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Biomedical subjects

K S Channer

Publications and source records attributed to K S Channer.

At least 73 records · Page 4Linked to original sources
PubMed1997

Response of normoxic pulmonary arteries of the rat in the resting and contracted state to NO synthase blockade.

1. The pulmonary vasculature is normally in a low resting state of tone. It has been hypothesized that this basal tone is actively maintained by the continuous release of a vasodilator in the resting state. However, evidence for basal release of nitric oxide (NO) is inconclusive. 2. We studied the release of NO in arteries from the pulmonary circulation of male Wistar-Kyoto rats by examining the effects of the L-arginine analogue NG-nitro-L-arginine methyl ester (L-NAME) on resting pulmonary arteries and on vessels pre-contracted with prostaglandin F2(alpha) (PGF2 alpha). 3. Rats (n = 21) were killed by an overdose with pentobarbitone. Pulmonary arteries were dissected (mean internal diameter 459 +/- 11 microns) and mounted in a small vessel wire myograph. Resting tensions were to set to stimulate transmural pressures of 17.5 mmHg. 4. L-NAME (100 microM) was found to produce a contraction of 0.64 +/- 0.09 mN mm-1 in resting pulmonary arteries when added alone to the myograph bath. This contraction was not produced following removal of the endothelium. Vessel contraction to PGF(2 alpha) (100 microM) was found to be significantly greater when carried out in the presence of L-NAME (100 microM) -1.37 +/- 0.15 mN mm-1 compared with 1.96 +/- 0.17 mN mm-1. Dilation following acetylcholine (ACh) (1 microM) was abolished in the presence of L-NAME (100 microM). 5. Rat pulmonary artery contraction in response to the addition of L-NAME and the absence of contraction upon removal of the endothelium provides supportive evidence of the active release of nitric oxide for the maintenance of resting tone.

Animals↗
PubMed1997

Evaluation of a protocol to select patients of all ages for cardioversion from atrial fibrillation.

OBJECTIVE: to audit the success of a decision protocol to select patients for cardioversion from atrial fibrillation or flutter by recording the success of cardioversion and the maintenance of sinus rhythm over a 2-year period. DESIGN: retrospective case notes review. SETTING: a teaching hospital coronary care unit and cardiology department. PATIENTS: 227 consecutive patients were considered for cardioversion from atrial fibrillation or flutter from 1989 to 1992; 128 fulfilled the selection criteria. MAIN OUTCOME MEASURES: successful cardioversion and maintenance of sinus rhythm after cardioversion. RESULTS: 116 (91%) patients selected by application of the guidelines were successfully cardioverted. The probabilities of maintaining sinus rhythm at 6, 12 and 24 months were 0.92, 0.88 and 0.73 respectively. CONCLUSION: careful selection of patients in atrial fibrillation identifies a group in whom cardioversion is likely to be safe and successful regardless of age.

Adult↗
PubMed1997

How important is family history in ischaemic heart disease?

A positive family history is an established risk factor for ischaemic heart disease, but the size of the contribution relative to classical risks is open to debate. The literature suggests that inherited factors are important in the development of premature ischaemic heart disease, but decline in importance with age. A polymorphism in the angiotensin-converting-enzyme gene was the first new genetic factor thought to contribute independently and significantly to cardiovascular risk. However, more recent large prospective studies have indicated that its contribution is smaller than was originally thought. Interventions should continue to be targeted at the reduction of important environmental factors, such as smoking cigarettes.

Adoption↗
PubMed1997

Assessment of the value of technician reporting of electrocardiographs in an accident and emergency department.

OBJECTIVE: To assess the value of a cardiac technicians' report on electrocardiographs (ECGs) in reducing serious errors of interpretation by senior house officers. METHODS: A parallel study of interpretation of ECGs by senior house officers from 238 cases seen in an accident and emergency (A&E) department in a teaching hospital. 129 ECGs were reported by a cardiac technician at the time of recording and before the senior house officer wrote a report, and 109 were reported only by the senior house officers. Misinterpretations by doctors and technicians were graded by a consultant cardiologist on a four point scale and compared in the two groups. Serious errors (grade 4) were defined as those which potentially affected immediate management. RESULTS: The number of grade 4 errors of interpretation of ECGs by A&E senior house officers was reduced by 59% when there was a prior technical report (mean (SD), 18(17)% v 6 (7%); Fisher's exact test P < 0.05). CONCLUSIONS: When cardiac technicians provide a report on an ECG at the time of its recording, serious errors of interpretation by senior house officers are reduced.

Allied Health Personnel↗
PubMed1997

Prognostic implications of qualitative assessment of left ventricular function compared to simple routine quantitative echocardiography.

OBJECTIVE: To compare the prognostic value of qualitative estimates of left ventricular function with that of routine simple quantitative indices used in echocardiography. DESIGN: Retrospective follow up study. SETTING: University hospital. PATIENTS: The records of 2,964 patients who had undergone echocardiography and who could be traced on the family health services register were examined; 919 cases were included in the study, and a further 458 were used to validate the statistical models for prognostic assessment. There were 928 exclusions on the basis of referral for or diagnosis of alternative conditions, and 659 because of incomplete collection of the qualitative and quantitative data used in the study. MAIN OUTCOME MEASURE: Survival over the study period. RESULTS: A qualitative "eyeball" estimate of left ventricular function was of prognostic significance (relative risk of poor v good, 2.248; P << 0.001; 95% confidence interval 1.620 to 3.119). None of the quantitative echocardiographic indices was of independent prognostic significance when all variables were tested simultaneously in the regression model. CONCLUSIONS: A qualitative echocardiographic estimate of left ventricular dysfunction is of prognostic value, supporting the view of many cardiologists who use their overall impression of left ventricular function at echocardiography as the basis for treatment decisions.

Adolescent↗
PubMed1997

An evaluation and improvement program for inpatient anticoagulant control.

To improve the management and therapeutic control of inpatients on anticoagulant drugs, combined prescription and monitoring charts have been developed for both heparin and warfarin which incorporate clinical guidelines. These have been introduced throughout a 700-bedded acute teaching hospital via a structured program of change management. We have demonstrated improvements in the quality of anticoagulant control (assessed with a custom-written computer program), adherence to clinical guidelines and quality of monitoring and prescribing of anticoagulants in inpatients. The percentage time spent under-anticoagulated with heparin (activated partial thromboplastin time ratio < 1.5) fell from 32.7% to 18.5% (p < 0.0001), whereas there was no change in percentage time over-anticoagulated (5.1% vs. 5.8%; p = ns). The percentage time spent under-anticoagulated with warfarin was unaltered (26.3% vs. 29.8%; p = ns) but the percentage time spent over-anticoagulated (International Normalised Ratio > 4.5) was halved from 5.4% to 2.7% (p < 0.001). We conclude that the introduction of the charts led to significant improvements in anticoagulant control.

Aged↗
PubMed1996

The effect of meals of differing composition on exercise tolerance in patients with angina pectoris.

In this study we compared different dietary constituents and their effect on the angina threshold. We compared carbohydrate-rich, fat-rich and balanced liquid diets on effort tolerance in 14 patients of mean (range) 61 (41-73) years of age with chronic stable angina. On four different occasions at least 1 week apart, patients had exercise treadmill tests after an overnight fast and then after a rest period of 1 h ingested one of three different approximately isocalorific (about 4000 kJ) liquid drinks of 600 ml consisting mainly of: fat, carbohydrate or a balanced meal with an equal volume of water as control. Meals were given in random order. Analysis of the mean (SD) differences in heart rate between fasting and the post-prandial state for the different meals revealed a significant increase between water and the other meals, fat (+4(6) beats.min-1 P < 0.002), balanced (+9(17) beats.min-1 P < 0.004), and carbohydrate (+10(12) beats.min-1 P < 0.0002). There was no significant difference between the groups as regards systolic or diastolic blood pressure. Cardiac output increased following the meals but decreased after water; however, there was a significant difference between water and balanced meals. Exercise tolerance fell following all the meals but was significantly greater after a balanced (mean (SD) -108(129) s P < 0.01) and carbohydrate meal (-92(52) s P < 0.001). The reduction in exercise duration following a fat meal (-36(53)s) was not significantly different from that following water (-8(43) s) but was significantly smaller than after a carbohydrate meal (P < 0.02). Time to 1 mm of ST depression showed similar changes to that of total exercise duration, being significantly lower after a carbohydrate (mean (SD) -76(77) s P < 0.01) and balanced meal (-76(63) s P < 0.005). Time to 1 mm ST depression, although reduced by a fat meal (-15(84) s) was significantly less than after a carbohydrate meal (P < 0.02). In conclusion, patients with chronic stable angina have impaired effort tolerance and a lower angina threshold after high calorie containing liquid meals. Meals rich in carbohydrate have greater effects than meals where the majority of calories are derived from fat. Patients should be advised to avoid exercise in the first 30 min after eating.

Adult↗
PubMed1996

Doppler measurement of cardiac output during cardiopulmonary resuscitation.

OBJECTIVE: To estimate the cardiac output produced by external cardiac compression during standard cardiopulmonary resuscitation performed by two groups of operators with different levels of experience and training. METHODS: Cardiac output was measured by Doppler aortovelography. All patients included in the study had necropsy examinations. Only patients without evidence of pulmonary embolism, myocardial rupture, aortic valve disease, or acute depletion of the intravascular volume were included. RESULTS: 31 patients presenting to the accident and emergency department suffering from non-traumatic cardiac arrest had cardiac output measurements made during resuscitation. Eleven patients were excluded after necropsy examination. The median cardiac index for the 20 study patients was 3.2 L min-1 m-2. The cardiac output produced by massage by less experienced personnel (median 1.2 L min-1 m-2) was significantly less than that produced by those fully trained in the technique (median 3.2 L min-1 m-2; P < 0.01 95% confidence interval -2.36 to -1.29). The amount of resuscitation related trauma was no greater than in other published series. CONCLUSIONS: Differences in cardiac output during external cardiac compression are related to experience with the technique.

Adolescent↗
PubMed1996

Acute pulmonary vasodilatory properties of amlodipine in humans with pulmonary hypertension.

OBJECTIVE: Calcium antagonists are the only oral vasodilators shown to influence mortality in primary pulmonary hypertension, but the high doses required are often poorly tolerated. Amlodipine is a novel, relatively well tolerated, calcium antagonist. It has not been previously tested in humans with pulmonary hypertension. DESIGN: Calcium antagonists are claimed to be of benefit in the 20-30% of patients who respond--that is, whose mean pulmonary artery pressure and pulmonary vascular resistance decreased by 20% after acute administration. Increasing oral doses of amlodipine (up to 40 mg) were given and haemodynamic measurements were obtained by the use of indwelling pulmonary artery catheters 12 h after each dose. SETTING: Large teaching hospital, primary referral centre. PATIENTS: Six patients (four women; age range 37-78 years) with pulmonary hypertension (one with primary pulmonary hypertension, five with thromboembolic disease. MAIN OUTCOME MEASURES: Mean pulmonary artery pressure and pulmonary vascular resistance decreased by greater than 20% in two patients, mean pulmonary artery pressure decreased by greater than 20% in one patient with a pulmonary vascular resistance reduction of 19%. Thus, two of six patients responded to amlodipine and one partially responded. RESULTS: The whole group mean (SEM) pulmonary artery pressure decreased from 47.7 (4.2) to 41.7 (4.4) mm Hg and mean pulmonary vascular resistance from 8.6 (2.1) to 7.1 (1.8) Wood units. Cardiac output rose by a mean (range) of 4% (-20.8 to+20.8), heart rate by 8.8% (-10 to +33), and systemic systolic blood pressure decreased by 12% (-29.2 to -5.8) and diastolic blood pressure by 6.8% (-28.2 to+20.0). There were no symptoms of systemic hypotension. CONCLUSION: These results show that oral amlodipine can produce acute pulmonary vasodilatation in patients with pulmonary hypertension. Further studies are required, but amlodipine may prove to be of value in the treatment of primary pulmonary hypertension.

Adult↗
PubMed1996

Changes in haemodynamic parameters following Tai Chi Chuan and aerobic exercise in patients recovering from acute myocardial infarction.

In this study, 126 patients (90 males, average age 56 years, range 39-80) were randomised to Wu Chian-Ch'uan style Tai Chi (38), aerobic exercise (41) or a non-exercise support group (47) following acute myocardial infarction. Patients attended twice weekly for three weeks then weekly for a further five weeks. Heart rate and blood pressure were recorded before and after each session. Over the 11 sessions of exercise there was a negative trend in diastolic blood pressure only in the Tai Chi group (Rs = 0.79, p < 0.01). Significant trends in systolic blood pressure occurred in both exercise groups (Rs = 0.64 and 0.63, both p < 0.05). Only four (8%) patients completed the support group eight-week programme which was less than the number completing Tai Chi (82%; p < 0.001) and aerobic exercise groups (73%; p < 0.001).

Adult↗