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At least 595 records · Page 33Linked to original sources
PubMed1991

Blood rheology after cardiac valve replacement with mechanical prostheses or bioprostheses.

Arterial thromboembolism is a serious complication in patients after heart valve replacement. Abnormalities in blood rheology may contribute to this complication. Therefore, the aim of this study was to compare various determinants of blood rheology in patients with substitute heart valves with those in healthy controls; furthermore, differences between patients with mechanical valves and those with bioprostheses should be investigated. The hemorrheologic determinants--fibrinogen, plasma viscosity, red cell aggregation, hematocrit and platelet aggregation--were studied in 92 patients with mechanical bileaflet valves, in 28 patients with bioprostheses and in 29 control subjects; the time since valve replacement was greater than or equal to 9 months. Fibrinogen, plasma viscosity, red cell and spontaneous platelet aggregation were found to be increased in all patients after heart valve replacement compared with normal subjects (fibrinogen: 348 +/- 87 vs 267 +/- 66 mg/dl, p less than 0.01; plasma viscosity: 1.71 +/- 0.1 vs 1.66 +/- 0.1 mPas, p less than 0.05; red cell aggregation: 9.9 +/- 2 vs 7.8 +/- 2 U, p less than 0.01; platelet aggregation: 22 +/- 15 vs 13 +/- 13%, p less than 0.01); among patients, fibrinogen, plasma viscosity and spontaneous platelet aggregation were higher in mechanical valves than in bioprostheses (fibrinogen: 359 +/- 95 vs 314 +/- 41 mg/dl, p less than 0.01; plasma viscosity: 1.72 +/- 0.1 vs 1.68 +/- 0.1 mPas, p less than 0.1; platelet aggregation: 23 +/- 15 vs 16 +/- 11%; p less than 0.05), whereas no difference could be found for red cell aggregation (9.7 +/- 2 vs 10.5 +/- 2%, p greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Bioprosthesis↗
PubMed1992

Value of exercise Doppler echocardiography in patients with prosthetic or bioprosthetic cardiac valves.

Doppler echocardiographic evaluation of the prosthetic valve function is usually performed at rest, although this situation is not representative for patients' daily activities. Therefore, a symptom-limited Master 2-step test was performed in 61 asymptomatic patients with normal left ventricular function. No adequate Doppler signals were obtained in 5 of 61 patients (8%) within 60 second after termination of exercise. In patients with aortic valve prostheses (n = 24), heart rate increased from 74 +/- 10 to 105 +/- 18 beats/min, the maximal instantaneous gradient from 44 (range 22 to 90) to 68 (range 28 to 165) mm Hg (r = 0.89) and the mean gradient from 24 (range 12 to 50) to 39 (range 18 to 100) mm Hg (r = 0.90). In 6 of 11 patients with a maximal flow velocity ratio between the left ventricular outflow tract and the aortic valve prosthesis less than or equal to 0.25, the mean gradient increased to a value greater than or equal to 50 mm Hg after exercise, whereas in patients with a ratio of greater than or equal to 0.25, this never occurred. In patients with mitral valve prostheses (n = 39), heart rate increased from 80 +/- 12 to 116 +/- 14 beats/min and mean gradient from 6 (range 3 to 10) to 14 (range 6 to 25) mm Hg (r = 0.59). The correlation of the mean diastolic pressure gradient after exercise with pressure half-time was 0.66. Systolic pulmonary artery pressure at rest and after exercise could be determined in 22 of 39 patients (56%) and increased from 34 (range 20 to 70) to 57 (range 35 to 110) mm Hg. It is concluded that the response to exercise can, to a large extent, be inferred from Doppler parameters at rest, particularly in patients with aortic valve prostheses. The clinical implication of the high gradients found in some asymptomatic patients in the present study should be elucidated by follow-up studies.

Adolescent↗
PubMed1989

Cardiac valve replacement in the elderly: clinical performance of biological prostheses.

From 1975 to 1987, 1,127 elderly patients underwent 1,223 valve replacements with the Carpentier-Edwards standard or supraannular porcine bioprostheses in 1,147 operations. Of the total patient population seen during these years, 33.5% receiving a standard porcine bioprosthesis and 48.6% receiving a supraannular bioprosthesis were 65 years of age or older. Of this elderly patient population, 465 patients were between 65 and 69 years old; 618 patients, 70 and 79 years old; and 52 patients, 80 years old and older. Aortic valve replacement was performed in 635 patients, mitral valve replacement in 417 patients, tricuspid valve replacement in 2 patients, and multiple-valve replacement in 80 patients. The cumulative follow-up was 3,957 patient-years. Early mortality was 9.5%: 7.3% for the 65- to 69-year-old group, 10.7% for the 70- to 79-year-old group, and 15.4% for the group 80 years old and older. Late mortality was 5.5% per patient-year: 4.2% per patient-year for the 65- to 69-year-old group, 6.3% per patient-year for the 70- to 79-year-old group, and 14.1% per patient-year for the group 80 years old and older. Valve-related causes contributed to 7 early deaths and 33 late deaths. The overall patient survival, including operative deaths, was 70.7% +/- 1.6% at 5 years and 47.8% +/- 3.7% at 10 and 12 years. The freedom from all valve-related complications was 52.1% +/- 6.1% at 10 and 12 years. The overall rate of valve-related complications was 5.0% per patient-year (fatal complications, 1.13% per patient-year). The overall rate of thromboembolism was 2.3% per patient-year and the freedom from thromboembolism, 69.6% +/- 5.2% at 10 and 12 years. The freedom from structural valve deterioration was 80.8% +/- 8.1% at 10 and 12 years: 71.7% +/- 11.0% at 10 and 12 years for the 65- to 69-year-old group, 97.9% +/- 1.2% at 10 years for the 70- to 79-year-old group, and 100% at 12 years for the group 80 years old and older. At 10 and 12 years, the freedom from valve-related death was 83.7% +/- 4.3% and the freedom from reoperation, 73.3% +/- 8.6%. The freedom from valve-related death, residual morbidity from thromboembolism and anticoagulant-related hemorrhage, and reoperation was 61.7% +/- 7.0% at 10 and 12 years. The clinical performance of porcine bioprostheses in the elderly patient population has been excellent. The early mortality increases in patients 70 years old or older.(ABSTRACT TRUNCATED AT 400 WORDS)

Age Factors↗
PubMed1995

Structure-function correlations in cryopreserved allograft cardiac valves.

This communication briefly summarizes a morphologic investigation of explanted cryopreserved heart valves and discusses the findings in the context of ongoing debates regarding modes of failure, cellular viability, durability of the extracellular matrix, and the contribution of immune responses. We studied 20 cryopreserved human heart valve allografts functioning up to 9 years as either orthotopic aortic valves/root replacements or right ventricle-to-pulmonary artery conduits explanted for valve failure, infection, or growth-related conduit or valve stenosis. Implanted valves had progressively severe loss of normal layered structure and were devoid of stainable deep connective tissue cells. Inflammation was minimal. Other late findings included minimal inflammation, mild cuspal hematomas, mural thrombus, and calcification, most prominent in the aortic wall. Transmission electron microscopy of late explants revealed nonviable cells and their debris, and a collagenous skeleton that was largely intact. We conclude that cryopreserved allograft heart valves have minimal, if any, viable cells, but largely retain the original collagen network; preservation of the autolysis-resistant collagenous skeleton likely provides the structural basis of function. Our results also suggest that immune responsiveness has little, if any, impact on late allograft function or degradation.

Adolescent↗