Assessment Of Coronary Stenosis Severity Research Articles

The haemodynamic response to intravenous adenosine and its impact on fractional flow reserve: results of the AFFECTS (Adenosine For the Functional assEssment of Coronary sTenosis Severity) study

The haemodynamic response to intravenous adenosine and its impact on fractional flow reserve: results of the AFFECTS (Adenosine For the Functional assEssment of Coronary sTenosis Severity) study

Abstract 18441: Adenosine-Free Functional Assessment of Coronary Stenosis Severity by Contrast-Induced Submaximal Hyperemia

Background Detection of clinically significant stenoses by fractional flow reserve (FFR) or hyperemic stenosis resistance (HSR) requires maximal vasodilation, which varies with the amount of adenosine (ADO) given. However, the hemodynamic effect of a coronary artery stenosis is uniquely determined by its quadratic pressure gradient-velocity (ΔP- v ) relationship over a range of physiological flow velocities. Hypothesis Functional stenosis severity can be defined from the ΔP- v relationship in terms of the mean pressure gradient at a fixed submaximal velocity (dP v ). Since contrast medium (CM) induces reactive hyperemia, it provides a convenient means to increase flow for this purpose. Methods In 64 patients, aortic pressure (P a ) and intracoronary pressure (P d ) and v distal to an intermediate stenosis were recorded throughout the response to an i.c. ADO injection (30-60 µg). The curve fit (ΔP=A v +B v 2 ) of each ΔP-v relationship was used to obtain the mean dP v at 20, 25, 30, and 40 cm/s. Ischemic cut-off values for each dP v were defined with respect to FFR (=P d /P a ) <0.75 and HSR (=ΔP/ v ) >0.80 mmHg/cm/s. The dP v with the least discordance was used to assess diagnostic performance. Measurements were repeated after i.c. CM injection (3 ml) in 20 patients. Similarity between ADO and CM-derived ΔP- v relationships was evaluated by comparing the dP v at all fixed velocities. Results ADO-based FFR ranged from 0.27 to 0.97 and HSR from 0.08 to 9.12 mmHg/cm/s. Maximal v after CM was 17 ± 16% lower (p<0.01) and P d was 9 ± 11% higher (p<0.001) compared to ADO. Corresponding ADO and CM ΔP-v relationships showed good agreement; no significant differences were found for dP v at any of the tested velocities. Diagnostic performance was highest for dP v at a velocity of 25 cm/s (dP v25 ), with a cut-off >15.8 mmHg. Sensitivity, specificity, and accuracy compared to FFR were 84%, 92% and 87% for ADO and 88%, 92% and 90% for CM-based dP v25 , respectively. Sensitivity, specificity and accuracy were 100% compared to HSR for both ADO and CM-based dP v25 . Conclusion dP v25 is a promising new index of functional stenosis severity that is based on stenosis hemodynamics and yields a high diagnostic accuracy. This index can be obtained from CM injections and obviates problems associated with the use of adenosine.

Abstract 18548: Validation of a New Imaging Parameter, Ultrasonic Intensity of Blood Speckles, Measured by Intravascular Ultrasound for Assessment of Coronary Stenosis Severity Comparing with Fractional Flow Reserve

Background : Little is known regarding intravascular ultrasound (IVUS) criteria to determine functional severity of coronary stenosis. Ultrasonic intensity of blood speckles (IBS) increases as blood flow decreases below coronary stenosis in clinical observation of gray-scale IVUS. The present study was conducted to determine IVUS parameters indicating functional significance of intermediate coronary stenotic lesions. Methods and Results : Thirty consecutive patients with angiographically single intermediate stenotic lesion in left anterior descending coronary artery were enrolled in this study. They were evaluated by means of IVUS and intracoronary pressure measurements. In IVUS analysis conventional gray-scale images were recorded and averaged integrated backscatter (IB) values of blood speckles were measured in cross-sectional vessel lumens at left main trunk (proximal) and 5 mm distal of targeted lesion (distal) using Terumo radiofrequency IVUS (RF-IVUS) system. IBS was defined as difference of IB values between the proximal and the distal sites (distal IB - proximal IB). Fractional flow reserve (FFR) was measured at maximal hyperemia induced by intravenous adenosine infusion. FFR < 0.80 at maximum hyperemia was seen in 19 (63%) of total 30 lesions. IBS had significantly negative correlation with FFR (r = - 0.57, p = 0.001). The optimal cutoff value of IBS for FFR < 0.80 was 10.0 which was obtained from receiver operating characteristic curve (area under curve 0.88; p = 0.001) (Figure). Sensitivity and specificity at the cutoff were 85 % and 70 %, respectively. Also, IBS wasan independent determinant of FFR (H.R. 1.23; 95% confidence interval [CI], 0.008 to 0.031; p = 0.008) in multivariate analysis. Conclusion : IBS, a brand-new IVUS parameter, obtained by RF-IVUS analysis showed a significant correlation to FFR values and can be a predictor for functional significance of epicardial coronary stenosis.

From SYNTAX to FAME, a paradigm shift in revascularization strategies

In patients with chest pain, noninvasive functional assessment prior to cardiac catheterization is often missing or it is inadequate to guide percutaneous coronary revascularization. This is particularly frequent in patients with complex coronary atherosclerotic disease, such as left main stenosis or multivessel disease. Interventional cardiologists are therefore often confronted with diagnostic dilemmas as to which revascularization strategy should be adopted in these patients. A revascularization strategy based on drug-eluting stent (DES) implantation of all the lesions deemed anatomically significant has been increasingly adopted, thanks to the availability of DESs. The down side of this strategy is that DESs are being liberally used even to treat lesions that are not responsible for patients' symptoms (e.g. not ischemic), just on the basis of their angiographic appearance. An alternative approach consists in limiting DES implantation to only the lesions that are indeed responsible for patients' symptoms, like those inducing ischemia, on the basis of fractional flow reserve (FFR). Following the results of important randomized clinical trials, this article discusses the pros and cons of both strategies, underscoring the key role of functional assessment of coronary stenosis severity by FFR.

Letter by Layland et al Regarding Article, “Validation of Intravascular Ultrasound–Derived Parameters With Fractional Flow Reserve for Assessment of Coronary Stenosis Severity”

HomeCirculation: Cardiovascular InterventionsVol. 4, No. 3Letter by Layland et al Regarding Article, “Validation of Intravascular Ultrasound–Derived Parameters With Fractional Flow Reserve for Assessment of Coronary Stenosis Severity” Free AccessLetterPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessLetterPDF/EPUBLetter by Layland et al Regarding Article, “Validation of Intravascular Ultrasound–Derived Parameters With Fractional Flow Reserve for Assessment of Coronary Stenosis Severity” Jamie Layland, Andrew Wilson, Robert Whitbourn and Andrew MacIsaac Jamie LaylandJamie Layland Department of Cardiology St. Vincent's Hospital Melbourne University of Melbourne Melbourne, Australia (Layland, Wilson, Whitbourn, MacIsaac) Search for more papers by this author , Andrew WilsonAndrew Wilson Department of Cardiology St. Vincent's Hospital Melbourne University of Melbourne Melbourne, Australia (Layland, Wilson, Whitbourn, MacIsaac) Search for more papers by this author , Robert WhitbournRobert Whitbourn Department of Cardiology St. Vincent's Hospital Melbourne University of Melbourne Melbourne, Australia (Layland, Wilson, Whitbourn, MacIsaac) Search for more papers by this author and Andrew MacIsaacAndrew MacIsaac Department of Cardiology St. Vincent's Hospital Melbourne University of Melbourne Melbourne, Australia (Layland, Wilson, Whitbourn, MacIsaac) Search for more papers by this author Originally published1 Jun 2011https://doi.org/10.1161/CIRCINTERVENTIONS.111.962043Circulation: Cardiovascular Interventions. 2011;4:e16To the Editor:We read with great interest the study by Kang et al1 that explored the relationship between intravascular ultrasound parameters and fractional flow reserve (FFR) in the assessment of intermediate coronary stenoses.1 We congratulate the authors, who concluded that lesions with a mean luminal area of <2.4 mm2 had a high sensitivity and negative predictive value to predict FFR <0.8, but this was with a poor specificity and positive predictive value. These findings are not unexpected, given that lesion severity is only one of the features that determine the hemodynamic significance of a lesion. The Hagen-Poiseuille equation states that flow in a tube is determined by (ΔPπr4)/(8ιη), where ι and r are length and radius of the tube, respectively, and η the viscosity and ΔP the pressure gradient across the tube. Thus there are other factors that may affect coronary blood flow other than intravascular derived severity of a lesion.Although FFR has been validated in patients studied late after ST-elevation–myocardial infarction,2 Tamita et al3 demonstrated that FFR may underestimate the significance of culprit lesions early after ST-elevation–myocardial infarction. Kang et al4 included patients with non–ST-elevation–myocardial infarction, and there is a paucity of data validating FFR in this population. Microvascular resistance is assumed to be minimal and constant in the simplified FFR calculation. Clinical syndromes that may increase microvascular resistance such as non–ST-elevation–myocardial infarction can affect FFR by altering distal pressure.5The impact of increased lesion length on coronary flow and microvascular resistance on the assessment of FFR require further investigation to better understand the relationship between intravascular ultrasound and FFR parameters.Jamie Layland, MBChB, MRCP, FRACPAndrew Wilson, MBBS, PhD, FRACPRobert Whitbourn, MBBS, FRACPAndrew MacIsaac, MBBS, MD, FRACP Department of Cardiology St. Vincent's Hospital Melbourne University of Melbourne Melbourne, AustraliaDisclosuresDr Layland is supported by a postgraduate research scholarship from the National Health and Medical Research Council of Australia.

Response to Letter Regarding Article, “Validation of Intravascular Ultrasound–Derived Parameters With Fractional Flow Reserve for Assessment of Coronary Stenosis Severity”

We appreciate Dr Layland et al for their interest, and fully agree with the concern that fractional flow reserve (FFR) may underestimate the functional significance of stenotic lesions in patients with ST-segment elevation myocardial infarction (STEMI).1,2 Increased microvascular resistance may have an influence on FFR by altering distal pressure, which is especially remarkable in the culprit lesions with slow flow. Mostly, previous observations were based on “culprits” in the setting of early after STEMI. To the contrary, our inclusion was totally different from the previous studies. Although our data included a small number of patients with …

AS-106 Validation of Intravascular Ultrasound Derived Parameters with Fractional Flow Reserve for Assessment of Coronary Stenosis Severity

AS-106 Validation of Intravascular Ultrasound Derived Parameters with Fractional Flow Reserve for Assessment of Coronary Stenosis Severity

Validation of Intravascular Ultrasound–Derived Parameters With Fractional Flow Reserve for Assessment of Coronary Stenosis Severity

We assessed optimal intravascular ultrasound (IVUS) criteria for predicting functional significance of intermediate coronary lesions. Overall, 201 patients with 236 coronary lesions underwent IVUS and invasive physiological assessment before intervention. Fractional flow reserve (FFR) was measured at maximal hyperemia induced by intravenous adenosine infusion. FFR <0.80 at maximum hyperemia was seen in 49 (21%) of the overall 236 lesions. The independent determinants of FFR were minimal lumen area (MLA; β=0.020; 95% confidence interval [CI], 0.008 to 0.031; P=0.032), plaque burden (β=-0.002; 95% CI, -0.003 to 0.001; P=0.001), lesion length with a lumen area <3.0 mm(2) (β=-0.003; 95% CI, -0.005 to -0.001; P=0.005), and left anterior descending artery location (β=-0.035; 95% CI, -0.055 to -0.016; P=0.001). The best cutoff value (with a maximal accuracy) of the MLA to predict FFR <0.80 was <2.4 mm(2), with a diagnostic accuracy of 68% (90% sensitivity, 60% specificity, and area under the curve=0.800; 95% CI, 0.742 to 0.848; P<0.001). The cutoff value of plaque burden to predict FFR <0.80 was ≥79% (69% sensitivity, 72% specificity, and area under the curve=0.756; 95% CI, 0.696 to 0.810; P<0.001). The cutoff value of lesion length with a lumen area <3.0 mm(2) was 3.1 mm (84%sensitivity, 63%specificity, and area under the curve=0.765; 95% CI, 0.706 to 0.818; P<0.001). Among 117 lesions with an MLA ≥2.4 mm(2), 112 (96%) had an FFR ≥0.80,; and all but 1 showed FFR ≥0.75. Conversely, 44 (37%) lesions with an MLA <2.4 mm(2) had an FFR <0.80. IVUS-derived MLA ≥2.4 mm(2) may be useful to exclude FFR <0.80, but poor specificity limits its value for physiological assessment of lesions with MLA <2.4 mm(2). Thus, FFR or stress tests may be necessary to accurately identify ischemia-inducible intermediate stenoses.

Influence of heart rate on fractional flow reserve, pressure drop coefficient, and lesion flow coefficient for epicardial coronary stenosis in a porcine model

A limitation in the use of invasive coronary diagnostic indexes is that fluctuations in hemodynamic factors such as heart rate (HR), blood pressure, and contractility may alter resting or hyperemic flow measurements and may introduce uncertainties in the interpretation of these indexes. In this study, we focused on the effect of fluctuations in HR and area stenosis (AS) on diagnostic indexes. We hypothesized that the pressure drop coefficient (CDP(e), ratio of transstenotic pressure drop and distal dynamic pressure), lesion flow coefficient (LFC, square root of ratio of limiting value CDP and CDP at site of stenosis) derived from fluid dynamics principles, and fractional flow reserve (FFR, ratio of average distal and proximal pressures) are independent of HR and can significantly differentiate between the severity of stenosis. Cardiac catheterization was performed on 11 Yorkshire pigs. Simultaneous measurements of distal coronary arterial pressure and flow were performed using a dual sensor-tipped guidewire for HR < 120 and HR > 120 beats/min, in the presence of epicardial coronary lesions of <50% AS and >50% AS. The mean values of FFR, CDP(e), and LFC were significantly different (P < 0.05) for lesions of <50% AS and >50% AS (0.88 ± 0.04, 0.76 ± 0.04; 62 ± 30, 151 ± 35, and 0.10 ± 0.02 and 0.16 ± 0.01, respectively). The mean values of FFR and CDP(e) were not significantly different (P > 0.05) for variable HR conditions of HR < 120 and HR > 120 beats/min (FFR, 0.81 ± 0.04 and 0.82 ± 0.04; and CDP(e), 95 ± 33 and 118 ± 36). The mean values of LFC do somewhat vary with HR (0.14 ± 0.01 and 0.12 ± 0.02). In conclusion, fluctuations in HR have no significant influence on the measured values of CDP(e) and FFR but have a marginal influence on the measured values of LFC. However, all three parameters can significantly differentiate between stenosis severities. These results suggest that the diagnostic parameters can be potentially used in a better assessment of coronary stenosis severity under a clinical setting.

On the Inappropriateness of Noninvasive Multidetector Computed Tomography Coronary Angiography to Trigger Coronary Revascularization: A Comparison With Invasive Angiography

Our purpose was to evaluate the appropriateness of multidetector computed tomography angiography (MDCTA) as an anatomical standard for decision making in patients with known or suspected coronary artery disease. Although correlative studies between MDCTA and coronary angiography (CA) show good agreement, MDCTA visualizes plaque burden and calcifications well before luminal dimensions are encroached. Pressure-derived fractional flow reserve (FFR) was obtained in 81 patients (116 vessels) who underwent both CA and MDCTA. Segments were visually graded for stenosis severity as: G0 = normal, G1 = nonobstructive (<50% diameter reduction), and G2 = obstructive (> or =50% diameter reduction). Concordance between segmental severity scores by MDCTA and CA was good (k = 0.74; 95% confidence interval: 0.56 to 0.92). Diagnostic performance of MDCTA for detection of functionally significant stenosis based on FFR was low (sensitivity 79%; specificity 64%; positive likelihood ratio 2.2; negative likelihood ratio 0.3). Revascularization was considered appropriate in the presence of reduced FFR (< or =0.75). Decision making based on MDCTA guidance would result in revascularization in the absence of ischemia in 22% of patients (18 of 81) and inappropriate deferral in 7% (6 of 81), while revascularization in the absence of ischemia would be 16% (13 of 81) and inappropriate deferral 12% (10 of 81) with decisions guided by CA. Combined evaluation of stenosis severity using both anatomy (with either CA or MDCTA) and function (with FFR) yields the highest proportion of appropriate decisions: 90% and 91%, respectively (p = 0.0001 vs. CA only, p = 0.0001 vs. MDCTA only). Similar to CA, anatomical assessment of coronary stenosis severity by MDCTA does not reliably predict its functional significance.

Noninvasive quantification of coronary blood flow reserve in humans using myocardial contrast echocardiography.

We hypothesized that coronary blood flow (CBF) reserve could be quantified noninvasively in humans using myocardial contrast echocardiography (MCE). Eleven patients with normal epicardial coronary arteries (group I) and 19 with single-vessel coronary stenosis (group II) underwent quantitative coronary angiography, MCE, and CBF velocity measurements at rest and during intravenous adenosine infusion. In group I patients, MCE-derived myocardial blood flow (MBF) velocity reserve (2.4+/-0.08) was similar to CBF velocity reserve using a Doppler flow wire (2.4+/-1.1). Patients with a single risk factor had a significantly higher MBF reserve (3.0+/-0.89) than those with >/=2 risk factors (1.7+/-0.22). In group II patients, significant differences were found in MBF velocity reserve in patients with mild (<50%), moderate (50% to 75%), or severe (>75%) stenoses (2.2+/-0.40, 1.6+/-0.65, and 0.55+/-0.19, respectively; P=0.005). A linear relation was found between flow velocity reserve determined using the 2 methods (r=0.76, P<0.001), and a curvilinear relation was noted between the percent coronary stenosis measured using quantitative coronary angiography and velocity reserve using both methods. CBF reserve can be measured in humans using MCE. This method may allow the noninvasive assessment of coronary stenosis severity and the detection of microvascular dysfunction.

Assessment of coronary stenosis severity and transmural perfusion gradient by myocardial contrast echocardiography: comparison of gray-scale B-mode with power Doppler imaging.

The present study (1) compared the ability of power Doppler imaging with that of gray-scale B-mode tissue imaging to opacify the myocardium and detect coronary stenosis by myocardial contrast echocardiography and (2) compared the response of video intensity (VI) to variable pulsing intervals for each modality. Four grades of left anterior descending coronary artery (LAD) stenoses were created in 9 open-chest dogs. Stenoses reduced resting LAD flow by 25%, 50%, 75%, and 100% of baseline by flow probe. Myocardial contrast echocardiography was performed during varying ECG gated pulsing intervals (PIs) from 1:1 to 1:10. By gray-scale imaging, background-subtracted LAD bed VI was less than baseline VI at all PIs for the 100% reduced-flow state but not for any other flow state or interval. By power Doppler imaging, LAD bed VI was less than baseline VI at all intervals for 75% and 100% reduced-flow states but only 1:1 and 1:2 for 25% and 50% reduced-flow states, respectively. Correlation of VI and myocardial blood flow (determined by use of fluorescent microspheres) ratios from stenosed versus normal beds was stronger by power Doppler imaging. A transmural opacification gradient with stenosis was visualized and measured by power Doppler imaging, but it was insignificant by gray-scale imaging. The ratio of endocardial/epicardial flow determined by use of fluorescent microspheres was correlated with VI by power Doppler imaging at all PIs. Power Doppler imaging has advantages compared with gray-scale imaging in opacifying the myocardium and in detecting coronary stenosis and altered transmural distribution of myocardial perfusion from peak VI. Because VI differences from baseline at long PI vary for mild versus severe (75% and 100%, respectively) reduced-flow states, power Doppler imaging may provide a method to quantify coronary stenoses.

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

OBJECTIVESTo validate intravascular ultrasound (IVUS) measurements for differentiating functionally significant from nonsignificant coronary stenosis.BACKGROUNDTo date, there are no validated criteria for the definition of a flow-limiting coronary artery stenosis by IVUS.METHODSPreinterventional 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.RESULTSThe 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 ≤4 mm2is a simple and highly accurate criterion for significant coronary narrowing.CONCLUSIONSQuantitative IVUS indices can be reliably used for identifying significant epicardial coronary artery stenoses.

Improved Assessment of Coronary Stenosis Severity Using the Relative Flow Velocity Reserve

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. 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). 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.

Comparison of pressure-derived fractional flow reserve with poststenotic coronary flow velocity reserve for prediction of stress myocardial perfusion imaging results

The physiologic importance of coronary stenoses can be assessed indirectly by stress myocardial perfusion imaging or directly by translesional pressure and flow measurements. The aims of this study were to compare myocardial fractional flow reserve (FFR myo), a recently proposed index of lesion significance derived from hyperemic translesional pressure gradients, with directly measured poststenotic flow velocity reserve for the prediction of myocardial perfusion stress imaging results in corresponding vascular beds. Poststenotic coronary flow velocity (0.018-inch guide wire) and translesional pressure gradients (2.7F fluid-filled catheter) were measured at baseline and after intracoronary adenosine (12 to 18 μg) in 70 arteries (diameter stenosis: mean 56% ± 15%, range 14% to 94% by quantitative angiography). Coronary flow reserve was calculated as the ratio of hyperemic to basal mean flow velocity. FFR myo was calculated during maximal hyperemia as equal to 1 — (hyperemic gradient [mean aortic pressure — 5]), where 5 is the assumed central venous pressure. Positive and negative predictive values and predictive accuracy for reversible stress myocardial perfusion abnormalities were computed. There was a significant correlation between pressure-derived FFR myo and distal coronary flow reserve ( r = 0.46; p < 0.0001). The strongest predictor of stress myocardial perfusion imaging results was the poststenotic coronary flow reserve (chi square = 33.2; p < 0.0001). The correlation between stress myocardial perfusion imaging and FFR myo was also significant (chi square = 8.3; p < 0.005). There was no correlation between stress myocardial perfusion imaging and percentage diameter stenosis (chi square = 2.9; p = 0.10) or minimal lumen diameter (chi square = 0.47; p = 0.73). A poststenotic coronary flow reserve of ≤2 had a positive predictive value of 89% for regionally abnormal myocardial perfusion imaging abnormalities, whereas the positive predictive values of FFR myo and angiographic percentage diameter stenosis were only 71% and 67% respectively. In conclusion, the predictive value of poststenotic coronary flow velocity reserve for stress-induced myocardial perfusion abnormalities exceeds that of the translesional FFR myo. These findings should be considered when applying these techniques for clinical decision making in the assessment of coronary stenosis severity.

Assessment of coronary stenosis severity by a Doppler guidewire

Assessment of coronary stenosis severity by a Doppler guidewire

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

In vitro and animal experiments have shown that the severity of coronary stenoses can be assessed using the continuity equation if the maximal blood flow velocity of the stenotic jet is measured. The large diameter and the low range of velocities measurable without frequency aliasing with the conventional intracoronary Doppler catheters precluded the clinical application of this method for hemodynamically significant coronary stenoses in humans. This article reports the results obtained using a 12 MHz steerable angioplasty guidewire in a consecutive series of 52 patients undergoing percutaneous coronary angioplasty (61 coronary stenoses). The ratio between coronary flow velocity in a reference segment and in the stenosis was used to estimate the percent cross-sectional area stenosis. A Doppler recording suitable for quantization was obtained in the stenotic segment in only 10 of 61 arteries (16%). The time-averaged peak velocity increased from 15 ± 5 to 115 ± 26 cm/sec from the reference normal segment to the stenosis. Volumetric coronary flow calculated from the product of mean flow velocity and cross-sectional area was similar in the stenosis and in the reference segment (33.2 ± 14.9 vs 33.5 ± 17.0 ml/ min, respectively, difference not significant). The percent cross-sectional area stenosis and minimal luminal cross-sectional area derived from the Doppler velocity measurements using the continuity equation and calculated with quantitative angiography were also similar (Doppler, 86.7 ±5.1% and 1.00 ± 0.48 mm 2; quantitative angiography, 85.9 ± 7.9% and 1.02 ± 0.50 mm 2). A significant correlation was observed between Doppler-derived and angiographic measurements (percent cross-sectional area: r = 0.64, p < 0.05; minimal cross-sectional area: r = 0.69, p < 0.05). Although the percent cross-sectional area stenosis and minimal cross-sectional area derived from the Doppler measurements based on the continuity equation were significantly correlated with the corresponding quantitative angiographic measurements, this determination could be achieved in a minority of cases (16%), limiting the practical application of this approach for the assessment of coronary stenosis severity.

Assessment of the hemodynamic significance of coronary artery stenosis: Theoretical considerations and clinical measurements

ISUAL ASSESSMENT of the diameter percentage of stenosis of a diseased coronary artery still remains the “gold standard” in more than 99% of hospitals that perform coronary angiography.’ Several experimental studies have shown that percent diameter stenosis, under carefully controlled conditions, provides a useful index of the significance of a coronary lesion.*-” However, the general applicability of this index to clinical coronary disease, especially when it is diffuse and affects more than one vessel, has been seriously questioned.‘*” Furthermore, subjective assessment of the extent of a coronary obstruction has been found to correlate poorly with pathoanatomic findingP’ and to suffer significant interobserver and intraobserver variability.2”-28 With the appearance of more accurate, objective methods for the assessment of stenotic dimensions,‘9-3’ it became possible to overcome many of the limitations of the subjective visual approximation of percent diameter stenosis alone. Visual assessment can be avoided with the use of computer programs that analyze the coronary lesion either by automated borderdetection of the affected vessel29 or by densitometric analysis that makes use of the concept that, in an ideal setting, the density across an artery in a radiographic image is proportional to the cross-sectional area at that point.“’ In addition, other indices of the stenosis severity such as the absolute cross-sectional area of the stenosis have been proposed32 and can be now easily and reproducibly obtained. This anatomic/ geometric assessment of coronary stenosis severity has been further expanded by the development of more comprehensive methods that take into account all the dimensions of the lesion as measured on coronary angiograms.33 Furthermore, several methods for the assessment of the physiological significance of the stenosis by measuring the coronary flow reserve have been developed.34”5 These techniques are based on actual measurements of coronary flow or evaluation of myocardial perfusion, thus comprising a functional/physiological approach to assessing the impact of the lesion on the coronary circulation. All these indices with their limitations, have been used as single measures of the stenosis severity. Their value to predict the haemodynamic significance of any lesion has been examined and this review will analyze in detail the theoretic and experimental data describing these different indices of stenosis severity.

Clinical cardiac PET using generator-produced Rb-82: A review

Cardiac positron emission tomography (PET) with generator-produced rubidium-82 (Rb-82) provides information not previously available for optimal diagnosis and management of cardiac disease. This new information includes the accurate, noninvasive diagnosis of coronary artery disease in asymptomatic or symptomatic patients, the noninvasive assessment of coronary stenosis severity, myocardial infarct imaging, myocardial viability, collateral function, and cardiomyopathy. Cardiac positron imaging may be carried out economically at the same or less cost as other high-tech diagnostic imaging but provides perfusion and metabolic information quantitatively for routine clinical studies not available by other diagnostic modalities.