Alterations of phasic coronary artery flow velocity in humans during percutaneous coronary angioplasty

Postoperative flow characteristics of left internal thoracic artery grafts

Twenty patients whose left internal thoracic artery (LITA) was anastomosed to the left anterior descending artery (LAD) underwent postoperative coronary angiography and Doppler ultrasound velocimetry. During angiography, the diameter of the LITA conduit was measured at three points: proximal, mid, and distal. The degree of left anterior descending artery stenosis proximal to the anastomotic site was evaluated by densitometry. The LITA flow velocity pattern was obtained at the three points to calculate the total, systolic, and diastolic flow volume. There were significant differences in the total LITA flow among the three points (proximal, 36.0 +/- 17.2 mL/min; mid, 29.9 +/- 15.2 mL/min; distal, 27.2 +/- 14.0 mL/min; p < 0.001 between the proximal and the mid or distal portions). The degree of left anterior descending artery stenosis affected the distal LITA flow and diameter (r = 0.823 and 0.811, respectively). There were significant differences in the systolic LITA flow among the three points (proximal, 13.2 +/- 6.5 mL/min; mid, 8.1 +/- 4.7 mL/min; distal, 5.6 +/- 3.4 mL/min; p < 0.001 between the proximal and the mid or distal portions). However, there was no statistically significant difference in the diastolic LITA flow among the three points (proximal, 22.9 +/- 11.0 mL/min; mid, 21.7 +/- 10.8 mL/min; distal, 21.6 +/- 10.8 mL/min). We conclude that a lower degree of LAD stenosis significantly reduces the LITA flow, inducing the string phenomenon. Additionally, during the diastolic phase, the LITA graft transports the blood primarily to the coronary artery but not to the side branches. Therefore, the steal phenomenon might not apply in the setting of an LITA graft.

Effects of nonuniform insonation by catheter-tipped Doppler transducers on velocity estimation

Studies of the coronary arteries using intravascular Doppler catheters have frequently been performed to assess the local circulation in various clinical situations. The parameters which are correlated with clinical observations are usually calculated from the intensity weighted mean velocity (IWMV) or the maximum velocity extracted from the Doppler power spectrum. It is known that these estimates are affected by nonuniform insonation of the blood vessel by the ultrasonic beam. The sample volume of a commercially available Doppler catheter has been theoretically and experimentally studied, and the effects of the nonuniform sampling of the vessel by the ultrasound beam examined. The results show that the velocity estimates are dramatically affected by both the position of the catheter within the artery, and the blood velocity profile. It is concluded that the maximum velocity estimator is more reliable than the IWMV estimator, but that results obtained with this estimator must also be treated with extreme caution.

Clinical outcome of deferring angioplasty in patients with normal translesional pressure-flow velocity measurements

OBJECTIVES

The objective of this study was to determine the feasibility, safety and outcome of deferring angioplasty in patients with angiographically intermediate lesions that are found not to limit flow, as determined by direct translesional hemodynamic assessment.

BACKGROUND

The clinical importance of some coronary stenoses of intermediate angiographic severity frequently requires noninvasive stress testing. Direct translesional pressure and flow measurements may assist in clinical decision making in patients with such stenoses.

METHODS

Translesional spectral flow velocity (Doppler guide wire) and pressure data were obtained in 88 patients for 100 lesions (26 single-vessel and 74 multivessel coronary artery lesions) with quantitative angiographic coronary narrowings (mean +/- SD diameter narrowing 54 +/- 7% [range 40% to 74%]). Target lesion angioplasty was prospectively deferred on the basis of predetermined normal values, defined as a proximal/distal velocity ratio < 1.7 or a pressure gradient < 25 mm Hg, or both. Patients were followed up for 9 +/- 5 months (range 6 to 30).

RESULTS

In the deferred angioplasty group, translesional velocity ratios were similar to those of a normal reference group (mean 1.1 +/- 0.32 vs. 1.3 +/- 0.55) and significantly lower than those of a reference cohort of patients who had undergone angioplasty (2.27 +/- 1.2, p < 0.05). The mean translesional pressure gradient in the deferred angioplasty group was also lower than that in the angioplasty group (10 +/- 9 vs. 45 +/- 22 mm Hg, p < 0.001). At follow-up in the deferred angioplasty group, four, six, zero and two patients, respectively, had had subsequent angioplasty, coronary artery bypass graft surgery or myocardial infarction or had died. In one patient, death was related to angioplasty of a nontarget artery lesion, and one patient with multivessel disease had a cardiac arrest due to ventricular fibrillation 12 months after lesion assessment. Among the 10 patients requiring later angioplasty or coronary artery bypass grafting, only six procedures were performed on target arteries. No patient had a complication of translesional flow or pressure measurements.

CONCLUSIONS

These data demonstrate the safety, feasibility and clinical outcome of deferring angioplasty of coronary artery narrowings associated with normal translesional coronary hemodynamic variables. Given the practice of performing angioplasty without ischemic testing or when testing is inconclusive, translesional hemodynamic data obtained at diagnostic catheterization can identify patients in whom it is safe to postpone angioplasty.

Part XII: Assessment of serial lesions in the proximal right coronary artery following intracoronary thrombolysis

Assessment of angiographically serial coronary lesions at the time of diagnostic catheterization remains a difficult clinical problem. Doppler flow velocity data is easily obtainable and allows physiologic interrogation of the distal coronary microcirculation, but has limitations in the detection of some flow-limiting stenoses. In cases of serial lesions or distal arterial disease, particularly after thrombolysis, flow velocity data may be insufficient to identify the hemodynamic significance of the coronary lesions. Translesional pressure measurements may be combined with flow velocity data to support an appropriate physiologically based therapeutic approach.

Effect of angiographic and hemodynamic results of coronary balloon angioplasty on late angiographic outcome

A small residual stenosis and a low residual translesional pressure gradient after percutaneous transluminal coronary angioplasty (PTCA) are thought to be associated with lower rates of restenosis. However, these two posprocedure parameters have not been studied simultaneously in relation to late angiographic outcome. Restudy angiograms after successful single-vessel and single-lesion PTCA were performed in 1261 patients, who were divided into three groups according to final residual stenosis: group 1, 0% to 19%, group 2, 20% to 34%, and group 3, 35% to 49%. This study population also was divided into two groups by final residual pressure gradient: < or = 17 and > or = 18 mm Hg. Luminal patency at restudy and restenosis rates by these definitions were studied. By the definition of > or = 50% stenosis at restudy, group 1 had the lowest restenosis rate, and group 3 had the highest. By the definition of an increase of > or = 30% stenosis compared with the immediate post-PTCA result, group 1 had the highest restenosis rate, and group 3 had the lowest. Although it had the greatest loss of luminal diameter over the follow-up period, group 1 maintained the greatest luminal patency at restudy. A residual pressure gradient < or = 17 mm Hg was associated with lower restenosis rate regardless of the definition used. Despite greater loss of luminal diameter over the follow-up period, optimal postprocedure angiographic results may result in better long-term luminal patency. Transluminal pressure gradient is more predictive of late angiographic results regardless of the definition used. Further studies, with hemodynamic measurements, may reveal potential clinical implications.

Doppler flow velocity measurements during coronary angioplasty

In addition to further studies using Doppler catheters to assess blood flow velocity during coronary angioplasty this study intends to evaluate the functional significance of coronary stenoses and to estimate their hemodynamic relevance prior to and after percutaneous transluminal coronary angioplasty (PTCA). Diameters of coronary artery stenoses were quantified by means of the cardiovascular angiographic analysis system (CAAS) both prior to and following successful PTCA in 37 patients. During coronary artery angioplasty a 12 M:Hz 0.018-in. Doppler-tipped guidewire was used to measure prestenotic and poststenotic parameters of coronary artery flow velocity both prior to and following PTCA. The minimal stenosis diameter was raised from 1.01 +/- 0.58 to 1.76 +/- 0.73 mm (P < 0.0001), the percent diameter stenosis decreased from 63 +/- 11 to 35 +/- 6% (P < 0.0001). Prestenotic average (APV) and maximum peak velocity (MPV), peak velocity integral (PVI), average systolic (ASPV) and diastolic (ADPV) peak velocity, systolic (SPVI) and diastolic (DPVI) peak velocity integral, and diastolic/systolic velocity ratio showed--in contrast to further studies--a considerably significant difference (P < 0.05), whereas poststenotic Doppler data (APV, MPV, PVI, ASPV, DSPV, SPVI, DPVI, DSVR) differed highly significantly (P < 0.0001) prior to and following PTCA. Prestenotic and poststenotic measurements of coronary artery flow velocity differed significantly before and after PTCA and offer the potential for estimating both the hemodynamic relevance of coronary artery stenoses and success of PTCA.

Intracoronary Doppler guide wire versus stress single-photon emission computed tomographic thallium-201 imaging in assessment of intermediate coronary stenoses

OBJECTIVES

The purpose of this study was to compare measures of coronary flow reserve by an intracoronary Doppler guide wire with results of stress single-photon emission computed tomographic (SPECT) thallium-201 imaging in patients with intermediate coronary artery disease (40% to 70% stenosis).

BACKGROUND

Visual assessment of the coronary arteriogram as a means of predicting the physiologic significance of intermediate coronary stenoses is inaccurate. Coronary flow reserve is a reliable marker of the functional importance of a coronary lesion. The recent development of an intracoronary Doppler guide wire permits routine assessment of coronary flow reserve distal to coronary artery stenoses.

METHODS

We prospectively evaluated coronary flow reserve in 30 subjects with intermediate stenoses using an intracoronary Doppler guide wire during elective coronary angiography. Patients subsequently underwent stress SPECT thallium-201 testing, and the blinded interpretations were correlated. Coronary flow reserve in a control group with normal coronary arteries classified our sample into group 1 (abnormal flow reserve, < 2.0) and group 2 (normal flow reserve, > or = 2.0).

RESULTS

As defined, the coronary flow reserve of 16 vessels in group 1 was diminished in comparison to that of 19 vessels in group 2 (p = 0.0001). Qualitative and quantitative analysis of stress SPECT thallium-201 images confirmed perfusion defects in 15 of 16 vascular territories in group 1 in contrast to 1 of 19 regions in group 2. The sensitivity, specificity and overall predictive accuracy of Doppler-determined coronary flow reserve for stress SPECT thallium-201 results were 94%, 95% and 94%, respectively.

CONCLUSIONS

In appropriately selected patients with intermediate coronary artery stenoses, Doppler guide wire determination of lesion significance provides equivalent data to those acquired by stress SPECT thallium-201 imaging.

Blood flow velocity in the right coronary artery: assessment before and after angioplasty

OBJECTIVES

This study attempted 1) to assess the utility of rest measurements of intracoronary blood flow velocity for the physiologic assessment of coronary stenoses before and after right coronary artery angioplasty, and 2) to compare the phasic flow pattern in the right coronary artery proper with the phasic flow pattern in its major branches to the left ventricle.

BACKGROUND

Previous investigations have demonstrated that a reduction in distal blood flow velocity and a loss of distal diastolic predominant flow are characteristic of physiologically significant stenoses and that these indexes normalize after successful coronary artery dilation. However, these studies were predominantly performed in the left coronary artery. The utility of monitoring rest velocity variables during angioplasty of the right coronary artery has not been studied.

METHODS

We studied 20 patients undergoing angioplasty of the right coronary artery with use of a Doppler angioplasty guide wire.

RESULTS

Values were expressed as the mean value +/- 1 SD. The rest average peak velocity did not decrease distal to angiographically significant right coronary artery stenoses (23.3 +/- 9.4 cm/s proximal vs. 20.2 +/- 11.1 cm/s distal, p = 0.20). The proximal/distal velocity ratio was 1.4 +/- 0.9 before angioplasty and did not significantly decrease after angioplasty (p = 0.58). This study had a 99.4% power to detect a difference between proximal and distal average peak velocity. There was no relation between percent diameter stenosis and proximal/distal velocity ratios (r = 0.15, p = 0.55). Diastolic predominant flow was not observed in the proximal or distal right coronary artery. However, after angioplasty, diastolic predominant flow was observed in the posterolateral and posterior descending coronary arteries.

CONCLUSIONS

Rest phasic Doppler flow velocity indexes are not useful for evaluating stenoses in the right coronary artery proper before or after angioplasty. In contrast to the right coronary artery proper, diastolic predominant flow is observed in the posterior descending and posterolateral coronary arteries. The utility of measuring hyperemic Doppler flow velocity indexes, such as distal coronary flow reserve, for assessing right coronary artery stenoses merits further investigation.

Continuous coronary flow velocity monitoring during coronary interventions: velocity trend patterns associated with adverse events

Continuous measurement of blood flow velocity during interventional procedures has the potential to provide an early warning of coronary flow instability, which can lead to abrupt closure or other adverse events before angiography. The magnitude and fluctuations of the average velocity over time (trend) was studied by using a 0.018-inch Doppler-tipped angioplasty guide wire in 32 patients after coronary angiography (n = 20), atherectomy (n = 2), urgent stent (n = 6), urgent vein graft thrombolysis (n = 4), or acute myocardial infarction (n = 2). The patients (mean age 60 +/- 11 years) had postprocedural in-laboratory flow monitoring for a mean of 19 +/- 11 (range 8 to 36) minutes. The coronary artery monitored was the left anterior descending in 13, circumflex in 6, right coronary artery in 9, and saphenous vein graft in 4. Seven patients had flow-related events during continuous flow velocity monitoring before serial angiographic study. These events included coronary vasospasm (abrupt flow acceleration), vasovagal flow cessation, cyclical flow variations resulting from accumulation of intraluminal thrombus, and rapid decline of flow velocity. The last two patterns were associated with abrupt vessel closure during angioplasty. Continuous flow velocity monitoring is easily incorporated into routine interventional procedures and provides an early indication of unstable flow and the potential for abrupt vessel closure and other adverse events.

Slope of the instantaneous hyperemic diastolic coronary flow velocity-pressure relation. A new index for assessment of the physiological significance of coronary stenosis in humans

BACKGROUND

Coronary flow reserve (CFR), the functional index of stenosis severity more frequently used in the catheterization laboratory, is greatly affected by the hemodynamic conditions at the time of measurement and cannot be applied in the immediate assessment of the outcome of coronary interventions. The aim of the present study was to establish the feasibility and reproducibility of the assessment of the slope of the instantaneous diastolic relation between coronary flow velocity and aortic pressure during maximal hyperemia (IHDVPS) using a spectral analysis of the intracoronary Doppler signal, to assess the sensitivity and specificity of this index in the detection of flow-limiting coronary stenoses in comparison with CFR, and to study the possibility of determining the zero-flow pressure from the intercept of the velocity-pressure relation on the pressure axis during a controlled cardiac arrest.

METHODS AND RESULTS

The instantaneous peak coronary flow velocity measured after intracoronary papaverine with a Doppler guidewire was plotted against the simultaneously measured aortic pressure, and the slope of the velocity-pressure relation in the phase of progressive diastolic velocity decrease was calculated during four consecutive beats. In nine normal arteries, a controlled diastolic cardiac arrest was induced by an intracoronary bolus injection of 3 mg adenosine. The IHDVPS could be assessed in 79 of 95 patients (83%), with a moderate intraobserver variability (0.4 +/- 11% after independent selection of different beats during maximal hyperemia). The IHDVPS showed no significant correlation with heart rate, mean diastolic aortic pressure, type of vessel studied, and cross-sectional area at the site of the velocity recording. The IHDVPS was significantly lower in arteries with > or = 30% diameter stenosis than in normal or near-normal arteries (0.71 +/- 0.48 versus 1.73 +/- 0.80 cm.s-1.mm Hg-1, P < .0000002). In the stenosis group, both IHDVPS and CFR were significantly correlated with the minimal luminal cross-sectional area (r = .46, P < .05 and r = .62, P < .002, respectively). The study of the velocity-pressure relation during long diastolic pauses showed a curvilinear relation between velocity and pressure in the lower pressure range, with an upward concavity to the velocity axis and no intercept with the pressure axis in most cases.

CONCLUSIONS

The IHDVPS can distinguish between arteries with and without coronary stenoses and has a significant inverse correlation with the severity of the stenosis. Under the stable hemodynamic conditions of this study, the IHDVPS and CFR had similar sensitivities and specificities in distinguishing normal and stenotic vessels and demonstrated similar correlation with minimal luminal cross-sectional area. The curvilinearity of the velocity-pressure relation during long diastolic pauses, possibly due to a significant reduction of luminal cross-sectional area at low pressures, complicates the use of the flow velocity-pressure relation for the assessment of the zero-flow pressure.

Limitations of translesional pressure and flow velocity for long ostial left anterior descending stenoses

Translesional pressure and flow velocity can be used to assess angiographically intermediate or indeterminate lesions. Ostial narrowings and long lesions represent situations that may require both pressure and flow velocity assessment. In patients with hypertension, diabetes mellitus, and chronic renal failure, distally measured absolute and regional coronary reserve values alone may not be helpful in selecting lesions requiring intervention.

Digital angiographic assessment of the physiological changes to the regional microcirculation induced by successful coronary angioplasty

BACKGROUND

Impulse response analysis of digital coronary angiographic images calculates a parameter known as the mean transit time of the microcirculation (Tmicro). This has been shown to accurately assess the regional microcirculatory response to proximal stenosis in relation to flow. Our goal was to apply impulse response analysis to patients undergoing successful angioplasty and to quantify the induced physiological changes with respect to quantitative angiographic measurements of stenosis dimensions.

METHODS AND RESULTS

We studied 24 patients before and after successful single-vessel percutaneous transluminal coronary angioplasty (PTCA). Minimal luminal stenosis area was increased from 0.9 +/- 0.6 before PTCA to 4.1 +/- 1.3 mm2 after PTCA (P < .0001). In all patients this was accompanied by an increase in the inverse of Tmicro (Tmicro-1), from 8.5 +/- 3.0 to 26.5 +/- 9.0 min-1 (P < .0001) with a linear correlation between Tmicro-1 and minimal luminal stenosis area (r = .73; SEE = 7.74). Stenosis flow reserve, estimated by integration of stenosis dimensions, increased in all patients from 1.8 +/- 1.0 to 4.5 +/- 0.4 after PTCA (P < .01). A comparison of Tmicro-1 with stenosis flow reserve revealed a nonlinear relation. In 16 patients undergoing PTCA of the left anterior descending or circumflex artery, contrast injections into the left main stem allowed simultaneous measurements of Tmicro-1 in the adjacent, nonstenotic artery. Adjacent artery Tmicro-1 did not change after PTCA (25.8 +/- 6.2 compared with 25.6 +/- 6.8 min-1 before PTCA; P = NS); moreover, Tmicro-1 of the dilated artery measured after PTCA was equivalent to the nonstenotic adjacent artery, indicating normalization of microcirculatory responses.

CONCLUSIONS

These data suggest that Tmicro-1 determined by digital angiographic impulse response analysis of a single contrast injection under resting flow conditions may be a practical method to assess the regional microcirculatory response to changes in stenosis severity effected by coronary angioplasty.

Coronary flow velocity during coronary angioplasty in regions of myocardial infarction

In patients undergoing angioplasty for angina after myocardial infarction, patterns of post-stenotic coronary blood flow velocity depend not only on satisfactory dilation of the flow-limiting lesion, but also on the vasoregulatory capacity of infarcted myocardium. The case examples demonstrate both normal and persistently abnormal flow velocity patterns following successful coronary angioplasty for post-infarction ischemia. Recognition of collateral flow patterns, easily available using the Doppler angioplasty guidewire, may provide valuable information predicting the viability of post-infarcted myocardium and the resolution of abnormal distal coronary flow patterns.

Correlation of pharmacological 99mTc-sestamibi myocardial perfusion imaging with poststenotic coronary flow reserve in patients with angiographically intermediate coronary artery stenoses

BACKGROUND

The physiological assessment of angiographically intermediate-severity stenoses remains problematic. Functional measurements of poststenotic intracoronary Doppler coronary flow reserve can be performed in humans but have not been correlated with hyperemic myocardial perfusion imaging or angiographic data in this patient population.

METHODS AND RESULTS

Thirty-three patients undergoing diagnostic quantitative coronary angiography (QCA) for assessment of intermediate-severity coronary artery disease (mean QCA percent diameter stenosis, 56 +/- 14%) were studied. Proximal and distal poststenotic Doppler coronary flow velocities were measured (left anterior descending coronary artery, 16; right coronary artery, 10; left circumflex artery, 7 patients) before and during peak maximal hyperemia with intracoronary adenosine (8 to 12 micrograms). Intravenous pharmacological stress (adenosine, 20 patients; dipyridamole, 13 patients) 99mTc-sestamibi tomographic perfusion imaging was performed within 1 week of coronary flow-velocity studies. kappa statistics were calculated to measure the strength of correlation among coronary flow velocities, perfusion imaging data, and QCA results. QCA stenosis severity (abnormal, > or = 50% diameter stenosis) and poststenotic Doppler coronary flow reserve (ratio of abnormal distal hyperemic to basal flow, < or = 2.0) were correctly correlated in 20 of 27 patients (74%; kappa = .48). QCA stenosis severity and 99mTc-sestamibi imaging (abnormal if one or more reversible myocardial segments were present in the poststenotic zone) were correlated in 28 of 33 patients (85%; kappa = .63). 99mTc-sestamibi imaging results agreed with the basal (nonhyperemic) proximal-to-distal velocity ratio (normal, < 1.7) in 15 of 31 patients (48%; kappa = .17). The strongest correlation occurred between hyperemic distal flow-velocity ratio measurements and 99mTc-sestamibi perfusion imaging results in 24 of 27 patients (89%; kappa = .78). All 14 patients with abnormal distal hyperemic flow-velocity values had corresponding reversible 99mTc-sestamibi tomographic defects. More reversibly hypoperfused segments were present in patients with abnormal poststenotic hyperemic flow-velocity ratios (abnormal, 2.4 +/- 0.7 segments; normal, 0.6 +/- 1.0 segments; P < .05). The number of poststenotic myocardial 99mTc-sestamibi perfusion defects was correlated with the QCA percent cross-sectional area reduction (P < .02) and with minimal luminal diameter (P < .05) of intermediate-severity coronary artery stenoses.

CONCLUSIONS

Two technologically diverse functional measures of stenosis severity--Doppler-derived poststenotic hyperemic intracoronary flow reserve and vasodilator stress 99mTc-sestamibi myocardial perfusion imaging--are highly (89%) correlated. The physiological assessment of coronary stenoses of angiographically intermediate severity may be improved by the use of these techniques.

Physiologic assessment of ostial left circumflex coronary artery disease using a Doppler guidewire before and after rotational atherectomy facilitated angioplasty

Intravascular Doppler assessment of coronary flow velocity has demonstrated the physiologic significance of intermediate stenoses and the success of coronary interventions. We describe a patient where Doppler evaluation confirmed the significance of an intermediate left circumflex ostial stenosis. We also describe the Doppler flow velocity characteristics after successful rotational atherectomy facilitated angioplasty.

Effect of L-arginine on coronary endothelial function in cardiac transplant recipients. Relation to vessel wall morphology

BACKGROUND

Coronary endothelial vasodilator dysfunction is a common finding in cardiac transplant recipients and may represent an early marker for the development of intimal thickening and graft atherosclerosis. The present study tested the hypothesis that endothelial dysfunction precedes intimal thickening and that administration of L-arginine, the precursor of endothelium-derived relaxing factor, improves endothelial vasodilator function of coronary conduit and resistance vessels if given at an early stage of graft atherosclerosis.

METHODS AND RESULTS

Acetylcholine (10(-6), 10(-5), 10(-4) mol/L) was infused into the left anterior descending or circumflex artery and repeated after intravenous infusion of L-arginine (10 mg.kg-1.min-1 over 20 minutes) in 18 cardiac transplant recipients. Epicardial responses were evaluated by quantitative angiography, and the microcirculation was studied by determination of coronary blood flow with a Doppler flow velocity wire. Intimal thickening was assessed by intravascular ultrasound (n = 14). In epicardial coronary arteries, acetylcholine tended to elicit vasoconstriction. Epicardial coronary vasoconstriction elicited by acetylcholine was attenuated by infusion of L-arginine (10(-4) mol/L, -6.8% versus -2.8%; P < .01); this beneficial effect was observed predominantly in patients with normal intravascular ultrasound characteristics. In coronary resistance vessels, acetylcholine induced vasodilation, reflected by increases in coronary blood flow. The acetylcholine-induced increase in blood flow was significantly enhanced with L-arginine (at a dose of 10(-4) mol/L, + 121% versus 176%; before versus after L-arginine, P < .002).

CONCLUSIONS

The coronary vasculature of cardiac transplant recipients exhibits a generalized endothelial dysfunction of conduit and resistance vessels. L-Arginine improves endothelial dysfunction of both coronary microvasculature and epicardial coronary arteries. The reversibility of epicardial endothelial dysfunction by L-arginine is more likely in vessels with normal wall morphology.

Effects of heart rate on phasic coronary blood flow pattern and flow reserve in patients with normal coronary arteries: a study with an intravascular Doppler catheter and spectral analysis

To assess the effects of pacing-induced tachycardia on phasic coronary blood flow pattern and flow reserve of left anterior descending artery, we examined 16 patients with chest pain and angiographically normal coronary arteries by using an intravascular Doppler catheter with spectral analysis of the velocity signal. The heart rate was increased from a mean of 68 +/- 11 beats/min during sinus rhythm to 100 beats/min and again to 120 beats/min. Cross-sectional area of the epicardial artery and resting systolic and diastolic coronary blood flows increased progressively, resulting in an elevation of total coronary flow from 142 +/- 54 ml/min during sinus rhythm to 190 +/- 66 ml/min at 100 beats/min (p < 0.05) and to 219 +/- 69 ml/min at 120 beats/min (p < 0.01). During maximal hyperemia with intracoronary injection of 10 to 12 mg of papaverine, there was an increase in the systolic coronary blood flow with a decrease in the diastolic flow, resulting in no significant change in the total flow. These alterations led to progressive reductions in coronary flow reserve from 3.9 +/- 0.7 during sinus rhythm to 2.9 +/- 0.9 at 100 beats/min (p < 0.01) and to 2.3 +/- 0.3 at 120 beats/min (p < 0.001). Thus careful consideration should be given to the effects of heart rate when phasic coronary blood flow pattern and flow reserve are assessed.

Identification of coronary artery stenoses and poststenotic blood flow patterns using a miniature high-frequency epicardial transducer

BACKGROUND

Intraoperative epicardial coronary Doppler ultrasound has the potential to provide anatomic and functional information. This technique has been hindered by the large size of standard transducers, but a miniature transducer is available that may fulfill the potential of coronary ultrasound.

METHODS AND RESULTS

Twenty consecutive patients who were undergoing coronary artery bypass grafting were studied and compared with 9 control patients with normal coronary arteries who were undergoing routine mitral valve surgery. A miniature 6.5-MHz transducer was used to image coronary arteries and measure coronary blood flow velocities. Seventeen proximal left anterior descending and 3 right coronary artery stenoses were studied. As defined by coronary angiography (1 to 34 days before surgery), there were 13 severe stenoses (> 70%), 4 moderate stenoses (40% to 70%), 2 minor stenoses (< 40%), and 1 subtotal occlusion. Stenoses were readily identified by ultrasound. Color flow mapping demonstrated laminar flow in normal arteries and nonlaminar flow across moderate and severe stenoses. In the control patients with unobstructed arteries, peak and mean diastolic velocities were 35 +/- 2.1 and 26 +/- 1.9 cm/s with peak and mean systolic velocities of 16 +/- 1.4 and 11 +/- 0.8 cm/s, respectively. Prestenotic flow velocities were not significantly different from normal control values, but a wide range of poststenotic flow disturbances were detected. Analysis of the 20 study patients did not reveal significant differences in poststenotic compared with prestenotic flow. A subgroup analysis of 12 patients with severe left anterior descending coronary artery stenoses was performed, and reversed poststenotic systolic flow was seen in 9. Prestenotic peak and mean systolic velocities were 16.5 +/- 1.7 and 11.9 +/- 1.1 cm/s, respectively, and were significantly altered downstream of the stenoses at -22.7 +/- 17.2 and -15.9 +/- 10.9 cm/s (P < .05 and P < .01, respectively). Reversed systolic flow was seen only distal to severe left anterior descending coronary artery stenoses and did not correlate with retrograde collateral filling as determined by preoperative coronary angiography. Moderate stenoses appeared to increase both systolic and diastolic components of poststenotic flow.

CONCLUSIONS

Epicardial Doppler ultrasound with a miniature transducer identifies coronary stenoses and associated blood flow disturbances. Compared with moderate lesions, severe stenoses demonstrated different poststenotic flow patterns. Intraoperative use of this technique may determine the hemodynamic significance of coronary stenoses.

Cocaine-induced microvascular spasm in Yucatan miniature swine. In vivo and in vitro evidence of spasm

The purpose of the present study was to determine the maximal coronary flow reserve (CFR) before and after the administration of successive cocaine doses (0.1, 0.5, 3, and 7 mg/kg IV) for 2 minutes at 10-minute intervals in eight miniature swine. CFR was assessed by the administration of adenosine (0.03, 0.3, and 3 mg IC). Hemodynamic and flow measurements were performed 3 minutes after each dose. Coronary flow (CF) was measured with a Doppler-tipped wire in the proximal left anterior descending coronary artery (LAD). Also, microvessels were dissected, and vessel diameters were measured by a videoelectronic dimension analyzer. In vivo, LAD CF increased fourfold, CFR increased twofold, and coronary vascular resistance (CVR) decreased fourfold after the administration of adenosine. In contrast, LAD CF decreased threefold, CFR decreased onefold, and CVR increased sixfold 3 minutes after the administration of cocaine. Adenosine (3 mg) was repeated 4 minutes after the administration of cocaine, and LAD CF increased 1.4-fold, CVR increased 2.5-fold, and CFR decreased onefold. Thus, adenosine partially reversed the potent cocaine constrictor effect. In vitro, 10(-9) mol/L cocaine decreased the diameter of the coronary microvessels from 129 +/- 12 to 127 +/- 12 microns, and 10(-4) mol/L cocaine decreased coronary microvessel diameter to 114 +/- 15 microns (P < .05). In conclusion, cocaine in vivo decreases CFR, and consistent with the in vivo effect, cocaine in vitro produced constriction of vessels < 200 microns. These results indicate that cocaine can produce profound microvascular spasm. This may contribute to the ischemia/infarction reported in patients who abuse cocaine and who are subsequently found to have normal epicardial coronary arteries.

Translesional pressure-flow velocity assessment in patients: Part I

Interventional physiology presents the operator with objective data to facilitate decision making. A thorough and validated understanding of the alterations of pressure and flow in the human coronary circulation is currently in progress. As illustrated in the case studies, some situations have data which may initially appear contradictory or unhelpful to clinical practice. These data should provide a framework to understand the dynamic physiology producing the clinical syndromes in patients undergoing coronary interventional procedures. Future Interventional Physiology Rounds will examine coronary pressure-flow responses during directional atherectomy, stents, and acute myocardial infarction.

Phasic coronary flow characteristics in patients with hypertrophic cardiomyopathy: a study by coronary Doppler catheter

Abnormal patterns of coronary flow velocity have been observed in patients with symmetric left ventricular hypertrophy in conditions such as aortic stenosis and systemic hypertension. However, phasic coronary flow characteristics have not been investigated in patients with asymmetric left ventricular hypertrophy in hypertrophic cardiomyopathy. The purpose of this study was to assess phasic coronary flow characteristics and their relation to echocardiographic and hemodynamic parameters in patients with hypertrophic cardiomyopathy. Coronary flow velocity was recorded in the left anterior descending artery with a 20 MHz Doppler catheter in eight patients with hypertrophic nonobstructive cardiomyopathy and eight control subjects with normal coronary arteries. Flow reversals observed in systole in all patients with hypertrophic cardiomyopathy, and the time velocity integrals of systolic flow were significantly smaller in patients with hypertrophic cardiomyopathy than in control subjects (-1.5 +/- 1.7 versus 4.3 +/- 1.2 cm; p < 0.01). The time from the beginning of diastole to peak diastolic velocity corrected by the square root of R-R interval (square root of RR) was prolonged significantly, and the velocity half-time from peak diastolic velocity corrected by square root of RR was shorter in the patients with hypertrophic cardiomyopathy compared with those in the control subjects (6.8 +/- 2.0 msec versus 4.0 +/- 0.6 msec [p < 0.01] and 9.2 +/- 4.9 msec versus 13.9 +/- 2.0 msec [p < 0.05], respectively). Peak velocity and time velocity integral of flow reversal showed significant correlations with anterior ventricular septal thickness (y = -0.5x + 13.5, r = 0.8, and p < 0.01; y = -1.3 +/- 16.8, r = 0.8, and p = 0.024, respectively), the septal/free wall thickness ratio (y = -0.1x + 1.1, r = 0.8, and p < 0.01; y = -0.2x + 1.4, r = 0.9, and p < 0.01, respectively), and the degree of narrowing of the first septal perforator arteries (y = 1.9x + 91.6, r = 0.8, and p = 0.012; y = 6.1x + 80.6, r = 0.9, and p < 0.01, respectively). In conclusion, flow reversal in systole and slow acceleration and rapid deceleration in diastole were characteristics in patients with hypertrophic cardiomyopathy. Flow reversal might be related to the degree of left ventricular asymmetry and compression of the septal perforator arteries.

Validation of volumetric flow measurements by means of a Doppler-tipped coronary angioplasty guide wire

We used an in vitro model to validate volumetric flow measurements obtained with an 0.018-inch angioplasty guidewire with a 12 MHz transducer mounted on its tip. By using a modified two-head roller pump device, flow was adjusted incrementally from a minimum of 90 ml/min to a maximum of 550 ml/min. Flow was measured with the Doppler guide wire in tubing ranging from 1.9 mm to 6.0 mm internal diameter, as the product of the spectral Doppler velocity integral and the cross-sectional area of the tubing, over a 1-minute period. It was an excellent correlation between the Doppler calculated flow rates and actual flow, regardless of tubing diameter (r = 0.99). These results suggest that the Doppler spectral output of this device might be accurately applied to estimates of volumetric flow in human coronary arteries.

Noninvasive assessment of coronary flow dynamics before and after coronary angioplasty using transesophageal Doppler

Recent invasive studies using intracoronary Doppler catheters or guide wires reported improved coronary flow dynamics after successful percutaneous transluminal coronary angioplasty. Transesophageal Doppler enables the measurement of coronary flow velocities within the left anterior descending artery. The present study was designed to test: (1) whether transesophageal Doppler may detect coronary flow velocity changes in patients undergoing angioplasty for left anterior descending artery stenosis, and (2) whether this technique may help to evaluate non-invasively the results of the procedure. Twenty-three patients undergoing angioplasty of the left anterior descending artery were studied by transesophageal Doppler before and < or = 24 hours after the interventional procedure. Coronary flow velocities were measured in the proximal part of the left anterior descending artery with the use of pulsed Doppler guided by color flow imaging. The degree of stenosis was measured by computerized quantitative coronary arteriography. Coronary flow velocity signals were successfully obtained in 19 of 23 patients (83%). In 16 successful angioplasty procedures, peak diastolic velocity increased from 37 +/- 14 cm/s before angioplasty to 51 +/- 16 cm/s after (p = 0.0001). In the 3 patients in whom angioplasty was unsuccessful, transesophageal Doppler showed no significant increase in peak diastolic coronary flow velocity. In a total of 19 angioplasty procedures, a good linear relation was found between the percent changes in coronary flow diastolic velocity and the reduction in the degree of stenosis (r = 0.85; p = 0.0001). All patients with > 20% increase in peak diastolic velocity had > 40% stenosis reduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive assessment of left internal mammary artery graft patency using duplex Doppler echocardiography from supraclavicular fossa

OBJECTIVES

The purpose of this study was to clarify the usefulness of duplex Doppler echocardiography from the supraclavicular fossa for assessment of left internal mammary artery graft patency.

BACKGROUND

A noninvasive method to assess coronary artery bypass graft patency would be useful for clinical diagnosis and long-term follow-up of graft outcome.

METHODS

Duplex Doppler echocardiography from the supraclavicular fossa was performed in 56 consecutive patients who underwent postoperative cardiac catheterization studies, including quantitative angiography. All patients underwent coronary artery bypass graft surgery using the left internal mammary artery graft to the left anterior descending coronary artery.

RESULTS

The left internal mammary artery graft and its flow were detected in 55 (98%) of the 56 patients with duplex Doppler echocardiography from the supraclavicular fossa. According to the quantitative angiographic data, the patients were assigned to three groups: group A (36 patients) with a normal left internal mammary artery graft (< 50% diameter stenosis), group B (9 patients) with intermediate (50% to 75% diameter) graft stenosis and group C (10 patients) with severe (> 75% diameter) graft stenosis. The diastolic/systolic peak velocity ratio was smaller in group C than in groups A and B (p < 0.05), but there was no significant difference between groups A and B. A diastolic/systolic peak velocity ratio < 0.6 predicted severe left internal mammary artery graft stenosis (> 75% diameter stenosis) with a sensitivity and specificity of 100% and 80%, respectively. The diastolic fraction of time-velocity integral was smaller in group C than in groups A and B (p < 0.05), but there was no significant difference between groups A and B. A diastolic fraction < 0.5 predicted significant left internal mammary artery graft stenosis (> 75% diameter stenosis) with a sensitivity and specificity of 90% and 100%, respectively.

CONCLUSIONS

Duplex Doppler echocardiography from the supraclavicular fossa is useful for noninvasive assessment of left internal mammary artery graft patency.

Relation of phasic coronary flow velocity profile to clinical and hemodynamic characteristics of patients with aortic valve disease

BACKGROUND

Our objective was to assess phasic coronary blood flow and velocity characteristics of the proximal portion of the left anterior descending artery and to evaluate their relation to the clinical and hemodynamic manifestations in patients with aortic valve disease.

METHODS AND RESULTS

We examined 26 patients with chronic aortic regurgitation (AR), 12 patients with predominant aortic stenosis (AS), and 11 control subjects using an intravascular Doppler catheter with spectral analysis. Angiographic assessment of AR identified 10 patients with mild regurgitation and 16 with severe regurgitation. The resting systolic coronary flow velocity-time integral (VTI) was significantly higher and the diastolic VTI was slightly but significantly higher in patients with severe regurgitation than in those with mild regurgitation (11.8 +/- 4.2 vs 4.1 +/- 1.1 cm, P < .001; 18.5 +/- 5.8 vs 13.2 +/- 3.2 cm, P < .05) and control subjects (4.0 +/- 1.0 cm, P < .001 and 13.3 +/- 3.6 cm, P < .05), respectively. Patients with AS had a slightly lower resting systolic VTI (3.8 +/- 1.4 cm) and a higher diastolic VTI (14.6 +/- 3.7 cm) than control subjects. Resting coronary blood flow was greater in patients with aortic valve disease than in control subjects. There was a significant correlation between the ratio of the resting systolic to diastolic VTI (S/D ratio) and the ratio of the aortic systolic to diastolic pressure (r = .75, P < .001) in patients with AR. The S/D ratio was inversely correlated with left ventricular systolic pressure (r = -.92, P < .001) and positively correlated with the ratio of the aortic systolic to diastolic pressure (r = .68, P < .05) in patients with AS.

CONCLUSIONS

Our results indicate that hemodynamic changes related to aortic valve disease contribute to alterations in the resting phasic coronary blood flow and velocity profiles observed in these patients.

Flow velocity quantification in human coronary arteries with fast, breath-hold MR angiography

Measurement of coronary artery flow velocities has, until now, largely required the use of invasive technologies. The authors have implemented a breath-hold magnetic resonance (MR) angiography technique for depicting the coronary arteries and for quantifying flow velocities. The method was tested in flow phantoms and then applied to a series of subjects: 11 subjects were studied at rest, and four were studied before and during pharmacologic stress induced by intravenous adenosine. Flow velocities at rest in the midportion of the right coronary artery were 9.9 cm/sec +/- 3.5 (n = 12); in the proximal left anterior descending coronary artery, they were significantly higher, measuring 20.5 cm/sec +/- 5.2 (n = 6). With adenosine, flow velocities typically increased at least fourfold. The authors conclude that noninvasive measurement of coronary artery flow velocities is feasible with MR angiography; this method may prove useful for determining the physiologic significance of coronary artery stenosis.

Application of intracoronary flow velocity for detection and management of ostial saphenous vein graft lesions

Ostial lesions of saphenous vein grafts can be difficult to assess by angiography. A physiologic approach to the selection and recanalization of ostial lesions in saphenous vein grafts may be advantageous to overcome limitations of angiography. To assist in identifying favorable physiology and facilitate procedural decision making, the use of coronary flow velocity measurements with a Doppler-tipped 0.018-inch angioplasty flowire in three particularly difficult patients with varying types of saphenous vein graft aorto-ostial narrowings is reported.

Quantitative demonstration of dipyridamole-induced coronary steal and alteration by angioplasty in man: analysis by simultaneous, continuous dual Doppler spectral flow velocity

In the course of studying the effects of coronary angioplasty on branch vessel flow using two Doppler flow velocity guidewires, we quantitated simultaneous blood flow responses proximal and distal to a stenosis. The alterations of flow documented a horizontal epicardial steal induced during dipyridamole hyperemia, hyperemic flow reversal by intravenous aminophylline, and subsequent normalization of distal hyperemia after endoluminal enlargement by successful angioplasty. The quantitative physiology of the patient described here confirms one postulated mechanism of abnormal myocardial perfusion stress scintigraphy. Continuous dual flowire spectral coronary flow determinations appear to be a valuable method in verifying postulated mechanisms of various pharmacologic and mechanical stimuli influencing coronary blood flow in patients with atherosclerotic coronary artery disease.

Assessing the hemodynamic significance of coronary artery stenoses: analysis of translesional pressure-flow velocity relations in patients

OBJECTIVES

The purpose of this study was to examine the relation among the angiographic severity of coronary artery lesions, coronary flow velocity and translesional pressure gradients.

BACKGROUND

Determination of the clinical and hemodynamic significance of coronary artery stenoses is often difficult and inexact. Angiography has been shown to be an imperfect tool for determining the physiologic significance of eccentric or irregular coronary lumen narrowing.

METHODS

Using a 0.018-in. (0.046 cm) intracoronary Doppler-tipped angioplasty guide wire, spectral flow velocity data both proximal and distal to coronary stenoses were compared with translesional pressure gradient measurements and angiographic data obtained during cardiac catheterization in 101 patients. There were 17 patients with normal angiographic findings and 84 with coronary artery disease, with lesions ranging from 28% to 99% diameter narrowing. Patients with coronary disease were assigned to two groups on the basis of translesional gradients at rest. Group A (n = 56) had gradients < 20 mm Hg, and Group B (n = 28) had gradients > or = 20 mm Hg.

RESULTS

Proximal average peak velocity, diastolic velocity integral and total velocity integral were slightly but statistically lower in Group A; however, the distal average peak velocity and diastolic and total velocity integrals were all markedly (all p < 0.01) decreased in patients with gradients > or = 20 mm Hg (Group B). In addition, the ratio of proximal to distal total flow velocity integral was higher in Group B (2.4 +/- 1.0) than in group A (1.1 +/- 0.3, p < 0.001). There was a strong correlation between translesional pressure gradients and the ratios of the proximal to distal total flow velocity integrals (r = 0.8, p < 0.001), with a weaker relation between quantitative angiography and pressure gradients (r = 0.6, p < 0.001). In angiographically intermediate stenoses (range 50% to 70%), angiography was a poor predictor of translesional gradients (r = 0.2, p = NS), whereas the flow velocity ratios continued to have a strong correlation (r = 0.8, p < 0.001). Only two patients with a proximal/distal total flow velocity ratio < 1.7 had a translesional gradient > 30 mm Hg. Both patients had a very proximal lesion in a nonbranching right coronary artery.

CONCLUSIONS

These data demonstrate that in branching human coronary arteries, a close relation exists between translesional hemodynamics and distal coronary flow velocity. Translesional coronary flow velocity is a new and easily applicable method for determining the hemodynamic significance of coronary artery stenoses that is superior to angiography and can be applied at the time of diagnostic catheterization. These data will provide a rational approach to making decisions on the use of coronary interventional techniques when angiographic findings are questionable.

Use of the Doppler guide wire for intraluminal diagnosis to facilitate coronary intervention

The FloWire Doppler flow guide wire has recently been approved for intracoronary application, joining angioscopy and intravascular ultrasonography as new methods for transluminal evaluation of coronary lesions. The 0.018-inch FloWire provides a high-fidelity continuous Doppler signal. Velocity measurements are continuously displayed on the FloMap monitor in a gray-scale spectral pattern, providing quantitation of an entire spectral distribution of flow velocities. This torquable, steerable guide wire can be used in small and distal branches of the coronary tree. We describe the clinical use of the FloWire Doppler guide wire in three patients who had coronary anatomic abnormalities that could not be assessed by other techniques. In each case the Doppler guide wire facilitated analysis of the physiologic significance of the coronary stenosis. The information gained was crucial in selecting safe and effective treatment for these patients.

Sensitivity and reproducibility of the instantaneous hyperemic flow versus pressure slope index compared to coronary flow reserve for the assessment of stenosis severity

The objective of this study was to compare the reproducibility and sensitivity of the instantaneous hyperemic flow versus pressure slope index (i-HFVP) and coronary flow reserve (CFR). The i-HFVP is the slope of the relationship between diastolic hyperemic coronary flow and diastolic aortic pressure, normalized for bed weight. In contrast to CFR (the ratio of hyperemic to basal coronary flow), the i-HFVP has been shown to be independent of changes in aortic pressure, heart rate, contractility, and preload. To compare reproducibility, i-HFVP and CFR were measured three times in eight dogs instrumented with high-fidelity micromanometers and flow probes, allowing for full hemodynamic recovery between phases (15 to 40 minutes). Maximum hyperemia was induced with intravenous adenosine. The sensitivity of i-HFVP and CFR was assessed in 16 instrumented dogs. Measurements were performed for one basal state and for five subcritical incremental stenoses created with a screw occluder during hyperemia. Intraclass variability correlation coefficients were 0.96 for i-HFVP but only 0.56 for CFR. Both i-HFVP and CFR showed significant decrements with each increasing stenosis. However, the percentage reductions at each level were significantly greater for the i-HFVP. The difference in percentage reduction favoring increased sensitivity of the i-HFVP ranged from 11% to 23%. It was concluded that the i-HFVP is more reproducible and more sensitive to the presence of stenoses than CFR.

Use of translesional coronary flow velocity for interventional decisions in a patient with multiple intermediately severe coronary stenoses

Translesional pressure gradients are currently not performed routinely for most angioplasty procedures because of the technical limitations. With the use of an 0.18 inch Doppler flow velocity guidewire, coronary flow velocity, both proximal and distal to a lesion, can be easily assessed. In branching arteries, significant lesions are characterized by a ratio of proximal to distal flow velocity of > 1.7, loss of the normal phasic diastolic predominant flow velocity pattern, and/or loss of distal hyperemia. We describe the use of coronary flow velocity in assisting important decision making in a young patient with a recent myocardial infarction and multiple coronary lesions. The decision for angioplasty of the hemodynamically significant stenosis was confirmed by translesional flow velocity measurements. A rational approach to coronary intervention in patients with multiple stenoses of intermediate severity appears to be facilitated by direct measurement of translesional flow dynamics.

Coronary flow velocity dynamics in normal and diseased arteries

Distal coronary flow velocity measurements were previously limited to open heart or experimental procedures. Unlike previous Doppler catheter techniques, a Doppler angioplasty flow wire permits flow velocity measurements in both the proximal and distal segments of normal and diseased coronary arteries. In order to determine the potential clinical application of the Doppler flow wire, we performed baseline and hyperemia flow velocity measurements in proximal and distal segments of 20 angiographically normal arteries (right coronary = 8; left circumflex = 7; left anterior descending = 5) and 29 significantly stenosed arteries. All 3 normal coronary arteries had a diastolic-predominant pattern in both proximal and distal segments; the right coronary artery showed significantly less diastolic predominance. The coronary vasodilator reserve was similar in all three normal coronary arteries, and in the proximal and distal arterial segments. Abnormal arteries had significantly lower coronary vasodilator reserve (normal vs abnormal, 2.3 +/- 0.8/1.6 +/- 0.7; p < 0.02). Normal arteries had preservation of velocity parameters in the distal segments; abnormal arteries had a significant decrease in distal velocity parameters. The proximal-to-distal velocity ratio was thus significantly higher in abnormal arteries (2.4 +/- 0.7 vs 1.1 +/- 0.2; p < 0.001). The coronary vasodilator reserve in proximal and distal arteries--in addition to the proximal to distal velocity ratio--may provide functional and hemodynamic data complementary to coronary angiography in the assessment of coronary artery stenosis.

Coronary artery flow monitoring following coronary interventions

Technologic innovations have made it possible to measure coronary artery blood flow in awake patients. Both flow velocity as well as flow reserve can be assessed. In particular, the period of time immediately following coronary interventions offers a unique opportunity to study important features of coronary flow behavior. In 22 patients, coronary flow reserve was measured before and after an intervention, either angioplasty or atherectomy, using a 0.018-in Doppler guidewire (Flowire). The minimum lumen diameter (MLD) was increased from 1.0 +/- 0.4 to 1.7 +/- 0.4 mm, while coronary flow velocity increased significantly, rising from 29 +/- 13 to 39 +/- 14 cm/sec (p < 0.025). The maximum hyperemic velocity also increased, from 44 +/- 16 to 69 +/- 21 cm/sec. Using only the preintervention or postintervention values, the flow reserve ratio was 1.53 +/- 0.4 prior to intervention and 1.84 +/- 0.5 after intervention (p = nonsignificant). However, the post-intervention value may have been artifactually reduced by the fact that both resting as well as hyperemic velocities increased. When the post-intervention flow reserve ratio was recalculated, using the preintervention resting value, flow reserve ratio was seen in increase from 1.53 +/- 0.4 to 2.73 +/- 1.2 (p < 0.001). Measurements of coronary flow in the postintervention period also revealed several interesting phenomena. Spasm of a coronary artery was documented, and its resolution in response to intracoronary nitroglycerin was observed. Elastic recoil following angioplasty was documented by gradual decline in coronary flow over 30 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitating coronary collateral flow velocity in patients during coronary angioplasty using a Doppler guidewire

Quantitation of coronary collateral flow in patients has been limited to angiographic techniques, which are subject to well-known methodologic limitations. The use of a Doppler-tipped angioplasty guidewire permits measurement of both antegrade and retrograde flow distal to totally or subtotally occluded vessels that may be supplied with acutely recruitable or angiographically mature collateral conduits. Using coronary flow velocity as an indicator of collateral flow, retrograde flow velocity was quantitated in 17 patients. Mean collateral flow velocity was approximately 30% of normal postangioplasty antegrade flow velocity. The phasic pattern of collateral flow was highly variable, but the retrograde diastolic and systolic flow velocity integrals were 20% and 40% (respectively) of post-procedure antegrade flow velocity. Preliminary studies with pharmacologic stimulation of the contralateral supply artery suggests that collateral flow is not increased by intracoronary nitroglycerin (200 micrograms) or adenosine (12 micrograms), but may be markedly augmented during mechanical stimulation of balloon occlusion. These data represent the first in a series of quantitative observations on control of the coronary collateral circulation in humans. Future investigations using the Doppler Flowire (Cardiometrics) will enhance understanding of factors modulating ischemia through collateral supply.

Maximal blood flow velocity in severe coronary stenoses measured with a Doppler guidewire. Limitations for the application of the continuity equation in the assessment of stenosis severity

In vitro and animal experiments have shown that the severity of coronary stenoses can be assessed using the continuity equation if the maximal blood flow velocity of the stenotic jet is measured. The large diameter and the low range of velocities measurable without frequency aliasing with the conventional intracoronary Doppler catheters precluded the clinical application of this method for hemodynamically significant coronary stenoses in humans. This article reports the results obtained using a 12 MHz steerable angioplasty guidewire in a consecutive series of 52 patients undergoing percutaneous coronary angioplasty (61 coronary stenoses). The ratio between coronary flow velocity in a reference segment and in the stenosis was used to estimate the percent cross-sectional area stenosis. A Doppler recording suitable for quantitation was obtained in the stenotic segment in only 10 of 61 arteries (16%). The time-averaged peak velocity increased from 15 +/- 5 to 115 +/- 26 cm/sec from the reference normal segment to the stenosis. Volumetric coronary flow calculated from the product of mean flow velocity and cross-sectional area was similar in the stenosis and in the reference segment (33.2 +/- 14.9 vs 33.5 +/- 17.0 mL/min, respectively, difference not significant). The percent cross-sectional area stenosis and minimal luminal cross-sectional area derived from the Doppler velocity measurements using the continuity equation and calculated with quantitative angiography were also similar (Doppler, 86.7 +/- 5.1% and 1.00 +/- 0.48 mm2; quantitative angiography, 85.9 +/- 7.9% and 1.02 +/- 0.50 mm2).(ABSTRACT TRUNCATED AT 250 WORDS)

Combined physiologic and anatomic assessment of percutaneous revascularization using a Doppler guidewire and ultrasound catheter

Previous investigations have established the utility of intravascular ultrasound (IVUS) examination for the evaluation of arterial dimensions and qualitative changes following percutaneous revascularization. More recently, the feasibility of obtaining intravascular physiology findings before and/or after percutaneous revascularization by use of an intravascular Doppler Flowire (Cardiometrics) has been demonstrated. Accordingly, we investigated the feasibility of using this combined physiologic/anatomic approach to evaluate individuals undergoing percutaneous revascularization of stenotic or occluded coronary and peripheral arteries. A total of 76 patients were evaluated using the Flowire to guide an IVUS catheter. Revascularization of coronary and peripheral vascular stenoses and/or occlusions was achieved in these patients by balloon angioplasty, directional atherectomy, excimer laser angioplasty, and thrombolytic therapy, alone or in combination. Physiologic findings obtained with the Flowire reinforced conclusions regarding morphologic severity of candidate stenoses and anatomic adequacy of revascularization following IVUS examination. In certain ambiguous cases, information gained by one modality clarified information obtained with the other. Finally, one modality may also serve as an alternative when logistics preclude the serial use of both. The preliminary experience obtained in this feasibility trial confirmed that IVUS and the Flowire may be combined to assess both candidate lesions as well as postprocedural patency in patients undergoing percutaneous revascularization. The combination of anatomic and physiologic data available from IVUS and Flowire provides a far more sensitive and possibly more accurate analysis of the adequacy of revascularization than has been possible by angiography alone. The extent to which such a detailed investigation is required to optimize interventional therapy on a routine basis is the subject of subsequent investigations.