Bulk Flow and Near Wall Hemodynamics of the Rabbit Aortic Arch and Descending Thoracic Aorta: A 4D PC-MRI Derived Computational Fluid Dynamics Study.

Animal models offer a flexible experimental environment for studying atherosclerosis. The mouse is the most commonly used animal, however, the underlying hemodynamics in larger animals such as the rabbit are far closer to that of humans. The aortic arch is a vessel with complex helical flow and highly heterogeneous shear stress patterns which may influence where atherosclerotic lesions form. A better understanding of intraspecies flow variation and the impact of geometry on flow may improve our understanding of where disease forms. In this work, we use magnetic resonance angiography (MRA) and 4D phase contrast magnetic resonance imaging (PC-MRI) to image and measure blood velocity in the rabbit aortic arch. Measured flow rates from the PC-MRI were used as boundary conditions in computational fluid dynamics (CFD) models of the arches. Helical flow, cross flow index (CFI), and time-averaged wall shear stress (TAWSS) were determined from the simulated flow field. Both traditional geometric metrics and shape modes derived from statistical shape analysis were analyzed with respect to flow helicity. High CFI and low TAWSS were found to colocalize in the ascending aorta and to a lesser extent on the inner curvature of the aortic arch. The Reynolds number was linearly associated with an increase in helical flow intensity (R = 0.85, p < 0.05). Both traditional and statistical shape analyses correlated with increased helical flow symmetry. However, a stronger correlation was obtained from the statistical shape analysis demonstrating its potential for discerning the role of shape in hemodynamic studies.

Acute coronary syndrome as a first presentation of systemic lupus erythematosus in a teenager: revascularization by hybrid coronary artery bypass graft surgery and percutaneous coronary intervention: case report.

Patients with systemic lupus erythematosus (SLE) may present with acute coronary syndrome (ACS) due to coronary vasculitis or premature atherosclerosis. There is a paucity of data on invasive management strategies for young adults who present with an ACS secondary to active vasculitis. This article describes the case of a teenager who presented with an ACS secondary to lupus vasculitis as his first presentation of active SLE. Coronary angiography showed a left main equivalent lesion involving a proximal very large left anterior descending artery (LAD) and diagonal stenosis (with a diminutive left circumflex artery). The boy underwent a successful endoscopic coronary bypass surgery to his LAD followed by percutaneous coronary intervention to his diagonal artery. This case demonstrates the feasibility and safety of a hybrid coronary revascularization in a teenager with acute coronary syndrome due to coronary vasculitis.

Left ventricular inotropic reserve and right ventricular function predict increase of left ventricular ejection fraction after beta-blocker therapy in nonischemic cardiomyopathy.

OBJECTIVES: The purpose of this study was to determine whether higher left ventricular inotropic reserve, defined as the increase in left ventricular ejection fraction (LVEF) in response to intravenous dobutamine infusion, or other ventriculographic variables predict the increase in LVEF after beta-blocker therapy in patients with nonischemic cardiomyopathy (NICM). BACKGROUND: Long-term beta-blocker therapy increases LVEF in some patients with NICM. Other than dose, there are no definite predictors of LVEF increase. METHODS: Thirty patients with LVEF < or = 0.35 and NICM underwent assessment of LVEF at rest and after a 10-min intravenous infusion of dobutamine at 10 microg/kg/min, using equilibrium radionuclide ventriculography. Age was 49 +/- 11 years, 33% women, functional class 2.6 +/- 0.5, duration of chronic heart failure 3.2 +/- 2.9 years, LVEF 0.21 +/- 0.07, left ventricular end-diastolic volume index 180 +/- 64 ml/m2. Right ventricular ejection fraction (RVEF) was abnormal in 37%. Mean dobutamine-induced augmentation of LVEF (DoALVEF) was 0.12 +/- 0.08. Patients were started on one of three beta-blockers (carvedilol, bucindolol or metoprolol) and the dose was advanced to the maximum tolerated. RESULTS: Left ventricular ejection fraction, reassessed 7.4 +/- 5.9 months after maximum beta-blocker dose was reached, increased to 0.34 +/- 0.13 (p = 0.0006). The following baseline variables correlated with improvement of LVEF: DoALVEF (p = 0.001), RVEF (p = 0.005), systolic blood pressure at end of dobutamine infusion (p = 0.02) and dose of beta-blocker (p = 0.07). In a multivariate analysis, only DoALVEF (p = 0.0003) and RVEF (p = 0.002) were predictive of the increase in LVEF. CONCLUSIONS: Patients with nonischemic cardiomyopathy who have higher left ventricular inotropic reserve and normal RVEF derive higher increase in LVEF from beta-blocker therapy.

Fractional flow reserve compared with intravascular ultrasound guidance for optimizing stent deployment.

BACKGROUND: Determination of fractional flow reserve (FFR) has been proposed as a means to assess stent deployment. In this prospective, multicenter trial, we evaluate the use of FFR to optimize stenting by comparing it with standard intravascular ultrasound (IVUS) criteria. METHODS AND RESULTS: Eighty-four stable patients with isolated coronary lesions underwent coronary stent deployment starting at 10 atm and increased serially by 2 atm until the FFR was >/=0.94 or 16 atm was achieved. IVUS was then performed. FFR was measured with a coronary pressure wire with intracoronary adenosine to induce hyperemia. The diagnostic characteristics of an FFR <0.94 to predict suboptimal stent expansion by IVUS, defined in both absolute and relative terms, were calculated. Over a range of IVUS criteria, the highest sensitivity, specificity, and predictive accuracy of FFR were 80%, 30%, and 42%, respectively. Receiver operator characteristic analysis defined an optimal FFR cut point at >/=0.96; at this threshold, the sensitivity, specificity, and predictive accuracy of FFR were 75%, 58%, and 62%, respectively (P=0.03 for comparison of predictive accuracy, P=0.01 for concordance between FFR and IVUS). The negative predictive value was 88%. Significantly better diagnostic performance was achieved in a subgroup that received higher doses (>30 microgram) of intracoronary adenosine during pressure measurements, suggesting that FFR might be overestimated in the other group. CONCLUSIONS: A fractional flow reserve <0.96, measured after stent deployment, predicts a suboptimal result based on validated intravascular ultrasound criteria; however, an FFR >/=0.96 does not reliably predict an optimal stent result. Higher doses of intracoronary adenosine than previously used to measure FFR improve these results.

Relationship between extent of residual myocardial viability and coronary flow reserve in patients with recent myocardial infarction.

BACKGROUND: The presence of viability in an infarct zone implies an intact microvasculature. We hypothesized that coronary flow reserve (CFR), which assesses the microcirculation, would correlate with the extent of viability in infarction zones. METHODS: CFR was measured after stenting in 17 patients with single vessel disease >48 hours from infarction. Viability was determined with use of single-photon emission computed tomography sestamibi imaging. RESULTS: Sestamibi uptake in the infarct zone correlated with CFR in the infarct artery (r = 0.62, P =.008) and sestamibi uptake in the infarct zone was greater in patients with normal CFR than in patients with abnormal CFR (61.9 +/- 9.1% vs 46.3 +/- 9.6%, P =.004). In addition, CFR was greater in patients with viability compared with patients without viability (2.4 +/- 1.3 vs 1.4 +/- 0.4, P =.015). CONCLUSIONS: CFR correlates with the extent of viability after infarction. Preserved CFR in an infarct-related artery implies preserved viability.

Failure to improve left ventricular function after coronary revascularization for ischemic cardiomyopathy is not associated with worse outcome.

Background-Preoperative identification of viable myocardium in patients with ischemic cardiomyopathy is considered important because CABG can result in recovery of left ventricular (LV) function. However, the hypothesis that lack of improvement of LV function after CABG is associated with poorer patient outcome is untested. Methods and Results-Outcome was compared in patients with ischemic LV dysfunction (LVEF 0.05 increase in LVEF (group A) and 36 (35%) had no significant change, or

Localized intramural drug delivery during balloon angioplasty using hydrogel-coated balloons and pressure-augmented diffusion.

OBJECTIVES: This study was designed to assess the feasibility of using hydrogel-coated balloons to deliver biologically active agents to the blood vessel wall. BACKGROUND: The local intramural delivery of therapeutic agents during balloon angioplasty has been proposed as an adjunctive technique for preventing early intracoronary thrombosis and late restenosis. METHODS: To assess the efficacy of delivery and depth of penetration in vitro, local delivery of horseradish peroxidase was performed in 40 porcine peripheral arteries, and delivery of fluoresceinated heparin was performed in 20 porcine peripheral arteries and 7 human atheromatous arteries. To determine the persistence of these agents in the vessel wall in vivo, horseradish peroxidase was delivered to 18 porcine peripheral arteries that were harvested at intervals of 45 min to 48 h. Fluoresceinated heparin was delivered to 22 porcine peripheral arteries, 14 with the use of a protective sleeve, harvested at intervals of 30 s to 24 h. RESULTS: In vitro agent delivery was successful in all specimens. The depth of penetration of horseradish peroxidase was directly related to both balloon pressure (p < 0.04) and duration of inflation (p < 0.01). In vivo peroxidase staining was evident at 45 and 90 min but not thereafter. With the use of a protective sleeve, heparin was present in all arteries harvested at 30 s, with marked dissipation at 1 and 24 h. Without a sleeve, no fluorescein staining was detected in any artery. With both agents, delivery occurred consistently over broad regions of the vessel wall that were free of architectural disruption. CONCLUSIONS: Hydrogel-coated balloons can deliver biologically active agents to the vessel wall without gross tissue disruption and may provide an atraumatic method for the local delivery of therapeutic agents during balloon angioplasty.