Guido Van Nooten

Variations of autonomic tone preceding onset of atrial fibrillation after coronary artery bypass grafting

Assessment of autonomic tone preceding the onset of atrial fibrillation (AF) after coronary artery bypass grafting (CABG) with heart rate variability was examined in 64 patients scheduled for elective CABG (days 2 to 5). Ninety-six-hour Holter tapes were analyzed in each patient and all events labeled by an experienced technician. The hour preceding AF was divided into 4 quarters (heart rate variability calculated per quarter) and compared with similar time episodes from the group without AF. Twenty-six of 64 patients (40%) had a total of 35 episodes. Only increased age (68+/-5 vs 62+/-9 years) and lower ejection fraction (66+/-16% vs 73+/-8%) were associated with an increased risk for AF. Before onset, a greater number of atrial premature complexes was observed. The standard deviation of all RR intervals (SDNN) showed an increase in the group with AF in the last 15 minutes (significant vs controls and within the AF group). The low-frequency/high-frequency ratio was significantly lower in patients in the first 30 minutes, followed by an increase mainly because the high-frequency spectrum became less important. Thus, initiation of postoperative AF is influenced by autonomic tone variations. A shift in the autonomic balance with a loss of vagal tone and a moderate increase in sympathetic tone are observed before the onset of AF compared with those in controls.

Comparison of the Hemodynamic and Thrombogenic Performance of Two Bileaflet Mechanical Heart Valves Using a CFD/FSI Model

The hemodynamic and the thrombogenic performance of two commercially available bileaflet mechanical heart valves (MHVs)--the ATS Open Pivot Valve (ATS) and the St. Jude Regent Valve (SJM), was compared using a state of the art computational fluid dynamics-fluid structure interaction (CFD-FSI) methodology. A transient simulation of the ATS and SJM valves was conducted in a three-dimensional model geometry of a straight conduit with sudden expansion distal the valves, including the valve housing and detailed hinge geometry. An aortic flow waveform (60 beats/min, cardiac output 4 l/min) was applied at the inlet. The FSI formulation utilized a fully implicit coupling procedure using a separate solver for the fluid problem (FLUENT) and for the structural problem. Valve leaflet excursion and pressure differences were calculated, as well as shear stress on the leaflets and accumulated shear stress on particles released during both forward and backward flow phases through the open and closed valve, respectively. In contrast to the SJM, the ATS valve opened to less than maximal opening angle. Nevertheless, maximal and mean pressure gradients and velocity patterns through the valve orifices were comparable. Platelet stress accumulation during forward flow indicated that no platelets experienced a stress accumulation higher than 35 dyne x s/cm2, the threshold for platelet activation (Hellums criterion). However, during the regurgitation flow phase, 0.81% of the platelets in the SJM valve experienced a stress accumulation higher than 35 dyne x s/cm2, compared with 0.63% for the ATS valve. The numerical results indicate that the designs of the ATS and SJM valves, which differ mostly in their hinge mechanism, lead to different potential for platelet activation, especially during the regurgitation phase. This numerical methodology can be used to assess the effects of design parameters on the flow induced thrombogenic potential of blood recirculating devices.

Tricuspid valve replacement: Postoperative and long-term results ☆ ☆☆ ★

A series of 146 consecutive patients who underwent tricuspid valve replacement at the University Brugmann Hospital between 1967 and 1987 was reviewed. Mean age at operation was 51.4 years (+/- 12.1 years). Different types of prostheses were implanted including porcine and bovine pericardial bioprostheses and older and bileaflet mechanical valves. Most patients were severely disabled by their cardiac disease before operation, with 30.1% in New York Heart Association functional class III and 69.9% in class IV. Operative mortality and hospital mortality rates (30 days) were high (16.4%). Incremental risk factors for hospital death included icterus (p < 0.005), preoperative hepatomegaly (p = 0.012), and New York Heart Association functional class IV (p = 0.013). Multivariate analysis only selected preoperative icterus (p < 0.01) as being independently significantly related to hospital mortality. The hospital survivors were followed up for a median of 94 months. A complete follow-up was available for all patients except two for 30 months or more. At 30 months the only two significant parameters were the type of myocardial protection (p = 0.024) and the year of operation (before 1977 or after [precardioplegia era or after], p = 0.011). There were 70 late deaths during the entire follow-up period. The univariate (log-rank statistics) incremental risk factor for late death was the type of tricuspid prosthesis (Smeloff-Cutter and Kay-Shiley versus St. Jude Medical versus bioprosthesis) (p = 0.04). A trend was observed for the type of operative myocardial protection (normothermia and coronary perfusion) (p = 0.06) and preoperative New York Heart Association functional class IV (p = 0.055). Actuarial survival was 74% at 60 months and 23.4% at 180 months. Cumulative follow-up added up to 1015 patient-years. In a more detailed analysis of the effect on survival of the type of tricuspid prosthesis, a significant difference was observed between the bioprostheses and some older mechanical prostheses (Smeloff-Cutter and Kay-Shiley) (p = 0.04) but not between the bioprostheses and the bileaflet valves (p = 0.15). When the follow-up period was stratified according to less than 7 years and more than 7 years of follow-up, no difference was observed for the first period, but for the late follow-up the new mechanical prostheses did better than the bioprostheses (p = 0.05), suggesting a degradation of the bioprostheses after 7 years and favoring mechanical prostheses for those patients with a good long-term prognosis.

Bypass versus drug-eluting stents at three years in SYNTAX patients with diabetes mellitus or metabolic syndrome.

BACKGROUND Diabetes mellitus increases adverse outcomes after coronary revascularization; however, the impact of metabolic syndrome is unclear. We examined the impact of diabetes and metabolic syndrome on coronary artery bypass graft surgery (CABG) and stenting outcomes to determine the optimal revascularization option for the treatment of complex coronary artery disease. METHODS Patients (n = 1,800) with left main or three-vessel disease or both were randomly allocated to treatment with a TAXUS Express(2) paclitaxel-eluting stent (PES) or CABG, and were included in predefined nondiabetic (n = 1,348) or diabetic subgroups (n = 452); 258 patients with diabetes also had metabolic syndrome. RESULTS Among diabetic patients, the 3-year major adverse cardiac and cerebrovascular event (MACCE) rate (22.9% CABG, 37.0% PES; p = 0.002) and revascularization rate (12.9% CABG, 28.0% PES; p < 0.001) were higher after PES treatment. Diabetes increased MACCE rates among PES-treated patients, but had little impact on results after CABG. Compared with CABG, PES treatment yielded comparable MACCE in diabetic patients (30.5% versus 29.8%, p =0.98) and nondiabetic patients (20.2% versus 20.3%, p =0.99) with low Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery (SYNTAX) study scores of 22 or less. For patients with SYNTAX Scores of 33 or greater, MACCE rates were lower with CABG (18.5% versus 45.9%, p < 0.001 diabetic; 19.8% versus 30.0%, p = 0.01 nondiabetic). Metabolic syndrome did not significantly predict MACCE or repeat revascularization. CONCLUSIONS These exploratory analyses suggest that among diabetic patients with complex left main or three-vessel disease, or both, 3-year MACCE is higher after PES compared with CABG. Although PES is a potential treatment option in patients with less complex lesions, CABG should be the revascularization option of choice for patients with more complex anatomic disease, especially with concurrent diabetes. Metabolic syndrome had little impact on 3-year outcomes.

Randomized Comparison of Stentless Versus Stented Valves for Aortic Stenosis Effects on Left Ventricular Mass

Background— Aortic valve replacement (AVR) is the established treatment for severe aortic stenosis. In response to the long-term results of aortic homografts, stentless porcine valves were introduced as an alternative low-resistance valve. We conducted a randomized trial comparing a stentless with a stented porcine valve in adults with severe aortic stenosis. Methods and Results— The primary outcome was change in left ventricular mass index (LVMI) measured by transthoracic echocardiography and, in a subset, by cardiovascular MR. Measurements were taken before valve replacement and at 6 and 12 months. Patients undergoing AVR with an aortic annulus ≤25 mm in diameter were randomly allocated to a stentless (n=93) or a stented supra-annular (n=97) valve. There were no significant differences in mean LVMI between the stentless versus stented groups at baseline (176±62 and 182±63 g/m2, respectively) or at 6 months (142±49 and 131±45 g/m2, respectively), although within-group changes from baseline to 6 months were highly significant. Changes in LVMI measured by cardiovascular MR (n=38) were consistent with the echo findings. There was a greater reduction in peak aortic velocity (P<0.001) and a greater increase in indexed effective orifice area (P<0.001) in the stentless group than in the stented group. There were no differences in clinical outcomes between the 2 valve groups. Conclusions— Despite significant differences in indexed effective orifice area and peak flow velocity in favor of the stentless valve, there were similar reductions in left ventricular mass at 6 months with both stented and stentless valves, which persisted at 12 months.

Successful management of a large pulmonary cement embolus after percutaneous vertebroplasty: a case report

Percutaneous vertebroplasty is increasingly used for the treatment of vertebral compression fractures. Local leakage of polymethylmethacrylate cement into the perivertebral space is a common complication, but important systemic effects have rarely been reported. The authors describe the case of a 52-year-old patient with central pulmonary embolism after percutaneous vertebroplasty of the eleventh thoracic vertebral body. The large cement embolus was removed from the right pulmonary artery with a hybrid technique combining an interventional catheter procedure with an open heart operation. The patient made an uneventful recovery. The authors review how appropriate arthroplasty techniques might minimize the risk of this dreadful complication.

O2 delivery and CO2 production during cardiopulmonary bypass as determinants of acute kidney injury: time for a goal-directed perfusion management?

IntroductionAcute kidney injury (AKI) is common after cardiac operations. There are different risk factors or determinants of AKI, and some are related to cardiopulmonary bypass (CPB). In this study, we explored the association between metabolic parameters (oxygen delivery (DO2) and carbon dioxide production (VCO2)) during CPB with postoperative AKI.MethodsWe conducted a retrospective analysis of prospectively collected data at two different institutions. The study population included 359 adult patients. The DO2 and VCO2 levels of each patient were monitored during CPB. Outcome variables were related to kidney function (peak postoperative serum creatinine increase and AKI stage 1 or 2). The experimental hypothesis was that nadir DO2 values and nadir DO2/VCO2 ratios during CPB would be independent predictors of AKI. Multivariable logistic regression models were built to detect the independent predictors of AKI and any kind of kidney function damage.ResultsA nadir DO2 level < 262 mL/minute/m2 and a nadir DO2/VCO2 ratio < 5.3 were independently associated with AKI within a model including EuroSCORE and CPB duration. Patients with nadir DO2 levels and nadir DO2/VCO2 ratios below the identified cutoff values during CPB had a significantly higher rate of AKI stage 2 (odds ratios 3.1 and 2.9, respectively). The negative predictive power of both variables exceeded 90%. The most accurate predictor of AKI stage 2 postoperative status was the nadir DO2 level.ConclusionsThe nadir DO2 level during CPB is independently associated with postoperative AKI. The measurement of VCO2-related variables does not add accuracy to the AKI prediction. Since DO2 during CPB is a modifiable factor (through pump flow adjustments), this study generates the hypothesis that goal-directed perfusion management aimed at maintaining the DO2 level above the identified critical value might limit the incidence of postoperative AKI.

Surgical treatment of impending paradoxical embolism through patent foramen ovale

We describe the case of a patient with deep venous thrombosis who had cerebral and extremity paradoxical emboli and an intracardiac thrombus crossing a patent foramen ovale identified by echocardiography. He was treated successfully with immediate intracardiac embolectomy and closure of the patent foramen ovale.

The initial experience with the ATS Medical mechanical cardiac valve prosthesis.

BACKGROUND From May 1994 through October 2000, a total of 1,146 patients underwent valve replacement with the ATS Medical mechanical cardiac valve prosthesis under a study protocol approved by international ethics committees (non-United States participants) or under a United States Food and Drug Administration-approved Investigational Device Exemption study. The study took place at 19 domestic and three international centers. METHODS As required by the Food and Drug Administrations Heart Valve Guidance Document, only isolated implants were included in the study (double-valve implants were excluded), with operative and follow-up data collected from each center. RESULTS Aortic valve replacement (AVR) was conducted in 801 patients (309 with coronary bypass) and mitral valve replacement (MVR) in 345 patients (78 with coronary bypass). Overall operative (< or = 30 days post implant) mortality was 2.1% (17 AVR = 2.1%, 7 MVR = 2.0%), 7 of which (AVR = 4, MVR = 3) were valve related. In 2,086 patient-years (1,459 AVR patient-years, 627 MVR patient-years) of follow-up, there were an additional 50 patient deaths of these, 18 were valve related, 9 due to anticoagulant related bleeding, 5 sudden/unexplained, and 1 each after stroke, thrombosis, prosthetic valve endocarditis, and thromboembolism. Late (>30 days post implant) valve-related complications included: transient and chronic thromboembolism (27 AVR (linearized rate 1.85%/patient-year) and 20 MVR (3.19%/patient-year), of which 11/47 (0.53%/patient-year) had chronic deficits, thrombosis (1 AVR = 0.07%/patient-year and 4 MVR = 0.64%/patient-year), paravalvular leak (10 AVR = 0.69%/patient-year and 8 MVR = 1.28%/patient-year), anticoagulant related hemorrhage (34 AVR = 2.33%/patient-year and 8 MVR = 1.28%/patient-year), prosthetic valve endocarditis (3 AVR = 0.21%/patient-year and 2 MVR = 0.32%/patient-year), and structural valve failure or dysfunction (0%). Echocardiographic gradients were proportional to valve size and did not significantly change over the follow-up period. CONCLUSIONS This study documented the ATS Medical mechanical cardiac valve prosthesis to be a valuable addition to the surgeons armamentarium in the treatment of cardiac valvular disease.

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 surgeons (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.