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Biomedical subjects

J A Strom

Publications and source records attributed to J A Strom.

52 records · Page 3Linked to original sources
PubMed1985

Effects of timing of atrial systole on LV filling and mitral valve closure: computer and dog studies.

Atrioventricular (AV) delay that results in maximum ventricular filling and physiological mechanisms that govern dependence of filling on timing of atrial systole were studied by combining computer experiments with experiments in the anesthetized dog instrumented to measure phasic mitral flow. Ventricular filling volume is maximized at AV delay of 100 ms in the computer study and 80 ms in the dog study. At any time in diastole atrial contraction accelerates mitral flow, opening the mitral valve widely; atrial relaxation then decelerates mitral flow, moving the valve leaflets toward closure. The time the valve remains closed following atrial systole varies inversely with AV delay. When AV delay is optimal, the mitral valve is moving rapidly toward closure but is not yet closed at onset of ventricular systole. The decline in filling volume as AV delay decreases below its optimum value is primarily the result of premature termination of atrial ejection by ventricular systole. As AV delay increases above its optimal value, filling volume progressively decreases because of premature mitral valve closure that limits effective diastolic filling period. There is no significant retrograde mitral flow at any point in diastole for any AV delay.

Animals↗
PubMed1984

Acute limb ischemia following aortic reconstruction. A preventable cause of increased mortality.

Acute limb ischemia following aortic reconstruction is primarily related to intraoperative technical errors and is associated with significantly increased mortality. Elective aortic reconstruction was performed on 262 patients between 1975 and 1981. Surgical indications were aneurysm in 84 patients (32%), occlusive disease in 125 (48%), and both of these in 53 (20%). Acute limb ischemia developed postoperatively in 27 patients (10.3%); it was noted at the conclusion of the operation in five (19%) of them and within the first 48 hours in 22 (81%). The mortality was greater in the combined aneurysm and occlusive disease group than in the aneurysm-only and occlusive disease-only groups, primarily because of an increased incidence of myocardial disease in the combined group. Postoperative limb ischemia was mainly a result of technical error and resulted in increased mortality in all groups.

Aged↗
PubMed1984

Autotransfusion in complex abdominal aneurysms.

We have used a simple adaptation of the cardiotomy suction apparatus for autotransfusion during operation for four aortocaval fistulas and two ruptured internal iliac aneurysms. This has allowed significant blood salvage and maintenance of intraoperative hemodynamic stability. We have had no intraoperative complications and have noted no renal or pulmonary compromise postoperatively. One patient had minor coagulopathy postoperatively that was corrected with fresh frozen plasma and platelet transfusion during the first 12 hours. Autotransfusion for aortocaval fistulas and ruptured internal iliac aneurysms is safe, simple, clinically beneficial and cost effective.

Aneurysm↗
PubMed1983

Cerebral arterial spasm--a controlled trial of nimodipine in patients with subarachnoid hemorrhage.

We enrolled 125 neurologically normal patients with intracranial aneurysms in a multi-institution, prospective, double-blind, randomized, placebo-controlled trial within 96 hours of their subarachnoid hemorrhage, to determine whether treatment with the calcium blocker nimodipine would prevent or reduce the severity of ischemic neurologic deficits from arterial spasm. A deficit from cerebral arterial spasm that persisted and was severe or caused death by the end of the 21-day treatment period occurred in 8 of 60 patients given placebo and in 1 of 56 given nimodipine (P = 0.03, Fisher's exact test). Analysis of the amount of basal subarachnoid blood on pre-entry CAT scans in patients with deficits from spasm showed that an increase in subarachnoid blood was not associated with a worse neurologic outcome among patients who received nimodipine, unlike the situation in patients given a placebo. There were no side effects from nimodipine. We conclude that nimodipine should be given to patients who are neurologically normal after subarachnoid hemorrhage in order to reduce the occurrence of severe neurologic deficits due to cerebral arterial spasm.

Adolescent↗
PubMed1983

A noninvasive comparison of left ventricular performance in sickle cell anemia and chronic aortic regurgitation.

Abnormalities of the cardiovascular system are common in patients with sickle cell anemia (SS). Noninvasive testing to document left ventricular dysfunction has yielded conflicting results. Left ventricular performance was evaluated in 27 patients with SS by M-mode and 2-D echocardiography, and systolic time intervals. Comparisons were made to 25 normal controls, and to 22 patients with chronic aortic regurgitation. Left ventricular diastolic diameter (LVDD) and cardiac index (CI) were significantly greater in the patients with SS than in controls (LVDD 5.3 +/- 0.4 vs. 4.7 +/- 0.5 cm; CI 4.2 +/- 1.3 vs. 3.1 +/- 0.8 liters/min/m2; both p less than 0.001). Left ventricular ejection fraction (EF) was slightly, but significantly less (62.9 +/- 7.3 vs. 67.0 +/- 5.4; p less than 0.05). In comparison to the patients with chronic aortic regurgitation, the LVDD in the patients with SS was slightly, but significantly lower (LVDD 5.3 +/- 0.4 vs. 5.9 +/- 0.6 cm; p less than 0.05). There was no significant difference between the patients in EF or CI (EF 62.9 +/- 7.3 vs. 63.3 +/- 4.4; CI 4.2 +/- 1.3 vs. 5.0 +/- 1.0 liters/min/m2; NS). Left ventricular EF was below 55 in three patients who also had hypertension at the time of examination. We conclude that patients with SS have resting left ventricular performance consistent with a high output state. Significant left ventricular dysfunction related to sickle cell disease alone was not demonstrated in this population, although the addition of hypertension appears to deleteriously affect resting left ventricular performance.

Adult↗
PubMed1982

Comparison of oral propranolol and verapamil for combined systemic hypertension and angina pectoris. A placebo-controlled double-blind randomized crossover trial.

The relative efficacies of oral verapamil, a calcium-entry blocking drug, and propranolol, a beta-adrenergic blocking drug, were compared in 12 patients who had both stable angina pectoris and mild to moderate systemic hypertension, using a placebo-controlled, double-blind, randomized crossover protocol. Compared with placebo, both propranolol and verapamil decreased the frequency of anginal attacks and the number of nitroglycerin tablets consumed, and increased exercise duration and total work; there were no significant differences in the antianginal effect of the two drugs. Both verapamil and propranolol reduced the supine and standing systolic and diastolic blood pressure measured at rest; compared with propranolol, however, verapamil had greater effects on standing diastolic blood pressure (p less than 0.002). Resting heart rate was reduced from placebo baseline with large doses of both drugs; compared with verapamil, however, propranolol exerted greater effects on resting heart rate and rate-pressure product. Plasma renin activity was increased from placebo baseline with verapamil (p less than 0.05), but was reduced with propranolol (p less than 0.05); no significant change in plasma aldosterone was seen with either drug. Verapamil appears to be a safe and effective treatment alternative to propranolol for relieving anginal symptoms, improving exercise tolerance, and reducing elevated systemic blood pressure in patients with both angina pectoris and mild to moderate systemic hypertension.

Adrenergic beta-Antagonists↗
PubMed1982

Glucagon, gastric inhibitory polypeptide and the gastrocolic response.

Serosal bipolar electrodes and strain gauge force transducers were placed on the right and left colon in subhuman primates to record spike discharges and circular muscular contractions. The effect of glucagon on colonic motor and electrical activity were studied before and after meals. Serum concentration of gastric inhibitory polypeptide was measured simultaneously 15 minutes before and 45 minutes after eating. Serum levels of gastric inhibitory polypeptide increased in response to eating; pre- and postcibal concentrations were not altered by glucagon. The gastrocolic response of the colon to eating was demonstrated. Glucagon inhibited the intrinsic activity of the entire colon before meals and partly inhibited the right colon after meals. Postcibal left colon activity was not inhibited by glucagon. This indicates that a distinct mechanism accounts for the left colonic postcibal increase in contractile and electrical spike activity. A neural or humoral mechanism is implicated but is not specifically identified.

Animals↗
PubMed1981

Left ventricular ejection fraction and its response to therapy in essential hypertension.

Left ventricular ejection fraction at rest and during treadmill and isometric handgrip exercise were determined in 16 patients with essential hypertension (mean age 47.4 years) before and after therapy. The untreated hypertensive patient showed a linear correlation between mean blood pressure and LVEF (r = 0.62, p less than 0.01). The relation of sitting, resting LVEF with systolic blood pressure was highly significant (r = 0.88, p less than 0.001). Prior to therapy no significant change in LVEF in response to exercise was noted. After therapy with captopril, a normal isotonic exercise response occurred consisting of a highly significant increase in ejection fraction (p less than 0.0025). Subjects receiving propranolol had a fall in LVEF with isometric stress (p less than 0.0025). These data suggest an increased ejection fraction in patients with essential hypertension when all other parameters of the heart are normal and an abnormal response to isotonic exercise which may be reversed with therapy.

Adult↗
PubMed1980

The demonstration of vegetations by echocardiography in bacterial endocarditis. An indication for early surgical intervention.

The visualization of vegetations by M-mode echocardiography in patients with infective endocarditis has been suggested to imply a poor prognosis regarding the development of major systemic emboli, congestive heart failure and the need for early surgical intervention. The question of using the finding of vegetations by echocardiography as an indication for surgery is controversial. To answer this question, 30 patients with the clinical diagnosis of endocarditis were studied by echocardiography. In 17 of the 30 (57 per cent) vegetations were present (aortic eight, mitral four, both mitral and aortic five), whereas in 13 (43 per cent) no vegetations were visualized. Infecting organisms were similar in each group; Streptococcus viridans being the most common. The patients with echocardiographically demonstrable vegetations had a higher incidence of congestive heart failure compared to the patients without (14 of 17 versus six of 13, p less than 0.05), major emboli (eight of 17 versus two of 13, p = NS) and need for valve surgery (17 of 17 versus two of 13, p less than 0.001). Mortality was not significantly different in the two groups (six of 17 versus three of 13, p = NS). Urgent or emergency surgery was required in 16 of 17 patients with vegetations. Thus, the demonstration of vegetations by echocardiography identified a subset of patients with more severe disease in whom early operative intervention was required.

Adult↗
PubMed1980

Frank orthogonal vectorcardiograms in humans during and after exposure to +Gz acceleration stress.

Frank orthogonal vectorcardiograms (VCGs) were recorded from 10 subjects prior to, during, and for 15 min after exposures to +3Gz , +5Gz, and +7Gz. The order of acceleration exposure was randomized, with the individual exposures separated by at least 1 week. Standard USAF anti-G suits were worn by all subjects. Detailed analysis of the scalar lead electrocardiograms revealed no abnormalities. There were no consistent signs of conduction disturbances or ischemic ST-T segment changes. The QRS axis of the VCG demonstrated posterior rotation in the sagittal plane and counterclockwise rotation in the transverse plane during +Gz stress. The changes in the VCGs recorded during +Gz stress appeared to be related to rotational changes of the heart due to mechanical stress and/or motion within the thorax. There were no ECG or VCG changes indicative of myocardial ischemia and/or damage during or after +Gz stress.

Acceleration↗
PubMedDate not supplied

Sustained improvement in flow-mediated vasodilation after short-term administration of dobutamine in patients with severe congestive heart failure.

BACKGROUND: In patients with severe congestive heart failure (CHF), short-term administration of dobutamine exerts sustained clinical benefits that are partially mediated by a training-like effect on skeletal muscle. Recently, physical training has been shown to enhance endothelial function in the skeletal muscle vasculature by improving endothelial function. Whether the dobutamine-induced training effect is also associated with an improvement in endothelial function in the skeletal muscle vasculature is currently unknown. METHODS AND RESULTS: Flow-mediated vasodilation in response to peak reactive hyperemia was evaluated in the forearms of 9 patients with severe CHF who were treated with dobutamine for 72 hours. Resting and peak hyperemic brachial artery blood flow and diameter (BABF [mL/min] and BAD [mm], respectively) were measured by 2-dimensional and Doppler ultrasonography at baseline, at 3 and 72 hours during dobutamine infusion, and at 2 and 4 weeks after discontinuation of dobutamine therapy. In addition, the brachial artery response to sublingual (SL) administration of nitroglycerin (NTG) was evaluated at baseline and at 2 and 4 weeks after discontinuation of dobutamine therapy. Ten patients with severe CHF who did not receive dobutamine served as control subjects. Resting BABF was significantly increased at 3 and 72 hours (391.2+/-31.8 and 366.8+/-31.0 mL/min, respectively, compared with 289.8+/-18.6 mL/min at baseline; P<0.05). Peak hyperemic BABF was not altered by dobutamine infusion compared with baseline values. The increase in BAD during peak hyperemic response was greater after infusion of dobutamine for 72 hours (15.2+/-2.7% versus 9.1+/-1.8%, P<0.05) and remained significantly greater for >/=2 weeks after discontinuation of dobutamine (12.3+/-2.2% versus 9.1+/-1.8%, P<0.05). In contrast to the peak hyperemic response, the increase in BAD (%) induced by SL NTG was unchanged by administration of dobutamine for 72 hours. Two and 4 weeks after discontinuation of dobutamine, NTG-induced increases in BAD were similar to the BAD noted at baseline. CONCLUSIONS: In patients with severe CHF, short-term administration of dobutamine for 72 hours selectively improves vascular endothelial function for >/=2 weeks.

Blood Flow Velocity↗