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Biomedical subjects

K B James

Publications and source records attributed to K B James.

29 records · Page 2Linked to original sources
PubMed1994

Prognosis of patients with left ventricular dysfunction, with and without viable myocardium after myocardial infarction. Relative efficacy of medical therapy and revascularization.

BACKGROUND: The uptake of F-18 deoxyglucose into dysfunction segments after myocardial infarction identifies metabolically active (FDG+) or inactive (FDG-) myocardium. Although patients with FDG+ segments have been found to be at risk for adverse events, the prognostic significance of viable myocardium in relation to other influences on postinfarction prognosis, including revascularization, remain ill defined. The purpose of this study was to investigate the relative prognostic significance of FDG+ tissue and to establish whether myocardial revascularization in patients with viable tissue attenuates the risk of adverse outcome. METHODS AND RESULTS: One hundred thirty-seven patients with left ventricular dysfunction and resting perfusion defects after myocardial infarction underwent positron emission tomography with both dipyridamole stress Rb-82 perfusion imaging and FDG imaging. After the exclusion of 4 patients proceeding to transplantation, 2 with uninterpretable scans and 2 lost to follow-up, 129 patients were followed clinically for 17 +/- 9 months. Four groups were defined: patients with FDG+ dysfunctional myocardium who were revascularized (n = 49) or treated medically (n = 21) and those with FDG- segments who were revascularized (n = 19) or treated medically (n = 40). The groups of patients with FDG+ or FDG- findings, with and without revascularization, did not differ with respect to known determinants of postinfarction prognosis: age, left ventricular ejection fraction, or the prevalence of multivessel disease. Nonfatal ischemic events occurred in 48% of medically treated FDG+ patients compared with 8% of revascularized patients with FDG+ tissue (P < .001) and 5% of patients with FDG- myocardium (P < .001). Thirteen patients died from cardiac causes; 11 (85%) had a left ventricular ejection fraction of < 30%, and these patients were evenly distributed between FDG+ and FDG- groups. Using Cox's proportional hazards model, only the presence of FDG+ myocardium (odds ratio, 12.9; P < .001) and the absence of revascularization (odds ratio, 5.8; P = .002) independently predicted ischemic events, while only age (P = .02) and ejection fraction (P < .001) but not the presence of viable myocardium were predictive of death. CONCLUSIONS: Residual viable myocardium after myocardial infarction may act as an unstable substrate for further events unless it is revascularized. Despite this association, age and left ventricular dysfunction remained the strongest predictors of cardiac death after myocardial infarction in these patients with a spectrum of left ventricular dysfunction.

Aged↗
PubMed1994

Implantable left ventricular assist device. Approaching an alternative for end-stage heart failure. Implantable LVAD Study Group.

BACKGROUND: The implantable left ventricular assist device (LVAD) was designed to provide circulatory support as an alternative to heart transplantation or to continued medical therapy of end-stage heart failure. Initial experience with the implantable LVAD used as a bridge to heart transplantation provides a clinical opportunity to study the function of the device and adaptation by the patient. METHODS AND RESULTS: Nineteen heart transplant candidates (mean age, 50 years; 17 males) underwent insertion of the HeartMate LVAD as a bridge to heart transplantation from December 1991 to November 1993. All patients were in cardiogenic shock on inotropes, and 16 (84%) were on an intra-aortic balloon pump. Three patients died because of multiple organ failure; all had right ventricular (RV) dysfunction (2 required RV assist devices). Sixteen patients (84%) improved markedly and were rehabilitated to New York Heart Association functional class I-II. Three patients are still on support. Significant improvements in hemodynamic function (based on analysis of the percent change from pre-LVAD condition to pretransplantation) were observed: cardiac index rose from 1.6 +/- 0.2 to 3.2 +/- 0.9 L/min per m2 (P = .0002), left atrial pressure fell from 22.9 +/- 9.5 to 8.0 +/- 5.5 mm Hg (P = .003), RV ejection fraction increased from 19.8 +/- 11.3% to 40.8 +/- 8.9% (P = .0004), pulmonary vascular resistance decreased from 5.2 +/- 2.6 to 2.0 +/- 0.8 Wood units (P = .004). Thirteen patients had successful transplants after a mean duration of 66 days on the LVAD (range, 22 to 101 days). There were no thromboembolic events while the patients were on the LVAD. Only aspirin with dipyridamole was given for anticoagulation during a total of > 1100 patient days of support. CONCLUSIONS: Bridge to transplant implantable LVAD experience indicates that hemodynamic improvement should be significant after insertion of the devices and that the risk of thromboembolic events with the HeartMate LVAD should be extremely low. Rehabilitation and quality of life should be markedly improved. Limitations of extrapolating this clinical experience to the permanent implantable LVAD include that these patients were hospitalized (permanent implants will be outpatients); the "vented-electric" HeartMate LVAD was not tested (it is a portable, battery-powered device), and true "chronic" LVAD support (> 1 year) was not tested, so questions regarding long-term device reliability and the chronic risk of infection are unknown.

Equipment Design↗
PubMed1991

Contribution of peripheral afferents to the activation of the soleus muscle during walking in humans.

Small, rapid stretches were applied to the soleus muscle during the stance phase of walking by lifting the forefoot with a pneumatic device. Stretch responses were induced in the soleus muscle by the disturbance. The amplitude and time course of the responses from the soleus muscle were a function of both the kinematics of the disturbance and the time in the step cycle when the disturbance was applied. The step cycle was divided into 16 equal time parts, and data obtained within each of these parts were averaged together. The electromyographic (EMG) response of the soleus muscle showed a time course that was similar to the time course of the angular velocity induced by the disturbance at the ankle. Three linear equations were used to predict the EMG response from the soleus muscle as a function of the angular kinematics of the disturbance: 1) velocity, 2) velocity and displacement, 3) velocity, displacement and acceleration. Introduction of a pure delay between the EMG and the kinematics substantially improved the predictions. Most of the variance (70%) in the EMG response could be accounted for by the velocity of the disturbance alone with an optimal delay (average 38 ms). Inclusion of a displacement term significantly increased the variance accounted for (85%), but further addition of an acceleration term did not. Since the velocity of the disturbance accounted for most of the variance, the reflex gain was estimated from the velocity coefficient. This coefficient increased in a ramp-like fashion through the early part of the stance phase, qualitatively similar to the increase in the H-reflex.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1991

Quadricuspid aortic valve. Case report and review of the literature.

Quadricuspid aortic valve is a rare congenital anomaly that may be found unexpectedly at surgery or diagnosed preoperatively by means of echocardiography or aortography. The most common hemodynamic abnormality associated with this anomaly is aortic insufficiency. We describe a representative case involving a 62-year-old man with severe aortic insufficiency and mild aortic stenosis. At operation, the aortic valve was found to have 4 cusps. The valve was replaced with a mechanical prosthesis. The patient was released 7 days after operation and was clinically well at 6-month follow-up.

Journal Article↗
PubMed1990

Electrocardiographic criteria for anterior myocardial infarction.

In a two-stage review, electrocardiographic patterns associated with anterior infarction were determined in 135 patients whose diagnoses were established by contrast ventriculography. The five most common findings were tested in 1,324 consecutive patients to assess sensitivity, specificity, and predictive accuracies for anterior myocardial infarction. The criteria were shown to have high positive predictive accuracy and specificity levels, and confirmed the value of the standard 12-lead electrocardiogram for detecting anterior myocardial injury.

Electrocardiography↗
PubMed1989

Myocarditis as cause of impaired myocardial function after aortocoronary bypass.

A 44-year-old man suffered congestive heart failure and worsened ejection fraction 8 months following repeat aortocoronary bypass surgery. Recatheterization showed patent grafts. A constellation of symptoms, together with highly suggestive (but not in themselves diagnostic) endomyocardial biopsy results, led us to an unexpected diagnosis of active lymphocytic myocarditis. After treatment with prednisone and azathioprine, the patient improved clinically and his left ventricular ejection fraction increased from 18% to 24%.

Journal Article↗
PubMed1989

Heart disease arising during or secondary to pregnancy.

When cardiovascular disease in women is considered, the cardiovascular physiology and diseases related to pregnancy are clearly unique, particularly to young women. Toxemia and its associated hypertension are the major cardiovascular disorders arising during and secondary to pregnancy and may well increase in prevalence as women undertake childbearing at older ages. Although its pathophysiology is unknown and its outcome may be grave to both mother and child, toxemia is preventable, treatable, and curable. This is unlike the three other forms of heart disease occurring in pregnancy discussed here. Aortic dissection, pulmonary hypertension, and peripartum cardiomyopathy are not preventable and are unpredictable, difficult to treat, and incurable. These latter disorders carry on indefinitely for the duration of the patient's life and seriously limit future options, including those for more pregnancies. Among the disorders of the heart in pregnancy, toxemia and peripartum cardiomyopathy are the subjects of especially active investigation at present. Major advances in understanding these disorders could minimize cardiovascular risk to the pregnant woman.

Aortic Aneurysm↗
PubMed1988

Rehabilitation of musicians with upper limb amputations.

Three saxophone players with upper limb amputations have been successfully rehabilitated to play their musical instruments using skin-conductivity touch control. Each attained a standard of musicianship sufficient to perform the standard repertoire of the instrument in a concert setting. The mechanical and electrical modifications to the saxophone are described, as well as the principles of operation of the skin-conductivity touch control module. The touch control module is commercially available for prosthetists who wish to fit musicians or others with upper extremity amputations who require rapid accurate control of a number of channels of powered prosthetic function.

Amputation, Surgical↗
PubMed1986

Improved ankle-foot system for above-knee amputees.

Above-knee amputees were studied while wearing a prosthesis containing either a standard or a modified single axis foot. The modified foot allowed 12-15 degrees of dorsiflexion and reduced stiffness in the area of the metatarsal-phalangeal (MTP) joint. The amputees were allowed to vary the stiffness at the two joints to obtain what "felt best." The amputees agreed that in comparison to the standard single-axis foot, the modified foot: a) offered a more comfortable gait while walking on level ground; b) made walking up inclines easier; c) affected knee stability while walking on declines; and d) made foot placement on stairs and ladders more critical due to potential knee instability. As well as qualitative reactions, changes in the gait cycle were measured quantitatively for different speeds and inclinations of walking on a treadmill. Measurements from normal subjects matched by age and sex were used for control purposes. All participants wore soft-soled shoes. The amputees selected a stiffness that allowed a degree of dorsiflexion which precisely matched on average that of the normal subjects. In contrast, they selected a stiffness at the MTP joint which allowed very little flexion of the toes. Significant changes also occurred in the pattern of hip movements, so that they became much more symmetrical on the two sides, although substantial differences remained between the hip movements of the amputees and the normal subjects. If modifications in the ankle joint can be coupled with improvements in the knee joint to prevent potential instability, a much improved gait should be possible for above-knee amputees.

Adult↗