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Biomedical subjects

R N Stevenson

Publications and source records attributed to R N Stevenson.

17 recordsLinked to original sources
PubMed2003

Haemodynamic and electrocardiographic consequences of severe nicorandil toxicity.

A 35 year old woman was admitted to the emergency department two hours after ingesting 60x20 mg tablets of nicorandil, total 1.2 g. The dominant feature of icorandil toxicity was profound peripheral vasodilatation associated with coronary hypoperfusion. Despite widespread electrocardiographic signs of myocardial ischaemia, there was no evidence of myocardial damage and no serious cardiac arrhythmia. Volume loading and pressor support proved to be an effective treatment strategy.

Adult↗
PubMed1997

A case-control investigation of the relation between hyperlipidaemia and calcific aortic valve stenosis.

OBJECTIVE: To investigate the relation of hyperlipidaemia to calcific aortic valve stenosis. DESIGN: A case-control study designed to detect a clinically relevant difference in the fasting plasma concentrations of total cholesterol between the groups at the 5% level with a power of 90%. Predefined subgroup analyses were based on presence of significant coronary disease and valve morphology (that is, bicuspid or tricuspid). SETTING: A district general hospital. SUBJECTS: 20 patients with severe calcific aortic stenosis and 20 controls. RESULTS: Mean (SD) fasting plasma total cholesterol in patients with aortic stenosis was 0.79 (1.50) mmol/l greater than in the controls (p = 0.029). The magnitude of differences between patients with aortic stenosis and controls was similar whether the patients had coronary artery disease (0.78 (1.73) mmol/l) or not (0.80 (1.37) mmol/l). The presence of a stenosed tricuspid aortic valve was associated with a significant increase in plasma cholesterol (1.70 (0.87) mmol/l, p = 0.012). For bicuspid valves the degree of elevation of plasma cholesterol was less and not statistically significant. CONCLUSIONS: Calcific aortic stenosis is associated with hypercholesterolaemia, especially when the valve is tricuspid. Further studies are necessary to confirm that the relation is causal. This finding may have implications for measures to prevent the most common cause of cardiac valve replacement in the developed world.

Aged↗
PubMed1994

Relative value of clinical variables, treadmill stress testing, and Holter ST monitoring for postinfarction risk stratification.

The aim of this study was to compare the roles of clinical assessment, treadmill stress testing, and Holter ST analysis for postinfarction risk stratification in patients treated with thrombolysis. The study group consisted of 256 consecutive patients, all of whom underwent Holter ST monitoring early (mean 83 hours, range 48 to 180) after admission. Of these, 12 were excluded from the analysis either because Holter recordings were of insufficient quality (n = 6), or because reinfarction occurred within 24 hours of monitoring (n = 6). In the remaining 244 patients, 43 sustained a recurrent event (death, reinfarction, unstable angina) over the 8-month (range 3 to 12) follow-up period, and an additional 14 patients required revascularization. At multivariate event-free survival analysis, Killip class > or = 2 and Holter ST shift were independently predictive of the outcome. The strongest predictor was Holter ST shift at a cumulative duration of > 60 minutes. Of the 232 patients eligible for stress testing (12 sustained an event between Holter monitoring and the scheduled stress test), 196 were able to perform the test. The variable "inability to perform a stress test" was not independently predictive of outcome and did not influence the multivariate analysis. When clinical, Holter, and stress test variables were taken into account in patients who performed a stress test, Killip class was the only independent predictor of outcome (event-free survival). When revascularization was included as an end point, Holter ST shift was the only independent predictor of outcome. In conclusion, a significant proportion of recurrent events after thrombolysis occurs very early, before stress testing can be performed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Early exercise testing after treatment with thrombolytic drugs for acute myocardial infarction: importance of reciprocal ST segment depression.

OBJECTIVE: To investigate the clinical importance of reciprocal ST depression induced by exercise testing early after acute myocardial infarction in patients treated with thrombolysis. DESIGN: Prospective observational study. SETTING: District general hospital in London. SUBJECTS: 202 patients (170 men) aged 33-69 with acute myocardial infarction treated with thrombolysis. MAIN OUTCOME MEASURES: All patients underwent exercise testing and coronary arteriography. ST depression induced by exercise was classified as either reciprocal (associated with ST elevation) or isolated (occurring on its own). The relation between reciprocal ST depression and the following end points was studied: characteristics of the infarct, left ventricular ejection fraction, extent of coronary artery disease on arteriography, and presence of angina induced by exercise. RESULTS: Reciprocal ST depression occurred almost exclusively in Q wave infarctions and was associated with a lower overall ejection fraction than isolated ST depression. It tended to be associated with persistent occlusion of the coronary artery related to the infarct and did not indicate remote ischaemia due to multivessel coronary disease. Unlike isolated ST depression, reciprocal ST depression was not associated with angina induced by exercise. CONCLUSIONS: Reciprocal ST depression induced by exercise is usually associated with extensive Q wave infarctions and persistent occlusion of the artery related to the infarct. It does not seem to indicate reversible ischaemia and should not be used as a non-invasive marker of multivessel disease in the assessment of requirements for further investigation soon after acute myocardial infarction.

Adult↗
PubMed1993

Significance of reciprocal ST depression in acute myocardial infarction: a study of 258 patients treated by thrombolysis.

OBJECTIVE: To investigate the clinical significance of reciprocal ST depression on the presenting electrocardiogram in patients with acute myocardial infarction treated by thrombolysis. DESIGN: A prospective cohort analytical study. SETTING: A London district general hospital. SUBJECTS: Two hundred and fifty eight consecutive patients with acute myocardial infarction treated with thrombolysis. INTERVENTIONS: All patients underwent treadmill stress testing after a mean (SEM) of 10 (3) days; 200 patients (78%) were referred for coronary arteriography at 30 (16) days. MAIN OUTCOME MEASURES: Relation between reciprocal ST depression at presentation and several endpoints: time from start of chest pain to hospital presentation, electrocardiographic changes during early treadmill stress testing, presence of multivessel coronary disease, and clinical outcome in terms of recurrent ischaemic events (death, reinfarction, and unstable angina) during a 10 (range six to 12) month follow up. RESULTS: Presentation was generally early, but in this group of patients reciprocal ST depression was significantly related to the time from the start of symptoms, those with reciprocal change presenting on average one hour earlier than those without. Although reciprocal change on the presenting electrocardiogram was weakly associated with ST depression on treadmill stress testing, it was not indicative of remote ischaemia as a result of multivessel coronary disease or high grade collateralisation of the infarct related artery. There was no association between reciprocal change and the incidence of recurrent ischaemic events. CONCLUSION: Reciprocal ST depression on the presenting electrocardiogram seems to be a benign electrical phenomenon related to the time from the start of symptoms. It does not necessarily predict an adverse prognosis in patients treated by thrombolysis.

Adult↗
PubMed1993

Holter ST monitoring early after acute myocardial infarction: mechanisms of ischaemia in patients treated by thrombolysis.

OBJECTIVE: To investigate the mechanisms of Holter ST shift in patients with acute myocardial infarction treated by thrombolysis. DESIGN: Prospective observational study. SETTING: A London district general hospital. SUBJECTS: The study group consisted of 94 patients with acute myocardial infarction treated by thrombolysis. INTERVENTIONS: All underwent early 48 hour Holter ST monitoring and elective coronary arteriography. MAIN OUTCOME MEASURES: Relation of Holter ST shift to multivessel coronary disease, coronary patency, collateralisation, and morphology of the infarct related lesion. RESULTS: There was a trend towards an increased prevalence of Holter ST shift in patients with patency of the infarct related artery and those with multivessel disease. This was only significant in patients with three vessel disease, a significantly higher proportion of whom had > 3 episodes of ST shift (41% v 14%; p = 0.02) or a total duration of ST shift > 1 hour (35% v 13%; p = 0.04) than those with less extensive coronary disease. Holter ST shift occurred in a significantly higher proportion of patients with complex lesion morphology (Ambrose type 2 or 3) compared with those with lesions of Ambrose morphology type 1 or 2 (60% v 33%; p = 0.05). CONCLUSION: Holter ST shift detected early after thrombolysis is an ischaemic phenomenon with a complex pathophysiology. It reflects both remote ischaemia in patients with multivessel disease, and dynamic ischaemic processes related to complex lesion morphology in those with a patent infarct related artery.

Adult↗
PubMed1993

Comparison of coronary angiographic findings in acute and chronic first presentation of ischemic heart disease.

BACKGROUND: It is generally assumed that the clinical manifestations of ischemic heart disease occur randomly on the same underlying pathological process. Therefore, coronary angiographic findings should be similar whether the first presentation of ischemic heart disease is acute myocardial infarction or uncomplicated chronic stable angina. METHODS AND RESULTS: We studied 102 patients (men < or = 60 years old, women < or = 65 years old) presenting with either acute myocardial infarction as first manifestation of coronary artery disease with a concomitant coronary angiogram (55 patients; mean age, 50.2 years) or stable angina for at least 2 years with no history, ECG, or left ventriculographic evidence of any acute event and with an angiogram performed at least 2 years after initial symptoms (47 patients; mean age at symptom onset, 51.7 years). These angiograms were evaluated blindly for severity (number of vessels diseased, stenoses > or = 50%, occlusions), extent of disease (with an index derived by assigning a score of 0-3 per segment, depending on the proportion of lumen length irregularity and dividing the sum by the number of visualized segments), and pattern (discrete: three or fewer loci of disease never involving more than 50% of the length of any segment or diffuse: anything exceeding this). Patients with unheralded myocardial infarction had fewer vessels diseased, fewer stenoses and occlusion, and a lower extent index than those with uncomplicated stable angina (mean +/- SD of 1.3 +/- 0.8 versus 2.1 +/- 0.8, p < 0.001; 2.1 +/- 1.8 versus 3.9 +/- 1.8, p < 0.001; 0.6 +/- 0.6 versus 1.0 +/- 0.9, p < 0.02; and 0.6 +/- 0.5 versus 1.2 +/- 0.5, p < 0.001, respectively). A discrete pattern was present in 54.5% of patients with unheralded infarction and in only 8.5% of those with uncomplicated angina (p < 0.001). CONCLUSIONS: These very different angiographic findings suggest that unheralded acute myocardial infarction and uncomplicated chronic stable angina do not occur randomly on a common atherosclerotic background but rather that additional factors, such as a varying propensity to thrombosis, may predispose to one or the other of these two clinical syndromes.

Angina Pectoris↗
PubMed1992

Calcitonin gene-related peptide: a haemodynamic study of a novel vasodilator in patients with severe chronic heart failure.

The haemodynamic and neurohumeral response to a novel vasodilator calcitonin gene-related peptide was assessed in 11 patients with severe chronic heart failure. To assess tolerance, a continuous 48-h infusion (n = 6) was compared with a regimen of two successive 8-h infusions (n = 5). Haemodynamic response profiles were similar for both regimens, though the continuous infusion was poorly tolerated. Reductions in afterload reflected by changes in systemic vascular resistance and systemic blood pressure led to increases in cardiac index of at least 24%. Increments in heart rate accounted for much of the increase in cardiac output, there being no significant change in stroke volume index. The response was maintained over the 48-h study period with no tachyphylaxis. Renin and angiotensin levels increased significantly after 24 h. Calcitonin gene-related peptide exerts a favourable haemodynamic response in patients with severe heart failure. The dose used in this study, however, caused troublesome side-effects, particularly when given by continuous infusion. Further studies are required to establish the therapeutic range of this new peptide.

Aged↗
PubMed1991

Angiotensin converting enzyme inhibitors and magnesium conservation in patients with congestive cardiac failure.

OBJECTIVE: To investigate whether angiotensin converting enzyme inhibitors reduce diuretic induced magnesium excretion in patients in congestive cardiac failure. DESIGN: Cohort analytic study. SETTING: A London district general hospital. SUBJECTS: Thirty four patients with chronic congestive cardiac failure caused by ischaemic heart disease or cardiomyopathy selected consecutively from inpatients under the care of two consultant cardiologists. Nineteen patients (group 1) on diuretics alone were compared with 15 patients (group 2) taking diuretics plus either enalapril or captopril. All drug regimens were stable for at least three months before the study. Patients with impaired renal function (plasma creatinine greater than 120 mumol/l) were excluded. INTERVENTIONS: An intravenous loading dose of magnesium sulphate was given to minimise the variability in baseline magnesium state. MAIN OUTCOME MEASURE: Total urine magnesium excretion and creatinine clearance in 24 hour urine collections. RESULTS: Plasma magnesium was similar in the two groups. However, 24 hour urine magnesium excretion was significantly lower in group 2 than in group 1. Furthermore, creatinine clearance was also significantly lower in group 2 and correlated strongly with magnesium excretion. There was no such relation in group 1. There was no difference in fractional clearance of magnesium between groups. CONCLUSION: Angiotensin converting enzyme inhibitors have an important magnesium conserving action, possibly via their effect on glomerular filtration rate.

Aged↗