PubMed Health⌕ Search

Biomedical subjects

A D Timmis

Publications and source records attributed to A D Timmis.

At least 109 records · Page 6Linked to original sources
PubMed1990

Lipid peroxidation associated with successful thrombolysis.

In 50 patients receiving thrombolytic treatment for acute myocardial infarction, peripheral venous blood samples were taken before streptokinase and 2 h later for assay of markers of free radical activity. Coronary arteriography was carried out within 72 h of thrombolysis. In the 42 patients with patent arteries after thrombolysis, the levels of thiobarbituric-acid-reactive material (TBA-RM), which reflects lipid peroxidation by free radicals, rose after streptokinase by 10.5 (SD 9.6) [corrected] nmol/g albumin, whereas in the 8 whose arteries remained occluded TBA-RM fell by 14.7 (8.0) [corrected] nmol/g albumin. There was no significant change in the 18:2 (9,11)/18:2 (9,12) molar ratio, an indicator of lipid isomerisation, either between the groups or after streptokinase. Thus, after successful thrombolysis there is a rise in lipid peroxidation, not seen in patients whose arteries remain occluded. This finding suggests free-radical-mediated damage at the time of reperfusion, and provides indirect evidence of reperfusion injury in man. This study provides evidence associating indicators of free radical activity with documented myocardial reperfusion in man.

Adult↗
PubMed1990

Coronary arteriography in a district general hospital: feasibility, safety, and diagnostic accuracy.

OBJECTIVE: To determine the feasibility, safety, and diagnostic accuracy of coronary arteriography in the radiology department of a district general hospital using conventional fluoroscopy and videotape recording. DESIGN: Observational study of the feasibility and safety of coronary arteriography in a district general hospital and analysis of its diagnostic accuracy by prospective within patient comparison of the video recordings with cinearteriograms obtained in a catheter laboratory. SETTING: Radiology department of a district general hospital and the catheter laboratory of a cardiological referral centre. SUBJECTS: 50 Patients with acute myocardial infarction treated with streptokinase who underwent coronary arteriography in a district general hospital three (two to five) days after admission. 45 Of these patients had repeat coronary arteriography after four (three to seven) days in the catheter laboratory of a cardiological referral centre. MAIN OUTCOME MEASURES: Incidence of complications associated with catheterisation and the sensitivity and specificity of video recordings in the district general hospital (judged by two experienced observers) for identifying the location and severity of coronary stenoses. RESULTS: Coronary arteriograms recorded on videotape in the district general hospital were obtained in 47 cases and apart from one episode of ventricular fibrilation (treated successfully by cardioversion) there were no complications of the procedure. 45 Patients were transferred for investigation in the catheter laboratory, providing 45 paired coronary arteriograms recorded on videotape and cine film. The specificity of the video recordings for identifying the location and severity of coronary stenoses was over 90%. Sensitivity, however, was lower and for one observer fell below 40% for lesions in the circumflex artery. A cardiothoracic surgeon judged that only nine of the 47 video recordings were adequate for assessing revascularisation requirements. CONCLUSIONS: Coronary arteriography in the radiology department of a district general hospital is safe and feasible. Nevertheless, the quality of image with conventional fluoroscopy and video film is inadequate and will need to be improved before coronary arteriography in this setting can be recommended.

Aged↗
PubMed1990

Myocardial infarction and biventricular free-wall rupture with shunting through a false aneurysm.

A 65-year-old man presented with acute inferior myocardial infarction and received thrombolytic therapy with clinical evidence of coronary arterial recanalisation. Recovery was uncomplicated until- the eighth day when he experienced recurrent chest pain with evidence of reinfarction in the same territory. This was associated with the development of a pansystolic murmur and cardiogenic shock. Cardiac catheterisation showed right coronary arterial occlusion and inferior infarction with a false aneurysm and a left-to-right shunt (shunt ratio 2.5:1). Surgery confirmed the formation of a false aneurysm caused by rupture of the free walls of both ventricles. Importantly, however, the interventricular septum was intact and the left-to-right shunt was through the false aneurysm itself. This is the first report of biventricular free-wall rupture with shunting through a false aneurysm treated successfully by surgery.

Aged↗
PubMed1990

Exertional myocardial ischemia in diabetes: a quantitative analysis of anginal perceptual threshold and the influence of autonomic function.

Patients with diabetes are prone to silent myocardial infarction and silent exertional ischemia. Although the mechanism is not clear, it may reflect a specific impairment of the sensory innervation of the heart. To test this hypothesis, anginal perceptual threshold was measured in 32 diabetic patients and 36 nondiabetic control patients, all of whom had typical exertional angina. Anginal perceptual threshold was defined as the time from onset of 0.1 mV ST depression to the onset of chest pain during treadmill stress electrocardiography. Although ST depression occurred earlier in the diabetic than in the nondiabetic group (111 +/- 82 versus 216 +/- 162 s, p less than 0.005), the anginal perceptual threshold in the diabetic group was delayed by a mean of 86 s (149 +/- 76 versus 63 +/- 59 s, p less than 0.001), with 95% confidence intervals of 53 to 119 s. Autonomic function tests were abnormal in the diabetic group, and in both groups regression analyses (using a third order polynomial) showed marked prolongations of anginal perceptual threshold as the heart rate responses to the Valsalva maneuver decreased to below the normal range (r = 0.5, p less than 0.001). There was a similar though less pronounced relation between anginal perceptual threshold and the heart rate responses to deep breathing (r = 0.3, p less than 0.02). These data suggest that prolongation of the anginal perceptual threshold may be caused by autonomic neuropathy involving the sensory innervation of the heart. To test sensory function, median nerve conduction studies were performed in 19 patients (10 diabetic and 9 nondiabetic).(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1990

Coronary lesion morphology in acute myocardial infarction: demonstration of early remodeling after streptokinase treatment.

Coronary lesion morphology was analyzed in 72 patients 1 to 8 days after streptokinase treatment for acute myocardial infarction and compared with lesion morphology in a control group of 24 patients with stable angina. In the streptokinase group the infarct-related artery was patent in 55 patients (76%). Compared with stenoses in the stable angina group, there were no differences in the stenosis length, severity, calcification or in the proportion located at an acute bend or at a branch point. However, lesions in the streptokinase group were more often irregular (p less than 0.005) and eccentric (p less than 0.01), had a shoulder (p less than 0.0001), globular filling defects (p less than 0.01), linear filling defects (p less than 0.00005) and contrast staining (p less than 0.05). Plaque ulceration index was higher in the streptokinase than in the stable angina group (6.2 +/- 7.9 versus 3.5 +/- 3.4, p less than 0.001). Of the 72 streptokinase-treated patients, 35 were maintained on heparin infusion until angioplasty 2 to 10 days later. At repeat angiography before angioplasty, globular lesion filling defects seen in eight patients had disappeared, whereas linear filling defects persisted in 7 of 14 cases. Fewer lesions were irregular (p less than 0.0001) and the ulceration index decreased from 7.4 +/- 10.4 to 3.0 +/- 1.6 (p less than 0.001). These data show that the lesion in the infarct-related artery after streptokinase treatment is irregular and often associated with filling defects, perhaps corresponding to plaque fissuring and intraluminal thrombosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1990

Prolonged anginal perceptual threshold in diabetes: effects on exercise capacity and myocardial ischemia.

Anginal perceptual threshold (the time from onset of 0.1 mV of ST segment depression to onset of angina during treadmill exercise) is prolonged in diabetic patients with coronary artery disease. In the present study, the functional significance of this perceptual abnormality was evaluated by analysis of its effect on exercise capacity and the severity of myocardial ischemia. Treadmill exercise in 32 diabetic patients and 36 nondiabetic control patients showed a close linear correlation between the time to onset of electrical ischemia (ST segment depression) and exercise capacity in both groups (r = 0.8 and 0.9, respectively; p less than 0.001). However, the slope of the relation was flatter in the diabetic group because prolongation of the anginal perceptual threshold permitted continued exercise as ischemia intensified. The anginal perceptual threshold itself showed a close linear correlation with exercise capacity in the diabetic group (r = 0.8, p less than 0.001), although in the nondiabetic group these variables were unrelated. The permissive effect of a prolonged anginal perceptual threshold on exercise capacity is undesirable as reflected by its correlation with ischemia at peak exercise (r = 0.6, p less than 0.001): the longer the threshold, the greater the exercise capacity and the more severe the ischemia. Indeed, the inverse relation between the severity of ischemia at peak exercise and exercise capacity in the nondiabetic group (r = 0.4, p less than 0.02) was completely lost in the diabetic group. Thus, in diabetic patients with coronary artery disease, anginal perceptual threshold is a major determinant of exercise capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1990

A new method of haemodynamic assessment of mitral stenosis in atrial fibrillation: construction of a nomogram.

Accurate haemodynamic assessment of mitral stenosis by hydraulic formulas requires measurement of the mean valve gradient and the cardiac output. The calculation is laborious, particularly in the presence of atrial fibrillation when averaged values obtained from multiple beat-to-beat determinations must be used. The relations between valve area, end diastolic gradient, and heart rate in 20 patients with mitral stenosis and atrial fibrillation were examined. In each patient the end diastolic pressure gradient for each cardiac cycle was related linearly to the RR interval of that cycle, and this relation was unchanged on exercise. The slope (S) and intercept (I) of this relation correlated with the degree of mitral stenosis as measured by the Gorlin valve area. The regression equations describing these relations were then used to construct a nomogram relating end diastolic pressure gradient to mitral valve area at different heart rates. When the nomogram was applied to catheterisation data from a further 30 patients the results correlated well with direct calculation of valve area by the Gorlin formula. The nomogram is simple to use, does not require measurement of cardiac output, and is independent of heart rate so that it is unnecessary for the patient to exercise during catheterisation.

Atrial Fibrillation↗
PubMed1989

Clinical outcome of coronary angioplasty for single-vessel disease.

The acute and long-term results of coronary angioplasty in 412 patients with single-vessel coronary artery disease are reported. Angiographic success was observed in 85.5% of all lesions and 84.7% of all arteries in which dilatation was attempted. Success rates improved during the study; since 1985, the angiographic success rate for non-occluded arteries has been 91.0%. Early complications occurred in 6.8%; angioplasty achieved clinical success in 80.3% of all patients at discharge from hospital. The median duration of follow-up was 772 days, with clinical status established for 98.8% of patients. 5 years after clinically successful angioplasty, cumulative cardiac survival was 96.6% and freedom from cardiac death and myocardial infarction was 90.4% (95.8% and 85.4%, respectively, on intention-to-treat analysis). Within 5 years of successful angioplasty, 12.4% of survivors underwent coronary bypass surgery and 16.9% had repeat angioplasty. Freedom from all cardiac events at 5 years was 70.2% after clinically successful angioplasty and 60.2% on intention-to-treat analysis. Angina symptoms were improved in over 80% of patients and abolished in 75%.

Activities of Daily Living↗
PubMed1989

The evaluation of ventricular function using gated myocardial imaging with Tc-99m MIBI.

Left ventricular function is an important prognostic indicator in patients with coronary artery disease. We have assessed a method of providing this information as an adjunct to myocardial perfusion imaging using Tc-99m MIBI (2-methoxy-2-methyl-isopropyl-1-isonitrile). Two separate studies, at rest and during exercise, were performed following an injection of 400-600 M Bq of Tc-99m MIBI in 62 patients. Cardiac gating permitted excellent myocardial edge definition during the cardiac cycle. Radionuclide fractional shortening (RFS) was calculated from the anteroposterior (AP) and the septum to lateral wall (SL) axes in diastole and systole. Results were compared with echocardiographic fractional shortening (EFS) and the ejection fraction (EF) obtained from the gated equilibrium blood pool using Tc-99m-labelled red blood cells. The RFS in the AP axis correlated closely with echocardiographic FS (r = 0.89, P less than 0.001). The RFS in both axes was averaged to provide a global RFS. Global RFS correlated closely with LV radionuclide EF (r = 0.83, P less than 0.001). Inter- and intra-observer reproducibility studies have shown a variability for the procedure of less than 10%. In conclusion, gated perfusion imaging with Tc-99m MIBI, provides useful functional information as an adjunct to perfusion imaging.

Coronary Disease↗
PubMed1989

Coronary angioplasty and left ventricular function in single vessel coronary artery disease.

Left ventricular function was investigated in 86 patients with single vessel coronary artery disease before and three to six months after successful angioplasty. Before angioplasty thallium-201 perfusion scintigraphy and technetium-99m gated equilibrium ventriculography in most patients showed that stress testing (exercise and ice water stimulation and isometric handgrip respectively) induced myocardial perfusion defects that were associated with a mean (SD) drop in left ventricular ejection fraction from 64 (6)% to 56 (7)%. After angioplasty there was residual coronary stenosis of less than or equal to 20% of the diameter of the vessel in 78 patients (group 1) and of between 20 and 50% in eight patients (group 2). After the procedure the perfusion defects seen during stress resolved in 86% of group 1 and in 87% of group 2. Despite the apparent improvement in myocardial perfusion left ventricular dysfunction persisted in group 2--that is during stress the left ventricular ejection fraction fell from 65% (6) to 56% (5). In group 1, on the other hand, the improvement in myocardial perfusion was associated with significant improvement in left ventricular function with a normal increase in ejection fraction from 63 (5) at rest to 67 (6) during stress. Radionuclide studies, one to six weeks after angioplasty in 30 group 1 patients showed continuing left ventricular decompensation during stress in nine (30%) of them despite correction of perfusion defects. But reinvestigation three to six months after the procedure showed recovery of left ventricular function with an increase in ejection fraction from 66 (5) at rest to 69 (7) during stress. These data indicate that coronary angioplasty procedures that give a residual stenosis of </= 20% improve myocardial perfusion and the response of the left ventricle to stress. The functional improvement may be delayed for up to three months, however, possibly because arterial healing at the angioplasty site is delayed. On the other hand, when the residual stenosis is between 21 and 50% of the diameter of the vessel subclinical left ventricular dysfunction during stress may persist indefinitely.

Adult↗
PubMed1988

Effect of intracarotid administration of ouabain in dogs.

Recent work has documented both centrally mediated vasoconstriction and, paradoxically, a withdrawal of sympathetic activity in response to cardiac glycosides. In the present study the possibility that these different neurogenic responses might be dose related was investigated by infusing ouabain (5, 10, and 20 micrograms) for 5 min into the right common carotid artery of 51 anesthetized mongrel dogs. Effects on vascular resistance in the isolated, separately perfused but innervated gracilis muscle were measured. A 5-microgram infusion of ouabain (n = 6) produced a prolonged decrease in gracilis vascular resistance (GVR) of 19.4 +/- 5.4% (SE) from 43.4 +/- 6.7 (SE) to 33.7 +/- 4.2 mmHg.ml-1.100 g muscle.min (resistance units, RU). This vasodilatory response was not present in nine additional dogs following denervation of the carotid bifurcation. A 10-microgram infusion had no significant effect on GVR (n = 5), but the 20-microgram infusion of ouabain (n = 8) caused a rapid increase in GVR from 42.1 +/- 5.0 to 47.6 +/- 5.7 RU, an increase of 14.4 +/- 5.6%, which was not influenced by denervation of the carotid bifurcation (n = 8). This vasoconstriction was transient returning toward the control levels by 20 min following the infusion. These data indicate important dose-related differences in vascular responses to ouabain that are directionally opposite and mediated by separate neurogenic mechanisms. At high doses a centrally mediated vasoconstriction dominates, whereas at low doses carotid bifurcation mediated vascular dilatation occurs.

Animals↗
PubMed1987

Contrast perfusion echocardiography: distribution and reproducibility of myocardial contrast enhancement in coronary artery disease.

A qualitative assessment was undertaken of the echocardiographic distribution of myocardial contrast enhancement after selective intracoronary injections of 2 ml of hand-agitated Urografin solution. The reproducibility and duration of contrast enhancement has also been examined. Forty-five contrast injections were given, 36 into the left and 6 into the right coronary arteries and 3 into bypass grafts of 28 patients undergoing diagnostic arteriography. Myocardial contrast enhancement occurred in 91% of cases. Although contrast enhancement appeared within the expected area of distribution of the artery infused, in no case was enhancement homogeneous. In 4 patients (1 of whom had undergone coronary bypass surgery), contrast enhancement also appeared in areas remote from the expected perfusion territory, in each case due to well established collateral supply seen angiographically. The contrast effect persisted for 71 +/- 26 seconds. Repeat injection in 5 patients (using identical echocardiographic windows) confirmed the reproducibility of the technique. No patient had symptoms related to the injections, although transient left ventricular wall motion abnormalities were observed in 3 cases. High-grade coronary stenoses did not affect distribution of myocardial contrast enhancement, although coronary occlusions produced well defined deficits. Thus, selective intracoronary injections of hand-agitated echocardiographic contrast medium produce regional myocardial enhancement, which probably reflects the perfusion territory of the artery. The technique is safe and reproducible in human subjects. Nevertheless, because regional enhancement after selective coronary injections is not homogeneous, analysis of enhancement deficits is unlikely to provide a clinically useful means of evaluating the functional significance of coronary stenoses.

Angiography↗