Estimation of the frequency of involuntary infertility on a nation-wide basis.

BACKGROUND: Assessing couple fecundity on a nation-wide basis without excluding couples who eventually remain infertile is challenging. Our aim was to describe couple fecundity (in terms of frequency of involuntary infertility) among the general population living in France. METHODS: We used a current-duration design. A random sample of 64 262 households was selected in 2007-2008, allowing us to identify 15 810 women aged 18-44 years. Eligible women (n= 1089) were those having regular sexual intercourse with a male partner, not using any method of contraception and not having delivered in the previous 3 months. These women reported information on the current duration of unprotected intercourse (CDUI, the time elapsed between the start of the period of unprotected intercourse and the time of inclusion in the study). The CDUI distribution was used to estimate the frequency of involuntary infertility, using a newly developed statistical technique that does not require couples to be followed up until the end of the period of unprotected intercourse. RESULTS: CDUI was defined for 867 women. An estimated 46% of couples had no detected pregnancy conceived during the first 6 months of unprotected intercourse [95% confidence interval (CI), 36-56%]. The proportions of couples with no detected pregnancy within 12 and 24 months were 24% (19-30%) and 11% (8-14%), respectively. CONCLUSIONS: These results constitute one of the few descriptions of the fecundity of a nation-wide representative sample of couples from the general population, not limited to couples who eventually conceived or to those resorting to medical help.

Transoesophageal echocardiographic monitoring during paediatric cardiac surgery: obtainable information and feasibility in 532 children.

BACKGROUND: We hypothesized that transoesophageal echocardiography (TOE) performed by the anaesthesiologists would be beneficial for monitoring purposes during paediatric cardiac surgery. We present the results for the first 5 years in 532 consecutive children. METHODS: The probe was successfully inserted in 99% of cases and remained in the oesophagus for 211 min on average (range 10-555 min). RESULTS: Insignificant valve leak, single- or biventricular failure and volume depletion were the most common new findings due to TOE. Changes in inotropic strategy and volume replacement were the most frequent interventions. In 45% of the cases, new information was disclosed and, in a total of 8% of cases, decisive information was provided. Except for tracheal extubation in one child who was uneventfully reintubated, no severe complications were identified. CONCLUSIONS: These data stress the safety and ease of performing TOE in children undergoing cardiac surgery. There is evidence for benefit from TOE findings to potentially enhance the therapeutic basis.

Tissue injury and the inflammatory response to pediatric cardiac surgery with cardiopulmonary bypass: a descriptive study.

BACKGROUND: There are few detailed descriptions of the inflammatory response to cardiac surgery with cardiopulmonary bypass (CPB) in children beyond 24 h postoperatively. This is especially true for the antiinflammatory cytokines and the extent of tissue injury. The aim of the current study was to describe the inflammatory and injury responses in uncomplicated pediatric cardiac surgery with CPB, where methylprednisolone and modified ultrafiltration (MUF) were used. METHODS: Blood samples were collected up to 48 h postoperatively. Cytokines (tumor necrosis factor-alpha and interleukin-6, -1beta, -10, and -1ra), complement (C3d and C4d) and coagulation system (prothrombin activation fragments 1 and 2 and antithrombin III) activation, neutrophil elastase, and the resulting tissue injury (creatine kinase, lactate dehydrogenase, alanine transaminase, amylase, and gamma-glutamyl transferase) were measured. RESULTS: The proinflammatory cytokine release varied widely, in contrast to a clear-cut antiinflammatory response. Cytokine concentrations did not decrease immediately after MUF, and no rebound increases later in the postoperative period were observed. The coagulation system, but not complement, was activated. There was a late release of C-reactive protein. Tissue injury could be quantified biochemically without evidence of hepatic or pancreatic dysfunction. CONCLUSION: In this group of uncomplicated subjects, the antiinflammatory cytokine and tissue injury responses were well defined, in contrast to a variable proinflammatory cytokine release. This was accompanied by activation of the coagulation system but not of complement. Concentrations of inflammatory mediators did not decrease immediately after MUF, and there was no evidence for rebound release later in the postoperative period.

Improvement in growth, and levels of insulin-like growth factor-I in the serum, after cavopulmonary connections.

INTRODUCTION: The total cavopulmonary connection, and the bidirectional Glenn anastomosis, are widely used for palliation of patients with complex functionally univentricular hearts. Little attention has been paid to the potential for postoperative growth in children after these operations, which are now performed at increasingly younger age. MATERIAL AND RESULTS: Physical growth, and levels of insulin-like growth factor I in the serum, were measured in 20 patients, aged 11.5 +/- 5.6 years, 2 (0.5-6) years after a total cavopulmonary connection in 12, or a Glenn anastomosis in 8. All patients were in functional class I or II of the categorisation of the New York Heart Association, with excellent haemodynamic and angiographic findings. None of the patients had clinical signs of protein losing enteropathy. Controls included 33 healthy children, aged 11.5 +/- 2.7 years. Preoperatively, the mean Z-scores for weight and height were negative, -1.1 +/- 0.8 and -0.5 +/- 1.5. At follow-up, both parameters had improved significantly by 1.1 +/- 0.9 and 0.8 +/- 1.2 percentiles, and Z-scores were comparable between the two groups (p=0.81 for weight and p=0.88 for height). No correlations were found between haemodynamics and the improvement in growth noted during follow-up. Increases equal to, or greater than 2 standard deviations for weight and height were seen only in children undergoing surgery before the age of 5 years. A significant correlation between age at operation and improvement in growth, however, could not be found. Levels of growth factor measured in the serum were not statistically different from levels in healthy children for either group of patients (p=0.07 for girls and p=0.37 for boys). CONCLUSION: Physical growth improved significantly following the surgical procedures. The concentrations of the growth factor measured in the serum were not different from levels in healthy children, suggesting normal nutritional status in both palliative situations.

Neurohormonal activation late after cavopulmonary connection.

OBJECTIVE: To determine whether patients with cavopulmonary connection have higher levels of vasoactive/water-salt regulating hormones and if so, whether hormone levels are related to postoperative haemodynamics and postoperative follow up. DESIGN: Cross sectional study. SETTING: University hospital. PATIENTS: 20 patients (New York Heart Association functional class I-II), mean age 11 years (range 4 to 22), were studied at a mean of 2 years (0.5 to 6) after a total cavopulmonary connection (TCPC, n = 12) or a bidirectional Glenn anastomosis (BDG, n = 8). INTERVENTIONS: Cardiac catheterisation was performed and blood samples were drawn. Control blood samples were drawn from 33 healthy children, mean age 12 years (6 to 16). MAIN OUTCOME MEASURES: Plasma levels of angiotensin II, renin, aldosterone, arginine, vasopressin, atrial natriuretic factor (ANF), brain natriuretic peptide (BNP). RESULTS: All neurohormones were significantly increased in both TCPC and BDG patients (p < 0. 05), with a fourfold increase in angiotensin II, renin, and aldosterone, and a twofold increase in vasopressin, ANF, and BNP (compared with healthy controls). There was no correlation between haemodynamic variables and hormone levels. Angiotensin II and renin were inversely correlated with time to follow up. All subjects over 15 years (n = 5) had normal neurohormonal levels. CONCLUSIONS: Neurohormones were raised for years after successful cavopulmonary operations but lower levels were observed with time on follow up. This supports the hypothesis that neurohormonal activation is primarily related to altered postoperative physiology and that adaptation takes place over time.

[Pediatric heart surgery]. / Børnehjertekirurgi.

Surgery for congenital heart defects has since its beginnings fifty years ago evolved from being palliative to corrective in many cases. Surgery for the more simple defects is now performed with low surgical mortality and excellent prognoses, but the mortality for some of the more complex defects is still high, and the treatment regarded as palliative. The principles for and the results of the surgical treatment of some more complex defects are reviewed. The importance of follow-up is emphasized. Future possibilities are discussed.

[Pediatric heart surgery]. / Børnehjertekirurgi.

Surgery for congenital heart defects has since its beginnings fifty years ago evolved from being palliative to corrective in many cases. Surgery for the more simple defects is now performed with low surgical mortality and excellent prognoses, but the mortality for some of the more complex defects is still high, and the treatment regarded as palliative. The principles for and the results of the surgical treatment of some more complex defects are reviewed. The importance of follow-up is emphasized. Future possibilities are discussed.

Pulmonary and caval flow dynamics after total cavopulmonary connection.

OBJECTIVE: To assess flow dynamics after total cavopulmonary connection (TCPC). DESIGN: Cross-sectional study. SETTING: Aarhus University Hospital. PATIENTS: Seven patients (mean age 9 (4-18) years) who had previously undergone a lateral tunnel TCPC mean 2 (0. 3-5) years earlier. INTERVENTIONS: Pressure recordings (cardiac catheterisation), flow volume, and temporal changes of flow in the lateral tunnel, superior vena cava, and right and left pulmonary arteries (magnetic resonance velocity mapping). RESULTS: Superior vena cava flow was similar to lateral tunnel flow (1.7 (0.6-1.9) v 1. 3 (0.9-2.4) l/min*m2) (NS), and right pulmonary artery flow was higher than left pulmonary artery flow (1.7 (0.6-4.3) v 1.1 (0.8-2. 5) l/min*m2, p < 0.05). The flow pulsatility index was highest in the lateral tunnel (2.0 (1.1-8.5)), lowest in the superior vena cava (0.8 (0.5-2.4)), and intermediate in the left and right pulmonary arteries (1.6 (0.9-2.0) and 1.2 (0.4-1.9), respectively). Flow and pressure waveforms were biphasic with maxima in atrial systole and late ventricular systole. CONCLUSIONS: Following a standard lateral tunnel TCPC, flow returning via the superior vena cava is not lower than flow returning via the inferior vena cava as otherwise seen in healthy subjects; flow distribution to the pulmonary arteries is optimal; and some pulsatility is preserved primarily in the lateral tunnel and the corresponding pulmonary artery. This study provides in vivo data for future in vitro and computer model studies.

Tetralogy of Fallot. A population-based study of epidemiology, associated malformations and survival in western Denmark 1984-1992.

The study describes the epidemiology and mortality of tetralogy of Fallot (TOF) in a population-based study in Western Denmark. Ninety-two infants with TOF were born during 1984-1992. Prevalence was 3.01 per 10,000 livebirths. Karyotype anomalies were present in 12 (13%) and extracardiac malformations in 16 (17%) of the infants. Down syndrome, cleft palate, cleft lip and palate and combined skeletal, gastrointestinal and renal lesions (VACTERL association) were prevalent. Twenty-four infants died (26% of total), 13 (54%) of the deaths occurring during the first year of life. Mortality was significantly increased in infants with extracardiac malformations (50% vs 19%, p < 0.05). Eighteen deaths (75% of total deaths) occurred before corrective surgery and 7 of these deaths were sudden. Extracardiac malformation(s) in infants with TOF is a significant risk factor for death. The study stresses the importance of population-based studies for the assessment of mortality from congenital heart malformations. Overall mortality may be very different from mortality related to cardiac surgery.

Myocardial structure as a determinant of pre- and postoperative ventricular function and long-term prognosis after valve replacement for aortic stenosis.

BACKGROUND: Long-term results after aortic value replacement for aortic stenosis can be correlated to a cardiac-related pre-operative risk profile. This predictability indicates that there is a common basis in subtle or overt structural abnormalities of left ventricular myocardium. METHODS AND RESULTS: Forty-nine patients aged 24-82 (mean 61) years, with aortic stenosis had a full wall thickness transmural biopsy of the left ventricular antero-lateral free wall during aortic valve replacement. Echocardiography and radionuclide ventriculography were performed prior to, and 18 months (n = 41) after, the operation. Postoperative follow-up to a maximum of 7.7 years was 100% complete. Pre-operatively, all patients had an increase in both the left ventricular mass index (202 +/- 67 g.m-2) and the muscle cell diameter (41 +/- 8 microns); other morphological data included a muscle cell nucleus volume of 752 +/- 192 microns3, a muscle cell mass index of 163 +/- 54.m-2, and a fibrous tissue mass index of 39 +/- 16 g.m-2. Patients with a pre-operative episode of clinical left ventricular failure (n = 19) had significantly greater morphological variables than those without. Pre-operative ejection fraction and other measures of systolic function correlated inversely with the morphological data, except for the fibrous tissue mass index; diastolic function indices correlated inversely with all the morphological variables. At the 18-month re-study, the same general picture was noted, but with an underlying strengthening, especially of the muscle cell mass index. Overall, the mass index dropped to 152 +/- 51 g.m-2 (P < 0.0001), but in 17% of the patients it became normal; the mass index at 18 months was directly correlated to morphological variables. A high muscle cell nucleus volume was identified as an independent predictor of early and late mortality. CONCLUSIONS: Abnormalities of the hypertrophied left ventricular muscle cell and the degree of muscle hypertrophy are, to some degree, underlying determinants of pre-operative symptomatology, pre- and postoperative ventricular function, and early and late mortality after valve replacement for aortic stenosis. Incomplete hypertrophy impaired results, was related to pre-operative myocardial structural abnormalities.

[Mortality and worsening of prognosis for patients with aortic stenosis while on the waiting list]. / Mortalitet og prognoseforringelse for patienter med aortastenose på kirurgisk venteliste.

In a prospective study, 99 consecutive patients with an operative indication due to severe aortic stenosis (AS) were put on a surgical waiting list. The waiting time to aortic valve replacement (AVR) averaged 6.3 months (0.5-19 months). There were 58 men and 41 women with a mean age of 61 years (21-82 years). The patients were divided into three groups: group 1 (N = 81) with an uneventful stay on the waiting list; group 2 (N = 11) with significant worsening of a prognostic index; and group 3 (N = 7) with patients who died during the waiting time. The waiting list death rate was 13.5%/patient-year compared with a post-AVR death rate of 4.9% patient-year (p < 0.05) with a mean post-AVR follow-up of 5.7 years. According to a prognostic index (Cox regression model) at inclusion, group 2 patients had a predicted 7-year post-AVR survival probability of 72%, but only of 61% according to their prognostic index immediately preoperatively; their observed 7-year post-AVR survival was 60%. Logistic regression analysis identified high age, short duration of symptoms, signs of severe hypertrophy and strain in the ECG, female gender, and deranged left ventricular diastolic function (related to severely increased left ventricular muscle mass) as independent predictors of prognostic worsening and death while on the waiting list. The predictive models did not allow sufficiently accurate identification of the patients at risk during the waiting period. The consequences of a surgical waiting period averaging 6 months are serious for AS patients. The death rate is high and a subgroup worsens its prognostic profile with a significantly reduced post-AVR long-term survival as the result.

Modified ultrafiltration in paediatric cardiac surgery.

The effect of modified ultrafiltration (MUF) after cardiopulmonary bypass for paediatric cardiac surgery was evaluated in 138 children with moderate to severe congenital heart disease. The median age was 0.4 years (0 days to 6.5 years), and the weight 5.3 kg (2.2-20 kg). The operation was discontinued in six cases, three because of technical problems and three because of unstable circulation. One-hundred-and-thirty-four patients were ultrafiltrated for a median of 12 min (2-27 min) with an ultrafiltrate of median 44 ml/kg (6-118 ml/kg). Haematocrit was significantly increased from 28% (20-39%) to 36% (26-51%) and systolic arterial pressure from 56 mmHg (30-85 mmHg) to 74.0 mmHg (32-118 mmHg). Furthermore arterial oxygenation was significantly increased from 30.8 kPa (4.8-70.4 kPa) to 34.1 kPa (4.9-80.6 kPa), and arterial carbon dioxide tension from 4.8 kPa (3.1-7.3 kPa) to 5.1 kPa (3.1-7.6 kPa). Heart rate was significantly reduced from 145 beats/min (92-201 beats/min) to 136 beats/min (88-200 beats/min). There were no significant differences in central venous pressure, left atrial pressure and base excess before and after MUF. MUF increases systolic blood pressure, haematocrit, arterial oxygen and carbon dioxide tension coming off bypass in paediatric cardiac surgery and reduces heart rate and postoperative fluid overload.

Impact of size mismatch and left ventricular function on performance of the St. Jude disc valve after aortic valve replacement.

BACKGROUND: The hemodynamic function of the St. Jude valve may change relative to changes in left ventricular function after aortic valve replacement for aortic stenosis. From theoretical reasons one may hypothesize that prosthetic valve hemodynamic function is related to left ventricular failure and mismatch between valve size and patient/ventricular chamber size. METHODS: Forty patients aged 24 to 82 years who survived aortic valve replacement for aortic stenosis with a standard St. Jude disc valve (mean size, 23.5 mm; range, 19 to 29 mm) were followed up prospectively with Doppler echocardiography and radionuclide left ventriculography preoperatively and 9 days, 3 months, and 18 months after the operation with assessment of intravascular hemolysis at 18 months. Follow-up to a maximum of 7.4 years (mean, 6.3 years) was 100% complete. RESULTS: Left ventricular muscle mass index decreased from 198 +/- 62 g.m-2 preoperatively to 153 +/- 53 g.m-2 at 18 months (p < 0.001), paralleled by a significant increase in left ventricular ejection fraction, peak ejection rate, and peak filling rate; only 18% of the patients had normal left ventricular muscle mass index and only 32% normal ventricular function (normal left ventricular ejection fraction, peak ejection rate, peak filling rate, early filling fraction, and late filling fraction during atrial contraction) at 18 months. Prosthetic valve peak Doppler gradient dropped from 20 +/- 6 mm Hg at 9 days to 17 +/- 5 mm Hg at 18 months (p < 0.05). Reduction of left ventricular muscle mass index was unrelated to peak gradient and size of the valve. Peak gradient at 18 months rose with valve orifice diameter of 17 mm or less (by 6 mm Hg), orifice diameter/body surface area of 9 mm.m-2 or less (by 5 mm Hg), left ventricular enddiastolic dimension (by 23 mm Hg per 10 mm increase), and impaired ventricular function (by 3 mm Hg). All but 2 patients (5%) had intravascular hemolysis; none had anemia. Two patients with moderate paravalvular leak had the highest serum lactic dehydrogenase levels; 4 patients with trivial leak had higher serum lactic dehydrogenase levels than those without leak. Serum lactic dehydrogenase levels rose with moderate paravalvular leak, impaired ventricular function, and valve orifice diameter. Six patients with trivial or moderate paravalvular leak had a cumulative 7-year freedom from bleeding and thromboembolism of 44% +/- 22% compared with 87% +/- 5% for those without leak (p < 0.05). CONCLUSIONS: The peak gradient of the St. Jude aortic valve dropped marginally over the first 18 postoperative months in association with incomplete left ventricular hypertrophy regression and marginal improvement of ventricular function. Mismatch between valve size and ventricular cavity size or patient size and impaired function of a dilated ventricle significantly compromised the performance of the St. Jude valve. Probably explained by platelet destruction or activation, paravalvular leak was related to bleeding and thromboembolic complications.

[Total and partial cavo-pulmonary anastomosis for univentricular hearts]. / Total og partiel cava-pulmonal anastomose ved univentrikulaert hjerte.

Between January 1990 and January 1995, 37 children and young adults with univentricular hearts were evaluated for total cavo-pulmonary connection (TCPC) or partial cavo-pulmonary connection (PCPC). Nineteen patients had tricuspid atresia, ten double-inlet left ventricle, five mitral atresia, and three had other complex univentricular lesions. Twenty-eight patients had previously been palliated by a systemic-pulmonary artery shunt or by pulmonary artery banding. All patients underwent physical examination, two-dimensional echo-cardiography, and cardiac catheterization. Suitability for TCPC was decided according to the modified Choussat criteria. Nine patients (24%), were judged unsuitable for any type of cava-pulmonary connection. Seventeen patients aged 5 (2-20) years underwent TCPC, and two patients awaited TCPC at follow-up (October 1995) Nine patients aged 10 (1-40) years had borderline morphology or haemodynamics and therefore underwent PCPC. One of these had, however, to be taken down immediately due to development of superior vena cava syndrome. The postoperative follow-up time was 20 (0.3 5.4) years. The 30-day, 1-, and 5-year survival rates (Kaplan-Meier) were 82%, 76%, and 76% after TCPC and 100%, 100%, and 100% after PCPC. All deaths were due to ventricular failure. At latest follow-up, all hospital survivors were in NYHA class I or II. All PCPC, and 85% of the TCPC patients were in sinus rhythm. All patients had good ventricular function. TCPC and PCPC can be performed in selected patients with univentricular hearts with an acceptable mortality and morbidity and result in significant functional improvement.

Left ventricular systolic and diastolic function in aortic stenosis. Prognostic value after valve replacement and underlying mechanisms.

AIMS: The aims of the study were to examine the prognostic value of pre-operative left ventricular systolic and diastolic function on early, and late mortality after valve replacement for aortic stenosis, and to identify possible underlying mechanisms. METHODS AND RESULTS: Ninety-one prospectively recruited consecutive patients with a mean age of 61 years underwent valve replacement for aortic stenosis with concomitant coronary artery bypass grafting in 32 and a minimum postoperative observation period of 5.4 years. There were six early (< or = 30 days postoperatively) and 19 late deaths, and 18 deaths from specific causes (cardiac and prosthetic valve related). Early mortality occurred exclusively among patients with a combined subnormal left ventricular systolic function (subnormal ejection fraction or peak ejection rate, or supranormal time-to-peak ejection--duration of systole ratio) and a subnormal fast filling fraction. In Cox regression models on crude mortality and specific deaths, a subnormal ejection fraction and a fast filling fraction of < or = 45% were the only independent risk factors. Patients with none of these risk factors had normal sex- and age-specific survival, those with any one factor had an early, and those with both factors a massive early and a late excess mortality, with 5-year crude survival of 92%, 77%, and 50%, respectively (P < 0.0001). Systolic wall stress was without prognostic value. Further analyses indicated that impairment of left ventricular function occurred with increasing muscle mass over two phases: (1) diastolic dysfunction characterized by a pattern of severe relative concentric hypertrophy; (2) the addition of systolic dysfunction characterized by a more dilated, less concentric chamber geometry. Coronary artery disease seemed to provoke the latter development sooner. CONCLUSIONS: Impaired systolic and diastolic left ventricular function, irrespective of afterload, were decisive independent pre-operative risk factors for early as well as late mortality after aortic valve replacement for aortic stenosis. The adverse influence of concentric hypertrophy was the main underlying mechanism. Operative intervention, before impairment of diastolic and systolic function, should be advocated.

Mortality and worsening of prognostic profile during waiting time for valve replacement in aortic stenosis.

In a prospective study 99 consecutive patients with operative indication due to severe aortic stenosis (AS) were put on a surgical waiting list. The waiting-time to aortic valve replacement (AVR) averaged 6.3 months (0.5-19 months). There were 58 men and 41 women with a mean age of 61 years (21-82 years). The patients were divided into three groups: group I (n = 81) with an uneventful stay on the waiting list (including one patient who declined the AVR offer); group II (n = 11) with significant worsening of a prognostic index; and group III (n = 7) with patients who died during the waiting-time. The waiting-list death rate was 13.5 +/- 5.0% patient-year-1 compared with a post-AVR death rate of 4.9 +/- 0.9%. patient-year-1 (p < 0.05) with a mean post-AVR follow-up of 5.7 years. According to their prognostic index at inclusion, group II patients had a predicted (by a Cox model) 7-year post-AVR survival probability of 72%, but only of 61% according to their prognostic index immediately preoperatively; their observed 7-year post-AVR survival was 60%. Logistic regression analysis identified high age, short duration of symptoms, severe hypertrophy and strain in the ECG, female sex, and deranged left-ventricular diastolic function (related to severely increased left-ventricular muscle mass) as independent predictors of death on the waiting-list and prognosis worsening. From a clinical viewpoint, the predictive models did not allow sufficiently accurate identification of the patients at risk during the waiting-time. The consequences of a surgical waiting-time averaging 6 months are serious for AS patients. The death rate is high and a subgroup worsen their prognostic profile, with significantly reduced post-AVR long-term survival as the result.

Pediatric multiplane transesophageal echocardiography in congenital heart disease: new possibilities with a miniaturized probe.

In recent years, transducers for multiplane Doppler echocardiography have demonstrated their superior imaging performance in adult patients. To date, the size of these probes has limited their use in pediatric patients. In this article, we report our initial experience with a recently developed miniaturized transducer with all conventional imaging and Doppler modalities. The study focused primarily on imaging performance by comparing standard biplane images with those obtained in oblique planes. The investigations were carried out intraoperatively or during interventional catheterization in patients with congenital heart disease. We observed no complications in a study population of 15 children (weight range of 5 to 63 kg and an age range of 96 days to 11 years). The probe was easy to handle and provided excellent images. Additional information was obtained in several cases and documentation of clinical findings was easier because an optimal image plane almost always could be displayed. We concluded that pediatric multiplane Doppler echocardiography has considerably improved investigative performance compared with the conventional monoplane or biplane studies normally available for this age group. In neonates, however, investigation with the multiplane technique is limited by the size of the patient.

Two-chain bacteriorhodopsin synthesized by Schizosaccharomyces pombe.

Bacteriorhodopsin (BR), the light-driven proton pump of Halobacterium salinarium purple membrane, was produced in functional form as a two-chain protein by simultaneous expression in the fission yeast Schizosaccharomyces pombe of two separate structural genes, one coding for an aminoterminal BR fragment encompassing the first two transmembrane helices of BR, the other coding for the remainder of the protein. The fragments assemble spontaneously in vivo to yield functional BR which can be purified by immobilized metal ion affinity chromatography.

What force can the myocardium generate on a prosthetic mitral valve ring? An animal experimental study.

Data on the magnitude of forces which can be generated by the myocardium on a prosthetic heart valve ring are not available from the literature. Therefore, we implanted strain gauge mounted 29 mm original specification Edwards-Duromedics mitral valve prostheses in 13 pigs. The valves were implanted in both anatomic and anti-anatomic orientation. In order to estimate the forces on the valve ring, acute in vivo measurements of the dynamic deformation of the valve ring were performed and correlated with the stiffness of the same valves measured in vitro. In the post cardioplegic heart of the anesthetized pigs there was a maximum force developed by the myocardium of 6-8 N on the valve ring with a resulting maximum deformation of 40 microns with valves mounted in the anatomic position. These findings have implications for design of future mechanical mitral valves and for mitral rings used for mitral valvuloplasty. These data can also be used as reference for evaluation of safety limits in existing valves in terms of their physical properties. Based on the direction of the maximum myocardial force acting on the mitral valve ring and the difference in compliance of the valve ring along the pivotal or orthogonal axis, it is indicated from that these acute porcine studies that bileaflet valves in the mitral position are subjected to less deformation when implanted 60 degrees counter-clockwise to the native mitral intercommisural line.