Quantitative myocardial perfusion in liver transplantation candidates: Poorly metabolized caffeine inhibition of vasodilatory stress.

Background: Data on cardiac positron emission tomography (PET) in liver transplantation (LT) candidates are limited with no prior study accounting for poorly metabolized caffeine reducing stress perfusion.

Method: Consecutive LT candidates (n = 114) undergoing cardiac rest/stress PET were instructed to abstain from caffeine for 2 days extended to 5 and 7 days. Due to persistently high prevalence of measurable blood caffeine after 5-day caffeine abstinence, dipyridamole (n = 41) initially used was changed to dobutamine (n = 73).

Coronary flow capacity and survival prediction after revascularization: physiological basis and clinical implications.

Background And Aims: Coronary flow capacity (CFC) is associated with an observed 10-year survival probability for individual patients before and after actual revascularization for comparison to virtual hypothetical ideal complete revascularization.

Methods: Stress myocardial perfusion (mL/min/g) and coronary flow reserve (CFR) per pixel were quantified in 6979 coronary artery disease (CAD) subjects using Rb-82 positron emission tomography (PET) for CFC maps of artery-specific size-severity abnormalities expressed as percent left ventricle with prospective follow-up to define survival probability per-decade as fraction of 1.0.

Does financial hardship associate with abnormal quantitative myocardial perfusion and major adverse cardiovascular event?

Background: Data on impact of financial hardship on coronary artery disease (CAD) remain incomplete.

Methods: Consecutive subjects referred for clinical rest/stress cardiac positron emission tomography (PET) were enrolled. Financial hardship is defined as patients' inability to pay for their out-of-pocket expense for cardiac PET.

Subendocardial and Transmural Myocardial Ischemia: Clinical Characteristics, Prevalence, and Outcomes With and Without Revascularization.

Background: Subendocardial ischemia is commonly diagnosed but not quantified by imaging.

Objectives: This study sought to define size and severity of subendocardial and transmural stress perfusion deficits, clinical associations, and outcomes.

Methods: Regional rest-stress perfusion in mL/min/g, coronary flow reserve, coronary flow capacity (CFC), relative stress flow, subendocardial stress-to-rest ratio and stress subendocardial-to-subepicardial ratio as percentage of left ventricle were measured by positron emission tomography (PET) with rubidium Rb 82 and dipyridamole stress in serial 6,331 diagnostic PETs with prospective 10-year follow-up for major adverse cardiac events with and without revascularization.

Use of a Pressure Wire for Automatically Correcting Artifacts in Phasic Pressure Tracings From a Fluid-Filled Catheter.

Background/purpose: Matching phasic pressure tracings between a fluid-filled catheter and high-fidelity pressure wire has received limited attention, although each part contributes half of the information to clinical decisions. We aimed to study the impact of a novel and automated method for improving the phasic calibration of a fluid-filled catheter by accounting for its oscillatory behavior.

Methods/materials: Retrospective analysis of drift check tracings was performed using our algorithm that corrects for mean difference (offset), temporal delays (timing), differential sensitivity of the manifold transducer and pressure wire sensor (gain), and the oscillatory behavior of the fluid-filled catheter described by its resonant frequency and damping factor (how quickly oscillations disappear after a change in pressure).

Prognostic value of microvascular resistance and its association to fractional flow reserve: a DEFINE-FLOW substudy.

Objective: This study aimed to evaluate the prognostic value of hyperemic microvascular resistance (HMR) and its relationship with hyperemic stenosis resistance (HSR) index and fractional flow reserve (FFR) in stable coronary artery disease.

Methods: This is a substudy of the DEFINE-FLOW cohort (NCT02328820), which evaluated the prognosis of lesions (n=456) after combined FFR and coronary flow reserve (CFR) assessment in a prospective, non-blinded, non-randomised, multicentre study in 12 centres in Europe and Japan. Participants (n=430) were evaluated by wire-based measurement of coronary pressure, flow and vascular resistance (ComboWire XT, Phillips Volcano, San Diego, California, USA).

Combined Pressure and Flow Measurements to Guide Treatment of Coronary Stenoses.

Objectives: The aim of this study was to assess clinical outcomes after combined pressure and flow assessment of coronary lesions.

Background: Although fractional flow reserve (FFR) remains the invasive reference standard for revascularization, approximately 40% of stenoses have discordant coronary flow reserve (CFR). Optimal treatment for these disagreements remains unclear.

Design and rationale of the randomized trial of comprehensive lifestyle modification, optimal pharmacological treatment and utilizing PET imaging for quantifying and managing stable coronary artery disease (the CENTURY study).

Background: The literature reports no randomized trial in chronic coronary artery disease (CAD) of a comprehensive management strategy integrating intense lifestyle management, maximal medical treatment to specific goals and high precision quantitative cardiac positron emission tomography (PET) for identifying high mortality risk patients needing essential invasive procedures. We hypothesize that this comprehensive strategy achieves greater risk factor reduction, lower major adverse cardiovascular events and fewer invasive procedures than standard practice.

Methods: The CENTURY Study (NCT00756379) is a randomized-controlled-trial study in patients with stable or at high risk for CAD.

Mortality Prediction by Quantitative PET Perfusion Expressed as Coronary Flow Capacity With and Without Revascularization.

Objectives: This study sought to determine the relationship between the severity of reduced quantitative perfusion parameters and mortality with and without revascularization.

Background: The physiological mechanisms for differential mortality risk of coronary flow reserve (CFR) and coronary flow capacity (CFC) before and after revascularization are unknown.

Methods: Global and regional rest-stress (ml/min/g), CFR, their regional per-pixel combination as CFC, and relative stress in ml/min/g were measured as percent of LV in all serial routine 5,274 diagnostic PET scans with systematic follow-up over 10 years (mean 4.

Coronary Microcirculation in Aortic Stenosis: Pathophysiology, Invasive Assessment, and Future Directions.

With the increasing prevalence of aortic stenosis (AS) due to a growing elderly population, a proper understanding of its physiology is paramount to guide therapy and define severity. A better understanding of the microvasculature in AS could improve clinical care by predicting left ventricular remodeling or anticipate the interplay between epicardial stenosis and myocardial dysfunction. In this review, we combine five decades of literature regarding microvascular, coronary, and aortic valve physiology with emerging insights from newly developed invasive tools for quantifying microcirculatory function.

Coronary Flow Capacity to Identify Stenosis Associated With Coronary Flow Improvement After Revascularization: A Combined Analysis From DEFINE FLOW and IDEAL.

Background Coronary flow capacity (CFC), which is a categorical assessment based on the combination of hyperemic coronary flow and coronary flow reserve (CFR), has been introduced as a comprehensive assessment of the coronary circulation to overcome the limitations of CFR alone. The aim of this study was to quantify coronary flow changes after percutaneous coronary intervention in relation to the classification of CFC and the current physiological cutoff values of fractional flow reserve, instantaneous wave-free ratio, and CFR. Methods and Results Using the combined data set from DEFINE FLOW (Distal Evaluation of Functional Performance With Intravascular Sensors to Assess the Narrowing Effect -Combined Pressure and Doppler FLOW Velocity Measurements) and IDEAL (Iberian-Dutch-English), a total of 133 vessels that underwent intracoronary Doppler flow measurement before and after percutaneous coronary intervention were analyzed.

Phasic pressure measurements for coronary and valvular interventions using fluid-filled catheters: Errors, automated correction, and clinical implications.

Objectives: We sought to develop an automatic method for correcting common errors in phasic pressure tracings for physiology-guided interventions on coronary and valvular stenosis.

Background: Effective coronary and valvular interventions rely on accurate hemodynamic assessment. Phasic (subcycle) indexes remain intrinsic to valvular stenosis and are emerging for coronary stenosis.

Distal Evaluation of Functional performance with Intravascular sensors to assess the Narrowing Effect-combined pressure and Doppler FLOW velocity measurements (DEFINE-FLOW) trial: Rationale and trial design.

Background: It remains uncertain if invasive coronary physiology beyond fractional flow reserve (FFR) can refine lesion selection for revascularization or provide additional prognostic value. Coronary flow reserve (CFR) equals the ratio of hyperemic to baseline flow velocity and has a wealth of invasive and noninvasive data supporting its validity. Because of fundamental physiologic relationships, binary classification of FFR and CFR disagrees in approximately 30%-40% of cases.

Regional, Artery-Specific Thresholds of Quantitative Myocardial Perfusion by PET Associated with Reduced Myocardial Infarction and Death After Revascularization in Stable Coronary Artery Disease.

Because randomized coronary revascularization trials in stable coronary artery disease (CAD) have shown no reduced myocardial infarction (MI) or mortality, the threshold of quantitative myocardial perfusion severity was analyzed for association with reduced death, MI, or stroke after revascularization within 90 d after PET. In a prospective long-term cohort of stable CAD, regional, artery-specific, quantitative myocardial perfusion by PET, coronary revascularization within 90 d after PET, and all-cause death, MI, and stroke (DMS) at 9-y follow-up (mean ± SD, 3.0 ± 2.

Pressure gradient vs. flow relationships to characterize the physiology of a severely stenotic aortic valve before and after transcatheter valve implantation.

Aims: Echocardiography and tomographic imaging have documented dynamic changes in aortic stenosis (AS) geometry and severity during both the cardiac cycle and stress-induced increases in cardiac output. However, corresponding pressure gradient vs. flow relationships have not been described.

What can intracoronary pressure measurements tell us about flow reserve? Pressure-Bounded coronary flow reserve and example application to the randomized DEFER trial.

Objective: We propose a novel technique called pressure-bounded coronary flow reserve (pb-CFR) and demonstrate its application to the randomized DEFER trial.

Background: Intracoronary flow reserve assessment remains underutilized relative to pressure measurements partly due to less robust tools.

Methods: While rest and hyperemic intracoronary pressure measurements cannot quantify CFR exactly, they do provide upper and lower bounds.

Optimal Adenosine Stress for Maximum Stress Perfusion, Coronary Flow Reserve, and Pixel Distribution of Coronary Flow Capacity by Kolmogorov-Smirnov Analysis.

Background: Different adenosine stress imaging protocols have not been systemically validated for absolute myocardial perfusion and coronary flow reserve (CFR) by positron emission tomography, where submaximal stress precludes assessing physiological severity of coronary artery disease.

Methods And Results: In 127 volunteers, serial rest-stress positron emission tomography scans using rubidium-82 with various adenosine infusion protocols identified (1) the protocol with maximum stress perfusion and CFR, (2) test-retest precision in same subject, (3) stress perfusion and CFR after adenosine compared with dipyridamole, (4) heterogeneity of coronary flow capacity combining stress perfusion and CFR, and (5) potential relevance for patients with risk factors or coronary artery disease. The adenosine 6-minute infusion with rubidium-82 injection at 3 minutes caused CFR that was significantly 15.

Routine Clinical Quantitative Rest Stress Myocardial Perfusion for Managing Coronary Artery Disease: Clinical Relevance of Test-Retest Variability.

Objectives: Positron emission tomography (PET) quantifies stress myocardial perfusion (in cc/min/g) and coronary flow reserve to guide noninvasively the management of coronary artery disease. This study determined their test-retest precision within minutes and daily biological variability essential for bounding clinical decision-making or risk stratification based on low flow ischemic thresholds or follow-up changes.

Background: Randomized trials of fractional flow reserve-guided percutaneous coronary interventions established an objective, quantitative, outcomes-driven standard of physiological stenosis severity.