Biomedical subjects

F G Dunn

Publications and source records attributed to F G Dunn.

At least 91 records · Page 5Linked to original sources

PubMed1984

Enalapril improves systemic and renal hemodynamics and allows regression of left ventricular mass in essential hypertension.

Enalapril, a new angiotensin-converting enzyme inhibitor, is an effective antihypertensive agent for both renovascular and essential hypertension. It is structurally different from captopril in that it does not possess a sulfhydryl group. The systemic and renal hemodynamic, biochemical and cardiac adaptive changes induced by enalapril were studied in 8 patients with essential hypertension before and after 12 weeks of therapy. Mean arterial pressure decreased from 110 to 90 mm Hg (p less than 0.01), and this was mediated through a decrease in total peripheral resistance from 42 +/- 3 to 32 +/- 3 U (p less than 0.01). Cardiac index and heart rate did not change. Renal plasma flow was increased in 6 of 8 patients and renal vascular resistance decreased from 123 +/- 6 to 91 +/- 7 U (p less than 0.001). Left ventricular mass index decreased from a mean of 166 +/- 29 to 117 +/- 8 g/m2 (p less than 0.05) without impaired myocardial contractility. Thus, enalapril lowers arterial pressure by reducing total peripheral resistance without reflexive cardiac effects. It also has favorable hemodynamic effects on the kidney. This is the first report of regression of LV mass with this agent in man.

Adult↗

PubMed1984

Impaired systemic arterial compliance in borderline hypertension.

Arterial compliance was evaluated by pulse wave velocity, pulse pressure/stroke volume, and by an exponential analysis of the diastolic blood pressure decay curve in three groups of normotensive, borderline hypertensive, and established essential hypertensive patients. Two of the above three indices reflected significantly impaired arterial compliance in borderline hypertension, and all three indices were distinctly abnormal in patients with established hypertension. A close correlation among the three indices was observed in the entire study population. Multiple regression analysis indicated that age (p less than 0.005), systolic (p less than 0.005) and diastolic (p less than 0.025) pressure were independent determinants of pulse wave velocity; other factors such as total peripheral resistance, pulse pressure, and stroke volume were not. We conclude that arterial compliance becomes impaired early in hypertensive cardiovascular disease at the time when arterial pressure may be only slightly elevated. Thus structural alteration of the arterial wall can be demonstrated in borderline hypertension. Age, systolic and, to a lesser degree, diastolic pressures are the best determinants of arterial compliance in large vessels and are therefore important risk factors for evolving systemic arterial disease in essential hypertension.

Adult↗

PubMed1984

Hypertension and sudden death. Increased ventricular ectopic activity in left ventricular hypertrophy.

The present study was designed to detect and quantify cardiac arrhythmias in hypertensive patients with left ventricular hypertrophy. Continuous ambulatory electrocardiographic tracings and arterial pressure were recorded for 24 hours in 14 normotensive subjects, 10 patients with established essential hypertension without left ventricular hypertrophy, and 16 hypertensive patients with left ventricular hypertrophy by electrocardiographic criteria. Urinary excretion of norepinephrine was simultaneously measured over four successive four-hour and one eight-hour period. Patients with left ventricular hypertrophy had significantly more ventricular (but not atrial) premature contractions than those without left ventricular hypertrophy or than normotensive subjects. Five patients with left ventricular hypertrophy had episodes of more than 30 premature ventricular contractions per minute. Higher-grade ventricular ectopic activity such as coupled premature ventricular contractions was seen in two, and multifocal premature ventricular contractions were seen in three in the group with left ventricular hypertrophy. No difference in urinary catecholamine excretion rates among the three groups was seen. Left ventricular hypertrophy has been shown to be an independent risk factor for sudden death and acute myocardial infarction. Electrocardiographic monitoring of patients with left ventricular hypertrophy allows identification of those who have the highest risk and, therefore, require the most aggressive therapeutic intervention.

Adult↗

PubMed1984

Diurnal variation of blood pressure in elderly patients with essential hypertension.

Twenty-one elderly patients with essential hypertension, all over 65 years of age, were subjected to automated noninvasive 24-hour blood pressure measurement. Readings were obtained every 7.5 minutes throughout the day. The data were analyzed with respect to: correlation between office and ambulatory pressure measurements; possible differences in the circadian blood pressure pattern; and the existence of hypertensive or atherosclerotic cardiovascular complications. In all patients, the office systolic pressures were significantly higher than the ambulatory daytime pressures; diastolic pressures were similar. At night, two patterns of blood pressure emerged. In one there was a further fall in both systolic and diastolic pressures to normotensive levels, whereas the other pattern revealed no change in diastolic pressure, although systolic pressure increased significantly to similar levels as measured in the office. The prevalence of hypertensive or atherosclerotic cardiovascular complications in the patients with the first pattern was significantly less than in the group of patients with the second pattern (chi square, P less than 0.025). The data reported herein indicate that ambulatory blood pressure monitoring may help in the overall clinical evaluation of elderly patients with hypertension.

Aged↗

PubMed1984

Immediate hemodynamic effects of a dopamine-receptor agonist (fenoldopam) in patients with essential hypertension.

Systemic, splanchnic, and renal hemodynamics, intravascular volume, and reflexive and endocrine changes were measured before and after a single dose of fenoldopam, a novel antihypertensive agent that acts through stimulation of specific dopamine receptors. A 13% reduction in mean arterial pressure was mediated by a fall in total peripheral resistance association with an increase in cardiac index, heart rate, stroke volume, left ventricular ejection rate, and circumferential fiber shortening. Renal blood flow increased, thereby reducing the renal vascular resistance by more than 40%. In contrast, splanchnic hemodynamics failed to change. Likewise, there were no changes in intravascular volume, plasma renin activity, or norepinephrine, serum aldosterone, or prolactin levels.

Administration, Oral↗

PubMed1984

Hypertensive heart disease in the patient with a normal electrocardiogram and chest radiograph.

Epidemiological studies in recent years have demonstrated the prognostic implications of cardiac involvement in patients with essential hypertension. Thus, all the major complications of this disorder are increased when left ventricular hypertrophy (LVH), as measured by the electrocardiogram (ECG), is present. However, both the ECG and the chest radiograph lack sensitivity in the diagnosis of LVH and cannot provide necessary information regarding cardiac function and perfusion. The development of techniques such as echocardiography has permitted an assessment of cardiac structure and function by noninvasive means early in the development of cardiac adaptation to hypertension. Echocardiography is more sensitive than either the ECG or chest radiograph in the diagnosis of LVH and can also provide information on altered cardiac function even before LVH is present. This earlier detection of cardiac involvement in hypertension is likely to have both prognostic and therapeutic implications and therefore should be considered as part of the baseline assessment of all patients with sustained elevation of arterial pressure.

Cardiomegaly↗

PubMed1984

Systemic and renal effects of enalapril and its effects on cardiac mass.

Enalapril is a new angiotensin converting enzyme (ACE) inhibitor and has been shown to be of benefit in the treatment of both renovascular and essential hypertension. We have studied the systemic and renal haemodynamic, biochemical and cardiac adaptive changes induced by this agent in eight patients with essential hypertension before and after 12 weeks of therapy. Mean arterial pressure fell from 110 to 90 mmHg (P less than 0.01) and this was mediated through a fall in total peripheral resistance, cardiac index and heart rate remaining unchanged. Renal plasma flow rose in six patients. Renal vascular resistance fell in all patients (P less than 0.01). Left ventricular mass index was reduced from a mean of 166 +/- 29 to 117 +/- 8 g/m2 (P less than 0.05) and systolic ventricular function remained unchanged. Thus, enalapril lowers arterial pressure by reducing total peripheral resistance, has favourable haemodynamic effects on the kidney, and produces a reduction in left ventricular mass within three months of the start of therapy.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1984

Clinical and hemodynamic determinants of left ventricular dimensions.

This study was designed to quantitate the influence of 20 clinical, hemodynamic, and volume determinants of left ventricular (LV) structure. Systemic hemodynamics, intravascular volume, and LV echocardiographic measurements were collected in a heterogeneous population of 171 patients. Stepwise multiple-regression analysis indicated that body weight and body-surface area were the most powerful determinants of LV chamber size, wall thickness, and muscle mass. Age, a pressure independent determinant of myocardial mass, had no influence on chamber size or LV function. Arterial pressure correlated best with the relative wall thickness and chamber volume. Intravascular volume was a major discriminator for chamber volume, LV mass, and velocity of circumferential fiber shortening. It is concluded that body weight, arterial pressure, intravascular volume, and age are each independent determinants of the LV dimension. Systolic pressure most closely correlated with relative wall thickness and thereby is the best predictor of degree of concentric LV hypertrophy.

Adolescent↗

PubMed1984

Greater renal vascular involvement in the black patient with essential hypertension. A comparison of systemic and renal hemodynamics in black and white patients.

Systemic, splanchnic, and renal hemodynamic data were derived from 60 male and female, black and white, untreated and uncomplicated patients with essential hypertension. The systemic hemodynamic data confirmed our previous findings that at any level of arterial pressure, when black and white patients are matched for age, sex, and mean arterial pressure, cardiac index and total peripheral resistance were similar. This suggests that hypertensive vascular disease is no more severe in the black. This concept was supported further with respect to the splanchnic vasculature; however, renal blood flow was less and renal vascular resistance was higher at any level of mean arterial pressure (or total peripheral resistance) in the black. These physiological findings lend credence to those reports suggesting that at any level of pressure, hypertensive disease and morbidity (e.g., renal impairment) are more severe in the black patient. In addition, these data underscore the importance of understanding regional circulatory characteristics and they do not necessarily follow pari passu measured indices of systemic hemodynamics.

Black People↗

PubMed1984

Stable red cell mass despite contracted plasma volume in men with essential hypertension.

Red blood cell mass, plasma volume, and renal and systemic hemodynamic measurements were evaluated in 24 normotensive men (group 1), 45 men with mild essential hypertension (group 2), and 43 men with moderate to severe essential hypertension (group 3). Despite significant hemodynamic differences between the groups and although plasma volume was contracted, the increased hematocrit in the third group of patients was not explained by an increase in red blood cell mass. Because this was the case in all groups, it demonstrates that the increased hematocrit in patients with more severe essential hypertension is solely attributable to the contracted plasma volume.

Adult↗

PubMed1983

Essential hypertension in the elderly: haemodynamics, intravascular volume, plasma renin activity, and circulating catecholamine levels.

In an attempt to dissociate the cardiovascular adaptations to high blood pressure from those of ageing, 30 patients with established essential hypertension aged over 65 years were matched for mean arterial pressure, race, sex, height, and weight with 30 patients younger than 42 years. Cardiac output, heart rate, stroke volume, intravascular volume, renal blood flow, and plasma renin activity were significantly lower in the elderly, whereas total peripheral (and renal vascular) resistance, left ventricular posterior wall and septal thicknesses, and left ventricular mass were higher. Intravascular volume correlated inversely with total peripheral resistance in both groups and in all patients. Pathophysiological findings of essential hypertension in the elderly are characterised by a hypertrophied heart of the concentric type with a low cardiac output resulting from a smaller stroke volume and a slower heart rate. Renal blood flow is disproportionally reduced and total peripheral and renal vascular resistance elevated.

Adult↗

PubMed1983

Pharmacologic and physiologic considerations of adrenoceptor blockade.

The beta-adrenergic receptor blocking drugs have been in use for the treatment of hypertension for almost two decades. Although the mechanism of their antihypertensive action still is not precisely known, they have become an established major class of therapy for the disease. Most agents produce an immediate reduction in heart rate and cardiac output, later followed by a reduction in pressure. The exceptions include: those agents that possess intrinsic sympathomimetic activity and produce little reduction in heart rate and output; and labetalol, an agent that reduces pressure immediately (associated with the cardiac effects) because it possesses alpha- as well as beta-adrenoceptor blocking effects. Just because a beta-blocking drug reduces cardiac output significantly, it does not follow that renal blood flow will decrease; this depends upon the number and affinity of receptors in the renal circulation. Most beta blockers (including labetalol) reduce renal vascular resistance in patients with uncomplicated hypertension. Other actions of this class of adrenoceptor blocking agents are discussed. As we learn more of the physiologic effects of adrenoceptor blocking agents, there is no doubt that we shall gain more insight into the underlying mechanisms of hypertensive diseases as well as their pharmacologic properties.

Adrenergic beta-Antagonists↗

PubMed1983

Management of coronary artery disease in patients with hypertensive left ventricular hypertrophy.

An appreciation of the cardiac effects of antihypertensive drugs and important pharmacologic advances in the past 10 years have permitted a more rational approach to the management of the patient with both coronary artery disease and hypertensive left ventricular hypertrophy. Since this is a particularly high-risk group of patients, early detection and optimal management of ischemic symptoms and hypertension are necessary. Beta-blocking agents are ideal agents (in the absence of heart failure) since their efficacy has been proved in both coronary artery disease and hypertension. Similarly, calcium slow-channel blocking agents have both antianginal and antihypertensive properties. When arterial pressure reduction is needed quickly, caution is required in the choice of an agent since adverse reflexive cardiac effects may occur, particularly with pure arteriolar dilators. If a diuretic is required, serum potassium levels should be carefully monitored since both coronary artery disease and left ventricular hypertrophy already increase the risk of life-threatening dysrhythmias. The decrease in mortality from coronary heart disease seen in the past 10 years is likely to be further improved by specific attention to management of such high-risk groups as those with associated hypertensive left ventricular hypertrophy.

Adrenergic beta-Antagonists↗

PubMed1983

Immediate hemodynamic effects of a new calcium-channel blocking agent (nitrendipine) in essential hypertension.

The immediate hemodynamic effects of a new calcium-channel blocking agent nitrendipine were studied in 12 patients with mild established essential hypertension. According to the response to mean arterial pressure, patients were classified into responders (decrease greater than 10 mm Hg, 7 patients) and nonresponders (less than or equal to 10 mm Hg, 5 patients). The decrease in arterial pressure in responders was associated with a significant (p less than 0.01) decrease in total peripheral resistance and a significant (p less than 0.05) increase in heart rate, cardiac index, and left ventricular ejection rate. The plasma norepinephrine level was significantly (p less than 0.05) increased in the responders. The response to upright tilt was qualitatively similar to pretreatment values. Thus, nitrendipine lowered arterial pressure as a result of arteriolar dilatation associated with a reflexive increase in heart rate and cardiac index. These hemodynamic properties make the drug particularly apt for use in combination with beta-adrenergic blockade for the treatment of arterial hypertension.

Adult↗

PubMed1983

Disparate cardiovascular effects of obesity and arterial hypertension.

Since obesity and essential hypertension frequently coexist, a study was designed to analyze some of their cardiovascular effects. Twenty-eight obese patients, half of whom were normotensive and half with established hypertension, were matched for mean arterial pressure with 28 corresponding lean subjects. Systemic and renal hemodynamics, intravascular volume, plasma renin activity, and circulating catecholamine levels were measured. Obese patients had increased cardiac output (p less than 0.001), stroke volume (p less than 0.001), central blood volume (p less than 0.02), plasma and total blood volume (p less than 0.01), and decreased total peripheral resistance (p less than 0.001). In contrast, cardiac output, central blood volume, and stroke volume of hypertensive patients were normal, but they had increased total peripheral (p less than 0.001) and renal vascular resistance (p less than 0.001) and a contracted intravascular volume. Left ventricular stroke work was elevated to a similar level in obesity (p less than 0.001) and hypertension (p less than 0.02), but the increase was caused by an expanded stroke volume in the former and by an increase in systolic pressure in the latter. It is concluded that the disparate effects of obesity and hypertension on total peripheral resistance and intravascular volume counteract and may even offset each other. Thus, obesity may mitigate the effects of chronically elevated total peripheral resistance (and therefore end-organ damage) in essential hypertension. Since both entities affect the heart through different mechanisms, their presence in the same patient results in a double burden to the left ventricle, thereby gently enhancing the long-term risk of congestive failure.

Adult↗

PubMed1983

Hypertension and myocardial infarction.

Because hypertension and myocardial infarction are closely linked in several ways, a better understanding of this relation leads to more effective prophylaxis and management. Management should be directed at three different areas: 1) the prevention of a first myocardial infarction, 2) the prevention of complications after an infarction, and 3) the management of hypertension during evolution of an acute infarction. There is good evidence that beta-receptor blocking agents are beneficial to long-term management. When therapy is required in the acute situation, arteriolar vasodilators are to be avoided and combined arteriolar/venular dilators are the drugs of choice.

Antihypertensive Agents↗

PubMed1983

Racial differences in cardiac adaptation to essential hypertension determined by echocardiographic indexes.

Epidemiologic data point to racial differences in cardiac adaptation to hypertension. In this study, echocardiography and measurement of systemic hemodynamics were performed in 30 black and 30 white patients with untreated essential hypertension. Each black patient was matched with a white patient for age, sex and mean arterial pressure. Wall thickness measurements were similar, but left ventricular mass index was significantly increased in blacks (probability [p] less than 0.05). There was a nonsignificant increase in the number of black patients with posterior wall thickness greater than 1.1 cm. Only in black patients was posterior wall thickness related to systolic (r = 0.45; p = 0.008) and diastolic (r = 0.44; p = 0.0042) pressure and to total peripheral resistance (r = 0.32; p less than 0.046). Thus, although ventricular wall thickness changes are similar in black and white patients, qualitative differences exist in the cardiac adaptive process to systemic hypertension.

Adaptation, Physiological↗

PubMed1983

Hemodynamic effects of intravenous labetalol in essential hypertension.

Labetalol inhibits alpha- and beta-adrenergic receptors. Systemic and regional hemodynamic alterations after intravenous labetalol and its cardiovascular reflexive and metabolic effects were evaluated in 12 subjects with mild to moderately severe essential hypertension. Supine systolic, diastolic, and mean pressures were reduced (from 180/101 and 125 to 149/86 and 109 mm Hg; P less than 0.001). The fall was accentuated during head-up tilt and was accompanied by decreased cardiac output and central blood volume in subjects in both the supine and tilted positions. Neither heart rate nor total peripheral resistance was changed by labetalol, suggesting that venodilation resulting from alpha-adrenergic-receptor inhibition played an important role in arterial pressure reduction.

Adult↗