[Show abstract][Hide abstract] ABSTRACT: Background:
The objective of this study was to measure myocardial blood flow (MBF) in humans using (99m)Tc-tetrofosmin and dynamic single-photon emission computed tomography (SPECT).
Dynamic SPECT using (99m)Tc-tetrofosmin and dynamic positron emission tomography (PET) was performed on a group of 16 patients. The SPECT data were reconstructed using a 4D-spatiotemporal iterative reconstruction method. The data corresponding to 9 patients were used to determine the flow-extraction curve for (99m)Tc-tefrofosmin while data from the remaining 7 patients were used for method validation. The nonlinear tracer correction parameters A and B for (99m)Tc-tefrofosmin were estimated for the 9 patients by fitting the flow-extraction curve [Formula: see text] for K 1 values estimated with (99m)Tc-tefrofosmin using SPECT and MBF values estimated with (13)N-NH3 using PET. These parameters were then used to calculate MBF and coronary flow reserve (CFR) in three coronary territories (LAD, RCA, and LCX) using SPECT for an independent cohort of 7 patients. The results were then compared with that estimated with (13)N-NH3 PET. The flow-dependent permeability surface-area product (PS) for (99m)Tc-tefrofosmin was also estimated.
The estimated flow-extraction parameters for (99m)Tc-tefrofosmin were found to be A = 0.91 ± 0.11, B = 0.34 ± 0.20 (R (2) = 0.49). The range of MBF in LAD, RCA, and LCX was 0.44-3.81 mL/min/g. The MBF between PET and SPECT in the group of independent cohort of 7 patients showed statistically significant correlation, r = 0.71 (P < .001). However, the corresponding CFR correlation was moderate r = 0.39 yet statistically significant (P = .037). The PS for (99m)Tc-tefrofosmin was (0.019 ± 0.10)*MBF + (0.32 ± 0.16).
Dynamic cardiac SPECT using (99m)Tc-tetrofosmin and a clinical two-headed SPECT/CT scanner can be a useful tool for estimation of MBF.
No preview · Article · Dec 2015 · Journal of Nuclear Cardiology
[Show abstract][Hide abstract] ABSTRACT: Background:
We previously reported the generation of a reporter line of human embryonic stem cells (hESCs) with enhanced green fluorescent protein (eGFP) expression driven by the α-myosin heavy chain (αMHC) promoter. The GFP+/αMHC+ cells derived from this cell line behave as multipotent, human myocardial precursors (hMPs) in vitro. In this study, we evaluated the therapeutic effects of GFP+/αMHC+ cells isolated from the reporter line in a mouse model of myocardial infarction (MI).
MI was generated in immunodeficient mice. hMPs were injected into murine infarcted hearts under ultrasound guidance at 3 days post-MI. Human fetal skin fibroblasts (hFFs) were injected as control. Cardiac function was evaluated by echocardiography. Infarct size, angiogenesis, apoptosis, cell fate, and teratoma formation were analyzed by immunohistochemical staining.
Compared with control, hMPs resulted in improvement of cardiac function post-MI with smaller infarct size, induced endogenous angiogenesis, and reduced apoptosis of host cardiomyocytes at the peri-infarct zone at 28 days post-MI.
Intramyocardial injection of hMPs improved cardiac function post-MI. The engraftment rate of these cells in the myocardium post-MI was low, suggesting that the majority of effect occurs via paracrine mechanisms.
[Show abstract][Hide abstract] ABSTRACT: Injection of various stem cells has been tested with the hopes of improving cardiac function after a myocardial infarction (MI). However, there is continued controversy as to which cell type is best for repair. Due to technical differences in cell isolation, processing, delivery, and cardiac functional assessment by various investigators, it has been difficult to directly compare the results of different cells. Using same techniques to evaluate the efficacy of different cell types, we have separately delivered bone marrow cells (BMCs), cardiospheres (CSs), CS-derived Sca-1(+)/CD45(-) cells, human embryonic stem cell-derived cardiomyocytes, and BMC extract into infarcted murine myocardium and found that all of these treatments reduce infarct size and improve cardiac function post-MI similarly without one regimen being superior to another. The beneficial effects appear to be via paracrine influences. Different progenitors lead to improved cardiac function post-MI, but it is premature to hype any specific cell type at this time.
No preview · Article · May 2015 · Heart Failure Reviews
[Show abstract][Hide abstract] ABSTRACT: We have generated a bioinspired tunable system of hyaluronic acid (HyA)-based hydrogels for Matrix-Assisted Cell Transplantation (MACT). With this material, we have independently evaluated matrix parameters such as adhesion peptide density, mechanical properties, and growth factor sequestering capacity, to engineer an environment that imbues donor cells with a milieu that promotes survival and engraftment with host tissues after transplantation. Using a versatile population of Sca-1+/CD45− cardiac progenitor cells (CPCs), we demonstrated that the addition of heparin in the HyA hydrogels was necessary to coordinate the presentation of TGFβ1 and to support the trophic functions of the CPCs via endothelial cell differentiation and vascular like tubular network formation. Presentation of exogenous TGFβ1 by binding with heparin improved differentiated CPC function by sequestering additional endogenously-produced angiogenic factors. Finally, we demonstrated that TGFβ1 and heparin-containing HyA hydrogels can promote CPC survival when implanted subcutaneously into murine hind-limbs and encouraged their participation in the ensuing neovascular response, which included blood vessels that had anastomosed with the host's blood vessels.
[Show abstract][Hide abstract] ABSTRACT: Heart failure is increasing at an alarming rate, making it a worldwide epidemic. As the population ages and life expectancy increases, this trend is not likely to change. Myocardial infarction (MI)-induced adverse left ventricular (LV) remodeling is responsible for nearly 70% of heart failure cases. The adverse remodeling process involves an extension of the border zone (BZ) adjacent to an MI, which is normally perfused but shows myofiber contractile dysfunction. To improve patient-specific modeling of cardiac mechanics, we sought to create a finite element model of the human LV with BZ and MI morphologies integrated directly from delayed enhancement magnetic resonance (DE-MR) images. Instead of separating the LV into discrete regions (e.g. the MI, BZ and remote regions) with each having a homogeneous myocardial material property, we assumed a functional relation between the DE-MR image pixel intensity and myocardial contractility. The finite element model was then comprehensively validated using measurements obtained from the same patient, namely, 3D strain measurements, using complementary spatial modulation of magnetization magnetic resonance (CSPAMM-MR) images. We demonstrate the utility of our method for quantifying smooth regional variations in myocardial contractility using cardiac DE-MR and CSPAMM-MR images acquired from a 78-year-old woman who experienced an MI approximately one year prior. We found a remote myocardial diastolic stiffness of 0.102 kPa, and a remote myocardial contractility of 146.9 kPa, which are both in the range of previously published normal human values. Moreover, we found a BZ extending over 30% of the normalized pixel intensity maps from the DE-MR images, which is consistent with the literature. Based on these regional myocardial material properties, we used our finite element model to compute unmeasurable patient-specific diastolic and systolic LV myofiber stress distributions. One of the main driving forces for adverse LV remodeling is assumed to be an abnormally high level of ventricular wall stress, and many existing and new treatments for heart failure fundamentally attempt to normalize LV wall stress. Thus, our non-invasive method for estimating smooth regional variations in myocardial contractility should be valuable for optimizing new surgical or medical strategies to limit the chronic evolution from infarction to heart failure.
Full-text · Article · Nov 2014 · Journal of Biomechanical Engineering
[Show abstract][Hide abstract] ABSTRACT: Cardiac catheterization has been increasingly utilized to evaluate coronary artery disease in patients with end stage liver disease (ESLD). It is known in other populations that radial access reduces access site complications;however, there is a paucity of data in ESLD patients. We investigated vascular and bleeding complications rates between trans-femoral and trans-radial cardiac catheterizations in this high risk population. In this retrospective cohort study, three hundred and thirty four ESLD patients were identified between August 2004 and December 2012 who had undergone trans-femoral (femoral group) or trans-radial (radial group) cardiac catheterizations at our institution. The radial group was not significantly different from the femoral group in age (p = 0.056), proportions of genders (p = 0.85), and weight (p = 0.19); however, compared to the femoral group, the radial group had significantly lower blood pressure (p < 0.0001), hemoglobin (10.4 ± 1.9 vs 11.1 ± 2.02 g/dL, p = 0.001), and hematocrit (30.3 ± 5.7% vs 32.6 ± 6.0%, p < 0.0006), and had a significantly higher INR (1.94 ± 1.16 vs 1.59 ± 0.62, p = 0.0001). In terms of vascular complications, the radial group had a significantly lower rate of pseudoaneurysms (0% vs 3.7%, p = 0.019) than the femoral group. While there were no bleeding complications in either group or differences in transfusion requirements, there was a significantly lower percentage drop in hematocrit in the radial group compared to the femoral group (5.4% vs 7.8%, p = 0.039). In conclusion, trans-radial catheterization is associated with lower rates of vascular access site complications compared to trans-femoral catheterization.
No preview · Article · Oct 2014 · American Journal of Cardiovascular Disease
[Show abstract][Hide abstract] ABSTRACT: Recent advances in technology have led to an increase in the use of bilateral femoral artery access and the requirement for large-bore access. Optimal access is in the common femoral artery (CFA), rather than higher (in the external iliac artery) or lower (in one of the branches of the CFA). However, there is a paucity of data in the literature about the relationship between bifurcation level of one CFA and the contralateral CFA. To define the prevalence of high bifurcation of the CFA and the relationship between bifurcation level on both sides, we performed a retrospective analysis of all patients with bilateral femoral angiography. From 4880 femoral angiograms performed at UCSF cardiac catheterization laboratory between 2005-2013, a total of 273 patients had bilateral femoral angiograms. The prevalence of low/normal, high, and very-high femoral bifurcations was 70%, 26%, and 4%, respectively, with no difference between sides. A high or very-high bifurcation significantly increased the likelihood of a high bifurcation on the contralateral side (odds ratio >3.0). Multivariable logistic regression analysis revealed age, gender, self-reported race, height, weight, and body mass index were not predictive of high or very-high bifurcations on either side. In conclusion, high femoral artery bifurcations are common and increase the likelihood of a high bifurcation of the contralateral femoral artery.
No preview · Article · Sep 2014 · The Journal of invasive cardiology
[Show abstract][Hide abstract] ABSTRACT: Coronary artery aneurysm (CAA) is an uncommon clinical finding, with an incidence varying from 1.5%-4.9% in adults, and is usually considered a variant of coronary artery disease (CAD). CAA identified in the context of acute coronary syndrome (ACS) represents a unique management challenge, particularly if the morphology of the CAA is suspected to have provoked the acute clinical syndrome. CAA is associated with thrombus formation due to abnormal laminar flow, as well as abnormal platelet and endothelial-derived pathophysiologic factors within the CAA. Once formed, mural thrombus may potentiate the deposition of additional thrombus within aneurysmal segments. Percutaneous revascularization of CAA has been associated with complications including distal embolization of thrombus, no-reflow phenomenon, stent malapposition, dissection, and rupture. Presently, there are no formal guidelines to direct the management of CAA in patients presenting with ACS; controversies exist whether conservative, surgical, or catheter-based management should be pursued. In this manuscript, we present an extensive review of the existing literature and associated clinical guidelines, and propose a management algorithm for patients with this complex clinical scenario. Armed with this perspective, therapeutic decisions may be tailored to synthesize patient factors and preferences, individualized clinical assessment, and existing American Heart Association/American College of Cardiology guidelines for management of ACS.
No preview · Article · Jun 2014 · The Journal of invasive cardiology
[Show abstract][Hide abstract] ABSTRACT: : Cardiovascular disease is the leading cause of death in Western countries. A major limitation of current treatments is the inability to efficiently repair or replace dead myocardium. Recently, stem cell-based therapies have been explored as an avenue to circumvent current therapeutic limitations. Overall, these therapies seem to result in small improvements in the contractile function of the heart. The exact mechanism(s) of action that underlie these improvements remain unknown, and it is believed that paracrine effects play a significant role. Previously, we had reported that an extract derived from bone marrow cells, in the absence of any live cell, contained cardioprotective soluble factors. In this study, we identify IL-15 as a putative cardioprotectant within the bone marrow cells paracrine profile. Using an in vitro culture system, we assessed the ability of IL-15 to protect cardiomyocytes under hypoxic conditions. For the first time, we have identified IL-15 receptors on the surface of cardiomyocytes and delineated the signaling system by which hypoxic cardiomyocytes may be protected from cellular death and rescued from oxidative stress with IL-15 treatment.
No preview · Article · May 2014 · Journal of cardiovascular pharmacology
[Show abstract][Hide abstract] ABSTRACT: Aging is associated with higher incidence of heart failure and death following myocardial infarction (MI). The molecular and cellular changes that lead to these worse outcomes are not known.
Young and aging mice underwent induction of MI by LAD ligation. There was a significant increase in mortality in the aging mice. Neither the young nor aging hearts after MI had inducible ventricular tachycardia. Cardiomyocyte apoptosis increases early after MI in young and aging mice, but to a much greater degree in the aging mice. Caspase inhibition with Ac-DEVD-CHO resulted in a 61% reduction in activated caspase-3 and an 84% reduction in apoptosis in cardiomyocytes in young mice (P < 0.05), but not in aging mice. Gene pathway profiling demonstrated activation of both the caspase and Map3k1/Mapk10 pathways in aging mice following MI, which may contribute to their resistance to caspase inhibition.
Aging hearts activate distinct apoptotic pathways have more cardiomyocyte apoptosis and are resistant to antiapoptotic therapies following MI. Novel or combination approaches may be required to improve outcomes in aging patients following MI.
No preview · Article · Dec 2013 · Cardiovascular Therapeutics
[Show abstract][Hide abstract] ABSTRACT: Current evidence suggests that regenerative v. degenerative endothelial responses can be integrated in a clinical endothelial phenotype, reflecting the net result between damage from risk factors and endogenous repair capacity. We have previously shown that a cocoa flavanol (CF) intervention can improve endothelial function and increase the regenerative capacity of the endothelium by mobilising circulating angiogenic cells in patients with coronary artery disease (CAD). The aim of the present study was to investigate whether CF can lower the levels of circulating endothelial microparticles (EMP), markers of endothelial integrity, along with improvements in endothelial function. The levels of EMP in the frozen plasma samples of CAD patients were measured along with endothelial function (flow-mediated vasodilation, FMD); n 16, FMD data published previously), and these data were compared with those of young (n 12) and age-matched (n 12) healthy control subjects. The CAD patients exhibited significantly increased levels of EMP along with impaired FMD when compared with the healthy control subjects. The levels of CD144+ and CD31+/41- EMP were inversely correlated with FMD (r - 0·67, P= 0·01 and r - 0·59, P= 0·01, respectively). In these CAD patients, the levels of EMP were measured after they had consumed a drink containing 375 mg of CF (high-CF intervention, HiFI) or 9 mg of CF (macro- and micronutrient-matched low-CF control, LoFl) twice daily over a 30-d period in a randomised, double-blind, cross-over study. After 1 month of HiFI, the levels of CD31+/41- and CD144+ EMP decreased ( - 25 and - 23 %, respectively), but not after LoFl. Our data show that flavanols lower the levels of EMP along with higher endothelial function, lending evidence to the novel concept that flavanols may improve endothelial integrity.
Full-text · Article · Nov 2013 · The British journal of nutrition
[Show abstract][Hide abstract] ABSTRACT: Transradial access (TRA) offers advantages including decreased vascular complications, reduced length of hospital stay, and reduced cost. The size of the radial artery (RA) limits the equipment that can be used via TRA. Intra-arterial (IA) vasodilators prevent and treat RA spasm, yet are not uniformly used in TRA and their effect on the absolute size of the RA remains unknown.
121 patients undergoing TRA for cardiac catheterization were included. 78 patients underwent RA angiography prior to administration of IA vasodilators ('no vasodilator' group), 43 patients underwent radial angiography after administration of an IA verapamil and nitroglycerin cocktail ('vasodilator' group). Quantitative angiography was used to compare the RA diameters.
Clinical characteristics were similar between the groups, except that patients in the 'no vasodilator' cohort were taller (1.67±0.1m vs. 1.73±0.1m, p=0.002), and heavier (84.9±18.2kg vs. 75±17.1kg, p=0.003). In the 'vasodilator' group the proximal RA diameter was larger (2.29±0.47mm vs. 2.09±0.41mm, p=0.02) as was the narrowest segment (1.83±0.56mm vs 1.39±0.43, p<0.0001) compared to the 'no vasodilator' group. At the RA origin, 79.4% of those in the 'vasodilator' group were larger than a 6Fr guide catheter, compared to 51.4% in the 'no vasodilator' group (p=0.004). At the narrowest segment a higher percentage of RAs in the 'vasodilator' group were larger than a 5Fr guide catheter (65.1% vs 26.9%, p<0.001) and a 6Fr catheter (34.9% vs 10.3%, p=0.001).
IA vasodilators increase pre-procedural RA diameter in patients undergoing cardiac catheterization via TRA. This increase in diameter has important implications for procedural planning.
Boyer et al. performed a blinded controlled clinical trial investigating the effects of intra-arterial vasodilators on radial artery size and spasm during cardiac catheterization. The study demonstrates that intra-arterial vasodilators significantly increased the radial artery size throughout the entire course of the vessel and significantly decreased the amount of radial artery spasm. The authors conclude that these findings support the use of intra-arterial vasodilators during cardiac catheterization and have important implications for emerging technologies such as larger bore sheathless radial procedures.
No preview · Article · Oct 2013 · Cardiovascular revascularization medicine: including molecular interventions
[Show abstract][Hide abstract] ABSTRACT: Introduction:
Cardiospheres (CS) are self-assembling clusters of cells that can be grown from cardiac tissue. They contain a heterogeneous cell population that includes cardiac progenitor cells (CPCs) and cardiac fibroblasts. CS and CPCs have been shown to improve cardiac function after myocardial infarction (MI) in experimental models and are now being studied in clinical trials. The effects of aging on the proliferative capacity of CS and CPCs, and the paracrine signaling between cell types, remain incompletely understood.
Methods and results:
We compared the growth of CS from young and aging murine hearts at baseline and following MI. The number of CS from young and aging hearts was similar at baseline. However, after MI, young hearts had a dramatic increase in the number of CS that grew, but this proliferative response to MI was virtually abolished in the aging heart. Further, the proportion of cells within the CS that were CPCs (defined as Sca-1(stem cell antigen-1)(+)/CD45(-)) was significantly lower in aging hearts than young hearts. Thus the number of available CPCs after culture from aging hearts was substantially lower than from young hearts. Cardiac fibroblasts from aging hearts proliferated more slowly in culture than those from young hearts. We then investigated the interaction between aging cardiac fibroblasts and CPCs. We found no significant paracrine effects on proliferation between these cell types, suggesting the impaired proliferation is a cell-autonomous problem.
Aging hearts generate fewer CPCs, and aging CPCs have significantly reduced proliferative potential following MI. Aging cardiac fibroblasts also have reduced proliferative capacity, but these appear to be cell-autonomous problems, not caused by paracrine signaling between cell types.
No preview · Article · Sep 2013 · Journal of Clinical Medicine
[Show abstract][Hide abstract] ABSTRACT: Various stem cell types have been tested for regenerating damaged myocardium after myocardial infarction. However, the results of clinical trials have not been consistent, with only some of the trials reporting small improvements in cardiac function. It appears that engraftment and survival of injected cells is limited, and transplanted stem cells either do not differentiate into cardiac cells or differentiate into only limited number of cardiac cells. The exact mechanism(s) of cardiac functional improvement by cell therapy are unclear, but paracrine effect may play a central role. The resident cardiac progenitor cells identified within the adult myocardium have distinct advantages over other stem cell types for cardiac cell therapy, as they are likely pre-committed to the cardiovascular fate. However, isolating and expanding these cells from cardiac biopsies is a challenge. More recently, direct reprogramming of fibroblasts into cardiomyocytes has given new hope for myocardial regeneration. Here we will review different stem cells used in cardiac cell therapy with a focus on the native cardiac progenitor cells and briefly outline future directions of cardiac cell therapy.
No preview · Article · May 2013 · Journal of cardiovascular pharmacology