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Allograft heart valves obtained from donor hearts have been cryopreserved in the Heart Valve Bank in Rotterdam for transplantation purposes. In contrast to hepatitis B screening of organ donors, which consists of only a rapid HBV surface antigen (HBsAg) assay, tissue donors can be screened more completely for hepatitis B virus (HBV) by HBsAg and antibodies against HBV core antigen (anti-HBc) tests, and when necessary, anti-HBs and HBV-DNA tests. The value of this complete HBV screening was investigated by evaluation of the HBV screening results of 676 donor sera. HBsAg was positive in 1 serum. Anti-HBc was positive in 63 sera, of which 52 also had positive antibodies against HBV surface antigen (anti-HBs) tests (no risk of transmission) and 10 had negative anti-HBs tests. In 3 cases with a negative anti-HBs test the HBV-DNA test was positive (risk of transmission). In 3 cases not enough serum was available to perform all tests, resulting in a total of 7 rejected donors. Single HBsAg testing would have resulted in the rejection of only 1 donor. In the presented group of selected donors, approximately 0.5% of the HBsAg-negative donors were lower-level chronic carriers of hepatitis B. Complete HBV screening decreases the risk of transmission of hepatitis B in allograft heart valve transplantation.
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Experience with tissue valves for heart valve replacement over the past seven years is presented and analyzed. Between February 1967 and March 1969, 87 patients had heart valves replaced with preserved heterologous aortic valves. Valve failure occurred in 19 of the 70 operative survivors. There are 45 long-term survivors with heterologous aortic valves; 10 have regurgitant murmurs and 35 have valves functioning normally. Microscopic examination of failed valves has shown that the heterologous aortic valve gradually becomes a mechanically vulnerable structure in a state of rejection. During the past five years. autologous and homologous fascia lata and heterologous pericardium, mounted on a support frame, were used in 241 patients (131 aortic, 103 mitral and seven tricuspid). The follow-up period for the fascia lata group was 40 to 62 months and for the pericardial group 7 to 39 months. There have been significant differences in valve function with regard to both the site of valve insertion and the type of tissue used. Pericardial valves in the aortic position have produced the best results and autologous fascial valves in the mitral position, the worst. Valve failure occurred in only six patients, all with autologous fascia in the mitral position. The incidence of thromboembolism in the entire series was very low even though anticoagulants were not used. Analysis of clinical and hemodynamic results has shown that preserved heterologous pericardium has the potential for an adequate heart valve substitute.
Until now, we have estimated cavitation for mechanical heart valves (MHV) mounted in an electrohydraulic total artificial heart (EHTAH) with tap water. However, tap water at room temperature is not a proper substitute for blood at 37 degrees C. We therefore investigated fluid characterization in studies of MHV cavitation associated with the viscosity and nuclei content of a testing fluid. We used the Medtronic Hall valve mounted in the mitral position of the EHTAH. As testing fluids, tap water, distilled water, and glycerin solution were used. The valve-closing velocity, pressure-drop measurements, and a high-speed video camera were employed to determine the cavitation intensity in MHV. Most of the cavitation bubbles were observed at the edge of the valve stop. Our analysis of the results indicates that squeeze flow is the major cause of cavitation in the Medtronic Hall valve. The cavitation intensity increased with increases in the fluid viscosity and the valve-closing velocity. Even if cavitation intensity in glycerin solution was greater, the cavitation occurrence probability was less in glycerin solution than in tap water. Our results suggest that tap water contains particles that cause an increase in the cavitation occurrence probability. We conclude that cavitation intensity is greatly affected by the nuclei concentration in the fluid and the fluid viscosity.
The American Heart Association (AHA) has published guidelines for use of prophylactic antibiotics to prevent bacterial endocarditis, but few data are available about physician compliance with these guidelines. A retrospective review was conducted of the use of prophylactic antibiotics in patients with prosthetic heart valves who were undergoing diagnostic or operative procedures or heart catheterization at three hospitals. Compliance with AHA recommendations was only 30 percent (14 of 46) for procedures considered high risk for patients with prosthetic heart valves. Six (23 percent) of 26 patients who underwent right or left heart catheterization received prophylactic antibiotics (not recommended by AHA). Antibiotics were given to 42 (74 percent) of 57 patients who underwent surgical procedures considered at low risk of bacteremia, but only 33 (58 percent) received antibiotics that cover organisms commonly present at the site of the procedure. The results indicate that clinicians frequently do not administer prophylactic antibiotics in patients with prosthetic heart valves who are undergoing invasive procedures or do not follow published AHA guidelines when antibiotics are administered.
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Twenty-five patients who had repeated thromboemboli from a prosthetic mitral valve were treated with reoperation using a tissue valve prosthesis. Reoperation was performed an average of 4.0 years after the original valve replacement in 14 men and 11 women, with an average age of 50 (range 35 to 65) years. A stented allograft was used in the first 7 patients and a porcine xenograft in the last 18 patients. There were one hospital death and two late deaths. With the first prosthetic valve there were 66 documented embolic episodes in 101.5 patient years (0.65 embolus/year). Only four embolic episodes in 67.4 patient years (0.059 embolus/year) occurred after tissue valve replacement (P less than 0.001). These results indicate that in patients with recurrent or severe embolization after prosthetic heart valve replacement, rereplacement with a tissue prosthesis can be safely performed and significantly reduces the likelihood that additional embolic episodes will occur.
Current heart valve prostheses may be classified as either mechanical or tissue valves (bioprostheses). The principal advantage of mechanical devices is their established long-term durability; however, chronic anticoagulation is recommended to reduce the incidence of thromboembolic complications. Tissue valves are associated with a relatively low rate of thromboembolism but their durability level has not been determined. All contemporary prosthetic heart valves yield comparable survival rates.
The ideal heart valve prosthesis has not been developed. The today available mechanical and biological prostheses are far from perfect concerning thrombogenesis, mechanical durability and hemodynamic performance. Failure of an implanted valve is possible due to inadequate indication, inadequate surgical technique and inadequate medical follow-up. The patient with a heart valve prosthesis must be seen as a life-long challenge for the cooperation between cardiologists and cardiac surgeons. This article describes the main causes of prosthetic heart valve dysfunction and the surgical treatment, including structural dysfunction, thrombosis, paravalvular leakage, tissue ingrowth and prosthetic valve endocarditis.
Recently, cavitation on the surface of mechanical heart valves has been studied as a cause of fractures occurring in implanted mechanical heart valves. In this study, to investigate the mechanism of cavitation bubbles associated with monoleaflet mitral valves in an electrohydraulic total artificial heart (EHTAH), and to select the best valves for our EHTAH system, we measured three parameters. First, an image was created of the cavitation bubbles using a high-speed camera. Second, pressure drop in the vicinity of the valve surface was measured using mini pressure sensor. Then, the closing of the valve was observed using a Laser displacement sensor. Most of the cavitation bubbles in the Medtronic Hall valve were observed at the edge of the valve stop. With the Omnicarbon valve, the cavitation bubbles were observed at the edge of the valve and on the inner side of the leaflet. On the other hand, cavitation bubbles were observed only on the inner side of the leaflet in Björk-Shiley valve. Cavitation bubbles concentrated on the edge of the valve stop; the major cause of these cavitation bubbles was determined to be the squeeze flow. The formation of cavitation bubbles depended on the valve closing velocity and the valve leaflet geometry. From a viewpoint of squeeze flow, a low closing velocity and a small size of the valve stop could minimize cavitation.
Strut fracture with embolization of the valve disk has been reported worldwide in about 550 cases out of a total of 86,000 implanted Björk-Shiley convexo-concave disk valves. 320 of the patients died. In Norway six cases of strut fracture are reported, with five deaths. The highest risk is reported for valves with a 70 degree opening of the disk. Other risk factors are large valves in the mitral position, valves produced in the year 1981 and early 1982, and valves welded by inexperienced welders. A joint lawsuit which was started in January 1992 on behalf of all living patients with a CC-valve has been concluded and has resulted in a legal settlement between the parties.
One hundred fifty four patients underwent isolated mitral valve replacement with bioprosthetic heart valve at Hyogo Medical College Hospital from November 1973 to December 1998. A porcine bioprosthetic valve was replaced in 82 patients (Hancock 43, Carpentier-Edwards 26, Hancock II 13) and pericardial bioprosthetic valve in 72 patients (Ionescue-Shiley 39, Carpentier-Edwards 33) with a mean follow-up of 1,410 patients-years. Their thromboembolism rates were also analyzed in linear and actuarial term over the 15-year period. The incidence of thromboembolism rate was 2.5%/pt.yr. Thromboembolic free rates for patients with anticoagulant therapy were significantly decreased for patients without therapy. Thromboembolic free rates for patients with atrial fibliration were also were significantly decreased for patients with sinus rhythm because the patients with sinus rhythm were not on anticoagulant therapy. In conclusion, it is necessary for the all patients to be on anticoagulant therapy after mitral valve replacement with bioprosthetic valves, even though patients with sinus rhythm.
Heart valve diseases have a significant high mortality, and the valve replacement using glutaraldehyde crosslinked porcine heart valves is one of the main curing techniques. But its application is limited due to poor durability, calcification of the valves and immunogenic reactions. The aim of this study was to evaluate the crosslinking effect of procyanidins on porcine heart valve matrix. After crosslinking of the decellularized porcine aortic heart valves by procyanidins, the tensile strength, the in vitro enzymatic degradation resistance, procyanidins release from the crosslinked materials and the cytotoxicity of procyanidins to heart valvular interstitial cells were examined. The results showed that the tensile strength of procyanidins crosslinked valve matrix was higher than that of glutaraldehyde crosslinked valve matrix. Valve matrix crosslinked by 10 mg/ml procyanidins could be stored in D-Hanks solution for at least 45 days without any decline in ultimate tensile strength and maintained the elasticity as the fresh valves. Furthermore, procyanidins was found to release when the crosslinked tissue stored in D-Hanks solution. The release rate was high during the first 4 days and then dramatically decreased thereafter. During releasing phase, the concentration of procyanidins was no toxicity to heart valve interstitial cells. In vitro enzymatic degradation revealed that crosslinked matrix could resist the enzymatic hydrolysis, and the resistant capacity was approximately the same as glutaraldehyde crosslinked valve matrix. This study shows that procyanidins can crosslink porcine heart valves effectively without toxicity. Our results suggested that this method might be a useful approach for preparation of bioprosthetic heart valve.
Complications after heart valve replacement remain a substantial source of morbidity and mortality despite continuing advances in surgical care and prosthetic design. Infectious endocarditis occurs in about 4 percent of patients and may appear early (within 60 days) or late after operation. Endocarditis of early onset is commonly due to staphylococcal, fungal or gram-negative organisms and is fatal in 70 percent or more of cases. Infection of late onset is more often of streptococcal origin and the mortality rate is lower, about 35 percent. With either type, prompt recognition, vigorous and appropriate antimicrobial therapy and early consideration of surgical intervention are crucial. The postperfusion and postpericardiotomy syndromes are relatively common and relatively benign syndromes associated with postoperative fever. Their recognition is important to prevent confusion with endocarditis or sepsis and thus to reassure the patient and physician. Treatment is primarily symptomatic. Intravascular hemolysis occurs with most prosthetic heart valves but is more common with certain prostheses and with paraprosthetic valve regurgitation, with significant hemolytic anemia in 5 to 15 percent. Oral iron replacement therapy is effective in the majority of patients, but occasionally blood transfusion or reoperation for leak around the prosthesis is necessary. Prosthesis dysfunction due to thrombus may be recognized clinically by recurrence of heart failure, syncope, cardiomegaly and altered prosthetic valve sounds or new murmurs. Hemodynamic studies verify the diagnosis, and prompt reoperation is indicated for this potentially lethal problem. Systemic embolization has decreased markedly with the introduction of cloth-covered prostheses and is frequently related to erratic or ineffective anticoagulant therapy. We continue to recommend anticoagulant therapy for all patients with prosthetic heart valves unless there is a major contraindication.