Artificial Cardiac Valves Research Articles

Influence of oxygen ventilation on Doppler microemboli signals in patients with artificial heart valves.

The purpose of this study was to evaluate the influence of inhalation of 100% oxygen on microembolic signal (MES) counts in patients with artificial cardiac valves. A total of 134 outpatients were examined. Transcranial Doppler baseline monitoring (45-minute duration) was performed in all patients under resting conditions. The first 30 patients subsequently underwent transcranial Doppler monitoring for at least 20 minutes under noninvasive positive pressure ventilation with 100% oxygen and for an additional 30 minutes under resting conditions. The same protocol was applied to all following patients with a baseline MES count > or = 10, while the examination was discontinued in the remaining patients. Baseline MES counts < 10, which remained unchanged during oxygen inhalation and the subsequent resting period, were observed in 26 of 30 initial patients. A total of 46 patients with MES counts > or = 10 were identified. Oxygen application was feasible in 43 patients. An exponential MES decrease was noted in 42 patients during oxygen inhalation (statistically significant in 38 patients), followed by a subsequent increase in 38 of 43 patients (statistically significant in 25 patients) under resting conditions. The exponential reduction of MES counts observed in this study corresponds to blood denitrogenation, thus strongly arguing for nitrogen bubbles as underlying embolic material in prosthetic valve carriers.

11a Thrombosis and embolism

Prevention offers the best approach to limiting morbidity and mortality from deep vein thrombosis and pulmonary embolism in obstetric patients. The use of anticoagulant drugs during pregnancy, however, can be problematic, from the maternal or the fetal point of view. Deciding on the best management is further limited by the lack of controlled clinical trials in the obstetric setting. From the data available, it can be recommended that anticoagulant prophylaxis should be targeted at groups of patients at high risk of thrombosis during pregnancy and the puerperium. Heparin is the agent of choice in most situations during pregnancy for the prophylaxis of venous thrombosis, while warfarin is still the most effective agent for the prevention of systemic embolism from artificial cardiac valves. Prophylactic measures against venous thrombosis are probably underused in the puerperium. Controlled clinical studies are urgently required to optimize prophylaxis of venous thromboembolism associated with pregnancy, and large studies may be more feasible in the puerperium when the incidence of thromboembolism is highest.

Survey of oral anticoagulant treatment in children.

To find out which children are treated with oral anticoagulants and how their treatment is controlled in the United Kingdom. Two questionnaires were used. The first was sent to general haematologists and the other to paediatric cardiologists and cardiac surgeons. There were 273 (58%) replies to the first questionnaire. Most children were treated because of artificial cardiac valve replacement. The mean target International Normalised Ratio (INR) used was 2.73 to 4.0 for children with heart valves and 2.1 to 3.25 for children with venous thrombosis. The second questionnaire elicited replies from 11 of 22 cardiac centres. The mean target INR used for children with cardiac valves ranged from 2.59-3.77. Of 68 children covered in the survey, there have been two major bleeds and two thrombotic episodes: 78.8% of children were controlled with a venous prothrombin time and 21.2% with a capillary test. There was no consistency in the dose regimens used for the induction of oral anticoagulant treatment with warfarin. The levels of anticoagulation used for maintenance are similar to those recommended by the British Society for Haematology for adults (3.0 to 4.5). They seem to be safe for children too.

Analysis of causes for wear and breakdown of elements in artificial cardiac valves of the disk type

In order to avoid the possibility of aggravated wear or breakdown of elements in disk-type ACV's it is necessary to provide for the rotation of the disk around an axis perpendicular to its plane, the centering of the disk within the valve housing, and the accurate matching of shape for the stopping elements of the housing with the shape of mating surfaces on the disk. The housing of each valve must be checked for the presence of internal flaws by means of nondestructive-inspection methods. A final quality check on the assembly of an ACV should be made during the mandatory tests on special test benches with a measurement of the basic functional parameters.

Phonocardiographic Characteristics of the St. Jude Prosthesis in the Aortic Position

immediately after it (Fig 2). It can be surmised that the early systolic sound observed in these patients may be related to max- imum excursion of the opening motion of the car- bon leaflets or turbulence created by transvalvular flow during left ventricular systole. The high fre- quency aortic closure sound is probably produced by coaptation of the leaflets and vibrations from the resonant prosthesis secondary to rapid decelera- tion of blood at end-systole. Other findings noted rji he St. Jude valvular prosthesis is a bileaflet pyro- lytic carbon device1 which is being implanted with increasing frequency. Knowledge of the aus- cultatory and phonocardiographic characteristics of artificial cardiac valves has proven to be useful in detecting their malfunction.� We describe here our observations on the phono- cardiographic features of the St. Jude prosthesis in the aortic position. Figure 1 shows the simultane- ously recorded carotid arterial pulse tracing, phono- cardiogram from the tricuspid area and lead 2 of the electrocardiogram from such a patient. The ma- jor component (M1) of the first heart sound com- plex is normal. An early systolic sound (ES) is present at the lower left sternal border. This sound is usually heard over the entire precordium, but is best recorded at the left parasternal location. The interval from the first heart sound to the opening or ejection sound ranges from 60 to 80 msec. Note that the ejection sound coincides in timing with the onset of the external carotid pulse upstroke. The aortic component (AC) of the second heart sound consists of a major high amplitude high frequency component followed by multiple lower amplitude medium to low frequency vibrations. This aortic closing sound is recorded in conjunction with the dicrotic notch of the external carotid pulse tracing. In all cases, the aortic closure sound was greater in amplitude than the opening ejection sound with an AC:ES amplitude ratio ranging from 5:1 to 8:1. Phonoechographic study indicates that the early systolic sound follows the opening point of the prosthetic leaflets by approximately 40 msec. The aortic component of the second heart sound is in- scribed at the time of ultrasonic valve closure or I 111111 I 11111111IIIIIIIIlII(IIIIl ltlJIjlIIIllII

Cloth-Particle Retinal Emboli from Artificial Cardiac Valves

Two patients with prosthetic mitral valves had ocular complications. A 28-year-old woman suffered recurrent episodes of bilateral retinal embolization and consequent loss of useful vision over a period of two years despite therapeutic anticoagulation. Replacement of the valve was followed by cessation of the embolization. A 52-year-old man noted the abrupt onset of blurred vision in his right eye. Visual acuity was 6/6 (20/20) bilaterally, but the right eye had many retinal emboli of varying shapes. Both patients had long-standing mitral valve disease, but ocular symptoms developed only after the implantation of a cloth-covered mitral valve prosthesis. To the best of our knowledge, retinal emboli from cloth-covered cardiac valve prostheses have not been previously reported. Patients with such prostheses and ocular complaints who have adequate anticoagulation therapy should be carefully examined for retinal emboli. If emboli are present, valve dysfunction is possible and valve replacement may be necessary.

Long-Term Follow-up of Artificial Valves in Patients under 15 Years Old

Forty-nine artificial cardiac valves implanted in 44 patients less than 15 years old were reviewed. Out of 49 valves, 16 were mechanical and 33 were xenografts. Average follow-up was 2 years 5 months. Marked valvular stenosis developed in 11 out of the 33 xenografts, an incidence of 15% per patient-year. In patients with a xenograft valve, the incidence of sepsis was found to be 4% per patient-year and brain accidents, 4% per patient-year. In patients with mechanical valves, the incidence of stenosis was only 2% per patient-year and brain accidents, 2% per patient-year. There was no sepsis. From these follow-up results, mechanical valves seem to be superior to xenografts when used in patients less than 15 years old.

Behaviour of magnesium in artificial cardiac valve replacement (author's transl)

Bei 46 Patienten im Alter von 19 bis 58 Jahren mit erworbenen Herzklappenfehlern, die sich dem prothetischen Herzklappenersatz mit Einsatz der Herz-Lungen-Maschine unterziehen mußten, wurden prä-, intra- und postoperative Bestimmungen der Serumkonzentrationen von Mg, Ca, K, Na und Cl durchgeführt. Gleichzeitig wurde geprüft, ob ein Zusammenhang mit dem Auftreten postoperativer Arrhythmien besteht. Die Patienten waren in Gruppen ohne und mit Magnesiumzugabe aufgeteilt.

Heart Substitutes: Mechanical and Transplant.

Four major fields of endeavor in cardiac surgery are included in this book. These are (1) prosthetic heart valves; (2) extracorporeal circulation; (3) mechanical heart; and (4) heart transplantation. While not meant to be a compendium of knowledge pertain- ing to prosthetic cardiac devices, it, nevertheless, discusses many topics, reveals many of the complexities of such devices, and acquaints the reader with the difficulties involving design, engineering, and the use of prosthetic cardiac devices. The problems surrounding cardiac transplantation are also fully discussed. Specific topics covered are 24 in number and include such pertinent areas as: the problem of thrombosis in artificial cardiac valves (chapt 3); methodology of cardiopulmonary bypass (chapt 7); artificial hearts: available types (chapt 13); and laboratory experience with heart transplantation (chapt 24). The individual topics are generally well-written, concise, and informative and comprise a resume of the experimental works of the individual authors and their colleagues.

The Prevention of Thrombosis in Artificial Cardiac Valves

The Prevention of Thrombosis in Artificial Cardiac Valves

Staphylococcal infection of a Starr-Edwards prosthesis, with fatal obstruction of the mitral valve.

IN recent years there has been increasing use of artificial cardiac valves such as the ball valve described by Starr and Edwards¶ in 1961. This report describes a patient with a Starr—Edwards prosthesis who died from occlusion of the mitral valve by thrombus and bacterial vegetations eleven months after operation. Case Report A 46-year-old woman was admitted to the Johns Hopkins Hospital for evaluation of fever on July 15, 1963. Twenty-three years previously mitral stenosis had been diagnosed, and in 1956 valvulotomy was performed. Five years later cardiac failure recurred, and atrial fibrillation developed. A markedly stenotic mitral valve was . . .