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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↗
PubMed1988

Surgical considerations for avoiding disc interference based on a ten-year experience with the Medtronic Hall heart valve.

All low profile valves are susceptible to problems related to implant technique, especially immobilization of the occluder. Because the disc-valve-ring clearance may be only a fraction of a millimeter, this complication is a small yet ever present possibility of which the surgeon must be aware. Special care must be taken when implanting low profile valves to eliminate the possibility of disc interference caused by suture ends or intracardiac structures. The surgeon can minimize the risk of disc immobilization by careful attention to precautionary surgical measures described herein.

Aortic Valve↗
PubMed1988

Risk factors in surgically treated mitral valve disease.

Risk factors for operative mortality and long term survival were identified in 144 patients undergoing mitral valve replacement (MVR). The 3-year survival was 77% at a median follow-up time of 3.01 years, including an early mortality of 7.6%. Nineteen preoperative and perioperative variables were analysed by univariate and multivariate methods. The sole risk factor independently predictive of postoperative death was a poor functional class with a relative risk (RR) of 3.17 compared to patients with a better functional class. Independent risk factors of long term survival were; prior heart operation, presence of mitral regurgitation, age at operation and poor functional class. Estimation of the parameters of the Cox's model gave a predicted 3-year survival ranging from 95% to 11% for the most favourable and the less favourable risk factor combinations. Risk factors that affected late death were the presence of ischemic coronary etiology and poor functional class. Two modes of late death were identified each with its prognostic factor. The most common mode was cardiac-related death, its sole risk factor was the presence of ischemic coronary etiology. The RR ratio was 3.2 for patients with ischemic coronary etiology, compared to patients with other etiologies. Sudden cardiac death was the next, its independent risk factor was the age at operation with increasing hazard for younger patients. The RR ratio was 8.55 for a 35-year-old patient compared to a 60-year-old patient.

Age Factors↗
PubMed1988

Risk factors in surgically treated aortic and mitral valve disease.

Risk factors in simultaneous aortic and mitral valve replacement were studied in 78 patients. Risk factors for early mortality, according to a stepwise logistic regression model, were male sex, concomitant heart surgery and prior valve replacement. For low-output syndrome, the major morbid event, the risk factors were endocarditic etiology, concomitant heart surgery and prior valve replacement. Survival curves were used to estimate univariate risk factors for total mortality. With a multivariate procedure, using the Cox regression model, two covariates were pin-pointed as independent prognostic factors in total mortality, viz. mitral regurgitation and concomitant heart surgery. The Cox model also showed the two covariates ischemic heart disease and endocarditic etiology to be risk factors in late mortality. Predicted 3-year survival was estimated with different combinations of these risk factors. The results were compared with earlier reports.

Aged↗
PubMed1988

Risk factors of morbidity and mortality in surgically treated chronic aortic valvular heart disease.

A cohort of 617 patients underwent aortic valve replacement (AVR) the median follow-up time was 3.4 years with a range (0-7.8) years. The incidence of early mortality was 5.0% and the five years survival (77.9 +/- 1.9)%. Risk factors of early mortality and morbidity (Low Output Syndrome) occurring the first 31 days after operation were pinpointed. Another analysis was done to estimate independent predictors of late premature death from all causes, and from specific causes (cardiac related, sudden cardiac). One of the major late morbid events was the appearance of systemic emboli. Its rate was 1.4% pats. Year. Its risk factors were presence of pure aortic regurgitation and advanced age at operation. The relative survival rate was at 5 years of 87.0% for the total cohort, but for our younger patients (age less than 30 years), we reached 99.4%. Our results suggest more aggressive measures to correct the hazard in AVR, and impose carefulness in comparing quality of AVR from different institutions for mortality and morbidity. Finally the results of AVR are rather palliative than curative except for our younger patients where we reached curability.

Adult↗
PubMed1988

Morbidity in valvular heart replacement: risk factors of systemic emboli and thrombotic obstruction.

A study on a cohort of 839 patients with valvular heart replacement between June 1977 and May 1985 showed that the linearized rates of systemic emboli and thrombotic obstruction were 1.4/100 pts/year for Aortic Valve Replacement (AVR), 2.2/100 pts./year for Mitral Valve Replacement, and 3.00/100 pts./year for Double Valve Replacement (DVR). The 5-year free-from-thromboembolism (TE) survival was 95% for AVR and 92% for MVR. The hazard function (the instantaneous risk) for TE peaked in the first six months after operation for AVR and MVR. Another analysis using the Cox regression model to estimate risk factors of systemic emboli and thrombotic obstruction pinpointed two factors in the AVR group: presence of aortic regurgitation (AR) and age at operation. In the MVR group the sole predictor covariate was sex of the patients, with a higher hazard for females. Our results underline the importance of patient-related factors besides the type of prosthesis as predictors of morbidity from TE.

Age Factors↗
PubMed1987

Burns: epidemiology and the effect of a prevention programme.

Epidemiological data concerning 1391 patients hospitalized at the Burns Unit, Odense University Hospital during a 17-year period are presented. The annual incidence showed a steady downward trend of 3 per cent per year. Scald and fire were the most important causes of burn injuries. Among children a significant reduction in burns due to scalds and electrical or corrosive injuries was noted. The rate of injury among adults and the elderly was constant. These results might reflect an intensive information campaign in the media, revisions of laws and regulations and improvements in the safety of household products, especially directed towards thermal injuries among smaller children.

Adolescent↗
PubMed1986

Continuous monitoring of cardiac output postoperatively using an implantable Doppler probe.

The authors evolved a Doppler probe which can be attached to the ascending aorta intraoperatively. Using a pulsed echo Doppler flowmeter operating at 2 mHz, cardiac output was continuously measured during the first 2 days after open-heart surgery in 20 patients. The internal diameter of the aorta was assessed with ultrasound echo technique. The probe was fixed to the ascending aorta with a double suture through the adventitia. The suture was tightened by means of a long tourniquet which was passed through an infraxiphoid skin incision, between the two chest drains. A stable position providing adequate signals was achieved by use of probes with stabilizing "side flaps". In 8 cases the method was compared with the thermodilution technique using Swan-Ganz catheters. Analysis of 44 simultaneously performed measurements revealed a highly significant correlation between the two methods, and the results remained comparable throughout the 48-hour test period. There were no complications and all the probes could be easily removed.

Cardiac Output↗
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↗