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Biomedical subjects

H Larkin

Publications and source records attributed to H Larkin.

156 records · Page 9Linked to original sources
PubMed1980

Precordial voltage variation in the normal electrocardiogram.

Intra-individual precordial voltage variation was examined in serial 12 lead electrocardiograms (ECGs) performed at 10 minute and 24 hour intervals in sixteen young, healthy males forming two age matched groups. Significant variation was found in repeat ECGs at both periods. When precordial electrodes remained in situ between serial 10 minute recordings variation was reduced by approximately 60% We conclude that significant precordial voltage variation is present in serial electrocardiography, even when performed over the short term. Alteration in precordial electrode placement accounts for the major proportion of variation and this may be sufficiently large to interfere with the accurate interpretation of serial precordial voltage changes in an individual subject.

Adolescent↗
PubMed1980

Cardiac and haemodynamic measurements in hypertensive pregnancy.

1. Haemodynamic and left ventricular variables were determined by M-mode echocardiography in 21 normotensive and 36 hypertensive patients during the last trimester of pregnancy. 2. Blood pressure of hypertensive patients was lowered by bed rest only, or by oxprenolol or methyldopa, but remained elevated. 3. Cardiac output was raised in the last trimester of pregnancy in both normotensive and hypertensive patients. 4. Left ventricular mass was increased in normal pregnancy, but displayed an exaggerated increase in hypertensive patients. 5. Total peripheral resistance was inappropriately elevated in hypertensive pregnancy, except in the oxprenolol-treated group. 6. There ws no reduction in heart rate or cardiac output in the group treated with beta-adrenoreceptor blocking agents. These factors, in combination with normal peripheral resistance, may contribute to the improvement in foetal outcome described in maternal hypertension of pregnancy treated with oxprenolol.

Adult↗
PubMed1980

Labetalol and propranolol in mild hypertensives: comparison of blood pressure and plasma volume effects.

Labetalol administered in a small to moderate dose (first month 400 mg/day, second month average 585 mg/day) was effective in lowering blood pressure (BP) (-21/-18 mmHg, recumbent) in 11 of 13 mild essential hypertensives over an eight-week period, despite a significant (+294 ml) increase in plasma volume. The effect of propranolol (first month 160 mg/day, second month average 234 mg/day) was significantly less on both blood pressure (-9/-9 mmHg) and plasma volume (+98 ml), although the pre-propranolol BP was lower and the final BP achieved on the two medications was comparable (labetalol 147/89 mmHg, propranolol 145/89). Six patients who continued labetalol for periods of up to 14 months had persistent plasma volume expansion. Three of these, taking a higher dose of labetalol, developed resistance to the drug's antihypertensive effect. Addition of a diuretic restored antihypertensive efficacy and led to a fall in plasma volume. No such plasma volume expansion was seen in six patients who were followed on long term propranolol therapy. Some plasma volume expansion with the combined alpha- beta-adrenoceptor blocker labetalol may be appropriate to its vasodilator action. Provided this effect is not excessive, it appears not to lead to resistance to its antihypertensive action. Small to moderate doses of labetalol would, therefore, seem effective without concomitant diuretic. Such sole use of labetalol could help minimise orthostatic symptoms which can be a major side effect of combination therapy.

Adult↗
PubMed1979

Anatomical accuracy of echocardiographically assessed left ventricular wall thickness.

1. A comparison of direct measurement and M-mode echocardiography in the determination of posterior left ventricular wall thickness was performed in 26 subjects, of whom 21 underwent cardiac bypass surgery; the remainder came to necropsy. 2. In the surgical group a close correlation was demonstrated between direct measurement of posterior wall thickness and the echocardiographic end-diastolic dimension (r = 0.76, P less than 0.001). 3. The necropsy measurement of posterior wall thickness correlated with the echocardiographic end-systolic dimension (r = 0.99, P less than 0.001). 4. These findings confirm that the echocardiographic measurement of posterior wall thickness accurately reflects the anatomical dimension.

Blood Pressure↗
PubMed1979

Haemodynamic profile of angiotensin II antagonism in essential hypertensive patients.

1. The haemodynamic response to antagonistic (10 microgram min-1 kg-1) and agonistic (40 microgram min-1 kg-1) doses of saralasin was studied in young essential hypertensive patients. Blood pressure behaviour alone was thought to be inadequate to describe the response pattern. 2. Pre-saralasin setting of the renin-angiotensin axis was varied with salt intake (15 and 290 mmol of Na+/day) each for 10 days. This failed to influence blood pressure or plasma volume. 3. Antagonist blockade after low salt lowered blood pressure in three patients with the highest plasma renin values. Cardiac output rose in two of these, but it dropped in all others. 4. Decreases in cardiac output occurred with both doses of saralasin and even with suppression of the renin-angiotensin axis. This response is therefore unlikely to be due to removal of myocardial or venous angiotensin effects. 5. The renin-angiotensin system played a part in maintenance of blood pressure only with severe salt restriction and in a small proportion of cases. 6. No heart rate effect was seen with sarcalasin. 7. Blood pressure and total peripheral resistance responses were dependent on pre-(antagonist/agonist) setting, but heart rate and cardiac output were not influenced by this factor.

Adult↗
PubMed1978

Relation between prognosis and the blood pressure before and during treatment of hypertensive patients.

1. A study was conducted amongst 1247 treated hypertensive patients to determine the predictive power of untreated baseline and achieved treated blood pressures in the development of the complications of hypertension. In addition the relative importance of systolic and diastolic pressures was calculated. 2. Statistical analysis was done by calculating univariate differences in blood pressure between cases with and without complications. The higher the univariate distance, the greater the predictive power. 3. Blood pressures achieved during treatment were more important than baseline pressures for predicting stroke in both men and women, confirming the benefits of antihypertensive therapy in preventing strokes. 4. There was some evidence of prevention of myocardial infarction in men and of angina in women as a result of therapy. 5. There was no evidence to suggest that any one group of drugs, including beta-adrenoreceptor-blocking drugs and thiazides, conferred any extra benefit in preventing coronary heart disease. 6. The systolic blood pressures achieved during treatment predicted stroke better than diastolic pressure, but no consistent trends were found for coronary heart disease.

Adolescent↗
PubMedDate not supplied

Haemodynamics of hypertension in pregnancy assessed by M-mode echocardiography.

1. Echocardiographic haemodynamic and left ventricular parameters were determined in twenty-one normontensives and thirty-six hypertensives during the last trimester of pregnancy. 2. Equivalent blood pressure control was obtained in hypertensives with bet rest only, oxprenolol or methyldopa, but remained above normotensive levels. 3. Cardiac output was elevated in the last trimester of pregnancy in normotensivves and hypertensives. 4. Left ventricular mass was increased in normal pregnancy, but displayed an exaggerated increase in hypertensives. 5. Total peripheral resistance was inappropriately elevated in hypertensive pregnancy, but was normalized in the oxprenolol-treated group. 6. There was no reduction in heart rate or cardiac output in the beta-adrenoreceptor blocker-treated group. This feature, in combination with lowered peripheral resistance, may contribute to the improvement in foetal outcome observed in maternal hypertension of pregnancy treated with oxprenolol.

Adrenergic beta-Antagonists↗