Increase In Average Peak Velocity Research Articles

Thermodilution-derived volumetric resting coronary blood flow measurement in humans.

Quantification of microvascular function requires the measurement of flow and resistance at rest and during hyperaemia. Continuous intracoronary thermodilution accurately measures coronary flow during hyperaemia. The aim of this study was to investigate whether continuous coronary thermodilution using lower infusion rates also enables volumetric coronary blood flow measurements (in mL/min) at rest. In 59 patients (88 arteries), the ratio of distal to proximal coronary pressure (Pd/Pa), as well as absolute blood flow (in mL/min) by continuous thermodilution, was recorded using a pressure/temperature guidewire. Saline was infused at rates of 10 and 20 mL/min. In 27 arteries, Doppler average peak velocity (APV) was measured simultaneously. Pd/Pa, APV, thermodilution-derived coronary flow reserve (CFRthermo) and coronary flow velocity reserve (CFVR) were assessed. In 10 arteries, simultaneous recordings were obtained at saline infusion rates of 6, 8, 10 and 20 mL/min. Compared to baseline, saline infusion at 10 mL/min did not change Pd/Pa (0.95±0.05 versus 0.94±0.05, p=0.49) or APV (22±8 versus 23±8 cm/s, p=0.60); conversely, an infusion rate of 20 mL/min induced a decrease in Pd/Pa and an increase in APV. Stable thermodilution tracings were obtained during saline infusion at 8 and 10 mL/min, but not at 6 mL/min. Mean values of CFRthermo and CFVR were similar (2.78±0.91 versus 2.76±1.06, p=0.935) and their individual values correlated closely (r=0.89, 95% CI: 0.78-0.95, p<0.001). In addition to hyperaemic flow, continuous thermodilution can quantify absolute resting coronary blood flow; therefore, it can be used to calculate coronary flow reserve and microvascular resistance reserve.

Thermodilution-derived resting coronary flow measurement: “a reverse dose finding study”

Abstract Background Hyperemic absolute coronary blood flow (in mL/min) can be safely and reproducibly measured with intracoronary continuous thermodilution of saline at room temperature at an infusion rate of 20 mL/min. This study aims at assessing the best infusion rate to measure resting flow by thermodilution, i.e. low enough to avoid microvascular dilation but high enough to allow reliable thermodilution tracings Methods and results In 26 coronary arteries (24 patients) with angiographic non-significant stenoses, absolute flow was assessed by continuous saline thermodilution at infusion rates of 10 mL/min and 20 mL/min using a pressure/temperature sensored guide wire, a dedicated infusion catheter and a dedicated software. Average peak velocity (APV) was measured simultaneously using an intracoronary Doppler-wire. In addition, in a subgroup of 10 arteries, absolute flow and APV were also measured during saline infusion at 6 ml/min and 8 ml/min. In 26 coronary arteries there was no significance difference in the Pd/Pa and in the APV at baseline and during the infusion of saline at 10 ml/min (Pd/Pa: 0.94±0.057 vs 0.94±0.059, p=0.82; APV: 22.2±8.40 vs 23.2±8.39 cm/s, p=0.63). In contrast, at an infusion rate of 20 mL/min, we observed a significant decrease in Pd/Pa compared to baseline (0.85±0.089 vs 0.95±0.053 vs, respectively, p&amp;lt;0.001) and a significant increase in APV (22.2±8.4 cm/s to 57.8±25.5 cm/s, respectively, p&amp;lt;0.001). The coronary flow reserve (CFR) evaluated by Doppler and intracoronary continuous thermodilution correlated well (r=0.87, 95% CI = 0.72–0.94, p&amp;lt;0.001) and Bland-Altman analysis documented a mean bias of −0.003 (limit of agreement −1.05 to 1.04) thus indicating the presence of resting coronary blood flow during the infusion of 10 mL/min of saline. In 10 coronary arteries saline infusions at 6 and 8 ml/min did not produce any significant changes in the Pd/Pa and in the APV compared to baseline and both Doppler and Thermodilution derived CFR correlated well at each infusion rate (6 ml/min: r=0.71, 95% CI 0.14–0.92, p=0.02; 8ml/min: r=0.78, 95% CI=0.31–0.95, p=0.007). However, with an infusion rate of 6 mL/min, an unstable thermodilution tracing was observed. Accordingly, Bland-Altman analysis showed a significantly larger dispersion of the CFR values when 6 ml/min was used to measure resting coronary flow (as compared with 8 m/min): mean bias at 6 ml/min: −0.53, limits of agreement: −2.25 to 1.20: mean bias at 8 ml/min: 0.004, limits of agreement: −0.72 to 0.73. Conclusion Absolute resting coronary flow can be measured by intracoronary continuous thermodilution of saline at infusion rate of 8–10 ml/min. Funding Acknowledgement Type of funding source: None

Quantifying coronary microvascular disease: assessing absolute microvascular resistance reserve (MRR) by continuous coronary thermodilution

Abstract Background and aim Hyperemic absolute coronary blood flow (in mL/min) can be safely and reproducibly measured with intracoronary continuous thermodilution of saline at room temperature at an infusion rate of 20 mL/min. This study aims at assessing whether continuous thermodilution can also measure resting flow and microvascular resistance. Methods and results In 87 coronary arteries (58 patients) with angiographic non-significant stenoses absolute flow was assessed by continuous thermodilution of saline at infusion rates of 10 mL/min and 20 mL/min using a pressure/temperature sensored guide wire, a dedicated infusion catheter and a dedicated software. In addition, in 26 arteries, average peak velocity (APV) was measured simultaneously using an intracoronary Doppler-wire. There was no significant difference between Pd/Pa at baseline and during saline infusion at 10 mL/min, (0.95±0.053 vs 0.94±0.054, respectively (p=0.53) and there was no significant difference in APV at baseline and during the infusion of saline at 10 mL/min (22.2±8.40 vs 23.2±8.39 cm/s, respectively, p=0.63), thus indicating presence of resting coronary blood flow during the infusion of 10 mL/min of saline. In contrast, at an infusion rate of 20 mL/min, a significant decrease in Pd/Pa was observed compared to baseline: (0.85±0.089 vs 0.95±0.053, respectively, p&amp;lt;0.001) and a significant increase in APV was observed (22.2±8.4 cm/s to 57.8±25.5 cm/s, respectively, p&amp;lt;0.001). The coronary flow reserve (CFR) calculated by thermodilution and by Doppler flow velocity were similar (2.73±0.85 vs 2.72±1.07, respectively) and their individual values correlated closely (r=0.87, 95% CI 0.72–0.94, p&amp;lt;0,001). Microvascular resistance (Rμ), defined as the distal coronary pressure divided by the absolute flow was calculated both at rest (Rμ-rest) and during hyperemia (Rμ-hyper). Microvascular Resistance Reserve (MRR), is calculated as the ratio of Rμ-rest and Rμ-hyper and showed a good correlation with the analogous Doppler-derived parameter (using the APV instead of absolute flow). Mean doppler and thermodilution derived MRR were similar (3.32±1.50 vs 3.23±1.16) and values correlated closely (r=0.91, 95% CI 0.81 - 0.96, p&amp;lt;0.001; Bland-Altman analysis: mean bias = 0.071, limit of agreement −1.195 to 1.338). Conclusion Absolute coronary blood flow (in mL/min) can be measured by continuous thermodilution both at rest and during hyperemia. This allows accurate, reproducible, and operator-independent direct volumetric calculation of CFR and MRR. The latter is a quantitative metric which is specific for microvascular function and independent from myocardial mass. Doppler and Thermodilution derived MRR Funding Acknowledgement Type of funding source: None

Measurement of Fractional Flow Reserve Predicts the Functional Significance of Peripheral Arterial Lesions in the Ischaemic Leg

Introduction - The current mainstay for investigating peripheral arterial disease (PAD) uses duplex ultrasound (DUS) and visual assessment of lesions by either computed tomography (CTA)/magnetic resonance (MRA) or invasive angiography (IA). In coronary vessels, Fractional Flow Reserve (FFR) measures the trans-stenotic pressure loss during maximum flow to determine the ‘functional’ significance and inform revascularisation. This study (i) investigated the relationship between anatomical (diameter stenosis, DS%) and functional (FFR) severity of peripheral arterial stenoses and (ii) correlated these parameters to limb tissue perfusion. Methods - Patients with short-distance claudication (IC) and critical limb ischaemia (CLI) underwent DUS and CTA. Pre-procedural blood oxygenation level-dependent cardiovascular magnetic resonance (BOLD-CMR; 3.0T Achieva, Philips Healthcare) was performed in both legs at rest and during reactive hyperaemia. T2* signal gradient during reactive hyperemia (Grad) of the calf muscles was recorded. During elective angioplasty/stenting, an 0.014” Doppler-flow and pressure-sensing guidewire (ComboWire XT®, Philips Healthcare) was used to measure the trans-stenotic pressure index (distal lesion pressure[Pd]/aortic pressure[Pa]) at rest (“Pd/Pa”) and during hyperaemia (“FFR”). Intra-arterial adenosine was used to provoke hyperaemia, which was confirmed by measuring the resting-to-hyperaemic change in average peak velocity (APV) and microvascular resistance (MVR, calculated as Pd/APV). Quantitative Vessel Analysis (Philips Allura Xper FD20, Philips Healthcare) was used to calculate percentage diameter stenosis (DS%) from CTA and IA. Follow up with DUS determined primary patency, defined as <50% restenosis in the treated segment. Results - Fifty-two stenoses (iliac n=33; femoral n=19) in 41 patients were evaluated; 59% had IC and 41% had CLI. Median DS% by DUS, CTA, and IA were 70% (IQR 60-86), 67% (52-77) and 61% (48-73), respectively. Pd/Pa and FFR were successfully measured in all patients with no complications. There was a significant increase in APV (14.9 cm/s (8.5-20.7) to 30 cm/s (18.2-44.8); p<0.0001) and reduction in MVR (6.8 (4.5-9.2) to 2.7 (1.7-3.9); p<0.0001) following adenosine administration. Median pre-treatment Pd/Pa was 0.91 (0.78-0.97) and FFR was 0.70 (0.52-0.87), which improved to 0.94 (0.86-0.98; p=0.001) and 0.90 (0.80-0.95; p<0.0001) after angioplasty/stenting, respectively. FFR correlated poorly with CTA and IA-DS% (R2=0.57-0.60; p<0.0001) and had a stronger association with clinical severity (CLI vs IC; AUC 0.96, p<0.0001). Perfusion in 18 ischaemic limbs (14 patients) was assessed with BOLD-CMR. FFR strongly correlated with Grad (R2=0.63; p<0.0001), whereas DS% (DUS, R2=0.18 [p=0.85]; CTA, R2=0.45 [p=0.001] and IA, R2=0.41 [p=0.003]) were poor predictors of limb perfusion. Forty patients (98%) were followed up for a median of 3 (1.8-4.1) months. A post-treatment FFR cut-off of 0.88 demonstrated a sensitivity and specificity of 75% for predicting primary patency (AUC 0.852; p Conclusion - FFR appears to be a useful index of functional severity and ischaemic burden related to peripheral arterial stenoses, and for predicting successful intervention. Clinical trials will determine whether it will become, as it has in the coronary circulation, the gold standard for making treatment decisions.

Repeated epinephrine doses during prolonged cardiopulmonary resuscitation have limited effects on myocardial blood flow: a randomized porcine study.

BackgroundIn current guidelines, prolonged cardiopulmonary resuscitation (CPR) mandates administration of repeated intravenous epinephrine (EPI) doses. This porcine study simulating a prolonged CPR-situation in the coronary catheterisation laboratory, explores the effect of EPI-administrations on coronary perfusion pressure (CPP), continuous coronary artery flow average peak velocity (APV) and amplitude spectrum area (AMSA).MethodsThirty-six pigs were randomized 1:1:1 to EPI 0.02 mg/kg/dose, EPI 0.03 mg/kg/dose or saline (control) in an experimental cardiac arrest (CA) model. During 15 minutes of mechanical chest compressions, four EPI/saline-injections were administered, and the effect on CPP, APV and AMSA were recorded. Comparisons were performed between the control and the two EPI-groups and a combination of the two EPI-groups, EPI-all.ResultCompared to the control group, maximum peak of CPP (Pmax) after injection 1 and 2 was significantly increased in the EPI-all group (p = 0.022, p = 0.016), in EPI 0.02-group after injection 2 and 3 (p = 0.023, p = 0.027) and in EPI 0.03-group after injection 1 (p = 0.013). At Pmax, APV increased only after first injection in both the EPI-all and the EPI 0.03-group compared with the control group (p = 0.011, p = 0.018). There was no statistical difference of AMSA at any Pmax. Seven out of 12 animals (58%) in each EPI-group versus 10 out of 12 (83%) achieved spontaneous circulation after CA.ConclusionIn an experimental CA-CPR pig model repeated doses of intravenous EPI results in a significant increase in APV only after the first injection despite increments in CPP also during the following 2 injections indicating inappropriate changes in coronary vascular resistance during subsequent EPI administration.

Coronary and Microvascular Physiology During Intra-Aortic Balloon Counterpulsation

This study sought to identify the effect of coronary autoregulation on myocardial perfusion during intra-aortic balloon pump (IABP) therapy. IABP is the most commonly used circulatory support device, although its efficacy in certain scenarios has been questioned. The impact of alterations in microvascular function on IABP efficacy has not previously been evaluated in humans. Thirteen patients with ischemic cardiomyopathy (left ventricular ejection fraction: 34 ± 8%) undergoing percutaneous coronary intervention were recruited. Simultaneous intracoronary pressure and Doppler-flow measurements were undertaken in the target vessel following percutaneous coronary intervention, during unassisted and IABP-assisted conditions. Coronary autoregulation was modulated by the use of intracoronary adenosine, inducing maximal hyperemia. Wave intensity analysis characterized the coronary wave energies associated with balloon counterpulsation. Two unique diastolic coronary waves were temporally associated with IABP device use; a forward compression wave and a forward expansion wave caused by inflation and deflation, respectively. During basal conditions, IABP therapy increased distal coronary pressure (82.4 ± 16.1 vs. 88.7 ± 17.8 mm Hg, p = 0.03), as well as microvascular resistance (2.32 ± 0.52 vs. 3.27 ± 0.41 mm Hg cm s(-1), p = 0.001), with no change in average peak velocity (30.6 ± 12.0 vs. 26.6 ± 11.3 cm s(-1), p = 0.59). When autoregulation was disabled, counterpulsation caused an increase in average peak velocity (39.4 ± 10.5 vs. 44.7 ± 17.5 cm s(-1), p = 0.002) that was linearly related with IABP-forward compression wave energy (R(2) = 0.71, p = 0.001). Autoregulation ameliorates the effect of IABP on coronary flow. However, during hyperemia, IABP augments myocardial perfusion, principally due to a diastolic forward compression wave caused by balloon inflation, suggesting IABP would be of greatest benefit when microcirculatory reserve is exhausted.

Assessment of flow velocity in saphenous vein graft using the Doppler guidewire

The purpose of the study is to evaluate flow velocity characteristics in saphenous vein graft for coronary artery bypass grafting, especially in the graftnative vessel anastomotic site. The flow velocity was measured in 13 patients with saphenous vein graft (Group I) using a Doppler guidewire, and values were compared with those in patients who had severe (≧75%, Group II, n=31) or intermediate (<75%, Group III, n=27) coronary artery stenosis. In Group I, the flow velocity data were measured in the graft, in the anastomotic site, and in the native artery distal to the anastomosis, and in Groups II and III data were measured proximal to the stenosis, in the stenosis, and distal to the stenosis. In the saphenous vein graft, average peak velocity (APV) was significantly lower than that proximal to the stenosis. The APV increased significantly from the graft to the anastomotic site (13.3±7.2 → 36.2±15.8 cm/s,p<0.001). The APV in the anastomotic site was significantly lower than that in the stenotic site in Group II (Group II: 100.5±54.7 cm/s,p<0.001), but it was similar to that in Group III (Group III: 58.6±25.2 cm/s). The APV distal to the anastomosis in Group I was normal (22.4±8.0 cm/s), and it was significantly faster than the APV distal to the stenosis in Group II (Group II: 11.7±8.0 cm/s,p <0.001) or Group III (Group III: 15.9±8.2 cm/s,p< 0.05). In Group I, the diameter of saphenous vein graft was significantly larger than that of the native distal artery (4.23±0.85 vs 2.06±0.17 mm,p<0.001), and the Doppler-derived percent cross-sectional area stenosis at the anastomosis showed a significant correlation with the angiographically derived percent crosssectional area stenosis of the graft to the native distal artery (r=0.95,p<0.001). From these results it was thought that the increase of the APV from the graft to the anastomosis was due to caliber change from the graft to the native artery.

Reversibility of coronary endothelial vasomotor dysfunction in idiopathic dilated cardiomyopathy: acute effects of vitamin C

In patients with idiopathic dilated cardiomyopathy, endothelium vasomotor function is disturbed. Increased oxidative stress and the consecutive formation of oxygen free radicals have been implicated as one possibility for this observation, suggesting that nitric oxide (NO) is inactivated by oxygen free radicals. We tested the hypothesis that the antioxidant, vitamin C, may improve endothelial function in idiopathic dilated cardiomyopathy. In 11 patients, the endothelium-dependent vasomotor response of the left anterior descending coronary artery to intracoronary acetylcholine (ACh) infusion (1/2 × 10 −6 mol/L, 1/4 × 10 −5 mol/L; respectively) was determined before and immediately after intravenous infusion of 3 g of vitamin C. Coronary cross-sectional diameter was obtained by quantitative coronary angiography, average peak velocity was measured by an intracoronary Doppler flow wire, and coronary blood flow (CBF) was calculated. Maximum cross-sectional diameter was determined after administration of nitroglycerin. Dose-dependent ACh showed a decrease in cross-sectional diameter (−5% to −7%, p <0.05) and an increase in average peak velocity (+16% to +25%, p <0.05); the CBF was unchanged (+1% to −2%, p = NS). After vitamin C infusion, the cross-sectional diameter increased in a dose-dependent manner from +11% to +15%, the average peak velocity increased from +20% to + 41% (p <0.05), and the CBF increased from +38% to + 82% (p <0.01, p <0.001, respectively). Thus, patients with idiopathic dilated cardiomyopathy had endothelial dysfunction, and administration of vitamin C reversed endothelium-dependent dysfunction.

Renal artery vasomotion: in vivo assessment in the pig with intravascular Doppler.

Intravascular Doppler is widely used for experimental studies in the coronary circulation. We designed this study to assess baseline bloodflow and arteriolar resistance in the porcine renal circulation and to study the vasomotor responses of vasoactive drugs. In anesthesized piglets (n = 15), renal arterial diameter was measured with quantitative angiography and blood flow velocity with a Doppler wire (Cardiometrics). Bloodflow and resistances were calculated at baseline and after injection of vasoactive drugs (isosorbide dinitrate, papaverine). This allowed us to determine the renal bloodflow reserve (the capacity of the kidney to augment basal bloodflow). Injection of isosorbide dinitrate was associated with an increase in average peak velocity of 64% (P < 0.01) and a small (from 4.5 to 4.74, P < 0.01) but significant increase in renal artery diameter, resulting in an increase in bloodflow of 82% (P < 0.01) and a decrease in arteriolar resistance of 46% (P < 0.01). Bloodflow returned to baseline (4.76 +/- 1.48 mL/s) approximately 5 min after isosorbide injection. Average Peak Velocity increased almost twofold after papaverine injection (60 +/- 10 to 108 +/- 24 cm/sec, P < 0.01). There was a significant (P < 0.01) increase in arterial bloodflow of 96% in the right and 79% in the left renal artery after injection of papaverine with a corresponding significant (P < 0.01) decrease in arteriolar resistance of 49% in the right and 44% in the left renal artery. Using a combination of quantitative angiography and intravascular Doppler allows easy measurement of baseline renal blood flow and of the effects of vasodilator drugs on bloodflow and resistance. The results show that a vasodilatator reserve exists in the renal circulation but is less marked than that reported in the coronary circulation.

The pattern of alteration in flow velocity in the recanalized artery is related to left ventricular recovery in patients with acute infarction and successful direct balloon angioplasty

Objectives. We evaluated the relationship between alterations in coronary flow velocity during the acute phase of acute myocardial infarction (AMI) and the recovery of left ventricular wall motion in patients who underwent successful primary angioplasty.Background. The status of the coronary microcirculation is the major determinant of the prognosis of patients who have had successful reperfusion after AMI. Animal studies have shown that dynamic changes in regional flow are associated with the extent of infarction. Evaluation of alterations in coronary flow velocity in infarcted arteries may provide information about microcirculatory damage.Methods. Flow velocity of the distal anterior descending artery was continuously monitored with the use of a Doppler guide wire immediately after recanalization for 18 ± 4 h in 19 patients who underwent successful primary angioplasty after anterior AMI. Subjects were divided into two groups on the basis of the time course of alterations in average peak velocity (APV). Group D consisted of patients who had progressive decreases in APV through the next day (n = 9), and Group I comprised patients with an increase in APV after a transient decline (n = 10). Ejection fraction (EF) and regional wall motion (RWM) were assessed by left ventriculography performed on admission and at discharge.Results. The APV at the end of monitoring was greater in group I than in group D. In group I, EF and RWM were significantly improved at discharge. The change in EF was greater in group I than in group D (17 ± 9% vs. 4 ± 9%, p = 0.007), as was the change in RWM (0.96 ± 0.23 vs. 0.13 ± 0.36 SD/chord, p < 0.0001).Conclusions. The alteration in flow velocity in recanalized infarcted arteries is related to left ventricular recovery. A progressive decrease in velocity after angioplasty implies no reflow, which is associated with a poor recovery of left ventricular function. Reperfusion injury may account in part for this phenomenon.

Coronary collateral blood-flow velocity improves with repeated coronary occlusions during angioplasty in patients with coronary artery disease and systemic hypertension.

Cardiac hypertrophy is associated with numerous alterations in the coronary circulation. To test the hypothesis that, during angioplasty, the coronary collateral blood flow during repetitive coronary occlusions increases more in hypertensives than it does in normotensives. We studied 34 patients (22 normotensives and 12 hypertensives) with stable angina and single-vessel disease undergoing coronary angioplasty during two similar balloon inflations. Each balloon inflation was maintained for 120 s. The coronary blood flow velocity was estimated using the Doppler-flow guide wire, which was positioned distally to the lesion. Flow velocities were recorded before balloon deflation. The average peak velocity increased by 29.0 +/- 14.7 mm/s in the hypertensives and decreased by 9.4 +/- 4.9 mm/s in the normotensives (P < 0.01) during the second balloon inflation, whereas the velocity-time integral increased by 33.1 +/- 19.2 mm and decreased by 14.3 +/- 11.3 mm (P < 0.05), respectively. The ST-segment elevation decreased by 1.13 +/- 1.27 and by 0.17 +/- 0.16 mV, respectively (P = 0.01). The increase in the average peak velocity which occurred during the second balloon inflation was related to the left ventricular mass (r = 0.47, P = 0.004). These results indicate that the coronary collateral blood flow velocity improves with repetitive coronary occlusions during angioplasty in patients with systemic hypertension and that this increase is correlated to the left ventricular mass.

Does coronary flow reserve assessed by blood flow velocity analysis reflect absolute coronary flow reserve?

Doppler guidewire enables us to measure phasic coronary velocity and has been used for the measurement of coronary flow reserve (CFR). Although CFR is usually calculated by the quotient of peak flow velocity during papaverine infusion and flow velocity at rest, this assumption is true only if conduit vessel size is constant. To determine the accuracy of measurement of CFR using average peak velocity (APV) with Doppler guidewire, we investigated the influence of intracoronary papaverine on coronary flow velocity and coronary arterial diameter (CAD) and examined the correlation between CFR derived using APV and that derived using coronary blood flow (CBF) in 26 patients with normal coronary arteries. We measured phasic coronary flow velocity, and performed quantitative coronary angiography in the proximal left coronary artery at control and during 10 mg of intracoronary papaverine. Compared to control value, papaverine induced a significant increase in APV (% increase: 182 +/- 101%; P < 0.001). Papaverine also significantly increased CAD (16 +/- 10%; P < 0.001). Thus, CFR derived from APV was significantly lower than that derived from CBF (2.8 +/- 1.0 vs. 4.0 +/- 1.5, P < 0.001). Although there was a significantly strong positive correlation between these two methods (R2 = 0.83, P < 0.001), there was also considerable variability with regard to predicting one variable from the other. These results suggest the importance of standardizing the conditions in which coronary flow velocity is measured with regard to either controlling or measuring changes in epicardial coronary arterial diameter during changes in distal resistance vessel tone.

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.

919-10 Coronary Hemodynamics After Rotational Atherectomy

The effects of Rotational Athereclomy (PTCRA) and adjunctive balloon angioplasty on the coronary microcirculation were studied with a Doppler-Flow wire in 10 patients (Pts) with single discrete subtotal stenoses in one coronary artery (LAD = 5, RCA = 4, LCX = 1). TIMI-grade Flow was determined for each vessel. Using a cine proyeclor equipped with fra me counter, the number of cineframes required from initiation of the contrast injection 10 opacification of a specified distal landmark were recorded before and after PTCRA. Doppler measurements were made before and after PTCRA and adjunctive balloon. Average Peak Velocity (APV) and Diastolic/Systolic Velocity ratio (DSVR) were measured distal to the lesion. Coronary Flow Reserve (CFRI was assessed with adenosine (24 to 30 JLg i.c.). Estimated coronary blood flow (CBF) and coronary vascular resistances were calculated by standard formulae. Resu/ts: Before PTCRA, all Pts had TIMI-III Flow. Immediately after PTCRA, 2 Pts had TIM I-I Flow, 4 Pts had TIMI-II Flow, and 4 Pts had TIMI-III Flow. In all Pts however, the frame to opacification increased significantly from 49 ± 12 to 118 ± 47 frames (p &lt; 0.05). After the administration of nitroglycerin i.e. (10/10 Pts) and verapamil. i.e. (2/10 Ptsl. TIMI-III Flow was restored in all Pts and the frame to opacification returned to baseline (50 ± 9 frames). The following are the coronary hemodynamics after PTCRA + adjunctive balloon + nitroglycerin + verapamil. Results (mean ± semi):Empty CellBeforeAfterp valueMAP (mmHg)101 ± 594 ± 4nsHR (bts/min)72 ± 274 ± 3nsProx. Lumen Diam (mm)3.44 ± 013.50 ± 0.2nsMinimal Lumen Diam (mm)1.3 ± 012.6 ± 02005APV(cm/s)20 ± 336 ± 50.05DSVR (ratio)1.8 ± 0.815 ± 0.6nsCSF (ml/min)81 ± 14154 ± 180.05CVR (mmhg/ml/min)1.74 ± 0.40.74 ± 0.4005CFR (ratio)1.24 ± 011.6 ± 0.1ns 1) Immediately after PTCRA, the reduction in CBF is likely due to coronary spasm since this spasm was rapidly reversed by of coronary vasodilators. 2) Immediately after PTCRA + adjunctive balloon, there is an increase in APV, estimated CBF and a fall in CVR. Despite this beneficial hemodynamic profile, the CFR remained abnormal. suggesting either ischemic reactive hyperemia or a persistent abnormality in the microcirculatuion.

Assessment of coronary conductance and resistance vessel reactivity in response to nitroglycerin, ergonovine and adenosine: In vivo studies with simultaneous intravascular two-dimensional and Doppler ultrasound

Objectives. The aim of this study was to determine the differential effects of nitroglycerin, ergonovine and adenosine on the resistantce vessels in vivo by using a Doppler-tipped guide wire in combination with an ultrasound imaging catheter.Background. Catheter-based two-dimensional intravascular ultrasound yields images of the coronary arteries from which cross-sectional areas can be measured. Intravascular Doppler ultrasound techniques allow measurement of coronary blood flow velocity. The simultaneous use of the two techniques can yield anatomic and physiologic information on conductance and resistance vessels but has not been tried in the coronary arteries.Methods. In 15 dogs, we studied coronary Bow and vascular reactivity in response to pharmacologic agents using two approaches: 1) a 30-MHz, 4.3F imaging catheter placed alongside a 0.018-in. (0.046 cm) Doppler wire in the circumflex or left anterior descending coronary artery (n = 5); 2) the ultrasound imaging catheter introduced directly over a 0.014-in. (0.036 cm) Doppler wire (n = 10). Vasodilator and vasoconstrictor responses were studied by using intracoronary nitroglycerin (50,100 and 200 μg), ergonovine (200 μg) and adenosine (6 mg).Results. Nitroglycerin caused a dose-dependent increase in epicardial coronary artery cross-sectional area and, to a lesser extent, in average peak flow velocity, resulting in an increase in volumetric coronary blood flow of 39% and 59% at the doses of 100 and 200 μg, respectively. With these doses of nitroglycerin, the decrease in diastolic to systolic velocity ratio and the increased change in cross-sectional area from end-diastole to end-systole suggested an enhanced epicardial coronary artery compliance. With ergonovine, a 12% reduction in epicardial coronary artery cross-sectional area was seen, without a significant change in average peak velocity, resulting in a 15% decrease in volumetric coronary blood flow. Adenosine caused a 270% increase in average peak velocity but no change in epicardial coronary artery cross-sectional area, resulting in a 270% increase in volumetric bood flow.Conclusions. This study demonstrates that nitroglycerin and ergonovine predominantly influence coronary conductance arteries whereas adenosine mainly dilates coronary resistance vessels. These findings also demonstrate that the combined use of a two-dimensional and a Doppler ultrasound transducer within one catheter assembly can provide information on the differential effects of vasoactive agents on the epicardial and microvascular coronary circulation.

Effect of selective angiotensin II receptor antagonism and angiotensin converting enzyme inhibition on the coronary vasculature in vivo. Intravascular two-dimensional and Doppler ultrasound studies.

Although angiotensin converting enzyme (ACE) inhibitors have been reported to increase coronary blood flow, the effect of selective angiotensin II (AT1)-receptor antagonism on the coronary circulation has not been defined. We examined the effects of the AT1-receptor antagonist Losartan (DuP 753, 0.2-3.2 mg/kg) on coronary arteries in vivo in 11 dogs, using a combination of intravascular two-dimensional and Doppler ultrasound. In six dogs, a 30-MHz, 4.3F ultrasound imaging catheter was placed in the midsegment of the circumflex coronary artery to measure cross-sectional area (CSA), and a 0.018-in. Doppler wire was placed alongside to measure coronary flow velocity. At peak effect (1.6 mg/kg), Losartan increased mean coronary CSA from 7.9 +/- 0.5 to 9.5 +/- 0.8 mm2 and average peak velocity (APV) from 32 +/- 10 to 56 +/- 18 cm/sec, resulting in an increase in coronary blood flow from 74 +/- 19 to 151 +/- 36 mL/min. The maximal effect of the ACE inhibitor enalaprilat (5 mg) was an increase in CSA from 7.7 +/- 0.7 to 8.4 +/- 0.8 mm2 and an increase in APV from 36 +/- 10 to 53 +/- 20 cm/sec, with an increase in coronary blood flow from 82 +/- 25 to 122 +/- 41 mL/min. Relative to maximal hyperemia with adenosine (6 mg i.c.), the magnitude of flow increase from baseline was 0.37 with the AT1-receptor antagonist and 0.19 with the ACE inhibitor (p < 0.05). These effects were seen without changes in heart rate or systemic arterial pressure. In an additional five dogs, the ultrasound imaging catheter was introduced directly over a 0.014-in. Doppler wire, and the effects of indomethacin, propranolol, and N omega-nitro-L-arginine methylester (L-NAME) on the vasodilator effect of Losartan (1.6 mg/kg) were examined. Indomethacin and propranolol had no effect on Losartan-induced vasodilation, suggesting that it was not mediated via prostaglandins or beta-adrenoceptors. However, Losartan-induced epicardial vasodilation was partially inhibited by L-NAME, suggesting an action partly dependent on endothelial release of nitric oxide. Thus, these acute studies in anesthetized dogs suggest that inhibition of AT1-receptors in the coronary circulation results in vasodilator responses greater in magnitude than ACE inhibition and partly endothelium dependent. The exact role for AT1-receptors in human coronary physiology and pathology remains to be defined.