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Biomedical subjects

R G Wilcox

Publications and source records attributed to R G Wilcox.

At least 55 records · Page 3Linked to original sources
PubMed1991

Ventricular arrhythmias during treatment with alteplase (recombinant tissue plasminogen activator) in suspected acute myocardial infarction.

Continuous electrocardiography during the first 24 hours of a stay in a coronary care unit was used to record ventricular arrhythmias during treatment with alteplase (recombinant tissue plasminogen activator) or placebo. Recordings were made on 378 of the 436 patients admitted to a double blind trial of alteplase or placebo in one participating centre of the Anglo-Scandinavian study of early thrombosis (ASSET), patients being selected according to the availability of recorders. Of these, 309 (158 given alteplase and 151 placebo) had greater than 5 hours of analysable data. Most of the arrhythmias were recorded in patients with an in hospital diagnosis of myocardial infarction. Ventricular couplets and ventricular tachycardia were significantly more common in the patients treated with alteplase. Further, in patients with myocardial infarction who had ventricular extrasystoles, couplets, or ventricular tachycardia type a, the number of hours in which each arrhythmia was recorded was significantly higher in the alteplase group. The various ventricular arrhythmias in the alteplase group tended to cluster in the first 4-12 hours of the recordings. During the first 24 hours admission there were four episodes of ventricular fibrillation in the alteplase group and five in the placebo group of taped patients. By one month there had been 18 deaths in these 309 patients (alteplase four, placebo 14). These bore no relation to any recorded arrhythmia. Clinical records for the patients with no or minimal tape data yielded six further episodes of ventricular fibrillation during the first 24 hours (three in the alteplase group and three in the placebo group). Of the total 436 patients, 10 of the 218 patients in the alteplase group had died by one month compared with 22 of the 218 patients treated with placebo. The use of alteplase increases the incident of non-life threatening ventricular arrhythmias. These results, however suggest that arrhythmia after thrombolysis in the pre-hospital phase may be less of a problem than it is perceived to be.

Adolescent↗
PubMed1991

A comparison of same day and separate day injection protocols for myocardial perfusion SPECT using 99Tcm-MIBI.

Three dose administration protocols for 99Tcm-MIBI were applied to groups of 15 patients with known or suspected ischaemic heart disease. Firstly, injections were given on consecutive days, with 300 MBq at rest and 500 MBq 24 h later at exercise. Secondly, both injections on the same day with 200 MBq at rest followed 1.5 h later by 1000 MBq during exercise. Finally, both injections on the same day with 200 MBq at rest followed 1.5 h later by 600 MBq during exercise. The diagnostic accuracy was significantly better when the administrations were on separate days than when given on the same day. There was no difference in diagnostic accuracy between the two same day protocols. The same day protocols gave a significantly higher false negative reporting rate than the separate day protocol.

Adult↗
PubMed1990

Effects of alteplase in acute myocardial infarction: 6-month results from the ASSET study. Anglo-Scandinavian Study of Early Thrombolysis.

In a randomised, controlled trial 2514 patients with suspected acute myocardial infarction received 100 mg intravenous alteplase (recombinant tissue plasminogen activator [rt-PA]) plus heparin within 5 h of onset of symptoms, and 2499 similar controls received placebo plus heparin. At 1 month the overall mortality rates were 7.2% and 9.8%, respectively, a relative reduction of 26% (95% confidence interval [CI] 11-39%). At 6 months the mortality rates were 10.4% (alteplase) and 13.1% (placebo), a relative reduction of 21% (95% Cl 8%-32%, p = 0.0026). 6-month mortality rates in patients with proven myocardial infarction were 12.6% and 17.1%, respectively (relative reduction 26%; 95% Cl 14-37%); this effect was similar for anterior (15.6% vs 21.2%) and inferior (7.7% vs 12.8%) myocardial infarction. 6-month mortality rates were lower in those treated with alteplase irrespective of other recognised cardiac risk factors. However, treatment with alteplase made no difference to subsequent cardiac events after one month (readmissions, reinfarctions, death) nor to treatment for angina or heart failure. Product limit estimates of one year mortality are 13.2% with alteplase and 15.1% with placebo. The corresponding figures for patients with an index diagnosis of myocardial infarction are 15.7% and 18.9%, a relative reduction of 16.9%.

Adolescent↗
PubMed1989

Thrombolysis with tissue plasminogen activator in suspected acute myocardial infarction. The ASSET Study.

Intravenous rtPA (total dose, 100 mg over 3 h) was compared with placebo in a prospective, randomized, double-blind trial in 5,011 patients with suspected AMI of less than 5 h duration. No ECG or enzymatic confirmation of the diagnosis was required for study entry. At 1 month 9.8% of patients given placebo had died compared with 7.2% of those who received rtPA (2.6% actual reduction, 26% relative reduction, with 95% confidence intervals of 11-39%). The majority of deaths occurred in patients who had an in-hospital diagnosis of MI (72% in both groups), with a 1-month infarct mortality of 13.1% in the placebo limb and 9.4% in the rtPA limb (relative reduction 28%, 95% CI, 14-41%). Approximately 18% of patients in both groups had a normal ECG on entry to the trial, and at 1 month the fatality was 1.6% in the rtPA group and 3.0% in the placebo group. Treatment with rtPA did not reduce the number of patients with normal ECGs from developing MI (28% rtPA vs 24% placebo). Treatment with rtPA was associated with significantly more bleeding episodes, the vast majority of which were clinically minor. The risk of all strokes in the rtPA group was similar to that in the placebo group (1.1% vs 1.0%). Treatment with rtPA was unaccompanied by either allergic or hypotensive episodes, and, among rtPA treated patients, there was no increase in clinically important ventricular dysrhythmias. Neither age nor time from onset of symptoms reduced the benefit from rtPA.

Aged↗
PubMed1988

Trial of tissue plasminogen activator for mortality reduction in acute myocardial infarction. Anglo-Scandinavian Study of Early Thrombolysis (ASSET).

13,318 patients admitted to fifty-two coronary care units with suspected acute myocardial infarction were considered for inclusion in a double-blind study comparing recombinant tissue-type plasminogen activator (rt-PA) 100 mg plus heparin with placebo plus heparin. 8307 (62%) were excluded, mainly because their symptoms had begun more than 5 h previously, but all excluded patients were followed up at least until hospital discharge. 2516 patients were randomly allocated to rt-PA and 2495 to placebo. At one month the overall case fatality rates were 7.2% and 9.8%, respectively, a relative reduction of 26% (95% confidence interval 11-39%). 6.3% of patients given rt-PA had a bleeding complication (1.4% major) compared with 0.8% given placebo (0.4% major). However, the incidence of stroke was similar--1.1% in the rt-PA group and 1.0% in the placebo group. Subset analysis showed that patients who had a normal electrocardiogram (ECG) at the time of randomisation (17.5% of the whole trial population) had a low case fatality rate (1.6% in those given rt-PA compared with 3.0% in those given placebo). In those with an abnormal ECG at entry, rt-PA was associated with a 24.5% relative reduction in 1 month fatality (95% confidence interval 9-37%).

Adolescent↗
PubMed1988

A comparison of planar and tomographic imaging of the myocardium using 99Tcm-t-butyl isonitrile.

Oblique reconstruction tomography for stress imaging of 99Tcm-t-butyl isonitrile was performed. Oblique reconstructions, transaxial reconstructions and conventional planar images were reported by three observers. These reports were compared in 12 patients with suspected heart disease, using ECG, cardiac enzymes and coronary angiography to derive diagnostic standards. Oblique reconstruction tomography gave better agreement between the observers and more accurate diagnoses than either transaxial reconstruction or planar imaging.

Adult↗
PubMed1988

Amlodipine and captopril in moderate-severe essential hypertension.

The therapeutic usefulness of adding once-daily amlodipine (10 mg) for four weeks in moderate-severe hypertensive patients uncontrolled on low dose captopril (25 mg twice daily) alone was studied in 29 patients in a double-blind, placebo-controlled two-way crossover comparison. Once daily amlodipine was shown to be an effective antihypertensive drug when combined with captopril. The amlodipine minus placebo differences in mean changes from captopril baseline values were: -18/-12 mmHg and -20/-12 mmHg for supine and standing systolic/diastolic pressures (P less than 0.001 for all four pressure variables). The combination was well tolerated, and no patient discontinued therapy. Five patients experienced ankle oedema and four patients reported flushing while receiving amlodipine/captopril.

Adolescent↗
PubMed1987

Post-exercise hypotension: the effects of epanolol or atenolol on some hormonal and cardiovascular variables in hypertensive men.

1 Eight men with primary hypertension were treated for 3 weeks with placebo, epanolol (200 mg or 400 mg), or atenolol 100 mg in a randomised cross-over study. Each active treatment period was preceded by a 3 week placebo treatment period and both investigators and subjects were blind to the active drug sequence. 2 At the end of each period, measurements were made of resting cardiovascular (heart rate, blood pressure, forearm blood flow) and biochemical variables (plasma renin, angiotensin II, aldosterone, adrenaline, noradrenaline, vasopressin, sodium and potassium concentrations and osmolality). Responses to exercise (including gas exchange, sweat rate, and ratings of perceived exertion) and the reflex cardiovascular adjustments to distal body subatmospheric pressure were also assessed. 3 The reduction of exercise-induced tachycardia by epanolol 400 mg was comparable to that of atenolol. There was very little difference in the effects of atenolol or epanolol 400 mg on resting blood pressure, but in both cases blood pressures were usually significantly lower than with epanolol 200 mg. 4 Although each active treatment influenced the renin-angiotensin system and circulating levels of catecholamines, the exercise-induced reduction in blood pressure was unaffected. Thus, the hypotensive effects of pharmacological and non-pharmacological interventions were additive.

Adrenergic alpha-Antagonists↗
PubMed1986

Trial of early nifedipine in acute myocardial infarction: the Trent study.

Over 30 months 9292 consecutive patients admitted to nine coronary care units with suspected myocardial infarction were considered for admission to a randomised double blind study comparing the effect on mortality of nifedipine 10 mg four times a day with that of placebo. Among the 4801 patients excluded from the study the overall one month fatality rate was 18.2% and the one month fatality rate in those with definite myocardial infarction 26.8%. A total of 4491 patients fulfilled the entry criteria and were randomly allocated to nifedipine or placebo immediately after assessment in the coronary care unit. Roughly 64% of patients in both treatment groups sustained an acute myocardial infarction. The overall one month fatality rates were 6.3% in the placebo treated group and 6.7% in the nifedipine treated group. Most of the deaths occurred in patients with an in hospital diagnosis of myocardial infarction, and their one month fatality rates were 9.3% for the placebo group and 10.2% for the nifedipine group. These differences were not statistically significant. Subgroup analysis also did not suggest any particular group of patients with suspected acute myocardial infarction who might benefit from early nifedipine treatment in the dose studied.

Adolescent↗
PubMed1985

Effect of aspirin and indomethacin on exercise-induced changes in blood pressure and limb blood flow in normal volunteers.

To evaluate the possible role of prostaglandins in exercise-induced changes in blood pressure and limb blood flow we have compared the effects of aspirin and indomethacin in a double-blind placebo controlled study in a group of normal volunteers. Nine men undertook treadmill exercise after pretreatment with placebo, aspirin and indomethacin. Indomethacin caused a greater increase in systolic blood pressure during exercise than aspirin (p less than 0.05) and a smaller fall in diastolic pressure than either placebo or aspirin (p less than 0.02 and p less than 0.01). Compared with placebo both aspirin and indomethacin attenuated to a similar degree the increase in calf blood flow (p less than 0.05 and p less than 0.03) and the changes in forearm blood flow following exercise. These results suggest that although aspirin and indomethacin both inhibit prostaglandin production they have different effects on exercise-induced changes in blood pressure. They have, however, similar effects on limb blood flow.

Adult↗
PubMed1984

Post-exercise reduction of blood pressure in hypertensive men is not due to acute impairment of baroreflex function.

Two experiments were carried out in male subjects. In the first experiment heart rate and blood pressures were measured before, during and for 90 min after a 50 min period of intermittent exercise in seven hypertensive subjects. After exercise there was a marked reduction in systolic and diastolic blood pressures; this effect lasted throughout the 90 min observation period and was unaccompanied by tachycardia. In the second experiment heart rate and blood pressures were measured before and during the rest periods in a 50 min session of intermittent exercise in nine hypertensive and nine normotensive subjects. Following the first 10 min bout of exercise, resting blood pressures were significantly reduced in the hypertensive subjects; the reduction in blood pressure progressively increased following successive exercise periods. The normotensive subjects did not show a significant reduction in resting blood pressures until the fifth bout of exercise had been completed. In the second experiment also, the competence of baroreflexes was assessed by measuring cardiovascular responses to lower body subatmospheric pressure ( LBSP ) 30 min before and 30 and 60 min after exercise. The post-exercise reduction in blood pressure was not due to exercise-induced impairment of baroreflex mechanisms since the reduced blood pressure after exercise was well maintained during lower body subatmospheric pressure. Furthermore, after exercise, exposure to lower body subatmospheric pressure elicited greater increases in heart rate and forearm vascular resistance than were seen before exercise.

Adult↗
PubMed1984

The effects of acute or chronic ingestion of propranolol or metoprolol on the physiological responses to prolonged, submaximal exercise in hypertensive men.

We have studied the physiological responses to 50 min of intermittent, moderate exercise in hypertensive men after the ingestion of a single dose of placebo, propranolol or metoprolol, and also after 28 days treatment. In addition, subjective assessments of mood were made during the last 7 days of each period of chronic treatment. Heart rate and blood pressure, both at rest and during exercise, were significantly reduced by a single dose of propranolol or metoprolol; more marked effects were observed after chronic treatment. Ventilation and gas exchange during exercise were only slightly disturbed by single doses of propranolol or metoprolol, whereas chronic treatment had no effect. Perceived exertion scores were increased after a single dose of either drug, compared to placebo, and the effect of propranolol was greater than that of metoprolol. With chronic treatment there were fewer differences between the perceived exertion scores during exercise, although 'leg' fatigue remained greater after propranolol than after placebo. Sweating from the forehead during exercise was enhanced by a single dose of either beta-adrenoceptor antagonist, with propranolol having the greater effect. After chronic treatment the effect of propranolol was diminished, whereas the effect of metoprolol was maintained. Very few disturbances of mood were found after chronic ingestion of the beta-adrenoceptor antagonists.

Adult↗