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Biomedical subjects

F A Gaffney

Publications and source records attributed to F A Gaffney.

At least 55 records · Page 3Linked to original sources
PubMed1984

Pathophysiologic mechanisms of cardiac tamponade and pulsus alternans shown by echocardiography.

A pericardial effusion is easily recognized by echocardiography, but the diagnosis of cardiac tamponade by echocardiography is controversial. Recently, several reports have indicated that right ventricular (RV) or right atrial (RA) diastolic collapse represent highly specific and sensitive signs of a hemodynamically significant pericardial effusion. This report evaluates the pathophysiologic significance of these findings in 3 patients. One patient had classic clinical and hemodynamic features of tamponade without typical echocardiographic features; 1 had typical echocardiographic features of tamponade without the characteristic clinical or hemodynamic features; and 1 had all the findings characteristic of tamponade, including mechanical and electrical alternans. The first patient had increased right-sided cardiac pressures and RV hypertrophy, which prevented RV or RA collapse. The second patient had low right-sided intracardiac pressures, which allowed RV and RA diastolic compression to occur during early and mid-diastole. In the third patient, severe holodiastolic impairment of right-sided filling, and presumed decreased pulmonary venous and pericardial compliance, in the setting of tamponade produced a beat-to-beat alternation of RV and left ventricular filling with associated electrical and mechanical alternans. RV or RA collapse during diastole occurs when intrapericardial pressure equals or exceeds intracardiac pressure. Increases in wall stiffness of chamber pressures may prevent diastolic collapse in the setting of tamponade. Conversely, extremely low intracardiac pressures may allow diastolic collapse to occur in the absence of overt cardiac tamponade. The extent and timing of the RA or RV collapse, rather than its mere occurrence, are important in the diagnosis of cardiac tamponade by echocardiography.

Adolescent↗
PubMed1984

Simplified right ventricular volume algorithm using one digitized view and transducer tilt angle.

We recently described a technique for determining in-vitro right ventricular volume from multiple two-dimensional echocardiographic views taken at sequential angles. The product of sectional area and center of mass for each view (U) is integrated over the angle of tilt of the transducer to give volume. We now note that the plot of U vs. angle is almost triangular when the echoes are taken from the short axis position. The maximal U value (the vertex of the triangle) and the total angle span (the base) are then used in the equation (maximal U x total angle span)/2 to calculate volume. This new approximation provides an excellent correlation with actual volumes. We conclude that the triangular approximation provides accurate in-vitro estimates of right ventricular volume in normal human hearts.

Algorithms↗
PubMed1983

Hydrogen peroxide contrast echocardiography.

Several agents are used as echocardiographic contrast agents, but their unreliability discourages routine clinical use. Studies from the early 1960s suggest that dilute hydrogen peroxide (H2O2) is a safe intravascular agent. Its use was evaluated in contrast echocardiography. To obtain dense opacification reliably, H2O2 (3%) was passed through a sterile 0.2 micron Millipore filter and diluted with heparinized saline solution to make a 0.1 to 0.2% solution. A drop of blood was withdrawn from an indwelling peripheral venous needle into a syringe containing 0.5 to 2.0 ml of the dilute H2O2 and the contents injected. Studies in dogs, normal adults and 36 patients with noncyanotic congenital and acquired cardiac disorders produced dense opacification with no complications. In vitro mixture of H2O2 (0.3%) with leukocyte-poor blood or plasma produced only a few microbubbles, while addition to whole blood or buffy coat produced many, suggesting a role for leukocyte peroxidase. H2O2 contrast echocardiography is simple, inexpensive, and reliably provides dense, sustained opacification. This study and previous studies suggest that intravenous injection of 0.2% H2O2 can be done safely. Great caution should be exercised in patients with severe pulmonary hypertension or large right-to-left shunts because little clinical experience with H2O2 is available.

Animals↗
PubMed1983

Noninvasive recognition of the parchment right ventricle (Uhl's anomaly arrhythmogenic right ventricular dysplasia) syndrome.

The case of a 53-year-old man with right heart failure, selective enlargement of the right-sided cardiac chambers, and recurrent sustained ventricular tachycardia is presented. Echocardiographic, radionuclide ventriculographic, and angiographic studies were typical of the right ventricular abnormalities in Uhl's anomaly; electrocardiographic and electrophysiologic findings were those of arrhythmogenic right ventricular dysplasia. Features of this unusual cause of cardiac failure and ventricular arrhythmias in the adult are reviewed, and compared to previous reports of both Uhl's anomaly and arrhythmogenic right ventricular dysplasia. We postulate that these two syndromes are manifestations of a single, presumably congenital, pathophysiologic process--the "parchment right ventricle" syndrome.

Echocardiography↗
PubMed1983

Abnormal cardiovascular regulation in the mitral valve prolapse syndrome.

Studies of patients with mitral valve prolapse syndrome have suggested autonomic nervous system dysfunction, but a precise definition of mechanisms is lacking. We measured supine and standing heart rate, blood pressure, cardiac output, oxygen consumption, plasma catecholamines, and blood volume in 23 symptomatic women with both echocardiographic and phonographic signs of MVP and in 17 normal control subjects. An analysis of the results revealed 2 distinct subgroups of patients: those with normal heart rates but increased vasoconstriction (Group I, n = 10) and those with orthostatic tachycardia (Group II, n = 13). Group II patients had heart rates at rest supine of 97 +/- 3 compared with 79 +/- 2 in Group I patients and 78 +/- 8 in control subjects. Estimated total blood volumes were lowest in Group I patients, intermediate in Group II patients, and highest in control subjects (p less than 0.05). Other measurements at rest supine were similar in patients and controls. After standing for 5 minutes, patients had a higher mean plasma epinephrine value, diastolic blood pressure (81 +/- 2 versus 74 +/- 3 mm Hg, p less than 0.05), and peripheral resistance (1,878 +/- 114 versus 1,414 +/- 92, dynes s cm-5, p less than 0.01), wider arteriovenous oxygen difference (6.7 +/- 0.4 versus 5.3 +/- 0.5 vol%), and lower stroke volume index (26 +/- 2 versus 33 +/- 2 ml/m2, p less than 0.01) than did the control subjects. Cardiac output was normal in Group II patients but reduced in Group I patients, who demonstrated marked vasoconstriction. No patient had evidence of a "hyperkinetic" circulatory state. A cycle of decreased forward stroke volume, vasoconstriction, and blood volume contraction appears to be present in at least some symptomatic patients with MVP.

Adult↗
PubMed1983

Hemodynamic and neuroendocrine responses to acute and chronic alpha-adrenergic blockade with prazosin and phenoxybenzamine.

We investigated the relevance of the selective alpha 1-adrenergic receptor blockade produced by prazosin to its blood pressure-lowering efficacy in man. The hemodynamic and neuroendocrine responses to the acute and chronic oral administration of prazosin and phenoxybenzamine were compared in a randomized, double-blind, placebo-controlled, crossover study of 11 patients with essential hypertension. These responses were also evaluated during lower body negative pressure and dynamic bicycle exercise, which produce potent but diversified activation of the sympathetic nervous system. In the acute studies, arterial blood pressure decreased to similar levels with prazosin or phenoxybenzamine; however, hemodynamic and neuroendocrine responses differed both before and during sympathetic nervous system activation. Prazosin lowered arterial blood pressure by reducing total peripheral resistance (p less than 0.05). In contrast, phenoxybenzamine produced a modest reduction in cardiac output (8%, p less than 0.05) with little change in total peripheral resistance, forearm vascular resistance or forearm blood flow. Additionally, plasma norepinephrine concentration and heart rate rose to significantly higher levels with prazosin (p less than 0.02) than with phenoxybenzamine, a difference that was most evident with lower body negative pressure or dynamic exercise. Baroreceptor control of arterial pressure homeostasis was preserved with both agents, except during marked degrees of cardiovascular stress. With chronic therapy, the circulatory responses adapted to the alpha-adrenergic antagonists, and both drugs produced similar hemodynamic and neuroendocrine profiles. The differences with acute administration may be the result of a more rapid onset of action and a more marked degree of alpha-adrenergic blockage with prazosin than with phenoxybenzamine therapy, rather than to any difference in their alpha 1- and alpha 2-adrenergic receptor blocking properties. Moreover, the findings of the present study suggest that the prejunctional alpha 2-receptor, autoinhibitory to sympathetic neuronal norepinephrine release, is of no functional significance in patients with essential hypertension.

Adrenergic alpha-Antagonists↗
PubMed1983

Effects of long-term clonidine administration on the hemodynamic and neuroendocrine postural responses of patients with dysautonomia.

Patients with mitral valve prolapse syndrome (MVPS), vasoregulatory asthenia, and poor postural adjustment often have orthostatic intolerance characterized by tachycardia and a narrow pulse pressure on standing. Autonomic dysfunction is thought to play an important role. Increased alpha-adrenergic activity has been shown in MVPS patients with orthostatic intolerance. We measured hemodynamic and neuroendocrine responses to long-term oral clonidine therapy in eight women, aged 36 +/- 1.8 years (27 to 44 years). None had responded favorably to beta-blockers. Heart rate, blood pressure, oxygen consumption, cardiac output, and plasma norepinephrine levels were measured in both supine and standing positions, before and after one to four weeks of clonidine (0.3 to 0.4 mg daily). Clonidine reduced standing plasma norepinephrine levels, total peripheral resistance, and diastolic blood pressure; a smaller decrease in cardiac output on standing was noted. Plasma volumes increased 12 percent. Mild reductions in plasma catecholamines and total peripheral resistance are associated with fewer, not more, orthostatic symptoms in this group of patients. "Placebo" or mild sedative effects may explain part of the response to clonidine, but the hemodynamic and neuroendocrine data suggest that decreased alpha-adrenergic hyperactivity may also be important.

Adult↗
PubMed1982

Cardiovascular function in patients with progressive systemic sclerosis (scleroderma).

Sixteen patients with progressive systemic sclerosis (PSS), including 3 with the "CREST" (calcinosis, Raynaud's, esophageal dysfunction, sclerodactyly, and/or telangiectasias) variant, were evaluated with resting M-mode echocardiography and noninvasive measurements of cardiac output at rest and during submaximal exercise to determine the nature and extent of any cardiovascular impairment. No patient had arterial hypertension, significant renal impairment, clinical evidence of large vessel coronary artery disease, or severe pulmonary dysfunction. The duration of disease was 1 to 12 years (9 to 30 for patients with the CREST variant). Echocardiographic abnormalities included increased right ventricular dimension (3 patients), reduced left ventricular ejection fraction (3 patients), and pericardial effusion (3 patients). Cardiac index (CI) and stroke volume index (SVI) at rest were similar for patients and controls. Patients and controls were exercised to similar heart rates (130 +/- 3 vs 124 +/- 4; p, NS). Total peripheral resistance (TPR) was higher for patients (1123 +/- 81 vs 810 +/- 44 dyn X s X cm-5) and their mean SVI failed to increase significantly compared with sitting rest values (30 +/- 2 vs 35 +/- 3 ml/m2). The control subjects had the expected increase in SVI (36 +/- 2 vs 51 +/- 5; p less than 0.01). Ten patients with an abnormal hemodynamic response to exercise had a normal echocardiographic circumferential fiber shortening (VCF) or ejection fraction (EF) at rest. The data indicate that PSS patients have a greater degree of cardiovascular dysfunction than would be predicted from clinical data and laboratory evaluation of cardiovascular and pulmonary function at rest. Multiple mechanisms, including right and left ventricular dysfunction and abnormal vasoconstrictor activity, are likely to contribute to the reduction in exercise capacity seen in patients with PSS.

Adult↗
PubMed1982

Passive leg raising does not produce a significant or sustained autotransfusion effect.

Passive leg raising is widely used to treat hypotension associated with hypovolemia. Presumably gravity causes a central translocation of leg venous blood and an increase in filling pressure, cardiac output, and arterial pressure. Ten healthy volunteers, 25 to 35 years old, had measurements of heart rate, blood pressure, and cardiac output in the supine position after 20 sec and 7 min of 60 degrees passive leg elevation. The protocol was performed 3 and 45 min after the subjects changed from an ambulatory upright to a supine position. Stroke volume and cardiac output increased transiently (8-10%) when the legs were raised after 3 min rest in the supine position. By 7 min of leg elevation, these beneficial effects disappeared. After 45 min supine, leg raising had no effect on stroke volume or cardiac output but increased blood pressure (4 mm Hg) by increasing peripheral resistance (15%). Thus, leg raising, like application of the MAST trousers, fails to produce any sustained increase in cardiac output or stroke volume. Small venous leg volumes and time-dependent changes in the distribution of venous volume and compliance may explain the absence of any sustained 'autotransfusion' effect.

Adult↗
PubMed1981

Distinctive anthropometric characteristics of women with mitral valve prolapse.

We examined the hypothesis that mitral valve prolapse is often associated with an inherited, anthropometrically distinct habitus. Using standard echo- and phonocardiographic techniques, we identified 60 subjects with mitral valve prolapse, 21 first-degree relatives (12 with mitral valve prolapse and nine normal) and a control group of 57 normal women. Patients with "silent" (echo only) mitral valve prolapse or the Marfan syndrome were excluded. Analysis of measurements taken of the first 39 patients and 46 control subjects revealed that, in relation to their height, patients with mitral valve prolapse had narrower anteroposterior chest diameters and longer arm spans than did the women in the control group. Linear discriminant analysis produced the equation: Z = 17.511 + 98.6 (anteroposterior chest diameter/height)--27.3 (arm span/height). Those with mitral valve prolapse tended to score below zero (mean, --0.62), whereas normal subjects tended to score above zero (mean, --0.39; p less than 0.001). The equation was tested prospectively on 53 subjects, including the 21 family members, and correctly classified 75 percent of all unrelated subjects and 86 percent of the family members as normal or having mitral valve prolapse. Both mitral valve prolapse and discriminant classification followed an autosomally dominant pattern of inheritance. We conclude that a significant proportion of patients with mitral valve prolapse have an autosomally dominant, inherited, anthropometrically distinct habitus, suggesting that mitral valve prolapse is only one component of a generalized developmental syndrome.

Adult↗
PubMed1981

Hemodynamic effects of Medical Anti-Shock Trousers (MAST garment).

Despite widespread use of the Medical Anti-Shock Trousers (MAST) little is known about the exact mechanism by which they increase arterial pressure. It is assumed that an autotransfusion occurs. To examine this question, blood pressure, heart rate, forearm blood flow, cardiac output, and stroke volume were measured in ten healthy adults, supine and during 60 degree headup tilt with MAST garment pressures of 409 and 100 mm Hg. Supine, the garment produced no net 'autotransfusion,' but raised blood pressure (27%) by increasing peripheral resistance (48%) with decreased stroke volume and cardiac output (18%). During headup tilt without the MAST device, venous pooling in the legs decreased stroke volume (52%), cardiac output (30%), and increased total peripheral resistance (40%). Application of the garment during tilt shifted this blood centrally, producing increased stroke volume (52%), cardiac output (30%), and increased total peripheral resistance (40%). Application of the garment during tilt shifted this blood centrally, producing increased stroke volume (14%). In supine normovolemic subjects, the garment raised pressure almost exclusively by increased systemic afterload. Forearm vascular resistance did not change and the increased pressure augmented flow to the arm, i.e., to noncompressed tissue. With increased venous pooling during tilt, the MAST garment acted as a 'G-suit' and caused a central shift of blood volume. These findings could explain: 1) why fluid replacement is not always adequate to maintain pressure when deflating the trousers; 2) why the trousers should not be used if one wishes to avoid increasing afterload (e.g., certain patients with acute myocardial infarction). We conclude that the MAST garment acts as a local, effective, nonpharmacologic vasoconstrictor and should be used when such an effect is clinically appropriate.

Adolescent↗
PubMed1981

Total plasma creatinine: an accurate measure of total striated muscle mass.

Creatinine is a metabolite unique to striated muscle. Measurement of 24-h urinary creatinine excretion is an established method for estimating striated muscle mass. However, accurate assessment of urinary creatinine excretion is often impractical. We investigated the hypothesis that total plasma creatinine could be used instead of urinary creatinine excretion to estimate body composition. In 24 men, plasma volume and plasma creatinine concentration were measured, and total plasma creatinine was calculated as the product of these two measurements. Other measurements included urinary creatinine excretion, total body water, and anthropometry. Total plasma creatinine correlated strongly with urinary creatinine excretion (r = 0.82) and with weight, total body water, and anthropometrically estimated lean body mass. Muscle mass could be predicted by the equation: 0.88 x total plasma creatinine (mg). To verify this relationship, total plasma creatinine was prospectively measured in four dogs, then their total striated muscle was removed and weighed. Predicted muscle mass was within +/- 3.9% (range = 0.5-10.8%) of observed muscle mass. The ability to estimate muscle mass conveniently and accurately from total plasma creatinine should prove valuable for future studies in physiology and body composition.

Adult↗