Time-averaged Peak Velocity Research Articles

Volumetric blood flow measurement using Doppler ultrasound: concerns about the technique.

Volumetric blood flow measurement using Doppler ultrasound: concerns about the technique.

Packed red blood cell transfusion (PRBC) attenuates intestinal blood flow responses to feedings in pre-term neonates with normalization at 24 hours

Objective: To determine whether packed red blood cell (PRBC) transfusion affects post-prandial superior mesenteric artery blood flow velocities (SMA BFVs) in very-low birth weight (VLBW) neonates and if so, at what time point after transfusion restoration of previous SMA BFV patterns occurs.Design/Methods: VLBW pre-term neonates, older than 14 days and tolerating bolus enteral feedings administered every 3 h were enrolled in this prospective observational study. Pulsed Doppler ultrasound was used to measure pre- and post-prandial (at 45 min) time-averaged mean, peak and end diastolic velocities (TAMV, PSV, EDV) immediately before and after 15 ml/kg of PRBC transfusion was given over 3 h; patent ductus arteriosus (PDA) status was also evaluated. Subsequent pre- and post-prandial SMA BFVs were recorded 24 and 48 h after the transfusion.Results: Pre- and post-prandial measurements were obtained for 21 out of 25 enrolled infants. Post-prandial SMA BFVs were attenuated during the feedings immediately after transfusion; at 24 and 48 h after transfusion, changes in post-prandial SMA BFVs were similar to those measured prior to transfusion; the presence of the PDA did not affect results.Conclusions: PRBC transfusion blunted SMA BFV responses to feedings immediately after the transfusion with normalization observed 24 h post-transfusion.

Assessment of intracranial blood flow velocities using a computer controlled vasoactive stimulus: A comparison between phase contrast magnetic resonance angiography and transcranial doppler ultrasonography

To compare measurements of blood flow velocity (BFV) and BFV changes in the middle cerebral arteries (MCA) acquired from phase contrast magnetic resonance angiography (PCMRA) and transcranial Doppler ultrasound (TCD) during controlled manipulation of end-tidal partial pressure of carbon dioxide (PetCO2 ). In vivo TCD and PCMRA velocity data from the M1 segment in the MCA of nine healthy adult volunteers were acquired during precise targeting of PetCO2 induced by a computer-controlled gas delivery system. Doppler spectra and phase contrast data were processed into time-averaged peak-velocity (TAPV) values for comparison. Changes in velocity between baseline and hypercapnia were analyzed in terms of velocity-based cerebrovascular reactivity (CVR). Good correlation between the pairs of velocity measurements acquired from the two modalities were found (ρ = 0.81), but Bland-Altman analysis indicates a significant bias error. There was relatively weak agreement between the pairs of computed CVR values (ρ = -0.26). Under precise PetCO2 control, PCMRA proves to be more consistent than TCD. Despite issues with variability, TCD is qualitatively comparable to PCMRA measures of velocity in the MCA. However, PCMRA velocity results are better suited for analyses that require quantitative values, such as CVR.

Anterograde and retrograde blood velocity profiles in the intact human cardiovascular system

Current assessments of the effects of shear patterns on vascular function assume that a parabolic velocity profile is always present. Any substantial deviation in the profile away from this may result in misinterpretation of the importance that shear patterns have on vascular function. The present investigation tested the hypothesis that anterograde and retrograde blood flow would have a parabolic velocity profile at rest, during cold pressor test and exercise. Eight healthy subjects completed a cold pressor test and a graded knee-extension exercise test. Doppler ultrasound was used to determine time-averaged mean velocity (V(mean)) and time-averaged peak velocity (V(peak)) for both anterograde and retrograde flow in the femoral artery (FA) and brachial artery (BA). The V(mean)/V(peak) ratio was used to interpret the shape of the blood velocity profile (parabolic, V(mean)/V(peak) = 0.5; plug-like, V(mean)/V(peak) = 1.0). At rest, BA and FA V(mean)/V(peak) ratios of anterograde and retrograde flow were not significantly different from 0.5. During cold pressor test, anterograde V(mean)/V(peak) in the BA (0.56 ± 0.02) and FA (0.58 ± 0.03) were significantly greater than 0.5. During peak exercise, the V(mean)/V(peak) ratio of anterograde flow in the FA (0.53 ± 0.04) was not significantly different from 0.5. In all conditions, the retrograde V(mean)/V(peak) ratio was lower than anterograde. These data demonstrate that blood flow through two different conduit arteries during two different physiological stressors maintains a velocity profile that resembles a slightly blunted parabolic velocity profile.

Effects of a Patent Ductus Arteriosus on Postprandial Intestinal Blood Flow in Extremely Low Birth Weight (ELBW) Neonates

Background: Patent ductus arteriosus (PDA) affects superior mesenteric artery blood flow velocity (SMA BFV) in fasting neonates. Recently, it has been reported that PDA affects postprandial mesenteric perfusion in premature baboons; however, the effects of PDA on postprandial mesenteric perfusion in preterm neonates have not been evaluated. Aims: To determine whether PDA affects postprandial SMA BFV in ELBW neonates. Methods: Appropriate for gestational age, ELBW preterm neonates, tolerating bolus enteral feedings were enrolled in this prospective observational study. Pulsed Doppler was used to measure preprandial and postprandial (at 30-min and 60-min) time-averaged mean, peak and end diastolic velocities (TAMV, PSV, EDV) once during the day of life 5 to 7; at the same time, PDA size was estimated using the PDA:left pulmonary artery (LPA) ratio : 0.5 (i.e., moderate/large PDA) and < 0.5 (i.e., small/no PDA). Mean values across time were graphed to illustrate relative changes in moderate/large and no/small PDA groups. Repeated measures ANOVA was used to compare SMA BFV changes between the groups from preprandial to 30-min and 60-min postprandial for each type of measured velocity (TAMV, PSV, EDV). Results: Of the38 infants studied, 16 were in the no/small PDA group; 22 were in the moderate/large PDA group. Postprandial TAMV, PSV and EDV were not different between these two groups ( p values were 0.798, 0.315 and 0.59, respectively). Conclusions: Changes in postprandial mesenteric blood velocity did not differ between infants with no/small PDA versus moderate/large PDA in this study's cohort of 38 ELBW neonates.

363 Probiotics Supplementation Increases Intestinal Blood Flow in Extremely Low Birth Weight (ELBW) Neonates

Background: Proposed benefits of probiotics supplementation are multiple; recently, vasoactive properties of trace amines, produced by probiotics, have been shown to affect mesenteric vasculature in animal models. The effects of probiotics on intestinal blood flow have not yet been described. Aims: To determine whether probiotics supplementation affects intestinal blood flow velocity in ELBW neonates. Methods: In this randomized, double-blind, placebo-controlled study probiotics (500 M CFU of Lactobacillus rhamnosus and 500 million CFU of Bifidobacterium infantis) were added to the first enteral feeding and continued until discharge or 34 weeks postmenstrual age. Pulsed Doppler measured preprandial and postprandial (at 30 and 60 min) time-averaged mean, peak and end diastolic velocities (TAMV, PSV, EDV) during second week of life after 7 days of probiotics supplementation. Mean values across time were graphed for probiotics and control groups. The percent change from preprandial to 60 min post was compared by t-test, for each measurement method. Results: Thirty-one infants were studied, 15 randomized to probiotics and 16 to placebo. Postprandial TAMV were increased significantly in probiotics group (p = 0.048), with PSV and EDV showing a trend. There were no significant differences between groups in mean birth weight, gestational age, the time of the study, volume and type of feedings (p > 0.05). The percent of infants undergoing phototherapy, receiving caffeine or being diagnosed with patent ductus arteriosus was similar between groups (p > 0.05). Conclusions: Probiotics administration significantly increases intestinal blood flow in ELBW preterm neonates when compared to placebo group.

Effect of graft adaptation of the internal mammary artery on longitudinal phasic blood flow velocity characteristics after surgery

Left internal mammary artery (LIMA) bypass conduits undergo gradual longitudinal flow transition from the proximal to distal segments, and the diastolic/systolic (D/S) ratios of the flow indices can diagnose graft patency. However, the influence of graft adaptation on this has not been studied. We examined 46 patients with LIMA graft to the left anterior descending artery using a Doppler-tipped guidewire in the proximal, middle, and distal segments; 34 had patent LIMAs (group A: new LIMAs; <1month postoperatively; n=22 and group B: old LIMAs; ≥1month postoperatively; n=12), and 12 had new LIMAs with distal stenosis (group C). In diastole, the time-averaged peak velocities, maximum peak velocities, and velocity-time integrals in each segment were significantly greater in group A than in groups B or C; however, in systole, they did not differ significantly among the three groups. The D/S ratios of the indices in all segments in group A were significantly greater than those in groups B or C; however, they did not differ between groups B and C in any of the segments. Graft adaptation of a patent LIMA, itself, affects the longitudinal flow transition pattern. The D/S ratio of the three indices in the patent old LIMAs did not differ from those in the LIMAs with distal stenosis early after surgery. The timing of LIMA flow assessment must be considered during assessment of the graft patency from the flow velocity patterns.

Advantage of Right Ventricular Outflow Tract Pacing on Cardiac Function and Coronary Circulation in Comparison with Right Ventricular Apex Pacing

The purpose of this study was to investigate the acute effect of right ventricular outflow tract (RVOT) pacing and right ventricular apex (RVA) pacing on synchronous ventricular activation and coronary flow dynamics. We enrolled 20 consecutive patients who underwent electrophysiologic study. Echocardiographic study including two-dimensional tissue tracking imaging and Doppler guide wire examination was performed during RVOT pacing and RVA pacing. The improvement of left ventricular radial dyssynchrony (99 ± 12 ms vs. 142 ± 16 ms, P < .001), time-averaged peak velocities of coronary blood flow (54 ± 18 cm/s vs. 47 ± 17 cm/s, P = .007), and coronary microvascular resistance index (2.0 ± 0.8 vs. 2.4 ± 1.1, P = .028) was observed with RVOT pacing compared with RVA pacing. RVOT pacing might provide favorable effects on the left ventricular function and coronary flow dynamics over RVA pacing.

Effect of compression stockings on venous blood velocity and blood flow

The effects of graduated compression stockings (GCS) on venous blood velocity have not been established. In healthy subjects, most investigations showed no effect on blood velocity, but mixed results have been reported. In this investigation we to test the hypothesis that popliteal blood velocity is increased by properly fitted GCS. Time average peak velocity in the popliteal vein, as well as time average mean velocity, vein diameter and mean volumetric flow were measured by pulsed wave Doppler ultrasound in 25 healthy male volunteers without compression stockings and repeated with fitted thigh-length compression stockings. Measurements were obtained while supine and while sitting at rest and during ankle exercise. Thigh-length GCS did not increase popliteal vein blood velocity, diameter, or volumetric blood flow while supine or sitting, with or without ankle exercise.

Ankle exercise and venous blood velocity

Ankle exercise increases venous blood velocity while supine, but the effect of ankle exercise on venous blood velocity while sitting is not known. In this investigation, we test the hypothesis that venous blood velocity can be increased while sitting by repetitive dorsiflexion of the foot. Time-averaged peak velocity (TAPV) in the popliteal vein of 20 healthy male volunteers was measured by pulsed Doppler ultrasound at rest and during ankle exercise in the supine and sitting positions. Right popliteal vein TAPV while supine at rest was 11 cm/second (sec) (95% confidence interval [CI] =9-13 cm/sec) and with ankle exercise it increased to 24 cm/sec (95% CI =20-28 cm/sec) (p<0.0001). With sitting at rest, right popliteal vein blood TAPV decreased from 11 cm/sec to 3 cm/sec (95% CI = 2-4 cm/sec) (p<0.0001). With ankle exercise while sitting, right popliteal vein TAPV increased to 18 cm/sec (95% CI =15-21 cm/sec) (p<0.0001). In conclusion, in both the supine and sitting positions, ankle exercise increased venous blood velocity, thereby transiently reducing a tendency toward venous stasis. Such ankle exercise might be useful in the prevention of stasis-induced deep venous thrombosis.

Abstract 2513: Assessment of Both Coronary Microvascular Damage and Epicardial Flow Velocity Measurement Immediately after Successful Percutaneous Coronary Intervention for Acute Myocardial Infarction Predicts In-Hospital Complications and Survival

Quantitative measurement of post-reperfusion epicardial flow velocity by a Doppler guidewire can predict clinical cardiac events in patients with acute myocardial infarction (AMI). It has also been reported that the coronary flow velocity pattern in patients with microvascular dysfunction is characterized by the presence of early systolic retrograde flow and a rapid diastolic deceleration time (DDT). The purpose of this study was to examine the role of assessing both epicardial flow velocity and microvascular damage in the prediction of in-hospital complications and survival after percutaneous coronary intervention (PCI). Two hundred and eleven consecutive patients with first anterior AMI who underwent successful PCI were subjected to coronary flow measurement immediately after successful PCI with a Doppler guidewire. The coronary flow velocity spectrum provided the following parameters: time-averaged peak velocity (cm/s, APV), systolic peak velocity (cm/s) and DDT (ms). We defined the presence of microvascular dysfunction as DDT ≤600 ms and the presence of systolic flow reversal, and slow epicardial flow as resting APV ≤10cm/s. We classified the patients into three categories: without microvascular dysfunction (group 1, n=122), with microvascular dysfunction and normal epicardial flow (group 2, n= 54), with microvascular dysfunction and slow epicardial flow (group 3, n=35). The clinical event rate was compared among the 3 groups. The in-hospital event rates for congestive heart failure, cardiac rupture and death were highest in group 3 and lowest in group 1 (Table ). Assessment of both coronary microvascular damage and epicardial flow velocity can accurately predict in-hospital complications and survival in AMI patients who underwent successful reperfusion of the infarct-related coronary artery, identifying a subset of high risk patients. In-hospital event rates (%)

Vascular Resistance in the Carotid Artery: An In Vitro Investigation of Embolic Protection Filters

To assess in vitro performance of four embolic protection filters (EPFs) with a varying mass of injected particles. Evaluation is based on capture efficiency, pressure gradient, flow rate, and vascular resistance. A bench-top flow apparatus was used for in vitro testing of four devices (Spider RX, FilterWire EZ, RX Accunet, and Emboshield). A silicone phantom with average human carotid artery dimensions and a 70% symmetric internal carotid artery (ICA) stenosis was used to model the carotid bifurcation. A blood-mimicking solution (glycerol/deionized water) was circulated at the time-averaged mean peak velocity for the common carotid artery. Five and 10 mg of 200- or 300-mum-diameter microspheres were injected into the ICA to evaluate the capture efficiency of the devices. The normalized pressure gradient, flow rate, and vascular resistance in the ICA were calculated from measured values of pressure and flow rate. The Spider RX captured the most particles (99.9% for 5 mg, 98.4% for 10 mg) and was associated with the slightest increase in pressure gradient (+8%, +15%) for both masses of microspheres injected. The Spider RX and FilterWire EZ were associated with the slightest decreases in flow rate (Spider RX, -1.9% and -12.1%; FilterWire EZ, -3.5% and -8.2%) and the slightest increases in vascular resistance (Spider RX, +10.1% and +33.0%; FilterWire EZ, +20.5% and +32.7%). The device-specific porosity was calculated, and the Spider RX was found to have the greatest at 50.4%; the Emboshield had the lowest at 2.2%. The Spider RX and FilterWire EZ had the best overall performances. Design features such as porosity and pore density are important parameters for improving the effectiveness of EPFs. Vascular resistance in the ICA is a flow-derived variable indicative of device performance and affected by the filter design features.

Abstract 3340: Coronary Flow Velocity Pattern Immediately After Percutaneous Coronary Intervention Predicts Left Ventricular Remodeling in Patients with Acute Myocardial Infarction

Background: Studies using the Doppler guidewire have shown that coronary flow velocity (CFV) pattern in recanalized infracted arteries predicts recovery of regional left ventricular (LV) function, in-hospital complications, and long-term cardiac events. However, the relationship between the CFV pattern after reperfusion and serial changes in LV volumes is not clear. We postulated that the quantitative CFV measurement immediately after successful percutaneous coronary intervention (PCI) might be associated with the LV remodeling. To test this hypothesis, we prospectively analyzed the LV remodeling according to CFV parameters measured by the Doppler guidewire in patients with acute myocardial infarction (AMI). Methods: Consecutive 211 patients with first-time anterior AMI underwent successful PCI (&lt;50% residual stenosis with TIMI flow grade 2–3) and coronary flow measurement with the Doppler guidewire. The CFV spectrum provided the following parameters: time-averaged peak velocity (cm/s), systolic peak velocity (cm/s), and diastolic deceleration time (ms). Left ventriculograms obtained immediately after PCI and 6 months after the infarction were analyzed to measure the end-diastolic volume index and end-systolic volume index. The LV remodeling was defined as an increase in end-diastolic volume index ≥20%. Result: The optimal cutoff values to predict LV remodeling (defined as 6-month LV dilation ≥20%) were 20 cm/s for time-averaged peak velocity, 0 cm/s for systolic peak velocity and 550 ms for diastolic deceleration time (sensitivity=0.63, specificity=0.56; sensitivity=0.76, specificity=0.85; and sensitivity=0.85, specificity=0.85, respectively). Systolic peak velocity and diastolic deceleration time correlated to the LV end-diastolic volume index obtained 6 months after AMI(r= −0.67; p&lt;0.001 and r= −0.78; p&lt;0.001, respectively). Conclusions: The CFV pattern appears to be an accurate predictor of LV remodeling even in patients who received successful PCI in the left anterior descending coronary artery immediately after AMI. This index, therefore, identifies a subset of patients at-risk.

In Vitro Performance Assessment of Distal Protection Devices for Carotid Artery Stenting: Effect of Physiological Anatomy on Vascular Resistance

To assess in vitro the performance of 5 distal protection devices (DPDs) by evaluating the capture efficiency, pressure gradient, volume flow rate, and vascular resistance in the internal carotid artery (ICA). The time-averaged mean peak velocity in the common carotid artery and a blood-mimicking solution were used to simulate physiologICAl conditions in a silicone carotid phantom representing average human carotid artery geometry with a 70% symmetrICAl ICA stenosis. Five milligrams of dyed 200-microm nominal diameter polymer microspheres (larger than the pore size of the devices, except Spider RX, which was tested with 300-microm-diameter particles) were injected into the ICA. The percentages of particles missed after injection and lost during device retrieval were measured for the 5 devices (Spider RX, FilterWire EZ, RX Accunet, Angioguard XP, and Emboshield). The normalized pressure gradient, fraction of the volume flow rate, and vascular resistance in the ICA were calculated. Spider RX captured the most particles (missing 0.06%, p<0.05) and yielded the smallest normalized pressure gradient increase (4.2%), the largest volume flow rate fraction (0.40), and the smallest vascular resistance in the ICA (272 mmHg/L x min(-1), a 5.4% increase with respect to initial conditions). Angioguard XP captured the fewest particles (missing 36.3%, p<0.05 except Emboshield) and resulted in the largest normalized pressure gradient increase (37%) in the ICA. RX Accunet produced the smallest volume flow rate fraction in the ICA (0.30) and the largest vascular resistance in the ICA (470 mmHg/ L x min(-1), an 82.2% increase). Emboshield migrated approximately 6 cm distal to the original position after particle injection. FilterWire EZ lost the fewest particles during retrieval (0.45%, p<0.05 except Accunet RX and Spider RX) and had the best overall performance with 200-microm emboli (p<0.05 except Accunet RX). None of the devices tested completely prevented embolization. Overall, Spider RX had the best performance and is conjectured to have the best wall apposition of the devices tested. Vascular resistance should be considered a key filter design parameter for performance testing since it represents a quantitative estimation of the "slow-flow phenomenon." Our findings should be extrapolated cautiously to help interventionists choose the best device.

Effect of a nitric oxide donor on the ophthalmic artery flow velocity waveform in preeclamptic women.

To evaluate the effects of an antihypertensive agent on the orbital circulation of preeclamptic women. We studied the ophthalmic arteries of 10 healthy pregnant women and 10 women with severe preeclampsia by pulsed Doppler ultrasonography and evaluated the effect of transdermal isosorbide dinitrate, a nitric oxide donor, on preeclamptic women. The average pulsatility index and resistive index were significantly lower, whereas the average end-diastolic velocity, time-averaged mean peak velocity, and peak ratio, which quantifies characteristic changes in the ophthalmic artery flow velocity waveform, were higher in preeclamptic women. Transdermal isosorbide dinitrate significantly reduced the average end-diastolic velocity (P < .05) and peak ratio of the ophthalmic artery (P < .01), whereas it did not significantly affect other indices. Orbital circulation was altered in preeclamptic women. A nitric oxide donor affected orbital circulation. Peak ratio was a sensitive index for evaluating orbital circulation in preeclampsia.

Effects of cilostazol on cerebral blood flow, P300, and serum lipid levels in the chronic stage of cerebral infarction

The effects of cilostazol (Pletaal, Otsuka Pharmaceutical Co., Tokyo, Japan) on cerebral blood flow, P300 event-related potentials, and serum lipid levels were examined in patients in the chronic stage of cerebral infarction. This study included 20 patients (13 men and 7 women, mean age 67 ± 11 years) with cerebral infarction who had taken ticlopidine (100 mg orally, twice a day). Quantitative cerebral blood flow measurements by Patlak plot analysis, ultrasound examinations of the common carotid arteries, and measurements of P300 event-related potentials and serum lipid levels were performed. Ticlopidine was then replaced with cilostazol (100 mg orally, twice a day) while other medications remained unchanged. The same examinations were performed again 3 months later. After replacement of ticlopidine with cilostazol, cerebral blood flow significantly increased in the frontal white matter, temporal cortex, and occipital cortex compared with cerebral blood flow before replacement with cilostazol. Ultrasonograms of the common carotid arteries showed no significant differences in intima-media thickness before and after replacement. However, peak systolic velocity, time-averaged peak velocity, and volume flow all significantly increased after replacement. Blood flow in the frontal white matter showed a significant negative correlation with P300 latency before and after replacement of ticlopidine with cilostazol. And P300 latency improved significantly after replacement with cilostazol. Regarding lipid levels, total cholesterol, triglycerides, and remnant-like particles-cholesterol all decreased significantly after replacement with cilostazol. Cilostazol, an inhibitor of platelet aggregation, was thus concluded to be effective in improving cerebral blood flow, cerebral function, and serum lipid levels in patients in the chronic stage of cerebral infarction. Copyright © 2001 by National Stroke Association

Effect of distal stenosis of internal thoracic artery bypass grafts on longitudinal phasic blood flow velocity characteristics

Background Left internal thoracic artery (LITA) bypass conduits show gradual longitudinal transition in their phasic flow velocity patterns from the proximal to distal segments, but little is known about the influence of distal stenosis, particularly early after surgery, on that characteristic. The purpose of this study was to evaluate the influence of distal stenosis on these flow velocity patterns. Methods We examined 24 LITAs within 1 month (7 to 30 days) after surgery with a Doppler-tipped guide wire at the proximal, mid, and distal segments. Maximum peak velocities (MPV), time averaged peak velocities (APV), and velocity-time integrals (VTI) were measured. Results In LITAs without stenosis (n = 14, group A), the APV, MPV, and VTI values at the diastole were significantly greater than those for distal stenosis (minimal lumen diameter >75%, n = 10, group B). The values of the 3 indexes at the systole in each segment did not differ significantly between the 2 groups. Both groups showed gradual increases in the diastolic/systolic ratios of the 3 indexes from the proximal to distal portions, the ratios in group A being significantly larger than that in group B (APV, P < .001; MPV, P < .01; TVI, P < .01, respectively). For these indexes, sensitivity and specificity for predicting stenosis of LITA was higher in the proximal and mid portion than in the distal. Conclusions Anastomotic stenosis decreases the diastolic flow component but not the systolic one. By using diastolic/systolic ratios of the 3 indexes, it is possible to predict distal stenosis of LITA from the resting phasic flow velocity pattern. (Am Heart J 1999;138:468-76.)

Noninvasive Measurement of Left Coronary Blood Flow Reserve by Transthoracic Doppler Echocardiography: Comparison with Doppler Guidewire Ultrasonography.

The development of new ultrasound instrumentation has made epicardial coronary artery blood flow imaging easier with the use of transthoracic coronary Doppler echocardiography (TCDE). This study was performed to investigate the accuracy of coronary blood flow reserve (CFR) measurement by TCDE. In 15 patients with ischemic heart disease in the absence of valvular disease or atrial fibrillation, coronary flow at rest and flow with hyperemia induced by intravenous dipyridamole infusion were recorded by TCDE and Doppler guidewire ultrasonography. The CFR was determined as the ratio of the maximum hyperemic diastolic time-averaged peak velocity to the velocity at rest in the proximal or distal left anterior descending coronary artery. It was found that the CFR of the left anterior descending coronary artery measured by TCDE was comparable in accuracy with CFR measured by invasive methods (r = 0.87, P < 0.0001, n = 15).

Restricted coronary flow reserve in patients with mitral regurgitation improves after mitral reconstructive surgery.

The purpose of this study was to assess coronary flow characteristics in patients with chronic mitral regurgitation (MR). Coronary flow reserve (CFR) has been reported to be restricted in cases with left ventricular (LV) volume overload caused by aortic regurgitation and increased LV preload. The study populations consisted of 31 patients with nonrheumatic chronic MR. Eleven with chest pain and normal coronary arteries served as control subjects. Phasic coronary flow velocities were obtained in the proximal segment of the angiographically normal left anterior descending coronary artery at rest and during hyperemia (0.14 mg/kg/min adenosine infusion intravenously) using a 0.014-in. (0.036 cm), 15-MHz Doppler guide wire. Coronary flow reserve was obtained from the ratio of hyperemic/baseline time-averaged peak velocity (APV). Thirteen cases who underwent mitral valve reconstructive surgery were also studied 1 month after surgery. Compared with control subjects, CFR was significantly reduced in cases with MR (2.1+/-0.5 vs. 33+/-0.6, respectively, p < 0.01) because baseline APV was significantly greater (28+/-8 vs. 19+/-6 cm/s, respectively, p < 0.01), although maximal hyperemic APV was not significantly different (56+/-14 vs. 61+/-16 cm/s, respectively, p = NS). Significant correlations were obtained between CFR and LV end-diastolic pressure (LVEDP) (r = 0.70, p < 0.01), LV mass index (r = 0.42, p < 0.01), LV end-diastolic volume (r = 038, p = 0.04) and MR volume (r = 0.39, p = 0.03), and stepwise regression analysis showed LVEDP was the most important determinant of CFR in MR (r2 = 0.49, p < 0.0001). This restricted CFR improved significantly after mitral valve reconstructive surgery (2.1+/-0.5 vs. 3.1+/-0.6, respectively, p < 0.01) because of reduction of baseline APV (28+/-8 vs. 21+/-8 cm/s, respectively, p < 0.01). Coronary flow reserve is limited in cases with MR because of elevation of baseline resting flow velocity. This reduction of CFR correlates well with increase in LV preload, mass and volume overload, especially with increase in LV preload, and this restricted CFR improves after mitral valve surgery.

Flow Dynamics of Angiographically No-Flow Patent Internal Mammary Artery Grafts

Objectives. This study sought to assess the flow dynamics of internal mammary artery grafts (IMAGs) in no-flow situations by use of a Doppler guide wire.Background. Functionally no-flow and anatomically patent IMAGs have been reported by angiography in patients with a patent recipient coronary artery.Methods. The study included 12 patients with an IMAG to the left anterior descending coronary artery (LAD) in whom no-flow patency of the graft was suspected angiographically. Thirteen patients with a normally functioning IMAG whose LAD was occluded in the proximal portion and was supplied only from the graft served as control patients. Phasic flow velocities were recorded in the distal portion of the graft and the recipient LAD using a 0.014-in., 15-MHz Doppler guide wire at rest and during hyperemia (0.14-mg/kg body weight per min intravenous adenosine infusion).Results. There were no significant differences in systolic (15 ± 3 vs. 19 ± 6 cm/s, p = NS), diastolic (35 ± 11 vs. 37 ± 7 cm/s, p = NS) and time-averaged peak velocities at rest (20 ± 5 vs. 21 ± 5 cm/s, p = NS), during hyperemia (51 ± 12 vs. 54 ± 8 cm/s, p = NS) and in coronary flow velocity reserve (2.8 ± 0.9 vs. 2.7 ± 0.3, NS) in the native LAD in patients with a no-flow patent graft versus control patients. Within the graft, to and fro signals with systolic reversal and diastolic anterograde flow were seen in the no-flow patent grafts, although anterograde flow signals were recorded in systole and diastole in control patients. Systolic (−28 ± 19 vs. 22 ± 9 cm/s, p < 0.01), diastolic (18 ± 17 vs. 44 ± 14 cm/s, p < 0.01) and time-averaged (−2 ± 6 vs. 26 ± 9 cm/s, p < 0.01) peak velocities at rest were significantly smaller in the no-flow patent grafts than in control grafts. During hyperemia, anterograde flow became predominant, with a reduction in retrograde systolic flow signal and an increase in diastolic flow velocity and time-averaged peak velocity in the no-flow patent grafts, and no-flow situations disappeared temporarily.Conclusions. Functionally no-flow situations of IMAGs manifesting to and fro signals with systolic flow reversal and diastolic antegrade low flow velocity are temporary conditions in certain hemodynamic circumstances, and these grafts function as conduits during hyperemic states.