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Biomedical subjects

J D Spence

Publications and source records attributed to J D Spence.

At least 109 records · Page 6Linked to original sources
PubMed1985

Blood pressure measurement in the elderly: correlation of arterial stiffness with difference between intra-arterial and cuff pressures.

Intra-arterial (radial) blood pressure (BP) measurement was compared with the indirect cuff method in 55 healthy volunteers aged from 59-80 years (mean 68.6 +/- 5.2 s.d.). On average, the cuff method underestimated systolic BP by 5 mmHg and overestimated diastolic BP by 8 mmHg. Cuff measurement underestimated systolic BP by greater than 10 mmHg in 17 cases, and by greater than 20 mmHg in three cases. The cuff method overestimated diastolic BP by greater than 10 mmHg in nine cases (one greater than 20 mmHg) and in two cases the cuff overestimated diastolic BP by greater than 30 mmHg, compared with intra-arterial pressures. The differences correlated with pulse wave velocity, an index of arterial stiffness. A pulse wave velocity index reflecting the entire length from the aortic root to the posterior tibial artery (PWVI/ao-pt) gave a correlation (r) of 0.48 (P less than 0.0005) with systolic arterial/cuff (A/C) difference, a correlation of 0.43 (P less than 0.001) with diastolic A/C difference, and a correlation of 0.57 (P less than 0.00001) with the A/C difference in measurement of mean arterial pressure. A positive but weaker correlation was observed between A/C difference and PWVI aorta-femoral. Although the pressure differences were not as great in these healthy elderly subjects as in previous studies of patients suspected of having pseudo-hypertension, caution still appears to be indicated in the interpretation of cuff blood pressure measurement in the elderly.

Aged↗
PubMed1985

Effects of antihypertensive drugs on atherogenic factors: possible importance of drug selection in prevention of atherosclerosis.

The treatment of hypertension is clearly beneficial. Blood pressure reduction with antihypertensive drugs reduces mortality and the incidence of complications such as stroke, renal failure, and congestive failure. However, analysis of long-term studies using different antihypertensive drugs indicates that the outcome of patients treated in those studies may be determined by effects of the antihypertensive drugs other than the lowering of blood pressure. Evidence is increasing that certain antihypertensive drugs have adverse effects on plasma lipid profiles that are of sufficient magnitude to offset the benefit of antihypertensive treatment in mild hypertensives. Furthermore, the effects of antihypertensive drugs on arterial flow disturbances, although they have received scant attention until now, may be important in the progression of atherosclerosis or even in the primary prevention of atherosclerosis. This article highlights differences in the effects of antihypertensive drugs on plasma lipids and on arterial flow disturbances as they may pertain to prevention of atherosclerosis.

Antihypertensive Agents↗
PubMed1984

Increased prevalence of mitral valve prolapse in patients with migraine.

Patients with classic migraine (69 women and 31 men) selected randomly from a practice list of over 1000 were matched for age, sex and neighbourhood with 100 people who did not have headache problems, and both groups underwent M-mode and two-dimensional echocardiography and clinical examination by cardiologists blinded to the subjects' clinical status. The mean ages were 34.9 +/- 11.3 years for the migraine group and 33.1 +/- 9.9 years for the control group. Definite and possible mitral valve prolapse (MVP), diagnosed according to predefined echocardiographic criteria, were found about twice as often in the migraine group as in the control group (in 15 v. 7 and 16 v. 8 patients respectively); the echocardiograms were definitely normal in 69 migraine patients and 85 controls (chi 2 = 8.39, p less than 0.025). Altogether 25% of the migraine group and 11% of the control group had evidence of MVP from a combination of the echocardiographic and auscultatory findings (chi 2 = 5.72, p less than 0.025). The odds ratio was 2.7, with 95% confidence limits of 1.17 and 6.29. The association between migraine and MVP has implications for the understanding of platelet abnormalities and episodes of cerebral ischemia occurring in both these conditions.

Adult↗
PubMed1984

Hemodynamic modification of aortic atherosclerosis. Effects of propranolol vs hydralazine in hypertensive hyperlipidemic rabbits.

According to hemodynamic theories of atherogenesis, atherosclerotic plaques are a reaction to endothelial damage caused by arterial flow disturbances such as turbulence. Earlier studies showed that hydralazine increased, whereas propranolol decreased, the product of heart rate X blood velocity, a predictor of arterial flow disturbances, and that hydralazine aggravated, whereas propranolol decreased turbulence in the region of carotid artery stenosis. This study was done to test the hypothesis that drugs which reduce arterial flow disturbances may be more effective in preventing atherosclerosis, than antihypertensive drugs which worsen arterial flow disturbances. Eighty-three New Zealand white rabbits were made hypertensive by a one-kidney Goldblatt procedure, and were fed a 1% cholesterol diet. Untreated hypertensive (P less than 0.01) and hydralazine-treated hypertensive rabbits (P less than 0.05) had significantly more atherosclerosis than did the normotensive controls; propranolol-treated rabbits did not differ significantly from the normotensive controls. Analysis of covariance showed that propranolol-treated rabbits had significantly less atherosclerosis than hydralazine-treated rabbits with blood pressure (P less than 0.04) or heart rate (P less than 0.006) as the covariates.

Animals↗
PubMed1984

Potassium-sparing diuretics: interaction with digoxin in elderly men.

The effects of two potassium-sparing diuretic combination drugs, triamterene-hydrochlorothiazide and spironolactone-hydrochlorothiazide, were compared with those of two kaliuretic diuretics, hydrochlorothiazide and furosemide, in order to ascertain the effects of those diuretics on concentrations of serum digoxin, serum potassium, and erythrocyte potassium, and to determine whether any of these diuretics should be preferred for patients taking digoxin. It was concluded that in patients for whom potassium depletion may lead to digoxin toxicity, a potassium-sparing diuretic may safely be used in order to reduce potassium excretion and thereby reduce the risk of arrhythmias.

Aged↗
PubMed1983

Effects of hydralazine versus propranolol on blood velocity patterns in patients with carotid stenosis.

1. Since endothelial damage due to flow disturbances is of postulated significance in the pathogenesis of atherosclerosis, this study examined the effects of antihypertensive drugs on carotid flow patterns in patients with known carotid stenosis. A Doppler Echoflow unit was used to display arterial velocities in red (normal range), yellow (increased velocity) and blue (abnormally increased velocity thought to represent turbulence and other departures from laminar flow). 2. Twenty patients were studied before drug, then during intravenous administration of hydralazine, 6-12 mg, and propranolol, 2-5 mg, over 10-15 min each, with return to baseline between drugs. 3. After hydralazine, the occurrence of abnormal high velocity flow patterns increased in 17 of 20 patients; there was no change in three patients. Propranolol reduced the occurrence of abnormal high velocity flow patterns in 19 of 20 patients (P less than 0.00001; chi-square). 4. These effects of antihypertensive drugs on arterial velocity patterns may be important in the selection of antihypertensive drugs to prevent or minimize the progression of atherosclerosis.

Aged↗
PubMed1983

Doppler flow maps of the carotid artery compared with the findings on angiography.

One noninvasive method of evaluating the condition of the carotid arteries is by the Echoflow Doppler device, which produces colour-coded images of the flow pattern in the arteries. Normal velocities are represented in red, accelerated flow in yellow and turbulences in blue. The authors present the results of Echoflow studies in 317 patients who also underwent cerebral angiography. Of 660 normal carotid vessels, 21 showed appreciable abnormalities on Echoflow study (false positive 3.2%). Of 87 vessels with stenosis of 50% or more, the Echoflow study showed normal flow in 26 (false negative 29.9%). The Echoflow study indicated no abnormalities in 3 of 22 patients with severe stenosis (more than 80%) (false negative 13.6%). Of nine patients with carotid occlusion, the Echoflow study gave normal findings in one (false negative 11.1%). Sensitivity was 70.1%, specificity was 96.9%, with a positive predictive accuracy of 93.9%. Sources of error include misidentification of arteries, signal attenuation (acoustic shadow), hemodynamic changes and timing of the Echoflow study relative to angiography. Combined studies with B-mode ultrasonography and spectral analysis of the Doppler signal should reduce error. These studies should not be used to replace angiography, but to help select for angiography patients for whom the study might be contraindicated because of advanced age or cardiac disease.

Carotid Artery Diseases↗
PubMed1982

Effects of antihypertensive agents on blood velocity: implications for atherogenesis.

Heart rate and blood velocity are major determinants of flow disturbances at arterial bifurcations. Since endothelial damage due to flow disturbances is thought to be significant in the pathogenesis of atherosclerosis, the effects of drugs on these parameters have to be considered in the selection of medications to prevent atherosclerosis. To determine the effects of antihypertensive drugs on heart rate and blood velocity 15 patients with hypertension were treated with placebo, hydrochlorothiazide, nadolol, propranolol and hydralazine in sequence. The doses given produced significant changes in heart rate and blood pressure, and Doppler ultrasonographic recording of aortic blood velocity showed that there were significant changes in peak blood velocity. Nadolol and propranolol produced significantly lower values of heart rate x blood velocity than placebo, hydralazine and hydrochlorothiazide.

Adult↗
PubMed1981

Diuretics and the institutional elderly: a case against routine potassium prescribing.

In 14 elderly male residents of a veterans' care complex who were receiving diuretic therapy for cardiac failure, oral potassium (K) supplements were withdrawn. Plasma and erythrocyte K levels were measured immediately before and six weeks after withdrawal of the supplements (38 mEq K daily). The controls comprised 19 elderly residents without disease and not taking drugs likely to influence K status. Study subjects and controls were receiving the same diet (average daily K content 100 mEq). After withdrawal of K supplements, the mean plasma K level fell significantly but the mean erythrocyte K level remained unchanged and did not differ from the control values. For a further six weeks after the withdrawal period, 7 subjects were treated with Aldactazide (diuretic hydrochlorothiazide plus K-sparing spironolactone). The plasma K level increased significantly but the erythrocyte K level remained unchanged. It was concluded that, in this setting, diuretic-induced hypokalemia is not necessarily accompanied by intracellular K depletion and that routine prophylaxis with K supplements or K-sparing agents is unnecessary and not without risk. Such therapy should be reserved for patients considered at special risk of K depletion because of known poor dietary intake, advanced liver disease, secondary hyperaldosteronism with renovascular hypertension, gastrointestinal losses, or nondiuretic medication known to affect K status adversely.

Aged↗
PubMed1981

Aortic atherosclerosis in hypertensive rabbits treated with anti-hypertensive agents having different effects on arterial flow disturbances. 1. Extent of surface involvement.

Hypertension may be considered a disorder of increased energy in the blood, with two components: increased pressure energy may promote arteriolar disease, whereas arterial diseases such as atherosclerosis may be more closely related to flow disturbances (turbulence, boundary layer separation, high shear, or axial stream impingement) due to increased kinetic energy. Previous studies have shown that hydralazine aggravates turbulence in stenosed carotid arteries, whereas propranolol diminishes turbulence. To assess the effect of these drugs on the progression of atherosclerosis, the drugs were administered subcutaneously to rabbits made hypertensive (one kidney Goldblatt) and hypercholesterolemic (1% cholesterol diet for 4 weeks). Appropriate controls with normal, only hypertensive and hypertensive-hypercholesterolemic untreated rabbits were employed. A total of 36 rabbits was used. The extent of the aortic surface involvement with atherosclerotic lesions was assessed by morphometric analysis of magnified photographs. Although the extent or surface involvement did not differ significantly between the untreated or treated hypertensive rabbits, there was an interesting difference in the relationship between blood pressure and extent of surface involvement. In the untreated and hydralazine treated rabbits, there was a direct correlation between increasing blood pressure and extent of lesions; in the propranolol treated group, this relationship was abolished.

Animals↗
PubMed1980

Benign intracranial hypertension without papilledema: role of 24-hour cerebrospinal fluid pressure monitoring in diagnosis and management.

Nine patients whose history suggested increased intracranial pressure (ICP), but whose funduscopic examination did not reveal papilledema, are described. Cerebrospinal fluid monitoring in seven of the cases showed abnormal pressure waves ranging from 22 to 40 mm Hg. The findings of computed tomography and isotope cisternography and the response to therapy supported the clinical diagnosis of benign intracranial hypertension (BIH). Fluorescein angiography, which was performed in five cases, was normal. None of the patients had enlargement of the blind spot; all had normal intraocular pressure. The clinical spectrum of BIH may need to be enlarged to include cases of increased ICP without clinically evident papilledema. (Neurosurgery, 7: 326-336, 1980).

Adolescent↗
PubMed1978

Pseudohypertension in the elderly.

1. Direct intra-arterial blood pressure (radial artery) has been compared with indirect blood pressures using a regular sized adult cuff and a thigh cuff, with a mercury sphygmomanometer, in 24 hypertensive patients aged 62--84 years, and in 16 hypertensive patients aged 29--59 years. 2. The patients were studied because they were suspected of having a false elevation of their indirect blood pressure, since they had diastolic pressures over 100 mmHg, without hypertensive retinopathy, cardiac hypertrophy, or nephropathy. 3. Indirect diastolic pressure was falsely elevated by 30 mmHg or more in 12 out of 24 of the subjects over age 60, and in four of the 16 of those under age 60. Pseudohypertension (indirect diastolic greater than 100 mmHg, direct diastolic greater than 90 mmHg) was present in 12 subjects over age 60 and 5 under age 60. 4. Errors in indirect measurement of blood pressure are a serious problem, particularly in the elderly. Direct intra-arterial measurement may be useful in the management of hypertension.

Adult↗
PubMed1977

Effects of antihypertensive drugs on blood velocity: implications for prevention of cerebral vascular disease.

The treatment of high blood pressure prevents death from congestive heart failure, hypertensive nephropathy, and encephalopathy, and strokes from cerebral arteriolar disease (lacunes, hemorrhage from microaneurysms). However, atherosclerosis, manifested as coronary artery disease is just as frequent a cause of death in well-controlled hypertensives as in poorly-controlled patients. Increasing evidence suggests that increased blood velocity, by causing turbulence and high shear rates at the endothelial surface of arteries, may be important in the pathogenesis of atherosclerosis. Turbulence has been observed in cerebral berry aneurysms. In order to measure the effects of antihypertensive agents on blood velocity, a new method of analysing Doppler ultrasound velocity recordings has been developed. Studies in Rhesus monkeys show the following: In doses which reduce diastolic pressure by 13-28%, propranolol decreased mean blood velocity (MV) by 17%, clonidine decreased MV by 14%, while methyldopa increased MV 12%, and hydralazine increased MV by 52%. (p less than .00001). It is hypothesized that enlargement of berry aneurysms, the progression of cerebral atherosclerosis, and embolism from carotid lesions might all be decreased by the selection of antihypertensive agents which decrease blood velocity.

Animals↗