Reoperations on cardiac valves.

As the number of patients undergoing cardiac valve replacement has grown, valve reoperations have become increasingly frequent. The newer generations of mechanical valves are far more efficient and freer from structural failure than the older ones. However, other valve and non-valve related complications still constitute a major cause of morbidity and mortality. On the other hand, bioprostheses, implanted in large numbers in the 1970's and early 1980's, have now gone into the second decade of life since implantation, when biodegradation becomes more frequent. Reoperations are technically more demanding than the original valve procedures because of the mediastinal and pericardial adhesions and the condition of the anulus after removal of the previous prosthesis. Greater awareness of the most dangerous steps and refinements to surgical technique have contributed to the decreased mortality observed in recent years. The risk is higher in certain conditions, such as the presence of prosthetic valve endocarditis and the patient being operated on an emergency basis in NYHA functional class IV. It may also be increased in females and the elderly. Multiple reoperations also carry a higher risk in most surgeon's experience. However, elective reoperations for defective mechanical valves and for replacement of a previously repaired mitral valve carry similar mortality rates to primary valve replacement procedures. The global mortality rates have not been significantly higher in the hands of experienced surgeons working in centers where reoperations are performed frequently. In smaller series high mortality rates are a constant, which underscores the importance of the learning curve. The indications for reoperation must therefore consider all risk factors and, when possible, the procedure must be performed by those who have the most experience. Under these circumstances, elective re-replacement of degenerating bioprostheses and of defective mechanical valves in asymptomatic patients may be advisable.     

Trauma to cardiac valves

Cardiorrhaphy is a relatively common procedure performed in a trauma center. However, there is a subgroup of patients with more complicated cardiac injuries such as coronary artery injuries, septal defects, and valvular injuries. Cardiac valvular injuries are often diagnosed subacutely when a new murmur is heard. Transesophageal echocardiography has been increasingly performed to diagnosis these injuries and may be helpful intraoperatively. Cardiac catheterization may be indicated in selected patients. Techniques to address these injuries may involve repair or prosthetic replacement. A high index of suspicion is needed to diagnose these relatively rare injuries.     

Echocardiographic evaluation of prosthetic cardiac valves

Comprehensive echocardiographic examination of patients with prosthetic cardiac valves using M-mode, two-dimensional, conventional, and color Doppler echocardiography represents an invaluable clinical tool in the serial follow-up of these patients. A thorough knowledge of these techniques and their limitations allows accurate assessment and prevention of misdiagnoses.     

Results of replacement of cardiac valves by homologous dura mater valves.

Homologous dura mater valve was employed in a series of 533 patients in the period between January 1971 and May 1974. The dura mater was sterilized and preserved in 98 percent glycerol solution at room temperature. Important data were the following (1) no significant pressure gradient through the vale at rest; (2) no bacterial endocarditis; (3) two cases of fungal endocarditis; (4) no degeneration or retraction of the leaflets; (5) no thrombus formation in the valve; and (6) no anticoagulants were used in this series.     

Platelet adherence to bioprosthetic cardiac valves

Tissue from porcine aortic bioprosthetic valves (Hancock) and bovine pericardial valves (Ionescu-Shiley) were incubated with platelets tagged with chromium-51. There was a significantly decreased platelet-collagen adhesion reaction in both porcine and bovine glutaraldehyde-treated valves compared with reactions in fresh porcine aortic valve and fresh bovine pericardium (p less than 0.001). There was no significant difference in the platelet-collagen reaction between porcine aortic valve and bovine pericardium, whether treated with glutaraldehyde or in the fresh state (p greater than 0.05). The addition of aspirin did not significantly decrease the platelet-collagen reaction on glutaraldehyde-treated or fresh valves (p greater than 0.05). Rinsing fresh valves in plasma appeared to offer more protection against platelet adhesion than rinsing them in saline solution (p less than 0.01). It is concluded that there is no difference in platelet adherence to porcine aortic valve or bovine pericardium and that glutaraldehyde, and perhaps plasma, offers a protective effect against platelet adhesion.     

Lack of Rhesus antigen expression by human committed erythroid progenitors

The D antigen of the Rhesus blood group, an erythroid-specific cell surface marker, is expressed by all morphologically recognizable human nucleated red blood cell precursors including, in low density, the pronormoblast. The object of the present study was to determine the expression of the D antigen by committed erythroid progenitors. Under conditions that produced complete inhibition of BFU-E and CFU-E by known cytotoxic antisera, no significant inhibition was produced by anti-D. Use of anti-human IgG (rabbit) to increase sensitivity and trypsinization to reveal cryptic Rh determinants were both without inhibitory effect. Erythroid bursts and colonies grew normally in methylcellulose that contained anti-D. The addition of anti-D to day 7 BFU-E did not inhibit their proliferation to mature bursts at day 14. These results suggest that the D antigen is not expressed by human committed erythroid progenitor cells. The D antigen is therefore an erythroid-specific differentiation marker, rather than an erythroid- lineage-specific antigen. The development of expression of the D antigen during erythropoiesis parallels that of band 3 protein, to which anti-D has been reported to bind. Lack of Rh expression by committed erythroid progenitors is consistent with the rarity of red cell aplasia in Rhesus hemolytic disease of the newborn and in idiopathic and drug-induced autoimmune hemolytic anemia in which the autoantibodies have apparent Rh specificity. These results imply that Rh compatibility is not a contraindication to human bone marrow transplantation.     

Rheumatic involvement of all four cardiac valves

Rheumatic involvement of all four heart valves is rare. A 35 year old woman presented with gradually progressive exertional dyspnoea for the preceding 10 years. On evaluation she was in atrial fibrillation with congestive heart failure. Clinical examination found evidence of stenosis of the mitral aortic and tricuspid valves with a history of rheumatic fever in childhood. Transthoracic echocardiography showed the involvement of all four cardiac valves. Few reports are available in the literature describing rheumatic quadrivalvar damage. Operator awareness of possible rheumatic involvement of all four valves is essential for appropriate diagnosis.     

Localization and pattern of expression of extracellular matrix components in human heart valves

BACKGROUND AND AIM OF THE STUDY: The pattern of expression and distribution of extracellular matrix (ECM) components in human cardiac leaflets was analyzed. Additionally, interstitial cells (ICs) from the four different leaflets were isolated and studied. METHODS: Immunohistochemistry and immunocytochemistry were used for localization, and flow cytometric analysis to quantify the expression of specific markers on these ICs; the synthesis and expression of ECM components was assessed. RESULTS: Elastin was found predominantly on the inflow layer, but fine fibers were also present in the central and outflow layers. Collagen I was predominantly on the outflow layer but permeated throughout the leaflets. Collagen III was expressed ubiquitously. Proteoglycan expression was throughout the leaflet, but was predominant in the central layer. Fibronectin and vitronectin were expressed strongly in the inflow layer, moderately in the central layer, and weakly in the outflow layer. Biglycan expression was ubiquitous, with strong filamentous strands in the central layer. Keratan sulfate and decorin were ubiquitous. Chondroitin-4-sulfate and chondroitin-6-sulfate were strongly expressed in the outer layers, and laminin was restricted to the basal lamina of the endothelial cells. Cultured ICs showed synthesis and expression of various ECM components. CONCLUSION: This study of the pattern of expression of ECM components may provide a basis for a fingerprint on which to base future valve alternatives. The results provide useful information for valve tissue engineering and an understanding of the structural basis of some sophisticated functions of the valves.     

Low-intensity anticoagulation in mechanical cardiac prosthetic valves

Retrospectively, we reviewed the charts of 101 patients at the University of Kansas Medical Center who received low-intensity anticoagulation for mechanical prosthetic valves implanted over a 17-yr period. The mean duration of follow-up was 4.6 yr, and the total duration of follow-up was 466.5 patient-yr. The patients' records were evaluated for evidence of hemorrhagic or thromboembolic complications. A prothrombin time ratio of 1.3 to 1.5 times control was considered to be low-intensity anticoagulation. There were three thromboembolic events or 2.9/100 patient-yr of follow-up at a prothrombin time ratio of less than 1.3, four thromboembolic events or 2.5/100 patient-yr of follow-up at 1.3 to 1.5 times control, four thromboembolic events or 2.2/100 patient-yr of follow-up at 1.6 to 2.0 times control, and no thromboembolic events at prothrombin time ratios greater than 2.0 times control. Hemorrhagic events occurred in three patients at a prothrombin time ratio of less than 1.3 times control or 2.8/100 patient-yr of follow-up, in six patients at 1.3 to 1.5 times control or 3.8/100 patient-yr of follow-up, in ten patients at 1.6 to 2.0 times control or 5.5/100 patient-yr of followup, and in two patients at 2.1 to 2.5 times control or 12.2/100 patient-yr of follow-up. The rate of hemorrhagic events at 2.5 times control was 470/100 patient-yr follow-up. While not providing definitive proof, we believe that our retrospective study provides supportive evidence for the use of low-intensity anticoagulation in patients with mechanical cardiac prostheses.     

Incomplete differentiation of cardiac valves. Angiographic diagnosis

A case of incomplete differentiation of the cardiac valves is presented because of the antemortem demonstration of continuous visualization of the valvular structures on angiograms. We suggest that this angiographie finding in a child with congenital heart disease should raise the possibility of this lesion.