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Biomedical subjects

F G Dunn

Publications and source records attributed to F G Dunn.

At least 109 records · Page 6Linked to original sources
PubMed1983

Cardiovascular changes after weight reduction in obesity hypertension.

Intravascular volumes and systemic and regional hemodynamic variables were measured before and after weight reduction in 12 patients with obesity and essential hypertension. These findings were compared with those in nine patients who did not have any weight loss. Reduction of mean arterial pressure significantly correlated with the fall in total body weight (r = 0.46, p less than 0.05). Total circulating and cardiopulmonary blood volumes were significantly reduced (p less than 0.05 and p less than 0.01, respectively), and these changes permitted a decreased venous return and cardiac output (p less than 0.01). This fall in cardiac output was directly related to a contracted total blood volume (r = 0.49, p less than 0.05) and decreased cardiopulmonary blood volume (r = 0.52, p less than 0.05). Patients who did not lose weight showed no changes in any of these hemodynamic measurements. In addition, weight loss was associated with reduced resting circulating levels of plasma norepinephrine (p less than 0.01), suggesting that diminished adrenergic function may also be related to weight reduction and its associated fall in arterial pressure.

Blood Pressure↗
PubMed1983

Dimorphic cardiac adaptation to obesity and arterial hypertension.

Cardiovascular function and structure were evaluated by M-mode echocardiography and systemic hemodynamics in paired lean and obese patients, either hypertensive or normotensive. Compared to lean patients, obese patients had greater left atrial (p less than 0.0001), ventricular (p less than 0.001), and aortic root (p less than 0.002) diameters; posterior and septal wall thickness (p less than 0.001); and ventricular mass, cardiac output, stroke volume, and stroke work (all p less than 0.0001). Hypertensive patients had increased posterior wall thickness, end diastolic wall stress, stroke work (p less than 0.01), and a lower radius to posterior wall thickness ratio indicating concentric hypertrophy (p less than 0.001) when compared to normotensive patients. Cardiac adaptation to obesity consists of left ventricular dilatation and hypertrophy (eccentric hypertrophy) irrespective of arterial pressure levels. In contrast, essential hypertension solely produces concentric hypertrophy. Both obesity and hypertension increase left ventricular stroke work by disparate hemodynamic mechanisms; their presence in the same patient will tax the heart and increase the long-term risk of congestive failure.

Adult↗
PubMed1982

Early hypertension and cardiac work.

Myocardial function and ventricular work in early essential hypertension were assessed by comparing systemic hemodynamics and echocardiographic data in 33 normotensive subjects and 38 hypertensive patients, all without left ventricular hypertrophy. External work (tension-time index and cardiac work) and internal work (fiber shortening velocity) were significantly increased in the patients with mild hypertension. Because factors other than blood pressure contribute to cardiac work, antihypertensive therapy must favorably affect both blood pressure and cardiac work.

Adult↗
PubMed1982

Hemodynamics, biochemical and reflexive changes produced by atenolol in hypertension.

Hemodynamic (systemic and regional), metabolic and cardiovascular reflexive variables were measured before and after 4 weeks of beta blockade with atenolol in 10 patients with mild essential hypertension. Atenolol reduced mean arterial pressure, heart rate, cardiac index (all p less than 0.005) and renal vascular resistance (p less than 0.01) and increased total peripheral resistance (p less than 0.005). Glomerular filtration rate and renal blood flow were unchanged; plasma renin activity fell 43%. Reflexive cardioacceleration during the Valsalva maneuver and upright passive tilt was blunted. No changes were observed in circulating fluid volumes. In six patients followed for 1 year, blood pressure and heart rate were maintained at levels similar to those during the first 4 weeks. Atenolol was shown to be an effective oral antihypertensive that has no apparent deleterious hemodynamic effects on the renal and splanchnic circulations.

Adrenergic beta-Antagonists↗
PubMed1982

Borderline hypertension and obesity: two prehypertensive states with elevated cardiac output.

Systemic, renal and splanchnic hemodynamics, intravascular volume, circulating catecholamine levels and plasma renin activity were compared in 39 patients with borderline hypertension and 28 normotensive subjects, who were less than 5% (n = 42, lean patients) or more than 40% overweight (n = 25, obese patients). Lean borderline hypertensive patients had greater cardiac output (p less than 0.05), heart rate (p less than 0.01) and renal blood flow (p less than 0.05); cardiopulmonary redistribution of intravascular volume (p less than 0.05); and higher circulating norepinephrine levels (p less than 0.05). Obese normotensive subjects also showed an increased cardiac output (p less than 0.005), stroke volume (p less than 0.01), left ventricular stroke work (p less than 0.05), and renal blood flow (p less than 0.05) (but not respective indexes), but intravascular volume was expanded (p less than 0.05) without redistribution and circulating catecholamine levels were normal. Obese borderline hypertensive patients had hemodynamic characteristics similar to those of obese normotensive subjects except for an increased peripheral resistance (p less than 0.05). The data indicate that although both populations have an increased cardiac output, the lean borderline hypertensive patients have signs of enhanced adrenergic activity as evidenced by higher circulating catecholamine levels and heart rate with blood volume translocation to the cardiopulmonary circulation. In contrast, the obese subjects (whether normotensive or borderline hypertensive), who also have increased cardiac output, seem to have normal adrenergic activity and an expanded intravascular volume without cardiopulmonary redistribution.

Adult↗
PubMed1981

Echocardiographic diastolic ventricular abnormality in hypertensive heart disease: atrial emptying index.

To analyze changes in left ventricular diastolic properties in hypertensive heart disease, the atrial emptying index was used to assess the rapid phase of diastolic filling of the left ventricle. Ten normal subjects (Group 1), 11 hypertensive patients without evidence of cardiac involvement (Group 2) and 10 hypertensive patients with echocardiographic evidence of left ventricular hypertrophy (Group 3) were compared using M mode echocardiography and systemic hemodynamic data. Whereas cardiac index (dye-dilution method) and rate of circumferential fiber shortening (echocardiogram) were normal in all three groups, there was a progressive increase in left atrial index (p less than 0.001, Group 1 versus Group 2 and versus Group 3) and a progressive decrease in the atrial emptying index (p less than 0.001, Group 1 versus Group 2 and versus Group 3). No correlation existed between the atrial emptying index and the left atrial index, mean arterial pressure or total peripheral resistance in any of the three groups. These data suggest that rapid filling of the left ventricle is reduced early in hypertension, even before electrocardiographic or systolic echocardiographic abnormalities are detectable. The atrial emptying index therefore appears to be an early indicator of abnormalities of left ventricular diastolic compliance in uncomplicated hypertension.

Adult↗
PubMed1981

Hypertension in the elderly: haemodynamic, fluid volume and endocrine findings.

1. Systemic and renal haemodynamics, intravascular volume, circulating catecholamines and plasma renin activity were measured in 18 patients with established essential hypertension who were older than 60 years of age. Each patient was matched with respect to mean arterial pressure, body surface area, race and sex with a patient that was younger than 42 years of age. 2. When compared with the younger group, elderly patients had a lower cardiac output, impaired myocardial reserve, lesser aortic elasticity, higher total peripheral resistance, more contracted intravascular volume and higher circulating noradrenaline levels. 3. Similar effects of age, although less pronounced, have been reported in normotensive subjects. We conclude that essential hypertension is a pathophysiological process that seems to accelerate the natural physiological haemodynamic, fluid volume and endocrine processes of aging.

Adult↗
PubMed1981

Borderline hypertension: relationship between age, hemodynamics and circulating catecholamines.

The relationships between age, systemic and renal hemodynamics, circulating catecholamines (norepinephrine, epinephrine and dopamine) and intravascular volumes were studied in 38 normotensive subjects and in 77 patients with borderline essential hypertension. Borderline hypertensive patients had a higher cardiac index (p less than 0.02) and renal blood flow (p less than 0.05) than normotensive subjects if they were younger than 30 years of age, whereas in older patients no difference was observed. In contrast, total peripheral resistance was normal in young borderline hypertensive patients, but significantly increased (p less than 0.02) in patients older than age 40 years. Cardiac output (r = -0.28, p less than 0.01) and renal blood flow (r = -0.47, p less than 0.001) correlated inversely with age in the entire population and in both subgroups. Cardiac output also correlated closely with renal blood flow in all subjects (r = 0.45, p less than 0.001). Circulating norepinephrine levels increased with age (r = 0.25, p less than 0.05), whereas epinephrine concentration tended to decrease. Plasma and total blood volume correlated directly with cardiac output (r = 0.39, p less than 0.001) and inversely with peripheral resistance (r = -0.34, p less than 0.001). These data indicate that the hyperdynamic circulation (high cardiac output and renal blood flow) of borderline hypertension is found predominantly in patients younger than age 30 years. Older patients are characterized by an elevated total peripheral resistance and normal cardiac output. The age-dependent increase in circulating norepinephrine and decrease in epinephrine levels may participate in the shift of the hemodynamic profile from high-cardiac-output hypertension in the young to a high-arteriolar-resistance hypertension in the older patient.

Adolescent↗
PubMed1981

Patterns of left ventricular adaptation in borderline and mild essential hypertension. Echocardiographic findings.

To assess patterns of left ventricular adaptation, 38 patients with borderline and 38 with sustained mild essential hypertension, all lacking electrocardiographic and roentgenographic criteria for left ventricular hypertrophy, were compared using systemic hemodynamic values and M-mode echocardiograms. All patients had normal left ventricular function and measurements of wall thickness. Those with borderline hypertension showed no asymmetric increase in the ratio of septal to posterior wall thickness. The ratio of the left ventricular radius to wall thickness remained normal in both groups, indicating no disproportionate hypertrophy or dilatation of chambers during the phase of normal left ventricular function. Neither finding substantiates asymmetric septal hypertrophy in early hypertension. Those with mild essential hypertension demonstrated an augmented mean circumferential fiber shortening rate compared to those with borderline hypertension (P less than 0.005), suggesting an early stage of left ventricular hyperfunction in the development and elaboration of hypertensive heart disease.

Adult↗
PubMed1981

Non-invasive cardiovascular assessment of indapamide in patients with essential hypertension.

The antihypertensive effect and a non-invasive cardiovascular assessment of indapamide in patients with idiopathic hypertension have been investigated in an uncontrolled study. Indapamide was found to be an effective antihypertensive agent in a dose of 2.5 mg per day with a mean fall in blood pressure of 25/18 mmHg. Apart from the development of impotence in one patient, no side effects were encountered. Its effect on heart rate and cardiac output suggest that vasodilatation may contribute to its mode of action. Exercise performance is well maintained and cardiac performance appears to improve when blood pressure is lowered with this drug.

Adult↗
PubMed1980

Effect of blood pressure control on left ventricular hypertrophy in patients with essential hypertension.

1. Changes in left ventricular structure and function were assessed by echocardiography in 22 patients before and after 9 months blood pressure control. 2. Nine patients had normal baseline echocardiograms (group 1) and 13 had echocardiographic evidence of left ventricular hypertrophy (group 2). 3. Group 2 patients demonstrated significant reductions in posterior wall thickness (P < 0.01), septal wall thickness (P < 0.025) and left ventricular mass (P < 0.005). Only six of the 13 patients showed a reduction of greater than or equal to 3 mm in posterior wall thickness. The remainder showed no alteration or only a slight non-significant reduction. 4. The regression of voltage in some patients but not in others did not appear to be related to initial blood pressure, the extent of the fall in blood pressure or duration of follow-up. It was not possible to say whether any specific therapy was beneficial to regression since most of the patients were on multiple therapy.

Adult↗