Coronary Blood Flow Velocity Reserve Research Articles

Coronary microvascular dysfunction: mechanisms and functional assessment.

Obstructive disease of the epicardial coronary arteries was recognized as the cause of angina pectoris >2 centuries ago, and sudden thrombotic occlusion of an epicardial coronary artery has been established as the cause of acute myocardial infarction for >100 years. In the past 2 decades, dysfunction of the coronary microvasculature emerged as an additional mechanism of myocardial ischaemia that bears important prognostic implications. The coronary microvasculature (vessels <300 μm in diameter) cannot be directly imaged in vivo, but a number of invasive and noninvasive techniques, each with relative advantages and pitfalls, can be used to assess parameters that depend directly on coronary microvascular function. These methods include invasive or noninvasive measurement of Doppler-derived coronary blood flow velocity reserve, assessment of myocardial blood flow and flow reserve using noninvasive imaging, and calculation of microcirculatory resistance indexes during coronary catheterization. These advanced techniques for assessment of the coronary microvasculature have provided novel insights into the pathophysiological role of coronary microvascular dysfunction in the development of myocardial ischaemia in different clinical conditions.

Candesartan improves impaired endothelial function in the human coronary artery

Endothelial dysfunction is closely related to cardiovascular events. Several studies have documented that angiotensin II type 1 receptor blockers (ARB) improve peripheral endothelial dysfunction. However, the effect of ARB on coronary endothelial function remains elusive. The purpose of this study was to ascertain the beneficial effects of ARB on human coronary artery endothelial function. Twenty-seven patients were randomly assigned to either the candesartan group (n=14) or the control group (n=13) and followed for 12 months. Coronary blood flow velocity was measured in the left anterior descending artery without stenosis using an intracoronary Doppler-tipped guide-wire. We evaluated coronary endothelial function as the coronary blood flow velocity reserve (CFR), which was defined as the percent change in the coronary blood flow velocity after an intracoronary acetylcholine infusion. At baseline, the CFR in both groups was below 300%, implying that these patients had endothelial dysfunction. After treatment with candesartan for 6 months, the CFR increased significantly from 199 ± 20 to 337 ± 27% (P<0.001), whereas the CFR did not change in the control group (194 ± 32 vs. 185 ± 41%, P=0.52). During 12 months of observation, the cardiovascular event-free survival rate of the patients with an increased CFR was significantly greater than the rate in patients with a decreased CFR (P=0.02). Moreover, the cardiovascular event-free survival rate was greater in the candesartan group than in the control group (P=0.04). Our results suggest that candesartan improves coronary endothelial dysfunction of human coronary arteries and may prevent cardiac events.

The prognostic value of stenosis resistance index after deferral of percutaneous transluminal coronary angioplasty in intermediate coronary lesions showing discordant results between fractional and coronary blood flow velocity reserve

The prognostic value of stenosis resistance index after deferral of percutaneous transluminal coronary angioplasty in intermediate coronary lesions showing discordant results between fractional and coronary blood flow velocity reserve

Rationale of combined intracoronary pressure and flow velocity measurements.

The routine use of sensor-tipped guide wires for the assessment of functional coronary lesion severity has become widespread in the catheterization laboratory. The physiological parameters derived from pressure or flow velocity measurements, fractional flow reserve, relative and absolute coronary blood flow velocity reserve show a high agreement with noninvasive stress testing for myocardial ischemia. However, since these parameters are based on either intracoronary pressure or flow velocity, they do not investigate the hemodynamics of the coronary circulation completely, leading to ambiguous or conflicting outcomes. Only the use of simultaneously measured distal pressure and flow velocity will avoid any possible misinterpretation of the data. We have successfully used an index of stenosis resistance during maximal hyperemia to characterize the functional significance of a coronary stenosis. Recent developments in guide wire technology, currently used for research investigations, put these simultaneous measurements within clinical reach.

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

OBJECTIVESWe 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.BACKGROUNDThere is limited information on the diagnostic accuracy of intracoronary-derived variables (CFVR, FFR and rCFVR) in patients with multivessel disease.METHODSDipyridamole technetium-99m sestambi (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.RESULTSThe 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.CONCLUSIONSThe 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-off values 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.

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

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. 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). 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.

Functional assessment of coronary artery stenosis by Doppler derived absolute and relative coronary blood flow velocity reserve in comparison with 99mTc MIBI SPECT

OBJECTIVETo determine the relation between the relative and absolute coronary blood flow velocity reserve (CFVR) compared with the results of 99mTc MIBI single photon emission computed tomography (SPECT).METHODSIn 37 patients...

Immediate and long-term effect of balloon angioplasty or stent implantation on the absolute and relative coronary blood flow velocity reserve.

There is controversy regarding the immediate and long-term effects of PTCA on the coronary flow reserve. A total of 54 patients with 1-vessel disease and normal left ventricular function were studied after balloon angioplasty (n=34) or stent implantation (n=20). Distal coronary blood flow velocity reserve (CFR) was defined as the ratio of adenosine-induced hyperemic versus baseline blood flow velocity with a 0.014-in Doppler guidewire. The relative CFR was defined as the ratio of the distal CFR and the reference CFR measured in the normal adjacent coronary artery. Hemodynamic and angiographic measurements were performed before and directly after balloon angioplasty or stent implantation and at 6-month follow-up. CFR after PTCA </=2.5 was defined as an impaired CFR. Immediately after PTCA, CFR improved toward the range of the reference artery CFR. In both the balloon-treated and the stent-treated groups, initial high CFR values decreased and impaired CFR values increased at follow-up toward the values of the reference CFR in patients without restenosis. Impaired CFR after balloon angioplasty (33%) or stent implantation (58%) in patients without restenosis was related to an increased baseline flow velocity that normalized at follow-up. Patients with an increase of CFR after stenting were characterized by an unaltered baseline flow velocity and an increased adenosine-induced hyperemic flow velocity. An impaired CFR (</=2.5) is a frequent finding after balloon angioplasty or stent implantation as a result of a high baseline flow velocity. Normalization of impaired CFR at follow-up in patients without restenosis was associated with a decline of the baseline flow velocity after both balloon angioplasty and stent implantation, supporting the contention that this phenomenon relates to a slow recovery of autoregulation of the microvascular bed.

Coronary Flow Reserve During Coronary Angioplasty in Patients With a Recent Myocardial Infarction: Relation to Stenosis and Myocardial Viability

In the present study, we examined post-stenotic coronary flow before and after percutaneous transluminal coronary angioplasty (PTCA) in patients with and without a recent myocardial infarction (MI) and related it to stenosis severity and residual viability. Post-stenotic coronary blood flow velocity reserve (CFVR) has been used with success to estimate functional stenosis severity in patients with stable angina. However, in patients with a recent MI, the impaired coronary vasodilator response of the reperfused myocardium may substantially alter the flow dynamics of the infarct-related artery. Distal coronary flow velocities were recorded before and after PTCA in 36 patients at day 13 +/- 7 (mean +/- SD) after acute MI and in 38 patients without MI. The CFVR was assessed by the ratio of distal hyperemic to baseline average peak velocity, using a 0.014-in. Doppler guide wire. Stenosis severity was analyzed by quantitative coronary angiography, and infarct size was assessed scintigraphically. For similar angiographic stenosis severity, pre- and post-PTCA values of CFVR were significantly lower in patients with than without MI: 1.22 +/- 0.26 versus 1.50 +/- 0.45 before PTCA (p < 0.05) and 1.72 +/- 0.43 versus 2.21 +/- 0.74 after PTCA, respectively (p < 0.01). Although CFVR increased significantly (p < 0.0001) after angiographically successful PTCA in both study groups, abnormal CFVR (< or = 2.0) was still observed in 80% of patients with MI and in 44% of those without MI (MI vs. no MI, p = 0.001). Patients with an extensive infarction (relative infarct size > or = 50%) and those with a small infarction (relative infarct size < 50%) had comparable levels of post-PTCA CFVR (1.6 +/- 0.3 vs. 1.8 +/- 0.5, p = NS). Among a variety of factors, angiographic stenosis severity was the most important determinant of CFVR in both study groups. In patients with a recent MI, CFVR was significantly lower than in those without MI, both before and after PTCA. Besides the presence of this postreperfusion-related impairment of the coronary vasodilating response, CFVR was mainly influenced by stenosis severity and not by residual viability.