Search

Background— Despite an appreciable increase in basal coronary blood flow in cyanotic congenital heart disease, flow reserve remains normal. We hypothesized that preservation of flow reserve resides in remodeling of the coronary microcirculation. Microcirculatory morphometric analyses were performed to test this hypothesis. Methods and Results— Necropsy specimens from 4 sources were studied: (1) hearts from patients with Eisenmenger’s syndrome (A; n=5), (2) structurally abnormal hearts with ventricular hypertrophy (B; n=8), (3) structurally normal hearts with ventricular hypertrophy (C; n=6), and (4) normal hearts (D; n=5). To compare responses of the microcirculation to hypoxia versus hypertrophy, sections were taken from the left ventricular free wall, which in group A, was hypoxemic but not hypertrophied; in groups B and C, was hypertrophied but not hypoxemic; and in group D, was neither hypertrophied nor hypoxemic. Coronary arterioles were immunolabeled for smooth muscle α-actin. Measured morphometric parameters included long and short axes, area, and perimeter. Arteriolar length, volume and surface densities were calculated. There was a significant intergroup difference for arteriolar length density ( P =0.03) and diameter ( P =0.03). Total length density in group A hearts was markedly lower, but mean arteriolar diameter was significantly greater (34%) compared with group B ( P =0.03). Arteriolar volume density was similar to that in the other groups. Conclusions— Remodeling of the coronary microcirculation is the key mechanism for preservation of flow reserve in cyanotic congenital heart disease. The increase in short axis (diameter) compensated for lower arteriolar length density and was the principal anatomic basis for maintenance of normal flow reserve.

Background— Hypercholesterolemia and sickle cell disease (SCD) impair endothelium-dependent vasodilation by dissimilar mechanisms. Hypercholesterolemia impairs vasodilation by a low-density lipoprotein (LDL)–dependent mechanism. SCD has been characterized as a chronic state of inflammation in which xanthine oxidase (XO) from ischemic tissues increases vascular superoxide anion (O 2 · − ) generation. Recent reports indicate that apolipoprotein (apo) A-1 mimetics inhibit atherosclerosis in LDL receptor–null ( Ldlr −/− ) mice fed Western diets. Here we hypothesize that L-4F, an apoA-1 mimetic, preserves vasodilation in hypercholesterolemia and SCD by decreasing mechanisms that increase O 2 · − generation. Methods and Results— Arterioles were isolated from hypercholesterolemic Ldlr −/− mice and from SCD mice that were treated with either saline or L-4F (1 mg/kg per day). Vasodilation in response to acetylcholine was determined by videomicroscopy. Effects of L-4F on LDL-induced increases in endothelium-dependent O 2 · − generation were determined on arterial segments via the hydroethidine assay and on stimulated endothelial cell cultures via superoxide dismutase–inhibitable ferricytochrome c reduction. Effects of L-4F on XO bound to pulmonary arterioles and content in livers of SCD mice were determined by immunofluorescence. Hypercholesterolemia impaired vasodilation in Ldlr −/− mice, which L-4F dramatically improved. L-4F inhibited LDL-induced increases in O 2 · − in arterial segments and in stimulated cultures. SCD impaired vasodilation, increased XO bound to pulmonary endothelium, and decreased liver XO content. L-4F dramatically improved vasodilation, decreased XO bound to pulmonary endothelium, and increased liver XO content compared with levels in untreated SCD mice. Conclusions— These data show that L-4F protects endothelium-dependent vasodilation in hypercholesterolemia and SCD. Our findings suggest that L-4F restores vascular endothelial function in diverse models of disease and may be applicable to treating a variety of vascular diseases.

Background: The mitochondria exist in a state of balance between fission (fragmentation) and fusion (joining of mitochondrial segments). Disease is characterized by excessive fission, leading to an overproduction of mitochondrial reactive oxygen species (ROS) which mediate pathological changes in vascular endothelium. Dynamin-related protein-1 (DRP-1) is the primary mediator of mitochondrial fission. The therapeutic benefit of exercise is largely due to increased endothelial shear; however the effects of shear stress on DRP-1 expression and mitochondrial structure are unknown. Hypothesis: Shear stress reduces mitochondrial fission in cultured human umbilical vein endothelial cells (HUVECs) exposed to the fission-inducing stimulus angiotensin II (ANG II) by reducing DRP-1 expression and activity. Methods: HUVECs were treated with MitoRFP for 24 hours to fluorescently label the mitochondria, then were exposed to ANG II (10 pM; 4 hours), fixed, and 25 random cells/group were imaged with a confocal microscope. Separate groups of cells were sheared (15 dyn/cm2; 24 hours) immediately following ANG II exposure using the Ibidi Pump System. To quantify mitochondrial fission, images were converted to binary color and ImageJ was used to count non-contiguous mitochondrial fragments. This value was divided by the number of pixels in the mitochondrial network and multiplied by 1000 to yield a Mitochondrial Fragmentation Index (MFI). Total DRP-1 expression and phosphorylation of the S616 activator and S637 suppressor sites were analyzed by Western blot. Results: ANG II increased MFI (1.13±0.25 vs. 0.75±0.06), DRP-1 expression (+48%) and phosphorylation of the S616 activator site (+141%; p Conclusions: High shear stress restores mitochondrial network integrity in HUVECs exposed to ANG II, suggesting exercise may promote vascular health by modulating mitochondrial fission.

Background: Over the last ten years there has been a significant increase in anticoagulation use in various conditions. However, trends in incidence and outcomes of adverse events associated with anticoagulation are not well defined. Methods: We analyzed patients in the Nationwide Inpatient Sample (NIS) between 2002-2011 with co-diagnosis of adverse effects of anticoagulation in therapeutic use. Primary outcome was trend in hospital admissions with adverse effects from anticoagulation. Secondary outcome was trends in in-hospital mortality. Results: During our analysis hospital admissions associate with adverse effects of anticoagulation increased 135.5% from 99,383 in 2002 to 234,046 in 2011. During the same period the number of hospitalizations with patients on long term anticoagulation more than tripled from 422,145 to 1,557,603. The most common probable indications for anticoagulation were atrial fibrillation (50.2%), personal history of venous thrombosis (12.5%) and prosthetic heart valve (7.1%). Clinical patterns of bleeding were gastrointestinal (15.7%), intracranial hemorrhage (2.5%) and gross hematuria (1.5%). Blood transfusion during index hospitalization with adverse effects of anticoagulation increased as well (27.4% in 2002 to 36.0% in 2011, p Conclusions: Our analysis showed an increasing trend in hospitalizations associated with adverse effects from therapeutic use of anticoagulants. With increasing use of these agents for appropriate guideline recommended indications caution needs to be exercised in patients with increased bleeding risk.

Background —K + channel activation in vascular smooth muscle cells (VSMCs) plays a key role in regulating vascular tone. It has been proposed that endothelium-derived hyperpolarizing factor (EDHF) contributes to microvascular dilation more than nitric oxide (NO) does. Whether hyperpolarization is important for coronary arteriolar dilation in humans is not known. Bradykinin (BK), an endogenous vasoactive substance, is released from ischemic myocardium and regulates coronary resistance. Therefore, we tested the effects of inhibiting NO synthase, cyclooxygenase, and K + channels on the changes in diameter and membrane potential (Em) in response to BK in isolated human coronary microvessels. Methods and Results —Arterioles (97±4 μm; n=120) dissected from human right atrial appendages (n=78) were cannulated at a distending pressure of 60 mm Hg and zero flow. Changes in vessel diameter (video microscopy) and VSMC Em (glass microelectrodes) were measured simultaneously. In vessels constricted and depolarized (Em; −50±3 to −28±2 mV) with endothelin-1 (ET), dilation to BK was associated with greater membrane hyperpolarization (−48±3 mV at 10 −6 mol/L) than dilation to sodium nitroprusside (SNP) (−34±2 mV at 10 −4 mol/L) for similar degrees of dilation. Treatment with N ω -nitro- l -arginine methyl ester (L-NAME; 10 −4 mol/L), an NO synthase inhibitor, partially decreased dilation to BK (maximum dilation 61±10% versus control 92±4%; P −8 mol/L), a large-conductance Ca 2+ -activated K + channel blocker, or apamin (10 −7 mol/L), a small-conductance Ca 2+ -activated K + channel blocker, inhibited both dilation (CTX 22±6% and apamin 45±10% versus control 69±6%; P P −6 mol/L), an ATP-sensitive K + channel blocker, was without effect. Conclusions —Vasodilation of human coronary arterioles to BK is largely dependent on membrane hyperpolarization by Ca 2+ -activated K + channel activation, with apparently less of a role for endothelium-derived NO. This suggests a role for K + channel activation in regulating human coronary arteriolar tone.

Background Nerve growth factor (NGF) is produced rapidly in myocardium after brief myocardial ischemia. It contributes to the maintenance of neural integrity in several tissues. We examined the effect of exogenous and endogenous NGF on ischemia-induced dysfunction of cardiac sympathetic nerves. Methods and Results In anesthetized dogs, bilateral stellate stimulation was performed, measuring changes in coronary vascular resistance (%ΔCVR) before and after release of either a 7- or 15-minute occlusion of the left anterior descending coronary artery (LAD). NGF (10 ng·kg −1 ·min −1 , n=5) or vehicle (n=6) was infused into the LAD in dogs during a 15-minute LAD occlusion. In separate experiments, antibody to NGF (anti-NGF, 2 ng·kg −1 ·min −1 , n=5) or vehicle (n=6) was infused into dogs during a 7-minute LAD occlusion. After release of a 15-minute LAD occlusion, attenuation of the coronary constriction to stellate stimulation was seen in the vehicle group (30±3% to 15±1% increase in CVR, P P =NS) but attenuated %ΔCVR in the anti-NGF group (39±8% to 17±2%, P Conclusions We conclude that exogenously infused and endogenously released NGF protects against postischemic neural stunning of sympathetic cardiac innervation.

Background : Acute hyperglycemia (HG) impairs endothelial function, which may be related to hyperpolarization of the inner mitochondrial membrane and excessive production of mitochondrial superoxide (ROS). Mitochondrial uncoupling agents could potentially reverse endothelial dysfunction due to HG in intact human arterioles. Methods : Human adipose arterioles were incubated in either euglycemic (NG, 5mM) or hyperglycemic (HG, 33mM) buffer for 4 hours. Vessels were then exposed to increasing doses of acetylcholine (ACh) in the presence and absence of NADPH oxidase inhibitor gp91ds-tat or CCCP, (100 nM), a mitochondrial membrane uncoupling agent. Vascular superoxide levels were also measured after incubation with NG and HG using a chemiluminescent probe (L-012) in the absence and presence of 1 and 2 above. Results : ACh-induced vasodilation was impaired by HG vs. NG control (P0.90 vs. NG). Endothelium-dependent vasodilation in HG vessels was greater after CCCP compared to gp91ds-tat (P Conclusion : HG-induced endothelial dysfunction is reversed with partial uncoupling of mitochondrial oxidative phosphorylation. Mitochondrial uncoupling more than NADPH oxidase blockade improves endothelial dysfunction due to HG.

Light chain amyloidosis (AL) is a rare disease associated with poor survival especially in the presence of cardiac involvement. Late gadolinium enhancement (LGE) on cardiac MRI was recently shown to correspond to cardiac amyloid deposition but the long term prognostic implication of this finding has not been established. The aim is to compare long-term survival between AL subjects with and without LGE. 25 biopsy-proven AL subjects (12 females, 61 ± 3 years) underwent cardiac MRI while undergoing workup for AL. Survival status was followed 24 ± 10 months post-MRI and compared between LGE positive and negative subjects. LGE was present in 19 (76%) AL subjects. 13 (52%) were in Heart Failure (HF) Class I with 7 (28%), 2 (8%) and 3 (12%) in Class II, III, IV respectively. LVEF was 65 ± 18% in LGE positive and 69 ± 12% LGE negative patients (p = 0.6). On follow up 10/19 LGE positive and 0/6 LGE negative patients died (log rank p = 0.03). LGE and initial presenting HF class (log rank p = 0.001) were associated with poor survival (see figure ). There was no significant association between LGE and initial presenting HF class (Fisher’s exact p = 0.4). This is the first long-term study demonstrating the prognostic significance of LGE in AL amyloidosis. Although small sample size precludes modeling the independent prognostic value of LGE, the lack of strong association with HF class and the presence of LGE in HF Class I subjects suggest additional utility of LGE in assessing the prognosis of AL subjects.

Light chain amyloidosis (AL), a plasma cell dyscrasia, is often fatal in patients with heart failure yet the mechanism of injury is unknown. We hypothesize that AL light chains (LC) acutely cause endothelial dysfunction in coronary arterioles. The aims are to measure endothelium-dependent and independent dilation and reactive oxygen species (ROS) in human coronary arterioles exposed to LC from AL subjects. Urine LC was isolated from 3 AL subjects by dialysis and lyophilization. Separately, 15 coronary arterioles were isolated from discarded atrial tissue from 12 non-AL subjects without significant vascular disease or diabetes undergoing open heart surgery (8 males, 70 ± 11 years). Arterioles were pressure-mounted and vessel diameter measured by videomicroscopy. Post-preconstriction with endothelin-1, vessels were exposed to vehicle and sequential doses of bradykinin (endothelium-mediated,10 −10 to 10 −6 M) then papaverine (endothelium-independent, 10 −4 M) were given and dilation was measured. Dilator response was again measured after 20 μg/mL of LC. Coronary arterioles were separately exposed to vehicle and LC and mitochondrial superoxide (MitoSox Red) and hydrogen peroxide (dichlorofluoroscein) were measured by fluorescence microscopy. see figure. Brief exposure to AL amyloid light chains impairs endothelium-dependent coronary vasodilation. This is associated with increased ROS production. This is the first human study demonstrating endothelial dysfunction in coronary microvasculature caused by AL LC. The vascular dysfunction and oxidative stress may be an important mechanism in the pathophysiology of this fatal disease.

Background —Flow-induced vasodilation (FID) is a physiological mechanism for regulating coronary flow and is mediated largely by nitric oxide (NO) in animals. Because hyperpolarizing mechanisms may play a greater role than NO in the microcirculation, we hypothesized that hyperpolarization contributes importantly to FID of human coronary arterioles. Methods and Results —Arterioles from atria or ventricles were cannulated for videomicroscopy. Membrane potential of vascular smooth muscle cells (VSMCs) was measured simultaneously. After constriction with endothelin-1, increases in flow induced an endothelium-dependent vasodilation. Nω -Nitro- l -arginine methyl ester 10 − 4 mol/L modestly impaired FID of arterioles from patients without coronary artery disease (CAD), whereas no inhibition was seen in arterioles from patients with CAD. Indomethacin 10 − 5 mol/L was without effect, but 40 mmol/L KCl attenuated maximal FID. Tetraethylammonium 10 − 3 mol/L but not glibenclamide 10 − 6 mol/L reduced FID. Charybdotoxin 10 − 8 mol/L impaired both FID (15±3% versus 75±12%, P P − 6 mol/L or 17-octadecynoic acid 10 − 5 mol/L reduced FID. By multivariate analysis, age was an independent predictor for the reduced FID. Conclusions —We conclude that shear stress induces endothelium-dependent vasodilation, hyperpolarizing VSMCs through opening Ca 2+ -activated K + channels in human coronary arterioles. In subjects without CAD, NO contributes to FID. NO and prostaglandins play no role in patients with CAD; rather, cytochrome P450 metabolites are involved. This is consistent with a role for endothelium-derived hyperpolarizing factor in FID of the human coronary microcirculation.