Behavior of Mustela putorius furo (the domestic ferret).

Behavior patterns exhibited by the domestic ferret, although similar to its wild cousins, are distinctly domestic in nature. Domestic ferrets use many different types of behaviors, including body posturing, animations, vocalizations, and scent markings. These behaviors may differ somewhat from ferret to ferret. The domestic ferret is best understood by observation and recognition of its behavior patterns and interactions as it plays and communicates with both humans and animals within its home environment. As with all other species of animals kept as pets, the clinician will be greatly benefited by urging the pet owner to regularly note typical behavior patterns for their individual pet. Following is a brief summary of behavioral changes noted in domestic ferrets that may aid the owner or keeper in the detection of potential illness or injury: A normally active ferret suddenly becoming quiet or vice-versa Any sudden increase or decrease in daily food and water intake Routine behaviors performed out of context or order, especially in older animals Any sudden increase or decrease in the speed at which routine behaviors are performed (such as urination, defecation, grooming, food, or water intake) Any sudden increase in the effort required to perform normal or routine behaviors Any sudden changes in personality or attitude toward other ferrets or toward other animals or people. The previous information was gathered over the last 15 years from personal observations, experiences, and studies of ferrets in the shelter, home, and animal hospital environments. This information regarding ferret behavior can assist the veterinarian in differentiating between normal and abnormal behaviors in domestic ferrets. This increased understanding of ferret behavior can aid in the diagnosis of injury and disease and assist the veterinarian in educating clients regarding ferret behavior, care, and recognition of potential disease.

Sustained angina relief 5 years after transmyocardial laser revascularization with a CO(2) laser.

BACKGROUND: Although transmyocardial laser revascularization (TMR) has provided symptomatic relief of angina over the short term, the long-term efficacy of the procedure is unknown. Angina symptoms as assessed independently by angina class and the Seattle Angina Questionnaire (SAQ) were prospectively collected up to 7 years after TMR. METHODS: Seventy-eight patients with severe angina not amenable to conventional revascularization were treated with a CO(2) laser. Their mean age was 61+/-10 years at the time of treatment. Preoperatively, 66% had unstable angina, 73% had had >/=1 myocardial infarction, 93% had undergone >/=1 CABG, 42% had >/=1 PTCA, 76% were in angina class IV, and 24% were in angina class III. Their average pre-TMR angina class was 3.7+/-0.4. RESULTS: After an average of 5 years (and up to 7 years) of follow-up, the average angina class was significantly improved to 1.6+/-1 (P=0.0001). This was unchanged from the 1.5+/-1 average angina class at 1 year postoperatively (P=NS). There was a marked redistribution according to angina class, with 81% of the patients in class II or better, and 17% of the patients had no angina 5 years after TMR. A decrease of >/=2 angina classes was considered significant, and by this criterion, 68% of the patients had successful long-term angina relief. The angina class results were further confirmed with the SAQ; 5-year SAQ scores revealed an average improvement of 170% over the baseline results. CONCLUSIONS: The long-term efficacy of TMR persists for >/=5 years. TMR with CO(2) laser as sole therapy for severe disabling angina provides significant long-term angina relief.

Late outcome of reoperative coronary revascularization on the beating heart.

BACKGROUND: Reoperative (redo) coronary artery bypass grafting (CABG) is associated with a higher morbidity and mortality than first-time CABG. An off-cardiopulmonary bypass (off-pump) approach to redo CABG, however, may potentially benefit redo patients. The aim of the present report is to describe the early and long-term clinical outcome of patients who underwent off-pump redo CABG between July 1985 and January 1999 in our institution. METHODS: Redo patients (n = 138) represented 13% of patients who had off-pump CABG during the period of study (n = 1072). Mean patient age was 63 +/- 12 years, and 67% were men. Surgical approaches included median sternotomy (n = 93, 67%), anterior (n = 20, 15%) and lateral (n = 25, 18%) minimally invasive direct coronary artery bypass (MIDCAB). RESULTS: Operative mortality was 2% (n = 3). Target lesion re-intervention was 6% (n = 9) Actuarial survival at a mean period of follow-up of 2.5 +/- 1 year (range: 1 month to 11 years) was 83%. Event-free survival (freedom from death, myocardial infarction, and repeat intervention) was 67%. Overall cardiac-related mortality was 10% (n = 14). CONCLUSION: Off-pump redo CABG can be safely performed with a relatively low mortality rate and a low rate of target lesion revascularization.

Stroke after coronary artery bypass: incidence, predictors, and clinical outcome.

BACKGROUND AND PURPOSE: Early postoperative stroke is a serious adverse event after coronary artery bypass grafting (CABG). This study sought to investigate risk factors, prevalence, and prognostic implications of postoperative stroke in patients undergoing CABG. METHODS: We investigated the predictors of postoperative stroke (n=333, 2%) in 16 528 consecutive patients who underwent CABG between September 1989 and June 1999 in our institution. Predictors of postoperative stroke were identified by logistic regression analysis. RESULTS: Among the preoperative and postoperative factors, significant correlates of stroke included (1) chronic renal insufficiency (P<0.001), (2) recent myocardial infarction (P=0.01), (3) previous cerebrovascular accident (P<0.001), (4) carotid artery disease (P<0.001), (5) hypertension (P<0.001), (6) diabetes (P=0.001), (7) age >75 years (P=0.008), (8) moderate/severe left ventricular dysfunction (P=0.01), (9) low cardiac output syndrome (P<0.001), and (10) atrial fibrillation (P<0.001). Postoperative stroke was associated with longer postoperative stay (11+/-4 versus 7+/-3 days for patients without stroke, P<0.001) and with higher in-hospital mortality (14% versus 2.7% for patients without stroke; P<0.001). CONCLUSIONS: Stroke after CABG is associated with high short-term morbidity and mortality. Increased stroke risk can be predicted by preoperative and postoperative clinical factors.

Minimally invasive coronary revascularization in women: A safe approach for a high-risk group.

PURPOSE: Female gender has been shown to be an independent risk factor for mortality in coronary artery bypass graft (CABG) surgery. This report analyzes our early outcomes in 304 women who underwent off-pump coronary artery bypass (OPCAB) surgery at the Washington Hospital Center (Washington, DC) over the last 3 years to determine whether this is a safe approach for coronary bypass in women. METHODS: A retrospective review of 5528 cases of CABG bypass (on-pump) and 840 cases of OPCAB surgery, from June 1996 to July 1999, was performed. Women accounted for 1527 (27.6%) of the on-pump bypass cases and 304 (36.2%) of the OPCABs. All cases without cardiopulmonary bypass were included, with the majority of the most recent cases being multivessel revascularization. The data for analysis were obtained from our cardiac surgery database and included cases from all surgeons operating at the Washington Hospital Center, although the majority of off-pump cases were performed by only a few of these surgeons. RESULTS: The two groups were similar with respect to urgent cases, redos, and other comorbities including preoperative congestive heart failure, peripheral vascular disease, transient ischemic attack (TIA), cerebral vascular accident, and previous myocardial infarction. The mean age for the two groups was similar, 67 years for the off-pump group and 66 years for the on-pump group. The absolute number of all off-pump cases increased each year (from 175 to a total of 373), representing a corresponding increase in percentage of all coronary artery bypass procedures (from 9% to 16%). Of the total number of patients undergoing CABG, the percentage of women who underwent OPCAB doubled from 3% to 6% over the time period analyzed. The percentage of single-vessel cases in the off-pump group fell from 88% to 41% as multivessel bypasses became more routine However, the percentage of patients aged > 75 years was greater for the off-pump group (30%) than for the on-pump group (24%). Otherwise, the two groups differed only in diabetic disease (36% off-pump compared with 46% on-pump; p = 0.001) and previous transcatheter therapy (38% off-pump compared with 29% on-pump; p = 0.003). Patients who had OPCABs received fewer postoperative transfusions (40%) than the on-pump group (59%; p < 0.001). The off-pump group also had fewer neurological complications in the form of TIAs or strokes (0.3%) compared with the on-pump group (3.5%; p = 0.001). The mortality rate was 2.3% off -pump versus 4.1% on pump but did not reach statistical significance in this study (p =.12). CONCLUSION: Myocardial revascularization in women can be performed safely without cardiopulmonary bypass. In our series, the mortality for women receiving off-pump revascularization was lower than the on-pump cohorts despite an older age and higher incidence of diabetes. Although the absolute mortality rates did not reach statistical significance, we were encouraged that the mortality rate for women operated on without CPB dropped to the mortality rate typically seen in men. We also observed a favorable tendency in the off-pump group for a shorter length of stay and a lower incidences of transient ischemic attacks, strokes, post-op bleeding, and blood transfusions. A larger series of patients with multivariate analysis and/or a prospective trial will need to be analyzed in order to confirm our findings.

Coronary revascularization of the circumflex system: different approaches and long-term outcome.

BACKGROUND: Minimally invasive direct coronary artery bypass, without cardiopulmonary bypass, through a left lateral thoracotomy approach (lateral MIDCAB), is a safe alternative to coronary artery bypass surgery using cardiopulmonary bypass (on-pump CABG) of the circumflex system via median sternotomy. However, it is unknown whether lateral MIDCAB may yield an improved long-term outcome over the conventional on-pump median sternotomy approach. METHODS: We compared the perioperative outcomes of patients undergoing lateral MIDCAB (n = 34) versus conventional on-pump CABG of the circumflex system (n = 16) from June 1996 to July 1999. The two groups were similar with respect to baseline characteristics and risk stratification. Patients who required only one or two grafts for complete revascularization were included. RESULTS: Lateral MIDCAB patients had a lower need than on-pump CABG patients for intraoperative (12% MIDCAB vs 43% on-pump CABG, p = 0.03) and postoperative transfusions (29% vs 69%, p = 0.01), had fewer neuropsychologic changes (0% vs 19%, p = 0.03), and had a lower rate of postoperative atrial fibrillation (12% vs 44%, p = 0.02). Lateral MIDCAB was also associated with a significantly lower postoperative length of stay (5 +/- 2 vs 7 +/- 3 days, p = 0.02). Actuarial survival at a mean period of follow-up of 19 +/- 11 months was 97% for the lateral MIDCAB versus 88% for the on-pump CABG group (p = 0.6). Event-free survival was 88% for lateral MIDCAB versus 81% for on-pump CABG (p = 0.1). CONCLUSIONS: Lateral MIDCAB may safely be performed in patients with isolated coronary artery disease of the circumflex system with improved early morbidity and an abbreviated hospital stay compared with conventional median sternotomy on-pump CABG.

Beating heart versus conventional single-vessel reoperative coronary artery bypass.

BACKGROUND: Reoperative (redo) coronary artery bypass grafting (CABG) with cardiopulmonary bypass (on-pump) is associated with a higher morbidity and mortality than first-time CABG. It is unknown, however, whether CABG without cardiopulmonary bypass (off-pump) may yield an improved clinical outcome over conventional on-pump redo CABG. METHODS: We compared the perioperative outcomes of patients with single-vessel disease who underwent on-pump (n = 41) versus off-pump (n = 91) redo CABG between April 1992 and July 1999. The two groups were similar with respect to baseline characteristics and risk stratification: mean Parsonnet scores were 26 +/- 9 for on-pump versus 24 +/- 8 for off-pump patients (p = nonsignificant). RESULTS: On-pump redo patients had a higher rate of postoperative transfusions (58% on-pump versus 27% off-pump, p = 0.001), prolonged ventilatory support (17% on-pump versus 4% off-pump, p = 0.03), and a higher rate of postoperative atrial fibrillation (29% on-pump versus 14% off-pump, p = 0.04). On-pump redo CABG was also associated with prolonged postoperative length of stay (8 +/- 4 days on-pump versus 5 +/- 2 days off-pump, p < 0.001). In-hospital mortality was significantly higher in on-pump than in off-pump patients (10% versus 1%, p = 0.03). CONCLUSIONS: Single-vessel off-pump redo CABG can be performed safely with a lower operative morbidity and mortality than on-pump CABG and an abbreviated hospital stay compared with conventional on-pump redo CABG.

Atrial fibrillation after beating heart surgery.

Postoperative atrial fibrillation (AF) is a frequent adverse event after coronary artery bypass grafting (CABG) and may negatively affect the early clinical outcome. We sought to investigate the risk factors, prevalence, and prognostic implications of postoperative AF in patients submitted to CABG without cardiopulmonary bypass (off-pump). The study population comprised 969 patients, 645 men (67%) and 324 women (33%) who had off-pump CABG at the Washington Hospital Center from January 1987 to May 1999. Preoperative AF patients were excluded (n = 15). Two hundred six patients (age 69 +/- 10 years, 137 men [66%]) developed AF, whereas 763 patients (age 61 +/- 12 years, 508 men [67%]) did not. Predictors of AF included age >75 years (odds ratio [OR] 3.0, 95% confidence interval [CI] 1.9 to 4.5; p <0.001), history of stroke (OR 2.1, CI 1.2 to 3.7; p = 0. 007), postoperative pleural effusion requiring thoracentesis (OR 3.2, CI 1.0 to 9.4; p = 0.03), and postoperative pulmonary edema (OR 5.1, CI 1.2 to 21; p = 0.02). Minimally invasive direct CABG was associated with a lower incidence of AF (OR 0.4, CI 0.3 to 0.7; p <0. 001). AF was associated with a prolonged postoperative hospital stay (9 +/- 6 days AF vs 6 +/- 5 days no AF, p <0.001). In-hospital mortality was significantly higher in AF patients (3% AF vs 1% no AF, p = 0.009). Patients with persistent AF had a higher postoperative in-hospital stroke rate than patients without persistent AF (9% vs 0. 6%, p <0.001). AF after beating heart surgery is associated with a higher in-hospital morbidity, mortality, and prolonged hospital stay. A minimally invasive surgical approach (minimally invasive direct CABG) is associated with a lower risk of AF.

Beating heart surgery in octogenarians: perioperative outcome and comparison with younger age groups.

BACKGROUND: Octogenarians have higher morbidity and mortality rates (9% to 16%) after coronary artery bypass grafting with cardiopulmonary bypass, compared with younger patients. METHODS: We compared the perioperative outcome and hospital stay after coronary artery bypass grafting without cardiopulmonary bypass (off-pump) from January 1987 to May 1999, among patients older than 80 years (n = 71), patients between 70 and 79 years (n = 228), and patients whose age ranged from 60 to 69 years (n = 296). In comparison with younger patients, more octogenarians were female (51% versus 39% in patients aged 70 to 79 years and 35% in those aged 60 to 69 years, p = 0.04), they had previous myocardial infarction more frequently (48% versus 47% versus 34%, respectively, p = 0.008), and were operated on urgently (69% versus 56% versus 52%, respectively, p = 0.04). RESULTS: Postoperative complications that were significantly higher in octogenarians compared with younger groups included pneumonia (6% in octogenarians versus 2% in patients aged 70 to 79 years and 0% in patients aged 60 to 69 years, p = 0.001) and atrial fibrillation (47% versus 32% versus 21%, respectively, p<0.001). By multivariate logistic regression analysis, age over 80 years was an independent predictor of prolonged hospital stay (odds ratio = 2.7, 95% confidence interval, 1.4 to 5, p<0.001). The in-hospital mortality rate was higher in octogenarians (6% versus 3% for 70 to 79 year-olds and 0.3% for 60 to 69 year-olds, p = 0.006). CONCLUSIONS: When appropriately applied in patients older than 80 years, off-pump coronary artery bypass grafting can be done with acceptable postoperative morbidity, mortality, and hospital stay.

Transmyocardial laser revascularization in the patient with unmanageable unstable angina.

BACKGROUND: Transmyocardial laser revascularization (TMR) provides relief for patients with chronic angina, nonamenable to direct coronary revascularization. Unmanageable, unstable angina (UUA) defines a subset of patients with refractory angina who are at high risk for myocardial infarction and death. Patients were classified in the UUA group when they had been admitted to the critical care unit with unstable angina for 7 days with three failed attempts at weaning them off intravenous antianginal medications. METHODS: Seventy-six treated patients were analyzed to determine if TMR is a viable option for patients with unmanageable unstable angina. These patients were compared with 91 routine protocol patients (protocol group [PG]) undergoing TMR for chronic angina not amenable to standard revascularization. The procedure was performed through a left thoracotomy without cardiopulmonary bypass. These patients were followed for 12 months after the TMR procedure. Both unmanageable and chronic angina patients had a high incidence of at least one prior surgical revascularization (87% and 91%, respectively). RESULTS: Perioperative mortality (< or = 30 days post-TMR) was higher in the UUAG versus PG (16% vs 3%, p = 0.005). Late mortality, up to 1 year of follow-up, was similar (13% vs 11%, UUAG vs PG; p = 0.83). A majority of the adverse events in the UUAG occurred within the first 3 months post-TMR, and patients surviving this interval did well, with reduced angina of at least two classes occurring in 69%, 82%, and 82% of patients at 3, 6, and 12 months, respectively. The percent improvement in angina class from baseline was statistically significant at 3, 6, and 12 months. A comparable improvement in angina was found in the protocol group of patients. CONCLUSIONS: TMR carried a significantly higher risk in unmanageable, unstable angina than in patients with chronic angina. In the later follow-up intervals, however, both groups demonstrated similar and persistent improvement in their angina up to 12 months after the procedure. TMR may be considered in the therapy of patients with unmanageable, unstable angina who otherwise have no recourse to effective therapy in the control of their disabling angina.

North American experience with the Perma-Flow prosthetic coronary graft.

BACKGROUND: The Perma-Flow prosthetic coronary graft is a 5-mm polytetrafluoroethylene tube into which is incorporated a Venturi flow restrictor. An aorto-superior vena caval fistula is created and coronary anastomoses are constructed proximal to the resistor in side-to-side fashion, where arterial pressure is maintained. From November 1992 through December 1995, eight investigational centers in North America have implanted this graft in 40 patients with inadequate autologous alternatives. METHODS: Patients were selected for inclusion in this study if coronary artery bypass grafting was required and adequate autologous conduit to complete revascularization was not available. Operative data were completed by the implantating surgeon and referred to a central center, the Minneapolis Heart Institute, for correlation. Follow-up was conducted by data coordinators at each institution, and follow-up data were obtained directly from these coordinators for inclusion in the study. RESULTS: Patient age ranged from 53 to 82 years, and 15 patients were undergoing reoperations (38%). On each Perma-Flow graft one to four coronary side-to-side anastomoses were constructed. In addition, left internal mammary artery (n = 26), greater saphenous vein (8), right internal mammary artery (4), and gastroepiploic artery (4) were used to complete revascularization. Aortic (2) or mitral valve replacement (1) was also carried out. There were seven operative deaths (18%) and two late deaths (4 and 6 months). After 1 to 37 months (mean, 13 +/- 9 months) of follow-up, 29 of 31 surviving patients are asymptomatic. Echocardiographic heart size has not increased from the postoperative value, indicating limited volume load has not affected heart size. Protocol catheterization (n = 32) in 28 patients 1 week to 1 year postoperatively revealed 7 of 73 studied coronary anastomoses (9.5%) and two distal extensions and resistors were occluded (7%). In 1 patient during sternal debridement at 1 year, no flow was found in the graft. CONCLUSIONS: The Perma-Flow graft is a useful adjunct to complete revascularization in patients with deficient autologous conduit.

Thromboembolic complications in a peripartum cardiomyopathy patient supported with the Abiomed BVS-5000 ventricular assist device.

A case of systemic embolization arising from an akinetic left ventricle in a peripartum cardiomyopathy patient supported with the Abiomed BVS-5000 ventricular assist device is reported. In an akinetic ventricle, prevention of blood stasis by positioning the atrial cannula tip across the mitral valve to decompress the ventricle may prevent this complication.

Coronary artery bypass without cardiopulmonary bypass.

The purpose of this article is twofold: to describe our technique for performing coronary artery bypass grafting without cardiopulmonary bypass (off pump) and to demonstrate that this operation is safe, in terms of mortality and certain indices of morbidity. Very little has been published in regard to off-bypass operations. From 1985 through 1990, 220 patients underwent operation off bypass; 220 on-pump controls were retrospectively matched for number of grafts, left ventricular function, and date of operation. Groups were compared in terms of mortality and ten indicators of morbidity. The same analysis was performed for ten subgroups. We found no statistically significant difference between groups in mortality (off pump, 1.4% [3/220]; on pump, 2.4% [5/220]), which held across all subgroups. Patients undergoing operation off pump required blood far less often (not transfused: off pump, 72.7% [160/220]; on pump, 54.6% [116/220]; p = 0.005 by Fisher's exact test), and the low output state occurred statistically less frequently off pump (off pump, 5.5% [12/220]; on-pump, 12.7% [28/220]; p = 0.01 by Fisher's exact test). Further research should be directed to which subgroups can be operated on to advantage off pump and which, if any, groups of patients should be confined to on-bypass operations.

Definitive repair in patients with pulmonary atresia and intact ventricular septum.

Between 1977 and 1988, 22 patients underwent definitive repair for pulmonary atresia with intact ventricular septum. Fifteen underwent biventricular repair (mean age 24 months). All had mild to moderate right ventricular hypoplasia at the time of definitive repair. Repair consisted of closure of the atrial septal defect with enlargement of the right ventricular cavity and outflow tract with a patch in eight, insertion of a valved homograft in three, and superior vena cava-pulmonary artery connection in four. There was one operative death (7%). Seven patients had severe right ventricular hypoplasia at the time of definitive repair and underwent a Fontan procedure (mean age 46 months). In two a valved connection was made to the right ventricle and in five a right atrial-pulmonary artery nonvalved connection. There were two operative deaths (29%). Three patients had right ventricular-coronary sinusoids: Two of them underwent a Fontan procedure and one a biventricular repair. We conclude that with adequate early palliation a biventricular repair may be successfully performed for patients with mild or moderate right ventricular hypoplasia, and the Fontan procedure may be used for those with severe right ventricular hypoplasia.

The fate of the 12 mm porcine valved conduit from the right ventricle to the pulmonary artery. A ten-year experience.

The 12 mm Dacron conduit containing a porcine valve is the smallest valved conduit manufactured and is used in the youngest infants with the most diminutive pulmonary arterial system. The outcome of patients with such a conduit is unknown. Between 1975 and 1985 there were 49 hospital survivors after placement of a 12 mm extracardiac valved conduit from the right ventricle to the pulmonary artery. Follow-up is available in 42 patients, aged 1 to 16 months (mean 3.5) and weighing 2.5 to 8.7 kg (mean 3.8). Twenty-eight patients (67%) have undergone subsequent conduit replacement, and 11 (26%) are alive and asymptomatic with a mean follow-up of 56 months. There were three late deaths. The interval between implantation and conduit change was 4.5 to 101 months (mean 44), allowing a weight gain of 2.7 to 23 kg (mean 10.4) before reoperation at age 12 to 117 months (mean 49). Despite elevated right ventricular pressures equaling systemic values, 37% of these patients were clinically asymptomatic. The gradient across the 12 mm valved conduit before explantation ranged from 30 to 173 torr (mean 83) with an almost equal predilection for stenosis at the proximal anastomosis, valve, conduit, distal anastomosis, and main pulmonary artery. The intervening pulmonary artery growth determined the size of the replacement conduit, 14 to 25 mm (mean 16), and was the main factor influencing the results of reoperation. This study demonstrates that the 12 mm porcine valve-containing conduit affords palliation in this difficult subset of patients with the smallest pulmonary arterial tree.

Recurrent macromastia after subcutaneous mastectomy.

Management of sudden unrelenting breast growth in a young woman included use of antiestrogen hormone therapy and subcutaneous mastectomy. Later, massive breast growth again occurred during pregnancy, requiring a repeat postpartum subcutaneous mastectomy. The dramatic response to a specific antiestrogen agent and the subsequent massive regrowth of breast tissue after subcutaneous mastectomy suggests that breast tissue is extremely sensitive to circulating hormones in certain patients with macromastia. The unusual nature of this patient's recurrent macromastia warrants this review of reports of similarly affected patients and discussion of general concepts in the medical and surgical management of the disorder.

Structure and classification of cuspal tears and perforations in porcine bioprosthetic cardiac valves implanted in patients.

Morphologic studies were made of cuspal tears and perforations in 16 porcine valve bioprostheses that had been implanted in 14 patients (9 male and 5 female) ranging in age from 2 to 65 years. Eleven bioprostheses had been in the mitral position for 30 to 123 months, four in the aortic position for 15 to 40 months and one in a varied pulmonary conduit for 96 months. The cuspal lesions were classified into four types. Type I lesions, which involved the free edges of the cusps, were the most common of all lesions and occurred with equal frequency in mitral and aortic bioprostheses. Regardless of position of implantation, type I lesions were more frequent in the right coronary cusp than in the other cusps. Ultrastructural study showed that these lesions develop as consequences of breakdown of collagen at the free edges of the cusps, usually near the commissures. Type II lesions consisted of linear perforations that extended along the basal regions of the cusps, forming an arc parallel to the sewing ring. These lesions were uncommon an resulted from separation of bundles of collagen. Type III lesions, which were large, round or oval perforations that occupied central regions of the cusps, were more common in aortic than in mitral bioprostheses. They were characterized by marked destruction of cuspal tissue and were most frequently associated with infection. Type IV lesions were small pinhole-like perforations; they usually were multiple, localized in central regions of the cusps and associated with calcific deposits. Type IV lesions were more common in mitral than in aortic bioprostheses. Regardless of position, they were more frequent in the left and noncoronary cusps than in the right coronary cusp (which may be protected by its muscle shelf against this type of perforation). It is concluded that cuspal tears and perforations develop in implanted bioprostheses as consequences of structural failure of connective tissue components.

Occurrence and significance of endothelial cells in implanted porcine bioprosthetic valves.

Histologic and scanning and transmission electron microscopic studies were made to determine the frequency of occurrence of endothelial cells in 49 porcine valve bioprostheses removed from 43 patients 2 days to 113 months (average 35 months) after implantation. Endothelial cells were found in none of 17 bioprostheses in place for less than 1 year, in 5 (23 percent) of 22 in place for 1 to 5 years and in 7 (70 percent) of 10 in place for longer than 5 years. The 12 bioprostheses in which endothelial cells were present had been implanted in the atrioventricular position (7 of 32 in the mitral position and 5 of 6 in the tricuspid position) for 21 to 113 months (average 71). Endothelial cells were not found in any of 11 bioprostheses implanted in the semilunar position (9 in the aortic position and 2 in pulmonary conduits); however, all but one of these bioprostheses had been in place for less than 5 years. Endothelial cells were concentrated along the basal regions of the cusps. These cells did not grow in direct contact with valve collagen, but were attached to fibrin, thrombi or fibroelastic host tissue (fibrous sheath) on the valve surfaces. The growth of endothelial cells and associated fibrous tissue may serve to increase the structural stability of bioprosthetic valve cusps, which may be of functional importance several years after implantation when the porcine connective tissue may have undergone significant deterioration.

Structure of bovine parietal pericardium and of unimplanted Ionescu-Shiley pericardial valvular bioprostheses.

To obtain a basis for the evaluation of postimplantation changes in bioprostheses made of parietal pericardium, we conducted comparative histologic, scanning and transmission electron microscopic studies of the structure of (1) normal bovine parietal pericardium, (2) glutaraldehyde-treated pericardial patches to be used for repair of cardiac defects, and (3) pericardial tissue cusps of unimplanted Ionescu-Shiley valves. Bovine parietal pericardium has three layers: (1) the serosa, or mesothelial cell layer; (2) the fibrosa, formed by diversely oriented, wavy bundles of collagen and by elastic fibers, and (3) the epipericardial connective tissue layer, which is partly continuous with the pericardiosternal ligaments. Pericardial patches and pericardial bioprosthetic cusps differ from normal pericardium by being denuded of mesothelium but they have normal degrees of waviness in their collagen. In Ionescu-Shiley valves, the inflow and outflow surfaces of each cusp correspond to the epipericardial and serosal surfaces of parietal pericardium, respectively. The inflow surfaces have a coarse texture, characterized by large bundles of collagen, and the outflow surfaces have numerous grooves, 10 to 30 mu in width and 20 mu in depth, which probably result from pressure exerted on the cuspidal surfaces by cotton material either during manufacturing or packing of the valves. Comparisons of the structure of bioprosthetic pericardial cusps and porcine aortic valve cusps show that the latter have reduced degrees of collagen waviness and a different layered structure: A layer similar to the spongiosa of aortic valve cusps is not present in pericardium. The functional implications of these observations are discussed in detail.