Volumetric Coronary Blood Flow 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.

Effect of side branch flow upon physiological indices in coronary artery disease

Recent efforts have demonstrated the ability of computational models to predict fractional flow reserve from coronary artery imaging without the need for invasive instrumentation. However, these models include only larger coronary arteries as smaller side branches cannot be resolved and are therefore neglected. The goal of this study was to evaluate the impact of neglecting the flow to these side branches when computing angiography-derived fractional flow reserve (vFFR) and indices of volumetric coronary artery blood flow. To compensate for the flow to side branches, a leakage function based upon vessel taper (Murray’s Law) was added to a previously developed computational model of coronary blood flow. The augmented model with a leakage function (1Dleaky) and the original model (1D) were then applied to predict FFR as well as inlet and outlet flow in 146 arteries from 80 patients who underwent invasive coronary angiography and FFR measurement. The results show that the leakage function did not significantly change the vFFR but did significantly impact the estimated volumetric flow rate and predicted coronary flow reserve. As both procedures achieved similar predictive accuracy of vFFR despite large differences in coronary blood flow, these results suggest careful consideration of the application of this index for quantitatively assessing flow.

Saline-Induced Coronary Hyperemia: Mechanisms and Effects on Left Ventricular Function.

During thermodilution-based assessment of volumetric coronary blood flow, we observed that intracoronary infusion of saline increased coronary flow. This study aims to quantify the extent and unravel the mechanisms of saline-induced hyperemia. Thirty-three patients were studied; in 24 patients, intracoronary Doppler flow velocity measurements were performed at rest, after intracoronary adenosine, and during increasing infusion rates of saline at room temperature through a dedicated catheter with 4 lateral side holes. In 9 patients, global longitudinal strain and flow propagation velocity were assessed by transthoracic echocardiography during a prolonged intracoronary saline infusion. Taking adenosine-induced maximal hyperemia as reference, intracoronary infusion of saline at rates of 5, 10, 15, and 20 mL/min induced 6%, 46%, 111%, and 112% of maximal hyperemia, respectively. There was a close agreement of maximal saline- and adenosine-induced coronary flow reserve (intraclass correlation coefficient, 0.922; P<0.001). The same infusion rates given through 1 end hole (n=6) or in the contralateral artery (n=6) did not induce a significant increase in flow velocity. Intracoronary saline given on top of an intravenous infusion of adenosine did not further increase flow. Intracoronary saline infusion did not affect blood pressure, systolic, or diastolic left ventricular function. Heart rate decreased by 15% during saline infusion (P=0.021). Intracoronary infusion of saline at room temperature through a dedicated catheter for coronary thermodilution induces steady-state maximal hyperemia at a flow rate ≥15 mL/min. These findings open new possibilities to measure maximal absolute coronary blood flow and minimal microcirculatory resistance.

Relation of Distribution of Coronary Blood Flow Volume to Coronary Artery Dominance

Coronary artery dominance influences the amount and anatomic location of myocardium that is perfused by the left or right coronary circulation. However, it is unknown whether coronary artery dominance also influences the distribution of coronary blood flow volume. The aim of this study was to evaluate volumetric coronary blood flow in 1,322 vessels from 496 patients in the Prediction of Progression of Coronary Artery Disease and Clinical Outcomes Using Vascular Profiling of Endothelial Shear Stress and Arterial Wall Morphology (PREDICTION) study. Patients were divided into 2 groups (right-dominant and left-dominant or balanced circulation). Coronary blood flow volume was calculated by coronary segment volume measurement using angiography and intravascular ultrasound and the contrast transit time through the segment. Coronary blood flow in the left circumflex coronary artery was significantly higher in left-dominant or balanced circulation than in right-dominant circulation (113 ± 43 vs 72 ± 37 ml/min, p <0.001), whereas flow in the right coronary artery was significantly lower in left-dominant or balanced circulation than in right-dominant circulation (56 ± 40 vs 113 ± 49 ml/min, p= 0.003). There was no significant difference in the left anterior descending coronary artery. In conclusion, coronary artery dominance has an impact on coronary blood flow volume in the left circumflex and right coronary arteries but not in the left anterior descending coronary artery. These findings suggest that the extent of myocardial perfusion area is associated with coronary blood flow volume.

Haemodynamic effects, safety, and tolerability of haemoglobin-based oxygen carrier-201 in patients undergoing PCI for CAD

Haemoglobin based oxygen carriers (HBOCs) are considered in the treatment of patients with acute coronary syndromes (ACS) undergoing percutaneous coronary intervention (PCI). In light of their potential vasopressor and colloidal properties, their effect on coronary physiology, safety and tolerability needs to be established. In this phase II pilot trial, 45 patients were randomly assigned, (1:1:1) to double blind treatment with a 30 minute intravenous (IV) infusion of either 15 or 30 g of HBOC-201, compared to an equivalent volume of non-oxygen carrier colloid control. Systemic, pulmonary, and coronary haemodynamics were studied during this infusion period. IV HBOC-201 administration produced an increase in systolic blood pressure (SBP), pulmonary capillary wedge pressure and calculated systemic vascular resistance (SVR) and a concomitant decrease in cardiac output (CO); there was a decrease in mixed venous saturation (SVO2) following IV HBOC-201. The left ventricular stroke work index (LVSWI) was not altered by HBOC-201 treatment. Of note, no coronary vasoconstriction was observed, nor were there significant changes in resting average peak velocity (APV), coronary-artery diameter, volumetric coronary blood flow, or coronary vascular resistance. The percentage of patients with adverse events did not differ between the HBOC-201 treated and control groups (76% vs. 63%, respectively, P=0.49). Seven serious adverse events (SAE) occurred in six patients in the treatment group and two in two patients in the control group. Only one SAE (hypertension) was judged HBOC-201 related. Patients in both the HBOC-201 and control group had a similar incidence of increased liver alanine transaminase (31% vs 31%, respectively, NS); 10% of the patients in the HBOC-201 group had increases greater than three times the upper limit of normal. Differential increases were noticed in some inflammatory markers (IL-6, CRP) 18-24 hours after infusion between the HBOC-201 arms and the control group. No compromise in the coronary blood flow or LVSWI was observed despite HBOC-201's known vasoactive effects. One SAE was adjudicated as "drug related" and fully resolved. The clinical relevance of the differential rise in certain biochemical markers and the adverse effects of plasma haemoglobin in the context of ACS needs further investigation.

Regional volumetric coronary blood flow measurement by digital angiography: In vivo validation 1

Rationale and objectives There are well-known limitations to the use of visual estimation to assess the severity of coronary artery disease and luminal stenosis. This is especially true in the case of an intermediate coronary lesion (30%–70% diameter stenosis), where coronary arteriography is very limited in distinguishing ischemia-producing intermediate coronary lesions from non-ischemia-producing ones. For this reason, a functional measure of stenosis severity is desirable. The goal of this study is to validate a video densitometry technique for quantitative assessment of regional volumetric coronary blood flow. Materials and methods Coronary arteriography was performed in eight swine (body weight, 25–50 kg) after power injection of contrast material into the left main coronary artery. Phase-matched subtracted images were used to quantify regional coronary blood flow using a video densitometry technique. The in vivo regional flow measurements were validated using a transit time ultrasound flow probe. Results In 44 measurements, the ultrasound (Q US) and video densitometry (Q VD) regional flow measurements were related by Q VD = 0.98 Q US + 0.11 mL/min ( r = 0.98). The results of mean regional coronary blood flow measurements for repeated coronary arteriograms of the first (Q VD1) and second (Q VD2) measured flows were related by Q VD1 = 1.04 Q VD2 + 0.05 mL/min ( r = 0.97). Conclusions A video densitometry technique for quantification of regional coronary blood flow was validated using a swine animal model. The results demonstrated the feasibility and potential utility of the video densitometry technique for accurate measurement of regional coronary blood flow, in vivo. This study provides an angiographic method that can potentially be used to evaluate intermediate coronary lesions during routine coronary arteriography.

Altered coronary flow properties in diffuse coronary artery ectasia

Objectives The purpose of this study was to investigate coronary blood flow properties in patients with diffuse coronary artery ectasia (CAE) associated with exercise-induced myocardial ischemia. Methods Seventeen patients with diffuse CAE and without coexisting coronary artery stenosis were enrolled in the study (CAE group). CAE was defined as luminal dilatation 1.5 to 2 times that of the adjacent normal coronary artery segment or the diameter of the corresponding coronary artery of the control group when there was no normal segment. The age- and sex-matched control group (n = 20) comprised patients with normal epicardial coronary arteries. Coronary blood flow velocities were obtained invasively by use of Doppler scanning flow wire. Coronary flow reserve (CFR) was measured by administration of intracoronary papaverine as the hyperemic stimulus. Volumetric coronary blood flow was estimated by multiplying the velocity time integral of coronary blood flow with the cross-sectional area of the coronary artery and the heart rate. Results Fifteen patients with CAE, but none of the patients in the control group, had electrocardiographic signs of myocardial ischemia at peak exercise on ergometry. Baseline average peak velocities (APVs) of coronary blood flow were similar in the 2 groups. Peak hyperemic APVs of coronary blood flow were lower in the CAE group than in the control group (17.5 ± 7.4 cm/s vs 41.5 ± 12.6 cm/s, respectively, P < .001). Volumetric coronary blood flow was significantly higher in the CAE group than in the control group, both at rest and at hyperemia (146.3 ± 71.2 cm 3/min vs 45.1 ± 16.1 cm 3/min, respectively, P < .001, and 202 ± 87.3 cm 3/min vs 104.1 ± 37.6 cm 3/min, respectively, P < .003). The mean CFR of the CAE group was significantly reduced compared with that of the control group (1.51 ± 0.31 vs 2.67 ± 0.52, respectively, P < .001). Conclusions The CFR is significantly reduced in patients with diffuse CAE compared to a matched control group. Although volumetric coronary blood flow is significantly higher in CAE, microcirculatory dysfunction that is reflected as depressed CFR may be the underlying cause of exercise-induced myocardial ischemia. (Am Heart J 2003;145:66-72.)

Coronary endothelial function in hyperhomocysteinemia: improvement after treatment with folic acid and cobalamin in patients with coronary artery disease

ObjectivesWe evaluated the effect of therapy with folic acid and cobalamin on coronary endothelial function, expressed as a change in volumetric coronary blood flow (CBF), in hyperhomocysteinemic patients with coronary artery disease (CAD). BackgroundHyperhomocysteinemia is an independent risk factor for CAD. The mechanism responsible for this increased risk is unclear, but it is generally assumed that hyperhomocysteinemia causes endothelial dysfunction. It is unknown whether lowering plasma homocysteine levels with folic acid and cobalamin improves coronary endothelial function in patients with hyperhomocysteinemia and symptomatic CAD. MethodsFifteen patients scheduled for elective percutaneous transluminal coronary angioplasty (PTCA) with plasma homocysteine levels of ≥16 μmol/l were randomized for six months of treatment with folic acid 5 mg and cobalamin 400 μg daily or placebo. Coronary endothelial function was evaluated in a non-PTCA vessel using acetylcholine infusion in dosages of 10−8 M, 10−7 M, and 10−6 M. Endothelium- dependent CBF is determined using intracoronary Doppler velocity and quantitative coronary angiography at baseline and after six months. ResultsIn the folic acid/cobalamin treated group, CBF increased after acetylcholine infusion with 96% (standard deviation 54; 95% confidence interval [CI]: 44% to 154%) compared with a decrease of 16% (standard deviation 35; 95% CI: −20% to +30%) of the CBF in the placebo-treated group (p < 0.005). ConclusionsThis is the first prospective randomized placebo-controlled intervention study evaluating coronary endothelial function in hyperhomocysteinemic patients with CAD. Our results suggest that coronary endothelial function improves after treatment with folic acid and cobalamin.

Relation Between Vascular Resistance and Intimal Thickness in Patients with Coronary Artery Disease

Background:The intimal thickening of coronary artery was understood as an early process in the beginning of atherosclerosis. However, the implication of intimal thickening as a morphologic change of coronary artery disease, on the coronary vascular hemodynamics has not been explored. Methods:To evaluate the effect of intimal thickening on the coronary vascular hemodynamics, we studied the extent of intimal thickening on intravascular ultrasound (IVUS) and the coronary vascular flow and resistance by using Doppler wire in left anterior descending coronary arteries after successful intervention in 40 patients (29 males, mean age 55±9 years) with coronary artery disease. Mean intimal index and mean lumen cross sectional area were determined by IVUS and coronary flow average peak velocity was obtained by using Doppler wire before and after intracoronary adenosine in distal artery to the stenosis. Coronary flow velocity reserve (CFR), volumetric coronary blood flow (CBF) and coronary vascular resistance index (CVRI) were calculated. Hyperemic pressureto-flow ratio (hyperemic mean aortic pressure/hyperemic volumetric coronary blood flow), ie, an index of minimal coronary vascular resistance (mCVR), was further derived. Results:Intimal index (mean 20.0± 8.3%) was significantly correlated with CVRI (mean 0.33±0.14, r=0.37, p=0.02) and mCVR (mean 0.81± 0.40 mmHg/ml/min, r=0.36, p=0.02). However, there was no correlation with CBF and CFR. Conclusion: The CVRI and mCVR, the indices coronary microvascular resistance, were significantly related to the degree of intimal thickness of coronary artery. The extent of intimal thickness of coronary artery on IVUS study may be related to microvascular integrity. (Korean Circulation J 2001;31(1):54-62)

Absolute volumetric coronary blood flow measurement with digital subtraction angiography.

The problems associated with visual interpretation of coronary arteriograms have been well-documented. There is a need for more physiologic means of assessing coronary artery stenosis during routine coronary arteriography. Volumetric coronary blood flow assessed as a function of time can be a valuable aid in the analysis of functional significance of arterial obstruction. A volumetric coronary blood flow measurement technique was investigated in a swine animal model using phase matched temporal subtraction images. The left anterior descending (LAD) coronary artery of swine animal models were instrumented with an ultrasound flow probe (US) and a vascular occluder producing stenosis. Contrast material injections (2-4 ml/sec for 3 sec) were made into the left coronary ostium during image acquisition. Phase-matched temporal subtraction (DSA) images were used to measure volumetric coronary blood flow in the LAD. In addition, a technique for automatic estimation of iodine calibration slope was also investigated. In 49 independent comparisons, the mean coronary blood flow (FPA) correlated extremely well with the mean US flow (FPA = 0.92US + 1.42 ml/min, r = 0.99, standard error of estimate (SEE) = 4.32 ml/min). Further more, the automatic iodine calibration technique was shown to be very accurate. In conclusion, accurate volumetric coronary blood flow measurements can be made before the onset of significant changes in coronary blood flow due to contrast injection.

Testosterone induces dilation of canine coronary conductance and resistance arteries in vivo.

Although estrogens have been shown to be vasoactive hormones, the vascular effects of testosterone are not well defined. Like estrogen, testosterone causes relaxation of isolated rabbit coronary arterial segments. We examined the vasodilator effects of testosterone in vivo in the coronary circulation and the potential mechanisms of its actions. Using simultaneous intravascular two-dimensional and Doppler ultrasound, we examined the effect of intracoronary testosterone in coronary conductance and resistance arteries in 10 anesthetized dogs (5 male, 5 female). We also assessed the contribution of NO, prostaglandins, ATP-sensitive K+ channels, and classic estrogen receptors to testosterone-induced vasodilation. Testosterone induced a significant increase in cross-sectional area, average coronary peak flow velocity, and calculated volumetric coronary blood flow at the 0.1 and 1 mumol/L concentrations. This effect was independent of sex. Pretreatment with N omega-nitro-L-arginine methyl ester to block NO synthesis decreased testosterone-induced increase in cross-sectional area, average coronary peak flow velocity, and coronary blood flow. Pretreatment with glybenclamide to assess the role of ATP-sensitive K+ channels did not influence testosterone-induced dilation in epicardial arteries but did attenuate its effect in the microcirculation. Pretreatment with indomethacin or the classic estrogen-receptor antagonist ICI 182,780 did not alter testosterone-induced changes. Short-term administration of testosterone induces a sex-independent vasodilation in coronary conductance and resistance arteries in vivo. Acute testosterone-induced coronary vasodilation of epicardial and resistance vessels is mediated in part by endothelium-derived NO. ATP-sensitive K+ channels appear to play a role in the vasodilatory effect of testosterone in resistance arteries.

Quantification of Volumetric Coronary Blood Flow With Dual-Energy Digital Subtraction Angiography

As a solution to the well-documented problems associated with visual interpretation of coronary arteriograms, more physiological methods of assessing coronary artery stenosis are being investigated. Volumetric coronary blood flow (BF) can be a valuable aid in the analysis of functional significance of arterial obstruction. The left anterior descending coronary artery (LAD) of 15 anesthetized pigs (40 to 50 kg) was dissected free from the epicardium in its proximal portion, and a transmit-time ultrasound flow probe of the appropriate size was applied. A vascular occluder was positioned distal to the flow probe for flow adjustments. Contrast injections (2 to 4 mL/s for 3 seconds) were made into the left main coronary artery during image acquisition with a motion-immune dual-energy digital subtraction angiography (DE DSA) system. Tissue-suppressed energy-subtracted images were used to generate time-density curves. BF measurements were made in the LAD vascular bed with use of the time-density curve, with consideration that blood was momentarily replaced with contrast during the injection. In 19 comparisons, the mean BF, measured with the use of DE DSA, correlated extremely well with the mean ultrasound flow (DE DSA=0.90 ultrasound+3.10 mL/min, r=.96). Also, contrast injection increased the BF by an average of only 15% during the image-acquisition time interval. Accurate BF measurements can be made with motion-immune DE DSA. The BF measurements can be completed before the onset of significant changes in BF due to contrast injection. Furthermore, it is possible to make the BF measurements during routine coronary arteriography.

Influence of Intimal Thickening on Coronary Blood Flow Responses in Orthotopic Heart Transplant Recipients

Intravascular ultrasound imaging detects epicardial intimal thickening in the majority of heart transplant recipients with angiographically normal epicardial coronary arteries. Although coronary artery vasoreactivity is abnormal after cardiac transplantation, intimal thickening does not appear to affect conduit vessel responses. However, the effect of intimal thickening on both conduit and resistance vessel responses, as measured by changes in volumetric coronary blood flow (CBF), is unknown. Epicardial coronary artery conductance and microvascular resistance vessel responses were studied after intracoronary adenosine and nitroglycerin administration in 36 orthotopic heart transplant recipients 1 month to 7 years after transplantation. Sequentially measured coronary flow average peak velocity ([APV, cm/s] 0.018 in Doppler guide wire) and epicardial luminal cross-sectional area ([CSA, mm2] 4.3F 30-MHz ultrasound catheter) data were obtained at baseline and during peak hyperemia after administration of 12 to 18 micrograms IC adenosine and 150 to 200 micrograms IC nitroglycerin. Volumetric CBF (mL/min) was calculated as CBF = APV (cm/s) x CSA (mm2) x 60 seconds/1 min x 1 cm2/100 mm2 x 0.5. Measurements were made from a discrete position in the proximal left anterior descending (LAD) artery (n = 22), mid-LAD artery (n = 7), proximal circumflex artery (n = 6), and proximal right coronary artery (n = 1). Intimal thickening was present in 19 of 32 patients (60%). Both adenosine and nitroglycerin increased APV (from 18.9 +/- 4.9 to 56.0 +/- 11.5 cm/s for adenosine and from 20.2 +/- 5.3 to 49.1 +/- 11.5 cm/s for nitroglycerin; both P < .05). Coronary flow velocity reserve was significantly higher for adenosine compared with nitroglycerin (3.1 +/- 0.6 versus 2.5 +/- 0.7, respectively; P < .001). Epicardial luminal CSA was unchanged during adenosine hyperemia compared with baseline (17.4 +/- 3.8 versus 17.3 +/- 4.0 mm2, respectively; P = NS) but was significantly greater during nitroglycerin hyperemia compared with baseline (18.7 +/- 3.8 versus 17.3 +/- 4.0 mm2, 6.2 +/- 3.6% change; P < .05). Baseline CBF was similar before drug administration. Hyperemic adenosine and nitroglycerin CBF responses (297 +/- 99 and 276 +/- 87 mL/min, respectively; P = NS) and CBF reserve (3.0 +/- 0.7 and 2.7 +/- 0.7, respectively; P = NS) were not significantly different. Importantly, intimal thickening did not diminish resting or hyperemic APV, coronary flow velocity reserve, luminal CSA, CBF, or CBF reserve responses. In this study of angiographically normal heart transplant recipients, epicardial intimal thickening does not diminish conduit and resistance vessel responses during endothelial-independent vasodilator administration.

704-5 Adenosine Dilates Conductance and Resistance Vessels in Denervated Human Coronary Arteries and is more Potent than Dipyridamole

Adenosine and dipyridamole are coronary vasodilators who act primarily on resistance vessels. Vascular response in the denervated heart are not well understood. To examine this question, coronary hemodynamic changes in response to standard vasodilators were assessed in eleven heart transplanted patients using simultaneously a 4.3 F, 30 MHz ultrasound imaging catheter (CVIS) over a 0.014” Doppler guidewire (Cardiometries). Measures of average peak velocity (APV) and cross-sectional area (CSA) were used to calculate volumetric flow during intravenous infusions of the endothelium independent vasodilators adenosine (140 μg/kg/min over 4 minutes) and dipyridamole (140 μg/kg/min over 4 minutes). Volumetric coronary blood flow (CBF) was calculated using the previously validated relationship CBF = 0.47 × CSA × APV. Flow reserve was assessed as a ratio of maximal pharmacologicallyinduced flow to steady baseline flow prior to infusion. Increase in coronary average peak velocity (261.9 vs. 194.6%, p = 0.005), lumenal area (111.8 vs 104.2%, P = 0.01). peak volumetric blood flow (515.8 vs. 317.2 cc/min, p = 0.007) and coronary flow reserve (2.93 ± 0.79 vs. 1.99 ± 0.56, p &lt; 0.001) were higher with adenosine compared to dipyridamole. Epicardial dilation was only seen with adenosine administration (p = 0.01). Both agents caused similar decreases in systemic blood pressure and little change in heart rate. Transplant recipients appear to have diminished flow velocity and flow reserve in response to endothelium-independent agents. Adenosine appears to be a more potent coronary vasodilator than dipyridamole in denervated human transplant subjects at both the epicardial and microvascular level at standard doses. Adenosine's effects in the conductance vasculature may be unique to the transplant recipient where denervation is present.

739-2 Intraaortic Balloon Pumping Augments Distal Coronary Blood Flow Provided Through Perfusion Balloon Catheters During High Risk PTCA

Perfusion balloon catheters (PBC) utilized for PTCA deliver antegrade distal blood flow during balloon inflation, limiting ischemia and permitting potentially hazardous or prolonged dilatations useful in management of high risk procedures. Distal flow is passive via the catheter lumen and determined in part by perfusion pressure, which may limit distal blood flow delivery, especially with lower profile PBC. Intraaortic balloon pumping (IABP) has been shown to increase diastolic pressure and blood flow in non-stenosed coronary arteries. To quantitate whether distal blood flow delivery via PBC could be augmented using intraaortic balloon pumping (IABP), we measured distal coronary flow velocity using an 0.018” Doppler-tipped guidewire placed alongside an inflated PBC (Flowtrack 40; ACS, Inc) during PTCA in 5 patients (4 LAD, 1 LCX) during high risk PTCA. Distal average peak velocity (APV, cm/s). systolic peak velocity (SPV, cm/s) and diastolic peak velocity(DPV, cm/s)were quantitated and volumetric coronary blood flow (CBF, ml/min) derived (APV × 0.5 × distal angiographic cross sectional area × 60) during PBC inflation without and with IABP. Results (means ± SD):Empty CellAPVSPVDPVDistal CBFIABP OFF10.1 ± 38.1 ± 215.5 ± 715.7 ± 6IABP ON12.3 ± 47.6 ± 320.3 ± 719.0 ± 7p value0.010.460.0010.009 While not affecting SPV, IABP increased APV, DPV and CBF measured distal to the inflated PBC by means of 22%, 35% and 22%, respectively. We conclude that use of IABP can significantly augment distal blood flow delivery by PBC during PTCA. This augmented distal perfusion may provide a mechanism to further reduce ischemia and increase the safety of high risk PTCA.

901-116 Coronary Vascular Relaxation Induced by Testosterone In Vivo is Gender Independent

To assess coronary vasoreactive response of testosterone and its relation to gender, we examined the effect of intracoronary testosterone (10 -10 to 10 -6 M) on epicardial and resistance coronary arteries in vivo in both male (5) and female (5) dogs. Changes in average peak flow velocity (APV) were assessed using a 0.014” Doppler guidewire (Cardiometrics), and epicardial cross-sectional area (CSA) was measured using a 4.3 F, 30 MHz ultrasound imaging catheter (CVIS). Guidewire and imaging catheter were positioned in the left circumflex artery. Testosterone induced a significant increase in both CSA, APV and calculated volumetric coronary blood flow (CBFI at the 10 -7 and 10 -6 M concentrations (CSA: 15.2 ± 10.2% increase at 10 -6 M (p = 0.05); APV: 36.4 ± 12.8 increase at 10 -7 (p &lt; 0,01) and 73.8 ± 66.8% increase at 10- 6 M (p = 0.004); CBF: 205% increase at 10 -6 M (p = 0.04)). Coronary vasorelaxation was equal in both males and females. No significant changes in heart rate or systemic pressure were noted. We conclude that acute testosterone administration induces epicardial and resistance coronary artery dilation in vivo and coronary vasorelaxation is independent of gender.

Measurement of volumetric coronary blood flow by simultaneous intravascular two-dimensional and Doppler ultrasound: Validation in an animal model

We examined the accuracy and feasibility of using simultaneous intracoronary Doppler and two-dimensional (2D) ultrasound imaging in the measurement of volumetric coronary blood flow (CBF). A femoral artery-to-circumflex coronary artery shunt was created in four dogs with tubing that incorporated an in-line transit-time ultrasound (TTU) flow probe. A 2D ultrasound catheter was introduced over a 0.014-inch Doppler guide wire into the circumflex artery with the guide wire tip positioned 2 cm beyond the imaging catheter tip. Cross-sectional area (CSA) and average peak velocity (APV) were recorded. CBF was determined from the previously validated relation CBF = CSA × 0.5 APV and the adjusted measurement formula CBF = CSA × 0.47 APV. Within the 119 measurements made, TTU CBF varied from 31 to 385 ml/min. An excellent correlation was found between 2D/Doppler-derived and TTU CBF with both constants; measurement agreement was improved and bias minimal with the 0.47 constant (slope = 0.9997; r = 0.99; p < 0.0001; SEE = −6.7 ± 8.6). We conclude that simultaneous 2D and Doppler ultrasound yields accurate estimates of volumetric CBF.

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.

Measurement of volumetric coronary blood flow with a doppler catheter: Validation in an animal model

Although Doppler catheter recordings are used to determine coronary flow velocity, their accuracy in the estimation of volumetric blood flow has not been validated. To address this issue, Doppler-derived coronary flow was measured in a canine model and compared with that obtained by means of an electromagnetic flowmeter. A carotid artery-to-circumflex coronary artery shunt was created in six dogs with tubing that incorporated an inline electromagnetic flow device. The circumflex artery was occlusively cannulated by means of a rigid metal stent of known internal diameter, which was placed 2 cm into the vessel, and flow was measured in the stent region by means of a 3F Doppler catheter. Analysis of Doppler shift signals was performed by means of a zero-crossing detector (ZCD) and an off-line fast-Fourier transformation (FFT) system. Flow derived from peak FFT velocities corresponded closely to electromagnetic flow (slope 1.09, r = 0.93), whereas mean FFT and ZCD velocities underestimated electromagnetic flow (with slopes of 0.47 and 0.46, respectively) despite a close correlation ( r = 0.92,0.94). Thus FFT analysis of the Doppler signal with determination of peak velocity gives the most accurate representation of flow, whereas measurements based on ZCD mean velocities may significantly underestimate coronary flow.