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Biomedical subjects

G C Timmis

Publications and source records attributed to G C Timmis.

At least 55 records · Page 3Linked to original sources
PubMed1991

Development of runner's anemia during a 20-day road race: effect of iron supplements.

Intense training for long-distance running has been associated with reduced hemoglobin (Hb) levels and low iron stores. Whether iron supplementation helps prevent this "runner's anemia" remains controversial. To determine the relationship between iron status and the early stage of reduced Hb levels in male runners, we examined hematologic variables in 15 healthy men (ages 25 to 47 yrs) who ran twice their regular training distance in 20 days during a 500-km road race. Nine of the runners took iron-containing tablets which provided an average of 36 mg/d of iron, while the other six did not take iron supplements. Only one of the 15 subjects had a low Hb concentration (less than 14 g/dl) before the race. After 10 days (285 km), low Hb levels (p less than 0.001) were found in 12/15; six of these runners took iron supplements. However, following a 2-day rest period and five more days of running, only 5/15 and 7/15, respectively, had low Hb levels. Serum iron, ferritin, total iron binding capacity, and percent transferrin saturation values remained within normal limits and did not change significantly. Reticulocyte counts progressively increased, becoming 8-fold higher than at baseline (p less than 0.001), irrespective of the use of iron supplements. "Runner's anemia" developed in 11/15 (73%) of the subjects, independently of their iron status and iron intake. The reductions in Hb were accompanied by parallel decreases in RBC count and hematocrit, and by a significant reticulocytosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Exercise prescription for hypertensive patients.

Physical conditioning has been suggested as a useful adjunct or alternative to pharmacologic therapy in the treatment of borderline or mild hypertension. This recommendation stems from numerous studies that have demonstrated modest decreases in blood pressure in hypertensive individuals. Exercise guidelines should be based on preliminary exercise testing and modified to accommodate those patients who are taking a variety of antihypertensive medications. Although pure isometric exercise is generally contraindicated in hypertensive patients, potentially valuable training activities that involve a substantial static component, including arm crank ergometry and mild-to-moderate load weight training, probably requires individual assessment.

Blood Pressure↗
PubMed1991

Myocardial and aerobic requirements for an upper body exerciser: implications for cardiac rehabilitation.

To assess the cardiorespiratory, hemodynamic, and electrocardiograph (ECG) responses to an upper body exercise device, we studied ten cardiac men (mean age +/- SD = 58.0 +/- 6.5 years) who performed three five-minute exercise bouts at metronome settings of 20, 50, and 80 clicks per minute. Operation of the device involved shuttling a plastic buoy on two 6-m waxed ropes between two persons. Aerobic requirements were generally appropriate for arm training, corresponding to mean values of 5.3, 7.0, and 10.1 ml.kg-1.min-1 at the three progressive metronome settings. Perceived exertion (Borg, 6 to 20 scale) at these work rates was 8.3, 10.4, and 14.6, whereas average heart rate and systolic blood pressure responses were 77, 85, and 114 beats.min-1 and 145, 158, and 175 mmHg, respectively. Continuous ECG monitoring during upper body exercise revealed no significant ST-segment depression or serious arrhythmias. The device appears to be a safe and effective complement to a cardiac exercise training program.

Aged↗
PubMed1990

Validity of arm ergometer blood pressures immediately after exercise.

It is not possible to assess blood pressure (BP) by the standard cuff method during exercise primarily involving the arms. Consequently, such measurements are often taken immediately after (within 15 seconds) exercise. To assess the validity of this practice, 18 healthy men (mean age 32 years) who completed 3 progressive 3-minute workloads were studied during arm-crank ergometry. Ankle systolic BP was measured at the dorsalis pedis artery at seated rest, 15 seconds before completion of each exercise stage and immediately after each workload, using a Doppler stethoscope; simultaneous postexercise brachial systolic BPs were determined by auscultation. Brachial systolic BP during armcrank ergometry was estimated by the formula: (resting brachial systolic BP) + (exercise ankle systolic BP - resting ankle systolic BP). Brachial systolic BPs, obtained immediately after arm-crank ergometry, were significantly lower than those estimated during exercise (p less than 0.001), with corresponding mean values of 141 versus 153, 144 versus 173 and 151 versus 182 mm Hg at 150, 300, and 450 kg.m.min-1, respectively. The difference between measured (postexercise) and estimated pressures increased with progressive workloads. These findings indicate that systolic BPs taken by the standard cuff method immediately after arm-crank ergometry are likely to underestimate "true" physiologic responses.

Adult↗
PubMed1990

Successful resuscitation of a patient with critical aortic stenosis and cardiac arrest by peripheral cardiopulmonary support system.

Patients with critical aortic stenosis have an increased risk of complications during diagnostic cardiac catheterization, and those who arrest are particularly difficult to resuscitate. Recent advances in therapeutic techniques may change this unfavorable prognosis, as it is illustrated in the presented case. A 68 year-old women with critical aortic stenosis sustained a cardiac arrest during diagnostic cardiac catheterization. Conventional cardiopulmonary resuscitation for 45 minutes failed to restore cardiac function and rhythm, which had degenerated to ventricular fibrillation, electromechanical dissociation, and asystole. Peripheral cardiopulmonary support system restored cardiac rhythm and blood pressure, with a subsequent successful aortic valve replacement.

Aged↗
PubMed1990

Contribution of transesophageal echocardiography to patient diagnosis and treatment: a prospective analysis.

The capability of transesophageal (TEE) versus transthoracic (TTE) echocardiography as a diagnostic tool in clinical practice was prospectively examined in 86 consecutive cases. A conclusive diagnosis was possible in 95% with TEE, whereas the same result was achieved in 48% by TTE. Specifically, TEE provided a conclusive diagnosis in 14 of 16 cases of infective endocarditis, while TTE gave this result in 4 of the 16 cases (p less than 0.001). Similarly, TEE allowed a conclusive diagnosis in 11 of 11 instances of aortic dissection, while TTE gave this indication in two cases (p less than 0.001). TEE was similarly effective in eight of eight cases of atrial thrombi, whereas TTE gave the diagnosis in three of eight cases (p less than 0.01). In five subjects with intracardiac masses, TEE gave a conclusive diagnosis in all five, whereas TTE was able to diagnose conclusively in one subject (p less than 0.02). In seven patients with mitral regurgitation, TEE gave the conclusive diagnosis in all seven and TTE was able to provide this information in four (p = NS). TEE was able to provide a conclusive diagnosis in four patients with aortic insufficiency, and TTE gave the same information in two of the four (p = NS). In 14 patients with prosthetic valve dysfunction, TEE gave the diagnosis in 12 and TTE gave it in eight patients (p = NS). Both methods gave a conclusive diagnosis in 13 out of 13 cases of mitral stenosis (p = NS). Also, TEE provided a conclusive diagnosis in eight of eight patients with adult congenital heart disease and TTE gave this information in four (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Exercise and fitness.

Exercise testing and prescription appear to play an important role in promoting health maintenance strategies for women. Multistage exercise tolerance testing provides invaluable information in assessing the patient's functional capacity. The diagnostic significance of exercise-induced ST-segment depression is tenuous, however, in women with a low likelihood of heart disease. Research suggests that numerous physiologic mechanisms act to increase fetal tolerance to the circulatory and respiratory challenges of moderate maternal exercise. Moreover, appropriately prescribed endurance exercise programs for women are associated with the same salutary effects as men. Even more encouraging is the fact that these benefits can be attained at moderate levels of exercise--if long-term compliance is maintained.

Exercise↗
PubMed1990

Field test estimation of maximal oxygen consumption in wheelchair users.

To develop a field test to estimate maximal oxygen consumption (VO2max) in wheelchair users, 30 men (means age = 34.3 years) were subjected to progressive arm-crank ergometer testing with directly measured VO2max. Additionally, they performed a modified 12-minute wheelchair propulsion test for distance. Field testing was conducted within two weeks of the VO2max determination, using a standardized wheelchair (Quickie II) on a 0.1-mile indoor synthetic running track. Average peak power output and VO2max were 540 kg.m.min-1 and 22.0 ml.kg-1.min-1, respectively. The mean (+/- 1SD) wheelchair propulsion distance was 1.11 +/- 0.24 miles. Correlation of the field test data with the VO2max was highly significant (r = 0.84; p less than .001). The regression of distance in 12 minutes plotted against VO2max yielded the following equation: wheelchair propulsion (miles) = 0.370 + 0.0337 (VO2max, ml.kg-1.min-1), where the standard error of estimate = 0.13. These findings suggest that field testing can provide a good estimate of VO2max in selected wheelchair users.

Adult↗
PubMed1989

A theoretical description of blood flow through the mitral orifice.

A nonlinear differential equation describing the Doppler velocity profile for blood flow through the mitral valve has been derived. This equation is based on fluid dynamics and a simple, but comprehensive model of atrial and ventricular mechanics. A numerical solution to the equation is described and provides excellent agreement with Doppler velocity curves obtained clinically. One important result of the theory is that in patients with mitral stenosis, the slope of the clinically observed straight-line descent of the velocity profile is proportional to the mitral orifice area and inversely proportional to the atrioventricular compliance.

Blood Flow Velocity↗
PubMed1988

Discrimination of anterograde from retrograde atrial electrograms for physiologic pacing.

The morphology of bipolar electrograms recorded in the right atrium was examined in nine patients in an attempt to discriminate retrograde from anterograde atrial signals to an extent that would be useful for physiologic pacing. Peak-to-peak amplitude, duration, square root of energy (energy), maximum slew rate, mean slew rate, and polarity were examined in the time domain. Maximum frequency, half-power frequency, Fourier amplitude peak, and frequency of peak were measured in the frequency domain. There was a significant difference between anterograde and retrograde signals for all variables related to amplitude; these variables are peak-to-peak amplitude, energy, Fourier amplitude peak, maximum slew rate and mean slew rate. In seven of nine patients there was at least one variable sufficiently discriminating to insure reliable detection of anterograde signals while systematically rejecting retrograde signals. However, no individual variable was able to effect this discrimination in more than four patients and at least three variables were needed for all seven patients: maximum frequency, one of either energy and Fourier amplitude peak, and one of either frequency of peak or half-power frequency (six possible combinations). Thus, although differences between anterograde and retrograde atrial activity can be demonstrated in most patients, no single parameter displays sufficient discriminating power to facilitate physiologic pacing in patients exhibiting retrograde activity.

Atrial Function↗
PubMed1986

A prospective randomized clinical trial of intracoronary streptokinase versus coronary angioplasty for acute myocardial infarction.

We randomly assigned 56 patients who presented within 12 hours of their first symptoms of acute myocardial infarction to treatment with either intracoronary streptokinase or coronary angioplasty. The mean (+/- SD) duration of symptoms (3.0 +/- 1.2 hours in the group treated with angioplasty vs. 3.6 +/- 1.8 in the group treated with streptokinase; P not significant) and time to recanalization (4.1 +/- 1.4 hours vs. 4.8 +/- 1.7 hours; P not significant) were similar in both groups. Coronary recanalization was achieved in 83 percent of the patients treated with angioplasty and in 85 percent of those treated with streptokinase (P not significant). Residual luminal stenosis in the coronary artery was significantly decreased after angioplasty, as compared with streptokinase therapy (43 +/- 31 percent of patients vs. 83 +/- 17; P less than 0.001). Residual stenosis of 70 percent or more was present in 4 percent of the angioplasty-treated patients and in 83 percent of the streptokinase-treated patients (P less than 0.01). Ventricular function after therapy was assessed by serial contrast ventriculograms. Increases in both global ejection fraction (8 +/- 7 percent vs. 1 +/- 6; P less than 0.001) and regional wall motion (+1.32 +/- 1.32 SD vs. +0.59 +/- 0.79 SD; P less than 0.05) were greater for the angioplasty group. We conclude that angioplasty and streptokinase produce similar rates of early coronary reperfusion during evolving transmural myocardial infarction. However, angioplasty is significantly more effective in alleviating the underlying coronary stenoses, and this may result in more effective preservation of ventricular function after therapy.

Angiography↗
PubMed1986

Attenuation of exercise training effects in patients taking beta blockers during early cardiac rehabilitation.

Cardiorespiratory responses to graded treadmill tests administered 1 month after myocardial infarction or coronary bypass surgery and again after 4 weeks of aerobic training were compared in 24 patients taking beta blockers and 15 control patients. There were no significant differences before training between the groups in age, weight, ventricular ejection fraction, oxygen uptake (Vo2) during the fixed work load (1.7 mph/10% grade), Vo2 at the ventilatory threshold, or Vo2max. After training, Vo2max was significantly increased (p less than 0.05) by 16% in the beta-blocker group and by 21% in controls. However, the group taking beta blockers showed no significant change in oxygen pulse (Vo2/heart rate) at the fixed work load or at the ventilatory threshold, whereas the controls increased Vo2/heart rate at the fixed work load by 9% (p less than 0.05) and at the ventilatory threshold by 22% (p less than 0.05). Metabolic and ventilatory responses to submaximal exercise should therefore also be considered when evaluating the efficacy of exercise training in patients taking beta blockers.

Adrenergic beta-Antagonists↗
PubMed1986

Accuracy of computerized electrocardiographic identification of left ventricular hypertrophy as determined by echocardiographic measurements of left ventricular mass: evaluation of a widely used computer program.

The Hewlett-Packard 1000 electrocardiographic management system employs a user-interactive computer with revisable software. The diagnostic accuracy of this system in predicting left ventricular hypertrophy has been evaluated by comparing computer-predicted with anatomic left ventricular hypertrophy. The latter was defined as a left ventricular mass greater than 247 g as determined by M-mode echocardiography within 1 week of the computerized electrocardiogram. In this study, the Hewlett-Packard system was evaluated in 134 consecutive patients having anatomic left ventricular hypertrophy and 157 similarly studied patients with a normal left ventricular mass. By means of various combinations of voltage criteria, ST-T wave changes, abnormal QRS duration or ventricular activation time, left atrial enlargement and left axis deviation, the computer correctly identified 43 of 134 patients with left ventricular hypertrophy (sensitivity 32%); left ventricular hypertrophy was suggested or identified in an additional 18 patients with a normal left ventricular mass (specificity 89%). Graded probability statements (that is, the "strength" of the left ventricular hypertrophy diagnosis) increased with ventricular mass not only in patients with anatomic left ventricular hypertrophy but also in the patients with a "false positive" computerized electrocardiogram. Overall diagnostic accuracy was improved only in men by adjusting the definition of left ventricular hypertrophy for sex (at least 300 g for men and 220 g for women). Diagnostic accuracy was significantly better in patients 65 years of age and younger than in older patients (p = 0.007). It is concluded that the overall performance of this computer program (version ECLSB6) requires modification to improve its accuracy in identifying left ventricular hypertrophy.

Age Factors↗