Quantification of coronary microvascular resistance using angiographic images for volumetric blood flow measurement: in vivo validation

Takarada

American Journal of Physiology-Heart and Circulatory Physiology

2012

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Coronary flow reserve (CFR) and fractional flow reserve (FFR) are important physiological indexes for coronary disease. The purpose of this study was to validate the CFR and FFR measurement techniques using only angiographic image data. Fifteen swine were instrumented with an ultrasound flow probe on the left anterior descending artery (LAD). Microspheres were gradually injected into the LAD to create microvascular disruption. An occluder was used to produce stenosis. Contrast material injections were made into the left coronary artery during image acquisition. Volumetric blood flow from the flow probe (Q(q)) was continuously recorded. Angiography-based blood flow (Q(a)) was calculated by using a time-density curve based on the first-pass analysis technique. Flow probe-based CFR (CFR(q)) and angiography-based CFR (CFR(a)) were calculated as the ratio of hyperemic to baseline flow using Q(q) and Q(a), respectively. Relative angiographic FFR (relative FFR(a)) was calculated as the ratio of the normalized Q(a) in LAD to the left circumflex artery (LC(X)) during hyperemia. Flow probe-based FFR (FFR(q)) was measured from the ratio of hyperemic flow with and without disease. CFR(a) showed a strong correlation with the gold standard CFR(q) (CFR(a) = 0.91 CFR(q) + 0.30; r = 0.90; P < 0.0001). Relative FFR(a) correlated linearly with FFR(q) (relative FFR(a) = 0.86 FFR(q) + 0.05; r = 0.90; P < 0.0001). The quantification of CFR and relative FFR(a) using angiographic image data was validated in a swine model. This angiographic technique can potentially be used for coronary physiological assessment during routine cardiac catheterization.

Section: Advantages Of the Angiographic Measurement Based On Fpamentioning

confidence: 99%

Quantification of absolute coronary flow reserve and relative fractional flow reserve in a swine animal model using angiographic image data

Takarada

American Journal of Physiology-Heart and Circulatory Physiology

2012

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“…1). Our laboratory's previous report has validated that the angiographic flow based on the FPA technique (Q a) has strong correlations with flow from the flow probe in the swine microvascular disruption model (43).…”

Section: Methodsmentioning

confidence: 82%

“…FPA technique, using angiographic image data, has previously been used to measure absolute coronary blood flow through a stenotic artery (26,27). Our laboratory's previous report (43) focused on validation of the FPA technique in a swine microvascular disruption model. It showed that angiographic NMR measurement based on the FPA technique has good accuracy and reproducibility.…”

Section: H404 Assessment Of Coronary Microcirculation In a Swine Modelmentioning

confidence: 99%

“…In a previous report, an angiographic technique for MR measurement, using a first-pass distribution analysis (FPA) technique in an in vivo coronary microvascular disruption model, was validated (43). The purpose of the present study is to compare the CFR, MR, and P zf at various stages of severity in microvascular disruption and epicardial artery conditions by using both a flow probe as the gold standard and the angiographic method.…”

mentioning

confidence: 99%

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Assessment of coronary microcirculation in a swine animal model

Takarada

American Journal of Physiology-Heart and Circulatory Physiology

2011

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Coronary microvascular dysfunction has important prognostic implications. Several hemodynamic indexes, such as coronary flow reserve (CFR), microvascular resistance, and zero-flow pressure (Pzf), were used to establish the most reliable index to assess coronary microcirculation. Fifteen swine were instrumented with a flow probe, and a pressure wire was advanced into the distal left anterior descending artery. Adenosine was used to produce maximum hyperemia. Microspheres were used to create microvascular dysfunction. An occluder was used to produce stenosis. Blood flow from the probe (Q p), aortic pressure, distal coronary pressure, and right atrium pressure were recorded. Angiographic flow (Q a) was calculated using a time-density curve. Flow probe-based CFR and angiographic CFR were calculated using Q p and Q a, respectively. Flow probe-based (NMRqh) and angiographic normalized microvascular resistance (NMRah) were determined using Q p and Q a, respectively, during hyperemia. Pzf was calculated using Q p and distal coronary pressure. Two series of receiver operating characteristic curves were generated: normal epicardial artery model (N model) and stenosis model (S model). The areas under the receiver operating characteristic curves for flow probe-based CFR, angiographic CFR, NMRqh, NMRah, and Pzf were 0. 855, 0.836, 0.976, 0.956, and 0.855 in N model and 0.737, 0.700, 0.935, 0.889, and 0.698 in S model. Both NMRqh and NMRah were significantly more reliable than CFR and Pzf in detecting the microvascular deterioration. Compared with CFR and Pzf, NMR provided a more accurate assessment of microcirculation. This improved accuracy was more prevalent when stenosis existed. Moreover, NMRah is potentially a less invasive method for assessing coronary microcirculation.angiography; blood flow; cardiovascular imaging; coronary microvascular function CORONARY ANGIOGRAPHY, a routine examination for patients with heart disease, provides an assessment of stenosis severity by visualizing the opacified arterial lumen. However, in many cases (12,40), the severity of myocardium ischemia correlates poorly with epicardial stenosis. Therefore, intracoronary physiological techniques have been developed to provide physiological evaluations for patients who undergo coronary angiography (8,34). Recently, the medical community's interest in coronary microcirculation has grown with the increasing awareness that microvascular dysfunction occurs in a number of myocardial disease states and has important prognostic implications (19,20). With this recognition comes the need for a method to accurately assess the functional capacity of coronary microcirculation for diagnostic purposes and to monitor the effects of therapeutic interventions targeted at reversing the extent of coronary microvascular dysfunction. To assess changes in the microcirculatory bed, several indexes have been proposed, such as coronary flow reserve (CFR), microvascular resistance (MR), and zero-flow pressure (P zf ). In the early 1990s, Gould et al. (14) introduced CFR...

“…The angiographic FFR technique, which includes the effects of both epicardial and microvascular disease, can be used to assess coronary flow reserve (14), microvascular resistance (13,15), as well as FFR to provide a detailed diagnosis for the entire coronary arterial system.…”

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confidence: 99%

Reply to “Letter to the editor: ‘A novel angiographic fractional flow reserve’”

American Journal of Physiology-Heart and Circulatory Physiology

2013

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REPLY: We thank Dr. Yang and colleagues (7a) for their interest in our angiographic fractional flow reserve (FFR) study. This FFR technique, based on first-pass distribution analysis, was validated in a swine animal model. We share their enthusiasm for this angiographic technique that enables direct measurement of coronary flow and FFR for the determination of lesion-specific ischemia.In this study, FFR measurements were made at various stages of severity of microvascular disruption in the left anterior descending artery. Also, an external vascular occluder was used to produce a moderate epicardial stenosis. Therefore, the angiographic FFR technique was validated not only in the microvascular disruption model but also in the epicardial stenosis model (14). However, continued injections of microspheres may cause heterogeneous microinfarcts, which are not the same pathological change as normal myocardial infarction or diffused microvascular disease. The microspheres are not chemoattractant and thus are different from human microvascular disease (1). In human microcircular disease, dysfunction is usually caused by physical obstruction and active thrombogenic, vasoconstrictive, and inflammatory effects and their interactions with the vascular wall. Furthermore, other disease conditions, such as ventricular hypertrophy, diabetes mellitus, flow limiting diffuse coronary artery disease, and previous myocardial infarction, should be considered. The impact of other disease conditions on angiographic FFR requires additional studies.Angiographic FFR is calculated based on angiographic flow measurement. It was validated with direct flow measurements using flow probes, which is the gold standard. Previous studies have also correlated angiographic FFR with pressure-wire derived FFR (4,11,12), which is currently being used for clinical application. The results indicated that the FFR measured from pressure ratios overestimated the measurements using gold standard flow-probe FFR, especially at low FFR values (8). These results were in agreement with a previous report that compared coronary FFR, as defined by flow ratio, to myocardial FFR, calculated by a pressure ratio (10). Pijls et al. (6, 7) compared (P d Ϫ P v )/(P a Ϫ P v ) with the coronary flow ratio, where P d , P v , and P a are coronary distal, coronary venous, and aortic pressures, respectively. Their results showed that with increasing stenosis severity, the coronary flow ratio progressively underestimated the pressure-based index. Siebes et al. (8) and Spaan et al. (9) have demonstrated the curved nature of pressure-flow relation and how this shape relates to the pressure dependence of minimal coronary microvascular resistance (5). As expected, the flow-based FFR and pressure-derived FFR correlated well at the linear range of pressure and flow. The clinical trials that established the guidelines for FFR are based on pressure measurements. Therefore, it will be necessary to perform clinical trials to establish the guidelines of FFR based on angiographic flow measur...