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

Fractional flow reserve, absolute and relative coronary blood flow velocity reserve in relation to the results of technetium-99m sestamibi single-photon emission computed tomography in patients with two-vessel coronary artery disease

OBJECTIVES

We sought to perform a direct comparison between perfusion scintigraphic results and intracoronary-derived hemodynamic variables (fractional flow reserve [FFR]; absolute and relative coronary flow velocity reserve [CFVR and rCFVR, respectively]) in patients with two-vessel disease.

BACKGROUND

There is limited information on the diagnostic accuracy of intracoronary-derived variables (CFVR, FFR and rCFVR) in patients with multivessel disease.

METHODS

Dipyridamole technetium-99m sestamibi (MIBI) single-photon emission computed tomography (SPECT) was performed in 127 patients. The presence of reversible perfusion defects in the region of interest was determined. Within one week, angiography was performed; CFVR, rCFVR and FFR were determined in 161 coronary lesions after intracoronary administration of adenosine. The predictive value for the presence of reversible perfusion defects on MIBI SPECT of CFVR, rCFVR and FFR was evaluated by the area under the curve (AUC) of the receiver operating characteristics curves.

RESULTS

The mean percentage diameter stenosis was 57% (range 35% to 85%), as measured by quantitative coronary angiography. Using per-patient analysis, the AUCs for CFVR (0.70 +/- 0.052), rCFVR (0.72 +/- 0.051) and FFR (0.76 +/- 0.050) were not significantly different (p = NS). The percentages of agreement with the results of MIBI SPECT were 76%, 78% and 77% for CFVR, rCFVR and FFR, respectively. Per-lesion analysis, using all 161 measured lesions, yielded similar results.

CONCLUSIONS

The diagnostic accuracy of three intracoronary-derived hemodynamic variables, as compared with the results of perfusion scintigraphy, is similar in patients with two-vessel coronary artery disease. Cut-offvalues of 2.0 for CFVR, 0.65 for rCFVR and 0.75 for FFR can be used for clinical decision-making in this patient cohort. Discordant results were obtained in 23% of the cases that require prospective evaluation for appropriate patient management.

Intravascular ultrasound findings in patients with abnormal coronary flow reserve after stenting

A coronary flow reserve (CFR) of 2.0 has been advocated as the endpoint for coronary intervention therapy. Experience shows, however, that CFR does indeed exceed 2.0 in many cases poststenting, while remaining below 2.0 in others. In this study, we assessed the clinical characteristics and IVUS findings of patients whose CFR remained below 2.0 after stent implantation, specifically 16 patients with CFR below 2.0 (22 lesions, 64 +/- 9 years, 4 female), and 102 patients with CFR above 2.0 (112 lesions, mean age 66 +/- 11 years, 22 female). Patient population comprised patients selected for retrospective study, but participants were selected on the basis of matching patient and lesion characteristics. The IVUS findings showed that incidence of calcified lesions and post-PTCA dissection of hard plaque were higher among patients with CFR < 2.0. Further, IVUS-obtained vascular measurements showed post-PTCA area stenosis to be 58.7 +/- 15.2% in the CFR < 2.0 group, and 45.3 +/- 12.5% among CFR > or = 2.0 patients (P < 0.05). These findings indicate that patients with diffuse calcified lesions or high post-PTCA % area stenosis, as determined by IVUS, are more likely to have lower CFR after stenting.

Physiologic assessment of coronary artery stenosis by coronary flow reserve measurements with transthoracic Doppler echocardiography: comparison with exercise thallium-201 single piston emission computed tomography

OBJECTIVES

We evaluated the value of coronary flow reserve (CFR), as determined by transthoracic Doppler echocardiography (TTDE), for physiologic assessment of coronary artery stenosis severity, and we compared TTDE measurements with those obtained by exercise thallium-201 (Tl-201) single-photon emission computed tomography (SPECT).

BACKGROUND

Coronary flow reserve measurements by TTDE have been reported to be useful for assessing angiographic left anterior descending coronary artery (LAD) stenosis. However, discrepancies exist between angiographic and physiologic estimates of coronary lesion severity.

METHODS

We studied 36 patients suspected of having coronary artery disease. The flow velocity in the distal LAD was measured by TTDE both at rest and during intravenous infusion of adenosine. Coronary flow reserve was calculated as the ratio of hyperemic to basal peak (peak CFR) and mean (mean CFR) diastolic flow velocities. The CFR measurements by TTDE were compared with the results of Tl-201-SPECT.

RESULTS

Complete TTDE data were acquired for 33 of 36 study patients. Of these 33 patients, Tl-201-SPECT confirmed reversible perfusion defects in the LAD territories in 12 patients (group A). Twenty-one patients had normal perfusion in the LAD territories (group B). Peak CFR and mean CFR (mean value +/- SD) were 1.5 +/- 0.6 and 1.5 +/- 0.7 in group A and 2.8 +/- 0.8 and 2.7 +/- 0.7 in group B, respectively. Both peak and mean CFR < or = 2.0 predicted reversible perfusion defects, with a sensitivity and specificity of 92% and 90%, respectively.

CONCLUSIONS

Noninvasive measurement of CFR by TTDE provides data equivalent to those obtained by Tl-201-SPECT for physiologic estimation of the severity of LAD stenosis.

Role of variability in microvascular resistance on fractional flow reserve and coronary blood flow velocity reserve in intermediate coronary lesions

BACKGROUND

Fractional flow reserve (FFR) and coronary blood flow velocity reserve (CFR) represent physiological quantities used to evaluate coronary lesion severity and to make clinical decisions. A comparison between the outcomes of both diagnostic techniques has not been performed in a large cohort of patients with intermediate coronary lesions.

METHODS AND RESULTS

FFR and CFR were assessed in 126 consecutive patients with 150 intermediate coronary lesions (between 40% and 70% diameter stenosis by visual assessment). Agreement between outcomes of FFR and CFR, categorized at cut-off values of 0.75 and 2.0, respectively, was observed in 109 coronary lesions (73%), whereas discordant outcomes were present in 41 lesions (27%). In 26 of these 41 lesions, FFR was <0.75 and CFR>or=2.0 (group A); in the remaining 15 lesions, FFR was >or=0.75 and CFR<2.0 (group B). Minimum microvascular resistance, defined as the ratio of mean distal pressure to average peak blood flow velocity during maximum hyperemia, showed a large variability (overall range, 0.65 to 4.64 mm Hg x cm(-1) x s(-1)) and was significantly higher in group B than in group A (2.42+/-0.77 versus 1.91+/-0.70 mm Hg x cm(-1) x s(-1); P:=0.034).

CONCLUSIONS

Our findings demonstrate the prominent role of microvascular resistance in modulating the relationship between FFR and CFR and emphasize the importance of combined pressure and flow velocity measurements to evaluate coronary lesion severity and microvascular involvement.

Coronary flow reserve: measurement with transthoracic Doppler echocardiography is reproducible and comparable with positron emission tomography

Detection of early vascular changes indicated by lowered coronary flow reserve (CFR) would allow early treatment and prevention of atherosclerosis. The purpose of this study was to test whether it is possible to reproducibly measure CFR with transthoracic Doppler echocardiography (TTE) in healthy volunteers. We measured CFR using dipyridamole infusion in ten healthy male volunteers with two methods: TTE and positron emission tomography (PET) with oxygen-15-labelled water (group A). However, CFR was assessed twice with TTE in eight healthy male volunteers (group B) to study the reproducibility of this method. We compared CFRs obtained using TTE flow measurements in the left anterior descending coronary artery (LAD) and PET flow measurements in the corresponding myocardial area. Coronary flow in LAD could be measured in all subjects using TTE. By TTE, an average CFR based on peak diastolic flow velocity (PDV) was 2.72 +/- 1.16, mean diastolic flow velocity (MDV) 2.56 +/- 1.06 and velocity time integral (VTI) 1.87 +/- 0.49. The results were reproducible in two repeated TTE studies (coefficient of variation in MDV 6.1 +/- 4.3%, n=8). By PET, CFR was 2.52 +/- 0.84. CFR assessed by TTE correlated closely with that measured by PET (MDV r=0.942, P<0.001; PDV r=0.912, P<0.002 and VTI r=0.888, P<0.006) and intraclass correlation was 0.929 (MDV) and tolerance limits for differences of CFRs was -0.78 to 0.72. We show that CFR measured by TTE has an excellent correlation with CFR measured by PET. We also found that TTE measurements of CFR were highly reproducible.

Myocardial perfusion in patients with permanent ventricular pacing and normal coronary arteries

OBJECTIVES

The purposes of this study were to test the specificity of dipyridamole myocardial perfusion scintigraphy in patients with permanent ventricular pacing (PVP) and to evaluate coronary blood flow and reserve in these patients.

BACKGROUND

Permanent ventricular pacing is associated with exercise perfusion defects on myocardial scintigraphy in the absence of coronary artery disease (CAD). On the basis of studies in patients with left bundle brunch block, coronary vasodilation with dipyridamole has been proposed as an alternative to exercise testing for detecting CAD in paced patients, but this approach has never been tested.

METHODS

Fourteen patients with a PVP and normal coronary arteries underwent stress thallium-201 scintigraphy and cardiac catheterization. In these patients and in eight control subjects, coronary flow velocities were measured in the left anterior descending coronary artery (LAD) and in the dominant coronary artery before and after adenosine administration.

RESULTS

In the paced patients, coronary flow velocities in the LAD and in the dominant coronary artery were significantly lower than those in the control subjects. In addition, seven patients showed perfusion defects on dipyridamole thallium-201 single-photon emission computed tomography, with a specificity of 50% for this test. The defect-related artery in these patients had lower coronary flow reserve (2.6 +/- 0.5) as compared with those without perfusion defects (3.9 +/- 1.0, p < 0.05) or the control group (3.5 +/- 0.5, p < 0.05).

CONCLUSIONS

Permanent ventricular pacing is associated with alterations in regional myocardial perfusion. Furthermore, abnormalities of microvascular flow, as indicated by reduced coronary flow reserve in the defect-related artery, are at least partially responsible for the uncertain specificity of dipyridamole myocardial perfusion scintigraphy.

Intermediate coronary artery stenosis: evidence-based decisions in interventions to avoid the oculostenotic reflex

The prevalence of intermediate coronary artery stenosis (defined as a diameter stenosis of 40% to 70%) is quite large in patients undergoing PTCA. The coronary angiogram is considered the 'gold standard' for the definition of coronary anatomy, in spite of various limitations associated with its use. In recent years, sensor tipped guidewire based methods of physiologic assessment of stenosis severity, like myocardial fractional flow reserve, and poststenotic coronary flow reserve had established their role in the decision making in catheterization laboratory. The decision making should combine morphologic and physiologic assessment as better evidence based approach in guiding therapy to avoid the 'oculostenotic reflex'.

Technical achievement: transthoracic Doppler echocardiography can be used to detect LAD restenosis after coronary angioplasty

We investigated the capability of transthoracic Doppler echocardiography (TTE) to detect and quantify the severity of restenosis in the left anterior descending coronary artery (LAD) after percutaneous transluminal coronary angioplasty (PTCA). We studied 10 consecutive patients assigned for quantitative coronary angiography (qCA) due to a recurrent angina pectoris after PTCA of the LAD. The LAD was visualized by TTE, and the presence of local turbulence and an increase in the blood flow velocity was regarded to indicate coronary stenosis. To assess the severity of the stenosis, the increase of blood flow velocity was measured. Angiography showed stenoses of various degrees (27-100%) in all patients. All stenoses were detectable using TTE. Moreover, the ratio of maximal blood flow velocity at the site of stenosis to the pre-stenotic blood flow velocity (M/P-ratio) correlated significantly with the reduction of the luminal diameter of LAD (r = 0.85, P < 0.003). A M/P-ratio higher than 3.0 predicted a diameter reduction of 50% or higher with sensitivity and specificity of 100% in patients with a subtotal stenosis (n = 9). Our results indicate that stenoses in the LAD could be found and the severity of the stenoses could be quantified reliably with TTE. This approach is totally non-invasive and less expensive than coronary angiography and can be used clinically in clarifying restenosis after coronary angioplasty.

Coronary flow reserve is reflective of myocardial perfusion status in acute anterior myocardial infarction

Our objective was to determine whether coronary vasodilatory reserve (CVR) correlates with the perfusion state of infarct zone in early recovery phase of acute anterior myocardial infarction (AMI). We studied 14 patients (11 males; mean age, 46 years) who had AMI and 6 control subjects who had chest pain but normal coronary angiograms. All patients underwent successful percutaneous revascularization of left anterior descending (LAD) coronary artery. Coronary flow velocity was measured using intracoronary (IC) Doppler at baseline and following IC injection of 18 microg of adenosine. Myocardial perfusion was evaluated by myocardial contrast echocardiography (MCE). CVR was higher in patients without a perfusion defect on MCE than in those with (2.48 +/- 0.21 vs. 1.66 +/- 0.13, P = 0.001). Subjects with a perfusion defect had a lower CVR than controls (1.66 +/- 0.13 vs.2.40 +/- 0.18, P < 0.05). CVR was > 2.0 in all subjects without a perfusion defect. There was a strong correlation between the magnitude of myocardial opacification in the LAD territory and CVR (r = 0.80, P < 0.01). Increase in peak diastolic flow velocity after adenosine infusion, but not systolic flow velocity, correlated with myocardial opacification index (r = 0.63, P = 0.016). CVR of infarct-related artery correlated closely with the perfusion status of the myocardium in infarct zone and those with a CVR > 2.0 had normal myocardial perfusion. These data suggest that CVR may be used to determine the perfusion state of the myocardium in the infarct zone, which is a known predictor of myocardial viability. Cathet. Cardiovasc. Intervent. 51:281-286, 2000.

Assessment of coronary flow reserve using fast velocity-encoded cine MR imaging: validation study using positron emission tomography

OBJECTIVE

Previous studies using intravascular Doppler sonography and positron emission tomography (PET) have shown that the hemodynamic significance of coronary artery stenosis can be evaluated by measuring coronary flow reserve. The purpose of this study was to assess whether MR imaging measurements of coronary flow reserve in the left anterior descending artery are comparable with those obtained with PET in the corresponding territory.

SUBJECTS AND METHODS

MR imaging and PET flow measurements were obtained in 10 healthy volunteers. Blood flow velocity in the left anterior descending artery was measured with breath-hold velocity-encoded cine MR imaging before and after IV administration of dipyridamole. The coronary flow velocity reserve measured by MR imaging was compared with the myocardial perfusion reserve in the anterior myocardium quantified on using PET and (15)O-labeled water.

RESULTS

The average flow velocity reserve in the left anterior descending artery measured on MR imaging was 2.44+/-1.14 in healthy volunteers, which was comparable with the myocardial perfusion reserve measured by PET (2.52+/-0.84). MR imaging and PET measurements of the coronary flow reserve showed a significant correlation (r = 0.79, p<0.01).

CONCLUSION

MR imaging measurement of the flow velocity reserve in the proximal left anterior descending artery correlates well with the myocardial perfusion reserve obtained with PET and (15)O-labeled water.

Coronary flow velocity immediately after primary coronary stenting as a predictor of ventricular wall motion recovery in acute myocardial infarction

OBJECTIVES

The purpose of this study was to examine the relationship between the pattern of coronary blood flow velocity immediately after successful primary stenting and the recovery of left ventricular (LV) wall motion in patients with acute myocardial infarction (AMI).

BACKGROUND

It is difficult to predict the recovery of LV wall motion immediately after direct angioplasty in AMI. Recent reports indicate that dysfunctional coronary microcirculation is an important determinant of prognosis for AMI patients after successful reperfusion.

METHODS

We measured left anterior descending coronary flow velocity variables using a Doppler guide wire immediately after successful primary stenting in 31 patients with their first anterior AMI. The patients were divided into two groups: those with and those without early systolic reverse flow (ESRF). Changes in LV regional wall motion (RWM) and ejection fraction (EF) at admission and at discharge were compared between the two groups. Coronary flow velocity variables immediately after primary stenting were compared with changes in left ventriculographic indexes.

RESULTS

The change in RWM was significantly greater in the non-ESRF group than it was in the ESRF group (0.9 +/- 0.7 vs. -0.1 +/- 0.3 standard deviation/chord, respectively, p < 0.001). The change in EF was also significantly greater in the non-ESRF group than it was in the ESRF group (10 +/- 10 vs. 1 +/- 6%, respectively, p < 0.05). In the non-ESRF group (diastolic to systolic velocity ratio [DSVR] <3.0), the DSVR correlated positively with the change in RWM (r = 0.60, p < 0.005, n = 24) and the change in EF (r = 0.52, p < 0.01).

CONCLUSIONS

The coronary flow velocity pattern measured immediately after successful primary stenting is predictive of the recovery of regional and global LV function in patients with AMI.

Assessment of coronary flow reserve with transthoracic Doppler echocardiography: comparison among adenosine, standard-dose dipyridamole, and high-dose dipyridamole

Coronary flow reserve (CFR), defined as a ratio of hyperemic-to-basal coronary flow velocity, provides important information about the functional aspect of coronary circulation. However, it usually is determined by invasive methods during catheterization. Recent studies have shown that transthoracic Doppler echocardiography (TTDE) may be useful in the measurement of coronary flow velocity in the distal portion of the left anterior descending coronary artery (LAD). The vasodilators used for hyperemia are adenosine and dipyridamole. However, the coronary vasodilative response and systemic hemodynamic effects of the two agents have not been directly compared with TTDE. We assessed blood flow velocity and vascular resistance in the distal LAD by TTDE during an intravenous 2-minute adenosine infusion (140 microg/kg/min) and low- (0.56 mg/kg) and high-dose dipyridamole (0. 84 mg/kg) infusion in 25 patients with patent LAD. Coronary flow velocity was successfully recorded in 20 patients (80%) during baseline and the consecutive vasodilator-infusion period. Compared with low-dose dipyridamole, adenosine infusion induced a higher CFR (3.7 +/- 0.87 vs 2.73 +/- 0.65; P <.05) and a lower coronary resistance index (0.31 +/- 0.04 vs 0.35 +/- 0.08; P <.05). But by increasing the dipyridamole dose to 0.84 mg/kg, the values of the CFR and coronary resistance index became comparable to those of adenosine infusion (2.85 +/- 0.78 vs 3.03 +/- 0.7, P = not significant [NS]; 0.33 +/- 0.04 vs 0.32 +/- 0.09, P = NS; respectively). We conclude that adenosine seems to be a favorable vasodilator for the measurement of CFR with TTDE.

Coronary physiology revisited : practical insights from the cardiac catheterization laboratory

Various coronary physiological measurements can be made in the cardiac catheterization laboratory using sensor-tipped guidewires; they include the measurement of poststenotic absolute coronary flow reserve, the relative coronary flow reserve, and the pressure-derived fractional flow reserve of the myocardium. Ambiguity regarding abnormal microcirculation has been reduced or eliminated with measurements of relative coronary flow reserve and fractional flow reserve. The role of microvascular flow impairment can be separately determined with coronary flow velocity reserve measurements. In addition to lesion assessment before and after intervention, emerging applications of coronary physiology include the determination of physiological responses to new pharmacological agents, such as glycoprotein IIb/IIIa blockers, in patients with acute myocardial infarction. Measurements of coronary physiology in the catheterization laboratory provide objective data that complement angiography for clinical decision-making.

Abnormal coronary flow velocity reserve after coronary artery stenting in patients: role of relative coronary reserve to assess potential mechanisms

BACKGROUND

Absolute coronary flow velocity reserve (CVR) after stenting may remain abnormal as a result of several different mechanisms. Relative CVR (rCVR=CVR(target)/CVR(reference)) theoretically normalizes for global microcirculatory disturbances and facilitates interpretation of abnormal CVR.

METHODS AND RESULTS

To characterize potential mechanisms of poststent physiology, CVR was measured using a Doppler-tipped angioplasty guidewire in 55 patients before and after angioplasty, after stenting, and in an angiographically normal reference vessel. For the group, the percent diameter stenosis decreased from 75+/-13% to 40+/-18% after angioplasty and to 10+/-9% (all P<0.05) after stent placement. After angioplasty, CVR increased from 1.63+/-0.71 to 1.89+/-0.55 (P<0.05) and after stent placement, to 2.48+/-0.75 (P<0.05 versus pre- and postangioplasty). After angioplasty, rCVR increased from 0.64+/-0.26 to 0.75+/-0.23 and after stent placement to 1.00+/-0.34. In 17 patients with CVR(stent) < or = 2.0, increased basal coronary flow, rather than attenuated hyperemia, was responsible in large part for the lower CVR(stent) compared with patients having CVR(stent) >2.0. In 8 patients with CVR(stent) <2.0, a normal rCVR supported global microvascular disease. The subgroup of 9 patients with CVR(stent) <2.0 and abnormal rCVR (16% of the studied patients) may require a pressure-derived fractional flow reserve to differentiate persistent obstruction from diffuse atherosclerotic disease or microvascular stunning.

CONCLUSIONS

Although a majority of patients after stenting normalize CVR for the individual circulation (ie, normal CVR or normal rCVR), in those with impaired CVR(stent), the analysis of coronary flow dynamics suggests several different physiological mechanisms. Additional assessment may be required to fully characterize the physiological result for such patients to exclude remediable luminal abnormalities.

MR measurement of coronary blood flow

The functional significance of coronary arterial stenosis can be evaluated by measuring the pharmacological flow reserve. Magnetic resonance (MR) imaging has a unique potential for noninvasive measurement of coronary blood flow and flow reserve in the native coronary artery and bypass graft. Restenosis after coronary balloon angioplasty and stenting in the left anterior descending artery can be detected noninvasively with serial MR measurements of the coronary flow reserve. Further refinement of the MR pulse sequences to improve spatial and temporal resolutions may permit accurate quantification of blood flow volume and flow reserve in all major coronary arterial branches. MR assessments of blood flow volume and flow pattern allow noninvasive detection of significant stenosis in the coronary artery bypass graft as well. By integrating MR blood flow measurement in the coronary sinus and cine MR assessment of left ventricular myocardial mass, altered myocardial micro-circulation in patients with diffuse myocardial diseases, such as hypertrophic cardiomyopathy and cardiac transplant, has been documented. J. Magn. Reson. Imaging 1999;10:728-733.

Prevalence of microvascular disease in patients with significant coronary artery disease

Coronary flow velocity reserve (CFVR) measurement using intracoronary Doppler techniques has been increasing accepted for the assessment of physiological significance of epicardial stenosis and the functional changes after coronary interventions. However, large discrepancy exists concerning the acute changes of CFVR immediately after intervention. The purpose of this study was to investigate the prevalence of microvascular dysfunction in patients with significant coronary artery disease. Intracoronary Doppler flow measurements were performed in a total of 212 patients who underwent coronary interventions because of significant epicardial stenosis using 0.014" Doppler flow wire (Cardiometrics, Inc, Mountain View, CA). Intracoronary bolus injection of adenosine (12 micrograms for the right coronary and 18 micrograms for the left coronary arteries) was used to induce hyperemic reaction. CFVR was registered as the ratio of average peak velocity during hyperemia (hAPV) to at baseline (bAPV). Successful coronary interventions either by percutaneous transluminal coronary balloon angioplasty (PTCA) or by stenting could significantly improve the CFVR. In 80 patients with PTCA, the bAPV elevated from 16.6 +/- 2.1 cm/s to 20.6 +/- 13.4 cm/s and hAPV from 30.1 +/- 15.9 cm/s to 45.2 +/- 17.7 cm/s (both p < 0.001) with PTCA and the CFVR increased from 1.94 +/- 0.78 to 2.58 +/- 0.87 correspondingly (p < 0.001). Significant elevation of coronary flow parameters were also found in 132 patients with subsequent stent implantation (bAPV from 15.3 +/- 6.7 cm/s to 18.7 +/- 9.1 cm/s, hAPV from 28.7 +/- 14.4 cm/s to 44.3 +/- 17.7 cm/s and CFVR from 1.90 +/- 0.70 to 2.59 +/- 0.87, all p < 0.001). Reduction of CFVR (< 3.0) after intervention still existed in 46 (61.3%) of 80 patients after PTCA and 88 (66.7%) of 132 patients after stenting. Moreover, CFVR < 3.0 were found in 50 (45.9%) of 109 reference vessels in patients with single vessel disease. Significant improvement of coronary flow velocity and coronary flow velocity reserve could be obtained after successful angioplasty. However, microvascualr dysfunction existed in a large proportion of patients either in normal reference vessels or in target vessels after interventions.

Coronary artery vasomotion and post-stenotic coronary artery blood flow after intracoronary lacidipine in patients with ischaemic heart disease: a pilot study

BACKGROUND

The calcium antagonist lacidipine has been shown to be highly vasoselective and to improve myocardial perfusion in hypertensive patients. However, its effects on coronary artery vasomotility and on post-stenotic coronary flow reserve in patients with atherosclerotic heart disease are unknown.

OBJECTIVES

This study was designed to investigate the acute direct effects of repeated infusions of lacidipine on epicardial coronary artery vasomotion and on post-stenotic coronary artery blood flow in patients with stable angina pectoris and angiographic evidence of coronary heart disease.

METHODS

In 8 patients with stable angina and moderate to severe stenosis of the left coronary artery, measurements of epicardial dimensions (quantitative angiography) and of coronary blood flow (Doppler guidewire) distal to a stenosis were performed at baseline and after 3 repeated intracoronary boluses of 12 microg of lacidipine. Results were compared with those obtained after 10 mg of intracoronary papaverine.

RESULTS

The intracoronary administration of lacidipine was well tolerated, without any adverse effects. Lacidipine significantly increased the minimal luminal diameter of the lesion (peak relative increase of 43.7%), without significant changes in heart rate and systolic aortic pressure. Intracoronary lacidipine caused a dose-dependent increase in coronary flow reserve. Maximal vasodilatory effects were equivalent to those obtained with intracoronary papaverine.

CONCLUSIONS

These results suggest that lacidipine acts directly as a potent vasodilator in stenotic epicardial vessels and improves myocardial perfusion distal to a moderately severe stenosis in patients with stable angina.

Assessment of coronary flow reserve with fast cine phase contrast magnetic resonance imaging: comparison with measurement by Doppler guide wire

Fast cine phase contrast magnetic resonance imaging (fast cine phase contrast MRI) can measure phasic coronary flow velocity in humans. The purpose of this study was to compare the coronary flow velocity reserves measured by MR IMAGING with those obtained by Doppler guide wire. Nineteen patients with ischemic or valvular heart disease were studied. Fast cine phase contrast MR images of the left anterior descending (LAD) artery were acquired during breath-hold time in the basal state and after administration of dipyridamole. Flow velocity in the LAD artery was also measured with Doppler guide wire before and after venous injection of dipyridamole in all subjects. Flow velocity in the coronary artery measured with MR IMAGING in the basal state (12.5 +/- 4.9 cm/sec) was significantly lower than that obtained with Doppler guide wire (32.4 +/- 12.1 cm/sec, P < 0.01). However, MR assessments of coronary flow velocity reserve showed a good linear correlation with those measured by Doppler guide wire (r = 0.91). In conclusion, fast cine phase contrast MR imaging is a useful technique, which can provide a noninvasive assessment of flow reserve ratios in patients with coronary artery disease. J. Magn. Reson. Imaging 1999;10:563-568.

Functional assessment of coronary artery stenosis by doppler derived absolute and relative coronary blood flow velocity reserve in comparison with (99m)Tc MIBI SPECT

OBJECTIVE

To determine the relation between the relative and absolute coronary blood flow velocity reserve (CFVR) compared with the results of (99m)Tc MIBI single photon emission computed tomography (SPECT).

METHODS

In 37 patients with one vessel disease, (99m)Tc MIBI SPECT was performed before angioplasty, two to three weeks after angioplasty, and at six months' follow up. CFVR was measured distal to the stenosis (dCFVR) as well as in a reference coronary artery before angioplasty, immediately after angioplasty, and at late follow up. Relative CFVR (rCFVR) was calculated as the ratio between dCFVR and CFVR measured in the reference coronary artery. The optimal thresholds for reversible perfusion defects were calculated using receiver operating characteristic curves.

RESULTS

The agreement for the full range of coronary artery stenosis (n = 107, mean (SD) diameter stenosis 48 (28)%, range 0-98%) between dCFVR (cut off value 1.9) and rCFVR (cut off value 0.65) with (99m)Tc MIBI SPECT was 81% and 85%, respectively. In intermediate lesions (n = 49, diameter stenosis range 30-75%) the agreement between dCFVR (cut off value 2.0) and (99m)Tc MIBI SPECT was 72%, which increased to 78% using the rCFVR (cut off value 0.65). There was a strong linear relation between dCFVR and rCFVR (r = 0.93, p < 0.0001).

CONCLUSIONS

A best cut off value for dCFVR of 1.9 corresponds with a best cut off value of 0.65 for rCFVR, within the full range of coronary narrowings. Intracoronary blood flow velocity analysis could obviate the need for additional myocardial perfusion scintigraphy in the majority of patients.

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).

Clinical potential of intravascular ultrasound for physiological assessment of coronary stenosis: relationship between quantitative ultrasound tomography and pressure-derived fractional flow reserve

BACKGROUND

Little is known regarding intravascular ultrasound (IVUS) criteria to determine the functional severity of coronary stenosis. Recently, fractional flow reserve (FFR) has emerged as a lesion-specific index of the functional severity of a coronary stenosis that is independent of systemic hemodynamic variability. The present study was undertaken to determine the IVUS parameters for the physiological severity of coronary stenosis.

METHODS AND RESULTS

Fifty-one lesions in 42 patients were evaluated by means of quantitative coronary angiogram, IVUS, and intracoronary pressure measurements. The FFR was calculated as the ratio of the distal coronary pressure divided by the proximal coronary pressure under hyperemia. We considered a value of the FFR <0.75 as significant in determining inducible ischemia, according to the previous studies. The minimal luminal area (MLA) and the area stenosis were measured by IVUS. By regression analysis, the MLA showed a positive correlation with the FFR value (r(2)=0.62, P<0.0001). The area stenosis had a significant inverse correlation with the value of FFR (r(2)=0.60, P<0.0001). The IVUS thresholds that maximized the sensitivity and specificity were MLA <3.0 mm(2) (sensitivity, 83.0%; specificity, 92.3%) and area stenosis >0.6 (sensitivity, 92.0%; specificity, 88.5%). The combination of both criteria (MLA <3.0 mm(2) and area stenosis <0.6) without exception met a value of the FFR <0.75.

CONCLUSIONS

Anatomic parameters obtained by IVUS showed a significant correlation to the FFR values. The present study demonstrated that the combination of the MLA and area stenosis measured by IVUS can be an anatomic predictor for the physiological impact of coronary epicardial stenosis.

Long-term follow-up after percutaneous transluminal coronary angioplasty was not performed based on intravascular ultrasound findings: importance of lumen dimensions

BACKGROUND

Angiography is limited in determining the anatomic severity of coronary artery stenoses. Clinical decision-making in patients with symptoms and intermediate lesions remains challenging.

METHODS AND RESULTS

The current analysis included 300 patients (357 intermediate native artery lesions) in whom intervention was deferred based on intravascular ultrasound (IVUS) findings. Standard clinical, angiographic, and IVUS parameters were collected. Patients were followed for >1 year. Events occurred in 24 patients (8%). They included 2 cardiac deaths, 4 myocardial infarctions, and 18 target-lesion revascularizations (TLR; 12 percutaneous transluminal coronary angiographies and 6 coronary artery bypass grafts; only 3 TLRs occurred within 6 months after the IVUS study). All significant univariate clinical, angiographic, and IVUS parameters (P<0.05) were tested in multivariate models. These included diabetes mellitus, IVUS lesion lumen area, maximum lumen diameter, minimum lumen diameter, plaque area, plaque burden, and area stenosis (AS). No angiographic measurement was significant at P<0.05. The only independent predictors of an event (death, myocardial infarction, or TLR) were IVUS minimum lumen area and AS. The only independent predictors of TLR were diabetes mellitus, IVUS minimum lumen area, and AS. In 248 lesions with a minimum lumen area >/=4.0 mm(2), the event rate was only 4.4% and the TLR rate 2.8%.

CONCLUSIONS

Long-term follow-up after IVUS-guided deferred interventions in patients with de novo intermediate native artery lesions showed a low event rate. In patients with a minimum lumen area >/=4.0 mm(2), the event rate was especially low. IVUS imaging is an acceptable alternative to physiological assessment in these patients.

Assessment of coronary stenoses by Doppler wires: a validation study using in vitro modeling and computer simulations

The present study evaluates the use of intracoronary velocity measurements by Doppler guidewires for assessing coronary obstructions. In vitro experiments were performed in a flow model using acrylic phantoms of coronary stenoses with different configurations (stenosis area: 56%, 75% and 89%; stenosis length: 1 and 5 mm; stenosis border: tapering or abrupt). Nonpulsatile laminar flow conditions of a test fluid were established at flow rates ranging from 0.5 to 2.0 mL/s to simulate baseline flow and flow after vasodilation. Peak Doppler velocity was measured proximal to, within and distal to the model stenoses. Computer simulations were employed to calculate radial flow profiles with and without a Doppler wire aligned with the vessel center. In 84 in vitro flow experiments, peak Doppler velocity correlated well with the average flow velocity as calculated from the actual flow rate and the vessel's cross-sectional area proximal to (r = 0.98, SEE = 1.4, p < 0.001) and within (r = 0.97, SEE = 16.4, p < 0.001) the stenosis. However, the ratio of calculated average velocity to Doppler-measured peak velocity was significantly different from 0.5, the expected value for a parabolic flow profile (0.76+/-0.08, 0.81+/-0.14; p < 0.001). Acceptable accuracy was found for the Doppler estimation of stenosis severity using the continuity equation (error: 0.9+/-1.2% and -4.6+/-3.5% for stenosis with a length of 5 mm and 1 mm, respectively). Doppler velocity reserve significantly underestimated the true flow reserve for the 56% and 75% stenoses (p < 0.01). Computer simulations demonstrated significant alterations of flow profiles by the wire, which explained the observed underestimation of the true flow reserve by the Doppler velocity reserve. Thus, Doppler guidewire measurements of intracoronary flow velocities are useful to assess the severity of coronary stenoses. However, the in vitro results and computer simulations indicate that guidewires alter the flow profile, so that Doppler velocity reserve may underestimate the true flow reserve.

Clinical validation of intravascular ultrasound imaging for assessment of coronary stenosis severity: comparison with stress myocardial perfusion imaging

OBJECTIVES

To validate intravascular ultrasound (IVUS) measurements for differentiating functionally significant from nonsignificant coronary stenosis.

BACKGROUND

To date, there are no validated criteria for the definition of a flow-limiting coronary artery stenosis by IVUS.

METHODS

Preinterventional IVUS imaging (30-MHz imaging catheter) of 70 de novo coronary lesions was performed. The lesion lumen area and three IVUS-derived stenosis indixes comparing lesion lumen area with the lesion external elastic lamina (EEL) area, the mean reference lumen area and the mean reference EEL area were compared with the results of stress myocardial perfusion imaging.

RESULTS

The lesion lumen area and three IVUS-derived stenosis indexes showed sensitivities and specificities ranging between 80% and 90% using stress myocardial perfusion imaging as the gold standard. The lesion lumen area < or =4 mm2 is a simple and highly accurate criterion for significant coronary narrowing.

CONCLUSIONS

Quantitative IVUS indices can be reliably used for identifying significant epicardial coronary artery stenoses.

Phasic coronary flow pattern and flow reserve in patients with left bundle branch block and normal coronary arteries

OBJECTIVES

The purpose of this study was to determine whether scintigraphic myocardial perfusion defects in patients with left bundle branch block (LBBB) and normal coronary arteries are related to abnormalities in coronary flow velocity pattern and/or coronary flow reserve.

BACKGROUND

Septal or anteroseptal defects on exercise myocardial perfusion scintigraphy are common in patients with LBBB and normal coronary arteries.

METHODS

Thirteen patients (7 men, age 61+/-8 years) with LBBB and normal coronary arteries underwent stress thallium-201 scintigraphy and cardiac catheterization. In all patients and in 11 control subjects coronary blood flow parameters were calculated from Doppler measurements of flow velocity in the left anterior descending coronary artery (LAD) before and after adenosine administration.

RESULTS

The time to maximum peak diastolic flow velocity was significantly longer both for the seven patients with (134+/-19 ms) and for the six without (136+/-7 ms) exercise perfusion defects than for controls (105+/-12 ms, p < 0.05), whereas the acceleration was slower (170+/-54, 186+/-42 and 279+/-96 cm/s2, respectively, p < 0.05). Coronary flow reserve in the patients with exercise perfusion defects (2.7+/-0.3) was significantly lower than in those without (3.7+/-0.5, p < 0.05) or in the control group (3.4+/-0.5, p < 0.05).

CONCLUSIONS

Patients with LBBB have an impairment of early diastolic blood flow in the LAD due to an increase in early diastolic compressive resistance resulting from delayed ventricular relaxation. Furthermore, exercise scintigraphic perfusion defects in these patients are associated with a reduced coronary flow reserve, indicating abnormalities of microvascular function in the same vascular territory.

Noninvasive assessment of coronary flow reserve with transthoracic signal-enhanced Doppler echocardiography

OBJECTIVES

The feasibility of noninvasive assessment of coronary flow reserve (CFR) in the distal left anterior descending artery (LAD) with echocardiography-enhanced transthoracic pulsed wave Doppler guided by high-resolution transthoracic color Doppler (TTCD) was investigated. The results were compared with the degree of coronary diameter stenosis obtained during cardiac catheterization.

BACKGROUND

Assessment of CFR has proven to be useful in the selection of patients undergoing invasive treatment of coronary artery disease and in estimating their prognosis. However, CFR could only be determined invasively in everyday practice during catheterization procedures. Recent development of high-resolution TTCD allows transthoracic visualization of distal LAD and supra-apical intramyocardial perforator branches and noninvasive measurement of CFR with pulsed wave Doppler technique.

METHODS

CFR was determined by measuring the ratio of pulsed wave Doppler time velocity integral during adenosine-induced hyperemia (140 microgram/kg/min intravenously) to baseline value. If the baseline Doppler signal of LAD flow was insufficient, an echocardiography (echo) enhancer (Levovist) was used. Forty-five patients were examined by TTCD (7-MHz B-mode, 5-MHz color Doppler, and 3.5-MHz pulsed wave Doppler) after coronary angiography had been performed. Group 1 consisted of 15 patients without heart disease, group 2 of 15 patients with 50% to 85% isolated LAD diameter stenosis, and group 3 of 15 patients with >85% LAD diameter stenosis.

RESULTS

Peripheral LAD coronary flow at baseline condition was assessed in 40 (88%) patients with TTCD. CFR could be quantified in 36 (80%) of the 45 patients: in 18 patients without echo enhancer, and in 18 patients with echo-enhancing agent. CFR could not be assessed in 9 (20%) patients. CFR in the various groups was as follows: group 1, 3. 13 +/- 0.57; group 2, 2.23 +/- 0.20 (vs group 1: P <.01); and group 3, 1.64 +/- 0.30 (vs group 2: P <.02).

CONCLUSION

CFR in the LAD can be determined in 80% of patients with pulsed wave Doppler guided by high-resolution TTCD combined with intravenously administered echo-enhancing agent.

Safety of deferring angioplasty in patients with normal coronary flow velocity reserve

BACKGROUND

In the catheter laboratory there is a need for functional tests validating the hemodynamic significance of coronary artery stenosis.

OBJECTIVES

It was the objective of our study to compare the long-term cardiac event rate and the clinical symptoms in patients with reduced coronary flow velocity reserve (CFVR) and standard PTCA with patients with normal CFVR and deferred angioplasty.

METHODS

Our study included 70 patients with intermediate coronary artery stenoses (13 f, 57 m; diameter stenosis >50%, <90%) and an indication for PTCA due to stable angina pectoris and/or signs of ischemia in noninvasive stress tests. CFVR was measured distal to the lesion after intracoronary administration of adenosine using 0.014 inch Doppler-tipped guide wires.

RESULTS

In 22 patients (31%), PTCA was deferred due to a CFVR > or = 2.0 (non-PTCA group). In the remaining 48 patients (69%) mean CFVR of 1.4+/-0.23 (p < 0.001) was measured (PTCA group). CFVR increased to 2.0+/-0.51 after angioplasty. During follow-up (average 15+/-6.0 months), the following major adverse cardiac events (MACE) occurred: in the PTCA group re-PTCA was performed in nine patients (18.8%) because of unstable angina, five patients (10.4%) suffered an acute myocardial infarction (MI) (two infarctions occurred during the angioplasty, three patients suffered an infarction during follow-up), two patients (4.2%) needed blood transfusions due to severe bleedings, two patients (4.2%) underwent bypass surgery and one patient (2.1%) died. In the non-PTCA group, angioplasty was necessary only in two cases (9.1%) during follow-up. We did not observe any MI in the non-PTCA group. The overall rate of MACE was significantly lower in the non-PTCA group compared to the PTCA group (9.1% vs. 33.3%, p < 0.01). However, only 40% of the patients of the non-PTCA group were free of angina pectoris at stress. In the PTCA group, 63% did not complain of any symptoms at follow-up (p < 0.05).

CONCLUSIONS

We conclude that determination of the CFVR is a valuable parameter for stratifying the hemodynamic significance of coronary artery stenosis. PTCA can safely be deferred in patients with significant coronary stenosis but a CFVR > or = 2.0. The total rate of MACE at follow-up was below 10% among these patients. However, if PTCA was deferred the number of patients who are free of angina is lower compared to those patients who underwent angioplasty.

[Noninvasive determination of coronary flow reserve with signal enhanced high resolution transthoracic Doppler color echocardiography]

The feasibility of non-invasive assessment of coronary flow reserve (CFR) in the left anterior descending artery (LAD) using echo-enhanced high-resolution transthoracic color Doppler echocardiography (TTCD) was investigated. The results were compared with the degree of coronary diameter-stenosis obtained during cardiac catheterization. CFR has proven to be useful in the selection of patients undergoing invasive treatment of coronary artery disease and in estimating their prognosis. However, CFR could only be determined in everyday practice invasively during catheterization procedures. Recent development of high-resolution TTCD allows transthoracic visualization of distal LAD and supra-apical intramyocardial perforator branches, and non-invasive measurement of CFR. CFR was determined by measuring the ratio of pulsed-wave Doppler time velocity integral during adenosine-induced hyperemia (140 micrograms/kg/min i.v.) to baseline value. If Doppler signal of LAD flow was insufficiently at basal condition, an echo enhancer (Levovist) was used. 45 patients were examined by TTCD (7 MHz B-mode, 5 MHz color Doppler, 3.5 MHz PW Doppler) after coronary angiography had been performed. Group I consisted of 15 patients without heart disease, Group II of 15 patients with 40 to 70% isolated LAD diameter stenosis, and Group III of 15 patients with > 70% LAD diameter stenosis. Peripheral LAD coronary flow at baseline condition was assessed in 40 patients (88%) using TTCD. CFR could be quantified in 36/45 patients (80%), in 18 patients without echo enhancer, and in 18 patients with echo-enhancing agent. In 9/45 patients CFR could not be assessed. CFR in Group I was 3.13 +/- 0.57, in Group II 2.23 +/- 0.20 (vs Group I p < 0.01) and in Group III 1.64 +/- 0.30 (vs Group II p < 0.02).

CONCLUSION

CFR of LAD can be determined in 80% of patients by the synergistic use of high-resolution TTCD combined with intravenous given ultrasound echo-enhancing agent.

Noninvasive assessment of coronary flow velocity and coronary flow velocity reserve in the left anterior descending coronary artery by Doppler echocardiography: comparison with invasive technique

OBJECTIVES

The purpose of this study was to evaluate whether transthoracic Doppler echocardiography (TTDE) can reliably measure coronary flow velocity (CFV) and coronary flow velocity reserve (CFVR) in the left anterior descending coronary artery (LAD) in the clinical setting.

BACKGROUND

Coronary flow velocity measurement has provided useful clinical and physiologic information. Advancement in TTDE provides noninvasive measurement of CFV and CFVR in the distal LAD.

METHODS

In 23 patients, CFV in the distal LAD was measured by TTDE (5 or 3.5 MHz) under the guidance of color Doppler flow mapping at the time of Doppler guide wire (DGW) examination. Coronary flow velocity in the distal LAD were measured at baseline and hyperemic conditions (intravenous administration of adenosine 0.14 mg/kg/min) by both TTDE and DGW techniques. Coronary flow velocity reserve was defined as the ratio of peak hyperemic to basal averaged peak velocity in the distal LAD.

RESULTS

Clear envelopes of basal and hyperemic CFV in the distal LAD were obtained in 18 (78%) of 23 study patients by TTDE. There were excellent correlations between TTDE and DGW methods for the measurements of CFV (averaged peak velocity: r=0.97, y=0.94x + 0.40; averaged diastolic peak velocity: r=0.97, y=0.94x + 0.69; systolic peak velocities: r=0.97, y=0.91x + 0.87; diastolic peak velocity: r=0.98, y=0.95x + 1.10). Coronary flow velocity reserve from TTDE correlated highly with those from DGW examinations (r=0.94, y=0.95x + 0.21).

CONCLUSIONS

Noninvasive measurement of CFV and CFVR in the distal LAD using TTDE accurately reflects invasive measurement of CFV and CFVR by DGW method.

Coronary flow reserve in the contralateral artery increases after successful coronary angioplasty in patients with spontaneously visible collateral vessels

OBJECTIVE

To test the hypothesis that coronary flow reserve could increase in the angiographically normal contralateral artery after successful coronary angioplasty of an ipsilateral coronary artery.

DESIGN

Coronary flow reserve was estimated using a Doppler flow guide wire, by giving intracoronary adenosine in the contralateral artery, before and 15 minutes after the end of angioplasty.

SETTING

Tertiary referral centre.

PATIENTS

31 patients, mean (SD) age 56 (11) years, with stable angina and single vessel disease, undergoing angioplasty of the right coronary or the left anterior descending artery.

RESULTS

In the contralateral artery baseline average peak velocity was 21 (9) cm/s before angioplasty and decreased to 12 (6) cm/s after (p < 0.005), while hyperaemic average peak velocity was 47 (19) cm/s before and decreased to 34 (15) cm/s after (p < 0.005). However, coronary flow reserve in the contralateral artery was 2.4 (0.7) before angioplasty and increased to 2.9 (0.6) after (p < 0.05). The contralateral coronary flow reserve after angioplasty increased by 0.8 (0.4) in 11 patients with visible collaterals before angioplasty and by 0.3 (0.6) in the remaining patients without visible collaterals (p < 0.05). Blood pressure and heart rate were unchanged after the procedure.

CONCLUSIONS

Coronary flow reserve in an angiographically normal contralateral artery increases after successful coronary angioplasty of the ipsilateral artery in patients with spontaneously visible collateral vessels before the procedure.

Hemodynamic rounds series II: Coronary hemodynamics for angioplasty and stenting after myocardial infarction: use of absolute, relative coronary velocity and fractional flow reserve

The application of absolute coronary velocity reserve, relative coronary velocity reserve, and pressure-derived fractional flow reserve of the myocardium may have influence on decision making for angioplasty and stenting in patients after myocardial infarction. This case highlights the use and limitations of these techniques in the setting of myocardial infarction where absolute coronary flow reserve may be commonly compromised. The role for absolute, relative coronary, and fractional flow reserve are discussed.

Coronary arteriography and lipid lowering: limitations, new concepts, and new paradigms in cardiovascular medicine

Coronary arteriography has played a central role in improving our understanding of the mechanisms of unstable coronary syndromes and the benefits of cholesterol lowering. However, coronary arteriography as currently used is outmoded and inadequate for new clinical algorithms based on vigorous lipid and other risk factor control as alternatives to invasive procedures for the primary treatment of coronary artery disease. What is needed is a way of viewing or analyzing noninvasive myocardial perfusion images and coronary arteriograms so as to identify and quantify the extent or severity of diffuse coronary atherosclerosis. Determining the relative contribution of diffuse and segmental narrowing by definitive myocardial perfusion imaging or coronary arteriography would provide the optimal basis for determining the need for revascularization procedures. In the absence of significant segmental stenoses, mild or diffuse disease identified by coronary arteriography would also provide a definitive diagnosis as the basis for lifelong cholesterol-lowering drugs and risk factor modification, even for patients with normal cholesterol levels. Thus, it is important to consider several new concepts for analyzing coronary arteriograms. More physiologically accurate invasive and noninvasive technology allows improved diagnosis and management of coronary atherosclerosis as new paradigms in cardiovascular medicine.

Clinical, intravascular ultrasound, and quantitative angiographic determinants of the coronary flow reserve before and after percutaneous transluminal coronary angioplasty

This study evaluated the clinical, intravascular ultrasound (IVUS), and angiographic determinants of the coronary flow reserve (CFR) as measured by guidewire Doppler velocimetry. Using standard methodology, 86 consecutive patients were studied before intervention (n = 73 patients, including the assessment of intermediate stenoses) and/or after intervention (n = 39 patients, including after percutaneous transluminal coronary angioplasty (PTCA) in 27 and post-Palmaz-Schatz stent placement + high-pressure adjunct PTCA in 12). Only 5 patients were studied before intervention, post-PTCA, and poststent. Univariate and multivariate clinical, quantitative coronary angiography (QCA), and IVUS correlates of the CFR were evaluated. There was a linear relation between CFR and IVUS minimum lumen cross-sectional area (CSA): r = 0.771, p <0.0001 for the overall cohort; r = 0.831, p <0.0001 before intervention; r = 0.514, p = 0.0061 post-PTCA; and r = 0.623, p = 0.0306 poststent placement. Overall, an IVUS minimum lumen CSA of > or = 4.0 mm2 had a diagnostic accuracy of 89% in identifying a CFR of > or = 2.0. This diagnostic accuracy increased slightly to 92% when only the preintervention observations were considered. Using multivariate linear regression analysis, the independent determinants of the CFR in the overall cohort of 112 observations were IVUS minimum lumen CSA (p <0.0001), angiographic lesion length (p = 0.0101), and diabetes mellitus (p = 0.0371): r2 = 0.6224. When the subset of preintervention observations were analyzed separately, the independent determinants of the CFR were minimum lumen CSA (p <0.0001) and angiographic lesion length (p = 0.0095); r2 = 0.7176. Thus, the major determinants of the CFR in patients with coronary artery disease are lumen compromise (which is best assessed by the IVUS measurement of the minimum lumen CSA) and lesion length. A minimum lumen CSA > or = 4.0 mm2 has a high diagnostic accuracy in predicting a CFR > or = 2.0, especially before intervention.

Improved assessment of coronary stenosis severity using the relative flow velocity reserve

BACKGROUND

Myocardial fractional flow reserve (FFR) is based on pressure measurements. We have now sought to establish a Doppler-based concept of relative flow velocity reserve (RFVR) for the functional assessment of stenosis severity in epicardial coronary arteries. A clear threshold value to discriminate the functional severity of a coronary stenosis does not exist for coronary flow velocity reserve (CVR) based on intracoronary Doppler measurements. In contrast, the concept of FFR, which is based on intracoronary pressure measurements, has been extensively validated. An FFR value below 0.75 reliably indicates a significant stenosis.

METHODS AND RESULTS

RFVR is calculated as the ratio between distal CVR in the stenosed target vessel and distal CVR in a nonstenotic reference vessel. In 21 patients, RFVR was determined in 24 target vessels by use of intracoronary adenosine and correlated to the FFR, determined as the ratio of mean poststenotic to aortic pressures, in the target vessel. Stenosis severity was classified according to quantitative coronary angiography analysis. Reference diameter was 3.0+/-0.4 mm (mean+/-SD), and area stenosis was 74+/-15% (range, 40% to 95%). CVRs in the target and reference vessels were 2.1+/-0.5 and 2.6+/-0.7, respectively. FFR ranged from 0.49 to 0.99 (mean, 0.81+/-0.15) and RFVR from 0.53 to 1.0 (mean, 0.82+/-0.13). Poststenotic CVR did not correlate with either percent area stenosis (r=0.27, P=NS) or FFR (r=0.33, P=NS). In contrast, FFR as well as RFVR showed a curvilinear relation to percent area stenosis (r=0.89, P<0.0001 and r=0.79, P<0.0001, respectively). There was a close linear correlation between FFR and RFVR (r=0.91, P<0.0001).

CONCLUSIONS

RFVR correlates closely to FFR and to percent area stenosis, whereas the correlation of CVR with FFR and percent area stenosis is rather poor. RFVR is a promising new concept for assessment of coronary stenosis severity and clinical decision making based on Doppler measurements.

Current concepts of coronary flow reserve for clinical decision making during cardiac catheterization

Measurements of coronary flow reserve, once used only for research, have gained wide acceptance as an additional diagnostic approach in the decision-making process of diagnostic cardiac catheterization and coronary interventions. Apart from the noninvasive determination of coronary flow reserve, intracoronary Doppler flow wires have facilitated decision making in the catheterization laboratory. Different techniques, unstandardized procedures, and data from uncomparable patient populations have remained a confounding factor. This review examines current concepts of coronary flow reserve as well as methodologic considerations and pitfalls. Applications of coronary flow reserve for periinterventional assessment are evaluated on the background of practical guidance. According to a detailed examination of arterial structure and function, a normal coronary flow reserve exceeds a value of 3.0. Values below 3.0 suggest involvement of microvascular disease caused by functional or structural alterations. The influences of various factors such as age, hemodynamics, hypercholesterolemia, hypertrophy, hypertension, syndrome X, and coronary artery disease are discussed in relation to the effect on coronary flow reserve. From available information, measurements of coronary flow reserve are an adjunct to current interventional technology to optimize individual patient care. Further efforts should be undertaken to incorporate these new methods into our routine clinical decision making.

Assessment of coronary blood flow in humans using phase difference MR imaging. Comparison with intracoronary Doppler flow measurement

Coronary blood flow quantification provides essential information on the hemodynamic significance of coronary artery stenoses. Recently, magnetic resonance (MR) flow mapping has emerged as a new promising method to noninvasively determine flow velocity and flow volume within the coronary arteries. The aim of this study was to compare phase difference (PD) MR flow quantification with intracoronary Doppler flow measurements in 15 patients with suspected or known coronary artery disease. Flow quantification was attempted before and after systemic application of 5mg Isosorbiddinitrate (ISDN) in order to determine possible alterations in coronary flow volume. PD MR flow mapping was performed successfully in 13 of the 15 patients. For flow velocities and flow volume values, a close correlation between PD MR and Doppler flow measurements was found (r = 0.79 and r = 0.90, respectively). However, average flow measured by PD MR was significantly lower than the invasively obtained values (9.0 +/- 4.4 cm/sec vs. 11.7 +/- 4.9 cm/sec; p < 0.001 and 46.3 +/- 28.7 ml/min vs. 53.4 +/- 32.8 ml/min; p < 0.05). Although the mean flow volume remained constant in the entire patient group after ISDN application, individual changes (increase in 6, decrease in 4 cases) could be documented with PD MR imaging and showed a good correlation to the Doppler method (r = 0.82). In conclusion, PD MR flow mapping is a promising method for the noninvasive quantification of coronary blood flow and therefore offers the potential of assessing coronary artery stenoses. However, technical improvements are mandatory in order to increase accuracy of the method.

Noninvasive assessment of significant left anterior descending coronary artery stenosis by coronary flow velocity reserve with transthoracic color Doppler echocardiography

BACKGROUND

Coronary flow reserve has been considered an important diagnostic index of the functional significance of coronary artery stenosis. With Doppler technique, it has been assessed as the ratio of hyperemic to basal coronary flow velocity (coronary flow velocity reserve [CFVR]) by invasive or semiinvasive methods with a Doppler catheter, a Doppler guide wire, and a transesophageal Doppler echocardiographic probe. Recent technological advancement in transthoracic Doppler echocardiography (TTDE) provides measurement of coronary flow velocity in the distal portion of the left anterior descending coronary artery (LAD) and may be useful in the noninvasive CFVR measurement. The purpose of this study was to evaluate the value of CFVR determined by TTDE for the assessment of significant LAD stenosis.

METHODS AND RESULTS

We studied 36 patients who underwent coronary angiography for the assessment of coronary artery disease. The study population consisted of 12 patients with significant LAD stenosis (group A) and 24 patients without significant LAD stenosis (group B). With TTDE, coronary flow velocities in the distal LAD were recorded at rest and during hyperemia induced by intravenous infusion of adenosine (0.14 mg x kg(-1) x min(-1)) under the guidance of color Doppler flow mapping. Adequate spectral Doppler recordings of coronary flow in the distal LAD for the assessment of CFVR were obtained in 34 of 36 study patients (94%). The peak and mean diastolic coronary flow velocities at baseline did not differ between groups A and B (23.6+/-10.3 versus 22.9+/-6.6 cm/s and 16.4+/-8.6 versus 14.5+/-4.0 cm/s, respectively). However, the peak and mean coronary flow velocities during hyperemia in group A were significantly smaller than those in group B (35.6+/-16.3 versus 54.2+/-16.3 cm/s and 24.7+/-13.1 versus 37.9+/-13.0 cm/s, respectively; P<.01). There were significant differences in CFVR obtained from peak and mean diastolic velocity between groups A and B (1.5+/-0.2 versus 2.4+/-0.4 and 1.5+/-0.2 versus 2.6+/-0.4, respectively; P<.001). A CFVR from peak diastolic velocity <2.0 had a sensitivity of 92% and a specificity of 82% for the presence of significant LAD stenosis. A CFVR from mean diastolic velocity <2.0 had a sensitivity of 92% and a specificity of 86% for the presence of significant LAD stenosis.

CONCLUSIONS

CFVR determined by TTDE is useful in the noninvasive assessment of significant stenotic lesion in the LAD.

Which variable of stenosis severity best describes the significance of an isolated left anterior descending coronary artery lesion? Correlation between quantitative coronary angiography, intracoronary Doppler measurements and high dose dipyridamole echocardiography

OBJECTIVES

This study sought to investigate the angiographic or intracoronary Doppler variables of stenosis severity that best correlate with the results of dipyridamole echocardiography.

BACKGROUND

Quantitative coronary angiography and intracoronary Doppler flow velocity assessments are the commonly used techniques for the objective identification of significant coronary artery stenosis.

METHODS

Thirty patients with an isolated lesion of the left anterior descending coronary artery (LAD) were studied by means of on-line quantitative coronary arteriography, intracoronary Doppler flow velocity measurements and dipyridamole echocardiography 6 months after percutaneous transluminal coronary angioplasty. The quantitative arteriographic analyses were performed on-line; post-stenotic Doppler flow velocities were measured at baseline and after adenosine infusion. Angiographic and Doppler measurements were compared with the corresponding dipyridamole echocardiographic data and analyzed by discriminant analysis.

RESULTS

The dipyridamole echocardiographic response was positive in 11 patients (37%). The best cutoff values for predicting an abnormal echocardiographic response were 1) stenotic flow reserve of 2.8 (p = 0.0001); 2) 59% diameter stenosis (p = 0.0001); 3) minimal lumen diameter of 1.35 mm (p = 0.001); 4) coronary flow reserve of 2.0 (p = 0.0002); and 5) maximal peak velocity of 60 cm/s during hyperemia (p = 0.04). Multivariate analysis identified stenotic flow reserve as the only independent predictor of ischemia during dipyridamole echocardiography.

CONCLUSIONS

Stenotic flow reserve is the variable that best describes the functional significance of an isolated LAD lesion, and a value of 2.8 is the best predictor of a positive dipyridamole echocardiographic response. Furthermore, angiographic variables of stenosis severity relate to echocardiographic test results better than intracoronary Doppler variables.

Mechanisms of limited maximum coronary flow in severe single-vessel coronary artery disease in humans due to vertical steal

We evaluated the usefulness of a decrease in the average peak velocity from 4 to 10 minutes after infusion of dipyridamole for detecting myocardial ischemia in 50 patients, including patients with a prior myocardial infarction. The decrease in the average peak velocity from 4 to 10 minutes associated with vertical steal and combined with a coronary flow reserve of < 1.6 had a high predictive value for myocardial ischemia in patients with or without prior myocardial infarction.

Retinopathy identifies marked restriction of coronary flow reserve in patients with diabetes mellitus

OBJECTIVES

This study sought to assess the differences in coronary flow reserve in patients with and without diabetic retinopathy.

BACKGROUND

Microvascular abnormalities throughout the body and impairment of coronary flow reserve have been described in patients with diabetes mellitus. However, the relation between diabetic retinopathy and coronary microvascular disease has not been investigated.

METHODS

The study included 29 patients with diabetes mellitus (18 with and 11 without diabetic retinopathy) and 15 control patients with chest pain and normal coronary arteries. Diabetic retinopathy was nonproliferative in all 18 patients with this disorder (8 had background, 10 preproliferative retinopathy). Five minutes after injection of 3 mg of isosorbide dinitrate, phasic flow velocities were recorded in the proximal segment of the angiographically normal left anterior descending coronary artery at rest and during hyperemia (0.14 mg/kg body weight per min of adenosine infused intravenously) using a 0.014-in. 15-MHz Doppler guide wire. Coronary blood flow was calculated, and coronary flow reserve was obtained from the hyperemic/baseline flow ratio.

RESULTS

Coronary blood flow was significantly lower during hyperemia ([mean +/- SD] 107 +/- 23 and 116 +/- 18 vs. 136 +/- 17 ml/min, respectively) and higher at baseline (58 +/- 16 and 45 +/- 12 vs. 37 +/- 10 ml/min, respectively) in diabetic patients with and without retinopathy than in control subjects (p < 0.05 for both diabetic groups). As a result, coronary flow reserve in both groups of diabetic patients was significantly lower than in control patients (1.9 +/- 0.4 and 2.8 +/- 0.3 vs. 3.3 +/- 0.4, respectively, p < 0.01 for both diabetic groups), and its reduction was greater in patients with than without retinopathy (p < 0.01). Furthermore, in patients with diabetic retinopathy, maximal hyperemic coronary flow (102 +/- 11 vs. 114 +/- 16 ml/min, p < 0.05) and flow reserve (1.6 +/- 0.2 vs. 2.3 +/- 0.2, p < 0.01) were significantly lower in those with preproliferative than background retinopathy.

CONCLUSIONS

Coronary flow reserve is significantly restricted in patients with diabetes mellitus, and its reduction is more marked in those with diabetic retinopathy, especially in advanced retinopathy. Thus, diabetic retinopathy should identify marked restriction of coronary flow reserve in patients with diabetes mellitus.

Phasic coronary flow characteristics in patients with constrictive pericarditis: comparison with restrictive cardiomyopathy

BACKGROUND

Phasic coronary flow characteristics have been reported in patients with aortic valve disease and hypertrophic cardiomyopathy. The purpose of this study was to assess the differences in coronary flow characteristics between patients with constrictive pericarditis and those with restrictive cardiomyopathy.

METHODS AND RESULTS

The study populations consisted of 7 case patients with constrictive pericarditis, 8 with restrictive cardiomyopathy, and 11 control subjects with chest pain and normal coronary arteries. Five minutes after injection of 3 mg of isosorbide dinitrate, phasic coronary flow velocity patterns were analyzed in the proximal segment of the angiographically normal left anterior descending coronary artery at rest using a 0.014-in, 15-MHz Doppler guidewire. Coronary flow reserve was obtained from the ratio of adenosine-induced (0.14 mg x kg(-1) x min(-1) I.V.) hyperemic/baseline time-averaged peak velocity. Although in case patients with constrictive pericarditis and restrictive cardiomyopathy maximal hyperemic time-averaged peak velocity (21+/-8 and 31+/-17 versus 60+/-19 cm/s, respectively; P<.001) and coronary flow reserve (1.3+/-0.4 and 1.6+/-0.6 versus 3.6+/-0.4, respectively, P<.001) were significantly lower than in control subjects, there were no significant differences in these indexes between the two groups of case patients. Velocity half-time of diastolic flow velocity corrected by square root(RR), which indicates deceleration of diastolic flow, in the groups of case patients with constrictive pericarditis and restrictive cardiomyopathy was significantly less than that in control subjects (6.2+/-2.6 and 10.6+/-1.5 versus 16.9+/-2.7, respectively; P<.001); this was also significantly smaller in constrictive pericarditis than restrictive cardiomyopathy (P<.001). This index <9.5 could distinguish constrictive pericarditis from restrictive cardiomyopathy with a sensitivity of 86% and a specificity of 88%. Furthermore, time from the beginning of diastole to diastolic peak velocity corrected by square root(RR) indicating acceleration of diastolic flow velocity in constrictive pericarditis was significantly less than that in restrictive cardiomyopathy and control subjects (2.8+/-1.2 versus 4.8+/-0.8 and 4.4+/-0.6, respectively; P<.001).

CONCLUSIONS

Although coronary flow reserve is limited in both constrictive pericarditis and restrictive cardiomyopathy because of restriction of hyperemic response, rapid acceleration and more rapid deceleration of diastolic flow velocity are more characteristic in constrictive pericarditis than in restrictive cardiomyopathy.

Comparison of coronary flow reserve between focal and diffuse vasoconstriction induced by ergonovine in patients with vasospastic angina

Decreased coronary flow reserve has been reported in patients with ergonovine-induced coronary vasoconstriction by the thermodilution method. To assess the difference of coronary flow reserve between patients with focal and diffuse vasospasm, after the vasospasm is discontinued by injection 3 mg of isosorbide dinitrate, phasic flow velocities of the diseased coronary artery were recorded at rest and during hyperemia (140 microg/kg/min of adenosine infusion intravenously) using a 0.014-inch, 15-MHz Doppler guidewire in 26 patients with ergonovine-induced coronary vasospasm (0.2-mg ergonovine injection intravenously), including 12 patients with focal (>90% stenosis), 14 patients with diffuse vasospasm (>50%), and 11 controls with normal coronary arteries without vasospasm. Although time-averaged peak velocity in cases with diffuse and focal vasospasm was not significantly different compared with that in controls at baseline (22 +/- 7, 18 +/- 5 vs 20 +/- 7 cm/s, respectively, NS), it was significantly lower in patients with diffuse vasospasm than in cases with focal vasospasm and in controls during hyperemia (43 +/- 13 vs 64 +/- 18, 61 +/- 19 cm/s, respectively, p <0.01). As a result, coronary flow reserve obtained from the ratio of hyperemic/baseline time-averaged peak velocity was significantly lower in patients with diffuse vasospasm than that in controls (1.9 +/- 0.4 vs 3.1 +/- 0.4, p <0.01), although it was not significantly different between the subjects with focal vasospasm and controls (3.5 +/- 0.7 vs 3.1 +/- 0.4, NS). Thus, coronary flow reserve is maintained normally in patients with focal vasospasm and limited in those with diffuse vasospasm. Microvascular impairment could exist further in cases with diffuse vasospasm, although similar endothelial dysfunction of the epicardial coronary artery is observed in focal and diffuse vasospasm.

Measurement of myocardial fractional flow reserve during coronary angioplasty in patients with old myocardial infarction

Although myocardial fractional flow reserve (FFRmyo) has been demonstrated to be a useful index for determining functional significance of coronary stenosis, the data in previous studies was derived from a highly selected group of patients. The aim of this study was to investigate the value of FFRmyo in a more clinically relevant group of patients, especially in patients who also had resistance vessel dysfunction. We measured FFRmyo in 20 consecutive patients who had undergone elective coronary angioplasty. FFRmyo was calculated by the ratio of Pc/Pa during intracoronary adenosine 5'-triphosphate (ATP; 50 micrograms in the left coronary and 20 micrograms in the right coronary artery) induced maximal hyperemia, where Pa represents mean aortic pressure obtained by the guiding catheter and Pc represents mean distal coronary pressure measured by a 2.1 F infusion catheter. In total, 21 vessels were dilated and 14 of them were infarct-related arteries. The percent diameter stenosis significantly decreased from 80 +/- 14% to 27 +/- 17%, and the FFRmyo increased significantly from 0.46 +/- 0.18 to 0.77 +/- 0.15 after angioplasty. There was no significant differences in the FFRmyo between vessels with previous myocardial infarction and those without, after angioplasty (0.78 +/- 0.18 vs. 0.76 +/- 0.08). There was a significant correlation between the percent diameter stenosis and FFRmyo before (r = 0.83, P < 0.001) and after (r = 0.64, P < 0.01) angioplasty. In conclusion, FFRmyo significantly improved immediately after angioplasty in vessels with myocardial infarction as well as those without. These results led us to suggest the usefulness of FFRmyo in patients who had both epicardial stenosis and resistance vessel dysfunction. The significant correlation between FFRmyo and quantitative coronary arterial diameter stenosis would further support the more widespread use of FFRmyo in the clinical setting.

From research to clinical practice: current role of intracoronary physiologically based decision making in the cardiac catheterization laboratory

Decisions regarding coronary interventions should be combined with objective evidence of myocardial ischemia. The most common physiologic approach utilizes hospital facilities outside the catheterization laboratory, requiring additional time and cost. With the introduction of sensor-tipped angioplasty guide wires, distal coronary flow velocity and pressure can be obtained in the cardiac catheterization laboratory, facilitating physiologically based decisions regarding the need for intervention. In the catheterization laboratory, physiologically significant stenoses can be characterized as having impaired post-stenotic coronary flow reserve < 2.0 and pressure-derived fractional flow reserve < 0.75, both variables related strongly to positive ischemic perfusion imaging or stress testing results. Deferring coronary interventions on the basis of normal translesional physiology is safe and is associated with a low rate (< 10%) of lesion progression over a 10-month follow-up period. Preliminary data indicate that excellent physiologic and anatomic end points after balloon angioplasty are associated with low (< 20%) restenosis rates at 6-month follow-up. Clinically relevant relations of in-laboratory physiology support the insight that physiologic, as much as or more than anatomic variables, ultimately determine the functional status of a patient. Current data suggest that an intracoronary physiologic approach complements coronary lumenology and appears to have important clinical and economic implications for patients undergoing invasive evaluation and treatment of coronary artery disease.

Intracoronary Doppler assessment of moderate coronary artery disease: comparison with 201Tl imaging and coronary angiography. FACTS Study Group

BACKGROUND

Coronary angiography may not reliably predict whether a stenosis causes exercise-induced ischemia. Intracoronary Doppler ultrasound may enhance diagnostic accuracy by providing a physiological assessment of stenosis severity. The goal of this study was to compare intracoronary Doppler ultrasound with both 201Tl imaging and coronary angiography.

METHODS AND RESULTS

Fifty-five patients with 67 stenotic coronary arteries underwent coronary angiography with intracoronary Doppler ultrasound and had exercise 201Tl testing within a 1-week period. Coronary flow reserve was measured, and analyses were performed by independent core laboratories. The mean stenosis was 59+/-12%; 51 of 67 stenoses were intermediate in severity (40% to 70%). A coronary flow reserve < 1.7 predicted the presence of a stress 201Tl defect in 56 of 67 stenoses (agreement=84%; kappa=0.67; 95% CI=0.48 to 0.86). In the patients who achieved 75% of their predicted maximum heart rate, the Doppler and 201Tl imaging data agreed in 46 of 52 stenoses (agreement=88%; kappa=0.77; 95%CI=0.57 to 0.97). Scatter was evident when angiography was compared with coronary flow reserve (r=.43), and the angiogram did not reliably predict the results of the 201Tl stress test (kappa=0.21; agreement=57% to 63%).

CONCLUSIONS

Doppler-derived coronary flow reserve accurately predicts the presence of exercise-induced ischemia on stress 201Tl imaging, and coronary angiography does not reliably assess the physiological significance of an intermediate coronary stenosis.