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Biomedical subjects

G A MacGregor

Publications and source records attributed to G A MacGregor.

At least 73 records · Page 4Linked to original sources
PubMed1998

High prevalence of carotid artery disease in patients with atheromatous renal artery stenosis.

BACKGROUND: Renovascular disease is the most frequently encountered secondary cause of hypertension and is one of the few potentially reversible causes of chronic renal failure. These patients are at increased risk of having cerebrovascular events following operative management for atheromatous renal-artery stenosis. We studied the prevalence of carotid-artery disease in patients with atheromatous renal-artery stenosis. METHODS: A cross-sectional study was carried out on 38 consecutive patients with atheromatous renal-artery stenosis who underwent renal-artery balloon angioplasty. Extracranial carotid atherosclerosis was assessed using a commercially available colour Doppler scanner, depending on the velocity of the peak systolic waveform in the internal carotid artery, and the internal carotid-artery/common carotid-artery ratio. RESULTS: Twenty-one patients (55.3%) had normal or mild carotid-artery disease, 10 (26.3%) had moderate, and 7 (18.4%) had severe carotid-artery disease. Nine patients had previously suffered a stroke (eight infarction, one haemorrhage) and one had multiple transient ischaemic attacks. CONCLUSIONS: Our results suggest that, in patients with atheromatous renal-artery disease severe enough to require angioplasty, 4 out of 10 appear to have moderate to severe carotid-artery disease. This may explain the increased prevalence of atherothrombotic cerebrovascular events in these patients, and also previous observations that, following operative management for atheromatous renal-artery stenosis, some patients had developed an acute or late cerebrovascular event. We suggest therefore that such patients should always be regarded as having generalized vascular disease not confined to one system, and need to be assessed for carotid-artery disease prior to operative management for atheromatous renal-artery stenosis.

Aged↗
PubMed1998

The use of HMG Co-A reductase inhibitors following acute myocardial infarction in hospital practice.

Treatment with a HMG-CoA reductase inhibitor (statin) following a myocardial infarction has been shown to reduce the incidence of subsequent coronary revascularisation, myocardial infarction and cardiovascular death. The majority (89%) of patients admitted to the coronary care unit of our hospital received a fasting cholesterol check as part of a routine coronary care unit protocol. However, our survey shows that only 26% of patients surviving an acute myocardial infarction were on treatment with a statin at follow-up. Furthermore, those receiving statins were given smaller doses than those used in clinical trials. One way to ensure patients receive adequate treatment with statins, may be to include it as part of a coronary care unit protocol.

Aged↗
PubMed1998

Contrasting endocrine responses to acute oral compared with intravenous sodium loading in normal humans.

There is evidence in animals and in humans for accelerated natriuresis after oral compared with intravenous sodium loading. To assess the role of atrial natriuretic peptide (ANP) as a contributory mechanism, we compared the hormonal responses to an intravenous sodium load and to the same sodium load taken orally in three separate groups of healthy subjects in balance on low, normal, or high sodium intake. On each diet, there was a trend for an early delay in sodium excretion, followed by increased natriuresis after the oral compared with intravenous sodium load. On all levels of dietary sodium intake, there was a significant (approximately 2-fold) increase in plasma ANP levels after intravenous saline infusion. There was a significant suppression of the renin system both after oral and intravenous sodium loading. However, there was no acute increase in plasma ANP levels after the oral sodium load, except on the very low sodium intake. This striking and unexpected observation suggests that changes in plasma ANP levels appear to play little role in the early response to an acute oral sodium load in subjects with sodium intake in the range of 150-350 mmol/day. Endocrine mechanisms for the accelerated increase in sodium excretion after oral compared with intravenous sodium loading remain to be elucidated.

Adult↗
PubMed1998

Importance of the renin system in determining blood pressure fall with salt restriction in black and white hypertensives.

Seventy-one white and 33 black patients with essential hypertension were studied while on a high sodium intake of 350 mmol/d for 5 days and low sodium intake of 10 mmol/d for 5 days. The fall in blood pressure on changing from the high sodium to the low sodium diet was 17/6 mm Hg in whites and 22/10 mm Hg in blacks. Compared with whites, black patients had a 7-mm Hg greater fall (P<0.05) in systolic blood pressure and 4-mm Hg greater fall (P=0.068) in diastolic blood pressure (adjusted for age and blood pressure on the normal diet) with similar changes in urinary sodium excretion. With sodium restriction, plasma renin activity rose from 0.65 to 3.03 ng. mL-1. h-1 in whites, whereas in blacks it rose only from 0.3 to 1.28 ng. mL-1. h-1 (P<0.001 between blacks and whites). From the high to the low salt diet, plasma angiotensin II increased by 31 pmol/L in whites and by 12 pmol/L in blacks (P<0.05 compared with whites), and plasma aldosterone rose by 499 pmol/L in whites and by 256 pmol/L in blacks (P<0.01). Significant inverse correlations were obtained for all patients between the fall in systolic blood pressure from the high to low salt diet and the rise in plasma renin activity and angiotensin II, as well as the absolute level on the low salt diet. These results demonstrate that the larger fall in blood pressure with a reduction in salt intake in blacks is due at least in part to a less responsive renin-angiotensin-aldosterone system in blacks.

Adult↗
PubMed1998

Some similarities and differences between verapamil and the dihydropyridines.

GROUPS OF CALCIUM CHANNEL BLOCKERS: The calcium channel blockers comprise a heterogeneous group of drugs. From both pharmacological and clinical points of view, they can be divided into three groups: the dihydropyridines, the phenylalkylamines and the benzothiazepines. REASONS FOR DIFFERENCES: There are important clinical and functional differences between the three groups. This may be explained by the fact that these families bind at different sites to the calcium channel. In this review, the major differences between the three groups are discussed, with an emphasis on verapamil.

Antihypertensive Agents↗
PubMed1997

Double-blind randomised trial of modest salt restriction in older people.

BACKGROUND: Stroke is directly related to blood pressure and treatment trials in older hypertensive individuals show a reduction in strokes. However, the majority of strokes occur in normotensive individuals in whom no attempt is made to lower blood pressure. We compared the effects of modest salt restriction on blood pressure in older hypertensive and normotensive people. METHODS: 47 untreated elderly people (24 men, age range 60-78 years; blood-pressure range 123-205 mm Hg systolic and 64-112 mm Hg diastolic) completed a 2-month double-blind randomised placebo-controlled crossover study of modest salt restriction with slow sodium and placebo to give a salt intake of either 10 g (equivalent to the normal amount for the UK population) or 5 g. FINDINGS: On the normal salt intake for the UK population, supine blood pressure was 163/90 (SD 21/10) mm Hg with urinary sodium excretion of 177 (49) mmol/day. With modest sodium restriction, blood pressure fell to 156/87 (22/9) mm Hg (p < 0.001/0.004) with a urinary sodium excretion of 94 (50) mmol/day. A reduction in sodium intake of 83 mmol/day was associated with a reduction of 7.2/3.2 mm Hg. There was no significant difference in the blood-pressure fall between 18 normotensive and 29 hypertensive participants (8.2/3.9 vs 6.6/2.7 mm Hg). INTERPRETATION: A modest reduction in salt intake leads to a fall in blood pressure in both normotensive and hypertensive older people similar to that in outcome trials of thiazide-based treatment. Since the majority of strokes in older people occur below the current definition of hypertension, our results have important implications for the prevention of stroke.

Aged↗
PubMed1997

The use of angiotensin-converting enzyme inhibitors in the treatment of heart failure in hospital practice.

Several well-controlled trials in patients with heart failure have shown that the use of angiotensin-converting enzyme (ACE) inhibitors, in combination with a diuretic, causes a reduction in mortality and morbidity, which seems to be mainly due to a reduction in fatal and nonfatal cardiovascular events. Our aim was to determine whether 249 consecutive patients discharged from hospital with a primary diagnosis of heart failure were routinely being treated with an ACE inhibitor at an appropriate dose. At the time of admission to hospital, 91 (36.5%) were receiving a combination of a diuretic and an ACE inhibitor, 129 (51.8%) were receiving a diuretic alone, and 29 (11.6%) had not previously received either a diuretic or an ACE inhibitor. At the time of discharge from hospital all patients were on a diuretic and 144 (57.8%) were also receiving an ACE inhibitor. Although 41 patients (16.5%) had a relative or absolute contraindication for the use of an ACE inhibitor, 64 patients (25.7%) with no contraindication were not receiving an ACE inhibitor. Many of the patients who were prescribed an ACE inhibitor were given it at an inappropriate dose; only 24 patients (16.7%) were on the dose that was used in the clinical trials showing a reduction in mortality. These results show that in one in four patients admitted to hospital with heart failure who should be receiving an ACE inhibitor by the time of discharge, are not. The average age of these patients was 76 years. Whilst it has been shown that the benefit of ACE inhibitors does not appear to be age-related, most published studies have not included many patients over the age of 80. Specific studies looking at the effect of ACE inhibitors in elderly patients would be helpful, as well as studies to determine the optimum treatment regimen for this age group.

Aged↗
PubMed1997

Salt--more adverse effects.

Salt intake has been shown to be the most important determinant of blood pressure differences both between populations and within populations, as well as the main determinant of the rise in blood pressure with increasing age. In spite of this overwhelming evidence, the food industry for commercial reasons has sustained an artificial debate about the importance of salt intake. This has distracted attention from the other serious effects that a high salt intake may have. A high salt intake (a) exacerbates conditions where there is already sodium and water retention; (b) is the rate limiting factor for carcinoma of the stomach; (c) contributes to left ventricular hypertrophy; (d) is likely to hasten deterioration of renal function and renal disease; (e) is an exacerbating factor in asthma; and (f) increasingly is suggested as a major aggravating factor in osteoporosis.

Animals↗