diagnostic and therapeutic capabilities of interventional cardiology.

Improvement of coronary morphology and blood flow after stenting. Assessment by intravascular ultrasound and intracoronary Doppler.

Intravascular ultrasound (IVUS) and intracoronary Doppler (ICD) were performed in eight patients (54.3 +/- 6.5 years, 6 male) immediately after PTCA and after stenting. ICD was also performed before PTCA. After PTCA, IVUS has demonstrated intimal rupture in all patients. After stenting, IVUS revealed wall wrapping of the intimal flap with a free lumen in all patients. The lumen diameter was 2.42 +/- 0.55 mm after PTCA and was 2.74 +/- 0.49 mm after stenting (p < 0.001). The cross-sectional area increased from 4.70 +/- 1.99 mm2 post-PTCA to 6.40 +/- 2.15 mm2 post-stent (p < 0.005). Coronary flow velocity reserve, calculated by the ratio of mean flow velocity at rest and after intracoronary papaverine administration, increased from 2.05 +/- 1.01 to 2.99 +/- 1.14 after PTCA (p = 0.015); and increased to 4.51 +/- 1.33 after stenting (p < 0.001). The morphological data derived from IVUS correlated with the functional information obtained with ICD. In addition to its established role in bail out situations, stent implantation may be considered when a suboptimal morphological and functional result has been demonstrated.

Prestenotic and Poststenotic Flow Measurement to Assess Severity of Coronary Artery Stenosis

The purpose of this study was to investigate differences between prestenotic and poststenotic intracoronary Doppler flow velocities and to determine whether these hemodynamic parameters of coronary flow demonstrate a correlation with geometrically measured coronary artery stenosis. A low-profile (0.018-in.) Doppler angioplasty guidewire capable of providing spectral flow velocity data was used to measure blood flow velocities both proximal and distal of 95 coronary artery stenoses ranging from 15% to 82% in diameter. Percent diameter stenoses were analyzed by quantitative coronary arteriography. In comparison with prestenotic measurements poststenotic Doppler flow velocities were markedly reduced in coronary artery stenoses with a diameter reduction greater than 50% in quantitative angiography. In stenoses less than 50% no difference between prestenotic and poststenotic parameters of coronary flow could be found. Prestenotic Doppler data demonstrated no correlation to percent diameter stenosis, whereas poststenotic flow data correlated moderately with percent diameter stenosis. Poststenotic Doppler data of stenoses below 50% differed significantly from stenoses above 50%. In conclusion, intracoronary Doppler flow velocity measurements performed distal to coronary artery stenoses contribute to the evaluation of hemodynamic significances of particular coronary artery stenoses.

Impaired Endothelium-Dependent Vasodilation of Coronary Resistance Vessels Is Associated With Exercise-Induced Myocardial Ischemia

The release of endothelium-derived relaxing factors has been shown experimentally to be of pivotal importance for the maintenance of coronary blood flow during increased demand. In humans with coronary atherosclerosis, endothelial vasodilator dysfunction is not confined only to epicardial conductance vessels but may also extend into the coronary microcirculation. We therefore tested the hypothesis that endothelial vasodilator dysfunction of the coronary resistance vasculature is associated with myocardial ischemia during exercise in patients without hemodynamically significant epicardial artery stenoses. Coronary vasodilator function was assessed by subselective infusion of the endothelium-dependent dilator acetylcholine (0.036 to 3.6 micrograms/mL) and the endothelium-independent dilator papaverine (7 mg). Coronary blood flow responses were evaluated by intracoronary Doppler flow velocity recordings and quantitative angiography. Exercise-induced myocardial perfusion was determined by 201Tl single photon emission computed tomographic imaging. Thirteen patients had exercise-induced myocardial perfusion defects suggestive of myocardial ischemia, whereas 14 patients had normal thallium imaging during exercise. In patients with exercise-induced thallium perfusion defects, coronary blood flow responses to acetylcholine were significantly (P < .005) blunted compared with patients with normal thallium imaging during exercise. In contrast, coronary blood flow reserve to the endothelium-independent smooth muscle relaxant papaverine was similar in the two groups. Patients with exercise-induced thallium perfusion defects exhibited a significantly (P < .005) reduced (23.9 +/- 9.0% [mean +/- SD]) endothelium-mediated coronary vasodilator capacity compared with patients with normal thallium testing (56.2 +/- 27.8%). Epicardial artery vasoreactivity to acetylcholine did not differ between the two groups. Impaired endothelium-dependent vasodilation of the coronary microcirculation is associated with exercise-induced myocardial ischemia in patients without hemodynamically significant epicardial artery lesions. Endothelial vasodilator dysfunction extending into the coronary microcirculation may thus contribute to the ischemic manifestations of coronary artery disease during times of increased myocardial demand.

Loss of Flow-Dependent Coronary Artery Dilatation in Patients With Hypertension

Abnormal endothelium-dependent coronary response to acetylcholine has been shown in patients with essential hypertension. We tested the hypothesis that flow-dependent dilatation, which has been shown in normal human coronary arteries, is impaired in hypertensive patients. The coronary vasomotor response to maximal increase of blood flow induced by papaverine was studied in 10 control subjects and in 14 hypertensive patients with no other risk factors and angiographically normal coronary arteries. After the injection of papaverine in the midportion of the left anterior descending coronary artery (LAD), the diameter of the proximal LAD (LAD1) was measured by quantitative angiography, whereas that of the proximal circumflex artery (LCx) served as control segment. Estimates of coronary blood flow in the distal LAD (LAD2) were calculated by intracoronary Doppler flow velocity measurements. An increase in LAD2 blood flow of 521 +/- 41% (P < .001) in control subjects was associated with a 17.0 +/- 3.3% dilatation of the LAD1 (P < .001) and with no significant change in the diameter of the LCx. In hypertensive patients, despite a comparable increase in LAD2 blood flow of 406 +/- 32% (P < .001), the LAD1 failed to dilate (-0.4 +/- 0.6%, NS). The dilative response to isosorbide dinitrate was similar in control subjects and hypertensive patients (30.0 +/- 4.1%, P < .001 and 21.9 +/- 1.9%, P < .001, respectively). Thus, the flow-mediated coronary dilatation is lost in hypertensive patients, and this may impair normal dilatation observed in response to an increase in myocardial metabolic demand.

Improvement of subendocardial myocardial perfusion after percutaneous transluminal coronary angioplasty. A myocardial contrast echocardiography study with correlation between myocardial contrast reserve and Doppler coronary reserve.

After angioplasty coronary reserve improves but does not normalize in most patients. The purpose of this study was to examine before and after angioplasty coronary reserve and transmural myocardial blood flow distribution using myocardial contrast echocardiography. Twelve patients with left anterior descending coronary artery stenosis were investigated before and immediately after angioplasty. A Doppler catheter was placed in the proximal segment. Myocardial contrast echocardiography was performed by imaging the septum in M mode in a parasternal view using a 3.0-mL bolus of sonicated amidotrizoate sodium meglumine through the guiding catheter. The gray level before injection was subtracted from the gray level after injection to maximize contrast time-intensity curves. The area under the curve was used as an indicator of myocardial blood flow, and subendocardial/subepicardial ratios were measured. After baseline measurements were obtained, Doppler and echographic data were recorded after a bolus infusion of papaverine into the left main coronary artery. The same protocol was performed in patients after angioplasty and in five control subjects with normal coronary arteries. Before angioplasty, echocardiographic and Doppler coronary reserve were 2.57 +/- 0.48 and 2.54 +/- 0.57, respectively. Both increased after angioplasty to 3.65 +/- 0.57 and 3.36 +/- 0.70, respectively (P < .05). Coronary reserve values obtained in patients with these two methods under the different conditions and in control subjects were correlated (r = .81; P = .0001). Before angioplasty, subendocardial/subepicardial septal ratios decreased from 0.80 +/- 0.48 to 0.60 +/- 0.27 after papaverine (P < .05). However, after angioplasty, these ratios tended to increase, from 0.72 +/- 0.27 to 0.92 +/- 0.45 after papaverine, but they did not change in control subjects (1.11 +/- 0.23 to 0.92 +/- 0.11). These results show that myocardial contrast echocardiography yields flow reserve values that correlate with values obtained using intracoronary Doppler. This technique may be considered as an accurate tool to assess coronary reserve in humans.

Usefullness of intracoronary doppler flow measurements in intermediate coronary artery stenosis (ICAS): A comparative study with TL-201 myocard perfusion imaging

Usefullness of intracoronary doppler flow measurements in intermediate coronary artery stenosis (ICAS): A comparative study with TL-201 myocard perfusion imaging

Intracoronary doppler guide wire adenosine induced hyperemia versus split-dose Thallium-201 dipyridamole imaging for assessment coronary blood flow reserve

Intracoronary doppler guide wire adenosine induced hyperemia versus split-dose Thallium-201 dipyridamole imaging for assessment coronary blood flow reserve

Intracoronary doppler flow measurement and TC-99m MIBI uptake in the assessment of intermediate coronary artery stenosts

Intracoronary doppler flow measurement and TC-99m MIBI uptake in the assessment of intermediate coronary artery stenosts

752-6 Visualization of Coronary Arteries and Measurement of Coronary Blood Flow with Transthoracic Echocardiography After Intravenous Administration of a New Echocardlographic Contrast Agent

Imagent ® US (AF0145, Alliance Pharmaceutical Corp.), a new hemodynamically inert perfluorochemical echocardiographic contrast agent, produces excellent left ventricular and blood pool contrast effect after intravenous administration when imaged with conventional (2-D) ultrasound. We evaluated the potential of Contrast Specific Imaging (Acuson) employing second harmonic principles to further enhance the visualization of structures containing contrast agents. Transthoracic images were obtained during injections of 10–40 mg of the agent into the left femoral vein of seven closed chest dogs. Coronary Dopplerflow was simultaneously measured using an intracoronary Doppler wire. No alterations in flow velocities were observed with contrast administration. There was heterogenous opacification of the myocardium following contrast injection: a striking finding was of contrast-enhanced linear, branching structures in the myocardium consistent with coronary vessels. Further exploration of the largest structures (2–3 mm diameter) in the region of the basal ventricular septum was technically possible with pulsed wave Doppler in two dogs. A characteristic coronary Doppler flow pattern was observed (Fig 1a). Transthoracic Doppler flow velocities transiently increased after intracoronary adenosine (Fig 1b). The calculated coronary flow reserve ratio was similar to simultaneous intracoronary Doppler measurements. Intramyocardial coronaryvasculature was observed and coronary flow velocites were measured during transthoracic Contrast Specific Imaging with an intravenously administered contrast agent. These findings suggest that noninvasive assessment of coronary blood flow is possible with echocardiographic contrast enhancement.

995-17 Are Intracoronary Doppler Flow Velocity Measurements Accurate for Assessment of Coronary Flow Reserve?

Coronary flow reserve (CFR) measurements are useful for assessment of coronary stenoses and microvascular function in patients. Intracoronary Doppler probes are commonly used for CFR measurement, but changes in flow velocity reflect volumetric flow only if the conduit vessel size is constant. We hypothesized that potent resistance vessel dilators used for CFR measurement also produce conduit artery dilation that perturbs the relationship between coronary flow velocity and volumetric flow. Coronary flow velocimetry (Doppler-tipped guidewire) and quantitative angiography were performed in a non-stenotic artery at control (Con), and during a maximally dilating dose of intracoronary adenosine before and after nitroglycerin (NTG) 100 μg i.c. in 6 patients. CFR was measured conventionally using peak/rest flow velocity changes alone (Vel) and flow estimates incorporating angiographic vessel cross-sectional area (VxA). (mean ± s.e.m.) Coronary Diameter (mm) CFR Con adenosine NTG Con Vel Can VxA NTG Vel 2.50 ± 0.26 2.89 ± 0.30 * 2.93 ± 0.28 * 3.0 ± 0.2 4.0 ± 0.3 † 3.8 ± 0.4 ‡ * p &lt; 0.01 vs control † p &lt; 0.01 vs can Vel ‡ p = 0.08 vs can Vel 1) Intracoronary adenosine produces concurrent conduit as well as resistance vessel dilation that is similar in magnitude to nitroglycerin. 2) Coronary flow reserve is underestimated if blood flow changes are assessed using flow velocity measurements alone. 3) Coronary flow reserve measured using velocity changes after pretreatment with nitroglycerin is similar to measurement that incorporates angiographic cross-sectional area, and may obviate the need for area determination.

814-3 Effect of Estradiol-17β upon Coronary Arterial Reactivity to Acetylcholine in Men with Coronary Artery Disease

Estradiol-17β (E) has been shown to improve exercise-induced myocardial ischemia and reverse acetylcholine (ACh)-induced coronary constriction in female patients with coronary artery disease (CAD). To test this latter effect in men we studied the effect of intracoronary administration of E (2.5 μ g) in 7 male patients with proven CAD (mean age 52 years). All patients underwent measurements of coronary artery diameter and coronary blood flow at rest, after control infusion and after infusion of ACh 1.6 and 16 μ g per min, using quantitative angiography and intracoronary Doppler flowmetry. Infusions were performed before and 20 minutes after the intracoronary administration of E. Coronary artery diameter was similar after either control or estradiol-17 β (mean ± SD; 2.9 ± 0.6 vs 2.8 ± 0.5 mm respectively. P = NS). E had no effect on the ACh-induced coronary constriction (ACh 1.6 μ g per min; 2.7 ± 0.3 vs 2.7 ± 0.2 mm, P = NS; ACh 16 μ g per min; 2.6 ± 0.3 vs 2.6 ± 03 mm, P = NS; post E vs pre E respectively). Likewise, E had no effect on basal coronary blood flow compared to control (77 ± 11 vs 75 ± 10 mL/min respectively, P = NS). E had no effect on the ACh-induced changes in coronary blood flow (ACh 1.6 μg per min; 95 ± 19 vs 90 ± 22 mL/min, P = NS; ACh 16 μg per min; 142 ± 27 vs 137 ± 39 mL/min, P = NS, post vs pre E respectively) Estradiol-17 β does not appearto attenuate acetylcholine-induced coronary constriction nor enhance acetylcholine-induced coronary blood flow in male atherosclerotic coronary arteries in vivo . This is in contrast to the effect of estrogen in menopausal females. This suggests that the coronary vasculature reacts differently to estrogen in males and females