Impaired microcirculation in heart failure

Oxygenation measurement by multi-wavelength oxygen-dependent phosphorescence and delayed fluorescence: catchment depth and application in intact heart

Oxygen delivery and metabolism represent key factors for organ function in health and disease. We describe the optical key characteristics of a technique to comprehensively measure oxygen tension (PO(2)) in myocardium, using oxygen-dependent quenching of phosphorescence and delayed fluorescence of porphyrins, by means of Monte Carlo simulations and ex vivo experiments. Oxyphor G2 (microvascular PO(2)) was excited at 442 nm and 632 nm and protoporphyrin IX (mitochondrial PO(2)) at 510 nm. This resulted in catchment depths of 161 (86) µm, 350 (307) µm and 262 (255) µm respectively, as estimated by Monte Carlo simulations and ex vivo experiments (brackets). The feasibility to detect changes in oxygenation within separate anatomical compartments is demonstrated in rat heart in vivo. Schematic of ex vivo measurements.

Cardiac Resynchronization Improves Microcirculation

BACKGROUND

Although it is known that cardiac resynchronization therapy (CRT) in heart failure (HF) patients improves systemic circulation, its acute effects on microcirculation are as yet unknown. Therefore we investigated the sublingual microcirculatory changes in HF patients from CRT and right ventricular (RV) pacing by use of orthogonal polarization spectral (OPS) imaging.

METHODS AND RESULTS

Twelve consecutive HF patients with a CRT device and 20 healthy individuals (HI) were included. Acute microcirculatory changes were assessed by functional capillary density (FCD) and capillary velocity (CV) measurement 6 months after CRT. FCD and CV were measured in HF patients sublingually after 15 minutes of programming 1 of 3 pacing modalities in random order (no pacing, RV pacing, and CRT). FCD was significantly higher in HI (11.2 +/- 2.1 cm/cm(2)) compared with HF patients with RV pacing (8.9 +/- 1.9 cm/cm(2); P = .03) and no pacing (8.3 +/- 2.4 cm/cm(2); P = .02). CRT (12.1 +/- 2.2 cm/cm(2)) significantly increased FCD in HF patients compared with RV pacing (8.9 +/- 1.9 cm/cm(2); P = .006) and no pacing (8.3 +/- 2.4 cm/cm(2); P = .008). CV was normal in all patients with or without pacing.

CONCLUSIONS

CRT improves microcirculatory function as assessed by OPS imaging.

Statins and the endothelium

Statins have been shown to have pleiotropic effects apart from serum lipid-lowering effect in human. One of the major target organs for the effects of statins is the vascular endothelium, which plays an important role in the development of atherosclerosis and angiogenesis. Recent numerous studies have shown that the statins' cholesterol-independent vascular effects appear to involve directly restoring or improving endothelial function by increasing NO production, promoting re-endothelialization after arterial injury, and inhibiting inflammatory responses within the vessel wall that are thought to contribute to atherosclerosis. This review provides an update of the unique effects of statins on endothelial cells including endothelial progenitor cells as well as highlighting the therapeutic potential of statins beyond their established lipid-lowering effects.

Microvascular abnormalities in chronic heart failure: a cross-sectional analysis

OBJECTIVES

Similar to what has been found in hypertension, elevated peripheral resistance in chronic heart failure (CHF) might be related to microvascular constriction and rarefaction. Our objective was to evaluate both structural and functional microvascular changes in patients with CHF in relation to left ventricular function and neurohumoral activation.

METHODS

In 25 patients with mild and severe CHF (New York Heart Association class I-II [n = 11] and class III-IV [n = 14]) and 10 age-matched healthy subjects, we studied microvascular density, diameters, and morphology of the bulbar conjunctiva and skin nailfold using intravital microscopy.

RESULTS

Total conjunctival microvascular density was higher in patients with mild heart failure compared with healthy controls, whereas it was lower in severe heart failure (medians, 6.75, 4.31, and 3.56 mm/mm2, respectively, p < 0.01). In patients with heart failure, venular density was correlated with left ventricular ejection fraction. Nailfold capillary recruitment during postocclusive reactive hyperemia, a measure of functional reserve capacity, was impaired in patients with severe CHF (p < 0.05). Furthermore, in severe CHF, more abnormal capillaries and enlarged diameters were found in the nailfold (p < 0.05).

CONCLUSIONS

In heart failure, several microvascular abnormalities occur that differ, depending on the severity of this condition.

Glial, vascular, and neuronal cytogenesis in whole-mounted cat retina

A method was developed for detecting cytogenesis in retinal whole-mount preparations by bromodeoxyuridine (BrdU) immunohistochemistry. Because BrdU is a nonspecific marker that labels all cells in the S phase of the cell cycle, it is ideally combined with other cell-specific markers to study the cytogenesis of specific cell types. Double-label protocols to visualize mitotically active astrocytes and cells associated with the forming vasculature have been developed and applied to the retina. This approach revealed that, during normal development of the kitten retina, vascular mitogenesis occurs predominantly in the ganglion cell and nerve fiber layers, where the inner retinal plexus is formed by a process involving transformation of mesenchymal precursor cells and division of vascular endothelial cells. The peak density of vascular mitogenesis moved in a central-to-peripheral manner and was associated with the leading edge of the forming capillary plexus. A small number of dividing vascular endothelial cells was also associated with angiogenesis, the process responsible for the formation of the outer retinal plexus, vessels at the area centralis, and the radial peripapillary capillaries. Cytogenesis associated with astrocytes occurred in the ganglion cell and nerve fiber layers but was apparent predominantly at or close to the optic nerve head. Confirming earlier studies, neuronal mitogenesis was shown to occur predominantly at the ventricular zone, first at the area centralis and spreading peripherally with increasing maturity. A second region of neuronal cytogenesis, at the subventricular zone, was also apparent. Tissue hyperoxia decreased the rate of vasculogenic cell division but had no apparent effect on neurogenic or astrocytic cell division. Four distinct zones of cell generation were therefore identified within the retina, each associated with either glial, vascular, or neuronal cytogenesis. Thus, BrdU immunohistochemistry in whole-mounted retinal preparations offers a fast and reliable alternative to [3H]thymidine autoradiography for the study of the topography of cytogenesis during development.