Cardiac vagal activity: a target for intervention in heart disease.
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Animals↗
Biomedical subjects
W A Littler
Publications and source records attributed to W A Littler.
Survival after acute myocardial infarction in Asian and white patients in Birmingham.
OBJECTIVE: To compare outcome after infarction in South Asian patients, comprising Indians, Pakistanis, Bangladeshis and individuals of East African origin, in Birmingham with that in white patients in the same city. DESIGN: A prospective case-control study. SETTING: Three large district general hospitals. PATIENTS: 102 South Asian patients discharged from hospital after an acute myocardial infarction were matched for age, sex, time and season of infarct, and hospital of admission with white patients. MAIN OUTCOME MEASURES: Survival and complication. RESULTS: There was no significant difference in survival or complications during the four years after an acute myocardial infarction in South Asian and white patients. CONCLUSION: The survival and clinical course of South Asian and white patients discharged after an acute myocardial infarction were similar over a four year period.
Africa↗
Dental prophylaxis for endocarditis.
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Anti-Bacterial Agents↗
Effect of quinapril on blood pressure and heart rate in congestive heart failure.
The effect of quinapril on blood pressure (BP), heart rate (HR) and their variabilities in 12 patients with severe congestive heart failure (New York Heart Association class III and IV) was assessed using ambulatory electrocardiographic and intraarterial monitoring. Mean +/- standard deviation daytime BP was 122/75 +/- 20/15 mm Hg at baseline and 113/70 +/- 13/16 mm Hg after 16 weeks of therapy with quinapril (p greater than 0.05 for systolic and diastolic BP); mean nighttime BP was 114/69 +/- 19/14 mm Hg at baseline and 107/69 +/- 15/14 mm Hg with quinapril (p greater than 0.05 for systolic and diastolic BP). Mean daytime HR was unchanged but nighttime HR was reduced from 77 +/- 11 to 71 +/- 10 beats/min, p = 0.02. HR variability (difference between the 75th and 25th percentiles of the frequency distribution of RR intervals) increased from 91 +/- 34 to 134 +/- 47 ms, p = 0.008. The variability of successive differences between RR intervals also increased significantly (75th to 25th percentile = 17 +/- 4 ms at baseline and 31 +/- 26 ms with quinapril, p = 0.02). Long-term quinapril caused clinically unimportant decreases in BP in patients with severe congestive heart failure. An increase in vagal activity caused by the reduction in circulating angiotensin II may account for the effect of converting enzyme inhibition on HR and its variability.
Adult↗
Antibiotic prophylaxis and infective endocarditis.
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Adult↗
Serum cortisol levels predict infarct size and patient mortality.
We have investigated prospectively the serum cortisol response to acute myocardial infarction in 70 consecutive patients admitted to a coronary care unit and we have shown that the levels are significantly raised early in the course of the illness and prior to elevation of the cardiac specific enzyme fraction, creatine kinase MB. The magnitude of the cortisol response is related to the size of the ensuing infarction (rs = 0.54) as calculated from the total creatine kinase MB release (P < 0.001) and very high levels (> 2000 mumol/l) are predictive of mortality (P < 0.05). Serum cortisol levels may have a role in the early identification of myocardial infarction and in predicting those patients with a poor prognosis.
Anistreplase↗
Acute and chronic hemodynamic effects of xamoterol in mild to moderate congestive heart failure.
Xamoterol, a new beta 1 partial agonist, has the potential to modulate cardiac response to variations in sympathetic tone in patients with heart failure. Its properties should result in beta-receptor stimulatory effects at low levels of sympathetic tone and beta-receptor protective effects at higher levels of sympathetic tone. The acute effects of intravenous (i.v.) xamoterol on hemodynamics at rest and during exercise were studied in 30 patients with mild to moderate heart failure (13 patients in New York Heart Association class II; 17 in class III) due to ischemic (n = 24) or cardiomyopathic (n = 6) heart disease. Cardiac index, stroke volume and stroke work index at rest were significantly improved after i.v. administration of xamoterol and consistent with net agonist effects. During exercise, heart rate and double product were significantly reduced (net antagonist effects), but with preservation of the expected increases in cardiac index and systolic blood pressure. These hemodynamic findings confirm the ability of xamoterol to modulate cardiac response to variations in sympathetic tone. Tachyphylaxis and arrhythmogenicity limit the chronic use of drugs with full beta-agonist properties as positive inotropes in heart failure. The patients were therefore entered into a 6-month double-blind, placebo-controlled, crossover study of chronic oral xamoterol therapy, 200 mg twice daily, and the hemodynamic responses to i.v. xamoterol were repeated at the end of the trial. No impairment in either resting or exercise effects was observed, indicative of a maintained response and absence of tachyphylaxis after chronic therapy. Furthermore, 24-hour ambulatory electrocardiographic monitoring showed no change in ventricular arrhythmias during oral treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Adrenergic beta-Agonists↗
Effects of the angiotensin converting enzyme inhibitor, benazepril, on the sino-aortic baroreceptor heart rate reflex.
The effects of monotherapy with the angiotensin converting enzyme inhibitor benazepril (10 mg once daily) on cardiovascular baroreceptor reflexes were determined in 10 patients with essential hypertension using a randomized, double-blind, placebo-controlled, cross-over protocol. Early sino-aortic baroreceptor/heart rate reflex resetting was apparent with acute treatment; this effect persisted throughout the active treatment period. Changes in baroreflex sensitivity did not appear to mediate the hypotensive effect of benazepril.
Angiotensin-Converting Enzyme Inhibitors↗
Comparison of the haemodynamic effects of dopexamine and dobutamine in patients with severe congestive heart failure.
Dopexamine hydrochloride is a novel compound with properties of DA1-dopaminergic and beta 2-adrenergic receptor agonism and neuronal noradrenaline uptake inhibition. It has been shown to produce beneficial renal and haemodynamic effects in patients with severe heart failure. We compared the haemodynamic effects of dopexamine (0.5 to 6 micrograms/kg/min) with those of dobutamine (5 to 25 micrograms/kg/min) in 9 patients with severe congestive heart failure. The two drugs were similar in their effects at peak infusion rates: heart rate increased (dopexamine 87 +/- 17 to 100 +/- 14; dobutamine 91 +/- 18 to 103 +/- 17 min-1), cardiac index increased (dopexamine 1.7 +/- 0.5 to 2.8 +/- 1.1; dobutamine 1.8 +/- 0.5 to 3.0 +/- 1.1 l.min-1.m-2) and systemic vascular resistance decreased (dopexamine 1553 +/- 221 to 1117 +/- 432; dobutamine 1721 +/- 347 to 1280 +/- 433 dyne.s.cm-5). Neither drug affected pulmonary artery wedge pressure (dopexamine 24 +/- 6 to 22 +/- 6; dobutamine 25 +/- 9 to 24 +/- 10 mm Hg). Dopexamine had significantly lower peak effects on left ventricular stroke work index (dopexamine 20 +/- 9, dobutamine 27 +/- 15 g.m.m-2, P less than 0.05) and cardiac power output (dopexamine 0.71 +/- 0.36, dobutamine 0.93 +/- 0.46 W, P less than 0.05). These haemodynamic effects, due largely to vasodilatation but with some contributory positive inotropy, indicate that dopexamine will be useful in the acute treatment of congestive heart failure.
Dobutamine↗
Acute aortitis and aortic incompetence due to systemic rheumatological disorders.
We report the clinical, laboratory and echocardiographic features of five cases of aortic incompetence associated with ankylosing spondylitis, rheumatoid arthritis and undefined connective tissue diseases. Immunosuppression with steroids and cytotoxic agents was used to suppress aortic root inflammation in four cases; in three the aortic root size stabilized and the patients remain well with no evidence of increasing aortic incompetence. In one case, control of the inflammatory process was never fully achieved for any length of time and the patient died shortly after aortic valve replacement. A fifth case required urgent valve replacement and remains well. A systemic rheumatological disorder should be considered in cases of apparent "lone" aortic incompetence and conversely aortic incompetence should not be overlooked in established systemic rheumatological disease. Immunosuppressive therapy may prevent or delay the need for aortic valve replacement in such cases.
Adult↗
Non-diabetic microalbuminuria in clinical practice and its relationship to posture, exercise and blood pressure.
1. The effects of posture and exercise on the relationship between low-level urinary albumin excretion (microalbuminuria) and blood pressure was investigated in two groups of non-diabetic patients at increased cardiovascular risk: 21 otherwise healthy patients with untreated essential hypertension (blood pressure greater than 160/90 mmHg), and 14 age-matched patients with blood pressure at presentation within the normotensive range (less than 160/90 mmHg) attending a cardiovascular clinic for assessment of chest pain. 2. A significant linear relationship between logarithmically transformed 'spot' urinary albumin/creatinine ratio and simultaneous clinic blood pressure existed when data from both groups of patients were analysed (r = 0.58, P less than 0.05). The relationship between the scatter plot of blood pressure and the albumin/creatinine ratio appeared most marked when the mean blood pressure exceeded 120 mmHg. 3. In patients with essential hypertension, clinic systolic blood pressure was related to the albumin/creatinine ratio in simultaneous 'spot' urine samples (r = 0.69, P less than 0.05) and also to the albumin/creatinine ratio in early-morning urine samples (r = 0.51, P less than 0.05). However, the relationship between clinic blood pressure and simultaneous 'spot' urinary albumin/creatinine ratio in the patients with chest pain did not achieve significance when analysed independently. 4. Hourly averaged ambulatory intra-arterial blood pressure was recorded in four of the patients with essential hypertension during normal daytime activity, and a significant correlation with the simultaneous hourly daytime urinary albumin/creatinine ratio was found (r = 0.65, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Influence of racial origin on admission rates of patients with suspected myocardial infarction in Birmingham.
All patients with suspected myocardial infarction admitted to hospital in four Birmingham health districts were studied to test the hypothesis that Asian patients would be overrepresented and Caribbean patients underrepresented compared with the indigenous population. One thousand four hundred and ninety six patients had a final diagnosis of myocardial infarction or severe angina pectoris. The relative risk of admission for Asian men compared with white men aged 45-64 years was 2.65 (95% confidence interval 2.20 to 3.19) and the risk for Asian men was high for both myocardial infarction and ischaemia when analysed separately. The relative risk of admission for Caribbean men compared with white men was 0.53 (95% CI 0.33 to 1.20). The relative risk for Asian women compared with white women in the same age group was 2.58 (95% CI 1.68 to 3.96), but this was due to an excess of admissions diagnosed as ischaemia rather than infarction in the Asian women. For Caribbean and white women the risk of admission was the same, although significantly fewer Caribbean women were admitted with myocardial infarction. The study was undertaken in 1986-87 and population data had to be derived from the 1981 census. The resident population changed in those five years and so the results were recalculated making allowances for these changes in the health districts involved. Based on these data the admission rate for Asian men with suspected myocardial infarction aged 45-64 was nearly twice that for white men (1.8): the relative risk of admission for Asian men compared with white men was 2.04 (95% CI 1.53 to 2.18). For Caribbean men the relative risk compared with white men was 0.45 (95% CI 0.29 to 0.71). For Asian women the relative risk of admission calculated from the adjusted census data resemble that in white women aged 45-64 years. The relative risk for admission with coronary heart disease in Asians is higher than expected work; one possible explanation for this is that the Asian population resident in the area under study was larger than estimated. The single major difference in risk factors was the high prevalence of diabetes mellitus in Asians (19.5% compared with 8.3% for white residents) but this did not wholly account for the excess of admissions from the Asian community.
Asia↗
Immunoglobulin response to intravenous streptokinase in acute myocardial infarction.
OBJECTIVE: To devise assays to assess and follow the specific antibody response in patients treated with streptokinase for acute myocardial infarction. DESIGN: Venous blood samples were collected before treatment with streptokinase started and subsequently at regular intervals over one year. Specific IgG and subclass IgG1 were assessed by an enzyme linked immunosorbent assay. SETTING: Coronary care unit in a general hospital. PATIENTS: 48 patients with acute myocardial infarction: 22 patients had venous blood samples taken at presentation only; serial blood samples were taken from 20 patients who then received thrombolytic therapy with streptokinase and six patients who were unsuitable for thrombolytic therapy. RESULTS: Titres of antibodies to streptokinase were low at presentation in 36 (75%) of the 48 patients. Serial measurements made in 20 patients showed the virtual disappearance of antibody within the first 24 hours. This was followed by a steady increase in the specific IgG1 titre, which peaked at day 14 before gradually declining. Values at one year remained significantly higher than baseline values. There was no evidence of an IgM response in the patients studied. CONCLUSION: Low titres of antibodies to streptokinase were widespread in the population. Antibody was consumed after treatment and the subsequent immunoglobulin rise suggested a secondary immune responses; the recently described neutralising capacity to streptokinase is probably related to this antibody.
Acute Disease↗
Effect of unrestricted activity on accuracy of ambulatory blood pressure measurement.
A validation study of the Takeda TM-2420 ambulatory blood pressure recorder was performed on 10 subjects using the Oxford ambulatory intra-arterial recording apparatus during unrestricted activity. Electronic linkage of the two recorders ensured simultaneous blood pressure readings, taken from opposite arms. Although there was close approximation of intra-arterial and automated sphygmomanometric recordings over the range of blood pressure encountered in this study, there was a wide scatter of points and a tendency for the machine to underestimate systolic pressure by more than 15 mm Hg in the hypertensive range (systolic blood pressure more than 160 mm Hg) was detected. These findings suggest that automated recording of blood pressure during unrestricted activity may have a proportion of artifactual readings. Although simultaneous intra-arterial blood pressure recording may not be appropriate for widespread use in device validation, this study illustrated some potential disadvantages of the current validation recommendations, namely, the absence of assessment of device accuracy during unrestricted and ambulatory activity.
Adult↗
The correlation of cardiac power output to exercise capacity in chronic heart failure.
Cardiac haemodynamics are deranged in chronic heart failure but fail to predict the exercise capacity of the patient. Cardiac power output is a descriptor of cardiac function derived from preload, blood pressure and cardiac output. Forty-one patients with moderately severe and severe chronic heart failure were exercised on a cycle ergometer to determine the relationship between traditional haemodynamics and cardiac power output and exercise capacity. Resting cardiac power output was no more predictive of exercise capacity than resting stroke-work index or resting cardiac index (r = 0.53, 0.61 and 0.51 respectively). Maximum cardiac power output and the ability to increase cardiac power output, however, were correlated with exercise capacity (r = 0.79 and 0.80). It is concluded that resting cardiac power output does not predict subsequent exercise capacity but that maximum cardiac power output and the ability to increase cardiac power output on stimulation are good descriptors of functional cardiac reserve.
Adult↗
The effects of the partial beta 1-agonist xamoterol on heart rate and ventricular arrhythmias in patients with mild to moderate heart failure.
A major concern with the use of oral inotropes in chronic heart failure is their propensity to exacerbate cardiac arrhythmias. In a double-blind randomized placebo-controlled crossover study of xamoterol, a novel beta 1-partial agonist, 24 h ambulatory electrocardiograms were obtained in 26 patients prior to and at the end of 13-week treatment periods. During treatment with xamoterol there was no significant change in mean hourly number of ventricular extrasystoles compared with baseline and placebo (30 +/- 17 vs 56 +/- 42 and 18 +/- 7, respectively), or in the number of patients showing complex forms (multiform VEs, pairs, ventricular tachycardia) (20/26 vs 19/26 and 19/26, respectively), or ventricular tachycardia alone (5/26 vs 4/26 and 6/26, respectively). Xamoterol therapy also stabilized heart rate variability over the 24 h period.
Adrenergic beta-Agonists↗
Comparison of felodipine with nifedipine as additions to metoprolol in the treatment of hypertension. U.K. Multicentre Hospital Group.
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Adult↗
Control of blood pressure in hypertensive patients with felodipine extended release or nifedipine retard.
1. This multicentre hospital study compared the antihypertensive efficacy and the tolerability of once daily felodipine extended release (ER) with twice daily nifedipine retard (R) in hypertensive patients inadequately controlled on metoprolol monotherapy. 2. One hundred patients, aged 20-70 years, whose seated diastolic blood pressure was 100-115 mmHg after 4 to 6 weeks of metoprolol (200 mg day-1) monotherapy, were randomised, double-blind, to receive felodipine ER 10 mg once daily or nifedipine R 20 mg twice daily for 8 weeks. The dosage of felodipine or nifedipine was doubled if seated diastolic blood pressure exceeded 95 mmHg, 2 or 4 weeks after randomisation. Metoprolol 200 mg once daily was taken throughout the trial. 3. Fifty-one patients received felodipine ER and 49 nifedipine R; 46 and 45 respectively completed the 8 week trial. About half of patients on each treatment needed the higher dose. The baseline characteristics of the felodipine and nifedipine groups were generally well balanced. 4. Seated diastolic blood pressure was reduced by 17 mmHg for felodipine (24 h post-dose) and by 9 mmHg for nifedipine (12 h post-dose), a difference between treatments of 8 mmHg (95% confidence interval 5 to 12 mmHg, P less than 0.0001). The attained blood pressures at the end of the study (felodipine 90 +/- 10, mmHg, mean +/- s.d.; nifedipine 95 +/- 10) were also significantly different (95% confidence interval for the 5 mmHg difference, -9 to -1 mmHg, P less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗