Hemolytic anemia in series 2300 and 2310 Starr-Edwards prosthetic valves

Mechanisms of hemolysis with mitral prosthetic regurgitation. Study using transesophageal echocardiography and fluid dynamic simulation

OBJECTIVES

The aims of this study were to define the hydrodynamic mechanisms involved in the occurrence of hemolysis in prosthetic mitral valve regurgitation and to reproduce them in a numeric simulation model in order to estimate peak shear stress.

BACKGROUND

Although in vitro studies have demonstrated that shear stresses > 3,000 dynes/cm2 are associated with significant erythrocyte destruction, it is not known whether these values can occur in vivo in conditions of abnormal prosthetic regurgitant flow.

METHODS

We studied 27 patients undergoing reoperation for significant mitral prosthetic regurgitation, 16 with and 11 without hemolysis. We classified the origin and geometry of the regurgitant jets by using transesophageal echocardiography. By using the physical and morphologic characteristics defined, several hydrodynamic patterns were simulated numerically to determine shear rates.

RESULTS

Eight (50%) of the 16 patients with hemolysis had paravalvular leaks and the other 8 had a jet with central origin, in contrast to 2 (18%) and 9 (82%), respectively, of the 11 patients without hemolysis (p = 0.12, power 0.38). Patients with hemolysis had patterns of flow fragmentation (n = 2), collision (n = 11) or rapid acceleration (n = 3), whereas those without hemolysis had either free jets (n = 7) or slow deceleration (n = 4) (p < 0.001, power 0.99). Numeric simulation demonstrated peak shear rates of 6,000, 4,500, 4,500, 925 and 950 dynes/cm2 in these five models, respectively.

CONCLUSIONS

The distinct patterns of regurgitant flow seen in these patients with mitral prosthetic hemolysis were associated with rapid acceleration and deceleration or high peak shear rates, or both. The nature of the flow disturbance produced by the prosthetic regurgitant lesion and the resultant increase in shear stress are more important than the site of origin of the flow disturbance in producing clinical hemolysis.

Prosthetic heart valves: a review

There are a number of difficulties inherent in the analysis of such a large and diverse quantity of data. In a substantial number of clinical trials, there is no significant effort made to evaluate prosthetic performance as a function of preoperative cardiac anatomy. Hemodynamics have not been systematically studied in relation to preexisting left ventricular size, shape, or configuration, mitral annular orientation, or left atrial size. Postoperative anticoagulation protocols vary from one institution to another and occasionally within study groups themselves. Less tangible variables such as alteration in surgical technique over time and differential familiarity of cardiovascular surgeons with the prostheses employed are chronic problems in any study of this sort. Perhaps the greatest variable in evaluating the postoperative performance of valvular prostheses over the past 20 yr is the radical improvement in techniques of intraoperative myocardial preservation. Notwithstanding, comparisons are possible within the confines of certain criteria. The caged ball value remains in use after 20 years of clinical experience. It has sustained the greatest number of modifications, probably because it has been the most extensively studied. Hemodynamics are adequate although its centrally obstructed design is responsible for increased turbulence, hemolysis, and neointimal proliferation, particularly in the aortic position. The device has been shown to be durable with virtually no reports of ball variance since the alteration of the silicone curing procedure in 1965. Thromboembolic rates are acceptable in the anticoagulated patient while prosthetic thrombosis is not a grave threat in the non-close clearance device. Incidence of endocarditis is not particularly different from that associated with all nonbioprosthetic valves, although there is a much greater published volume of clinical experience concerning recognition and treatment of late prosthetic valve endocarditis in patients with caged ball valves than there is for any other replacement device. Perhaps the most serious disadvantage to caged ball design is its size. Its large spatial requirements have led to anatomic complications in patients with small aortic roots, isolated mitral stenosis, left ventricular hypertrophy, and double valve replacement, among others. Nevertheless, this is still the valve of choice in some centers.(ABSTRACT TRUNCATED AT 400 WORDS)

Indexes of intravascular hemolysis, quantification of coagulation factors, and platelet survival in patients with porcine heterograft valves

Ten patients with porcine heterograft valves who were not receiving anticoagulant agents were evaluated to determine the effect of the valve on red blood cell survival and on platelet activation and consumption as measured by (1) quantification of the coagulation mechanism, (2) platelet function studies, and (3) 51-chromium platelet survival time. There was no evidence of significant intravascular hemolysis as determined by the reticulocyte count, serum iron and iron binding capacity, serum bilirubin level, or lactic dehydrogenase activity. The coagulation profile and the platelet function studies were normal. No statistically significant difference was found in the platelet survival time in the 10 patients with porcine heterograft valves (half-life 3.2 +/- 0.8 days) and the 11 normal control subjects (half-life 3.6 +/- 0.6 days) (p greater than 0.2). The finding of a normal platelet survival time in patients with porcine heterograft valves is consistent with clinical experience indicating that this device is associated with a low incidence of systemic embolization, approximating 3% per year.

The clinical life history of explanted prosthetic heart valves

This report analyzes 118 prosthetic heart valves obtained from 97 patients at reoperation (96) or at postmortem examination (22). The number obtained from the mitral, aortic, and tricuspid positions were 78, 32, and 8, respectively. Duration of implant ranged from one day to 12.3 years. Valves showing the least long-term wear were the Starr-Edwards metal strut-silicone bell and the Björk-Shiley. Moderate long-term durability was provided by the Beall and Starr-Edwards cloth-covered composite-seat prostheses while short-term durability was given by Hancock and Carpentier valves. Reoperation for valve-related causes was performed for 46 of 47 Beall valves, which demonstrated stenosis, hemolysis, and incompetence from component wear, 6 of 27 Björk-Shiley prostheses for valve thrombosis or thromboembolism or both, and 11 of 17 porcine prostheses because of calcification (4) or cusp perforation or rupture. Analyses of wear and fatigue of mechanical valves demonstrated that use of ultrahard materials (pyrolyte carbon, titanium, stellite 21) provided superior durability in contrast to polymeric solids or fabrics with poor abrasion and impact characteristics. Further, cloth and disc wear were evident as early as 0.5 year after implant and appeared to be complete by 4 years. Completeness of healing after 24 months was not related to the type of fabric material used or its construction. This study suggests that mechanical valves made from hard materials have long durability when properly implanted and require fastidious prophylaxis against infection and thromboembolism. The findings of early cusp perforation or rupture in the aortic position and leaflet calcification, stiffening, or disruption in the mitral position for porcine prostheses suggest that frequent and careful examinations of patients with these prostheses are required to detect early signs of stenosis or incompetence and that early reoperation is required before catastrophic valve failure necessitates emergency prosthetic valve replacement.

Durability of prosthetic heart valves

Accelerated fatigue testing of clinical heart valves has been performed at cyclic rates of 33 to 35 cycles per second at 37 degrees C using water for non-biological valves and glutaraldehyde solutions for tissue valves. Flows were in the physiological range, and the pressure difference across each valve during closure was 100 +/- 25 mm Hg. The results showed that major fatigue occurred for the Starr-Edwards 2320 at 150 million cycles, the Hufnagel trileaflet at 124 million cycles, the Björk-Shiley Delrin disc at 140, the Björk-Shiley Pyrolite disc at 973, the Beall 103 at 60, the Hancock porcine at 62, the Carpentier-Edwards porcine at 34, and the Ionescu-Shiley porcine pericardial prosthesis at 65 million cycles. The Lillehei-Kaster was removed after 762 million cycles without discernible wear. Three facts emerged from the testing data: (1) the component worn in vitro wears in vivo; (2) the sites of in vitro fatigue on the component are identical to clinical specimens; and (3) those valves that have high durability in vitro have given similar performance in patients. The in vitro and clinical data for tissue valves do not correlate. The possible reasons for the discrepancy are discussed, and a note of caution is made regarding realistic expectations of clinical durability of tissue valves.

Experimental evaluation of mechanical haemolysis with Starr-Edwards, Kay-Shiley and Björk-Shiley valves

Mechanical cell damage was studied in vitro with three types of prostheses: Starr-Edwards, Kay-Shiley and Björk-Shiley valves. Mechanical cell damage was found to be closely related to the flow characteristics in the prosthesis. Considering valves of similar orifice diameter, Björk-Shiley valves produced the lowest rate of haemolysis. This is due to the improved haemodynamic characteristics of the valve which resulted from the laminar type of flow. With Starr-Edwards valves, smaller sizes produced unacceptably high rates of haemolysis. Increasing the mean forward flow across the valve resulted in a disproportionate rise in the energy loss and the rate of haemolysis when compared with Björk-Shiley valves of similar annulus diameters.

Diagnosis and management of complications of prosthetic heart valves

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.

Coronary ostial stenosis, a complication of aortic valve replacement

Eight patients developing coronary ostial stenosis following Starr-Edwards aortic valve placement are reviewed. Coronary perfusion with a balloon tip perfusion catheter was performed during the intraoperative period on all patients and was considered technically satisfactory. Angina pectoris developed within six months of surgery in seven of eight patients and left main coronary artery occlusive disease was demonstrated in each of these cases. One patient who did not develop angina pectoris had right coronary artery narrowing without intraoperative perfusion of this vessel. All patients were reoperated, five survived, two are free of symptoms. Coronary ostial stenosis is a clinically recognizable complication of aortic valve replacement with potential for surgical correction.