Understanding heterogeneous mechanisms of heart failure with preserved ejection fraction through cardiorenal mathematical modeling

In contrast to heart failure (HF) with reduced ejection fraction (HFrEF), effective interventions for HF with preserved ejection fraction (HFpEF) have proven elusive, in part because it is a heterogeneous syndrome with incompletely understood pathophysiology. This study utilized mathematical modeling to evaluate mechanisms distinguishing HFpEF and HFrEF. HF was defined as a state of chronically elevated left ventricle end diastolic pressure (LVEDP > 20mmHg). First, using a previously developed cardiorenal model, sensitivities of LVEDP to potential contributing mechanisms of HFpEF, including increased myocardial, arterial, or venous stiffness, slowed ventricular relaxation, reduced LV contractility, hypertension, or reduced venous capacitance, were evaluated. Elevated LV stiffness was identified as the most sensitive factor. Large LV stiffness increases alone, or milder increases combined with either decreased LV contractility, increased arterial stiffness, or hypertension, could increase LVEDP into the HF range without reducing EF. We then evaluated effects of these mechanisms on mechanical signals of cardiac outward remodeling, and tested the ability to maintain stable EF (as opposed to progressive EF decline) under two remodeling assumptions: LV passive stress-driven vs. strain-driven remodeling. While elevated LV stiffness increased LVEDP and LV wall stress, it mitigated wall strain rise for a given LVEDP. This suggests that if LV strain drives outward remodeling, a stiffer myocardium will experience less strain and less outward dilatation when additional factors such as impaired contractility, hypertension, or arterial stiffening exacerbate LVEDP, allowing EF to remain normal even at high filling pressures. Thus, HFpEF heterogeneity may result from a range of different pathologic mechanisms occurring in an already stiffened myocardium. Together, these simulations further support LV stiffening as a critical mechanism contributing to elevated cardiac filling pressures; support LV passive strain as the outward dilatation signal; offer an explanation for HFpEF heterogeneity; and provide a mechanistic explanation distinguishing between HFpEF and HFrEF.

A 3-year analysis of the impact of COVID-19 pandemic on NSTEMI incidence, clinical characteristics, management, and outcomes

OBJECTIVE

The COVID-19 pandemic has been associated with decreased incidence of acute coronary syndrome with worsened outcomes. Few studies have addressed the effects beyond the initial phases of the pandemic. This study elucidated the incidence, clinical characteristics, management, and outcomes of NSTEMI at a tertiary referral center from sample time periods of 2019-2022.

METHODS

This study included consecutive NSTEMI patients from March 14-May 9, 2019-2022. Variables included baseline characteristics, clinical features on arrival, management strategy, time parameters, and adverse outcomes. The primary outcome was defined as death, heart failure requiring diuretics, and/or sustained ventricular arrhythmia.

RESULTS

This study comprised 250 patients of whom 181 who were admitted during the COVID-19 outbreak. Baseline characteristics were similar among groups. There was a reduction in door-to-angiography time from 29 h in 2019 to 19 h in 2020 [p = 0.01] and 20 h in 2021 [p = 0.02]. PCI intervention increased from 31.8% in 2019% to 50.0% in 2020 [p = 0.05] and 54.7% in 2021 [p < 0.01]. Median length-of-stay (LOS) was reduced from 3 days in 2019 to 2 days in 2020 [p = 0.03]. There was no significant change in outcomes in COVID-19 cohorts compared to control year.

CONCLUSIONS

NSTEMI patients during the first 2 years of the COVID-19 pandemic were associated with reduced door-to-angiography times and increased percutaneous coronary intervention (PCI), and patients in year one were associated with reduced LOS. This study suggests that NSTEMI may be managed more efficiently thus reducing hospital bed utilization and potential costs.

Reducing costs and improving care after hospitalization: Economic evaluation of a novel transitional care clinic

Transitional care management (TCM) is a novel strategy for reducing costs and improving clinical outcomes after hospitalization but remains under-utilized. An economic analysis was performed on a hospital-based transition of care clinic (TCC) open to all patients regardless of payor status. TCC reduced re-hospitalization and emergency department (ED) utilization at six-month follow up. A cost-consequence analysis based on real world data found the TCC intervention to be cost effective relative to usual care. Hospital managers should consider adoption of TCC to improve patient care and reduce costs.

Fundamentals of integrated ferrohydrodynamic cell separation in circulating tumor cell isolation

Methods to separate circulating tumor cells (CTCs) from blood samples were intensively researched in order to understand the metastatic process and develop corresponding clinical assays. However current methods faced challenges that stemmed from CTCs' heterogeneity in their biological markers and physical morphologies. To this end, we developed integrated ferrohydrodynamic cell separation (iFCS), a scheme that separated CTCs independent of their surface antigen expression and physical characteristics. iFCS integrated both diamagnetophoresis of CTCs and magnetophoresis of blood cells together via a magnetic liquid medium, ferrofluid, whose magnetization could be tuned by adjusting its magnetic volume concentration. In this paper, we presented the fundamental theory of iFCS and its specific application in CTC separation. Governing equations of iFCS were developed to guide its optimization process. Three critical parameters that affected iFCS's cell separation performance were determined and validated theoretically and experimentally. These parameters included the sample flow rate, the volumetric concentration of magnetic materials in the ferrofluid, and the gradient of the magnetic flux density. We determined these optimized parameters in an iFCS device that led to a high recovery CTC separation in both spiked and clinical samples.

Tumor antigen-independent and cell size variation-inclusive enrichment of viable circulating tumor cells

Isolation of circulating tumor cells (CTCs) from blood provides a minimally-invasive alternative for basic understanding, diagnosis, and prognosis of metastatic cancer. The roles and clinical values of CTCs are under intensive investigation, yet most studies are limited by technical challenges in the comprehensive enrichment of intact and viable CTCs with minimal white blood cell (WBC) contamination. Here, we report a novel method based on contrast of cell magnetization in biocompatible ferrofluids (a colloidal magnetic nanoparticle suspension), termed as integrated ferrohydrodynamic cell separation (iFCS), that enriches CTCs in a tumor antigen-independent and cell size variation-inclusive manner, achieves a high throughput (12 mL h-1), high recovery rate (99.08% at down to ∼10 cells per mL spike ratio), and low WBC contamination (533 cells for every one milliliter blood processed) and is biocompatible. This method will enable large cohort research to define the clinical and diagnostic value of CTC subtypes.

Exploring magnetohydrodynamic voltage distributions in the human body: Preliminary results

BACKGROUND

The aim of this study was to noninvasively measure regional contributions of vasculature in the human body using magnetohydrodynamic voltages (VMHD) obtained from electrocardiogram (ECG) recordings performed inside MRI's static magnetic field (B0). Integrating the regional VMHD over the Swave-Twave segment of the cardiac cycle (Vsegment) provides a non-invasive method for measuring regional blood volumes, which can be rapidly obtained during MRI without incurring additional cost.

METHODS

VMHD was extracted from 12-lead ECG traces acquired during gradual introduction into a 3T MRI. Regional contributions were computed utilizing weights based on B0's strength at specified distances from isocenter. Vsegment mapping was performed in six subjects and validated against MR angiograms (MRA).

RESULTS

Fluctuations in Vsegment, which presented as positive trace deflections, were found to be associated with aortic-arch flow in the thoracic cavity, the main branches of the abdominal aorta, and the bifurcation of the common iliac artery. The largest fluctuation corresponded to the location where the aortic arch was approximately orthogonal to B0. The smallest fluctuations corresponded to areas of vasculature that were parallel to B0. Significant correlations (specifically, Spearman's ranked correlation coefficients of 0.96 and 0.97 for abdominal and thoracic cavities, respectively) were found between the MRA and Vsegment maps (p < 0.001).

CONCLUSIONS

A novel non-invasive method to extract regional blood volumes from ECGs was developed and shown to be a rapid means to quantify peripheral and abdominal blood volumes.

Near infrared spectroscopy-guided exercise training for claudication in peripheral arterial disease

Rationale

Supervised treadmill exercise for claudication in peripheral arterial disease is effective but poorly tolerated because of ischemic leg pain. Near infrared spectroscopy allows non-invasive detection of muscle ischemia during exercise, allowing for characterization of tissue perfusion and oxygen utilization during training.

Objective

We evaluated walking time, muscle blood flow, and muscle mitochondrial capacity in patients with peripheral artery disease after a traditional pain-based walking program and after a muscle oxygen-guided walking program.

Method and results

Patients with peripheral artery disease trained thrice weekly in 40-minute-long sessions for 12 weeks, randomized to oxygen-guided training ( n = 8, age 72 ± 9.7 years, 25% female) versus traditional pain-based training ( n = 10, age 71.6 ± 8.8 years, 20% female). Oxygen-guided training intensity was determined by maintaining a 15% reduction in skeletal muscle oxygenation by near infrared spectroscopy rather than relying on symptoms of pain to determine exercise effort. Pain free and maximal walking times were measured with a 12-minute Gardner treadmill test. Gastrocnemius mitochondrial capacity and blood flow were measured using near infrared spectroscopy. Baseline pain-free walking time was similar on a Gardner treadmill test (2.5 ± 0.9 vs. 3.6 ± 1.0 min, p = 0.5). After training, oxygen-guided cohorts improved similar to pain-guided cohorts (pain-free walking time 6.7 ± 0.9 vs. 6.9 ± 1.1 min, p < 0.01 for change from baseline and p = 0.97 between cohorts). Mitochondrial capacity improved in both groups but more so in the pain-guided cohort than in the oxygen-guided cohort (38.8 ± 8.3 vs. 14.0 ± 9.3, p = 0.018). Resting muscle blood flow did not improve significantly in either group with training.

Conclusions

Oxygen-guided exercise training improves claudication comparable to pain-based training regimens. Adaptations in mitochondrial function rather than increases in limb perfusion may account for functional improvement. Increases in mitochondrial oxidative capacity may be proportional to the degree of tissue hypoxia during exercise.

Effect of exercise intensity on circulating microparticles in men and women

NEW FINDINGS

What is the central question of this study? What is the effect of exercise intensity on circulating microparticle populations in young, healthy men and women? What is the main finding and its importance? Acute, moderate-intensity continuous exercise and high-intensity interval exercise altered distinct microparticle populations during and after exercise in addition to a sex-specific response in CD62E⁺ microparticles. The microparticles studied contribute to cardiovascular disease progression, regulate vascular function and facilitate new blood vessel formation. Thus, characterizing the impact of intensity on exercise-induced microparticle responses advances our understanding of potential mechanisms underlying the beneficial vascular adaptations to exercise.

ABSTRACT

Circulating microparticles (MPs) are biological vectors of information within the cardiovascular system that elicit both deleterious and beneficial effects on the vasculature. Acute exercise has been shown to alter MP concentrations, probably through a shear stress-dependent mechanism, but evidence is limited. Therefore, we investigated the effect of exercise intensity on plasma levels of CD34⁺ and CD62E⁺ MPs in young, healthy men and women. Blood samples were collected before, during and after two energy-matched bouts of acute treadmill exercise: interval exercise (10 × 1 min intervals at ∼95% of maximal oxygen uptake V̇O2max) and continuous exercise (65% V̇O2max). Continuous exercise, but not interval exercise, reduced CD62E⁺ MP concentrations in men and women by 18% immediately after exercise (from 914.5 ± 589.6 to 754.4 ± 390.5 MPs μl^-1 ; P < 0.05), suggesting that mechanisms underlying exercise-induced CD62E⁺ MP dynamics are intensity dependent. Furthermore, continuous exercise reduced CD62E⁺ MPs in women by 19% (from 1030.6 ± 688.1 to 829.9 ± 435.4 MPs μl^-1 ; P < 0.05), but not in men. Although interval exercise did not alter CD62E⁺ MPs per se, the concentrations after interval exercise were higher than those observed after continuous exercise (P < 0.05). Conversely, CD34⁺ MPs did not fluctuate in response to short-duration acute continuous or interval exercise in men or women. Our results suggest that exercise-induced MP alterations are intensity dependent and sex specific and impact MP populations differentially.

Experimental intermittent ischemia augments exercise-induced inflammatory cytokine production

Acute exercise-induced inflammation is implicated in mediating the beneficial adaptations to regular exercise. Evidence suggests that reduced oxygen and/or blood flow to contracting muscle alters cytokine appearance. However, the acute inflammatory responses to hypoxic/ischemic exercise have been documented with inconsistent results and may not accurately reflect the ischemia produced during exercise in patients with ischemic cardiovascular diseases. Therefore, we determined the extent to which local inflammation is involved in the response to ischemic exercise. Fourteen healthy males performed unilateral isometric forearm contractions for 30 min with and without experimental ischemia. Blood was drawn at baseline, 5 and 10 min into exercise, at the end of exercise, and 30, 60, and 120 min after exercise. Oxygen saturation levels, as measured by near-infrared spectroscopy, were reduced by 10% and 41% during nonischemic and ischemic exercise, respectively. Nonischemic exercise did not affect cytokine values. Ischemia enhanced concentrations of basic fibroblast growth factor, interleukin (IL)-6, IL-10, tumor necrosis factor-alpha, and vascular endothelial growth factor during exercise, but IL-8 was not influenced by ischemic exercise. In conclusion, the present study demonstrates that ischemic, small-muscle endurance exercise elicits local inflammatory cytokine production compared with nonischemic exercise.

NEW & NOTEWORTHY We demonstrate that ischemic, small-muscle endurance exercise elicits local inflammatory cytokine production compared with nonischemic exercise. The present study advances our knowledge of the inflammatory response to exercise in a partial ischemic state, which may be relevant for understanding the therapeutic effects of exercise training for people with ischemic cardiovascular disease-associated comorbidities.

Reduced skeletal muscle oxidative capacity and impaired training adaptations in heart failure

Systolic heart failure (HF) is associated with exercise intolerance that has been attributed, in part, to skeletal muscle dysfunction. The purpose of this study was to compare skeletal muscle oxidative capacity and training-induced changes in oxidative capacity in participants with and without HF. Participants with HF (n = 16, 65 ± 6.6 years) were compared with control participants without HF (n = 23, 61 ± 5.0 years). A subset of participants (HF: n = 7, controls: n = 5) performed 4 weeks of wrist-flexor exercise training. Skeletal muscle oxidative capacity was determined from the recovery kinetics of muscle oxygen consumption measured by near-infrared spectroscopy (NIRS) following a brief bout of wrist-flexor exercise. Oxidative capacity, prior to exercise training, was significantly lower in the HF participants in both the dominant (1.31 ± 0.30 min⁻¹ vs. 1.59 ± 0.25 min⁻¹, P = 0.002; HF and control groups, respectively) and nondominant arms (1.29 ± 0.24 min⁻¹ vs. 1.46 ± 0.23 min⁻¹, P = 0.04; HF and control groups, respectively). Following 4 weeks of endurance training, there was a significant difference in the training response between HF and controls, as the difference in oxidative training adaptations was 0.69 ± 0.12 min⁻¹ (P < 0.001, 95% CI 0.43, 0.96). The wrist-flexor training induced a ∼50% improvement in oxidative capacity in participants without HF (mean difference from baseline = 0.66 ± 0.09 min⁻¹, P < 0.001, 95% CI 0.33, 0.98), whereas participants with HF showed no improvement in oxidative capacity (mean difference from baseline = −0.04 ± 0.08 min⁻¹, P = 0.66, 95% CI −0.24, 0.31), suggesting impairments in mitochondrial biogenesis. In conclusion, participants with HF had reduced oxidative capacity and impaired oxidative adaptations to endurance exercise compared to controls.

Contribution of endothelium-derived hyperpolarizing factor to exercise-induced vasodilation in health and hypercholesterolemia

The role of endothelium-derived hyperpolarizing factor (EDHF) in either the healthy circulation or in those with hypercholesterolemia is unknown. In healthy and hypercholesterolemic subjects, we measured forearm blood flow (FBF) using strain-gauge plethysmography at rest, during graded handgrip exercise, and after sodium nitroprusside infusion. Measurements were repeated after l-NMMA, tetraethylammonium (TEA), and combined infusions. At rest, l-NMMA infusion reduced FBF in healthy but not hypercholesterolemic subjects. At peak exercise, vasodilation was lower in hypercholesterolemic compared to healthy subjects (274% vs 438% increase in FBF, p=0.017). TEA infusion reduced exercise-induced vasodilation in both healthy and hypercholesterolemic subjects (27%, p<0.0001 and -20%, p<0.0001, respectively). The addition of l-NMMA to TEA further reduced FBF in healthy (-14%, p=0.012) but not in hypercholesterolemic subjects, indicating a reduced nitric oxide and greater EDHF-mediated contribution to exercise-induced vasodilation in hypercholesterolemia. In conclusion, exercise-induced vasodilation is impaired and predominantly mediated by EDHF in hypercholesterolemic subjects. CLINICAL TRIAL REGISTRATION IDENTIFIER NCT00166166:

Acute and chronic effects of sprint interval exercise on postprandial lipemia in women at-risk for the metabolic syndrome

Individuals diagnosed with the metabolic syndrome (MetS) exhibit elevated postprandial lipemia (PPL). The aims of this investigation were to determine 1) if an acute bout of sprint interval training (SIT) attenuates PPL; and 2) if the attenuation of PPL following 6 wk of SIT is magnified compared with a single session of SIT prior to training in women at-risk for MetS (n = 45; 30-65 yr). Women were randomized to SIT (n = 22) or a nonexercise control (n = 23; CON) for 6 wk. Postprandial responses to a high-fat meal challenge (HFMC) were assessed in the CON group before (B-HFMC) and after (Post-HFMC) without prior exercise and in the SIT group at baseline (B-HFMC) without prior exercise, after an acute bout of SIT (four 30-s all-out sprints with 4-min recovery) prior to (Pre-HFMC), and after the 6-wk intervention (Post-HFMC). Responses to the HFMC were assessed by collecting venous blood samples in the fasted state and at 0, 30, 60, 120, and 180 min postprandial. Compared with baseline, an acute bout of SIT before (Pre-HFMC) and after the 6-wk intervention (Post-HFMC) significantly attenuated fasted TG (P < 0.05; 16.6% and 12.3%, respectively) and postprandial area under the curve (13.1% and 9.7%, respectively; tAUC) TG responses. There was no difference in fasted or tAUC TG responses between Pre-HFMC and Post-HFMC. SIT is an effective mode of exercise to reduce fasted and postprandial TG concentrations in women at-risk for MetS. Six weeks of SIT does not magnify the attenuation of PPL in response to a single session of SIT.

Left-ventricular mechanical activation and aortic-arch orientation recovered from magneto-hydrodynamic voltages observed in 12-lead ECGs obtained inside MRIs: a feasibility study

To explore use of the Magnetohydrodynamic Voltage (VMHD), observed in intra-MRI 12-lead electrocardiograms (ECG), to indicate the timing of the onset of left-ventricular mechanical activation (LVMA) and the orientation of the aortic-arch (AAO). Blood flow through the aortic arch during systole, in the presence of the MRI magnetic field (B 0), generates VMHD. Since the magnitude and direction of VMHD are determined by the timing and directionality of blood flow relative to B 0, we hypothesized that clinically useful measures, LVMA and AAO, could be extracted from temporal and vectorial VMHD characteristics. VMHD signals were extracted from 12-lead ECG traces by comparing traces obtained inside and outside the MRI scanner. VMHD was converted into the Vectorcardiogram frame of reference. LVMA was quantified in 1 subject at 1.5T and 3 subjects at 3T, and the result compared to CINE MRI. AAO was inferred for 4 subjects at 3T and compared to anatomical imaging of the aortic arch orientation in the transverse plane. A < 10% error was observed in LVMA measurements, while a < 3° error was observed in aortic arch orientation measurements. The temporal and vectorial nature of VMHD is useful in estimating these clinically relevant parameters.

Endothelium-derived hyperpolarizing factor mediates bradykinin-stimulated tissue plasminogen activator release in humans

AIMS

Bradykinin (BK) stimulates tissue plasminogen activator (t-PA) release from human endothelium. Although BK stimulates both nitric oxide and endothelium-derived hyperpolarizing factor (EDHF) release, the role of EDHF in t-PA release remains unexplored. This study sought to determine the mechanisms of BK-stimulated t-PA release in the forearm vasculature of healthy human subjects.

METHODS

In 33 healthy subjects (age 40.3 ± 1.9 years), forearm blood flow (FBF) and t-PA release were measured at rest and after intra-arterial infusions of BK (400 ng/min) and sodium nitroprusside (3.2 mg/min). Measurements were repeated after intra-arterial infusion of tetraethylammonium chloride (TEA; 1 µmol/min), fluconazole (0.4 µmol·min(-1)·l(-1)), and N(G)-monomethyl-L-arginine (L-NMMA, 8 µmol/min) to block nitric oxide, and their combination in separate studies.

RESULTS

BK significantly increased net t-PA release across the forearm (p < 0.0001). Fluconazole attenuated both BK-mediated vasodilation (-23.3 ± 2.7% FBF, p < 0.0001) and t-PA release (from 50.9 ± 9.0 to 21.3 ± 8.9 ng/min/100 ml, p = 0.02). TEA attenuated FBF (-14.7 ± 3.2%, p = 0.002) and abolished BK-stimulated t-PA release (from 22.9 ± 5.7 to -0.8 ± 3.6 ng/min/100 ml, p = 0.0002). L-NMMA attenuated FBF (p < 0.0001), but did not inhibit BK-induced t-PA release (nonsignificant).

CONCLUSION

BK-stimulated t-PA release is partly due to cytochrome P450-derived epoxides and is inhibited by K(+)Ca channel blockade. Thus, BK stimulates both EDHF-dependent vasodilation and t-PA release.

Differences in vascular nitric oxide and endothelium-derived hyperpolarizing factor bioavailability in blacks and whites

OBJECTIVE

Abnormalities in nitric oxide (NO) bioavailability have been reported in blacks. Whether there are differences in endothelium-derived hyperpolarizing factor (EDHF) in addition to NO between blacks and whites and how these affect physiological vasodilation remain unknown. We hypothesized that the bioavailability of vascular NO and EDHF, at rest and with pharmacological and physiological vasodilation, varies between whites and blacks.

APPROACH AND RESULTS

In 74 white and 86 black subjects without known cardiovascular disease risk factors, forearm blood flow was measured using plethysmography at rest and during inhibition of NO with N(G)-monomethyl-L-arginine and of K(+) Ca channels (EDHF) with tetraethylammonium. The reduction in resting forearm blood flow was greater with N(G)-monomethyl-L-arginine (P=0.019) and similar with tetraethylammonium in whites compared with blacks. Vasodilation with bradykinin, acetylcholine, and sodium nitroprusside was lower in blacks compared with whites (all P<0.0001). Inhibition with N(G)-monomethyl-L-arginine was greater in whites compared with blacks with bradykinin, acetylcholine, and exercise. Inhibition with tetraethylammonium was lower in blacks with bradykinin, but greater during exercise and with acetylcholine.

CONCLUSIONS

The contribution to both resting and stimulus-mediated vasodilator tone of NO is greater in whites compared with blacks. EDHF partly compensates for the reduced NO release in exercise and acetylcholine-mediated vasodilation in blacks. Preserved EDHF but reduced NO bioavailability and sensitivity characterizes the vasculature in healthy blacks.

CLINICAL TRIAL REGISTRATION URL

http://clinicaltrials.gov/. Unique identifier: NCT00166166.

Circulating proangiogenic cell activity is associated with cardiovascular disease risk

Vascular injury mobilizes bone marrow-derived proangiogenic cells into the circulation, where these cells can facilitate vascular repair and new vessel formation. We sought to determine the relationship between a new biomarker of circulating bone marrow-derived proangiogenic cell activity, the presence of atherosclerotic cardiovascular disease (CVD) and its risk factors, and clinical outcomes. Circulating proangiogenic cell activity was estimated using a reproducible angiogenic colony-forming unit (CFU-A) assay in 532 clinically stable subjects aged 20 to 90 years and ranging in the CVD risk spectrum from those who are healthy without risk factors to those with active CVD. CFU-A counts increased with the burden of CVD risk factors (p < 0.001). CFU-A counts were higher in subjects with symptomatic CVD than in those without (p < 0.001). During follow-up of 232 subjects with CVD, CFU-A counts were higher in those with death, myocardial infarction, or stroke than in those without (110 [70-173] vs 84 [51-136], p = 0.01). Therefore, we conclude that circulating proangiogenic cell activity, as estimated by CFU-A counts, increases with CVD risk factor burden and in the presence of established CVD. Furthermore, higher circulating proangiogenic cell activity is associated with worse clinical outcome in those with CVD.

The differential effect of statins on oxidative stress and endothelial function: atorvastatin versus pravastatin

BACKGROUND

Atherogenic risk in subjects with metabolic syndrome is partly mediated by increased oxidative stress and subsequent endothelial dysfunction. Clinical trials have demonstrated differences in outcomes between subjects receiving lipophilic statins (atorvastatin) compared with hydrophilic statins (pravastatin). However, whether these findings are attributable to differences in the doses administered or to nonlipid-lowering pleiotropic effects of statins on oxidative stress and vascular function remains unknown. We hypothesized that equipotent doses of these two statins will have divergent effects on markers of oxidative stress and endothelial function.

METHODS

Thirty-six subjects with hyperlipidemia and metabolic syndrome and/or diabetes were randomized in a double-blind manner to either pravastatin 80 mg or atorvastatin 10 mg daily. Oxidative stress (dROMs assay that measures lipid hydroperoxides, plasma thiobarbituric acid reactive substances [TBARS], and aminothiol levels) and brachial artery flow-mediated dilation (FMD) were measured at baseline and after 12 weeks of statin therapy.

RESULTS

Statin therapy reduced serum low-density lipoprotein cholesterol levels equally in both groups. Atorvastatin therapy was associated with a significant reduction in TBARS (P = .006) and dROMs levels (P = .02), which was not observed in subjects treated with pravastatin. Endothelial function improved with statin therapy (P = .02), but there was no difference between the statin groups.

CONCLUSION

In hyperlipidemic subjects with metabolic syndrome, atorvastatin is associated with a greater reduction in lipid markers of oxidation compared with pravastatin. Whether these effects are responsible for the outcome differences in trials comparing these agents needs further investigation.

Endothelium-derived hyperpolarizing factor determines resting and stimulated forearm vasodilator tone in health and in disease

BACKGROUND

We assessed the contribution of endothelium-derived hyperpolarizing factors to resting and agonist-stimulated vasodilator tone in health and disease. Tetraethylammonium chloride (TEA) was used to inhibit K(+)(Ca) channel activation and fluconazole was used to inhibit cytochrome P450 2C9-mediated epoxyeicosatrienoic acid synthesis. We hypothesized that endothelium-derived hyperpolarizing factors contribute to resting vascular tone by K(+)(Ca) channel activation and epoxyeicosatrienoic acid release and that endothelium-derived hyperpolarizing factors compensate for reduced nitric oxide bioavailability at rest and with endothelium-dependent vasodilators.

METHODS AND RESULTS

In 103 healthy subjects and 71 nonhypertensive subjects with multiple risk factors, we measured resting forearm blood flow (FBF) using venous occlusion plethysmography before and after intra-arterial infusions of N(G)-monomethyl-l-arginine (L-NMMA), TEA, fluconazole, and their combination. The effects of these antagonists on resting FBF and on bradykinin- and acetylcholine-mediated vasodilation were studied. Resting FBF decreased with TEA and L-NMMA in all subjects (P<0.001); however, the vasoconstrictor response to L-NMMA was greater (P=0.04) and to TEA was lower (P=0.04) in healthy subjects compared with those with risk factors. Fluconazole decreased resting FBF in all subjects, and the addition of TEA further reduced FBF after fluconazole, suggesting that cytochrome P450 metabolites and other hyperpolarizing factor(s) activate K(+)(Ca) channels. Both L-NMMA and TEA attenuated bradykinin-mediated vasodilation in healthy and hypercholesterolemic subjects (P<0.001). In contrast, acetylcholine-mediated vasodilation remained unchanged with TEA in healthy subjects but was significantly attenuated in hypercholesterolemia (P<0.04).

CONCLUSIONS

First, by activating TEA-inhibitable K(+)(Ca) channels, endothelium-derived hyperpolarizing factors, together with nitric oxide, contribute to resting microvascular dilator tone. The contribution of K(+)(Ca) channel activation compared with nitric oxide is greater in those with multiple risk factors compared with healthy subjects. Second, activation of K(+)(Ca) channels is only partly through epoxyeicosatrienoic acid release, indicating the presence of other hyperpolarizing mechanisms. Third, bradykinin, but not acetylcholine, stimulates K(+)(Ca) channel-mediated vasodilation in healthy subjects, whereas in hypercholesterolemia, K(+)(Ca) channel-mediated vasodilation compensates for the reduced nitric oxide activity. Thus, enhanced endothelium-derived hyperpolarizing factor activity in conditions of nitric oxide deficiency contributes to maintenance of resting and agonist-stimulated vasodilation. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00166166.

Bone marrow mobilization with granulocyte macrophage colony-stimulating factor improves endothelial dysfunction and exercise capacity in patients with peripheral arterial disease

BACKGROUND

We hypothesized that granulocyte macrophage colony-stimulating factor (GM-CSF) administration will be safe and will improve endothelial dysfunction and exercise capacity by mobilizing progenitor cells in patients with peripheral arterial disease (PAD).

METHODS

Forty-five patients with PAD received thrice-weekly injections for 2 weeks of 3, 6, or 10 microg/kg per day of GM-CSF or placebo in successive cohorts of 15 subjects randomized 2:1 to drug or placebo. CD34+ mononuclear cell subsets and colony formation assay, endothelial function, ankle-brachial index, and walking capacity were measured.

RESULTS

Granulocyte macrophage colony-stimulating factor administration was safe. After pooling data from GM-CSF cohorts, at 2 weeks, there was a significant increase in total leukocytes (43%, P < .0001), CD34+ cells (46%, P = .035), and colony-forming units (31%, P = .026, week 1). At 12 weeks, endothelial function improved with GM-CSF (flow-mediated vasodilation increased by 59%, P < .01) as did pain-free treadmill walking time (38 seconds, P = .008) and total treadmill walking time (55 seconds, P = .016). Corresponding changes were not observed in the placebo group.

CONCLUSIONS

Granulocyte macrophage colony-stimulating factor therapy in patients with PAD was associated with mobilization of progenitor cells, improvement of endothelial dysfunction, and exercise capacity. The efficacy of strategies designed to mobilize bone marrow progenitors warrants further study in patients with PAD.

Salmonella meningitis in adults infected with HIV: case report and review of the literature

We report a case of Salmonella infantis meningitis in a patient infected with HIV who was successfully treated with 4 weeks of therapy and has had no relapses after 12 months of follow-up. Only 10 episodes of Salmonella species meningitis in patients infected with HIV are reported in the literature.