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A Bel

Publications and source records attributed to A Bel.

At least 19 recordsLinked to original sources

Automatic on-line electronic portal image analysis with a wavelet-based edge detector.

A fully automatic method for on-line electronic portal image analysis is proposed. The method uses multiscale edge detection with wavelets for both the field outline and the anatomical structures. An algorithm to extract and combine the information from different scales has been developed. The edges from the portal image are aligned with the edges from the reference image using chamfer matching. The reference is the first portal image of each treatment. The matching is applied first to the field and subsequently to the anatomy. The setup deviations are quantified as the displacement of the anatomical structures relative to the radiation beam boundaries. The performance of the algorithm was investigated for portal images with different contrast and noise level. The automatic analysis was used first to detect simulated displacements. Then the automatic procedure was tested on anterior-posterior and lateral portal images of a pelvic phantom. In both sets of tests the differences between the measured and the actual shifts were used to quantify the performance. Finally we applied the automatic procedure to clinical images of pelvic and lung regions. The output of the procedure was compared with the results of a manual match performed by a trained operator. The errors for the phantom tests were small: average standard deviation of 0.39 mm and 0.26 degrees and absolute mean error of 0.31 mm and 0.2 degrees were obtained. In the clinical cases average standard deviations of 1.32 mm and 0.6 degrees were found. The average absolute mean errors were 1.09 mm and 0.39 degrees. Failures were registered in 2% of the phantom tests and in 3% of the clinical cases. The algorithm execution is approximately 5 s on a 168 MHz Sun Ultra 2 workstation. The automatic analysis tool is considered to be a very useful tool for on-line setup corrections.

Automation↗

A computerized remote table control for fast on-line patient repositioning: implementation and clinical feasibility.

A computerized remote control for a Siemens ZXT treatment couch was implemented and its characteristics were investigated to establish its feasibility for on-line setup corrections, using portal imaging. Communication with the table was obtained by connecting it via a serial line to a work station. The treatment couch enables "goto" commands in the three main directions and around the isocenter. The accuracy of the movements after giving such a command was checked and the time for each movement was recorded. First, the movements into a single direction were studied (range of -4 to +4 cm and -4 degrees to +4 degrees). Each command was repeated four times. Second, the table was moved into the three main directions simultaneously. For this experiment a clinically relevant three-dimensional (3-D) normal distribution of shifts was used [N = 200, standard deviation (SD) 5 mm in the three main directions]. This latter experiment was done twice: without and with rotations (a distribution with SD 1 degrees). During the first experiment, with shifts into one direction, no systematic deviations were found. The overall accuracy of the shifts was 0.6 mm (1 SD) in each direction and 0.04 degrees (1 SD) for the rotations. The time required for a translation ranged between 4 and 13 s and for the rotation between 8 and 20 s. The second experiment with the 3-D distribution of setup errors yielded an error in the 3-D vector length equal to 0.96 mm (1 SD), independent of rotations. Shifts were performed in less than 11 s for 95% of the cases without rotations. When rotations were also performed, 95% of the movements finished in less than 16 s. In conclusion, the table movements are accurate and enable on-line setup corrections in daily clinical practice.

Feasibility Studies↗

Ministernotomy for aortic valve replacement: a study of the preliminary experience.

OBJECTIVE: The aim of the study was to evaluate the technical feasibility and the postoperative course of aortic valve replacement through a ministernotomy. SETTING: The Montreal Heart Institute and the Hôpital Lariboisière, Paris, France. DESIGN: A case series from 2 institutions. PATIENTS: Fifty-one patients who underwent aortic valve replacement through a ministernotomy. The sternal incision was started at the level of the sternal notch extending down to the third or fourth intercostal space with a transverse section of the sternum at this level on both sides or limited to the right side (inverted T or L incision). Thirty-nine patients had aortic stenoses, 6 patients were operated for aortic insufficiency and 6 had mixed disease. The mean (and standard deviation) preoperative left ventricular ejection fraction was 0.56 (0.17). MAIN OUTCOME MEASURES: Cardiac bypass time, complications and outcome. RESULTS: The patients received Carbomedics and St. Jude mechanical valves, Hancock and Carpentier-Edwards bioprostheses. Thirty-eight patients were administered antegrade and retrograde cardioplegia, 10 patients antegrade and 3 retrograde blood cardioplegia only. The mean (and standard error) cardiopulmonary bypass time and aortic cross-clamp time were 104 (38) minutes and 72 (16) minutes respectively. Two patients (4%) died and 2 patients (4%) showed evidence of a stroke after the procedure. Hospital stay averaged 8 (5) days. CONCLUSION: We conclude that aortic valve replacement can be done through a ministernotomy approach with perioperative results similar to those obtained through a conventional sternotomy.

Aged↗

Assessment of the uncertainties in dose delivery of a commercial system for linac-based stereotactic radiosurgery.

PURPOSE: Linac-based stereotactic radiosurgery (SRS) was introduced in our department in 1992, and since then, more than 200 patients have been treated with this method. An in-house-developed algorithm for target localization and dose calculation has recently been replaced with a commercially available system. In this study, both systems have been compared, and positional accuracy, as well as dose calculation, have been verified experimentally. METHODS AND MATERIALS: The in-house-developed software for target localization and dose calculation is an extension to George Sherouse's GRATIS(R) software for radiotherapy treatment planning, and has been replaced by a commercial (BrainSCAN version 3.1; BrainLAB, Germany) treatment planning system (TPS) for SRS. The positional accuracy for the entire SRS procedure (from image acquisition to treatment) has been investigated by treatment of simulated targets in the form of 0.2-cm lead beads inserted into an anthropomorphic phantom. Both dose calculation algorithms have been verified against manual calculations (based on basic beam data and CT data from phantom and patients), and measurements with the anthropomorphic phantom applying ionization chamber, thermoluminescent detectors, and radiographic film. This analysis has been performed on a variety of experimental situations, starting with static beams and simple one-arc treatments, to more complex and clinical relevant applications. Finally, 11 patients have been evaluated with both TPS in parallel for comparison and continuity of clinical experience. RESULTS: Phantom studies evaluating the entire SRS procedure have shown that a target, localized by CT, can be irradiated with a positional accuracy of 0.08 cm in any direction with 95% confidence. Neglecting the influence of dose perturbation when the beam passes through bone tissue or air cavities, the calculated dose values obtained from both TPSs agreed within 1% (SD 1%) for phantom and patient studies. The application of a one-dimensional path length correction for tissue heterogeneity influences the treatment prescription 4% on average (SD 1%), which is in compliance with theoretical predictions. The phantom measurements confirmed the predicted dose at isocenter within uncertainty for the different treatment schedules in this study. CONCLUSION: The full SRS procedure applied to an anthropomorphic phantom has been used as a comprehensive method to assess the uncertainties involved in dose delivery and target positioning. The results obtained with both TPSs are in agreement with AAPM Report 54, TG 42 and clinical continuity is assured. However, the use of a one-dimensional path length correction will result in an increase of 4% in dose prescription, which is slightly more than that predicted in the literature.

Algorithms↗

Characteristics and clinical application of a treatment simulator with Ct-option.

BACKGROUND AND PURPOSE: The integration of a scanner for computed tomography (CT) and a treatment simulator (Sim-CT, Elekta Oncology Systems, Crawley, UK) has been studied in a clinical situation. Image quality, hounsfield units (HU) and linearity have been evaluated as well as the implications for treatment planning. The additional dose to the patient has also been highlighted. MATERIAL AND METHODS: Image data is acquired using an array of solid state X-ray detectors attached externally to the simulator's image intensifier. Three different fields of view (FOV: 25.0 cm, 35.0 cm and 50.0 cm) with 0.2 cm, 0.5 cm and 1.0 cm slice thickness can be selected and the system allows for an aperture diameter of 92.0 cm at standard isocentric height. The CT performance has been characterized with several criteria: spatial resolution, contrast sensitivity, geometric accuracy, reliability of hounsfield units and the radiation output level. The spatial resolution gauge of the nuclear associates quality phantom (NAQP) as well as modulation transfer functions (MTF) have been applied to evaluate the spatial resolution. Contrast sensitivity and HU measurements have been performed by means of the NAQP and a HU conversion phantom that allows inserts with different electron densities. The computed tomography dose index (CTDI) of the CT-option has been monitored with a pencil shaped ionization chamber. Treatment planning and dose calculations for heterogeneity correction based on the Sim-CT images generated from an anthropomorphic phantom as well as from ten patients have been compared with similar treatment plans based on identical, yet diagnostic CT (DCT) images. RESULTS: The last row of holes that are resolved in the spatial resolution gauge of the NAQP are either 0.150 cm or 0.175 cm depending on the FOV and the applied reconstruction filter. These are consistent with the MTF curves showing cut-off frequencies ranging from 5.3 lp/cm to 7.1 lp/cm. Linear regression analysis of HU versus electron densities revealed a correlation coefficient of 0.99. Contrast, pixel size and geometric accuracy are within specifications. Computed tomography dose index values of 0.204 Gy/As and 0.069 Gy/As have been observed with dose measurements in the center of a 16 cm diameter and 32 cm diameter phantom, respectively for large FOV. Small FOV yields CTDI values of 0.925 Gy/As and 0.358 Gy/As which is a factor ten higher than the results obtained from a DCT under similar acquisition conditions. The phantom studies showed excellent agreement between dose distributions generated with the Sim-CT and DCT HU. The deviations between the calculated settings of monitor units as well as the maximum dose in three dimensions were less than 1% for the treatment plans based on either of these HU both for pelvic as well as thoracic simulations. The patient studies confirmed these results. CONCLUSIONS: The CT-option can be considered as an added value to the simulation process and the images acquired on the Sim-CT system are adequate for dose calculation with tissue heterogeneity correction. The good image quality, however, is compromised by the relative high dose values to the patient. The considerable load to the conventional X-ray tube currently limits the Sim-CT to seven image acquisitions per patient and therefore the system is limited in its capability to perform full three-dimensional reconstruction.

Computer Simulation↗

Clara's birth.

Advocacy for homebirth is based on the strong assumption that birthing is a physiological process and does not require medical interventions unless things turn "wrong." Let us assume that something might always go wrong, for instance during Clara's birth when the placenta was still retained after three hours. What needs to be done? The moment the midwife entered the house she was endowed with a responsibility for any problem caused by her failure to give proper guidance. With this weight on her shoulder, and according to her training and experience, there was no other way for her than to suggest an intervention regarding the placenta. The two midwives, B, and C., might not agree on risk estimations, the nature of the intervention, whether it should be performed at home or in a hospital. The estimation of abnormalities, evaluation of risks and the procedures with which to handle them are the main practical difference between classic obstetrics and non-interventionist midwifery--by analogy, between allopathy and naturopathy. The rest (positive thinking) is basically literature. A delivery will not remain normal just because we decide it "must" be physiological. Dr. Barua, a professor of obstetrics in Pondicherry, pointed out that normal deliveries are rare--fewer than 10 percent in South India. What we have instead is either pathological or "natural" deliveries in which regenerative processes take care of abnormal situations. Unless she has developed sensitive hands, a birth assistant or midwife must rely on monitoring procedures to evaluate deviations from the normal process. Even with the greatest care, these procedures are intrusive in that they disconnect the parturient from her own sensations. While successful unattended homebirth stories emphasise the extraordinary power and sensitivity of a birthing woman, the whole dream seems to collapse in abnormal or pathological cases. It would have collapsed for Sonia as well, had she not discarded negative suggestions. Dependency on medical experts is an alienation by which the patient is forced to tolerate what is not tolerable to her at a precise moment. The trauma of medicalized birth is not surprisingly associated with rape. It remains that the leitmotif in homebirth literature is more "empowerment," self assertion, militancy for the freedom of choice and ownership of her own body, than "self reliance" which involves a long-term sensitisation. Even outstanding essays a advocating non-medicalized birth may contain a sentence with implicit fear talk defusing the argument. For instance: "And if need be, [the midwife] can transport you to the hospital if you truly need the help that only modern obstetrics can provide...."] The sentence may be countereffective to a reader who is insecure about homebirth. The problem lies in the proximity of "truly" and "only." It was indeed the writer's intention to emphasise "truly" with an interrogative connotation: "Are you sure you need it?" However, the effect is overruled by the assertive strength of "only." The reader's unconscious reading may be that, truly, she needs the help that only modern obstetrics can provide. This is an example of negative suggestions conveyed by confidence building talk about health and pregnancy. Another example was Denis and Sonia's obsession with the placenta retention problem that had been causally exposed by midwife B. Why should her empowerment end suddenly when there is a life threatening complication during the delivery? If the pregnant woman claims a fundamental right to choose her way of birthing in uncomplicated cases, she needs even more self determination when she is in real danger. This paradox is striking evidence that the common sense attitude toward danger is affected by the "allopathic mind." It sets up an insurmountable barrier between the physiological and the pathological, whereby symptoms are failures of the normal regenerative processes. Hence, testimonies of women feeling that their bodies "b

Female↗

Electronic portal imaging with on-line correction of setup error in thoracic irradiation: clinical evaluation.

PURPOSE: To analyze setup errors and the feasibility of their on-line correction using electronic portal imaging in the irradiation of lung tumors. METHODS AND MATERIALS: Sixteen patients with lung cancer were irradiated through opposed anteroposterior fields. Localization images of anteroposterior fields were recorded with an electronic portal imaging device (EPID). Using an in-house developed algorithm for on-line comparison of portal images setup errors were measured and a correction of table position was performed with a remote couch control prior to treatment. In addition, residual errors were measured on the EPID verification image. Global and individual mean and standard deviation of setup errors were calculated and compared. The feasibility of the procedure was assessed measuring intra- and interobserver variability, influence of organ movement, reproducibility of error measurement, the extra time fraction needed for measuring and adjusting and the fraction of dose needed for imaging. RESULTS: In two setups the procedure could not be finished normally due to problems inherent to the procedure. The reproducibility, intraobserver variability, and influence of organ movements were each described by a distribution with a mean value less than or equal to 1 mm and a standard deviation (SD) of less than 1.5 mm. The interobserver variability showed to be a little bit larger (mean: 0.3 mm, SD: 1.7 mm). The mean time to perform the irradiation of the anteroposterior field was 4 +/- 1 min. The mean time for the measurement and correction procedure approximated 2.5 min. The mean extra time fraction was 65 +/- 24% (1 SD) with more than half of this coming from the error measurement. The dose needed for generation of EPID images was 5.9 +/- 1.4% of total treatment dose. The mean and SD of setup errors were, respectively, 0.1 and 4.5 mm for longitudinal and -2.0 and 5.7 mm for transversal errors. Of 196 measured translational errors 120 (61%) exceeded the adjustment criteria. For individual patients systematic and random setup errors can be as high as, respectively, 15.8 and 7.5 mm. Mean residual error and SD were for longitudinal direction 0.08 and 1.2 mm and for transversal direction -0.9 and 1.0 mm (pooled data). For individuals, the mean residual errors were smaller than 1 mm, with a typical SD per patient of less than 2 mm. CONCLUSION: Setup errors in thoracic radiation therapy are clinically important. On-line correction can be performed accurately with an objective measurement tool, although this prolongs the irradiation procedure for one field with 65%.

Algorithms↗

Inhibition of the pacemaker current: a bradycardic therapy for off-pump coronary operations.

BACKGROUND: The accurate performance of coronary anastomoses on the beating heart requires some form of myocardial immobilization that can be achieved pharmacologically. Different classes of drugs can be used to induce bradycardia, but the most effective in this setting of off-pump operation has not yet been determined. METHODS: Fifty-six isolated buffer-perfused rabbit hearts were divided into seven equal groups. Control hearts were continuously perfused throughout the experimental time course. A second group of hearts underwent 60 minutes of potassium arrest (at 37 degrees C) followed by 1 hour of reperfusion. The following pharmacologic approaches were tested in the remaining five groups: short-acting beta-blockade (esmolol, 6 x 10(-3) mol/L and 3 x 10(-4) mol/L), opening of adenosine triphosphate-dependent potassium channels (nicorandil, 10(-3) mol/L and 10(-5) mol/L), and inhibition of the pacemaker current, which largely accounts for the diastolic depolarization of sinoatrial node cells (S 16257-2, 3 x 10(-6) mol/L). Each drug was infused at a constant rate for 60 minutes, after which hearts were perfused for 1 additional hour with drug-free buffer. Heart rate and isovolumic measurements of function and coronary flow were serially taken during and after drug infusion. RESULTS: The worst recovery of systolic and, moreover, diastolic function was yielded by potassium arrest. Neither esmolol nor nicorandil was able to induce a significant bradycardia. However, nicorandil did not impair function which, conversely, was markedly depressed after esmolol therapy. Significant bradycardia (p < 0.0001 versus corresponding baseline values and versus all other groups) was only achieved with pacemaker current inhibition, which was otherwise associated with an excellent preservation of contractility, diastolic function, and coronary flow. CONCLUSIONS: Inhibition of the pacemaker current seems to be an effective approach for inducing intraoperative bradycardia without compromising left ventricular function or flow.

Adrenergic beta-Antagonists↗

Nonpenetrating stapling: a valuable alternative for coronary anastomoses?

BACKGROUND: The safe development of minimally invasive coronary artery bypass operations might require alternatives to conventional suture-based anastomotic techniques. In this setting, nonpenetrating stapling is an attractive option because of its simplicity of use and potential for improved endothelial preservation. METHODS AND RESULTS: In the experimental part of this study, porcine internal mammary arteries were anastomosed to left anterior descending coronary arteries using either an 8-0 polypropylene running suture or nonpenetrating microclips (7 anastomoses in each group). The endothelium-dependent relaxations to bradykinin of the arterial rings bearing the anastomosis and of noninstrumented rings were compared in organ chamber experiments. There were no significant differences in maximal relaxations (mean +/- SEM) between the microclipped and sutured anastomoses (81%+/-7% versus 74%+/-10%), which were both significantly lower than those of control coronary rings (98%+/-2%, p = 0.001 versus the two anastomosed groups). Histologic examination showed a comparable preservation of the coronary and graft endothelium with both techniques. The clinical part of the study comprised 7 patients in whom the left internal mammary artery was conventionally sutured to the left anterior descending whereas 13 saphenous vein grafts were anastomosed to their target vessels by nonpenetrating staples. There were no clip-related complications. An angiographic assessment of the venous grafts was performed within 10 days postoperatively in all patients. One graft is presumably occluded. The 12 remaining conduits were patent with stapled anastomoses featuring a widely open "shark-mouth" configuration. CONCLUSIONS: These preliminary data suggest that non-penetrating stapling is an easy-to-use technique that competes well with conventional suturing, at least in terms of immediate results. Further studies are warranted to better define its potential place within the armamentarium of minimally invasive coronary artery bypass techniques.

Aged↗

Microprocessor controlled limitation system for a stand-alone freely movable treatment couch.

Because of the capability of free movement in the treatment room, we recently introduced a Hercules treatment couch on one of our linear accelerators. One of the advantages of this couch is that it allows for a more flexible way of patient setup and that it can be moved entirely out of the way to enable treatment with a hospital bed. A disadvantage, however, is that the couch can hit a wall or a cover of the accelerator accidentally. A limitation system has been developed to protect both the table and the accelerator against such collisions.

Algorithms↗

Differential regulation of glutathione by oxidants and dexamethasone in alveolar epithelial cells.

We studied the regulation of GSH and the enzymes involved in GSH regulation, gamma-glutamylcysteine synthetase (gamma-GCS) and gamma-glutamyl transpeptidase (gamma-GT), in response to the oxidants menadione, xanthine/xanthine oxidase, hyperoxia, and cigarette smoke condensate in human alveolar epithelial cells (A549). Menadione (100 microM), xanthine/xanthine oxidase (50 microM/10 mU), and cigarette smoke condensate (10%) exposure produced increased GSH levels (240 +/- 6, 202 +/- 12, and 191 +/- 2 nmol/mg protein, respectively; P < 0.001) compared with the control level (132 +/- 8 nmol/mg protein), which were associated with a significant increase in gamma-GCS activity (0.18 +/- 0.006, 0.16 +/- 0.01, and 0.17 +/- 0. 008 U/mg protein, respectively; P < 0.01) compared with the control level (0.08 +/- 0.001 U/mg protein) at 24 h. Exposure to hyperoxia (95% O2) resulted in a time-dependent increase in GSH levels. gamma-GCS activity increased significantly at 4 h (P < 0.001), returning to control values after 12 h of exposure. Dexamethasone (3 microM) exposure produced a significant time-dependent decrease in the levels of GSH and gamma-GCS activity at 24-96 h. The activity of gamma-GT did not change after oxidant treatment; however, it was decreased significantly by dexamethasone at 24-96 h. Thus oxidants and dexamethasone modulate GSH levels and activities of gamma-GT and gamma-GCS by different mechanisms. We suggest that the increase in gamma-GCS activity but not in gamma-GT activity may be required for the increase in intracellular GSH under oxidative stress in alveolar epithelial cells.

Cell Line↗

[Coronary surgery on the beating heart under extracorporeal circulation in high-risk patients. An acceptable compromise?].

Coronary artery surgery with cardioplegia in high risk patients carries a risk of myocardial ischaemia and, without cardiopulmonary bypass, is not always technically feasible. The authors assessed an alternative, surgery on the beating heart with haemodynamic assist by cardiopulmonary bypass in 43 consecutive patients with poor left ventricular function (mean ejection fraction: 0.26), evolving myocardial ischaemia or acute myocardial infarction, old age (mean: 79.5 years) and comorbid conditions. Results were assessed mainly on clinical criteria. In addition, 9 patients had pre- and post-cardiopulmonary bypass measurements of markers of myocardial ischaemia (troponine Ic) and systemic inflammation (interleukines 6 and 10, elastase). In 6 cases, right atrial biopsy was analysed for expression of messenger ribonucleic acid coding for heat shock protein (HSP) 70; the data were compared with those of patients operated under warm blood cardioplegia. There was one cardiac death and one myocardial infarction. Myocardial conservation was confirmed by the minimal increase in troponine Ic levels and the significant increase in HSP 70 in RNA suggesting myocardial adaptation to stress. On the other hand, the minimal concentrations of mediators of inflammation were not significantly changed. In selected high risk patients, coronary revascularisation on the beating heart under cardiopulmonary bypass could be a valuable alternative. It conserves the potentially deleterious effects of cardiopulmonary bypass but peroperative global myocardial ischaemia, an important factor in the aggressivity of cardiac surgery, is eliminated.

Adult↗

Initial experience with intensity-modulated conformal radiation therapy for treatment of the head and neck region.

PURPOSE: The efficacy of a conventional, noninvasive fixation technique in combination with a commercially available system for conformal radiotherapy by intensity modulation of the treatment beam has been studied. METHODS AND MATERIALS: A slice-by-slice arc-rotation approach was used to deliver a conformal dose to the target and patient fixation was performed by means of thermoplastic casts. Eleven patients have been treated, of which 9 were for tumors of the head and neck region and 2 were for intracranial lesions. A procedure for target localization and verification of patient positioning suitable for this particular treatment technique has been developed based on the superposition of digitized portals with plots generated from the treatment-planning system. A dosimetric verification of the treatment procedure was performed with an anthropomorphic phantom: both absolute dose measurements (alanine and thermoluminescent detectors) and relative dose distribution measurements (film dosimetry) have been applied. The dose delivered outside the target has also been investigated. RESULTS: The dose verification with the anthropomorphic phantom yielded a ratio between measured and predicted dose values of 1.0 for different treatment schedules and the calculated dose distribution agreed with the measured dose distribution. Day-to-day variations in patient setup of 0.3 cm (translations) and 2.0 degrees (rotations) were considered acceptable for this particular patient population, whereas the verification protocol allowed detection of 0.1 cm translational errors and 1.0 rotational errors. CONCLUSIONS: The noninvasive fixation technique in combination with an adapted verification protocol proved to be acceptable for conformal treatment of the head and neck region. Dose measurements, in turn, confirmed the predicted dose values to the target and organs at risk within uncertainty. Daily monitoring becomes mandatory if an accuracy superior to 0.1 cm and 1.0 degree is required for patient setup.

Brain Neoplasms↗

On-pump, beating-heart coronary artery operations in high-risk patients: an acceptable trade-off?

BACKGROUND: Current cardioplegic techniques do not consistently avoid myocardial ischemic damage in high-risk patients undergoing coronary artery bypass grafting. Alternatively, revascularization without cardiopulmonary bypass is not always technically feasible. We investigated whether an intermediary approach based on maintenance of a beating heart with cardiopulmonary bypass support but without aortic cross-clamping might be an acceptable trade-off. METHODS: Thirty-seven consecutive patients underwent coronary artery bypass grafting (with an average of two grafts per patient) in a pump-supported, non-cross-clamped beating heart. Inclusion criteria were poor left ventricular function (18 patients; mean ejection fraction, 0.25), evolving myocardial ischemia or infarction (11 patients, 5 of whom were in cardiogenic shock), and advanced age (3 patients; mean age 79.5 years) with comorbidities. Results were assessed primarily on the basis of clinical outcome. In addition, measurements of plasma levels of markers of myocardial damage (troponin Ic) and systemic inflammation (interleukin-6, interleukin-10, elastase) were done in 9 patients before and after bypass. In 6 patients, right atrial biopsy specimens were taken before and after bypass and processed by Northern blotting for the expression of messenger ribonucleic acid coding for the cardioprotective heat-shock protein 70. These biologic data were compared with those from control patients who underwent warm cardioplegic arrest within the same time span. RESULTS: There was one cardiac-related death (2.7%), one Q-wave myocardial infarction, and no strokes. Four other deaths occurred from noncardiac causes, yielding an overall mortality rate of 13.5%. Limitation of myocardial injury was demonstrated by the minimal increase in postoperative troponin Ic levels (3.3 +/- 1.0 micrograms/L versus 6.6 +/- 1.5 micrograms/L in controls; p < 0.05) and the finding that heat-shock protein 70 messenger ribonucleic acid levels (expressed as a percentage of an internal standard) were significantly increased after bypass compared with pre-bypass values (279% +/- 80% versus 97% +/- 21%; p < 0.05). In the control group (cardioplegia), end-arrest values of heat-shock protein 70 messenger ribonucleic acid were not significantly changed from baseline (148% +/- 49% versus 91% +/- 29%), a finding suggesting a defective adaptive response to surgical stress. Conversely, peak levels of inflammatory mediators were not significantly different between the two groups. The eight grafts to the left anterior descending coronary artery that were assessed angiographically, by transthoracic Doppler echocardiography, or both methods were patent with satisfactory anastomoses. CONCLUSIONS: In select high-risk patients, on-pump, beating-heart coronary artery bypass grafting may be an acceptable trade-off between conventional cardioplegia and off-pump operations. It is still associated with the potentially detrimental effects of cardiopulmonary bypass but eliminates intraoperative global myocardial ischemia.

Adult↗

Failure of preconditioning to improve postcardioplegia stunning of minimally infarcted hearts.

BACKGROUND: Ischemic preconditioning is an effective means of reducing myocardial infarct size, but its ability to attenuate stunning after an episode of surgically relevant global ischemia remains elusive. Likewise, the role played by adenosine in this setting has not been established conclusively. This study was designed to address these two issues. METHODS: Thirty isolated, crystalloid-perfused rabbit hearts were subjected to 60 minutes of normothermic potassium arrest and 60 minutes of reperfusion. They were divided into three equal groups. The first group had no prearrest intervention and served as a control. In the second group, ischemic preconditioning was achieved with 5 minutes of zero-flow ischemia followed by 5 minutes of buffer reperfusion before arrest. In the third group, the hearts were first infused for 5 minutes with the nucleoside transport inhibitor draflazine (10(-6) mol/L), the efficacy of which was demonstrated by reversal of the normally high inosine to adenosine ratio in the coronary effluent. These hearts subsequently were given 2 additional minutes of ischemic (zero-flow) preconditioning followed by 5 minutes of reperfusion before arrest. During reperfusion, function was measured serially under isovolumic conditions. Myocardial necrosis was estimated from the release of creatine kinase after the initial 5 minutes of reflow, and the planimetrically determined extent of infarction was determined by triphenyltetrazolium chloride staining. RESULTS: Baseline hemodynamic data were comparable among the three groups. Neither ischemic preconditioning alone nor ischemic preconditioning with draflazine-induced enhancement of endogenous adenosine levels improved postischemic recovery of function over that seen in control, untreated hearts. These results correlated with a minimal amount of infarction in the control group (on average, <10% of the left ventricle), which was not reduced further by either preconditioning regimen. CONCLUSIONS: These data support the idea that, in the absence of substantial necrosis, ischemic preconditioning does not ameliorate postischemic stunning, which leads to the question of its usefulness in clinical cardiac operations. Although, in this model, protection was not potentiated by increasing endogenous concentrations of adenosine, it remains a worthwhile goal to identify the final effectors of the signaling pathway accounting for the otherwise demonstrated cardioprotective effects of preconditioning because of the potential for these mediators to act as effective antiischemic agents.

Adenosine↗

Warm blood cardioplegia in high risk patients.

OBJECTIVE: Despite overall good clinical results, cardiac surgery in high risk patients, such as those with poor left ventricular function or heavily hypertrophied myocardium, is still challenging. This study was designed to assess the efficacy of warm blood cardioplegia (WBC) in these two subgroups of patients. METHODS: Fifty-two patients, with an ejection fraction less than 50%, who underwent surgical revascularization, and 36 patients, with marked left ventricular hypertrophy (LVH), who were operated on for aortic valve replacement (AVR), were consecutively studied. All of them received continuous retrograde 'warm' blood cardioplegia. Results were assessed on clinical outcomes and compared with those predicted from a risk-stratifying index which has been previously validated in a large multicenter population-based study (Ontario score). RESULTS: For cardiac revascularization, the rates of overall hospital mortality, Q-wave infarctions and inotropic use were respectively 5.8%, 9.6% and 21.1%, comparing favorably with those of the Ontario Group. For aortic valve replacement, the incidence of hospital mortality and Q-wave infarction was 2.8%. CONCLUSIONS: By virtue of the study design, these data cannot conclusively establish the superiority of warm blood cardioplegia over other methods of myocardial protection. However, they support the safety of this technique, and suggest that these subgroups of high risk patients might represent the elective indication for aerobic arrest.

Aged↗

[Valvular homografts].

Renewed interest in heart valve homografts is related to recent advances in viability. Increased viability is achieved by collecting explanted hearts from multi-organ donors and cryopreservation. Right access is usually used in case of hereditary cardiopathy to resect or repair the aortic, mitral and tricuspid valves. Life-long anticoagulant treatment can thus be avoided. Current mid-term and long-term results are very promising.

Heart Valve Diseases↗