The effect of hydroxyethyl starch 6% 130/0.4 compared with gelatin on microvascular reactivity.

We compared the effects on microvascular reactivity of hydroxyethylstarch (Volulyte(®) ) and gelatin (Geloplasma(®) ) during acute haemodilution. The hypothesis was that Volulyte would provide better microvascular reactivity than Geloplasma. Forty patients undergoing elective cardiac surgery were randomly assigned to receive either Volulyte or Geloplasma as the exclusive priming solution of the cardiopulmonary bypass. To evaluate microvascular reactivity, postocclusive reactive hyperaemia was examined before and after cardiopulmonary bypass. Microvascular reactivity assessments included the rate of the occlusion and reperfusion slopes and reperfusion times. After cardiopulmonary bypass, increases in reperfusion time were significantly smaller in the Volulyte group (3 (-27 to 9 [-35 to 33]%) vs 29 (-17 to 76 [-34 to 137]%) in the Geloplasma group, p = 0.02 between groups). Rate of reperfusion increased in the Volulyte group (26 (-17 to 43 [-59 to 357])%), whereas it decreased in the Geloplasma group (-22 (-47 to 16 [-84 to 113])%), p = 0.02 between groups. The shorter reperfusion times and increased reperfusion rate suggest that Volulyte maintains better microvascular reactivity than Geloplasma.

Intramyocardial paravalvular abscess after aortic valve replacement.

Myocardial abscess is a rare but life-threatening disease with various clinical presentations. We describe the case of a paravalvular abscess distending intramurally 7 years post surgery for aortic valve replacement. Early detection and urgent surgical intervention is essential for this otherwise fatal disease entity.

Active or passive bio-coating: does it matters in extracorporeal circulation?

BACKGROUND: Two types of surface coating for cardiopulmonary bypass (CPB) are used: bioactive (heparin, nitric oxide) and biopassive (albumin, polyethyleneoxide (PEO), phosphorylcholine). When haemocompatible coatings are combined with the separation of pleuro-pericardial aspiration, attenuation of both the coagulation and complement cascades, as well as better platelet preservation, has been demonstrated. This study wants to investigate if the combination of a bioactive with a biopassive coating (unfractionated heparin embedded in a phosphorylcholine matrix) combines the beneficial effects of both approaches. MATERIALS AND METHODS: Thirty patients undergoing elective CABG were prospectively randomized into two groups of 15 patients. The sole exclusion criterion was an ejection fraction of less than 40%. In the control group (PC), the whole CPB circuit was coated with phosphorylcholine (PC). In the study group (XPC), unfractionated heparin was embedded in the PC matrix of the oxygenator and arterial line filter. RESULTS: No differences were found for haemolytic index, thrombin-anti-thrombin complex (TAT), IL-6, IL-10 and blood loss. PF4 plasma concentration increased from 27.6±22.0 IU/mL to 165.7±43.9 IU/mL (p<0.001) at 15 minutes of CPB in the PC and from 16.0±9.7 IU/mL to 150.9 ± 61.3 IU/mL (p<0.001) in the XPC group. Terminal complement complex (TCC) increased over time in both groups until the end of CPB (Figure 2A). Within each group, TCC generation was statistically significantly higher after the release of the aortic cross-clamp (p<0.001) and at the end of CPB (p<0.001). Total TCC generation was statistically significantly higher in the XPC group compared to the PC group (p=0.026). The difference was statistically significant after the release of the aortic cross-clamp (p=0.005) and at the end of CPB (p=0.001). CONCLUSIONS: Based on our results, there is no additional benefit in combining phosphorylcholine with unfractionated heparin in elective patients undergoing coronary artery bypass grafting (CABG). Massive haemodilution leads to enhanced complement activation.

Haemostasis monitoring during sequential aortic valve replacement and liver transplantation.

Despite advances in anaesthesiological and surgical techniques, cardiac surgery in cirrhotic patients remains hazardous. This report outlines our experience with haemostasis monitoring in two consecutive cases of sequential aortic valve replacement and liver transplantation. Clotting disturbances proved to have fatal consequences since one of these patients died following massive lung embolism. The second patient underwent successfully this combined procedure and is in good clinical state 14 months postoperatively. Evaluation and discussion of the coagulation monitoring by the Sonoclot Analyzer in both patients and related therapeutic suggestions for the prevention of thrombotic events are discussed.

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

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.

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.

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.

Tissue factor as the main activator of the coagulation system during cardiopulmonary bypass.

OBJECTIVE: This study investigates the influence of foreign material and blood aspirated from nonvascular structures on activation of coagulation, hemolysis, and blood loss. METHODS: The series comprises 3 randomized groups (groups C, S, and S+P) of 10 patients undergoing routine coronary artery bypass grafting with cardiopulmonary bypass. In group C, the control group, all aspirated blood was returned into the circulation. In group S suction blood was discarded, whereas group S+P was identical to group S, with surfaces coated with phosphorylcholine. Plasma concentrations of beta-thromboglobulin, thrombin generation, haptoglobin, and free hemoglobin, as well as blood loss, were measured. RESULTS: A steady increase in free plasma hemoglobin, as well as an increased generation of thrombin, was noticed in group C. Moreover, a close correlation (r = 0.916) between the generation of thrombin and its inhibition (thrombin-antithrombin complexes) was observed. Platelets were clearly activated in group C and, to a lesser extent, in group S. In contrast, platelet activation in group S+P was negligible, resulting in a 30% decrease in blood loss (P =.05). CONCLUSIONS: Aspirated blood contaminated by tissue contact is the most important activator of the coagulation system and the principal cause of hemolysis during cardiopulmonary bypass. Contact with a foreign surface is not a main variable in the procoagulant effect of bypass. Mimicking the outer cell membrane structure resulted in decreased platelet activation and decreased blood loss.

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), beta-thromboglobulin (betaTG), 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 betaTG 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.

Redo mitral surgery using the Estech endoclamp.

BACKGROUND: Redo-CABG surgery remains extremely hazardous in the presence of open bypass grafts. In our patients with mitral valve pathology with open and well-functioning bypass grafts, we explored alternative approaches in order to avoid damage to the grafts by extensive dissection and direct clamping of the ascending aorta. The "Estech procedure," which uses the Estech remote access perfusion (RAP) endoclamp catheter (Estech Inc., Danville, CA), was selected for these patients. METHODS: From January 1998 to January 2000, 10 patients underwent an Estech procedure for redo mitral surgery. All patients had previous cardiac operations such as coronary artery bypass grafting (CABG) and/or mitral valve procedures. The Estech procedure consisted of an anterior left thoracotomy and peripheral cannulation at femoral site using the Estech endovascular balloon technique. The series was comprised of seven mitral valve replacements, two valve reconstructions, and one closure of a paravalvular leak. One procedure had to be converted to a standard re-sternotomy due to extreme arteriosclerosis of the descending aorta with plaque dislocation at the time of catheter insertion. However, no damage was inflicted to the open bypass grafts. RESULTS: The follow-up period ranged from six to 30 months and was 100% complete. We encountered one hospital death in our group, which was due to a late post-operative intestinal infarction and multiple organ failure (MOF), and was not procedure related. As expected, morbidity was high in this compromised cohort, but no late death has occurred prior to submission of this article. All survivors progressed to an acceptable NYHA functional class. CONCLUSION: The excellent results in this complex patient group inspired us to use the Estech procedure as a standard approach for redo mitral surgery.

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.

The influence of low afterload on the nature of the stress-velocity relationship.

OBJECTIVES: Correct assessment of contractility by conventional methods during manipulation of afterload is often disappointing. To this purpose, the stress-velocity relationship offers assessment of contractility at different levels of afterload. We decided to study the influence of afterload on the nature of the stress-velocity relation. BACKGROUND: Although linear at baseline conditions in a population older than two years, data in newborns or after administration of low-dose dobutamine suggest a different nature of this relationship at low afterload. METHODS: Ten healthy piglets (five to six weeks; 11 to 13 kg) were studied. End-systolic meridional wall stress (ESWS) and rate-corrected velocity of circumferential fiber shortening (VcFc) were measured in these piglets at baseline, after balloon occlusion of the descending aorta, and at nitroprusside infusion rates of 1, 2 and 5 microg/kg/min. To eliminate inotropic influences mediated by reflex tachycardia, we subsequently studied five piglets and six adult pigs after bilateral cervical vagotomy. RESULTS: The ESWS changed from a baseline mean of 50 g/cm2 to 137 g/cm2 after balloon occlusion and to 19 g/cm2 at 5 microg/kg/min of nitroprusside. The VcFc changed from 1.19 c/s (circumference/second) to values of 0.9 c/s and 1.73 c/s, respectively. The ensuing stress-velocity regression line proved to be curvilinear instead of linear. The steeper slope at low afterload could suggest enhanced contractility compared to expected values had the relationship been linear. CONCLUSIONS: Data from young piglets and adult pigs suggest a curvilinear relationship of the stress-velocity relationship. This could probably explain some of the "hypercontractile states" encountered in conditions with low afterload.

Stentless or stented aortic valve implants in elderly patients?

OBJECTIVE: To assess differences in indication and mid-term results between stentless and stented procedures in elderly patients, we followed aortic valve patients over a period of 5 years. METHODS: In a consecutive series of 154 elderly aortic patients in regular sinus rhythm from 1992 to 1997, we inserted 103 stentless (Toronto SPVTM, St Jude Medical Inc., St Paul, Minneapolis, MN) and 51 stented (Carpentier-Edwards supra annular porcine, Baxter Inc., Irvine, CA) bioprostheses in the aortic position. RESULTS: All 154 patients seemed preoperatively eligible for a stentless procedure. Mean age was 74.8 years (range 67-86 years) with a majority of female patients. The surgeon's (in)experience, major dilatation or calcifications of the ascending aorta and aberrant coronary anatomy were the most common reasons for drawback from the stentless procedure (51/154 patients). Aortic clamp time was significantly higher in the stentless vs. stented group (70 vs. 57 min, P < 0.0001). The large average 25.3 mm size of the stentless prostheses (vs. 23.7 mm stented) stands in full contrast with the low mean body surface area of 1.68 m2 (vs. 1.70 m2) of the patients. We encountered. respectively. 5 and 2 hospital-deaths (P = n.s.). The follow-up period ranged from 6 to 66 months and was 97% complete, yielding, respectively, 302 and 139 patient-years. Survival (Kaplan-Meier method) was statistically higher in favor of the stentless procedures (log rank: P = 0.03). All survivors progressed markedly to a mean postoperative NYHA class 1.3 respectively, 1.4 (vs. preop. 3.3 and 3.2). Echocardiographic transvalvular gradients compared favorable for the stentless group in the small under 25 mm valves (P = 0.02 for 23 mm sized valves between groups) with improved left ventricular function and a significant decrease of left ventricular end diastolic diameter (LVEDD 48.0 vs. 56.5 mm) at 1 year follow-up. Cusp calcifications on control echocardiography were detected earlier (beyond 3 years) in the stented group, without signs of early significant regurgitation or dysfunction in both groups, except for one patient necessitating re-operation. CONCLUSION: Although the implantation technique is much more demanding for stentless procedures, reflected by a longer aortic clamp-time, and remains impossible in some cases, elderly, small sized patients take full benefit of their large, non-obstructive prostheses.

Deformation of the stentless porcine valve scaffold enhances accelerated leaflet fibrosis and calcification in juvenile sheep.

Stent mounting of xenografts induces a loss of mobility and reduces the effective valve orifice. By contrast, the higher surgical technical expertise required for stentless procedures is a major obstacle for many surgeons. To facilitate the insertion of the Toronto SPV (St Jude Medical Inc, St Paul, Minneapolis, MN) stentless aortic valve, we tried to alter the porcine design by lowering the invasive profile at the depth of the sinuses on both coronary sites. This technique could theoretically facilitate implantation of the modified stentless valve with an easygoing single-layer suture at the challenging subcoronary level and make it more attractive for the surgeon. The standard model was modified by lowering the profile at the depth of the sinuses on both coronary sites, whether by plication (in 3 specimens, one of each size) or excision (in 3 others) of the protruding porcine aortic wall at the nadir of each coronary sinus. Animal implants in juvenile sheep (6 standard Toronto versus 6 modified valves of 21, 23, and 25 mm) were studied for durability and biocompatibility for 3 to 6 months. All valves were evaluated by postoperative echocardiography and after explantation examined macroscopically, radiographically, histologically, and electron microscopically. The standard valves performed well, although at 6 months after implantation, marked fibrosis was found at the outflow parts with scattered calcifications, essentially in the porcine aortic wall. The leaflets remained mobile and contained scant mineralization. By contrast, the modified specimen showed markedly accelerated fibrosis and significant cusp calcifications at distance from the altered zones. Severe restriction of the mobility of the leaflets was visible 3 months after implantation in the juvenile sheep model. The more pronounced the deformation of the modified scaffold, the faster and more intense the degradation and calcification of the leaflets far from the altered zones (worse in the heavily deformed, plicated cusps). Because all valve types were prepared by identical preservation techniques, this study shows that loss of mobility by distortion of the natural scaffold induces early failure. It is extremely important to correct implantation of stentless valves to prevent early degeneration.

In vivo evaluation of a phosphorylcholine coated cardiopulmonary bypass circuit.

A complete phosphorylcholine coated cardiopulmonary bypass circuit, including the Dideco D901 oxygenator, was tested for gas transfer, blood path resistance, and biocompatibility in a standardized setting. Blood compatibility was tested by measuring complement and platelet activation. Three dogs (mean body weight 28 +/- 3 kg) were placed on cardiopulmonary bypass at a flow rate of 600 mL/min during 6 hours. The animals were weaned from cardiopulmonary bypass and sacrificed electively after 7 days. Oxygen and carbon dioxide transfer were 26.6 +/- 2.4 mL/min and 33.0 +/- 1.9 mL/min, respectively. Mean pressure drop across the oxygenator was 52.6 +/- 0.2 mmHg. The respective baseline values for thromboxane B2, prostaglandin E2 and platelet factor 4 were 1817 +/- 283 pg/mL, 12783 +/- 2109 pg/mL, and 0.35 +/- 0.08 IU/mL. Thromboxane B2 and prostaglandin E2 increased slightly to 2881 +/- 868 pg/mL and 18083 +/- 3144 pg/mL at 30 minutes of bypass, whereas platelet factor 4 values remained stable curing the procedure. Concentrations of complement split products C5a were only mildly increased. After use scanning electron microscopy was performed on the inner housing, heat exchanger, and outer surface of the hollow fibers. No thrombi nor organized cellular deposits were found on any of the components. Phosphorylcholine coating of CPB seems to be very promising regarding platelet activation and complement activation.

Preconditioning and proximal ligation did not influence the outcome of direct internal mammary artery bypass grafting in a canine model.

The aim of this study was to assess the need for preconditioning and/or exclusion of competitive flow in minimally invasive coronary bypass grafting procedures (MICAB), to prevent early graft occlusion. Eight mongrel dogs (+/- 25 kg) were operated on under intravenous anaesthesia (sodium thiopenthal 15 mg/kg) and maintained with Halothan 1-2% and Pancurorium. A direct anastomosis between the left internal mammary artery and the left anterior descending coronary artery was performed, via anterior distal sternotomy, on the beating heart. Four dogs were preoperatively randomly conditioned by intravenous bolus injection of Diltiazem (0.0025 g/kg) prior to the procedure and after (meanwhile the left internal mammary artery takedown, the proximal coronary artery was snared during 15 min). In the absence of ECG changes or rhythm disturbances, a direct anastomosis of the left internal mammary artery and the left anterior descending coronary artery was performed. In four control dogs, direct MICAB procedure was done without preconditioning. The proximal left anterior descending coronary artery was occluded upstream of the arteriotomy in two dogs from both groups to exclude competitive flow from the native coronary artery. All the procedures were successful, except for one conditioned dog that sustained preoperative transmural anterior myocardial infarction. Cardiac enzymes (CK and CKMB) rose in all groups immediately after the procedure; this was not statistically significant between groups. All survivors were angiographically controlled after 6 to 8 weeks. They showed good patency of all grafts (mean thrombolysis in myocardial infarction-flow equals 2.86). There was perfect matching between the left internal mammary artery and left anterior descending coronary artery in the conditioned and proximal occluded group, which was contrary to the competitive flow in the control groups between the open left anterior descending coronary artery and the left internal mammary artery graft. Permeability of the left internal mammary artery grafts are not influenced by preconditioning nor exclusion of competitive flow in the MICAB technique for the canine model. Graft diameter and flow are merely the result of outflow conditions. In one case, preconditioning was followed by fatal myocardial infarction.

Pulse duplicator hydrodynamics of four different bileaflet valves in the mitral position.

The hydrodynamic performance of four different types of bileaflet heart valve was tested both in steady flow conditions and in a newly designed computerized artificial left heart system. Four 29-mm valves, manufactured by either St. Jude Medical, CarboMedics, ATS Medical or Medtronic Parallel were studied under a steady state and in pulsatile conditions by pressure and flow recording and colour Doppler echocardiography in the 'mitral position' at rest and at exercise (cardiac output range 4-30 l/Min). In the steady state, significant differences were measured at peak flows of 30 l/min, with mean (s.d.) increasing pressure drops (mmHg) recorded at 3.48(0.13) (St. Jude Medical), 3.80(0.11) (Medtronic Parallel), 4.31(0.06) (ATS Medical) (P < 0.005), and 4.78(0.06) (Carbo Medics), (P < 0.005). The mean ratio of the closing volume to the stroke volume was comparable for all valves despite one faulty sample. In the pulsatile state the effective orifice area calculated by the Continuity and Gorlin equations decreased from 2.10(0.04) (ATS Medical), 1.95(0.05) (St. Jude Medical), 1.87(0.03) (Carbo Medics) to 1.67(0.02) (Medtronic Parallel) independently of method used. No significant difference was found in the mean ratio of the regurgitant volume to the stroke volume. The performance index, defined as the ratio of effective orifice area to geometric orifice area ranks the valves in the order ATS Medical (0.44), St. Jude Medical (0.43), Carbo Medics (0.41) and Medtronic Parallel (0.38). Regurgitation visible on colour Doppler echo was a mere consequence of the working principle of the bileaflet valves in the mitral position and was by no means hydrodynamically important nor representative of severe insufficiencies. Differences between the valve types were notable under severe conditions, such as high peak flow.

Clinical experience with the first 100 ATS heart valve implants.

Between May 1992 and March 1994, 100 consecutive patients had 119 new ATS mechanical bileaflet valves inserted (61 aortic, 50 mitral, eight tricuspid). The mean age of the patients was 63.7 (range 13-82) years. The follow-up period ranged from 5 to 27 months and was complete in all cases. Before surgery, 53 aortic valve patients were in New York Heart Association functional class III or higher. This improved to a mean of 1.3 postoperatively, all patients being in classes I or II. One patient died in hospital, and another 3 months after implantation (actuarial survival rate 98%). One patient had an embolic event 9 days after an aortic valve reoperation which caused a parietal infarction. One tricuspid valve blocked in the open position 6 weeks after implantation as a result of inadequate anticoagulation and was successfully unblocked after 2 days of intensive thrombolytic therapy. Patients were treated by mild anticoagulation without developing bleeding complications. Echocardiographic, transoesophageal and transthoracic valvular gradients compared favourably with the gradients reported in other mechanical valves (including small aortic valves). The haemodynamics were excellent without evidence of significant regurgitation. This was confirmed by an in vitro hydrodynamic evaluation of the valve using a pulse duplicator system. The valve closure caused little noise and was as a result well tolerated.

Toronto stentless aortic valve replacement in elderly patients.

From July 1992 to October 1994, we inserted new Toronto SPV stentless aortic heterografts (SJM Med. Inc., St Paul, Minneapolis, USA) in 40 of a series of 50 consecutive patients older than 70 years. The mean age was 75.7 years (range 70 - 86 years). All, except 4 patients, were pre-operatively in NYHA functional class III or higher. The aortic clamp time was significantly higher in the stentless groups (75 v. 53 minutes, P < 0.001). The average 25.5 mm size of the implanted valves stands in stark contract to the low body surface area (1.69 m2) of this patient groups. The surgeon's (in)experience was the major reason for the drawbacks (5/50) associated with a stentless procedures. The follow-up period ranged from 2 to 27 months and was complete in 100% of cases. We encountered 1 hospital death and no late deaths (97.5% actuarial survival). The mean NYHA class at follow-up was 1.5, and without exception patients were in class I or II. We noted one transient ischaemic attack immediately postoperatively and another later incident in a patient with a previous severe vascular history. With a low-intensity anticoagulation regiment for the first 3 months, there were two incidents of haemorrhaging necessitating premature anticoagulation withdrawal. Echocardiographic transthoracic valvular gradients compared favourably with the reported gradients of other biological valves, especially the smaller ones the significantly better haemodynamics were noted in most cases 6 months after implantation. Comparison of data with stented valves implanted during the same period indicates that the average size of the stentless valves was significantly higher (22.3 v. 25.5 mm, P < 0.001) in an equivalent population.

Removal of endocardial defibrillation leads.

Two patients, each with an endocardial defibrillation lead system (Endotak O62), required lead removal; one because of chronic lead infection and the second because of spurious shocks caused by lead insulation damage. Neither lead could be removed by simple traction. The defective lead was removed by a combination of catheterization techniques including a steerable ablation catheter and traction, both under general anesthesia. The lead with the insulation defect was rapidly removed with a locking stylet, suggesting that endocardial lead defibrillating leads can be removed similarly to pacemaker leads, thus avoid thoracotomy.