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Biomedical subjects

A Pitt

Publications and source records attributed to A Pitt.

At least 55 records · Page 3Linked to original sources
PubMed1983

Comparison of supine and erect bicycle exercise electrocardiography in coronary heart disease: accentuation of exercise-induced ischemic ST depression by supine posture.

Exercise-induced electrocardiographic ST depression was compared during supine and erect graded bicycle exercise in 43 patients with chest pain but no prior myocardial infarct; all had greater than or equal to 1 mm of ST depression during either erect or supine exercise; 16 had multivessel, 24 had 1-vessel and 3 had no coronary artery disease. Supine exercise used 4 minutes/stage and erect exercise used either 4 minutes or 3 minutes/stage with identical graded work loads for both postures. Chest pain occurred in 31 patients during erect and in 29 during supine exercise. ST depression was greater than or equal to 1 mm in 28 patients during erect exercise and in all 43 during supine exercise (p less than 0.001); mean maximal ST depression was 1.3 +/- 0.2 mm during erect and 2.6 +/- 0.2 mm during supine exercise (p less than 0.001). Maximal work load was higher during erect than supine exercise (745 +/- 32 versus 678 +/- 32 kpm/min; p less than 0.001). The accentuation of ST depression by supine posture was not attributable to the changes in heart rate, rate-pressure product or mean blood pressure during supine versus erect exercise. In the 10 patients who had 2 erect bicycle tests using work load durations of 3 and 4 minutes, the maximal ST depression was not significantly different (erect 3 minutes 1.3 +/- 0.5 mm and erect 4 minutes 1.4 +/- 0.4 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Incremental value of clinical assessment, supine exercise electrocardiography, and biplane exercise radionuclide ventriculography in the prediction of coronary artery disease in men with chest pain.

The incremental value of clinical assessment, exercise electrocardiography (ECG) and biplane radionuclide ventriculography (RVG) in the prediction of coronary artery disease (CAD) was assessed in 105 men without myocardial infarction who were undergoing coronary angiography for investigation of chest pain. Independent clinical assessment of chest pain was made prospectively by 2 physicians. Graded supine bicycle exercise testing was symptom-limited. Right anterior oblique ECG-gated first-pass RVG and left anterior oblique ECG-gated equilibrium RVG were performed at rest and exercise. Regional wall motion abnormalities were defined by agreement of 2 of 3 blinded observers. A combined strongly positive exercise ECG response was defined as greater than or equal to 2 mm ST depression or 1.0 to 1.9 mm ST depression with exercise-induced chest pain. A multivariate logistic regression model for the preexercise prediction of CAD was derived from the clinical data and selected 2 variables: chest pain class and cholesterol level. A second model assessed the incremental value of the exercise test in prediction of CAD and found 2 exercise variables that improved prediction: RVG wall motion abnormalities, and a combined strongly positive ECG response. Applying the derived predictive models, 37 of the 58 patients (64%) with preexercise probabilities of 10 to 90% crossed either below the 10% probability threshold or above the 90% threshold and 28 (48%) also moved across the 5 and 95% thresholds. Supine exercise testing with ECG and biplane RVG together, but neither test alone, effectively adds to clinical prediction of CAD. It is most useful in men with atypical chest pain and when the ECG and RVG results are concordant.

Adult↗
PubMed1983

Recent experience with transeptal catheterization.

We report our recent experience of 207 consecutive transeptal catheterizations performed in the following groups of patients: aortic valve disease in 152, mitral valve disease in 20, combined aortic and mitral valve disease in 11, hypertrophic obstructive cardiomyopathy in 11, assessment of prosthetic cardiac valves in nine, and four miscellaneous. Transeptal catheterization failed in 20 patients. There was no attempt to advance the transeptal catheter from the left atrium into the left ventricle in 18 patients, and failure to advance the transeptal catheter from the left atrium into the left ventricle occurred in 13 patients. Transeptal catheterization was achieved in a mean time of 9.7 +/- 4.6 SD min. There were no deaths, two major and four minor complications. We conclude that transeptal catheterization remains a useful technique that in experienced hands is both rapid and safe.

Adult↗
PubMed1983

Amiodarone therapy for life threatening or refractory cardiac arrhythmias.

Amiodarone was used in 40 patients with life-threatening or refractory tachyarrhythmias. Eighteen patients had recurrent ventricular tachycardia of whom 13 had suffered a cardiac arrest. Control has been excellent or good in 17 of these 18 patients during an average follow-up period of 10 months. A further 22 patients had supraventricular arrhythmias, including three with Wolff-Parkinson-White syndrome and paroxysmal atrial fibrillation. In 20 of these control has been excellent or good. The mean daily maintenance dose of amiodarone was 300 mg for patients with ventricular tachyarrhythmias and 200 mg for those with supraventricular tachyarrhythmias. Side-effects were common and included corneal microdeposits, skin rash and discolouration, alteration in thyroid function, and symptomatic bradycardia. Serious adverse effects were uncommon however and necessitated discontinuation of the drug in only two patients. Amiodarone did not appear to precipitate or exacerbate cardiac failure in any patient although many had severe left ventricular dysfunction. We conclude that amiodarone is effective in the therapy of life-threatening or refractory cardiac arrhythmias.

Adolescent↗
PubMed1982

Effects of verapamil on the electrophysiologic properties of the accessory pathway in patients with the Wolff-Parkinson-White syndrome.

The effects of intravenous verapamil on the electrophysiologic properties of the accessory pathway in 12 patients with symptomatic Wolff-Parkinson-White syndrome were studied using intracardiac electrical recordings. In 11 of the 12 patients it was possible to induce a reentrant supraventricular tachycardia with programmed atrial or ventricular pacing. After verapamil it was still possible to induce supraventricular tachycardia in 6 of the 11 patients; however, the mean cycle of length of the tachycardia increased from a control value of 330 +/- 20 ms (mean +/- standard error of mean) to 369 +/- 21 ms (p less than 0.05). Although verapamil had no significant effect on the anterograde refractory period of the accessory pathway as measured by the extrastimulus technique, it significantly increased maximal 1:1 atrioventricular (AV) conduction through the accessory pathway to incremental high rate atrial pacing in 10 of the 12 patients (control value 227 +/- 10 beats/min, value after verapamil 258 +/- 14 beats/min, p less than 0.001). In 4 patients in whom episodes of atrial fibrillation could be compared before and after verapamil, the drug decreased the average R-R interval from a control value of 327 +/- 27 ms to 282 +/- 28 ms (p less than 0.05) and decreased the shortest R-R interval between preexcited beats from a control value of 237 +/- 21 ms to 209 +/- 18 ms (p less than 0.05). It is concluded that in patients with symptomatic Wolff-Parkinson-White syndrome, verapamil may increase the ventricular response through the accessory pathway if atrial fibrillation occurs. This finding, which is of potential clinical significance, could not have been predicted from conventional anterograde refractory period estimations.

Adult↗
PubMed1982

Adverse interaction between beta-adrenergic blocking drugs and verapamil--report of three cases.

Three patients with ischaemic heart disease developed profound cardiac failure, hypotension and bradycardia during combined therapy with verapamil and beta-adrenergic blocking drugs. This clinical picture resolved completely with cessation of the combined therapy. Baseline left ventricular function, assessed by cardiac catheterisation or nuclear angiography, was normal in two patients and only mildly reduced in the other. Simultaneously administration of beta-adrenergic blocking drugs and verapamil may result in profound adverse interactions and should only be administered with great caution.

Adrenergic beta-Antagonists↗
PubMed1982

Right atrial thrombus simulating myxoma on M-mode echocardiography in a patient with pulmonary emboli.

Echoes from a right atrial mass in a patient with pulmonary embolism simulated a typical echocardiographic appearance of a right atrial myxoma. The patient was admitted with recurrent pulmonary emboli and had evidence of deep venous thrombosis on venography. M-mode echocardiography showed the appearance of a right atrial mass and right atrial angiography confirmed the presence of a mass prolapsing from right atrium into right ventricle. Subsequent 2-dimensional echocardiography and careful repeat M-mode echocardiography failed to demonstrate the mass suggesting embolisation to the lungs or lysis of the thrombus.

Adult↗
PubMed1982

Alpha-amanitin resistance in three wild strains of Drosophila melanogaster.

Three wild strains of D. melanogaster have been identified which are resistant to normally lethal levels of the fungal toxin, alpha-amanitin. Dietary LD50S for Oregon-R, the reference strain, and Ama-KTT, Ama-MI and Ama-KLM, the resistant strains, are 1.2, 35, 30 and 10 micrograms alpha-amanitin/vial, respectively. Resistance in all three strains is a digenic trait, being determined by two independently acting dominant genes, Ama-1, Ama-2, either of which is sufficient to confer resistance and which are located at approximately 18.8 and 100.7, respectively, on chromosome 3. Resistance to alpha-amanitin in all three strains is apparently not mediated by modification of RNA polymerase form II nor by failure of toxin transport or by toxin inactivation.

Amanitins↗
PubMed1982

Radionuclide angiographic assessment of global and segmental left ventricular function at rest and during exercise after coronary artery bypass graft surgery.

Left ventricular ejection fraction (LVEF) was measured by radionuclide angiography at rest and during supine bicycle exercise before and 3 months after coronary artery bypass graft surgery (CABG) in 20 patients with chronic stable angina. The right anterior oblique gated first-pass technique was used to assess LVEF response to maximal exercise (Wmax), while the left anterior oblique equilibrium-gated technique was used to assess LVEF and relative LV volume changes during graded submaximal exercise. Mean LVEF was unchanged at rest after CABG by both the first-pass (60 +/- 12% vs 60 +/- 12%) and equilibrium-gated (61 +/- 13% vs 62 +/- 13%) measurements. At Wmax, mean first-pass LVEF was significantly higher postoperatively than preoperatively (63 +/- 17% vs 53 +/- 17%; p less than 0.01) with a higher Wmax (750 +/- 182 vs 590 +/- 202 kpm/min; p less than 0.001) and higher rate-pressure product (302 +/- 59 vs 222 +/- 57 units; p less than 0.001). Similarly, equilibrium-gated LVEF levels during graded exercise, using stepwise regression analysis, were significantly higher postoperatively than preoperatively (p less than 0.001); at the highest graded work load, they averaged 63 +/- 19% postoperatively and 53 +/- 17% preoperatively, with higher work loads (500 +/- 190 vs 417 +/- 155; p less than 0.05) and higher rate-pressure products (271 +/- 55 vs 207 +/- 53; p less than 0.001). The increase in exercise LVEF after surgery was due to a marked decrease in the ratio, relative to resting values, of counts-based end-systolic volumes during submaximal exercise (preoperatively 1.91 +/- 1.04; postoperatively 1.14 +/- 0.46; p less than 0.01). The five subjects in whom LVEF decreased significantly during exercise postoperatively all had one or more blocked or stenosed grafts. This study documents, by two independent radionuclide techniques, an improved LVEF during exercise at an increased maximal work capacity and rate-pressure product 3 months after successful CABG.

Adult↗
PubMed1981

Indications and selection of patients for coronary artery bypass graft surgery.

Patients with chronic stable angina who have coronary artery bypass graft (CABG) surgery for the relief of symptoms are asymptomatic after one year in about 75% of cases. The indications for surgery in unstable angina are unclear. CABG has not shown to benefit patients with Printzmetal angina or who survived an episode of ventricular fibrillation. CABG for acute myocardial infarction is a contentious issue, buy an operative death rate of 5.2% with a late mortality of 1.1% has been reported. There is still debate about the usefulness of CABG in promoting life expectancy. Improved longevity is clearly seen in left main and triple vessel disease.

Angina Pectoris↗
PubMed1980

Isotope angiocardiography of the left ventricle.

Radionuclide imaging of the left ventricle is a recent innovative procedure requiring a gamma-camera interfaced to a computer. It has the advantages of being non-invasive and of allowing studies at rest and exercise. Left ventricular function may be assessed by viewing the images as an endless loop cine-display, or by quantitating the over-all and segmental functions. Validation studies comparing the technique with standard contrast angiograms have confirmed its reliability. Clinical studies have been undertaken in normal volunteers, and in patients. The technique will have increasing application in assessing the aetiology of chest pain, in selection of patients for cardiac surgery, and in determining the effects of interventions, such as drug therapy or coronary artery bypass surgery, on ventricular performance.

Adult↗
PubMed1980

Low dose heparin in the prevention of deep-vein thromboses in patients with acute myocardial infarction.

Patients with acute myocardial infarction of less than 48 hours duration were randomized into three groups. The "fully anticoagulated" group received heparin by intravenous infusion and warfarin sodium to maintain a whole blood clotting time of 30 to 90 minutes and a prothrombin index of 10% to 35%. The "low dose" heparin group received 500 units by intravenous infusion every 12 hours. The control group received no anticoagulants. The radioactive fibrinogen test was used to diagnose the presence of leg vein thromboses. The control group had an incidence of venous thrombosis of 29.7% compared with 13.9% in the low dose group and 11.3% in the fully anticoagulated group. Patients in the control group who had cardiac failure had a significantly higher incidence of venous thromboses (71.4%) when compared with patients not in failure (20.0%). In the two treatment groups no significant difference was observed in patients with and without cardiac failure. Patients with cardiac failure complicating an acute myocardial infarction have a high incidence of venous thromboses. Anticoagulants significantly reduce this incidence and low dose intravenous heparin is as efficacious as full anticoagulation.

Anticoagulants↗
PubMed1980

The effect of a selective beta adrenergic blocking agent on ventricular arrhythmias in the first year following myocardial infarction.

Fifty-five patients with recent acute myocardial infarction entered a single-blind cross-over trial to assess the effect of oral practolol 200 mg twice daily on the incidence and nature of ventricular arrhythmias in the first year following myocardial infarction. Patients had 24-hour Holter electrocardiogram tape monitoring at two weeks following infarction and at three-monthly intervals for one year. Twenty-six patients completed the full year of the trial with 12% of tape recordings technically unsatisfactory. A total of 46 periods of comparison of the action of practolol versus placebo therapy were available in thirty patients. Whilst receiving the selective beta adrenergic blocking agent, practolol, there was a significant reduction in the percentage of studied hours during which salvos of ventricular premature beats occurred (P < 0.025), however the percentage of patients in whom salvos were recorded was unchanged. The incidence of all other ventricular arrhythmias was not reduced in the practolol group. When the effect of practolol was related to the site of infarction, anterior or inferior, there was no significant reduction in the incidence of ventricular arrhythmias.

Adult↗
PubMed1980

The radionuclide assessment of left ventricular function using graded exercise in normal subjects.

In 20 normal volunteers, two minute equilibrium gated blood pool scanning (GBPS) was used to assess left ventricular function during rest and three stages of graded supine exercise on a bicycle ergometer. The three work loads were individualised for each subject from a previously performed exercise test and corresponded to mild, moderate and severe stress. The short imaging time was validated against standard GBPS. With exercise all subjects increased their left ventricular ejection fraction and in the majority, most of this rise occurred with the lowest work load. This change was predominantly due to a marked fall in end-systolic volume. The end-diastolic volume initially fell, then at peak exercise returned to baseline values. The major change in stroke volume occurred at peak exercise.

Adult↗