Continuous blood pressure monitoring utilizing a CMOS tactile sensor

A novel tactile device based on a monolithically integrated sensor chip is presented for external blood pressure measurement. It uses a tonometric principle, thus allowing for continuous monitoring of the blood pressure without the need for an invasive catheter. On the chip, the deflection of membranes in an array is sensed capacitively and read out using a SigmaDelta-modulator. The membrane array and the modulator are fabricated on a single chip using an industrial CMOS (complementary metal oxide semiconductor) technology combined with post-process micromachining to achieve small and portable devices with low power consumption. The tested device is operated at a conversion rate of 1 kilosamples per second and is pressure biased to a 2000 hPa (1500 mmHg) reference point. The power consumption of the sensor chip is 11.5 mW with signal-to-noise ratio better than 72 dB. During testing a pressure resolution of approximately 8 hPa (6 mmHg) for one digit at the output of the SigmaDelta-modulator is achieved over the range of interest continuous blood pressure monitoring using this CMOS-based tactile device is successfully demonstrated. The characteristic features of a blood pressure waveform are clearly recognizable from the acquired data.

Experiences in robotically enhanced IMA-preparation as initial step towards totally endoscopic coronary artery bypass grafting

AIM

To evaluate the feasibility of robotically enhanced preparation of internal mammary arteries (IMA).

METHOD

Via three trocars in left thoracic wall the left, right or both IMA were skeletonized under CO(2) insufflation and single lung ventilation using electrocautery.

RESULTS

In 12 months, 26 LIMA, five BIMA and one RIMA were dissected. In five patients, the procedure had to be determined (IMA injury (two), respiratory insufficiency (two), and heart penetration (one)). Mean intrathoracic pressure was 9.7+/-1.5 mmHg. Mean time for LIMA and RIMA dissection was 66.7+/-21.1 and 99.2+/-8.7 min, respectively. In 10 patients, pericardium was incised and course of LAD assessed. However, in two patients, this coronary did not correlate with LAD. Time for instrument change depended on type of tool (cautery blade: 24.9+/-13.1 s, clip applier 72.8+/-28.4 s).

CONCLUSION

Robotic dissection of IMA is reasonable. However, life-threatening complications can barely be managed due to inadequate tools and excessive time for instrument change. Incorrect determination of coronaries can result in misplaced anastomoses.

Left ventricular assist device as bridge to heart transplantation--lessons learned with the MicroMed DeBakey axial blood flow pump

OBJECTIVE

The MicroMed DeBakey left ventricular assist device (LVAD) axial blood flow pump was used as bridge to heart transplantation (HTx) in patients with terminal heart failure. The aim was to evaluate this novel mechanical circulatory support system in regard to overall outcome.

METHODS

Prospective study in 15 HTx candidates (mean age 40+/-7 years) with terminal heart failure and maximal medical treatment due to ischemic cardiomyopathy (CMP, n=5), dilated CMP (n=3), restrictive CMP (n=2), unclassified CMP (n=1), metabolic CMP (n=1), valvular CMP (n=1) and congenital CMP (n=2). All patients were implanted with a MicroMed DeBakey LVAD. A rescue procedure was necessary in eight critical patients, while seven underwent elective LVAD implantation. Procedures were performed via median sternotomy, in normotherm femoro-femoral CPB (mean duration 59+/-1 min). Oral Marcoumar (INR 2.0-3.0) and Aspirin (100 mg daily) were started as soon as possible. Patients were discharged into a specialized rehabilitation clinic from which it was possible to release them home after a few weeks.

RESULTS

Successful implantation and discharge from ICU (mean stay 10+/-7 days) was possible in 11 patients. Seven were transplanted (mean support 50.7 days) and one is awaiting HTx (support >310 days) in the comfort of his home (NYHA I). Survival was 100% among the transplanted patients. Of the seven elective implants, five, and of the eight rescue procedures three patients underwent successful HTx. Four patients died early, while three patients died late on pump support due to intracranial hemorrhage (n=2, 73 and 76 days) and chest infection (n=1, 124 days). All survivors were discharged from hospital, with significant decrease in NYHA class (mean 3.8-2.4 (n=11)). Treadmill testing showed increased exercise tolerance, from 35 to 71W (n=4). Plasma BNP values (mean 950-162 ng/l (n=4)) and pulmonary resistance (mean 316-194.5 dyne s/cm(5) (n=3)) decreased significantly during LVAD support.

CONCLUSIONS

The MicroMed DeBakey LVAD is simple to implant; outpatient treatment is safe and efficient. Patients' condition and pulmonary resistances normalize within 6 weeks, making previously considered inoperable patients amenable for HTx. HTx can be performed in low-risk situation, allowing better donor-recipient matching and improving overall outcome.

The relevance of large strains in functional tissue engineering of heart valves

BACKGROUND

Exposing the developing tissue to flow and pressure in a bioreactor has been shown to enhance tissue formation in tissue-engineered heart valves. Animal studies showed excellent functionality in these valves in the pulmonary position. However, they lack the mechanical strength for implantation in the high-pressure aortic position. Improving the in vitro conditioning protocol is an important step towards the use of these valves as aortic heart valve replacements. In this study, the relevance of large strains to improve the mechanical conditioning protocol was investigated.

METHODS

Using a newly developed device, engineered heart valve tissue was exposed to increasing cyclic strain in vitro. Tissue formation and mechanical properties were analyzed and compared to unstrained controls.

RESULTS

Straining resulted in more pronounced and organized tissue formation with superior mechanical properties over unstrained controls. Overall tissue properties improved with increasing strain levels.

CONCLUSIONS

The results demonstrate the significance of large strains in promoting tissue formation. This study may provide a methodological basis for tissue engineering of heart valves appropriate for systemic pressure applications.

Total robotic-enhanced pericardiectomy for effusive pericarditis

With the DaVinci Robot only recently in clinical use, limitations of video-assisted thoracoscopy could disappear due to Endo-Wrist features, tremor cancellation and three-dimensional view. This report describes the total endoscopic pericardiectomy successfully achieved with robotic assistance in a 50-year-old man suffering from effusive pericarditis.

Advanced training model for beating heart coronary artery surgery: the Zurich heart-trainer

OBJECTIVE

Coronary artery surgery with beating heart technique is gaining increasing popularity. However, it is a challenging technique even for well-trained cardiac surgeons. Thus, a training model for beating heart surgery was developed to increase safety and accuracy of this procedure.

METHODS

The model consists of differentially hardened polyurethane resembling mechanical properties of the human heart. The covering used in this model is a 1:1 replica of the human thoracic wall with optionally embedded skeletal structures. Sternotomy, lateral thoracotomy or trocar placement is possible to access the lungs, the pericardium and the heart with adjacent vessels. Disposable artificial coronaries variable in size, wall quality or wall thickness are embedded in the synthetic myocardium. Two-layer vessels, which can simulate dissection, are available. Bypass conduits utilize the same material. Coronaries/bypasses as well as part of the ascending aorta are water-tight and can be rinsed with saline. Lungs can be inflated. A purpose-built pump induces heart movement with adjustable or randomized stroke volume, heart rate and arrhythmia induction.

RESULTS

The model was tested in a recent 'Wet-Lab' course attended by 30 surgeons. All conventional instruments and stabilizers with standard techniques can be used. Training with beating or non-beating heart was possible. Time needed for an anastomosis was similar to clinical experience. Each artificial tissue showed its individual nature-like qualities. Various degrees of difficulty can be selected, according to stroke volume, heart rate, arrhythmia, vessel size and vessel quality. The model can be quickly and easily set up and is fully reusable.

CONCLUSIONS

The similarity to human tissue and the easy set-up make this completely artificial model an ideal teaching tool to increase the confidence of cardiac surgeons dealing with beating heart and minimally invasive surgery.

Endoscopic saphenous vein harvesting for CABG -- a randomized, prospective trial

BACKGROUND

The saphenous vein is an established conduit for coronary revascularization. Disadvantages of traditional harvest technique are significant pain and morbidity. We compared the endoscopic harvest technique with the traditional method.

METHOD

140 coronary artery bypass graft (CABG) patients were randomized into 2 groups: endoscopic vein harvesting (EVH; n = 80) and traditional open vein harvesting (OVH; n = 60). Analysis included preoperative risk factors for wound complication, harvesting time, graft injury, and intraoperative and postoperative complications. Patient follow-up lasted 3 months.

RESULTS

The preoperative risk profiles of the groups were comparable. In the EVH group, 5 patients (7.1 %) had to be switched to the open technique. EVH time was 45 +/- 6.2 min vs. 31.1 +/- 6.5 min. Two patients (2.5 %) had to be revised because of bleeding complication vs. 6 (10 %) in the OVH group. No local infections or wound complications were observed in the EVH group vs. 11 (18 %) cases in the OVH group. Two OVH cases (3.6 %) were readmitted for wound debridement. All EVH patients reported less pain and were completely satisfied by the cosmetic results.

CONCLUSION

EVH is a safe and efficient technique for CABG. Morbidity was significantly lower, with reduced pain and better cosmetic results. EVH time was significantly longer compared to the traditional harvesting technique.

Preoperative administration of steroids: influence on adhesion molecules and cytokines after cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass (CPB) is associated with tissue damage mediated by adhesion molecules and cytokines. Prebypass steroid administration may modulate the inflammatory response, resulting in improved postoperative recovery.

METHODS

Fifty patients undergoing elective coronary operations under normothermic CPB were randomized into two groups: group A (n = 24) received intravenous methylprednisolone (10 mg/kg) 4 hours preoperatively, and group B (n = 26) served as controls. Cytokines (tumor necrosis factor-alpha [TNF-alpha], interleukin-2R [IL-2R], IL-6, IL-8), soluble adhesion molecules (sE-selectin, sICAM-1), C-reactive protein, and leukocytes were measured before steroid application, then 24 and 48 hours, and 6 days postoperatively. Adhesion molecules were measured by enzyme-linked immunosorbent assay, cytokines by chemiluminescent immunoassay. Postoperatively, hemodynamic measurements, inotropic agent requirements, blood loss, duration of mechanical ventilation, and intensive care unit stay were compared.

RESULTS

Aortic cross-clamp and CPB time was similar in both groups. Prednisolone administration reduced postoperative levels of IL-6 (611 versus 92.7 pg/mL; p = 0.003), TNF-alpha (24.4 versus 11.0 pg/L, p = 0.02), and E-selectin (327 versus 107 ng/mL, p = 0.02). Postoperative recovery did not differ between groups.

CONCLUSIONS

Preoperative administration of methylprednisolone blunted the increase of IL-6, TNF-alpha, and E-selectin levels after CPB but had no measurable effect on postoperative recovery.

Genetic predisposition in patients undergoing cardiopulmonary bypass surgery is associated with an increase of inflammatory cytokines

OBJECTIVE

Cardiopulmonary bypass (CPB) surgery induces a transient rise in pro-inflammatory cytokines typically released by activated monocytes. The E4 variant of apolipoprotein E is a recognized risk factor for atherosclerosis. It has recently been shown that apolipoprotein E affects monocyte functions in vitro and leads to higher levels of median lipoprotein (a) in humans. The aim of the study is to investigate if the E4 genetic variant of apolipoprotein E affects cytokine release after CPB surgery.

METHODS

22 patients were operated on with standard coronary artery bypass grafting. Concentrations of interleukin 8 (IL-8) and tumor necrosis factor (TNF-alpha) were measured by automated Immulite immunoassay at regular intervals within 48 h after surgery. Total apparent cytokine outputs were calculated as area under the curve. Results are expressed as mean+/-standard deviation and compared by unpaired t-test.

RESULTS

In the presented patient population 6 (27%) carried the E4 allele. Sixteen (63%) showed no E4 allele. Mean cross clamp time (CCT) was 56.2+/-13.5 min versus 55.7+/-12.1 min and CPB time was 91.8+/-17.5 versus 93.5+/-15.7 min. No statistical difference between E4-carriers and E4 non-carriers regarding CCT and CPB was observed. The total amount of IL-8 and TNF-alpha was higher in patients carrying the E4 genetic variant of apolipoprotein E in comparison to E4 non-carriers (P<0.08, P<0.039).

CONCLUSION

The presence of the E4 allele is associated with increased release of IL-8 and TNF-alpha after CBP surgery. The preoperative determination of E4 in patients undergoing cardiac surgery may lead to additional perioperative measures for the treatment of an increased systemic inflammatory response.

Heat shock protein upregulation lowers cytokine levels after ischemia and reperfusion

OBJECTIVE

Studies showed that the expression of heat shock protein 70 (HSP70) by whole-body hyperthermia or warming of the heart is associated with protection against ischemia/reperfusion injury. The aim of this study is to determine a time-related response of HSP70 expression through topical cardiac warming with correlation to cytokine production.

METHODS

30 rats were divided into three groups: no heat shock, heat shocked, and controls. Heat shock was performed with 42 degrees C saline solution applied to the heart for 5, 30, and 60 min. HSP70 and cytokines were measured.

RESULTS

Heat shock treated animals showed a 1.2-fold increase after 5 min (NS) in HSP70 expression, a 2.0-fold increase (p < 0.02) after 30 min, and a 2.3-fold increase (p < 0.012) after 60 min compared to controls. The IL-1beta levels decreased from 14.3 pg/ml (normal controls) to 7.1 pg/ml after 5 min, to 1.6 pg/ml after 30 min (p < 0.002), and to 1.4 pg/ ml after 60 min of heat shock treatment (p < 0.002). The TNF-alpha levels also decreased, but not significantly.

CONCLUSIONS

Upregulation of HSP70 through this novel method is instant and detectable within hours. The amount of HSP70 expression induced is time dependent, showing an indirect correlation with cytokine levels. These results suggest that the protective effect of HSP70 is immediate and might be explained by reduced cytokine levels. No prior recovery period is needed.

Tissue engineering of small caliber vascular grafts

OBJECTIVE

Previous tissue engineering approaches to create small caliber vascular grafts have been limited by the structural and mechanical immaturity of the constructs. This study uses a novel in vitro pulse duplicator system providing a 'biomimetic' environment during tissue formation to yield more mature, implantable vascular grafts.

METHODS

Vascular grafts (I.D. 0.5 cm) were fabricated from novel bioabsorbable polymers (polyglycolic-acid/poly-4-hydroxybutyrate) and sequentially seeded with ovine vascular myofibroblasts and endothelial cells. After 4 days static culture, the grafts (n=24) were grown in vitro in a pulse duplicator system (bioreactor) for 4, 7, 14, 21, and 28 days. Controls (n=24) were grown in static culture conditions. Analysis of the neo-tissue included histology, scanning electron microscopy (SEM), and biochemical assays (DNA for cell content, 5-hydroxyproline for collagen). Mechanical testing was performed measuring the burst pressure and the suture retention strength.

RESULTS

Histology showed viable, dense tissue in all samples. SEM demonstrated confluent smooth inner surfaces of the grafts exposed to pulsatile flow after 14 days. Biochemical analysis revealed a continuous increase of cell mass and collagen to 21 days compared to significantly lower values in the static controls. The mechanical properties of the pulsed vascular grafts comprised supra-physiological burst strength and suture retention strength appropriate for surgical implantation.

CONCLUSIONS

This study demonstrates the feasibility of tissue engineering of viable, surgically implantable small caliber vascular grafts and the important effect of a 'biomimetic' in vitro environment on tissue maturation and extracellular matrix formation.

Expression of adhesion molecules and cytokines after coronary artery bypass grafting during normothermic and hypothermic cardiac arrest

OBJECTIVE

Cardiac surgery with cardiopulmonary bypass (CPB) results in vascular injury and tissue damage which involves leukocyte-endothelial interactions mediated by cytokines and adhesion molecules. This study was designed to demonstrate the effect of normothermic and hypothermic CPB to cytokine and soluble adhesion molecule levels in adults and to determine whether these levels correlate to the patients postoperative course.

DESIGN AND PATIENTS

In 25 patients after normothermic and in 25 patients after hypothermic coronary artery bypass grafting with cardiopulmonary bypass (CPB), blood samples for cytokine and soluble adhesion molecule analysis were taken preoperatively, 24, 36, 48 h, and 6 days postoperatively. Soluble adhesion molecules (sE-selectin, sICAM-1) were measured by ELISA and cytokines (TNF-alpha, IL-6, IL-8) by chemilumenscent-immunoassay. Clinical data were collected prospectively.

RESULTS

Postoperatively, adhesion molecule and cytokine levels were significantly elevated after CPB. Mean plasma levels of sICAM-1 was 2.4-fold higher after 6 days. Mean plasma concentration of sE-selectin peaked after 48 h with a 2-fold increase compared to normothermic conditions. In the hypothermia group sICAM-1, sE-selectin, IL-6, and IL-8 showed significantly higher levels (P<0.0057, P<0.0012, P<0.0419, P<0.0145) after 24 h compared to the normothermia group. No clinical differences were seen.

CONCLUSION

Adhesion molecules and cytokines are elevated after CPB. Patients after hypothermic CPB show significant higher sICAM-1, sE-selectin, IL-6, and IL-8 levels after 24 h compared to normothermic conditions. These results are mainly due to longer CPB and crossclamp times but do not alter the patient's postoperative course.

Fibrin gel as a three dimensional matrix in cardiovascular tissue engineering

OBJECTIVE

In tissue engineering, three-dimensional biodegradable scaffolds are generally used as a basic structure for cell anchorage, cell proliferation and cell differentiation. The currently used biodegradable scaffolds in cardiovascular tissue engineering are potentially immunogenic, they show toxic degradation and inflammatory reactions. The aim of this study is to establish a new three-dimensional cell culture system within cells achieve uniform distribution and quick tissue development and with no toxic degradation or inflammatory reactions.

METHODS

Human aortic tissue is harvested from the ascending aorta in the operation room and worked up to pure human myofibroblasts cultures. These human myofibroblasts cultures are suspended in fibrinogen solution and seeded into 6-well culture plates for cell development for 4 weeks and supplemented with different concentrations of aprotinin. Hydroxyproline assay and histological studies were performed to evaluate the tissue development in these fibrin gel structures.

RESULTS

The light microscopy and the transmission electron microscopy studies for tissue development based on the three-dimensional fibrin gel structures showed homogenous cell growth and confluent collagen production. No toxic degradation or inflammatory reactions could be detected. Furthermore, fibrin gel myofibroblasts structures dissolved within 2 days in medium without aprotinin, but medium supplemented with higher concentration of aprotinin retained the three-dimensional structure and had a higher collagen content (P<0.005) and a better tissue development.

CONCLUSIONS

A three-dimensional fibrin gel structure can serve as a useful scaffold for tissue engineering with controlled degradation, excellent seeding effects and good tissue development.

Tissue engineering in cardiovascular surgery: new approach to develop completely human autologous tissue

OBJECTIVE

In cardiovascular tissue engineering, three-dimensional scaffolds serve as physical supports and templates for cell attachment and tissue development. Currently used scaffolds are still far from ideal, they are potentially immunogenic and they show toxic degradation and inflammatory reactions. The aim of this study is to develop a new method for a three-dimensional completely autologous human tissue without using any scaffold materials.

METHODS

Human aortic tissue is harvested from the ascending aorta in the operation room and worked up to pure human myofibroblasts cultures. These human aortic myofibroblasts cultures (1.5x10(6) cells, passage 3) were seeded into 15-cm culture dishes. Cells were cultured with Dulbecco' s modified Eagle's medium supplemented with 1 mM L-ascorbic acid 2-phosphate for 4 weeks to form myofibroblast sheets. The harvested cell sheets were folded to form four-layer sheets. The folded sheets were then framed up and cultured for another 4 weeks. Tissue development was evaluated by biochemical assay and light and electron microscopy.

RESULTS

After 4 weeks of culture in ascorbic acid supplemented medium, myofibroblasts formed thin cell sheets in culture dishes. The cell sheets presented in a multi-layered pattern surrounded by extracellular matrices. Cultured for additional 4 weeks on the frames, the folded sheets further developed into more solid and flexible tissues. Light microscopy documented a structure resembling to a native tissue with confluent extracellular matrix. Under transmission electron microscope, viable cells and confluent bundles of striated mature collagen fibers were observed. Hydroxyproline assays showed significant increase of collagen content after culturing on the frames and were 80.5% of that of natural human pericardium.

CONCLUSIONS

Improved cell culture technique may render human aortic myofibroblasts to a native tissue-like structure. A three-dimensional completely autologous human tissue may be further developed on the base of this structure with no show toxic degradation or inflammatory reactions.

Modified technique for heterotopic rat heart transplantation under cardioplegic arrest

The development of microsurgical techniques offers a valuable opportunity to use small animals for experimental studies of vascularized organ transplants. Availability of inbred strains, natural resistance to infection, and economy make the rat an ideal animal model to investigate the effects of heart transplantation. The recent high interest and substantial laboratory activity with regard to posttransplantory immunological tissue reactions and apoptotic tissue processes led us to optimize transplantation technique by improving myocardial protection during ischemia and thereby minimizing adverse effects of the transplantation procedure itself. Thus the present report details the technique of heterotopic heart transplantation in rats using cardioplegic arrest.

Reoperative surgery for degenerated aortic bioprostheses: predictors for emergency surgery and reoperative mortality

OBJECTIVE

The long-term outcome of patients with aortic bioprosthetic valves could be improved by decreasing the reoperative mortality rate.

METHODS

Predictors of emergency reoperation and reoperative mortality were identified retrospectively in 172 patients who had the first bioprosthetic aortic valve replacement between 1975 and 1988 (mean age 46+/-13 years) and were subjected to replacement of the degenerated bioprostheses between 1978 and 1997 (mean age 56+/-14 years). Emergency reoperation had to be performed in 31 patients (18%).

RESULTS

The operative mortality was 5.2% (9/172), 22.6% for emergency (odds ratio 11.17; 95%-confidence limit 4.33-28.85) and 1.4% for elective replacement of the degenerated aortic bioprosthesis (P<0.0001; OR=20.3). Patients who died at reoperation had higher transvalvular gradients before the primary aortic valve replacement (P=0.007), received smaller bioprostheses at the first operation (P=0.03), had later recurrence of symptoms after the first aortic valve replacement (P=0.04), a higher pre-reoperative New York Heart Association (NYHA) class (P=0.02), and a higher incidence of coronary artery disease (P=0.001) and pulmonary artery hypertension (P=0.009). Endocarditis before the primary aortic valve replacement (P=0.004), postoperative pneumonia at the first operation (P=0.005), pulmonary hypertension (P=0.0004) acquired during the interval, later recurrence of symptoms (P=0.04) after the first operation, a lower ejection fraction at the time of reoperation (P=0.03) and acute onset of bioprosthetic regurgitation (P=0.00002) were predictors for emergency surgery. Higher transvalvular gradients at the primary aortic valve replacement (P=0. 006), coronary artery disease (P=0.003) acquired during the interval, the need for concomitant coronary artery revascularization (P=0. 001), sex (P=0.02) and size (P=0.05) and type of the bioprostheses used (P=0.007) were incremental predictors for reoperative mortality which were independent of emergency surgery.

CONCLUSIONS

Elective replacement of failed aortic bioprostheses is safe. Patients undergoing emergency reoperation have a considerably higher mortality. They can be identified by a history of native aortic valve endocarditis, higher transvalvular gradients at primary aortic valve replacement, smaller bioprostheses, and pulmonary hypertension or coronary artery disease acquired during the interval. A failing bioprosthesis must be replaced at its first sign of dysfunction.

Modified ultrafiltration lowers adhesion molecule and cytokine levels after cardiopulmonary bypass without clinical relevance in adults

OBJECTIVE

Cardiac surgery with cardiopulmonary bypass (CPB) results in expression of cytokines and adhesion molecules (AM) with subsequent inflammatory response. The purpose of the study was to evaluate the clinical impact of modified ultrafiltration (MUF) and its efficacy in reducing cytokines and AM following coronary artery bypass grafting (CABG) in adults.

METHODS

A prospective randomized study of 97 patients undergoing elective CABG was designed. Fifty patients were operated on using normothermic and 47 patients using hypothermic CPB. The normothermic group was subdivided into a group with modified ultrafiltration (n = 30) and a group without MUF (n = 20). In the hypothermic group 30 patients received MUF compared to 17 patients serving as controls. MUF was instituted after CPB for 15 min through the arterial and venous bypass circuit lines. Cytokines (IL-6, IL-8, TNF-alpha, IL-2R) and adhesion molecules (sE-selectin, sICAM-1) were measured preoperatively, pre-MUF, in the ultrafiltrate, 24 h, 48 h and 6 days after surgery by chemiluminescent enzyme immunometric assay or enzyme-linked immunosorbent assay (ELISA). Clinical parameters were collected prospectively until discharge.

RESULTS

In all patients AM and cytokines were significantly elevated after normothermic and hypothemic CPB. AM and cytokines were significantly higher in hypothermia compared to normothermia. In hypothermic CPB sE-selectin was decreased after 24 h by 37% (P < 0.0063) and by 40% (P < 0.0027) after 48 h postoperatively. ICAM-1 was reduced by 43% (P < 0.0001) after 24 h and by 60% (P < 0.0001) after 6 days. Similar results were seen in cytokines with reduction up to 60% after 24 h. Changes after 48 h were noticeable but not significant. Reduction of AM and cytokines after normothermic CPB was minimal. Neither in normothermia, nor in hypothermia has sIL-2R been effectively removed from the circulation. There were no significant differences in the clinical variables between the patients with or without MUF.

CONCLUSION

AM and cytokines are significantly elevated after hypothermic CPB compared to normothermic CPB. MUF led to a significant reduction in cytokine and AM levels after hypothermic CPB, except for IL-2R. MUF showed minimal effect in normothermia. We conclude that MUF is an efficient way to remove cytokines and AM. However, we were unable to demonstrate any significant impact of MUF in outcome of adults after elective CABG.

Affinity pump system: a new peristaltic blood pump for cardiopulmonary bypass

An in vitro study has been carried out to assess the pump performance of a new peristaltic, extracorporeal displacement pump (Affinity) for cardiopulmonary bypass. The pump system consists of a pump rotor (0-110 rpm), a pump chamber, a venous reservoir with a 5/8" connecting tube and the Affinity console. The polyurethane chamber is connected to the venous reservoir by a 5/8" tube and fills passively due to the hydrostatic pressure exhibited by the fluid height in the venous reservoir. The implementation of an occlusive segment in the pump chamber, which collapses in low filling states, should prevent significant negative pressures. An in vitro circuit was filled with bovine blood (37 degrees C, hematocrit 35%) and the pump flow was measured by an ultrasonic transit time flow probe with respect to pre-load, diameter and length of attached tubing in the venous line, pump speed (rpm) and size of the connecting tube (3/8" and 5/8"). At 108 rpm and a preload equal to 10 mmHg, the flow was 8.6 +/- 0.42 l/min for an afterload of 80 mmHg. The reduction of the inlet connector to 3/8" diminished the pump flow significantly to 5.2 +/- 0.31 l/min (p < 0.0001). The pump flow decreased linearly with respect to the length of the attached tube in the venous line and for a 2 m long 5/8" silicon tube, the rpm-optimized flow was still 6.0 +/- 0.28 l/min at a preload of 10 mmHg. In case of low filling state or too high rpm, the occlusive segment collapsed and no cavitation bubbles could be detected. Our in vitro measurements yield a nomogram for rpm-optimized blood flow with respect to the pre-load in the venous reservoir. The delivered 5/8"connecting tube facilitates optimum filling of the pump chamber for high blood flow, but limits the use of venous reservoirs to Affinity products. The pump yields a high blood flow even when long tubing in the venous line is used. This makes the pump a candidate for a ventricular assist device. In hypovolemia or high rpm, the occlusive segment collapses and no negative pressure is generated at the inflow site of the pump chamber.

Flow measurements through aortocoronary and intraluminal coronary shunts

AIMS

Temporary insertion of shunts during coronary artery bypass grafting (CABG) on the beating heart may provide the minimal flow required for adequate myocardial protection (40 to 60 ml/min). We investigated the flow as a function of the pressure head over three aortocoronary shunts and one intraluminal coronary shunt.

METHODS

The aortocoronary shunts (VS-01590 with bulb size 2, 3 and 4 mm) and the intraluminal shunt (IVS-4030, bulb size 4 mm) were perfused with 47% glycerin solution at 37 degrees C. The preload was raised in 5 mmHg steps from 35 to 80 mmHg. The afterload was set at 12 mmHg. A regression analysis of the flow on the pressure head was performed.

RESULTS

For maximal preload the flow through the aortocoronary shunts was 15.9 +/- 1.3, 46.2 +/- 2.2 and 75.4 +/- 3.3 ml/min, for the intraluminal shunt it was 76.1 +/- 3.4 ml/min. To provide a flow of 40 ml/min a preload of 70, 50 and 45 mmHg was necessary for the 3 mm and 4 mm aortocoronary shunt and the intraluminal shunt respectively. For the aortocoronary and the intraluminal shunts the beta-coefficients were 0.27, 0.66, 1.13 and 1.02 ml/(min*mmHg) respectively with all p < 0.0001.

CONCLUSIONS

For adequate pressure head the 3 mm and 4 mm aortocoronary shunt and the intraluminal shunt provide myocardial protection. In case of severe proximal coronary stenosis the intraluminal shunt will not guarantee myocardial protection and main benefit reduces to working in a bloodless field. The insertion of shunts is a cheap and simple method to optimize CABG on the beating heart.

Less invasive surgical treatment of renal cell carcinomas extending into the right heart and pulmonary arteries: surgery for renal cell carcinoma

BACKGROUND

Radical resection using deep hypothermic circulatory arrest improves the survival of patients with transvenous intracardiac tumor extension of renal cell carcinomas. A less invasive surgical approach avoiding deep hypothermia, circulatory arrest, and cross-clamping of the aorta is presented.

METHODS

Between 1987 and 1999, 12 patients (mean age 57+/-8 years) underwent resection of a renal cell carcinoma extending into the right atrium, right ventricle, or pulmonary arteries. After median sterno-laparotomy, normothermic cardiopulmonary bypass is used cannulating the ascending aorta, superior caval vein, and inferior caval vein below the renal veins. The tumor and the corresponding kidney are radically excised, including the renal vein. Tumor fragments from the inferior caval vein, the right heart, and pulmonary arteries are removed either on the fibrillating or beating heart.

RESULTS

Operative mortality was 0%. Mean cardiopulmonary bypass time was 53+/-27 minutes (median 36; range 32-110 minutes). Mean blood loss per patient was 1200 mL. Mean duration of postoperative mechanical ventilation was 36+/-12 hours (median 36; range 30-77 hours), mean intensive care stay 5.5+/-5 days (median 3; range 1-48 days), and mean duration of hospitalization 22+/-12 days (median 21; range 10-58 days). All patients were discharged home. Patients with multiple tumor manifestations outside the cardiovascular systems died within 9 months after the operation.

CONCLUSIONS

The use of normothermic cardiopulmonary bypass is a less invasive method for radical resection of renal cell carcinoma with intracardiac tumor extension. Radical resection does not improve survival in patients with multiple distant metastases.

Tissue engineering of a bioprosthetic heart valve: stimulation of extracellular matrix assessed by hydroxyproline assay

Creation of an autologous heart valve by tissue engineering offers a promising approach to cardiac surgery. Although we have demonstrated successful formation of native valve analogous tissue in vitro, hemodynamic competence remains a serious problem. The aim of this study was to optimize in vitro formation of collagen as a precondition for mechanical stability of new tissue. Human myofibroblasts were seeded on square sheets of biodegradable scaffolds (control). To stimulate collagen production, one series was cultured with L-ascorbic acid 2-phosphate. In a second series, the seeded scaffolds were subjected to tension by mounting them on a frame. After 4 weeks of culture time, the collagen content of the different series was assessed by hydroxyproline assay. Light and scanning electron microscopy were performed. Hydroxyproline content of the framed scaffolds was 10 times higher than that of the control group (p < 0.05) and 6 times higher than in the unframed scaffolds grown with ascorbic acid (p < 0.05), respectively. Scanning electron microscopy proved extensive formation of solid tissue in the framed samples. These results demonstrate that supplementation of myofibroblast cultures with ascorbic acid, especially if grown on strained scaffolds, significantly increases collagen content, which is crucial for mechanical stability. This concept is a further step toward the creation of a hemodynamically competent autologous heart valve.

Explanted cryopreserved allografts: a morphological and immunohistochemical comparison between arterial allografts and allograft heart valves from infants and adults

OBJECTIVE

Life expectancy of cryopreserved allografts implanted in infants is different from those implanted in adults. A morphological study of explanted allograft heart valves was performed to determine the mechanism of deterioration and to compare cryopreserved arterial and heart valve allografts from adult patients with those explanted from infants.

METHOD

Between 1987 and 1996, 209 cryopreserved allografts were implanted: 125 valved conduits or monocusps to reconstruct the right ventricular outflow tract in congenital heart disease, 50 allograft heart valves to treat native aortic and prosthetic aortic valve endocarditis and 34 cryopreserved arterial allografts to replace mycotic aortic aneurysms or infected aortic prosthetic grafts. Two months to 8 years after implantation, 23 heart valve allografts, 11 right-sided and 12 left-sided, and four arterial allografts had to be explanted for reasons such as degeneration, recurrent infection, aneurysm formation or rupture. Besides conventional staining, immunohistochemical detection of cell populations was performed as follows: CD45RO, CD3 and CD43 for T lymphocytes, CD20 for B lymphocytes, CD68 for macrophages, protein S100 for Langerhans-cells, vimentin for fibroblasts, alpha-actin for smooth muscle cells and factor VIII for endothelial cells.

RESULTS

Explanted cryopreserved allografts were all fibrotic, acellular, non-vital and without endothelial cells. The fibrous tissue was preserved. T lymphocytes, indicating rejection, were found in all right-sided allografts from the paediatric population, but only in 9% of left-sided valves explanted from adults and in one of the four of arterial allografts. Macrophages and Langerhans-cells were found only in right-sided allografts from paediatric patients.

CONCLUSION

Right-sided cryopreserved allografts from a paediatric population showed ongoing cellular rejection. By contrast, there was only a weak T-cell mediated rejection to adult heart valve and arterial allografts. Therefore, similar long-term results can be expected in adult arterial and heart valve allografts, whereas longevity of right-sided heart valve allograft in the paediatric age group seems endangered by cellular rejection.

Conservative treatment of the aortic root in acute type A dissection

OBJECTIVE

In acute type A dissection long-term results of conservative aortic root surgery were compared with the outcome of primary valve and/or root replacement.

METHODS

Between 1985 and 1995, 199 patients (mean age 59 years, 154 men) were operated on. The aortic root was involved in the dissection process and valve incompetence of varying degree was present without exception. Replacement of a proximal aortic segment was standard procedure in all patients. The aortic valve was preserved in 126 patients: commissural suture resuspension (12 patients), root reconstruction with GRF-glue (gelatine-resorcin-formaldehyde/glutaraldehyde-glue) (114 patients). Valve replacement was performed in 73 patients (50 composite grafts, 23 valve prostheses with separate supracoronary grafts). Preoperative risk factors (valve replacement vs. preservation): coronary artery disease (11 vs. 8%, NS), tamponade (18 vs. 17%, NS), unstable hemodynamics (22 vs. 15%, NS), renal failure (4 vs. 6%, NS), neurologic disorder (19 vs. 32%, NS).

RESULTS

The overall early mortality was 23.6% (47/199 patients) and increased after commissural suture resuspension compared with GRF-glue reconstruction (P = NS). Parameters of the early postoperative period did not differ between conservative treatment and root/valve replacement: low cardiac output, 34 versus 38% (P = NS); myocardial infarction, 10 versus 11% (P = NS); hemorrhage, 25 versus 23% (P = NS); duration of intensive care (P = NS). Survival was 61% after 8 years without difference between the two principal treatment groups (P = NS) and between the two conservative subgroups (P = NS). At 2 years, GRF-glue reconstruction had an increased freedom from reoperation on the aortic root (92 vs. 70%, P = 0.0253) and event free survival (77 vs. 41%, P = 0.0224) compared with suture resuspension. Commissural suture resuspension was an independent, significant predictor for reoperation (P = 0.0221, relative risk = 4.7130).

CONCLUSION

Surgery for acute type A dissection still carries a considerable early risk. Preservation of the aortic root is safe in the absence of Marfan or annuloaortic ectasia, but a certain incidence of reoperations on the aortic valve and the aortic root has to be accepted. Root reconstruction using GRF-glue is the method of choice and is superior to suture resuspension, with a significantly better reoperation-free and event-free survival.

Approach to the mitral valve through a right thoracotomy in potentially hazardous reoperation

BACKGROUND

Repeat sternotomy for mitral valve surgery may be hazardous in some patients. A right thoracotomy avoids the densely scarred area beneath the sternum and provides adequate in-line exposure of the mitral valve.

METHODS

Between 1994 and 1997, five patients were reoperated for a mitral valve or prosthesis dysfunction through a right thoracotomy. Indications were three second redo-mitral valve surgeries and two first redo, once in a patient with an aortic prosthesis and once in a patient with patent aortocoronary grafts. The operation was performed without clamping the ascending aorta in moderate hypothermic (four patients) or normothermia (one patient).

RESULTS

Exposure of the mitral valve for replacement (four patients) or for repair of a paraprosthetic leak (one patient) was optimal in all patients. Resumption of cardiac function occurred rapidly after repair without specific support. Postoperative course was uncomplicated. Blood loss ranged from 300 to 700 mL. Patients were discharged from 7 to 12 days postoperatively. They are in New York Heart Association (NYHA) functional Class I (four patients) and II (one patient), from 3 to 42 months postoperatively.

CONCLUSION

Right thoracotomy provides a direct "in the line of vision" access to the mitral valve. Because complete de-airing of the heart is difficult and respiratory function depressed after a right thoracotomy, this approach seems suitable when technical difficulties are expected in sternal reopening.

Hemodynamic properties of the hemopump HP14

BACKGROUND

The Hemopump HP14 is a catheter-mounted, transvalvular, left ventricular assist device intended for femoral percutaneous insertion. The pump was developed for patients with postoperative or postinterventional low cardiac output and for CABG surgery on the beating heart. Little is known about the effect of afterload and hematocrit on the pump performance.

METHODS

The influence of hematocrit and afterload on the pump flow was tested using an in vitro model filled with heparinized bovine blood. Regression analysis of the pump flow with respect to three hematocrit values (20%, 30%, 40%) and ten afterload levels (30 mmHg-120 mmHg in 10 mmHg increments) was performed for all pump speed levels (n = 7).

RESULTS

At all pump speed levels reduction of afterload and hematocrit were significant predictors for increasing pump flow (p<0.001). For hematocrit values between 40% and 20% and highest pump speed, mean pump flow at lowest afterload ranged between 2.34 and 2.53 L/min; and at highest afterload between 1.31 and 1.53 L/min. For speed level 1, afterload of 120 mmHg and hematocrit of 40% there was a maximal retrograde flow of 230+/-35 ml/min.

CONCLUSIONS

Pump performance is significantly improved by both afterload and hematocrit reduction. In the weaning phase and during the removal of the device, the pump should run at a speed level of at least three to prevent retrograde flow in the pump. Estimates for pump flow in vivo can be extrapolated from our diagrams. Our results show that the Hemopump HP14 is a valuable alternative to intra-aortic balloon counterpulsation.

Complete thromboendarterectomy of the calcified ascending aorta and aortic arch

BACKGROUND

Arteriosclerotic plaques of the ascending aorta and transverse arch increase the operative risk of cardiac operations and are strong predictors for late cerebrovascular events.

METHODS

Twenty-two patients, mean age 68 +/- 6 years (range, 55 to 77 years), with grade IV + V plaques of the ascending aorta and transverse arch underwent coronary artery bypass grafting (n = 21) and aortic valve replacement (n = 8). Cerebrovascular emboli from unknown sources were found preoperatively in 8 patients (36%). All were in sinus rhythm. Complete thromboendarterectomy of the ascending aorta and transverse arch was performed during hypothermic circulatory arrest. After 21 +/- 12 months (range, 4 to 44 months), magnetic resonance imaging and transthoracic echocardiography of endarterectomized vessels was performed.

RESULTS

There was one perioperative death (4.5%), one early (4.5%), and one late (4.7%) adverse neurologic event. Follow-up examinations revealed normal diameters of the endarterectomized aorta.

CONCLUSIONS

For patients with grade IV + V plaques, thromboendarterectomy of the ascending aorta and transverse arch can be performed with an acceptable surgical risk and a low recurrence rate for cerebrovascular events. Dilatation of the endarterectomized aorta was not observed.

Aortopulmonary window with anomalous origin of the right coronary artery

We report a case of an aortopulmonary window with a right coronary artery arising from the pulmonary trunk. This exceedingly rare anomaly with anomalous coronary artery presented without myocardial ischemia owing to the aortopulmonary window. The correct diagnosis was made by angiography and a successful surgical correction was performed.

Optimized performance of the Abiomed BVS 5000: adjustment of the pump height based on Doppler control of the flow pattern

The Abiomed BVS 5000 is an automatic volume-driven paracorporeal pulsatile assist device providing left, right or biventricular support. The paracorporeal position allows optical adjustment of filling volumes of the device, which determines the output of the system. A procedure to adjust for maximal stable flow has not yet been established. In vitro measurements have been performed to assess the flow and pressure characteristics of the Abiomed BVS 5000 by raising the preload in 5 mmHg steps before running the system. Doppler probes were placed at the inflow and outflow lines of the pump. After setting the afterload at 80 mmHg the assist device was started. Two measurements were performed to find optimal flow (based on Doppler control and optical adjustment). (1) By Doppler control a stable flow pattern was found at a preload of 25 mmHg with a mean atrial pressure of 5 mmHg and a mean flow of 5.3 +/- 0.7 l/min (mean +/- standard deviation) at the inflow and outflow sites (the console flow was 4.8 +/- 0.4 l/min with a frequency of 61.8 +/- 2.0 l/min). (2) Optical adjustment of the pump height gave rise to a preload of 35 mmHg where we recorded a maximal atrial pressure of 107 +/- 5.8 mmHg, a maximal retrograde flow of -4.3 +/- 1.2 l/min at the inflow and -1.2 +/- 0.4 l/min at the outflow site. The mean flow at the inflow and outflow sites was 5.1 +/- 0.5 l/min (the console flow was 4.6 +/- 0.3 l/min with a frequency of 59.6 +/- 2.6 Hz). At an initial afterload of 60 and 40 mmHg the system showed the same qualitative behaviour, but the results were less accurate. Optical adjustment of the pump height may result in an atrioventricular valve insufficiency with undetected retrograde flow and high atrial pressures. We conclude that a Doppler flow probe must be placed at the inflow site to guarantee maximal stable flow.

Disadvantages of local repair in acute type A aortic dissection

BACKGROUND

In acute type A dissection of the aorta, local repair with glue-aortoplasty was compared with aortic replacement.

METHODS

Between 1992 and 1996, 106 consecutive patients (mean age, 59 years; 84 men) were operated on average 14.5 hours after onset of dissection. A local repair (gelatin-resorcine-formaldehyde/glutaraldehyde glue, Trigon AG, Monchengladbach, Germany) without graft replacement was performed in 21 patients. Graft replacement and reinforcement of aortic stumps with gelatin-resorcine-formaldehyde/glutaraldehyde glue was performed in 85 patients (supracoronary graft, 68; aortic root replacement, 17).

RESULTS

Survival was 79% after 30 days and 69% after 2 years. There was no difference in early mortality (p = 0.2240) and survival (p = 0.07649). Risk factors for early mortality were preoperative shock, neurologic disorder, duration of crossclamp, and extracorporeal circulation. The rate of reoperation on the proximal aorta was 31.6% (6 of 19) after local repair and 9% (6 of 64) after aortic replacement (p = 0.0157). Local repair was a significant predictor for reoperation (p = 0.0087), with decreased reoperation-free survival (p = 0.01164). In all reinterventions (four supracoronary grafts, including two valve replacements; two composite grafts; two arch replacements) breakdown of the aortoplasty was confirmed.

CONCLUSION

Local repair has satisfactory early results but an increased incidence of reoperations due to a breakdown of the glue-aortoplasty. Indications for local repair should be restricted to high-risk patients requiring a minimal emergency surgical procedure.

Fluorescence activated cell sorting: a reliable method in tissue engineering of a bioprosthetic heart valve

BACKGROUND

Techniques of tissue engineering are used to seed human autologous cells in vitro on degradable mesh to create new functional tissue like a bioprosthetic heart valve. A precondition is subsequent seeding of native-valve-analogous pure endothelial and myofibroblast cell lines. The aim of this study is to find a safe method of isolating viable cell lines out of tissues from the operating room.

METHODS

Mixed cells from ascending aorta obtained from the operating room were incubated with an endothelial-specific fluorescent marker. The labeled cells were activated and sorted by flow cytometry. Isolated cell lines were cultured and thereafter square sheets of polymeric scaffold were seeded with myofibroblasts, followed by endothelial cells. The created tissue was stained with hematoxylin and eosin, van Gieson stain, and stains for factor VIII and CD34.

RESULTS

Control culture samples (n = 25) revealed vital uncontaminated endothelial and myofibroblast cell lines. Microscopy of the seeded meshes (n = 16) demonstrated a tissue-like structure. Van Gieson stain showed production of collagen. Endothelial cells formed a superficial monolayer, demonstrated by factor VIII and CD34; no invasive formation of capillaries was detectable.

CONCLUSIONS

These results demonstrate that fluorescence activated cell sorting is a reliable and safe method to gain pure vital autologous cell lines out of human mixed cells for subsequent seeding on degradable mesh and that those cells are active to form new tissue.

[The significance of endothelial adhesion molecules in heart surgery]

Myocardial ischemia and reperfusion is a common event in cardiovascular surgery patients. The endothelium has been shown to play a key role in the injury suffered after ischemia and reperfusion. When endothelial cells became hypoxic followed by reoxygenation they become activated to express endothelial adhesion molecules followed by the migration of neutrophils into the tissue. These changes may contribute to the early postoperatively myocardial dysfunction. An increased understanding of the interaction between leukocytes and endothelium may allow to develop new therapies in future.

Tissue engineering: a new approach in cardiovascular surgery--seeding of human fibroblasts on resorbable mesh

INTRODUCTION

In tissue engineering the material properties of synthetic compounds are manipulated to enable delivery of dissociated cells onto a scaffold in a manner that will result in in vitro formation of new functional tissue. The seeding of human fibroblasts on resorbable mesh is a precondition of a successful creation of human tissue such as autologous cardiac valves.

MATERIAL AND METHODS

Polymeric scaffolds (n = 12) composed of polyglycolic acid (PGA) with a fiber diameter of 12-15 mm and a polymer density of 70 mg/ml were used as square sheets of 0.3 x 1 x 1 cm. Fibroblasts (passage 5), harvested from human foreskin, were seeded (3.4 x 10(6)) and cultured over a 3 week period on a PGA mesh.

RESULTS

Microscopic examination of the seeded mesh demonstrated that the human fibroblasts were attached to the polymeric fibers and had begun to spread out and to divide. Electron microscopy showed a continuous distribution and formation of the cells throughout the "polymeric architecture". Spotlike hydrolysis of PGA fibers was observed. After 3 weeks the seeded scaffolds resembled a solid sheet of tissue.

CONCLUSION

These preliminary results, successful seeding of human fibroblasts on a PGA mesh, represent a first basic step on the way to construct human tissue such as autologous cardiac valves and demonstrate that tissue engineering might be a promising new device in therapy of cardiovascular disease.

Improved visualization in minimally invasive coronary bypass grafting

A special surgical technique is required for minimally invasive coronary artery bypass grafting, particularly under beating-heart conditions. We describe a very simple system that provides improved visualization of the surgical site.

Effect of soluble complement receptor type 1 on reperfusion edema and neutrophil migration after lung allotransplantation in swine

OBJECTIVE

Soluble complement receptor type 1 inhibits complement activation by blocking C3 and C5 convertases of the classical and alternative pathways. We evaluated the effect of soluble complement receptor type 1 on lung allograft reperfusion injury.

METHODS

Left lung transplantation was performed in 13 weight-matched pigs (25 to 31 kg) after prolonged preservation (20 hours at 1 degree C). One hour after reperfusion the recipient contralateral right lung was excluded to assess graft function only. Complement activity and C3a levels were measured after reperfusion and at the end of the assessment. Extravascular lung water index, intrathoracic blood volume, and cardiac output were assessed during a 5-hour observation period. Gas exchange and hemodynamics were monitored. At the end of the 5-hour assessment period, myeloperoxidase assay and bronchoalveolar lavage were performed to assess neutrophil migration, and C5b-9 (membrane attack complex) deposits in the allograft were detected by immunohistochemistry. Two groups were studied. In group II (n = 6) recipient animals were treated with soluble complement receptor type 1 (15 mg/kg) 15 minutes before reperfusion. Group I (n = 7) served as the control group.

RESULTS

Serum complement activity was completely inhibited in group II. In contrast to group I, C5b-9 complexes were not detected in group II allograft tissue samples. C3a was reduced to normal levels in group II (p = 0.00005). Extravascular lung water index was higher in group I animals throughout the assessment period (p = 0.035). No significant difference in allograft myeloperoxidase activity (p = 0.10) and polymorphonuclear leukocyte count of the bronchoalveolar lavage fluid (p = 0.057) was detected.

CONCLUSION

Inhibition of the complement system by soluble complement receptor type 1 blocks local complement activation in the allograft and reduces posttransplantation reperfusion edema but does not improve hemodynamic parameters.

Preoperative predictors of recurrent atrial fibrillation late after successful mitral valve reconstruction

OBJECTIVE

Late outcome after mitral valve repair was examined to define preoperative predictors of recurrent atrial fibrillation late after successful mitral valve reconstruction.

METHODS

One hundred and eighty-nine patients, 112 with preoperative sinus rhythm and 72 with preoperative chronic or intermittent atrial fibrillation, were followed for 12.2 +/- 10 years after valve repair. Clinic, hemodynamic end echocardiographic data were entered into Cox-regression and Kaplan-Meyer analysis to assess predictors for recurrent atrial fibrillation late after successful mitral valve repair.

RESULTS

Univariate and multivariate predictors for recurrent atrial fibrillation late after successful mitral valve reconstruction were preoperative atrial fibrillation (P = 0.0001), preoperative antiarrhythmic drug treatment (P = 0.005), heart rate (P = 0.01), left ventricular ejection fraction (P = 0.01) and increased left ventricular posterior wall thickness (P = 0.05). Patients > 57.5 years with a mean pulmonary artery pressure > or =23 mm Hg and a history of preoperative antiarrhythmic drug treatment had an odds ratio of 53.33 (95% confidence limits 6.12-464.54) for atrial fibrillation late after successful mitral valve repair.

CONCLUSION

Older patients with a history of atrial fibrillation, antiarrhythmic treatment or an elevated pulmonary artery pressure may present atrial fibrillation late after successful mitral valve repair. They could be considered for combined mitral valve reconstruction and surgery for atrial fibrillation even though sinus rhythm is present preoperatively.

Endothelial cell injury in cardiac surgery: salicylate may be protective by reducing expression of endothelial adhesion molecules

OBJECTIVE

Cardiac surgery with cardiopulmonary bypass induces ischemia to the heart, hypoxemia to various tissues and release of endotoxins. The endothelial cell may suffer from hypoxia and trigger cascades of adverse reactions by activation of neutrophils through adhesion molecules. The authors measured expression of intercellular adhesion molecule-1 (ICAM-1), during hypoxia and normoxia and hypothesized that salicylate, which inhibits the nuclear factor-kappaB (NFkappaB), an hypoxia-dependent transmission factor, could reduce this expression.

METHODS

Human umbilical vein endothelial cells were cultured and exposed to normoxia and hypoxia in the presence of lipopolysaccharide (LPS). The endothelial cells were thereafter treated with salicylate or indomethacin under the same conditions. The surface expression of ICAM-1 was measured by whole cell enzyme-linked immunosorbent assay (ELISA) and the NFkappaB expression by Western blotting.

RESULTS

In the presence of LPS and under hypoxic conditions, the endothelial cells produced a 300 +/- 41% increased expression of ICAM-1 compared with normoxia. The addition of salicylate (0.02-20 mM) completely inhibited the enhanced expression of ICAM-1, the addition of indomethacin at equivalent concentrations did not reduce ICAM-1 expression under either condition.

CONCLUSION

ICAM-1 expression is greatly enhanced by the hypoxic endothelial cell in the presence of circulating endotoxin. Pre-treatment with salicylate completely abolishes the enhanced expression. The study suggests that salicylate administered before cardiopulmonary bypass might protect the heart against ischemic/reperfusion injuries and reduce the load of the overall inflammatory reaction.

Tissue engineering: a new approach in cardiovascular surgery: Seeding of human fibroblasts followed by human endothelial cells on resorbable mesh

OBJECTIVE

In tissue engineering the material properties of synthetic compounds are chosen to enable delivery of dissociated cells onto a scaffold in a manner that will result in in vitro formation of a new functional tissue. The seeding of human fibroblasts followed by human endothelial cells on resorbable mesh is a precondition of a successful creation of human tissues such as vessels or cardiac valves.

METHODS

Polymeric scaffolds (n = 18) composed of polyglycolic acid (PGA) with a fiber diameter of 12-15 microm and a polymer density of 70 mg/ml were used as square sheets of 1 x 1 x 0.3 cm. Fibroblasts (passage 7) harvested from human foreskin were seeded (3.4 x 10(6)) and cultured over a 3 week period on a PGA-mesh, followed by seeding of endothelial cells (passage 5, 2.8 x 10(6)) harvested from human ascending aorta. Thereafter the new tissue was stained for HE, van Gieson, Trichrom Masson, Factor VIII and CD 34 and proved by scanning electron microscopy.

RESULTS

Microscopic examination of the seeded mesh demonstrated that the human fibroblasts were attached to the polymeric fibers and had begun to spread out and divide. The scanning electron microscopic examination demonstrated a homogeneous scaffold resembling a solid sheet of tissue. The seeded endothelial cells formed a monolayer on the fibroblasts and no endothelial cell invasion or new formation of capillaris could be detected.

CONCLUSIONS

These results are a first step to demonstrate that seeding of human fibroblasts and endothelial cells on PGA-mesh might be a feasible model to construct human tissues such as vessels or cardiac valves.

Composite graft replacement of the aortic root in acute dissection

OBJECTIVE

In acute type A dissection the indication for composite graft replacement of the aortic root and the optimal implantation technique are a matter of debate. In this study early and late results of root replacement in acute dissection are determined and compared with supracoronary graft replacement. Two implantation techniques (open vs. inclusion) are evaluated.

METHODS

Between 1985 and 1995, 207 consecutive patients (mean age 58 +/- 12 years, 78% men) were operated for acute type A dissection of the aorta. Root replacement in 50 patients (inclusion technique in 34/50 patients with Cabrol shunt in 15/34 patients, open technique in 16/50 patients) was compared with more conservative procedures in 157 patients: supracoronary graft replacement in 143 patients (with aortic valve replacement in 23 patients) and local repair without graft interposition in 14 patients. Preoperative risk factors, like hemodynamic instability, renal failure, neurologic disorder and coronary artery disease did not differ in the two treatment groups.

RESULTS

Early results, survival and reoperation-free survival after 5 years were insignificantly better after root replacement: mortality 10/50 (20%) vs. 38/157 (24%) P = n.s.; hemorrhage 10/50 (20%) vs. 39/157 (25%) P = n.s.; stroke 5/50 (10%) vs. 27/157 (17%) P = n.s.; survival 70 +/- 7% vs. 63 +/- 4%, reoperation free survival 92 +/- 6% vs. 78 +/- 5% P = 0.0815). For the open technique, early mortality was 18.8 vs. 20.6%, P = n.s. and reoperation free survival at 5 years was 80.7 vs. 65.2%, P = n.s. Perioperative complications did not differ in the two technical groups and a single pseudoaneurysm occurred in the Bentall group.

CONCLUSION

In acute dissection composite graft replacement of the aortic root can be carried out with good early and late results not inferior to more conservative procedures. The open technique is the implantation method of choice and the modified Bentall technique is indicated in situations with increased risk of bleeding.

[How to do: initial experiences with a new device in minimally invasive heart surgery]

A special surgical technique is required for minimal-invasive cardiac surgery. The view for the coronary artery anastomosis under beating heart conditions is important and coronary artery blood might prevent a clear view of the opened coronary artery vessel. A new system called VisoFlo promises to improve visualisation at the surgical site. VisoFlo delivers a column of air to help provide a clear view of anastomosis site and in addition has a controllable mist to help prevent desiccation of the graft and surrounding tissue. This system was tested on 45 patients with coronary-artery-bypass graft surgery under beating heart conditions and at 65 patients with standard coronary-artery-bypass graft surgery. Our conclusions are, that the VisoFlo system is easy to use, guarantees a clear view of the anastomosis site and the surgical work will not be impaired.

Hypoxia enhances induction of endothelial ICAM-1: role for metabolic acidosis and proteasomes

Intercellular adhesion molecule 1 (ICAM-1) is an important molecule in promotion of polymorphonuclear neutrophil transendothelial migration during inflammation. Coincident with many inflammatory diseases is tissue hypoxia. Thus we hypothesized that combinations of hypoxia and inflammatory stimuli may differentially regulate expression of endothelial ICAM-1. Human endothelial cells were exposed to hypoxia in the presence or absence of added lipopolysaccharide (LPS) and examined for expression of functional ICAM-1. Although hypoxia alone did not induce ICAM-1, the combination of LPS and hypoxia enhanced (3 +/- 0.4-fold over normoxia) ICAM-1 expression. Combinations of hypoxia and LPS significantly increased lymphocyte binding, and such increases were inhibited by addition of anti-ICAM-1 antibodies or antisense oligonucleotides. Hypoxic endothelia showed a > 10-fold increase in sensitivity to inhibitors of proteasome activation, and combinations of hypoxia and LPS enhanced proteasome-dependent cytoplasmic-to-nuclear localization of the nuclear transcription factor-kappa B p65 (Rel A) subunit. Such proteasome activation correlated with hypoxia-evoked decreases in both extracellular and intracellular pH. We conclude from these studies that endothelial hypoxia provides a novel, proteasome-dependent stimulus for ICAM-1 induction.

[False aneurysm in Behçet's syndrome]

HISTORY AND CLINICAL FINDINGS

A 32-year-old man developed acute right-sided sore throat, a thick voice and epistaxis. 13 years previously he had erythema nodosum, 12 and 10 year ago deep vein thrombosis. On admission he had Horner's syndrome, bulging of the gums and swelling of the paratracheal space. He had been on anticoagulation therapy with phenprocoumon since the leg vein thrombosis.

INVESTIGATIONS

Computed tomography demonstrated a false aneurysm of the right internal carotid artery. 9 months later a right radial artery aneurysm occurred, which was treated surgically. An arterial cannula had previously been placed at this site for pressure monitoring. 2 months later a false aneurysm of the right femoral artery was diagnosed: it had previously been used for an intravascular intervention. As embolization to the popliteal artery occurred after sonographically controlled compression had failed and reduction of anticoagulation treatment, this aneurysm, too, was treated surgically.

DIAGNOSIS, TREATMENT AND COURSE

Because of the tendency to aneurysm formation after arterial puncture and the history of venous thromboses the diagnosis of Behçet's syndrome was considered, confirmed by subsequently elucidated history of recurrent oral aphthous ulcers and folliculitis. There were no other manifestations of the syndrome. Immunosuppressive treatment was instituted after another two aneurysm recurrences were noted in the right common femoral artery.

CONCLUSIONS

This case illustrates that the diagnosis of Behçet's syndrome may be made more difficult if its manifestation is primarily vascular with minimal mucocutaneous involvement. It should be considered in the differential diagnosis of recurrent arterial aneurysms in a young person.