[Minimally invasive video-assisted operations for heart disease]. / Miniinvazivní videoasistované operace srdecních vad.

INTRODUCTION: Minimally invasive surgical access for the treatment of mitral and tricuspid valves has become an alternative method to the conventional approach via median sternotomy. The aim of this paper is to evaluate our experience and results with minimally invasive approach in cardiac surgery at our institution. MATERIAL AND METHODS: A total of 52 patients underwent minimally invasive cardiac surgery between November 2011 and March 2013. Right lateral minithoracotomy and femoral vessels cannulation for cardiopulmonary bypass was used. Follow-up data was collected in a prospective database and analysed retrospectively. RESULTS: The mean age of patients was 60.9 ± 11.6 years (female patients accounted for 63.5%). The procedures performed included mitral valve repair in 44 (85%) patients and tricuspid valve repair in 25 (48%). Atrial septal defect closure was performed in 8 (15%) patients and cryoablation of atrial fibrillation in 26 (50%) patients. There were 75% combined procedures. The median duration of the operation was 235 (155-315) minutes. The median length of cardiopulmonary bypass and crossclamp time was 139 (89-225) and 92 (51-168) minutes, respectively. The median duration of postoperative hospital stay was 12.5 (6-34) days. Hospital and 30-day mortality was 0%. At follow-up (121.3 ± 32.72 days), two patients (3.8%) required reoperation (1 for right haemothorax, 1 for aortic valve insufficiency). CONCLUSION: Minimally invasive access has been adopted as a routine method for the therapy of valve disease. The minithoracotomy approach is a safe and feasible technique with comparable mortality and in-hospital morbidity.

Noninvasive assessment of the iridial microcirculation in rats using sidestream dark field imaging.

Sidestream dark field imaging represents a novel, noninvasive method to study the microcirculation in humans and animals. To-date, it has been used extensively in various peripheral tissues (e.g. sublingual area, intestinal mucosa), however no data for the ocular vasculature, including the iridial microcirculation, are currently available. Therefore, the aim of this study was to examine the reliability and reproducibility of sidestream dark field imaging within the iridial microcirculation in experimental animals. Male Lewis rats were anaesthetized and the iris microvasculature was observed using an sidestream dark field probe gently placed against a cover slip covering the right eye. All video sequences recorded were analysed off-line by using AVA 3.0 software (MicroVision Medical, Amsterdam, The Netherlands). Results are expressed as mean (±SE) or median (interquartile range). Clear images were recorded from each animal and the total number of analysable video sequences was 50. All raw data for selected vessel density parameters passed normality test. The total all and small vessel density (in mm mm(-2) ) were 22,6 (±0,58) and 19,6 (±0,68), respectively. The perfused all and small vessel density were 20,9 (±0,61) and 19,1 (±0,65), respectively. The mean values of all iris vessel density parameters are shown in Figure 4. The DeBacker Score (n/mm) was 15,2 (±0,45), the proportion of perfused vessel was 94,5% (89,8-99,1%), and the MFI was 3 points (3-3). Taken together, these results indicate that SDF imaging provides a reliable and noninvasive method to examine the iridial microvascular bed in vivo and, thus, may provide unique opportunities for the study of the iridial vascular network in various experimental and clinical settings and disease models.

In situ assessment of the brain microcirculation in mechanically-ventilated rabbits using sidestream dark-field (SDF) imaging.

Assessment of the cerebral microcirculation by on-line visualization has been impossible for a long time. Sidestream dark-field (SDF) imaging is a relatively new method allowing direct visualization of cerebral surface layer microcirculation using hand-held probe for direct contact with target tissue. The aim of this study was to elucidate the feasibility of studying the cerebral microcirculation in situ by SDF imaging and to assess the basic cerebral microcirculatory parameters in mechanically ventilated rabbits. Images were obtained using SDF imaging from the surface of the brain via craniotomy. Clear high contrast SDF images were successfully obtained. Total small-vessel density was 14.6+/-1.8 mm/mm(2), total all-vessel density was 17.9+/-1.7 mm/mm(2), DeBacker score was 12.0+/-1.6 mm(-1) and microvascular flow index was 3.0+/-0.0. This method seems to be applicable in animal studies with possibility to use SDF imaging also intraoperatively, providing unique opportunity to study cerebral microcirculation during various experimental and clinical settings.

In situ assessment of the liver microcirculation in mechanically ventilated rats using sidestream dark-field imaging.

Assessment of hepatic microcirculation by on-line visualization has been impossible for a long time. Sidestream dark-field (SDF) imaging is a relatively new method allowing direct visualization of both mucosal microcirculation and surface layers microcirculation of solid organs using hand-held probe for direct contact with target tissue. The aim of this study was to evaluate the feasibility of studying the rat hepatic microcirculation in situ by SDF imaging. The liver lobes were left in situ, and images were obtained using SDF imaging on the surface of the liver via upper midline laparotomy. Images were captured intermittently during 10-sec apnoea and recorded. The microvascular parameters were compared with previous validation studies. Clear high contrast SDF images were successfully obtained. Quantitative analysis revealed a mean FSD (functional sinusoidal density) of 402+/-15 cm/cm(2), a sinusoidal diameter of 10.2+/-0.5 microm and postsinusoidal venular diameter of 33.9+/-13 microm. SDF imaging is a suitable noninvasive method for accurate quantification of the basic microcirculatory parameters of the liver in situ without a need to exteriorize the liver lobes. This method seems to be applicable in animal studies with possibility to use SDF imaging also intraoperatively, providing unique opportunity to study liver microcirculation during various experimental and clinical settings.

Noninvasive in vivo assessment of the skeletal muscle and small intestine serous surface microcirculation in rat: sidestream dark-field (SDF) imaging.

The pathophysiology of microcirculation is intensively investigated to understand disease development at the microscopic level. Orthogonal polarization spectral (OPS) imaging and its successor sidestream dark-field (SDF) imaging are relatively new noninvasive optical techniques allowing direct visualization of microcirculation in both clinical and experimental studies. The goal of this experimental study was to describe basic microcirculatory parameters of skeletal muscle and ileal serous surface microcirculation in the rat using SDF imaging and to standardize the technical aspects of the protocol. Interindividual variability in functional capillary density (FCD) and small vessels (<25 microm in diameter) proportion was determined in anesthetized rats on the surface of quadriceps femoris (m. rectus femoris and m. vastus medialis) and serous surface of ileum. Special custom made flexible arm was used to fix the SDF probe minimizing the pressure movement artifacts. Clear high contrast images were analyzed off-line. The mean FCD obtained from the surface of skeletal muscle and ileal serous surface was 219 (213-225 cm/cm(2)) and 290 (282-298 cm/cm(2)) respectively. There was no statistically significant difference between rats in mean values of FCD obtained from the muscle (P = 0.273) in contrast to ileal serous surface, where such difference was statistically significant (P = 0.036). No statistically significant differences in small vessels percentage was detected on either the muscle surface (P = 0.739) or on ileal serous surface (P = 0.659). Our study has shown that interindividual variability of basic microcirculatory parameters in rat skeletal muscle and ileum is acceptable when using SDF imaging technique according to a highly standardized protocol and with appropriate fixation device. SDF imaging represents promising technology for experimental and clinical studies.

Orthogonal polarization spectral imaging.

The microcirculation plays a crucial role in the interaction between blood and tissues both in physiological and pathophysiological states. Despite its critical role in numerous diseases including diabetes, hypertension, sepsis or multiple organ failure, methods for direct visualization and quantitative assessment of human microcirculation at the bedside are limited. Orthogonal polarization spectral (OPS) imaging is a relatively new noninvasive method for assessment of human microcirculation without using fluorescent dyes. Recent clinical studies using OPS imaging in various pathological states have shown a wide spectrum of different clinical applications with evident impact on the diagnosis, treatment or prognosis assessment. Thus, there is a great effort to validate OPS imaging for various clinical purposes. The principles of OPS imaging, validation studies, its advantages, limitations, methods of quantitative assessment and current experience in clinical practice are discussed.

Effect of nifedipine on coronary capillary geometry in normotensive and hypertensive rats.

The aim of this study was to describe quantitatively changes in the coronary capillary network resulting from hypertrophy in spontaneously hypertensive rats (SHR) and a potential effect of long-term treatment of these animals with nifedipine. Age-matched male SHR and Wistar-Kyoto (WKY) rats were treated for 27 weeks. Four experimental groups were analyzed: (1) untreated SHR, (2) nifedipine-treated SHR, (3) untreated control WKY rats, and (4) nifedipine-treated WKY rats. Treatment significantly decreased systolic blood pressure in SHR, although normotensive pressures were not reached. SHR had significantly higher cardiac weight, which decreased in nifedipine-treated rats, but values remained above those in control animals. Morphometric evaluation revealed lower capillary density and larger capillary domain area in hearts from SHR, which were partially attenuated by treatment with nifedipine. Capillary domain area was also significantly larger at arteriolar portions compared with domains supplied at venular portions. Capillary segment length was consistently shorter on the venular than arteriolar portion of the capillary, whereas no differences were observed between hearts from WKY rats and SHR. Treatment with nifedipine resulted in a prolongation of segment length. Reconstruction of the three-dimensional capillary supply unit (capillary domain area times capillary segment length) revealed significant differences between the amount of tissue supplied by a capillary at its arteriolar portion than more distally, which was detectable in all experimental groups. In hypertrophic hearts from SHR this tissue volume is increased mainly because of longer intercapillary distances and larger domains, especially on arteriolar portions.(ABSTRACT TRUNCATED AT 250 WORDS)

Local plasma convection can be important for oxygen release in tissue capillaries.

Aroesty and Gross investigated the effect of mixing in gaps between two successive RBCs on the local mass transfer at the capillary wall. They found that the effect was insignificant. In this presentation it is shown that their conclusion results from their choice of boundary conditions. When boundary concentrations are chosen which are more similar to those in diffusional models the flux at the capillary wall increases significantly when mixing increases. The calculations presented indicate that mixing of plasma may enhance oxygen transport, although it is impossible to assess the physiological importance. To be able to investigate that, a model has to be developed that includes oxygen transport in both the RBCs and tissue, the oxygen release in the RBCs, and the oxygen consumption in the tissue.

Capillarisation and fibre types in hypertrophied m. plantaris in rats of various ages.

Influences of age, overload obtained through denervation of synergists, and training on the capillarisation of the m. plantaris were compared in 5-, 13- and 25-month-old rats in relation to different fibre types. Overload resulted in about 30% hypertrophy in each age group. Age effects were significant only in the deep (more oxidative) region of the muscle. From 5 to 13 months, the percentage of FOG fibres increased at the expense of FG fibres, while the fibre cross-sectional areas (FCSA) of each fibre type increased. From 13 to 25 months, the FCSA of FG fibres decreased, as did the local capillary-to-fibre ratio (LCFR) of each fibre type, indicating capillary loss and a declined capillary density for each fibre type (CFD). Overload effects were identical for both the superficial (more glycolytic) and the deep region for each age group. With overload, FCSA and LCFR of each fibre type increased, while CFD decreased, indicating that capillary proliferation occurred with overload, even at old age, although lagging behind increases in FCSAs. Training showed minor effects.

Metabolic capacity, fibre type area and capillarization of rat plantaris muscle. Effects of age, overload and training and relationship with fatigue resistance.

1. The influences of age (5, 13 and 25-month-old rats), overload as obtained by denervation of synergists, and training on the metabolic capacity, relative muscle cross-sectional area occupied by each fibre type, capillarization and fatigue resistance of the rat m. plantaris were investigated. 2. Creatine kinase, phosphorylase and citrate synthase activities were lower in muscles of 25 than in those of 13-month-old rats (P < 0.001). 3. Overload resulted in an increased relative area of type I and IIa fibres at all ages (P = 0.001). 4. Capillary density decreased with overload and increasing age (P < 0.001). 5. Fatigue resistance was higher in muscles of 13 than in those of 5-month-old rats (P < 0.05), and increased with overload (P < 0.05) at all ages. 6. Fatigue resistance of the whole muscle was not closely related to its oxidative capacity in contrast to what is generally found for single fibres or motor units.

Cardiac structural remodelling after treatment of spontaneously hypertensive rats with nifedipine or nisoldipine.

OBJECTIVE: The aim was to determine if long term treatment with nifedipine or nisoldipine affects structural remodelling of cardiac myocytes and is effective in attenuating or preventing reparative and reactive myocardial fibrosis in essential hypertension. METHODS: Five and a half month old male spontaneously hypertensive rats and Wistar Kyoto (WKY) rats received either 1000 ppm nifedipine or nisoldipine or no treatment (controls) for 22 weeks. Haemodynamic variables were measured and hearts recovered from animals of each group. Cardiac myocytes were isolated by retrograde coronary perfusion with collagenase. Cell volume was determined by Coulter analysis, cell length by direct measurement, and cross sectional area by volume/length. Cardiac myocyte number was calculated for both ventricles. Tissue sections from perfusion fixed hearts were stained with picrosirius red and myocardial collagen was analysed. Reparative fibrosis was assessed by the presence of microscopic scarring and reactive (interstitial and perivascular) fibrosis was quantified. RESULTS: Nifedipine and nisoldipine significantly decreased systolic and diastolic blood pressure in spontaneously hypertensive rats, although normotensive pressures did not result. Left ventricular weight relative to body weight was significantly decreased in nifedipine and nisoldipine treated compared with untreated spontaneously hypertensive rats, although values remained significantly greater than WKY controls. Cardiac myocyte volume was slightly decreased with attenuation of blood pressure in spontaneously hypertensive rats, but no significant differences were found. Cardiac myocyte number for each ventricle was similar between groups. Microscopic scarring was significantly decreased in nifedipine and nisoldipine treated compared with untreated spontaneously hypertensive rats and interstitial and perivascular fibrosis were substantially reduced. CONCLUSIONS: Nifedipine and nisoldipine: (a) attenuate hypertension and decrease left ventricular mass in spontaneously hypertensive rats, but the associated decrease in myocyte size was not significant; (b) are cardioprotective as indicated by a significant decrease in the incidence of microscopic scarring; and (c) decrease the extent of reactive, both interstitial and perivascular, fibrosis normally found in untreated spontaneously hypertensive rats. Nifedipine and nisoldipine have the potential to positively alter myocardial pathology in essential hypertension.

Compensatory hypertrophy and training effects on the functioning of aging rat m. plantaris.

The influence of age, compensatory hypertrophy and training on isometric contraction characteristics of rat m. plantaris were investigated in 5-, 13- and 25-month-old rats. Each age group was subdivided into Control Not Trained, Control Trained, Operated Not Trained and Operated Trained groups. Run training was applied. The Operation i.c. denervation of synergists induced a 30% compensatory hypertrophy (P < 0.001). Age and training did not significantly affect muscle weight. The tetanic force was highest in 13-month-old and lowest in 25-month-old muscles as was the tetanic force/muscle weight (P < 0.001). Trained and hypertrophied muscles had increased tetanic force (P < 0.01), but tetanic force/muscle weight was not significantly affected. Twitch contraction time was longer in hypertrophied muscles than in controls (P < 0.001). Half relaxation time decreased with training (P < 0.05). Resistance to fatigue was increased in hypertrophied muscles as compared to controls (P < 0.04) and was lower in 5-month-old than in 13-month-old muscles, but their fatigue resistance did not differ from the 25-month-old muscles. Each age group showed comparable effects of training and hypertrophy on the contraction characteristics. These results indicate that the force generating capacity of the M. plantaris was optimal in the 13-month-old animals compared to the other age groups. Furthermore, our data show that aged muscles react in a similar way to increased functional demand as muscles of younger age.

The relationship between capillarisation and fibre types during compensatory hypertrophy of the plantaris muscle in the rat.

Compensatory hypertrophy of the plantaris muscle was obtained by denervation of its synergists. This hypertrophy is characterised by a 32% increase in muscle mass. The muscle consists of type I and IIa (oxidative), and IIb (glycolytic) fibres. Fibres of all types were enlarged in hypertrophied muscles and the proportion of type I fibres was increased. We investigated the capillarisation after hypertrophy as related to fibre type. In order to obtain this information a new technique was used, capable of estimating not only the traditional overall capillary density (CD) but also an index of heterogeneity in capillary spacing (LogSD), the 'local capillary to fibre ratio' (LCFR), obtained separately for each muscle fibre type, and finally a capillary density for each respective fibre type, the 'capillary fibre density' (CFD). It was found in both control and hypertrophied muscles that CD was higher in the deep (few IIb fibres) than in the superficial part of the muscle (considerable number of IIb fibres). The LogSD was lower, indicating less heterogeneity, in the deep than in the superficial part of the muscle. The LCFR and CFD of each fibre type was greater in the deep than in the superficial region of both control and hypertrophied muscles. Furthermore the CFD and LCFR were larger in type I and IIa fibres than in IIb fibres in each region of control and hypertrophied muscles. In hypertrophied muscles the CD was not significantly different from that of control muscles. However, LCFR of all fibre types was increased significantly in hypertrophied muscles as compared with controls, demonstrating capillary proliferation. The decreased CFD of type I and IIa fibres in the deep region of hypertrophied muscles as compared with controls suggests that here the capillary proliferation lags behind the increase in muscle mass. Endurance training had no significant effects for any region in any of the indices that were used.