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Biomedical subjects

M Rubenfire

Publications and source records attributed to M Rubenfire.

At least 73 records · Page 4Linked to original sources
PubMed1986

Intraaortic balloon pumping 1967 through 1982: analysis of complications in 733 patients.

Between June 1967 and December 1982, 872 attempts at intraaortic balloon pumping (IABP) were made in 733 patients. Nearly 75% of the patients were men; the proportion of women has increased in recent years. The principal indication for IABP support initially was cardiogenic shock, but over the years, preoperative support, weaning from cardiopulmonary bypass and unstable angina have become the primary indications. Complications of IABP were classified and distributed by severity (minor: I [15%] and II [26%]; major: III [3%] and IV [1%]) and type ([vascular [22%], infectious [22%], and bleeding [7%]). Vascular complication rates were higher in women (32 vs 18%; p = 0.0001), in diabetic patients (32 vs 20%, p = 0.003), and in hypertensive patients (27 vs 20%, p = 0.02). These did not vary with the duration of IABP support (range of duration 0 to 76 days). The rate of infectious complications was related to location where IABP was performed (coronary care unit 26%, operating room 12%). The rate of fever and bacteremia increased significantly with duration of IABP support, but the rate of local wound infection did not. In conclusion, most IABP complications are minor, resolve after balloon removal, are related to vascular status of the patient and, with the exception of bacteremia, are independent of IABP duration.

Adolescent↗
PubMed1986

Platelet hyperaggregability in patients with chest pain and angiographically normal coronary arteries.

Forty-one patients with chest pain and angiographically normal coronary arteries were studied for platelet abnormalities. Patients with conditions known or suspected to be associated with chest pain or platelet dysfunction were excluded. After coronary angiography and 2-week withdrawal from all medications, platelet aggregometry was performed using peripheral venous plasma samples and 3 concentrations of adenosine diphosphate, 2.34, 1.17 and 0.58 microM, and epinephrine, 11, 1.1 and 0.55 microM, as stimuli. Platelet morphology in response to surface contact (adhesion) was evaluated by transmission electron microscopy to determine the percentage of platelets in the round/abortive (inactive), dendritic (intermediate) and spread (activated) forms. Plasma specimens obtained from healthy volunteers of similar age and sex were analyzed in parallel and served as control subjects. Compared with control subjects, patients had increased aggregation at all concentrations of both adenosine diphosphate and epinephrine (p less than 0.001). Patients also had fewer platelets in the dendritic form and more in the round/abortive and spread forms. Thus, patients with chest pain and normal coronary arteries have platelet hyperaggregability in vitro, although the clinical relevance of this finding is unclear.

Adenosine Diphosphate↗
PubMed1986

Concealed ventricular premature complexes in a population sample.

One hundred fifty patients were analyzed with a random sample of patients whose Holter recordings indicated ventricular premature complexes (VPCs). Thirty-five patients (23%) had more than 30 VPCs/hour. Of these 35 patients, 19 had concealed VPCs. This represents 54% of the patients with more than 30 VPCs/hour and 13% of the total sample of 150 patients with VPCs. The most common type of concealed VPCs was the classic concealed bigeminy (S = 2n - 1), which was found in 10 of 19 patients (52%) whose electrocardiograms and patterns were characteristic of concealed VPCs. This was followed by the "even variant" 2n in 5 patients (26%), concealed trigeminy (S = 3n - 1) in 1 (5%), the 3n - 2 variant in 1 (5%) and the "interpolated variant" of 1 + (2n - 1) in 1 (5%). One patient showed a conversion from 2n - 1 to 2n.

Adult↗
PubMed1986

Relation of serum reverse T3 to amiodarone antiarrhythmic efficacy and toxicity.

The relation of serum reverse T3 (rT3) to amiodarone efficacy and toxicity was studied in 31 patients with frequent and complex ventricular arrhythmias. Baseline studies included 48-hour Holter recordings and rT3 levels (normal 33 ng/dl or less). Amiodarone therapy was initiated with a 5 mg/kg infusion followed by 600 to 800 mg/day for 7 to 10 days, then 200 to 400 mg/day. Holters and rT3 levels were repeated every 1 to 3 months and amiodarone was titrated to achieve at least a 70% reduction in total ventricular premature complexes, at least a 90% reduction in couplets and abolition of ventricular tachycardia. The baseline rT3 level was 18 +/- 7 ng/dl (range 10 to 30) and patients were followed 12 +/- 9 months. Arrhythmia control was achieved in 25 patients (81%), including 21 patients with elevated rT3 levels (36 to 105 ng/dl) and 4 patients with normal rT3 (15 to 33 ng/dl). Six patients were uncontrolled with rT3 (27 to 90 ng/dl) and 14 patients had minor side effects with rT3 (27 to 123 ng/dl). Three of 4 patients in whom rT3 levels exceeded 130 ng/dl died suddenly (137 to 174 ng/dl before the event). Thus, amiodarone efficacy and minor toxicity occurs at rT3 levels less than 105 ng/dl and sudden death may be associated with levels greater than 130 ng/dl.

Aged↗
PubMed1986

Intravenous lorcainide versus lidocaine in the treatment of frequent and complex ventricular arrhythmias.

Thirty patients with frequent (greater than or equal to 30/hr) and repetitive ventricular premature beats (VPBs) unassociated with acute infarction were randomized to intravenous lorcainide (LOR) or lidocaine (LID). Following at least 2 hours of baseline Holter monitoring, patients received LOR, 2 mg/kg then 200 mg/24hr, or LID, 1 mg/kg then 2 mg/min, with rebolus if needed. Nonresponders detected by bedside telemetry were crossed over. Clinical response was 6 of 25 (24%) including two of nine crossovers with LOR and 8 of 26 (31%) including 3 of 12 crossovers with LID (p = NS). By computer analysis of 24-hour Holter monitors and asymptotic regression of success rates at hourly intervals, it was projected that greater than or equal to 80% reduction in VPBs occurred in 28% of LOR and in 25% of LID (p = NS), and complete suppression of repetitive VPBs occurred in 102% of LOR and in 92% of LID (p = NS). The mean drug levels were 405 ng/ml (range 371 to 463) with LOR and 3.4 micrograms/ml (range 2.1 to 3.6) with LID. Side effects were similar, occurring in 8 of 25 LOR trials and in 11 of 26 LID trials (p = NS). Thus, LOR and LID effectively suppress repetitive VPBs and to a lesser extent VPB frequency. However, neither drug is superior and each may be an effective alternative when resistance to the other is encountered.

Aged↗
PubMed1986

Arrhythmia control and other factors related to sudden death in coronary disease patients at intermediate risk.

Thirty-three patients with coronary artery disease and frequent, complex ventricular arrhythmias (VA) were followed long-term to evaluate factors related to sudden death (SD). Patients with malignant VA (sustained ventricular tachycardia (VT), resuscitated SD, or acute myocardial infarction) were excluded. Baseline data included angiographic ejection fraction (EF), segmental wall motion, and Holter evidence of frequent (greater than 30/hr) and complex (repetitive) ventricular premature beats (VPBs). Control of VA was attempted with conventional or experimental agents and was defined as greater than or equal to 70% reduction in VPBs, greater than or equal to 90% reduction in couplets, and abolition of nonsustained VT on two consecutive Holter tapes. After 24 +/- 15 months of follow-up on the single most effective agent, 18 patients survived while 15 patients died suddenly. There was no difference between these groups with respect to age, sex, or baseline VA. Survivors had a higher EF (51% vs 34%, p less than 0.001), fewer dyskinetic segments (0.05 vs 1.0, p less than 0.01), and better VA control (83% vs 40%, p less than 0.01) than nonsurvivors. By analysis of variance, VA control was not independent of EF (F = 6.98, p less than 0.01). The 1-, 2-, and 3-year survival rates were 90%, 90%, and 82% for patients with EF greater than or equal to 40% and 22%, 11%, and 11%, for those with EF less than 40% and uncontrolled VA.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1986

Validity of skinfold thickness measures of formerly obese adults.

UNLABELLED: To assess the validity of skinfold thickness estimates of body fatness in formerly morbid obese adults, 23 patients (17 women, 6 men) who had completed a protein-sparing modified fast were studied. Mean +/- SD weight loss was 60.7 +/- 20.6 kg for men and 42.6 +/- 11.5 kg for women. Body density and percent body fatness were determined after weight loss according to four commonly used skinfold equations: Pollock (P); Durnin-Rahaman (D-R); Durnin-Womersley (D-W); and, Jackson-Pollock (J-P). The validity of these measurements was assessed by hydrostatic weighing, which revealed a percent body fatness of 20.4 +/- 6.5 for men and 29.8 +/- 8.4 for women. The mean difference and total error (square root of the mean of squared deviations) between skinfold predicted and hydrostatically-determined percent body fatness for each skinfold equation were: P, 2.0 and 4.9; D-R, 4.2 and 6.6; D-W, 7.1 and 8.4; and, J-P, 0.7 and 4.4. With the exception of the latter equation, all significantly overestimated (p less than 0.01) hydrostatically-determined percent body fatness. CONCLUSION: Select skinfold equations may result in a marked overestimation of body fatness in formerly obese patients.

Adipose Tissue↗
PubMed1986

The effect of verapamil on antipyrine pharmacokinetics and metabolism in man.

The effect of verapamil pre-treatment on the pharmacokinetics and metabolism of antipyrine was studied in eight healthy male volunteers. The oral clearance of antipyrine was decreased from 2.18 to 1.95 l h-1 (P less than 0.01) by verapamil (80 mg three times daily for 2 days prior to antipyrine administration and 2 days following) while half-life was increased from 13.2 to 15.6 h (P less than 0.01). The urinary excretion of norantipyrine, 4-hydroxyantipyrine and 3-hydroxymethylantipyrine was decreased by 19.2%, 23.1% and 16.7% respectively (P less than 0.05) in the presence of verapamil. In addition, the rate constants for formation of each of these metabolites were significantly decreased by an average of approximately 30%. These results suggest that verapamil is capable of inhibiting oxidative metabolism, a finding which could be of clinical significance for drugs highly dependent upon pathways such as those inhibited in this study for elimination.

Adult↗
PubMed1985

Intravenous and oral loading versus oral loading alone with amiodarone for chronic refractory ventricular arrhythmias.

To determine whether combined intravenous (i.v.) and oral loading with amiodarone can shorten its onset of action, a comparative study was conducted. Twenty patients with refractory ventricular arrhythmias were treated with amiodarone. All patients had frequent (greater than or equal to 30/hour) and complex (repetitive) ventricular premature beats on a 48-hour baseline Holter recording. Ten patients (group A) received oral loading alone: 800 mg/day for 7 days, 600 mg/day for 3 days, then a maintenance dose 200 to 400 mg/day. Ten patients (group B) received i.v. and oral loading: 5 mg/kg i.v., and then the same regimen as for group A. Follow-up 24-hour Holter recordings were obtained daily for 7 days, weekly for 1 month, and then monthly. Arrhythmia control was defined as at least a 70% reduction in ventricular premature beats, a 90% or greater reduction in couplets and abolition of ventricular tachycardia. The time to optimal ventricular arrhythmia control was shorter for group B (20 +/- 18 vs 105 +/- 83 days, p less than 0.05) and the cumulative amiodarone dose at the time of control was smaller for group B (10 +/- 8 vs 48 +/- 39 g, p less than 0.05). No complications were encountered with i.v. amiodarone. Thus, initial loading with i.v. amiodarone can shorten the time to optimal ventricular arrhythmia control and lower the cumulative dose required.

Administration, Oral↗
PubMed1984

Physiological profile of national-class National Collegiate Athletic Association fencers.

Selected physiological characteristics of seven national-class fencers (1983 National Collegiate Athletic Association Division I champions) were studied and the results compared with those for normal persons and athletes of similar age. Evaluation included maximal oxygen uptake during arm and leg ergometry, serum lipids, body composition, and standard spirometry. Maximal oxygen uptake during arm work (34.2 mL X kg-1 X min-1) was 68% of that observed during leg work (50.2 mL X kg-1 X min-1). Mean serum triglyceride, total cholesterol, and high-density-lipoprotein cholesterol levels were 68.5, 187, and 54.5 mg/dL, respectively. Hydrostatically determined percent body fat averaged 12.2%. Results of pulmonary function studies were normal. The aerobic capacity of National Collegiate Athletic Association fencers is only slightly higher than active men of comparable age, and substantially lower than world-class endurance athletes. These data suggest that success in fencing may depend more on technique, speed, and agility as opposed to a high aerobic capacity and low percent body fatness.

Adult↗
PubMed1984

The systemic fibrinolytic effect of low-dose intraarterial streptokinase: observations in 12 patients. Work in progress.

The systemic hematological effects of low-dose intraarterial streptokinase were studied in 12 patients with angiographic evidence of thrombosis. Streptokinase was administered at 5,000 U/hr; this rate was increased in the absence of clinical response or a systemic effect, which was defined as a thrombin time greater than twice that of the control time and/or a fibrinogen concentration less than 30% that of the control concentration. Eight patients experienced a systemic effect with final infusion rates of 7,500 to 20,000 U/hr over 20 to 72 hours, while 4 patients had no evidence of a systemic effect at 5,000 to 10,000 U/hr over 18 to 138 hours. A systemic effect could not be predicted based on infusion rates or durations, and the presence of a systemic effect was not predictive of hemorrhagic complications or thrombolytic effect in our small series. These results suggest that a systemic effect is frequently encountered with this form of therapy and is of uncertain clinical relevance.

Adult↗
PubMed1984

Chronic adaptations to physical conditioning in cardiac patients. Implications regarding exercise trainability.

Physical conditioning in patients with coronary heart disease can result in increased functional capacity, symptomatic relief of angina pectoris, favorable reduction of risk factors, enhanced psychological status, and improved quality of life. The mechanisms underlying the adaptations to training are poorly understood, but it is clear that several factors affect exercise trainability. Guidelines are available that suggest the appropriate intensity, frequency, and duration of exercise needed to obtain beneficial physiologic adaptations.

Adaptation, Physiological↗
PubMed1984

Cardiac exercise programs: role of continuous electrocardiographic monitoring.

The purpose of the present study was to determine the value of telemetry monitoring for detection of new and significant electrocardiographic (ECG) or blood pressure abnormalities during outpatient cardiac exercise therapy. Following preliminary graded exercise testing, 177 cardiac patients underwent a four-week monitored exercise program three days per week. During 2248 training sessions, 12 of the 177 patients (7%) showed significant ECG or blood pressure abnormalities not evident on initial exercise testing, eight (5%) requiring change in medical therapy. Abnormalities included significant (greater than 2mm) ST-T displacement (two patients), ventricular arrhythmias (seven patients), and hypertensive exercise response (three patients). Eleven of the abnormalities (92%) appeared during the first three weeks of the program. Results indicated that continuous ECG and blood pressure monitoring offered a small but significant diagnostic yield not evident on preliminary graded exercise testing. One-year experience suggested that short-term (four weeks) exercise monitoring may be adequate for cardiac patients who undergo careful preliminary screening.

Adult↗
PubMed1983

The mechanism of dysrhythmias in variant angina pectoris: occlusive versus reperfusion.

Thirty-six patients with variant angina pectoris (VAP) were analyzed to investigate whether the mechanism underlying dysrhythmia is related to coronary occlusion or reperfusion. Fifteen of the 36 patients demonstrated dysrhythmias (42%). Twelve of 15 patients (80%) experienced dysrhythmia prior to the acme of ST-segment elevation (occlusive dysrhythmia), and those of tachyarrhythmia type were characterized by the presence of ventricular premature beats initially isolated, increasing in frequency, and preceding the more malignant forms of dysrhythmias, such as ventricular tachycardia or ventricular fibrillation. The occlusive dysrhythmias included ventricular dysrhythmia (ventricular premature beats, ventricular tachycardia, slow ventricular tachycardia, ventricular fibrillation) in eight patients and conduction abnormalities (second- and third-degree AV block, left posterior fascicular block) in four patients. Thirteen episodes of VAP were fully recorded electrocardiographically. The average time to onset of dysrhythmia, after the beginning of ST-segment elevation, was 4.94 minutes +/- 1.52. The duration of the episodes without dysrhythmia was 0.86 minute +/- 0.53. The "reperfusion dysrhythmia" occurred in three patients (20%) and was characterized by the appearance of isolated couplets of ventricular premature beats, ventricular tachycardia, or ventricular fibrillation without prodromal ectopic activity. The dysrhythmia occurred in one patient during the resolution of ST-segment elevation and in two patients within seconds of ST-segment normalization. We conclude that the occlusive related dysrhythmias are the most important mechanism in VAP. They are dependent on the duration of the ischemic episode.

Adult↗
PubMed1983

Hydralazine therapy in severe chronic heart failure: inability of radionuclide left ventricular ejection fraction measurement to predict the hemodynamic response.

Simultaneous hemodynamic and radionuclide angiographic assessment was made at rest and during exercise in nine patients with severe chronic congestive heart failure to determine the value of radionuclide left ventricular ejection fraction measurement in predicting the hemodynamic response to short-term treatment with oral hydralazine. Hydralazine, 50 to 100 mg orally every 6 hours, produced significant increases in cardiac index and stroke volume index at rest and during exercise (p less than 0.01) and in left ventricular stroke work index at rest (p less than 0.01) and during exercise (p less than 0.05), significant decreases in systemic vascular resistance at rest and during exercise (p less than 0.01) and significant increases in radionuclide angiographic left ventricular ejection fraction at rest (control 0.21 +/- 0.06 vs. hydralazine 0.26 +/- 0.07, p less than 0.01) and during exercise (control 0.21 +/- 0.08 vs. hydralazine 0.24 +/- 0.09, p less than 0.05). However, there were no statistically significant correlations between changes in radionuclide ejection fraction with hydralazine and changes in hemodynamic variables with hydralazine, either at rest or during exercise. Patients responding hemodynamically to hydralazine could not be separated from those not responding on the basis of the radionuclide ejection fraction at rest or changes in ejection fraction with hydralazine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗