Search PubMed⌕ Search

Biomedical subjects

K V Hall

Publications and source records attributed to K V Hall.

At least 19 recordsLinked to original sources
PubMed1992

The Medtronic-Hall valve: a design in 1977 to improve the results of valve replacement.

The prototype Medtronic-Hall valve was developed from improvements to the Lillehei-Kaster and Björk-Shiley valves. The housing was constructed of a single piece of titanium and the disc was composed of pyrolytic carbon; both materials had shown no structural breakdown in previous clinical use. The valve was tested with pulse simulator and electromagnetic flow meter studies and yielded a high effective orifice area. Results in 110 patients were significantly better with the Medtronic-Hall valve than with either of the previous valves. In the 21-mm aortic valve the peak-peak gradient was 12 mmHg; it was 9.2 mmHg in the 23-mm, 3.8 mmHg in the 25-mm, and 2.5 mmHg in the 27-mm. Studies found 5% of forward flow regurgitation in the aortic position and more than desired regurgitation through the mitral valve. After the opening angle of the mitral valve was reduced to 70 degrees, regurgitation reached an acceptable level and the improved hemodynamics resulted in lower transvalvular gradients than in previous mechanical valves. Some patients are naturally more prone to thromboembolism regardless of valve type or anticoagulant therapy; thus the human factor plays a large role in a valve's success. More randomized studies are needed for accurate valve comparison, in addition to investigations of sewing ring factors. Nevertheless, the Medtronic-Hall valve has been used successfully for 15 years and has exhibited no housing fractures.

Actuarial Analysis↗
PubMed1979

Clinical and hemodynamic results after combined aortic and mitral valve replacement with the Lillehei-Kaster pivoting disc valve.

Combined mitral and aortic valve replacement with the Lillehei-Kaster pivoting disc valve prosthesis was performed in 23 patients. Hospital mortality rate was 8.3 per cent. Detailed postoperative clinical and hemodynamic studies were performed after a mean follow-up period of 24.4 months. Replacement of both valves had resulted in a marked symptomatic and hemodynamic improvement with a normal or nearly normal resting value of cardiac output, pulmonary arterial pressure, and pulmonary vascular resistance while left ventricular end-diastolic pressure (LVEDP) had increased significantly. The rise in left ventricular end-diastolic pressure most probably might be related to the simultaneous rise in cardiac output (Starling mechanism), reflecting the severity and irreversibility of the underlying myocardial disease. Most patients also had systolic gradient across the aortic prosthesis, as well as diastolic gradient across the mitral prosthesis. The gradients across the mitral prosthesis were approximately the same as seen after single valve replacement, while the pressure gradients across the aortic prosthesis were somewhat smaller than previously reported. Angiographic studies of the aortic valve movement indicated that the opening angle of the disc was approximately 60 degrees, and thus less than according to the valve specifications.

Adult↗
PubMed1979

Primary results with the new Hall-Kaster disc valve prosthesis in mitral position.

The Hall-Kaster central flow prosthetic heart valve was introduced in 1977 in an attempt to improve the hemodynamics of the disc valve prostheses. Towards this accomplishment, innovations in the tilting axis, the disc guidance mechanisms, and disc translational freedom cooperate to improve flow through both orifice segments of the open valve. The present study reports on the primary clinical and hemodynamic findings in the first 20 patients (mean age 57.6 years) with isolated mitral valvular disease, examined 3--4 months after insertion of the Hall-Kaster disc valve prosthesis. The hemodynamic findings displayed low gradients and high calculated valve areas (5). At rest, the mean diastolic pressure gradient across the smallest prosthesis used (O.D. 27) averaged 3.0 mmHg, vs. 2.6 mmHg across the largest valve sizes (O.D. 29--31). Calculated valve area was on an average 3.08 cm2 for the smaller valve, and 3.47 cm2 for the larger valves, which corresponded to an utilization of 81% and 77% of the orifice area measured in vitro. A comparison with earlier studies of mean diastolic mitral gradients with different mitral prostheses indicates that the Hall-Kaster disc valve represents an improvement towards a hemodynamically more efficient prosthesis for mitral valve replacement.

Aged↗
PubMed1979

Intraoperative and postoperative hemodynamic studies in patients undergoing aortic valve replacement with the Hall-Kaster cardiac disc valve prosthesis.

Intraoperative and postoperative hemodynamic measurements in the first patients to receive the Hall-Kaster cardiac disc valve prosthesis in the aortic position demonstrated the principal hemodynamic pattern of this new mechanical valve. These hemodynamic studies demonstrated favourable transvalvular gradient values and a degree of flow area utilization of the valve orifice which was close to its theoretical maximum. The Hall-Kaster prosthesis thus presented improved flow characteristics in patients undergoing aortic valve replacement, which is considered of particular importance to the patients with a narrow aortic root.

Adult↗
PubMed1979

Primary clinical experience with the Hall-Kaster valve in the aortic position: results at 3 months including hemodynamic studies.

The Hall-Kaster pivotal disc prosthetic heart valve was introduced in 1977. The primary goal of the design was to obtain the least possible obstruction to flow. Toward this end, innovations in the tilting axis, disc guidance mechanisms, and disc translational freedom combine to improve flow through both orifice segments of the open valve. The present study reports the primary clinical and hemodynamic findings in 28 patients (mean age, 53.8 years) with aortic valve disease, examined 3 months after insertion of the Hall-Kaster pivotal disc valve. The hemodynamics findings displayed low gradients and high calculated orifice areas. Satisfactory flow was observed through both the major and minor openings of the prosthesis. There were no arterial thromboembolic episodes. The increase in serum lactate dehydrogenase activity was moderate, indicating a slight-to-moderate intravascular haemolysis.

Adolescent↗
PubMed1979

Mitral insufficiency following myocardial infarction.

Severe mitral insufficiency following myocardial infarction in 15 patients is reported. The mean interval from infarction to surgery was 2.8 years. All patients were operated on with mitral valve replacement and in 14 aortocoronary bypass and/or resection of left ventricular aneurysm was necessary as well. Rupture of one or more heads of the papillary muscle was found in 5 patients. In another 5 the papillary muscles were discoloured, fibrosed and shortened, and in the last 5 patients the mitral incompetence was caused by a marked dilatation of the atrioventricular ring. Five patients (33%) died, 3 early and 2 late after surgery. All the patients who died had a markedly imparied left ventricular function pre-operatively with end-diastolic pressures from 15 to 26 mmHg.

Coronary Artery Bypass↗
PubMed1978

Aorto-coronary saphenous vein bypass graft. Peroperative flow studies related to late graft patency.

In aorto-coronary saphenous bypass grafts, peroperative flows measured by electromagnetic flowmetry were studied at rest and after injection of papaverine to reduce vasomotor tone. The results were correlated to graft patency approximately 14 months after operation and showed that patent grafts had greater flow values, both at rest and after papaverine, than grafts which were occluded at the re-examination. There was, however, considerable overlapping between the two groups, and no clear distinction between flow values in successful and unsuccessful grafts either at rest or after papaverine was found. No correlations were demonstrated between peroperative graft flow on one hand and the presence or absence of ventricular dyskinesia or electrocardiographic evidence of previous transmural myocardial infarction on the other.

Adult↗
PubMed1978

Influence of aorto-coronary saphenous vein bypass surgery on left ventricular function. Comparison before and one year after surgery in 80 patients.

To assess the haemodynamic effects of aorto-coronary saphenous vein bypass grafting, pre- and post-angiographic left ventricular end-diastolic pressure (LVEDP) and ejection fraction (EF) were measured before and in average 14 months after surgery in 80 patients. Symptomatic improvement occurred in 91% (73 of 80). In 43 patients with patent graft(s), pre-angiographic LVEDP and EF were unchanged (p always greater than 0.05), while postangiographic LVEDP was significantly reduced. Unchanged pre- and postangiographic LVEDP and EF were observed in 28 patients with double or triple grafts, with at least one graft patent and the other(s) occluded. Unchanged pre- and postangiographic LVEDP and reduced EF were observed in 9 patients with occluded single, double or triple grafts. We conclude that successful aorto-coronary saphenous vein bypass surgery in general does not improve resting left ventricular performance, but that the beneficial effect on left ventricular function can be demonstrated after a stress test such as ventriculography. A single graft to the left anterior descending artery seems to be of particular importance in this connection. On the other hand, deterioration was evident after unsuccessful surgery, particularly in patients with occlusions of 2 or 3 grafts. Digitalis therapy after operation or electrocardiographic indices of postoperative myocardial infarction apparently did not influence left ventricular performance.

Adult↗
PubMed1977

[Expensive surgery].

Explore the source record for details and available documents.

Cardiac Surgical Procedures↗
PubMed1977

Clinical and haemodynamic results following mitral valve replacement with the new Lillehei-Kaster pivoting disc valve prosthesis.

Thirty-four patients were re-examined 12-24 months after mitral valve replacement with the Lillehei-Kaster pivoting disc valve prosthesis. There was an improvement of the kinetics with a significant decrease in arteriovenous oxygen difference compared with oxygen consumption. Cardiac output and stroke volume remained abnormally low, not differing significantly from pre-operative values. Resting pulmonary wedge pressure, pulmonary arterial pressure and pulmonary vascular resistance decreased significantly after operation. Mean values for these parameters remained slightly above normal. Exercise produced a rise in pulmonary wedge pressure, which could be explained partly by a simultaneous deterioration of the left ventricular function, as indicated by high end-diastolic pressures, and partly by a degree of obstruction to the foreward flow at the mitral valve itself. The rise in pulmonary wedge pressures led in turn to increased pulmonary arterial pressure, the latter being aggravated in some patients by a rise in pulmonary vascular resistance. Cardiac output increased during exercise, but usually to a lesser extent than was anticipated from the increase in oxygen consumption. The changes in cardiac output during exercise were due to an increase in heart rate, while stroke volume remained unchanged. The mean diastolic pressure difference across the prosthesis was 8.6 mmHg at rest and 12.7 mmHg during exercise. Subjective improvement and reduction in heart volume, as noted in the present series, corroborated the benificial effect of the operative procedure. The valve were all competent, as judged by cinéangiography, except in a few patients, in whom a small valvular or paravalvular leakage was seen. No thrombo-embolic episodes were recorded during the follow-up period.

Adult↗