Regression of left ventricular hypertrophy after aortic valve replacement for aortic stenosis with different valve substitutes

OBJECTIVE: Stentless biologic aortic valves are less obstructive than stented biologic or mechanical valves. Their superior hemodynamic performances are expected to reflect in better regression of left ventricular hypertrophy. We compared the regression of left ventricular hypertrophy in 3 groups of patients undergoing aortic valve replacement for severe aortic stenosis. Group I (10 patients) received stentless biologic aortic valves, group II (10 patients) received stented biologic aortic valves, and group III (10 patients) received bileaflet mechanical aortic valves. METHODS: Echocardiographic evaluations were performed before the operation and after 1 year, and the results were compared with those of a control group. Left ventricular diameters and function, left ventricular wall thickness, and left ventricular mass were assessed by echocardiography. RESULTS: Group I patients had a significantly lower maximum and mean transprosthetic gradient than the other valve groups (P = .001). One year after operation there was a significant reduction in left ventricular mass for all patient groups (P < .01), but mass did not reach normal values (P = .05). Although the rate of regression in the interventricular septum and posterior wall thickness differed slightly among groups, their values at follow-up were comparable and still higher than control values (P = .002). The ratio between interventricular septum and posterior wall and the ratio between wall thickness and chamber radius did not change significantly at follow-up. CONCLUSIONS: Because the number of patients was relatively small, we could not use left ventricular mass regression after I year to distinguish among patients undergoing aortic valve replacement for aortic stenosis by means of valve prostheses with different hemodynamic performances.     

Combined warfarin and antiplatelet therapy after St. Jude Medical valve replacement for mitral valve disease

OBJECTIVES: The clinical effect of combined warfarin and antiplatelet therapy on the incidence of stroke and postoperative complications after mitral (plus aortic) valve replacement was studied and compared with that observed with warfarin therapy alone. BACKGROUND: It has been reported that combined warfarin and antiplatelet therapy may be effective but may be associated with an increased hemorrhagic risk. Therefore, definite benefits of the treatment in patients with an implanted prosthetic valve have not been clearly documented. METHODS: Between January 1980 and December 1992, 195 patients with a St. Jude Medical valve at the mitral (plus aortic) position were assigned to receive treatment with either warfarin alone (125 patients) or warfarin plus antiplatelet agents (70 patients), such as dipyridamole (150 or 300 mg daily, 14 patients) or ticlopidine (200 or 400 mg daily, 56 patients). A minimal dose of aspirin (10 to 40 mg) was added (29 patients) if the maximal platelet aggregation rate by collagen was not reduced. The target thrombotest level was 10% to 20%. RESULTS: The two treatment groups were similar with regard to gender and age distribution. The number of patients with atrial fibrillation, left atrial thrombus, history of previous stroke, simultaneous aortic valve operation and previously performed valve procedures were comparable in the two groups. Actuarial survival rate at 10 years was 98.3 +/- 1.7% (mean +/- SD) in the warfarin plus antiplatelet group and 90.3 +/- 3.2% in the warfarin group (p < 0.05 at 1 and 9 to 12 years). The actuarial stroke-free rate at 10 years was 95.3 +/- 3.4% and 84.3 +/- 3.8%, respectively (p < 0.05 by the generalized Wilcoxon test). The actuarial complication-free rate at 10 years was 89.4 +/- 4.3% and 67.9 +/- 4.8%, respectively (p < 0.05 by the generalized Wilcoxon test). No hemorrhagic complications were seen in the warfarin plus antiplatelet group. CONCLUSIONS: The results strongly indicate the effectiveness and safety of combined warfarin plus antiplatelet treatment after St. Jude Medical valve replacement for mitral (plus aortic) valve disease.     

Mitral valve replacement: randomized trial of St. Jude and Medtronic Hall prostheses

BACKGROUND: This study was designed to better define the merits of the bileaflet and tilting-disc valves. METHODS: We prospectively randomized 156 patients (mean age, 59 years) to receive either the St. Jude (n = 80) or the Medtronic Hall (n = 76) mitral valve prosthesis between September 1986 and December 1997. The two groups were not significantly different with respect to preoperative New York Heart Association class, left ventricular ejection fraction, incidence of mitral stenosis or insufficiency, extent of coronary artery disease, completeness of revascularization, or cross-clamp or bypass time. RESULTS: The operative mortality (11.2% versus 13.1%, St. Jude versus Medtronic Hall, respectively) and late mortality (27% versus 22%, St. Jude versus Medtronic Hall, respectively) were not significantly different. Follow-up was complete in all hospital survivors with a mean of 60.7 months (range, 1 to 133 months). The analysis of 10-year actuarial survival and freedom from valve-related events demonstrated no significant differences between the cohorts. Freedom from reoperation was higher in the St. Jude group (p < 0.01). Comparisons of patient functional status and echocardiographic hemodynamic parameters obtained at the time of follow-up demonstrated no significant differences between the two prostheses. CONCLUSIONS: This study suggests that there is no difference between the St. Jude and Medtronic Hall prostheses with respect to late clinical performance or hemodynamic results and therefore does not support the preferential selection of either prosthesis.     

Influence of left ventricular wall thickening on myocardial injury in aortic valve replacement

We retrospectively examined the influence of left ventricular wall thickening on myocardial injury in aortic valve replacement. Thirty-five patients who underwent aortic valve replacement in our hospital between January 1995 and July 1997 were studied. We divided these patients into 3 groups: group N (left ventricular thickness (LVT) < or = 10 mm), group H (10 < LVT < or = 15 mm), and group S (LVT > 15 mm). All patients of group S had aortic stenosis. CK and CK-MB were significantly higher and the cardiac index was significantly lower in group S than in the other groups. Intra-aortic balloon pumping was required for 50% of patients in group S, and a total dose of catecholamine above 10 micrograms/kg/min was also required for 50% of patients in this group. In the other groups, these percentages were significantly lower. Myocardial protection and postoperative care were difficult for patients with severe left ventricular hypertrophy with LVT over 15 mm in this study. Left ventricular wall thickness was a more important factor in determining difficulty with intraoperative myocardial protection than was left ventricular mass.     

Calcified embolus of the left coronary ostia after aortic valve replacement

A patient with a left coronary calcified embolus causing acute myocardial dysfunction immediately after aortic valve replacement is described. Prompt diagnosis by transesophageal echocardiogram was made, which led to removal of the embolus and a subsequent satisfactory course.     

Left ventricular mass regression after implantation of St. Jude Medical cardiac valves in small aortic roots

In this study, we analyzed the extent of regression of left ventricular hypertrophy in patients who received small St. Jude Medical (SJM) aortic valves and compared the results with those of another group receiving larger valves. Eighty-eight patients received either 19 or 21 mm valves (Group 1, 25 patients) or either 23 or 25 mm valves (Group 2, 53 patients). Echocardiographic studies were done before the operation and 5 years postoperatively. At follow-up a significant reduction in the left ventricular mass was found for both patient groups (p < 0.0001). Doppler echocardiography derived pressure gradients for both groups were obtained during the follow-up period. As expected, the patients in Group 1 had higher peak pressure gradients than did those in Group 2. However, there was no significant difference between the 2 groups or any significant correlations between peak pressure gradients and body surface area (BSA). Actuarial survival was 84.7% at 15 years for Group 1 and 85.9% at 17 years for Group 2. Actuarial freedom from valve related events was 91.4% at 15 years for Group 1 and 82.7% at 17 years for Group 2. There was no significant difference in survival or valve related event free curves between the 2 groups. After implantations of SJM valves in small aortic roots, significant left ventricular mass regression was obtained, and the results were comparable to those for valves of other sizes. The long-term performance of aortic valve replacement with small valves was satisfactory as judged by improvement in the functional class of patients and survival statistics, the durability of the prosthesis, and valve related morbidity comparable to that of valves of other sizes.     

Mitral valve replacement with the St. Jude Medical prosthesis: a 15-year follow-up

BACKGROUND: A retrospective study was conducted to analyze the results of St. Jude Medical mitral valve replacement. METHODS: From January 1979 to December 1989, 870 patients (54% women, 46% men; mean age, 55.8 +/- 6.2 years) underwent mitral valve replacement with the St. Jude Medical prosthesis. Of these operations 616 were isolated mitral valve replacements and 254 were double valve replacements. Coronary artery bypass grafting was performed concomitantly in 55 patients (6.3%). RESULTS: Overall, early mortality was 5.05%, with 4.2% for the isolated mitral valve procedure and 7.08% for the double valve replacement. Follow-up at 15 years was complete in 859 patients (98.74%). Mean follow-up time was 93.5 months, for a total of 6,436 years. Actuarial survival at 15 years was 59.5% +/- 5%, 60.5% +/- 6%, and 56.9% +/- 9%, for the entire group, the isolated mitral valve and double valve procedures, respectively. Multivariate analysis identified age, sex, hospital stay, and preoperative mitral regurgitation as independent prognosis factors for overall mortality. Of 606 patients alive at the latest follow-up, the New York Heart Association class improved significantly (from 67% class III/IV before the operation to 88% class I/II after the operation). All patients received warfarin to maintain an international normalized ratio between 3.5 and 4. The linearized rates (% per patient-year) of thrombosis, thromboembolism, and major hemorrhage were, respectively, 0.21, 0.75, and 0.94 for the entire group; 0.18, 0.67, and 0.88 for the isolated mitral valve operation; and 0.15, 0.92, and 1.08 for the double valve replacement. For the entire group the freedom from thrombosis and thromboembolism at 15 years was 98.1% +/- 1% and 88% +/- 4%, respectively. No case of structural dysfunction occurred. The freedom from paravalvular leak and endocarditis at 15 years was 95.3% +/- 2% and 97.3% +/- 2.4%, respectively. The probability of remaining free from reoperation at 15 years was therefore 95.6% +/- 2.5%. CONCLUSIONS: These results confirm that the St. Jude Medical valve is a reliable prosthesis with very low thrombosis and thromboembolism rates, allowing the use of a low dose of anticoagulation with an international normalized ratio of about 3.     

Comparative evaluation of left ventricular performance after mitral valve repair or valve replacement with or without chordal preservation

Germinating barley produces two alpha-amylase isozymes, AMY1 and AMY2, having 80% amino acid (aa) sequence identity and differing with respect to a number of functional properties. Recombinant AMY1 (re-AMY1) and AMY2 (re-AMY2) are produced in yeast, but whereas all re-AMY1 is secreted, re-AMY2 accumulates within the cell and only traces are secreted. Expression of AMY1::AMY2 hybrid cDNAs may provide a means of understanding the difference in secretion efficiency between the two isozymes. Here, the efficient homologous recombination system of the yeast, Saccharomyces cerevisiae, was used to generate hybrids of barley AMY with the N-terminal portion derived from AMY1, including the signal peptide (SP), and the C-terminal portion from AMY2. Hybrid cDNAs were thus generated that encode either the SP alone, or the SP followed by the N-terminal 21, 26, 53, 67 or 90 aa from AMY1 and the complementary C-terminal sequences from AMY2. Larger amounts of re-AMY are secreted by hybrids containing, in addition to the SP, 53 or more aa of AMY1. In contrast, only traces of re-AMY are secreted for hybrids having 26 or fewer aa of AMY1. In this case, re-AMY hybrid accumulates intracellularly. Transformants secreting hybrid enzymes also accumulated some re-AMY within the cell. The AMY1 SP, therefore, does not ensure re-AMY2 secretion and a certain portion of the N-terminal sequence of AMY1 is required for secretion of a re-AMY1::AMY2 hybrid.     

Prediction of indications for valve replacement among asymptomatic or minimally symptomatic patients with chronic aortic regurgitation and normal left ventricular performance

BACKGROUND: Optimal criteria for valve replacement are unclear in asymptomatic/minimally symptomatic patients with aortic regurgitation (AR) and normal left ventricular (LV) performance at rest. Moreover, previous studies have not assessed the prognostic capacity of load-adjusted LV performance ("contractility") variables, which may be fundamentally related to clinical state. Therefore, 18 years ago, we set out to test prospectively the hypothesis that objective noninvasive measures of LV size and performance and, specifically, of load-adjusted variables, assessed at rest and during exercise (ex), could predict the development of currently accepted indications for operation for AR. METHODS AND RESULTS: Clinical variables and measures of LV size, performance, and end-systolic wall stress (ESS) were assessed annually in 104 patients by radionuclide cineangiography at rest and maximal ex and by echocardiography at rest; ESS was derived during ex. During an average 7.3-year follow-up among patients who had not been operated on, 39 of 104 patients either died suddenly (n = 4) or developed operable symptoms only (n = 22) or subnormal LV performance with or without symptoms (n = 13) (progression rate=6.2%/y). By multivariate Cox model analysis, change (delta) in LV ejection fraction (EF) from rest to ex, normalized for deltaESS from rest to ex (deltaLVEF-deltaESS index), was the strongest predictor of progression to any end point or to sudden cardiac death alone. Unadjusted deltaLVEF was almost as efficient. Symptom status modified prediction on the basis of the deltaLVEF-deltaESS index. The population tercile at highest risk by deltaLVEF-deltaESS progressed to end points at a rate of 13.3%/y, and the lowest-risk tercile progressed at 1.8%/y. CONCLUSIONS: Currently accepted symptom and LV performance indications for valve replacement, as well as sudden cardiac death, can be predicted in asymptomatic/minimally symptomatic patients with AR by load-adjusted deltaLVEF-deltaESS index, which includes data obtained during exercise.     

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.     

Relationship between left ventricular morphology and postoperative cardiac function following valve replacement for mitral stenosis

The left ventricular myocardium excised from 14 patients who had mitral stenosis and who underwent mitral valve replacement was examined, and myocardial fibrosis was quantitated in relation to cardiac function. Conventional mitral valve replacement was performed with cold potassium-induced cardioplegia associated with systemic hypothermia (28 degrees C rectal temperature) and topical cooling. All 14 patients had perivascular fibrosis; the amounts ranged from 16% to 54% of the whole tissue excised. The mean left ventricular end-diastolic volume index (LVEDVI) determined by M-mode echocardiography increased significantly (p less than 0.001) from 66.9 +/- 4.6 ml/m2 preoperatively to 79.0 +/- 2.9 ml/m2 postoperatively. The difference between preoperative and postoperative LVEDVIs was significantly correlated (p less than 0.01) to the percentage of myocardial fibrosis (r = 0.72), in that the index increased postoperatively when myocardial fibrosis was more than 35% and decreased when fibrosis was less than 35%. After mitral valve replacement, the mean ejection fraction increased when fibrosis was less than 35% of whole tissue (+0.12 +/- 0.04) and decreased when fibrosis was greater than 35% (-0.02 +/- 0.02, p less than 0.01). No measured preoperative hemodynamic parameters were predictive of prognosis. These data suggest that the degree of myocardial fibrosis is related to left ventricular performance after mitral valve replacement.     

Effects of valve replacement on ventricular mechanics in mitral regurgitation and aortic stenosis

BACKGROUND: This study in humans assessed changes in left ventricular function early and late after correction of mitral regurgitation (MR) (n = 9) or aortic stenosis (AS) (n = 10). METHODS: Ventricular function was measured with radionuclide and micromanometer-derived pressure-volume loops during preload manipulation, thermodilution cardiac outputs, and echocardiograms. Late radionuclide and echocardiographic data were acquired at 24 hours and 20 months. RESULTS: Perioperative left ventricular performance (stroke work-end-diastolic volume relationship) did not change for patients with MR or AS. Significant changes in afterload occurred: ejection fraction (MR, 0.49 to 0.37; AS, 0.54 to 0.60; both, p = 0.013), mean left ventricular ejection pressure (MR, 73 to 91 mm Hg; AS, 138 to 93 mm Hg; both, p < 0.01), and end-systolic wall stress (MR, 26 to 42 x 10(3) dynes/cm2; AS, 37 to 22 x 10(3) dynes/cm2; both, p < 0.01). Ejection efficiency improved for MR patients (0.69 +/- 0.26 to 1.0 +/- 0.15; p < 0.05). The 20-month data showed improved New York Heart Association functional class, normal resting ejection fraction, and normal exercise response for both groups. CONCLUSIONS: Early after operation, a significant change in left ventricular load was seen with correction of MR and AS. Data obtained late after operation showed improvement consistent with ventricular remodeling.     

Myxoma of the left atrial appendage mimicking thrombus during aortic valve replacement

A previously well, 48-year-old female presented with a short history of respiratory distress and fever for which no cause could be found. Open lung biopsy was not contributory. She died within nine days of presentation of hypoxia and multi-organ failure. Post mortem examination revealed the pattern of desquamative interstitial pneumonitis.     

Hemodynamic evaluation of the Carbomedics R, St Jude Medical HP and Sorin-Bicarbon valve in patients with small aortic annulus

A Doppler echocardiographic study was performed to evaluate the hemodynamic performance of three 19 mm size currently used bileaflet valve prosthesis (St Jude Medical Hydrodinamic Plus, Sorin-Bicarbon and Carbomedic Reduced) implanted in aortic position. METHODS: Patients, 30, with the same profile receiving 19 mm size valve (ten for each valve type) were selected when body surface area (BSA) was > 1.7 m2. Doppler echocardiography was carried out at rest and after exercise, 60 days after surgery. Peak (Pg) and mean (Mg) gradients across the valve were recorded: the effective orifice area (EOA), and performance index (PI) were calculated. RESULTS: No significant differences were observed between St Jude Medical and Sorin Bicarbon as far as peak and mean gradient, effective orifice area and performance index at rest and after exercise. A significant difference (P < 0.05) was demonstrated in the above mentioned parameters when Carbomedics-R valve were tested. This type of valve showed a lower EOA and PI with higher Pg and Mg gradient both at rest and after exercise. CONCLUSION: The St Jude Hydrodymanic plus (Hp) and Sorin Bicarbon valves had similar performance and a better hemodynamic trend when compared to the Carbomedics-R valve in patients with large body surface areas. The Carbomedics-R valve shows a ineffective use of the total area of the prosthesis both at rest and after exercise.     

The effect of prosthesis-patient mismatch on aortic bioprosthetic valve hemodynamic performance and patient clinical status

BACKGROUND: High pressure gradients occurring through normally functioning prosthetic valves appear to be related to a mismatch between the effective orifice area of the prosthesis and the patient's body surface area. OBJECTIVE: To determine whether prosthesis-patient mismatch affects clinical and hemodynamic status, a group of patients with a bioprosthetic heart valve in the aortic position was prospectively evaluated at 6.2+/-4.4 years after implantation by transthoracic Doppler echocardiography. METHODS: Manufacturer-derived in vitro valve areas were available in 61 patients allowing classification into two subgroups, with or without mismatch, based on a valve area at implantation indexed for body surface area 0.85 cm2/m2 or less, or greater than 0.85 cm2/m2. Clinical and hemodynamic parameters evaluated at follow-up included New York Heart Association (NYHA) class distribution, mean transprosthetic gradient, prosthetic valve area and cardiac index. RESULTS: Prosthesis-patient mismatch was present in 32 of 61 patients (52%). Although NYHA class of the patients was similar in both groups, hemo-dynamic performance of the aortic bioprostheses was worse in patients with mismatch than in patients with no mismatch, as indicated by a higher mean gradient (22+/-9 versus 15+/-8 mm Hg, P=0.002) and a lower cardiac index (3.0+/-0.7 versus 3.4+/-0.7 L/min/m2, P=0.04). The prevalence and severity of intrinsic prosthetic dysfunction were similar in both groups. Despite similar NYHA functional class distribution in both groups, the occurrence of syncope, acute pulmonary edema and angina pectoris was significantly higher in patients with mismatch (50% versus 21%, P=0.017). CONCLUSIONS: Prosthesis-patient mismatch is associated with worse hemodynamic performance and higher prevalence of adverse clinical events. However, mismatch did not promote accelerated hemodynamic or structural deterioration of the bioprosthesis.     

Haemolysis after mitral valve replacement with the Bj?rk-Shiley and the Lillehei-Kaster disc valve prosthesis

The present study reports on the incidence and degree of intravascular haemolysis in 33 patients with Bj?rk-Shiley tilting disc prosthesis and in 34 patients with Lillehei-Kaster pivoting disc valve prosthesis in the mitral position examined 12 to 24 months after the operation. Serum haptoglobin, serum lactate dehydrogenase, serum bilirubin, and haemoglobin estimations were performed. Significant haemolysis was detected in 85 per cent of the patients. Haptoglobin was absent or reduced in 72 per cent, while raised values for serum lactate dehydrogenase were found in 43 per cent. The increase in lactate dehydrogenase was moderate and showed no correlation with blood flow through the prosthesis or with the gradient across the prosthesis. Most patients had normal haemoglobin and normal serum bilirubin values. Although intravascular haemolysis was of little clinical significance, the increase in lactate dehyrdrogenase was significantly higher in patients with the Lillehei-Kaster prosthesis than in patients with the Bj?rk Shiley prosthesis, indicating a slightly shorter red cell lifespan in the former group. The possible reasons for the difference between the two groups are discussed.     

St. Jude Medical valve prosthesis: an analysis of long-term outcome and prognostic factors

Between 1979 and 1984, 321 patients received 354 St. Jude Medical prostheses (194 aortic, 94 mitral, 1 tricuspid, and 32 multiple valve replacements). Follow-up was 96% complete (2967 patient-years; mean 9.5 years per patient). Actuarial event-free rates at 10 years and linearized rates (in parentheses) of late complications were as follows: embolism, 85.0% +/- 2.3% (2.3% per patient-year); anticoagulant-related hemorrhage, 74.8% +/- 2.7% (3.3% per patient-year); cerebrovascular accident, 81.8% +/- 2.5% (2.6% per patient-year); prosthesis thrombosis, 98.5% +/- 0.7% (0.1% per patient-year); endocarditis, 97.2% +/- 1.1% (0.4% per patient-year); prosthesis dysfunction, 97.1% +/- 1.0% (0.4% per patient-year); hemolytic anemia, 98.5% +/- 0.7% (0.1% per patient-year); reoperation, 97.4% +/- 1.0% (0.4% per patient-year); overall mortality, 63.3% +/- 2.7% (4.2% per patient-year); and valve-related death (including sudden death), 84.7% +/- 2.2% (1.4% per patient-year). Independent preoperative risk factors were as follows: (1) for embolism, cardiac failure as indication for operation and history of prior systemic embolism; (2) for cerebrovascular accidents, the same two factors and age; (3) for endocarditis, diabetes, chronic alcoholism, and aortic valve replacement; (4) for overall mortality, age, ejection fraction (or cardiac index or cardiothoracic index), chronic alcoholism, and history of systemic embolism; and (5) for valve-related death, chronic alcoholism, degenerative cause of valve disease, and prosthetic diameter 23 mm or smaller. Ninety percent of survivors were in New York Heart Association functional class I or II at the end of follow-up. In conclusion, this study confirms the excellent durability of the St. Jude Medical valve and the remarkable functional benefit for the majority of the patients. However, prosthesis-related complications are still common, particularly for small-diameter prostheses. Outcome is strongly related to the patient's preoperative cardiac condition and to the adequacy of anticoagulation control.     

Effect of short-term hormone replacement therapy on left ventricular mass and contractile function

This study examined the effects of neonatal cocaine exposure on the rewarding properties of play in a modified T-maze. Animals were artificially reared from postnatal day (PND) 4-9 with drug concentrated in four daily feeds. There were four treatment groups, 40 mg/kg/day cocaine, 20 mg/kg/day cocaine, an artificially reared control and a surgery control. From PND 38-42, subjects were tested with a food reward (EXP 1) or a play reward (EXP 2). No deficits in learning were seen when the reward was food. The 20 mg/kg/day cocaine group, however, showed impaired learning and altered play behavior when the reward was access to a play partner. Neonatal cocaine exposure thus appears to differentially affect learning based on the type of reward presented.     

Successful aorto-circumflex coronary bypass grafting through left thoracotomy following aortic and mitral valve replacement

We report successful descending thoracic aorto-circumflex coronary artery bypass grafting using a saphenous vein graft through left thoracotomy in a 44-year-old female. The patient developed severe angina attack after aortic and mitral valve replacement. Coronary angiography showed 99% stenosis of the circumflex coronary artery. Under general anesthesia, left femoral vein to arterial partial cardiopulmonary bypass was performed via left 4 th intercostal space. Body temperature was lowered to 22 degrees centigrade, and spontaneous cardiac fibrillation occurred. After minimal exposure by pericardial dissection of the circumflex coronary artery, distal anastomosis and then proximal anastomosis at the descending thoracic aorta was carried out under cardiac fibrillation. This surgery was done with minimal intra-and postoperative bleeding. Postoperative course was very smooth, and the patient was discharged and leading a normal life for 6 months after surgery.