Evaluation of Systemic Microvascular Endothelial Dysfunction in Patients Presenting With Infective Endocarditis

Overview

Infective endocarditis (IE) is a severe clinical condition with a high in-hospital and 5-year mortality. It has a growing incidence, both related to healthcare and possibly to changes in prophylaxis recommendations regarding oral procedures. Though not a new disease, several aspects in its clinical and laboratory diagnosis remain to be better studied and innovated. The evaluation of systemic microvascular disease has proven crucial in the investigation and comprehension of pathophysiology of cardiovascular diseases, as well as a tool for early diagnosis and prediction of complications. Few studies deal with microcirculation in patients with IE, and so far none utilizing speckle contrast imaging and functional capillary density. The present study will contribute to the investigation of microcirculatory changes in IE and possibly to earlier diagnosis of the condition and/or of its severity and complications. The aim of the study is to evaluate the changes in microvascular bed of patients with both acute and subacute endocarditis by speckle contrast imaging and skin video-capillaroscopy.

This is a cohort study that will include adult patients with active definite infective endocarditis by the modified Duke criteria admitted to our center for treatment. A control group of healthy volunteers, paired by sex and age, will be included. The microcirculatory tests will be performed in an undisturbed quiet room with a defined stable temperature (23 ± 1 °C) after a 20-minute rest in the supine position. Functional capillary density (FCD) defined as the number of spontaneously perfused capillaries per square millimeter of skin area will be assessed by video-microscopy system with an epi-illuminated fiber-optic microscope containing a 100-W mercury vapor lamp light source and an M200 objective with a final magnification of 200×. Images will be acquired and saved for posterior off-line analysis using a semi-automatic integrated system (Micro-vision Instruments, Evry, France). The mean capillary density for each patient will be calculated as the arithmetic mean of visible (i.e., spontaneously perfused) capillaries in three contiguous microscopic fields of 1mm2 each. Capillary recruitment (capillary reserve) will be evaluated using post-occlusive reactive hyperemia (PORH) after arm ischemia for 3 min. Microvascular reactivity will be evaluated using an laser speckle contrast imaging (LSCI) system with a laser wavelength of 785 nm (PeriCam PSI system, Perimed, Sweden) in combination with iontophoresis of acetylcholine (ACh), as an endothelium dependent substance, and nitroprusside (endothelium independent) for noninvasive and continuous measurement of cutaneous microvascular perfusion changes (in arbitrary perfusion units, APU).