F. Caes

Phosphorylcholine coating offers natural platelet preservation during cardiopulmonary bypass

Return of blood activated by tissue factor is the main culprit for triggering the coagulation cascade. When this activated blood is diverted from the cardiopulmonary bypass (CPB) circuit, it becomes possible to evaluate the effect of surface treatment on platelet and complement activation. Twenty adult patients undergoing elective coronary artery bypass grafting (CABG) were randomly assigned either to a control group ( n = 10) or to a group in which the CPB circuit was completely coated with phosphorylcholine ( n = 10). Plasma concentrations of platelet factor 4 (PF4), β-thromboglobulin (βTG), C3, C3d, C4, TCC, thrombin generation, haptoglobin and free haemoglobin, as well as blood loss, were measured. No significant differences between the two groups were found for haemolysis and thrombin generation. The mean total release of PF4 and βTG during CPB was 9338± 17303 IU/ml/CPB and 3790± 4104 IU/ml/CPB in the coated group versus 22192± 13931 IU/ml/CPB ( p = 0.011) and 8040± 3986 IU/ml/CPB ( p = 0.005) in the control group. Blood loss was 30% less in the coated group compared to the control group. Phosphorylcholine coating appears to have a favourable effect on blood platelets, which is most obvious after studying the changes during CPB. Clinically, this effect resulted in a 30% reduction in blood loss.

Valve replacement with the ATS open pivot bileaflet prosthesis

OBJECTIVE We sought to evaluate the ATS open pivot bileaflet valve with respect to haemodynamics and thromboembolism. METHODS We prospectively studied 200 consecutive patients aged 13-80 years. One hundred and nineteen aortic, 103 mitral and 11 tricuspid valves were replaced in 172 single, 23 double and 5 triple valve procedures. Thirty-eight were re-operations and 51 underwent coronary bypass. Transvalvular gradients were determined by transoesophageal and transthoracic echocardiography. Patients were followed for 12 months to 3 years. RESULTS There were four hospital (2%) and three late deaths, each non-valve related. Two patients were reoperated for partial valve dehiscence. One aortic reoperation patient suffered a potential transient thromboembolic event. One tricuspid prosthesis thrombosed after anticoagulation was discontinued but thrombolysis resolved this problem. There were no other thromboembolic events. Valve gradients were equivalent or better than those for other bileaflet valves. CONCLUSIONS The ATS valve has excellent haemodynamic characteristics and a very low thromboembolic rate, probably related to the convex self-washing hinge mechanism. Consequently, we have reduced anticoagulant levels to INR (international normalised ratio) 1.5 to 2.0 for aortic valve patients in sinus rhythm. Early experience suggests that the ATS valve functions well in the tricuspid position.

The valve choice in tricuspid valve replacement: 25 years of experience

This study reviews 146 consecutive patients who underwent tricuspid valve replacement (TVR) with 69 bioprostheses (porcine and bovine pericardial) and 77 mechanical ball, disc or bileaflet valves between 1967 and 1987. The mean age was 51.4 +/- 12.1 years. Preoperatively, 97% were in New York Heart Association (NYHA) functional class III or more and over 40% had undergone previous cardiac surgery. Hospital mortality was high (16.1%). Incremental risk factors for hospital death were preoperative icterus (P < 0.01), hepatomegaly (P = 0.02), NYHA functional class IV (P = 0.02) and male sex (P = 0.04) (univariate analysis). Ninety-eight percent of the hospital survivors were followed up for a mean of 92 months. Cumulative follow-up added up to 955 patient-years. There were 70 late deaths. The actuarial survival rate was 74% at 60 months and less than 25% at 14 years. Incremental risk factors for late death indicated by univariate analysis were the type of tricuspid prosthesis (Smel-off-Cutter and Kay-Shiley prostheses) (P = 0.04), the type of operative myocardial protection (normothermia and coronary perfusion) (P = 0.05) and preoperative NYHA functional class IV (P = 0.05). We conclude that TVR carries a high operative risk and poor long-term survival, both influenced by preoperative and perioperative variables. Bearing in mind the poor prognosis for TVR, we prefer a large-sized bioprosthesis, in view of its initial good durability and low risk of valve-related events. However, in patients with good life expectancy, a bileaflet mechanical prosthesis may be an acceptable alternative.

Operative outcome of minimal access aortic valve replacement versus standard procedure.

Abstract Background: to determine the advantages and/or risks of minimal access aortic valve replacement compared to standard sternotomy procedure. Methods: from January 1997 to December 2001, 271 consecutive adult patients underwent isolated aortic valve replacement of which 174 underwent a minimal access procedure (Group 1) and 97 a standard procedure (Group 2).The preoperative variables of both groups were comparable. Retrospective analysis of postoperative outcome was performed. Results: follow-up was complete and ranged from 6 months to 4 years. Overall in-hospital mortality was 3.3% (respectively 2.8 and 4.1%). No statistical difference was noted regarding operative time variables, mortality rate and hospital stay. There was a significant higher incidence of revision (p = 0.018) and late pericardial effusion (p = 0.022) in the minimal access group. Also trends were in favour of the standard group for incidence of postoperative pneumothorax and pericarditis constrictiva. Conclusions: minimal access aortic valve replacement is a safe and reliable technique, but carries the risk of incision-related morbidity. Proper patient selection and perioperative management is mandatory.

Off-pump coronary surgery : surgical strategy for the high-risk patient

OBJECTIVE In a retrospective study, we compared two groups of consecutive patients operated by the same team during the year 2000 for coronary artery disease with the use of extracorporeal circulation (group 1, n=230) or on the beating heart using the Octopus II plus stabiliser (group 2, n=228). High-risk patients were identified by a EuroSCORE plus 6. EuroSCORE definitions and predicted risk models were utilized to compare the variables of the groups. METHODS There were no significant differences between the preoperative variables of the groups in age, gender, left ventricular function, diabetes and peripheral vascular and renal disease as is indicated by the Euroscore (resp. 4.7/5.1 p=0.107). Calcification of the ascending aorta and chronic obstructive lung disease were statistically significant more prevalent in the beating heart group. No differences in preoperative variables in the high-risk patients group (Euroscore 8.5/8.1 p=0.356) except for calcification of the ascending aorta. RESULTS All patients underwent a full revascularisation through a midline sternotomy. Significant more distal anastomoses were performed in group 1 (3.7 per patient (1-6)) with regard to group 2 (2.9 per patient (1-6)). Anesthesia, postoperative treatment and follow up were equal for both groups. A significant lower incidence of atrial fibrillation (p=0.010), shorter ICU stay (p=0.031) and renal insufficiency (p=0.033) was reported in group 2. In the low risk group, we could not diagnose any difference between the two groups, except for atrial fibrillation. The benefits of the beating heart surgery however were more pronounced in the high-risk patient as is indicated by a significant reduction of the ICU stay by 1 day (3.5d/2.5d (p=0.028)), better preservation of the renal function (p=0.017) and a significant reduction of the length of hospital stay by more than two days (p=0.040). A lower incidence of atrial fibrillation, however not significant. CONCLUSION In our experience, beating heart surgery is a safe alternative for conventional coronary heart surgery. High-risk patients do benefit most from this technique. It became our first choice in the elderly patient and patients presenting with higher co-morbidities.

Clinical evaluation of a new hollow fibre membrane oxygenator

Twelve consecutive patients undergoing elective cardiac surgery were perfused with the Cobe Optima hollow fibre oxygenator. Gas transfer characteristics and blood handling were studied. The device had a maximum oxygen transfer of 315 ml/minute. The average shunt fraction was 4.5%, and was not influenced by blood-flow rate. Mean platelet count declined slightly to 91 % of the baseline at the end of the study period. Haemolysis was evaluated by monitoring serum-free haemoglobin, serum haptoglobin and serum haemopexin. The evolution was as follows: free haemoglobin increased from 14 ± 5 mg/100 ml to 85 ± 0.8/100 ml (p = 0.01) at the end of bypass; haptoglobin decreased from 1.33 ± 0.90 g/l to 0.89 ± 0.15 g/l (p = 0.01); and haemopexin decreased from 0.84 ± 0.13 g/I to 0.74 ± 0.15 g/l (p = nonsignificant). In all patients the residual capacity of serum haptoglobin to protect against haemolysis was satisfactory. All patients had an uneventful postoperative course.

An experimental model of coronary anastomosis without suturing

OBJECTIVE The aim of the study is to explore the feasibility and mid-term patency of an easier anastomotic technique for Minimally Invasive Direct Coronary Bypass Grafting (MIDCAB). METHODS Eight mongrel dogs (+/-15 kg) underwent direct anastomosis between the left internal thoracic artery (LITA) and the left anterior descending coronary artery (LAD) via inferior sternotomy on the beating heart. After positioning the graft, the distal part of the LAD was opened to allow retrograde filling of the LITA-graft. The anastomosis was secured by the use of biological glue (BioGlue, Cryolife, Marietta, GA, USA). No intravascular suture material was used. Ischemic time averaged 6 min. The proximal LAD was occluded upstream the arteriotomy. All survivors were angiographically controlled for patency after 6-8 weeks. Consequently, four dogs were sacrificed after 6 weeks and the remaining after 3 months for anatomo-pathological and histological examination by light and electron microscopy of the anastomotic site. RESULTS All procedures were successful except for one animal that died of uncontrollable bleeding at the anastomotic site. Another sustained post-operative transmural anterior myocardial infarction due to a late graft occlusion. All angiographically controlled grafts were patent with two vascular strings near the anastomotic site. Histology showed early macrophage infiltration into the glue. At post-mortem examination, new endothelialization was noticed in 80% of the cases. However, ultrastructural examination detected marked differences in endothelial fibroblastic lining compared to normal histology. CONCLUSIONS Good mid-term permeability of the LITA grafts was observed in this new anastomotic technique for MIDCAB in the canine model. Although neo-endothelialization was present in most cases, ultrastructural differences were noticed after 3 months in the neo-intima compared to normal.

Feasibility of a pumpless extracorporeal respiratory assist device

BACKGROUND Our study evaluated the efficacy and feasibility of a pumpless respiratory assist device and determined its capacity for carbon dioxide removal. METHODS In five adult pigs the left femoral vein and artery were cannulated with a 20F cannula and connected to a low-pressure hollow-fiber artificial lung. After we had obtained baseline values of mean arterial pressure, cardiac output, and blood flow across the artificial lung, the mean arterial pressure was reduced 20% and 40% relative to baseline; in a second phase, it was raised 20% and 40. Cardiac output and artificial lung flow were simultaneously recorded. We determined the carbon dioxide removal capacity of the artificial lung by gradually increasing the arterial partial carbon dioxide tension of the animal. RESULTS An increase of 10 mm Hg in mean arterial pressure resulted in an increase of flow of 0.14 L/min. The mean pressure drop across the artificial lung was measured at 17 +/- 9 mm Hg. The shunt flow over the artificial lung varied between 14 and 25% of the cardiac output of the animal. Depending on inlet conditions, carbon dioxide removal by the artificial lung was between 62 +/- 22 mL/L/min and 104 +/- 25 mL/L/min. CONCLUSIONS A pumpless respiratory assist device can remove a significant proportion of the metabolic carbon dioxide production. However, adequate mean arterial pressure is mandatory to maintain sufficient flow across the device. The technique seems attractive because of its simplicity and can be used in acute lung injury in conjunction of apneic oxygenation for prolonged respiratory support.

Anticoagulation revised for mechanical ATS heart valve implants

From May 1993 to June 1996, 262 consecutive patients had 312 new ATS (ATS Med. Inc., Minneapolis, USA) mechanical bileaflet valves inserted (169 aortic, 131 mitral, 12 tricuspid). We divided our patients into 3 groups: group 1 comprised all aortic valve patients in regular sinus rhythm (100 patients), group 2 all single valve replacements in atrial fibrillation (116), whereas group 3 included all double or triple valve replacements (46). The anticoagulation regime in group 1 was prospectively lowered to an I.N.R. (International ratio) between 1.5 and 2.5, instead of our regular aim to keep the I.N.R. strictly between 2.5 and 3.5 for mechanical valves. The follow-up period ranged from 6 to 42 months and was completed in respectively 99,97 and 98% of cases. We encountered no hospital-deaths in our first group, compared to 4 and 1 in the latter groups, although all were non-valve related. The actuarial survival was resp. 100,94, and 92% at one and 100,93, and 90% at two years. The linearized rate of incidence of complications (percent/patient-years) was respectively of the 3 groups: for paravalvular leakage: 1.2–0–2.2; endocarditis: 0–0–1.2; thrombem-bolism: 0.6–1.5–1.1; hemorrhage: 0–0.5–0.5; valve thrombosis: 0–0–0.1; structural deterioration: 0–0–0. Risk factors for death were poor preoperative status and for major cardiac events, the presence of atrial fibrillation and poor ventricular function. The excellent results of our group 1 patients could inspire the lowering of the anticogulation regime for all aortic ATS valve patients in regular sinus rhythm with good ventricular function.

Trapped venous embolus in a patent foramen ovale causing recurrent paradoxical embolism

The combination of deep venous thrombosis, patent foramen ovale and arterial emboli suggests the diagnosis of paradoxical embolism. In these cases, only very rarely, a causal relationship between the venous thrombus and the patent foramen can be established. An instructive case of trapped venous embolism within the foramen ovale is described proving a causal relationship between arterial embolism and its venous origin.