Markus Rothenburger

Echocardiographic assessment of global left ventricular function in mice

Doppler-echocardiographic assessment of cardiovascular structure and function in murine models has developed into one of the most commonly used non-invasive techniques during the last decades. Recent technical improvements even expanded the possibilities. In this review, we summarize the current options to assess global left ventricular (LV) function in mice using echocardiographic techniques. In detail, standard techniques as structural and functional assessment of the cardiovascular phenotype using one-dimensional M-mode echocardiography, two-dimensional B-mode echocardiography and spectral Doppler signals from mitral inflow respective aortal outflow are presented. Further pros and contras of recently implemented techniques as three-dimensional echocardiography and strain and strain rate measurements are discussed. Deduced measures of LV function as the myocardial performance index according to Tei, estimation of the mean velocity of circumferential fibre shortening, LV wall stress and different algorithms to estimate the LV mass are described in detail. Last but not least, specific features and limitations of murine echocardiography are presented. Future perspectives in respect to new examination techniques like targeted molecular imaging with advanced ultrasound contrast bubbles or improvement of equipment like new generation matrix transducers for murine echocardiography are discussed.

CYTOKINE RESPONSE TO INFECTION IN PATIENTS WITH ACUTE MYELOGENOUS LEUKAEMIA FOLLOWING INTENSIVE CHEMOTHERAPY

Summary. Septic shock is the major cause of treatmentrelated death in patients with acute myelogenous leukaemia (AML) undergoing intensive chemotheray. Interleukins (IL)‐1β, −6, −8, and tumour nerosis factor α (TNF‐α) have been implicated as mediators of septic shock, with circulating leucocytes being considered a major source for their release. However, Plasma cytokine levels of leucocytopnic patients with evolving sepsis have not been studied. We have prospectively measured plasma cytokines during chemotherapy‐induced leucocytopenia (< 1 × 109/1) in 50 patiens with AML. Cytokine levels in patients with severe sepsis (n=5) or septic shock (n=8) were cmpared to those measured in 13 matched patients with uncmplicated febrile infections. In evolving septic shock, IL‐6, IL‐8 and TNF‐α peaked within 48 h of fever onset at levels reported for nonleucocytopenic patients and distinctively higher than during uncomplicated febrile episodes (P < 0.05). Peak concentrations measured within 48 h after onset of fever were related to fatal outcome. IL‐1β was detected in less than 5% of all samples. Cytokine concentrations were unrelated to leucocyte counts and markers of neopterphil or monocyte activation (elastase and neeopterin levels, respectively). We conclude that cytokine release associated with evolving septic shock in patients with AML does not depend on circulating leucocytes.

Tissue engineering of heart valves: formation of a three-dimensional tissue using porcine heart valve cells.

Tissue engineering is a promising approach to obtaining lifetime durability of heart valves. The goal of this study was to develop a heart valve-like tissue and to compare the ultrastructure with normal valves. Myofibroblasts and endothelial cells were seeded on a type I collagen scaffold. The histologic organization and extracellular matrix were compared in light and electron micrographs. Radiolabeled proteoglycans were characterized by enzymatic degradation experiments. In tissue engineered specimens, cross sectional evaluation revealed that the scaffold (300 &mgr;m) was consistently infiltrated with myofibroblasts. Both sides were covered with a multicellular layer of myofibroblasts and overlaid by endothelial cells (50 &mgr;m). A newly formed extracellular matrix containing collagen fibrils and proteoglycans was found in the interstitial space. Collagen fibrils with a 60 nm banding pattern were found in both specimens. Small sized proteoglycans (65 nm) were associated and aligned at intervals of 60 nm with collagen fibrils. Large sized proteoglycans (180 nm) were located outside the collagen bundles in amorphous compartments of the extracellular matrix. The majority of glycosaminoglycans were chondroitin/dermatan sulfate, and a minority were heparan sulfate. The morphology and topography of cells and the organization of extracellular matrix in artificial tissues strongly resembles those of native valve tissues.

Aortic valve replacement for aortic regurgitation and stenosis, in patients with severe left ventricular dysfunction.

OBJECTIVE Aortic valve replacement for aortic valve stenosis (AS) and regurgitation (AR) in patients with severe left ventricular (LV) dysfunction contains an increased risk. Few data are available on the outcome of such patients. METHODS Fifty-five consecutive patients with severe LV dysfunction (ejection fraction, EF; <30%) and aortic valve replacement for AS (n=35) or AR (n=20) were investigated between 1994 and 2001. EF was 25+/-5%, mean transvalvular gradient 26+/-6mmHg (AS), aortic valve area 0.66+/-0.18cm(2) (AS), cardiac index (CI) 2.4+/-0.9l/min/m(2), enddiastolic LV diameter (LVEDD) 64+/-8mm and endsystolic LV diameters (LVESD) was 55+/-3mm. Ninety percent of patients were in New York Heart Association (NYHA) functional class III/IV at admission to the hospital. Concomitant coronary artery bypass grafts (CABG) were performed in 14 patients. Follow-up examinations including chest X-ray, echocardiography, exercise testing, were performed among survivors. RESULTS The survival rates for AS were: 1-year 76%, 2-year 68.8%, 5-year 64.2%; for AR: 1-year 94.4%, 2-year 86.5%, 5-year 74.2%. NYHA functional class improved from 90% in class III/IV to 45 (AR group) and 24% (AS group) at follow-up (P<0.02). The LVEDD decreased to 54+/-8mm after 1 year. The EF improved to 38+/-4 (AR group) and 40+/-5% (AS group) at follow-up. CONCLUSIONS Despite severe LV dysfunction, increased 1-year mortality especially in the AS group, aortic valve replacement was associated with improved functional status, symptoms and EF in both groups and in most patients. We, therefore, conclude that aortic valve replacement in patients with severe LV dysfunction can be performed with acceptable risk.

Ultrastructure of Proteoglycans in Tissue-Engineered Cardiovascular Structures

Proteoglycans such as versican, decorin, and perlecan are important components of the extracellular matrix in various tissues. They play an important role in water homeostasis, tissue elasticity, prevention of calcification, and thrombogenicity. The aim of our study was to detect such proteoglycans in engineered tissue and compare them with the proteoglycans of native porcine heart valves. Myofibroblasts were seeded on a type I collagen scaffold. Thereafter, endothelial cells were seeded onto the presettled myofibroblasts. The newly formed tissue was histologically and immunohistochemically examined. Cupromeronic blue was used for ultracytochemical staining of proteoglycans. Radiolabeled proteoglycans were isolated by ion-exchange chromatography and characterized by enzymatic degradation. Three differently sized proteoglycan precipitates were found. The large-sized proteoglycan (154 nm) was located outside the collagen bundles in a rarely structured extracellular matrix compound. The small-sized proteoglycan (46 nm) was aligned along the collagen bundles at intervals of 60 nm. The intermediate-sized proteoglycan (56 nm) was detected on the cell surface of myofibroblasts. The glycosaminoglycans included 80% chondroitin and dermatan sulfate and 20% heparan sulfate. We conclude that proteoglycans play an important role in the functional integrity of cardiovascular tissues. This study shows the successful production of a heart valve-like tissue with proteoglycans resembling, in terms of type, production, and distribution, proteoglycans of native heart valves.

The effect of high thoracic epidural anesthesia on systolic and diastolic left ventricular function in patients with coronary artery disease.

In patients with coronary artery disease, vasoconstriction is induced through activation of the sympathetic nervous system. Both α1- and α2-adrenergic epicardial and microvascular constriction are potent initiators of myocardial ischemia. Attenuation of ischemia has been observed when sympathetic nervous system activity is inhibited by high thoracic epidural anesthesia (HTEA). However, it is still a matter of controversy whether establishing HTEA may correspondingly translate into an improvement of left ventricular (LV) function. To clarify this issue, LV function was quantified serially before and after HTEA using a new combined systolic/diastolic variable of global LV function (myocardial performance index [MPI]) and additional variables that more specifically address systolic (e.g., fractional area change) or diastolic function (e.g., intraventricular flow propagation velocity [Vp]). High thoracic epidural catheters were inserted in 37 patients scheduled for coronary artery surgery, and HTEA was administered in the awake patients. Echocardiographic and hemodynamic measures were recorded before and after institution of HTEA. HTEA induced a significant improvement in diastolic LV function (e.g., Vp changed from 45.1 ± 16.1 to 53.8 ± 18.8 cm/s; P < 0.001), whereas indices of systolic function did not change. The change in the diastolic characteristics caused the MPI to improve from 0.51 ± 0.13 to 0.35 ± 0.13 (P < 0.001). We conclude that an improvement in cardiac function was due to improved diastolic characteristics.

The impact of anti-endotoxin core antibodies on endotoxin and cytokine release and ventilation time after cardiac surgery☆

OBJECTIVES We hypothesized that a temporary cardiopulmonary bypass (CPB)-induced reduction of endotoxin antibody levels contributes to elevated endotoxin levels and the associated inflammatory consequences, with a significant influence on the postoperative ventilation time period. BACKGROUND Cardiac surgery using CPB induces a systemic inflammatory response syndrome with an associated risk of increased postoperative morbidity and mortality. METHODS A total of 100 consecutive patients undergoing elective coronary artery bypass graft surgery using CPB were prospectively investigated. Endotoxin core antibodies (immunoglobulin [Ig] M/IgG against lipid A and lipopolysaccharide), endotoxin, interleukin (IL)-1-beta, IL-6, IL-8 and tumor necrosis factor-alpha were measured serially from 24 h preoperatively until 72 h postoperatively. RESULTS Eighty-five patients had no complications (group 1), whereas 15 patients required prolonged ventilation (group 2). In both groups, there was a decrease of all antibodies 5 min after CPB onset, compared with baseline values (p < 0.001), an increase of endotoxin and IL-8 peaking at 30 min postoperatively (p < 0.001) and an increase of IL-6 peaking 3 h postoperatively (p < 0.001). In group 2, preoperative antibody levels were lower (p < 0.01)--specifically, the decrease in IgM was significantly stronger and of longer duration (p < 0.002)--and levels of endotoxin (p < 0.001) and IL-8 (p < 0.001) were higher at 30 min postoperatively. CONCLUSIONS We conclude that an CPB-associated temporary reduction of anti-endotoxin core antibody levels contributes to elevated endotoxin and IL-8 release. Furthermore, lower levels of IgM anti-endotoxin core antibodies were associated with a greater rise in endotoxin and IL-8, as well as prolonged respirator dependence.

Skeletonization Versus Pedicle Preparation of the Radial Artery With and Without the Ultrasonic Scalpel

BACKGROUND The radial artery (RA) is increasingly used for myocardial revascularization because of its presumed advantageous long-term patency rates. The vessel can be harvested as a pedicle or skeletonized. The aim of this study was to compare the skeletonization technique with pedicle preparation using either an ultrasonic scalpel or scissors. METHODS Forty consecutive patients with coronary artery disease undergoing complete arterial revascularization were included in the study. In 20 patients the RAs were prepared using scissors and clips (group 1: skeletonization; group 2: pedicle). In another 20 patients the arteries harvested were prepared using an ultrasonic scalpel (group 3: skeletonization; group 4: pedicle). The RA was treated with papaverine to prevent spasm of the vessel during and after harvesting. Tissue specimens of each RA were taken to analyze endothelial morphology by scanning electron microscopy. After implantation of the RA, graft perfusion was measured with a flow probe. RESULTS Harvesting the RA as a skeletonized vessel took more time as compared with pedicle preparation (group 1 vs group 2: 37.1 +/- 3.5 minutes vs 24.4 +/- 3.9 minutes; p < 0.001 and group 3 vs group 4: 31.1 +/- 3.5 minutes vs 25.6 +/- 3.7 minutes; p < 0.01). The number of hemostatic titanium clips was similarly higher in group 1 as opposed to group 2 (58.7 +/- 7.1 vs 38.7 +/- 7.1; p < 0.01). However, there was no difference between groups 3 and 4 (p = 0.086). The length of the RA after skeletonization with scissors and clips was 20.8 +/- 1.5 cm in contrast with 19.1 +/- 0.9 cm (p < 0.01) after dissection as a pedicle. In the groups using the ultrasonic scalpel, there was no difference in graft length (p = 0.062). Mean blood flow through the graft after establishing the proximal anastomosis was similar among all groups (groups 1, 2, 3, and 4: 50 +/- 20.1 mL/min, 53.8 +/- 24.3 mL/min, 56.3 +/- 25.1 mL/min, and 51.8 +/- 23 mL/min, respectively). Scanning electron microscopy demonstrated endothelial damage in all patients in groups 1, 2, and 3 and in 7 patients of group 4. Most endothelial lesions were minor except in group 3 in which 1 of 5 endothelial lesions were severe. Statistically significant differences was found between groups 1 and 2, and 3 and 4 with respect to the degree of endothelial damage (p < 0.01). CONCLUSIONS Skeletonization using scissors and clips is more time consuming and technically more difficult, but yield significantly longer grafts. Skeletonization with an ultrasonic scalpel did not result in additional length and was more frequently associated with severe endothelial damage. Pedicle preparation using scissors or an ultrasonic scalpel is much simpler and faster, and does not jeopardize endothelial integrity.

Pyodera gangrenosum after aortic valve replacement

A 68-year-old male patient developed pyoderma gangrenosum after elective aortic valve replacement. Treatment with steroids and clofazimine was initiated, which resulted in rapid cessation of the necrotic process. Due to thoracic instability, stabilization of the sternum was performed followed by surgical debridement and atraumatic wound closure. Postoperatively, immunosuppression with cyclosporine A was added; the patient recovered completely. Pyoderma gangrenosum is a potential life-threatening complication that must be considered in patients with severely impaired wound healing after cardiac operation.

Effect of high dose platelet inhibitor treatment on thromboembolism in Novacor patients

BACKGROUND Thromboembolism and bleeding are among the most hazardous complications following implantation of long-term left ventricular support systems. This report focuses on the effect of high dose platelet inhibitor treatment in patients with the Novacor system to prevent thromboembolic events. METHODS Thirty-eight (out of 58) Novacor patients (43+/-11 years old) were studied in a non-randomized manner. Postimplantation: 20 patients were treated with heparin only (control group), whereas in the other 18 patients aspirin (3x330 mg/day) and dipyridamol (3x75 mg/day) were added to the treatment protocol (aspirin group). RESULTS Age, body size, underlying heart disease and support interval were comparable among both groups, however, patients in the aspirin group were much sicker with regard to urgency status, postoperative right heart failure and hematologic disorders. Cerebral thromboembolic complications were lower in the aspirin group (33% of patients, 0.4+/-0.7 events) as compared to the control group (55% (P=0.18), 1.4+/-2.3 events (P=0. 048)). Non-cerebral thromboembolism of surgical relevance was rare. The incidence of bleeding complications was mildly increased in the aspirin group. CONCLUSION The addition of high dose platelet inhibitors seems to lower the incidence of thromboembolism in Novacor patients.