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T H Pringle

Publications and source records attributed to T H Pringle.

At least 19 recordsLinked to original sources
PubMed1997

Right coronary artery stenosis is associated with impaired cardiac endocrine function during exercise.

AIMS: Resting plasma levels of atrial natriuretic peptide and B-type natriuretic peptide rise with left ventricular dysfunction, but little is known about effects of cardiac ischaemia on atrial natriuretic peptide and B-type natriuretic peptide levels during exercise. We investigated exercise levels of atrial natriuretic peptide and B-type natriuretic peptide in patients with suspected angina to determine whether these measurements could improve non-invasive assessment of coronary disease severity. METHODS AND RESULTS: One hundred patients performed an exercise test (Bruce protocol) within 2 weeks of coronary angiography. Plasma levels of atrial natriuretic peptide and B-type natriuretic peptide were measured at rest and at peak exercise. Multivariate regression analysis was used to assess effects of age, sex, coronary anatomy, exercise time and ventricular function on atrial natriuretic peptide and B-type natriuretic peptide levels. Increasing age and female sex were significantly associated with higher resting atrial natriuretic peptide levels; age alone was associated with higher exercise atrial natriuretic peptide levels. As expected, left ventricular end-diastolic pressure and disease of left anterior descending and circumflex coronary arteries were associated with increased resting B-type natriuretic peptide levels. However, the usual rise in B-type natriuretic peptide levels during exercise was independently reduced by disease of the right coronary artery. CONCLUSION: This paradoxical effect of right coronary artery disease limits the value of natriuretic peptide measurements as predictors of coronary disease severity. Impaired release of B-type natriuretic peptide may reduce exercise tolerance in patients with right coronary artery disease.

Age Factors↗
PubMed1997

Diagnosing left ventricular dysfunction after myocardial infarction: the Dundee algorithm.

Large-scale trials of angiotensin converting enzyme (ACE) inhibitors after acute myocardial infarction (AMI) suggest that the benefits are greatest in patients with left ventricular (LV) dysfunction. However, early evaluation of LV function in all patients after AMI by current methods can be difficult due to a lack of resources and skilled personnel. Thus a clinical algorithm that could be used at the bedside to reliably identify patients with a left ventricular ejection fraction (LVEF) < or = 40% would be helpful as an occasional alternative to echocardiography. We have devised such an algorithm based on the presence of one of: (i) clinical signs of heart failure; (ii) an index Q-wave anterior myocardial infarction; (iii) lack of thrombolytic therapy when there is a history of two or more previous myocardial infarctions and a CK rise > 1000 U/l. We tested this new algorithm prospectively in the coronary care units of two hospitals (one UK and one USA). In the UK centre, the sensitivity and specificity of the algorithm at identifying patients with a LVEF < or = 40% were 82% and 72%, respectively. In the US centre, the sensitivity of the algorithm was 91% and the specificity 78% at identifying patients with LV dysfunction. We have validated a simple clinical algorithm which can be used at the bedside for identifying patients who would benefit from an ACE inhibitor after AMI.

Aged↗
PubMed1996

Prediction of late cardiac events by dipyridamole thallium scintigraphy in patients with intermittent claudication and occult coronary artery disease.

Concomitant coronary artery disease often occurs in patients with peripheral vascular disease, but it may be asymptomatic. Despite being asymptomatic, cardiovascular events are the main source of morbidity and mortality in this group of patients. Dipyridamole thallium scintigraphy has been shown to be of prognostic value in patients with peripheral vascular disease and symptomatic coronary artery disease, but its effect on the long-term outcome in the asymptomatic group of patients is less defined. Eighty-four consecutive patients with peripheral vascular disease and no symptoms of coronary artery disease were therefore evaluated by clinical assessment, dipyridamole thallium imaging, radionuclide ventriculography, and cardiac catheterization and followed for a mean of 66 months. Abnormal perfusion patterns were found on thallium scintigraphy in 48 patients (57%); fixed, mixed, and reversible defects were present in 14 (17%), 11 (13%), and 23 (27%) patients, respectively. Significant coronary artery disease was present in 52 patients (69%) and mean left ventricular ejection fraction was 44%. During the follow-up period, 23 patients had a cardiac event (nonfatal myocardial infarction or cardiac death). Univariate analysis of 15 clinical, scintigraphic, radionuclide, and angiographic variables revealed that age, angiographic extent of coronary artery disease, and an abnormal thallium scan were significant predictors of subsequent cardiac events. Multivariate stepwise logistic regression analyses selected fixed and mixed thallium defects and diffuse coronary artery disease as the only significant independent predictors of outcome. Thus, the present study shows the value of dipyridamole thallium scintigraphy as a valuable prognostic indicator for long-term event-free survival in a cohort of patients with peripheral vascular disease and no history or symptoms of coronary artery disease.

Aged↗
PubMed1996

Diagnostic value of B-type natriuretic peptide concentrations in patients with acute myocardial infarction.

Although elevations of plasma atrial natriuretic peptide (ANP) concentrations have been shown to have prognostic significance in patients after acute myocardial infarction (AMI), the relation between plasma levels of B-type natriuretic peptide (BNP) and cardiovascular mortality remains unknown. To test the prognostic value of plasma ANP and BNP after AMI, plasma concentrations were measured a mean of 3 days after infarction in 75 patients. During a median follow-up of 19.7 months, 14 patients (18.4%) died of cardiovascular causes. On univariate analysis, plasma ANP and BNP, Killip class, modified Peel index, left ventricular ejection fraction, and presence of left ventricular failure were all associated with cardiovascular mortality. In contrast, plasma ANP was the only variable that correlated with the development of symptomatic heart failure and hospitalization. For the combined end point of cardiovascular mortality, symptomatic heart failure, and hospitalization, plasma neurohormones were the only variables of predictive value. By stepwise regression analysis, plasma BNP was the only significant independent predictor of cardiovascular mortality (p = 0.001), whereas plasma ANP identified patients at risk of symptomatic heart failure and hospitalization (p = 0.002 and 0.019, respectively). This study indicates that plasma BNP measured after AMI is a powerful neurohormonal predictor of subsequent cardiovascular mortality, whereas plasma ANP correlates better with the development of symptomatic heart failure and hospitalization. Routine measurement of both of these peptides in the period immediately after an AMI may provide a simple means of risk stratification with different information gained from each peptide.

Adult↗
PubMed1995

Raised plasma levels of atrial natriuretic factor in cardiac allograft recipients: evidence of increased cardiac secretion and decreased renal clearance.

The mechanism(s) causing high levels of plasma atrial natriuretic factor (ANF) in cardiac allograft recipients is(are) unclear. The kidney is important for the clearance of ANF and renal function may decline with cyclosporin A therapy in these patients. The relationship between plasma ANF level and renal function and also the pharmacokinetics of a continuous infusion of ANF (15.5 ng.kg-1.min-1 for 60 min) was examined in 6 cardiac allograft recipients on cyclosporin A therapy. Resting plasma ANF levels were significantly higher in these patients than in 8 healthy subjects (71 vs. 21 ng.l-1). Both effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) were significantly lower in these patients than in healthy subjects (215 vs. 617 ml.min-1 and 55 vs. 102 ml.min-1 respectively). There was a significant inverse correlation between plasma ANF and ERPF (r = -0.86) and between plasma ANF and GFR (r = -0.81). During the period of ANF infusion, steady state plasma ANF levels were significantly higher in cardiac allograft recipients. Total body clearance of ANF was marginally lower in these patients than in healthy subjects (60 vs. 10.0 l.min-1) although this difference did not reach statistical significance. Derived endogenous secretion rate of ANF was threefold higher in patients when compared to healthy subjects (633 vs. 208 ng.min-1). We have therefore shown that cardiac allograft recipients on cyclosporin A have elevated plasma ANF levels and also decreased renal function. Pharmacokinetic analysis have shown that this increase in plasma ANF levels is due more to increased ANF secretion than to decreased ANF clearance in these patients.

Adult↗
PubMed1995

A late increase in free radical activity post myocardial infarction.

Free radicals (FR) are a highly reactive chemical species which have been implicated in the pathogenesis of reperfusion injury. Experimental models of reperfusion injury have demonstrated that FR scavengers improve myocardial salvage and thus it has been postulated that they may be of benefit in acute myocardial infarct (MI) patients treated with thrombolysis. Previous studies of FR activity post MI have focused on the immediate post reperfusion period; the present study investigates FR activity in post MI patients over a longer time span. Free radicals have a very short half-life and in clinical studies their activity is usually assessed indirectly by measuring either the level of FR reaction products such as malondialdehyde (MDA) or FR scavengers such as plasma thiols (PSH). In the presence of increased FR activity MDA levels increase and PSH levels decrease. Twenty-two acute MI patients had blood samples taken on admission, day 7 and day 21 post MI for measurement of MDA and PSH levels. On day 7 post MI a significant increase in MDA was detected P = 0.0001 (Sign test) (median change +2.1 mumol.l) and a significant decrease was detected in PSH P = 0.04 (Sign test) (median change, -38 mumol.l-1). No significant differences were detected between admission and day 21 levels of MDA and PSH. This study demonstrates the presence of enhanced FR activity at a later time point than has previously been recognised. White blood cells utilise FRs during phagocytosis and the late rise in FR activity detected in this study may reflect white blood cell removal of necrotic myocardium.

Adult↗
PubMed1994

Detection of left ventricular dysfunction after acute myocardial infarction: comparison of clinical, echocardiographic, and neurohormonal methods.

OBJECTIVE: The SAVE study showed that captopril improves mortality in patients with left ventricular dysfunction after myocardial infarction and that this benefit occurred even in patients with no clinically overt heart failure. On the basis of this, it seems important to identify correctly which patients have left ventricular dysfunction after a myocardial infarction. The objective was to compare various methods of identifying patients with left ventricular dysfunction (left ventricular ejection fraction, LVEF, < or = 40%) after acute myocardial infarction. The methods compared were echocardiography (quantitative and qualitative visual assessment), clinical evaluation (subjective assessment and three clinical score methods), and measurement of plasma concentrations of cardiac natriuretic peptide hormones (atrial and brain natriuretic peptides, ANP and BNP). DESIGN: Cross sectional study of left ventricular function in patients two to eight days after acute myocardial infarction. SETTING: Coronary care unit of a teaching hospital. PATIENTS: 75 survivors of a recent myocardial infarction aged 40 to 88 with no history of cardiac failure and without cardiogenic shock at the time of entry to the study. MAIN OUTCOME MEASURES: Sensitivities and specificities of the various methods of detecting left ventricular dysfunction were calculated by comparing them with a cross sectional echocardiographic algorithm for LVEF. RESULTS: Clinical impression was poor at identifying LVEF < 40% (sensitivity 46%). Clinical scoring improved this figure somewhat (modified Peel index sensitivity 64%). Qualitative visual assessment echocardiography was a more sensitive method (sensitivity 82%) for detecting LVEF < 40%. Plasma BNP concentration was also a sensitive measure for detecting left ventricular dysfunction (sensitivity 84%) but plasma ANP concentration was much poorer (sensitivity 64%). CONCLUSION: Left ventricular dysfunction is easily and reliably detected by echocardiographic measurement of LVEF and also by a quick qualitative echocardiographic assessment but is likely to be missed by clinical assessment alone. High concentrations of plasma BNP maybe another useful indicator of left ventricular dysfunction, particularly in hospitals where not all patients can be screened by echocardiography or radionuclide ventriculography after myocardial infarction.

Adult↗
PubMed1993

A comparison of the redistribution and reinjection techniques in dipyridamole thallium tomography.

The effect of the injection of additional thallium after a redistribution study and prior to a further resting study was evaluated in 21 patients with angiographically proven coronary artery disease. Using dipyridamole as the stress mechanism, the studies were carried out tomographically and the results analysed quantitatively with the Bull's-eye technique. Two patients had normal scans. Of the remaining 19, 11 patients had a perfusion defect which appeared irreversible on redistribution imaging. However, six of these patients demonstrated improved or normal uptake after the second injection of thallium. Of the eight patients with a reversible defect, two revealed considerably greater reversibility after reinjection. These results indicate that the reinjection of thallium prior to the resting study significantly (P < 0.02) improves the detection rate of ischaemia during dipyridamole thallium tomography.

Coronary Disease↗
PubMed1993

Circadian variation of tissue plasminogen activator and its inhibitor, von Willebrand factor antigen, and prostacyclin stimulating factor in men with ischaemic heart disease.

OBJECTIVES: To determine whether plasma concentrations of tissue plasminogen activator antigen, von Willebrand factor antigen, and prostacyclin stimulating factor and plasminogen activator inhibitor activity show circadian variation in men with ischaemic heart disease. DESIGN: Blood samples were obtained every four hours for 24 hours from 10 men with ischaemic heart disease. The men were ambulant from 08:10 until 00:00 when they went to bed and they remained in bed until 08:00 the following morning. PATIENTS: Ten men with positive diagnostic exercise tolerance tests with no significant past history, who were not regularly taking any medical treatment except for glyceryl trinitrate. RESULTS: There was significant circadian variation in plasminogen activator inhibitor activity (p = 0.001) (peak value 04:00 and trough value 20:00), but not in plasma concentrations of tissue plasminogen activator antigen, von Willebrand factor, or prostacyclin stimulating factor. CONCLUSION: Men with ischaemic heart disease showed a significant circadian variation in fibrinolysis. The combination of peak values of plasminogen activator inhibitor activity and failure of plasma concentrations of tissue plasminogen activator antigen to increase in the early morning must predispose to thrombosis at this time. The circadian variation in fibrinolysis may contribute to the increased incidence of myocardial infarction in the morning.

Aged↗
PubMed1993

Free radical markers in patients with angina pectoris and normal coronary angiograms.

Markers suggestive of enhanced free radical (FR) activity have been demonstrated in patients with chest pain and normal coronary angiograms. This may be of pathogenetic importance because FRs impair vascular relaxation and are generated following episodes of myocardial ischaemia/reperfusion. Fifteen patients with angina pectoris, normal coronary angiograms and either a positive exercise tolerance test and/or abnormal dipyridamole thallium tomogram were studied along with 15 age-, sex- and smoking-matched controls. A peripheral venous blood sample was obtained to measure the following FR markers: malondialdehyde, plasma thiols, red blood cell glutathione and superoxide dismutase. No significant differences were detected in the levels of any of the FR markers between either the group of 15 patients with chest pain and normal angiograms or the subgroup with positive exercise tolerance tests when compared to the controls. There is therefore no evidence of enhanced FR activity in patients with chest pain and normal coronary angiograms in peripheral venous blood samples.

Adult↗
PubMed1992

Relationship between the extent of coronary artery disease and indicators of free radical activity.

Clinical studies have demonstrated that patients with coronary artery disease (CAD) have markers suggestive of increased free radical (FR) activity when compared with normal subjects; however, the relationship between the extent of CAD and level of FR markers is not known. The following indices of FR activity, plasma malondialdehyde (MDA), plasma thiols (PSH), red blood cell (RBC) glutathione (GSH), and RBC superoxide dismutase (SOD) were measured in 58 patients admitted for coronary angiography and in 50 matched controls. Regression analysis demonstrated no significant correlation between MDA, PSH, GSH, or SOD, and the angiographic grade which indicated the severity of the CAD. Patients with angiographically proven CAD (median 7.9 nmol/ml IQR 6.9-9.2) and patients with a history suggestive of angina pectoris but normal coronary angiograms (median 8.4 nmol/ml IQR 7.4-9.9) had significantly raised MDA levels compared with the controls (median 6.85 nmol/ml IQR 6.1-7.4), p less than 0.001 and p less than 0.005, respectively. The patients with angiographically proven CAD had significantly lower GSH levels (median 1461 microM IQR 1348-1709, p less than 0.002) compared with the controls (median 1754 microM IQR 1492-1930). Significantly raised SOD levels also were detected in patients with angiographically proven CAD (median 121.8 U/ml RBC, IQR 113.8-143.9) and in patients with a history of suggestive of angina pectoris but normal coronary angiograms (median 146 U/ml RBC, IQR 96.8-156.7) when compared with controls (median 96.3 U/ml RBC, IQR 82.4-115.6), p less than 0.001 and p less than 0.02, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Circadian variation of white blood cell aggregation and free radical indices in men with ischaemic heart disease.

The fibrinolytic activity of blood has a circadian variation with increased thrombotic tendency in the morning. This may be a contributory factor to the circadian variation in the time of onset of thrombotic events. However, there has recently been increasing interest to the role of the white blood cells (WBC) and free radicals (FRs) in thrombosis. We have previously reported a circadian variation in WBC aggregation and FR status in normal volunteers. No one has yet studied possible circadian variations in these parameters in patients with stable ischaemic heart disease (IHD). Ten men with stable IHD had blood samples collected at four-hourly intervals from midday until midday the following day. The patients were ambulant until midnight at which time they went to bed and remained in bed until 0800 h. The following were measured on each sample: WBC aggregation, malondialdehyde (MDA) which is a product of lipid peroxidation by FRs; the FR scavengers, plasma thiol (PSH), red cell glutathione (GSH) and superoxide dismutase (SOD) which are all altered in the presence of increased FR activity. WBC aggregation and PSH had significant circadian variations, P < 0.015 and P < 0.001 respectively. The WBC aggregation peak was at 1200 h and trough at 1600 h, the PSH peak was at midnight and the trough at 0400 h. WBC behaviour and FR status influence the flow properties of blood. The largest rise in WBC aggregation occurred from 0800 h to 1200 h; such an increase in aggregation could predispose to microcirculatory occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗