Measurement Of Coronary Flow Reserve Research Articles

Optimal Diagnostics and Therapy for Microvascular Angina Pectoris

Patients with microvascular angina are characterized by angina pectoris with proof of myocardial ischemia in the absence of any relevant epicardial stenosis and without myocardial disease (type 1 coronary microvascular dysfunction according to Crea and Camici). Structural and functional alterations of the coronary microvessels (diameter < 500 µm) are the reason for this phenomenon. Frequently such alterations are associated with cardiovascular risk factors. Patients with angina pectoris without epicardial stenoses represent for 10 - 50 % of all patients undergoing coronary angiography depending on the clinical presentation. Diagnostic approaches include non-invasive (e. g. combination of coronary CT-angiography and positron emission tomography/echo Doppler-based coronary flow reserve measurements) as well as invasive procedures (coronary flow reserve measurements in response to adenosine, intracoronary acetylcholine testing). Pharmacological treatment of these patients is often challenging and should be based on the characterization of the underlying mechanisms. Moreover, strict risk factor control and individually titrated combinations of antianginal substances (e. g. beta blockers, calcium channel blockers, nitrates, ranolazine, ivabradine etc.) are recommended.

TCT-134 Impact of post-percutaneous coronary intervention fractional flow reserve measurement on procedural management and clinical outcomes: the REPEAT-FFR Study

TCT-134 Impact of post-percutaneous coronary intervention fractional flow reserve measurement on procedural management and clinical outcomes: the REPEAT-FFR Study

Clues to Discordance and Dissimilarity Between Coronary Stenosis and Lesion-Specific Ischemia

Traditional diagnostic accuracy statistics have defined discordance between a stenosis and preserved coronary blood flow as a false-positive finding. With expanded use of invasive and noninvasive fractional flow reserve (FFR), as well as positron emission tomography measures of coronary flow reserve, our knowledge base has grown substantially, providing greater insight into the underlying rationale for discordant findings. We now understand that the presence of an obstructive stenosis is but one parameter which may elicit reductions in blood flow and prompt ischemic symptoms. Vessel size, collateral flow, and the length of the diseased segment are a few of the factors influencing coronary blood flow.1 Thus, for any given patient with an obstructive stenosis, reductions in coronary blood flow may or may not be present. Throughout the prior reported series,2,3 limited evidence is available with regards to coronary stenosis severity and location, as well as clinical patient subgroups, where the disconnect between stenosis severity and lesion-specific ischemia with FFR may …

Usefulness of coronary flow reserve measured by transthoracic coronary Doppler ultrasound in the elderly.

The left anterior descending (LAD) coronary artery is the main vessel of human coronary circulation, and life-threatening consequences are seen when flow in this area is impaired.[1] Noninvasive measurement of coronary flow reserve (CFR), defined as the ratio of maximal to baseline coronary blood flow, has been repeatedly shown to be a feasible technique by ultrasound transthoracic Doppler (TTD) both in the LAD and, with some limitations, in the posterior descending (PD) coronary artery.[2]–[7] CFR by TTD offers two important pieces of information: information about patency and flow through the large epicardial coronary artery proximal to the site of CFR assessment and information about the functional integrity of coronary microcirculation distal to the site of CFR assessment.[4] CFR by TTD is a valuable research tool for investigating the pathophysiology of coronary circulation. However, CFR by TTD is also an important clinical decision-making instrument, enabling functional assessment of epicardial coronary stenosis, particularly in cases of anatomically borderline stenosis, i.e., 50%–70% of cases.[8] CFR by TTD enables insight downstream into coronary microvascular function that might be impaired due to primary coronary microvascular disease, as a consequence of myocardial diseases with extramural compression and microvascular remodeling and rarefaction (in left ventricular hypertrophy, dilated or hypertrophic cardiomyopathy, or aortic stenosis), or as a consequence of microvascular obstruction due to micro-embolization by plaque and thrombus debris during percutaneous coronary interventions.[9] Epicardial coronary artery patency and flow may be particularly jeopardized in the elderly as a result of advanced atherosclerosis (a disease of aging). Coronary microcirculatory function might also be impaired in the elderly even in the absence of obstructive epicardial atherosclerosis due to accumulated risk factors (e.g., hypertension, diabetes, obesity) and co-morbidities (e.g., chronic kidney, aortic stenosis).[10],[11] As a technique that is noninvasive, inexpensive, easily repeatable, and that does not require radiation, TTD CFR may be very useful in the fragile population of the elderly, offering a better understanding of coronary vascular aging as well as clinically important information regarding the diagnosis and prognosis of coronary artery disease.

Síndrome cardíaco X. Angina vasoespástica. Isquemia silente

Cardiac syndrome XThis is a clinical entity consisting of typical exertional angina, documented myocardial ischaemia and normal coronary arteries, in the absence of other heart disease. It pathogenic mechanisms are microvascular dysfunction and abnormal perception of chest pain. Stress echocardiogram with ST changes and chest pain with no parietal mobility anomalies supports the diagnosis. Measurement of coronary flow reserve during Doppler ultrasound of the anterior descending artery is an objective test of microvascular dysfunction. Vasospastic anginaThis comprises episodes of chest pain secondary to occlusive focal spasm of the epicardial arteries that normally present with ST elevation, as well as the more frequent episodes caused by diffuse distal spasm, with an ST descent. Tests that induce vasospasm are generally used to confirm the diagnosis such as intracoronary injection of acetylcholine. Silent ischaemiaAngina is a poor marker of mycoardial ischaemia, silent ischaemia is the most frequent manifestation of heart disease. In its most common form, type III, it coexists with angina of any type. Its diagnosis requires confirmation of myocardial ischaemia, usually by exercise stress test or Holter monitoring, in the absence of chest pain. The aim should be to treat the ischaemia, not just the angina.

Angiotensin-Converting Enzyme Inhibition Early After Heart Transplantation

BackgroundCardiac allograft vasculopathy (CAV) remains a leading cause of mortality after heart transplantation (HT). Angiotensin-converting enzyme inhibitors (ACEIs) may retard the development of CAV but have not been well studied after HT. ObjectivesThis study tested the safety and efficacy of the ACEI ramipril on the development of CAV early after HT. MethodsIn this prospective, multicenter, randomized, double-blind, placebo-controlled trial, 96 HT recipients were randomized to undergo ramipril or placebo therapy. They underwent coronary angiography, endothelial function testing; measurements of fractional flow reserve (FFR) and coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR); and intravascular ultrasonography (IVUS) of the left anterior descending coronary artery, within 8 weeks of HT. At 1 year, the invasive assessment was repeated. Circulating endothelial progenitor cells (EPCs) were quantified at baseline and 1 year. ResultsPlaque volumes at 1 year were similar between the ramipril and placebo groups (162.1 ± 70.5 mm3 vs. 177.3 ± 94.3 mm3, respectively; p = 0.73). Patients receiving ramipril had improvement in microvascular function as shown by a significant decrease in IMR (21.4 ± 14.7 to 14.4 ± 6.3; p = 0.001) and increase in CFR (3.8 ± 1.7 to 4.8 ± 1.5; p = 0.017), from baseline to 1 year. This did not occur with IMR (17.4 ± 8.4 to 21.5 ± 20.0; p = 0.72) or CFR (4.1 ± 1.8 to 4.1 ± 2.2; p = 0.60) in the placebo-treated patients. EPCs decreased significantly at 1 year in the placebo group but not in the ramipril group. ConclusionsRamipril does not slow development of epicardial plaque volume but does stabilize levels of endothelial progenitor cells and improve microvascular function, which have been associated with improved long-term survival after HT. (Angiotensin Converting Enzyme [ACE] Inhibition and Cardiac Allograft Vasculopathy; NCT01078363)

Neointimal Healing Evaluated by Optical Coherence Tomography after Drug-Eluting Absorbable Metal Scaffold Implantation in de novo Native Coronary Lesions: Rationale and Design of the Magmaris-OCT Study

Objectives: We sought to explore neointimal healing assessed by optical coherence tomography (OCT) following implantation of the Magmaris sirolimus-eluting absorbable metal scaffold. Methods: The Magmaris-OCT is a prospective, multicenter, single-arm observational clinical study, intended to enrol 60 consecutive patients with up to 2 de novo native coronary lesions, each located in different major epicardial vessels, with a reference vessel diameter of 2.5-3.5 mm, and a maximum lesion length of 20 mm. Patients will undergo Magmaris scaffold implantation in the target lesion, according to the standard practice. Clinical follow-up will take place at 30 days, and at 3, 6, 9, and 12 months. For invasive-imaging follow-up, patients will be classified into 3 groups: cohort A will be scheduled for follow-up at 3 months, cohort B at 6 months, and cohort C at 12 months. Invasive imaging will include quantitative coronary angiography, OCT evaluation, and coronary flow reserve measurement. The primary end point will be the percentage of uncovered scaffold struts assessed by OCT at the prespecified follow-up. Conclusions: This study will provide insight into the short- and mid-term healing properties following Magmaris scaffold implantation, with special emphasis on the neointimal coverage of scaffold struts.

Impact of high serum Immunoglobulin E levels on the risk of atherosclerosis in humans.

BackgroundEpidemiological studies show that immunoglobulin E (IgE) levels were higher in subjects with acute coronary events. However, it is unknown if the increased IgE level is a marker of future coronary incidents and whether it may be regarded as a risk factor of an ischemic heart disease.ObjectiveOur aim was to investigate the relationship between IgE levels and some atherosclerotic markers in patients without known atherosclerotic disease.MethodsFifty patients (mean age, 40.96 ± 10.8 years) with high serum IgE levels due to various conditions who did not display evidence of an atherosclerotic disease and 30 healthy control subjects (mean age, 47 ± 8.27 years) were included in the study. Atherosclerotic disease markers including adhesion molecules like vascular cell adhesion molecule-1, intercellular adhesion molecule-1, proinflammatory cytokines such as interleukin-6, endothelin-1, and systemic inflammatory markers such as high sensitivity C-reactive protein were determined by enzyme-linked immunosorbent assay (ELISA). Endothelial functions of the coronary arteries were determined by coronary flow reserve (CFR) measurements and carotid intima media thickness using transthoracic Doppler echocardiography.ResultsCFR was significantly lower in the patient group when compared with the control group (p<0.001; 95% confidence interval, -0.79 to-0.20) while carotid media thicknesses were not different between 2 groups. There were no differences in ELISA test results between the 2 groups.ConclusionOur results showed that CFR as an early marker of endothelial dysfunction was significantly lower in patients with high IgE levels. This finding seems to support the role of IgE in the vascular pathology of atherosclerosis.

Anomalous Coronary Arteries and Myocardial Bridges: Risk Stratification in Children Using Novel Cardiac Catheterization Techniques.

The evaluation of the vast majority of children with anomalous aortic origin of a coronary artery (AAOCA) and/or myocardial bridges is performed with non-invasive testing. However, a subset of these patients may benefit from invasive testing for risk stratification. All patients included in the Coronary Anomalies Program (CAP) at Texas Children's Hospital who underwent cardiac catheterization were included. Techniques included selective coronary angiograms (SCA), intravascular ultrasound (IVUS), and fractional flow reserve (FFR) measurements with provocative testing using adenosine and/or dobutamine infusions. Out of the 131 patients followed by the CAP between 12/12-4/16, 8 (6%) patients underwent 9 cath investigations at median age 13.1 (2.6-18.7) years and median weight 49.5 (11.4-142.7) kg. Six patients presented with cardiac signs/symptoms. Four patients had myocardial bridges of the left anterior descending (LAD) coronary artery, 2 patients had isolated AAOCA, and 2 patients had an anomalous left coronary artery (LCA) with an intramyocardial course of the LAD. SCA was performed in all patients. FFR was positive in 4/6 patients: IVUS showed >70% intraluminal narrowing in 3/5 patients. One patient had hemodynamic instability that reversed with catheter removal from the coronary ostium. Based on the catheterization data obtained, findings were reassuring in three patients, surgery was performed in three patients, and two patients are being medically managed/restricted from competitive sports. In our small cohort of patients, we demonstrated that IVUS and FFR can safely be performed in children and may help to risk stratify some patients with AAOCA and myocardial bridges.

473 - Coronary Fractional Flow Reserve (FFR) measurement: which method of adenosine administration is the safest?

473 - Coronary Fractional Flow Reserve (FFR) measurement: which method of adenosine administration is the safest?

Coronary fractional flow reserve measurements of a stenosed side branch: a computational study investigating the influence of the bifurcation angle.

BackgroundCoronary hemodynamics and physiology specific for bifurcation lesions was not well understood. To investigate the influence of the bifurcation angle on the intracoronary hemodynamics of side branch (SB) lesions computational fluid dynamics simulations were performed.MethodsA parametric model representing a left anterior descending—first diagonal coronary bifurcation lesion was created according to the literature. Diameters obeyed fractal branching laws. Proximal and distal main branch (DMB) stenoses were both set at 60 %. We varied the distal bifurcation angles (40°, 55°, and 70°), the flow splits to the DMB and SB (55 %:45 %, 65 %:35 %, and 75 %:25 %), and the SB stenoses (40, 60, and 80 %), resulting in 27 simulations. Fractional flow reserve, defined as the ratio between the mean distal stenosis and mean aortic pressure during maximal hyperemia, was calculated for the DMB and SB (FFRSB) for all simulations.ResultsThe largest differences in FFRSB comparing the largest and smallest bifurcation angles were 0.02 (in cases with 40 % SB stenosis, irrespective of the assumed flow split) and 0.05 (in cases with 60 % SB stenosis, flow split 55 %:45 %). When the SB stenosis was 80 %, the difference in FFRSB between the largest and smallest bifurcation angle was 0.33 (flow split 55 %:45 %). By describing the ΔPSB−QSB relationship using a quadratic curve for cases with 80 % SB stenosis, we found that the curve was steeper (i.e. higher flow resistance) when bifurcation angle increases (ΔP = 0.451*Q + 0.010*Q2 and ΔP = 0.687*Q + 0.017*Q2 for 40° and 70° bifurcation angle, respectively). Our analyses revealed complex hemodynamics in all cases with evident counter-rotating helical flow structures. Larger bifurcation angles resulted in more pronounced helical flow structures (i.e. higher helicity intensity), when 60 or 80 % SB stenoses were present. A good correlation (R2 = 0.80) between the SB pressure drop and helicity intensity was also found.ConclusionsOur analyses showed that, in bifurcation lesions with 60 % MB stenosis and 80 % SB stenosis, SB pressure drop is higher for larger bifurcation angles suggesting higher flow resistance (i.e. curves describing the ΔPSB−QSB relationship being steeper). When the SB stenosis is mild (40 %) or moderate (60 %), SB resistance is minimally influenced by the bifurcation angle, with differences not being clinically meaningful. Our findings also highlighted the complex interplay between anatomy, pressure drops, and blood flow helicity in bifurcations.

Assessment of coronary flow reserve using a combination of planar first-pass angiography and myocardial SPECT: Comparison with myocardial 15O-water PET

Coronary flow reserve (CFR), defined as the ratio of maximum coronary flow increase from baseline resting blood flow, is one of the most sensitive parameters to detect early signs of coronary arteriosclerosis at the microvascular level. Myocardial perfusion PET is a well-established technology for CFR measurement, however, availability is still limited. The aim of this study is to introduce and validate myocardial flow reserve measurement by myocardial perfusion SPECT. MethodsMyocardial perfusion SPECT at rest and ATP stress (0.16mg/Kg/min) was performed in 10 patients with known coronary artery disease. Immediately after the injection of Tc-99m sestamibi (MIBI), left ventricular (LV) dynamic planar angiographic data were obtained for 90s. Coronary flow reserve index as measured by MIBI SPECT (CFRMIBI) was calculated as follows: CFRMIBI=CmsSbmb/CmbSbms, where subscripts b, s, Cm, and Sbm indicate baseline, during stress, myocardial counts with MIBI SPECT, and integral of LV counts with first pass angiography, respectively. Additionally, standard stress/rest 15O-water PET to estimate CFR was performed in all patients as standard of reference. ResultsCFRMIBI increased in conjunction with CFR, but underestimated blood flow at high flow rates. The relationship between CFRMIBI (Y) and CFRPET (X) was well fitted as follows: Y=1.40x(1-exp(1.79/x)) (r=0.84). ConclusionsThe index of CFRMIBI reflects the CFR by 15O-water PET but underestimates flow at high flows, maybe as a reflection of pharmacokinetic limitations of MIBI.

Serial Assessment of Transthoracic Coronary Flow Reserve as Method of Assessing Efficacy of Intracoronary Intervention in the Left Anterior and Posterior Descending Arteries

The study group comprised 14 patients with single-vessel coronary disease (stenosis 82+/-14%) of the LAD (9 patients) or right coronary artery (RCA, 5 patients) scheduled for stent implantation. All patients underwent dipyridamole stress echo with CFR evaluation of either distal LAD or PDA 1 day before and 6-9 days after successful stent implantation. CFR was calculated as the ratio of hyperemic to basal peak diastolic velocity. A CFR value of <2.0 was considered abnormal. Adequate Doppler signals to measure CFR were obtained in 13 patients (93%). Abnormal pre-procedure CFR value was revealed in 12 assessed patients (92%). Significant increase of CFR due to a decrease of coronary flow velocity at rest and its more pronounced hyperemic rise was found in all patients after stent implantation (CFR: 1.28+/-0.52 before and 2.53+/-0.37 after stenting; p<0.001). Using a cut-off value of CFR more or equal 2.0 to identify absence of significant coronary artery disease, TTE detected successful stent implantation with a sensitivity of 91.7% and specificity of 100% for both LAD and RCA. CFR was still abnormal in only 1 patient with pre-procedure>90% LAD stenosis. TTE is a feasible technique for serial CFR evaluation in LAD and PDA. Cut-off CFR value more or equal 2.0 is a sensitive and specific criterion of successful stent implantation in LAD and RCA.

Effect of chronic inflammation on coronary arteries in renal amyloidosis: More than renal dysfunction

Effect of chronic inflammation on coronary arteries in renal amyloidosis: More than renal dysfunction

Diabetes mellitus and coronary microvascular function in asymptomatic patients with severe aortic stenosis and nonobstructed coronary arteries.

Coronary flow reserve is impaired in asymptomatic patients with aortic stenosis and has a prognostic value. We investigated whether the type II diabetes mellitus additionally impairs microvascular circulation assessed by coronary flow reserve in patients with asymptomatic severe aortic stenosis, normal left ventricular ejection fraction and nonobstructed coronary arteries. A total of 128 patients, mean age of 66.35 ± 10.51 (58.6% males), with severe aortic stenosis and normal left ventricular ejection fraction were enrolled in this study. Patients with diabetes mellitus, those who were treated for diabetes mellitus or had documentation confirming the diagnosis of diabetes mellitus, were considered. All patients underwent coronary angiography and had no obstructive coronary disease (defined as having no stenosis >50% in diameter), standard transthoracic Doppler-echocardiographic study and adenosine stress transthoracic echocardiography for coronary flow reserve measurement. Diabetes mellitus was present in 26 patients (20.31%). There was no significant difference in aortic stenosis severity between diabetic and non-diabetic patients [aortic valve area (0.81 ± 0.18 vs 0.85 ± 0.15 cm(2)) and Vmax (4.20 ± 0.57 vs 4.21 ± 0.48 m/s)]. Mean coronary flow reserve in diabetic patients was 1.98 ± 0.48, while mean coronary flow reserve in non-diabetic patients was 2.64 ± 0.54 (p < 0.01). Diabetes mellitus was independent predictor of coronary flow reserve [B = -0.636, 95% confidence interval (-0.916 to -0.368), p < 0.001]. Diabetes mellitus additionally impairs coronary microvascular function in asymptomatic patients with severe aortic stenosis and nonobstructed coronary arteries.

Imaging- and physiology-guided percutaneous coronary intervention without contrast administration in advanced renal failure: a feasibility, safety, and outcome study

The feasibility, safety, and clinical utility of percutaneous coronary intervention (PCI) without radio-contrast medium in patients with advanced chronic kidney disease (CKD) are unknown. In this series, we investigated a specific strategy for 'zero contrast' PCI with the aims of preserving renal function and preventing the need for renal replacement therapy (RRT) in patients with advanced CKD. A total of 31 patients with advanced CKD [creatinine = 4.2 mg/dL, inter-quartile range (IQR) 3.1-4.8, estimated glomerular filtration rate = 16 ± 8 mL/min/1.73 m2] who had clinical indication for PCI based on a prior minimal contrast coronary angiogram were included. Zero contrast PCI was performed at least 1 week after diagnostic angiography using real-time intravascular ultrasound (IVUS) guidance, with pre- and post-PCI measurements of fractional flow reserve and coronary flow reserve to confirm physiological improvement. This approach resulted in successful PCI, no major adverse cardiovascular events and preservation of renal function without the need for RRT within a follow-up time of 79 days (IQR 33-207) in all patients. In patients with advanced CKD who require revascularization, PCI may safely be performed without contrast using IVUS and physiological guidance with high procedural success and without complications.

CT myocardial perfusion and coronary CT angiography: Influence of coronary calcium on a stress–rest protocol

BackgroundHigh amounts of coronary artery calcium limit image quality and diagnostic accuracy of multidetector computed tomography (MDCT) angiography (CTA) regarding the assessment of obstructive coronary artery disease (CAD). CT myocardial perfusion imaging may represent an opportunity to overcome this limitation. ObjectiveTo explore the additive value of CT myocardial perfusion to CTA depending on the patient's calcium score and in comparison to the reference standard of invasive coronary angiography plus fractional flow reserve (FFR) measurement. MethodsSymptomatic patients with intermediate pretest probability of CAD were prospectively recruited and underwent both cardiac MDCT (64-slice scanner, retrospectively-gated stress–rest protocol) and invasive coronary angiography including FFR assessment. We defined hemodynamically significant CAD by the presence of occlusive or subocclusive (99%) stenosis, >50% stenosis in left main or FFR≤0.80. Stress CT myocardial perfusion imaging was performed in all patients in addition to CTA. The additive value of CT myocardial perfusion to rule in or rule out the presence of hemodynamically relevant stenosis on a per-patient basis was assessed and analyzed relative to the patient's calcium score. Results95 patients were included in the analysis (62 ± 8.2 years, 68%males). Hemodynamically significant CAD was present in 42 patients. Sixty-four patients had a fully evaluable CTA examination. Per-patient, CTA alone had a sensitivity, specificity and AUC of 100%, 59% and 0.79 respectively (77% patients correctly classified). Adding CT myocardial perfusion to evaluate uninterpretable vessel territories in CTA in 66 patients with a calcium score>100 yielded a sensitivity of 88%, a specificity of 74% and an AUC of 0.81 (81% patients correctly classified), and in 52 patients with a calcium score>400 sensitivity was 91%, specificity 70%, and AUC 0.80 (82% patients correctly classified, p = 0.733 versus using perfusion imaging in all patients). ConclusionsFrom a pragmatic standpoint, limiting the use of CT perfusion to individuals with a calcium score above 400 might be a feasible strategy to optimize the diagnostic accuracy of CT imaging for diagnosis of obstructive CAD.

Imaging techniques for assessment of coronary flow reserve

The assessment of coronary flow reserve (CFR) may be useful for the functional evaluation of coronary artery disease (CAD). Invasive techniques, such as intracoronary Doppler ultrasound and pressure-derived method, directly assess CFR velocity and fractional flow reserve. Positron emission tomography (PET) has emerged as an accurate noninvasive technique to quantify CFR. Nevertheless, this approach has not been applied to routine studies because of its high cost and complexity. Recently, attempts to estimate CFR with single-photon emission computed tomography (SPECT) tracers have been made in order to obtain, with noninvasive methods, data for quantitative functional assessment of CAD. This review analyzes the relative merit and limitations of CFR measurements by cardiac imaging techniques and describes the potential clinical applications.

Abstract 19355: Assessment of Myocardial Capillary Rarefaction Using Intracoronary Wave Intensity Analysis: A Validation in Cardiac Allograft Patients With Resultant Prognostic Insights

Introduction: A decrease in capillary density (capillary rarefaction) is the predominant mechanism of microcirculatory dysfunction in certain heart conditions. Measuring capillary rarefaction with coronary flow reserve (CFR) or resistance measurements is hampered by the frequent presence of arteriolar remodelling. We investigated the potential of wave intensity analysis (WIA) to ascertain the presence of capillary rarefaction using transplant vasculopathy as a clinical model of microcirculatory disease. The prognostic implications of WIA-assessed capillary density in predicting cardiac allograft vasculopathy (CAV) was then also investigated. Methods: 52 patients with unobstructed coronary arteries underwent combined LAD pressure and flow measurements at rest and with intracoronary adenosine. CFR, hyperaemic microvascular resistance, coronary resistance index, coronary conductance (IHDVPS) and WIA were calculated. Simultaneous right ventricular biopsies were obtained and analysed for capillary density in 17 patients. All patients were then followed up with 1-3 yearly screening angiography and IVUS. Results: All patients were in sinus rhythm with normal LV function. A statistically significant relationship with capillary density was noted with CFR (r=0.52, p=0.048) and the backward decompression wave (BDW) (r=-0.65, p&lt;0.01) the latter of which was maintained with multiple regression analysis (p=0.02). Over a mean follow-up of 9.3 ± 5.2 years, the BDW was able to predict outcome in terms of CAV-events (-7.1 vs -4.5 x10 3 Wm -2 s -1 , p=0.04) as well as the development (7.9 vs 4.8 x10 3 Wm -2 s -1 , p=0.01) and severity (p=0.04) of angiographic CAV. There was a strong trend towards prediction of angiographic CAV disease with IHDVPS (1.7 vs 1.1 cm/s/mmHg, p=0.08) but no other relationships were noted with prognosis and microvascular indices. Conclusions: WIA is an excellent tool for assessing capillary rarefaction and provides a more focused insight into this domain of the microcirculation than other contemporary measures of microcirculatory function. In cardiac transplant patients, it is able to document the early histological changes of CAV and can predict CAV-related outcome as well as its angiographic presence and severity.

Combining Baseline Distal-to-Aortic Pressure Ratio and Fractional Flow Reserve in the Assessment of CoronaryStenosis Severity.

This study sought to understand the physiological basis of baseline distal-to-aortic pressure ratio (Pd/Pa) and fractional flow reserve (FFR) agreement and discordance, using coronary flow reserve (CFR), stenosis resistance, and microcirculatory resistance measurements, and form there, to investigate the potential value of combining Pd/Pa with FFR in the diagnostic rationale. Pd/Pa is always available before FFR assessment, and emerging data supports the notion that baseline indices can determine the ischemic potential of coronary stenosis in selected subsets. A total of 467 stenosed vessels from 363 patients were investigated with pressure and flow sensors during baseline and hyperemia: 168 vessels (135 patients) with thermodilution-derived flow, and 299 vessels (228 patients) with Doppler-derived flow. Pd/Pa correlated more strongly with CFR than FFR (ρ difference= 0.129; p for ρ comparison<0.001). Although Pd/Pa and FFR were closely correlated (ρ= 0.798; 95% confidence interval: 0.767 to 0.828), categorical discordance was observed in 19.3% of total vessels. Such discordance was associated with the patients' clinical profile and was characterized by contrastive changes in stenosis resistance, microcirculatory resistance, and the underlying CFR. Notably, all stenosis with Pd/Pa≤0.83 (n= 74, 15.8%) progressed to FFR≤0.80, and although no Pd/Pa cutoff was able to exclude the development of FFR≤0.80 in the high end of values, only 15 (10.1%) vessels with Pd/Pa≥0.96 (n=149,31.9%) developed FFR≤0.80, from which none had definite ischemia, as defined by CFR≤1.74. Combining baseline Pd/Pa with FFR seems to provide a more comprehensive physiological examination of stenosed coronary arteries and a closer pressure-based appraisal of the flow reserve of the downstream myocardialbed.