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Biomedical subjects

D J Coltart

Publications and source records attributed to D J Coltart.

At least 91 records · Page 5Linked to original sources
PubMed1980

Quantitation of ventricular arrhythmias.

Development of a computer-aided system for routine quantitation of spontaneously occurring ventricular arrhythmias in isolated perfused hearts is described. The technique essentially involves statistical treatment of electrocardiographic data to determine beat interval standard deviations. To minimize standard deviations arising from changes in heart rate, mean R-R intervals and standard deviations of 1-min sets of data are grouped and subjected to one-tailed analysis of variance. Residual standard deviation (derived from the difference between total variation and between set variation) expressed as a percentage of group mean is utilized as the Rhythm Disturbance Unit. It is proposed that this system can be used to facilitate investigations into mechanisms underlying arrhythmogenesis and in addition may have potential application in the screening of anti-arrhythmic interventions.

Analysis of Variance↗
PubMed1979

A computerised dichromatic earpiece densitometer for the measurement of cardiac output.

This study assesses a precalibrated dichromatic earpiece densitometer and microprocessor for the measurement of cardiac output by indocyanine green dye dilution. The measured cardiac output is compared with values of cardiac output simultaneously determined using a cuvette densitometer. The microprocessor computation of cardiac output agreed very closely with the cardiac output determined by manual calculation from the same dye dilution curves (standard deviation +/- 1.47%). The reproducibility of the earpiece densitometer (standard deviation +/- 5.2%) was virtually identical to that of the cuvette densitometer (+/- 5.3%). In a comparison of earpiece and cuvette densitometers for 60 measurements of cardiac output following pulmonary arterial injection of dye and for 50 measurements following femoral venous injection of dye, correlation coefficients were 0.83 and 0.78 and the standard deviations of the differences of simultaneous measurements were 7.2% and 8.3% respectively. The instrument offers an accurate reproducible and relatively noninvasive technique for measuring cardiac output.

Cardiac Output↗
PubMed1979

Pharmacological and clinical importance of narcotic antagonists and mixed antagonists--use in cardiology.

1 The treatment of pain of cardiac origin requires a knowledge of the haemodynamic action of the analgesic agents used. 2 The haemodynamic effects of morphine, diamorphine, pavaveretum, pethidine and pentazocine are reviewed. 3 Clinical experience with the new antagonist analgesic buprenorphine is reported. 4 These studies indicate that buprenorphine may be the agent of choice for the relief of severe pain in patients with unstable circulation.

Buprenorphine↗
PubMed1979

Echocardiographic findings in prolapsed aortic cusp with vegetation.

A patient with severe aortic regurgitation showed abnormal echoes in the left ventricular outflow tract compatible with aortic vegetation or flail aortic cusp. At operation, a pedunculated vegetation on a prolapsed aortic cusp was found. The case illustrates some of the pitfalls in the echocardiographic distinction of the two conditions.

Adult↗
PubMed1979

Thallium-201 myocardial imaging in assessment of results of aortocoronary bypass surgery.

Thirty-six patients were assessed by thallium-201 myocardial imaging before and after aortocoronary bypass operations and the results were compared with evaluation based on symptomatic assessment, exercise testing, and electrocardiography. After operation, the majority of patients were free from symptoms or symptomatically improved with increased exercise duration. Perioperative myocardial damage was shown in eight patients and myocardial ischaemia in 15 patients when assessed by thallium imaging during exercise. Thallium imaging proved more sensitive than electrocardiography in the demonstration of perioperative infarction and in the detection of postoperative ischaemia. Exercise electrocardiography may be misleading after aortocoronary bypass operations. Thallium imaging offers a simple, objective evaluation of the results of revascularisation procedures, throws light on the mechanisms of relief of angina by operation, and helps in the assessment of the patient whose progress is unsatisfactory after operation.

Adult↗
PubMed1979

Haemodynamic effects of disopyramide in patients after open-heart surgery.

Disopyramide phosphate was administered intravenously in a dose of 1.2 mg/kg body weight over one minute to nine patients after open-heart surgery and coronary artery bypass grafting. The haemodynamic changes were studied during and for 30 minutes after drug administration. Heart rate was unchanged throughout the study. During infusion the only significant changes were an increase in systemic blood pressure and systolic impedance signifying a direct increase in peripheral arterial resistance. Systemic blood pressure remained significantly higher for 10 minutes and systolic impedance for 30 minutes. Immediately after infusion max. dPower/dT, a measure of ventricular contractility, was significantly depressed for 15 minutes. Both cardiac output and aortic flow were significantly depressed for 30 minutes. DPTI/TTI, an estimate of subendocardial supply/demand ratio, showed an insignificant increase throughout the study. This study shows that intravenous disopyramide starts acting within 45 seconds of the start of infusion, directly increases peripheral arterial resistance, has a breif negative inotropic action, and does not reduce subendocardial blood flow.

Adult↗
PubMed1979

Cardiac anatomy viewed systematically with two dimensional echocardiography.

The details of three-dimensional cardiac anatomy are complex, and structure recognition is difficult in tomograms produced with recently developed two-dimensional ultrasonic sector scanners. This article presents a method we have found useful for systematic inclusion of most cardiac structures during such echocardiographic examinations. Orthogonal planes, aligned parallel and perpendicular to the long or major left ventricular axis, are obtained from each of three transducer positions on the body surface. Moving this X-Y image plane through the heart perpendicular to the plane (z axis) allows the viewer to integrate the images into a mental picture of the whole structure. The illustrations are oriented as they are displayed by ultrasonic sector scanners so they aid rapid recognition of cardiac structures.

Echocardiography↗
PubMed1978

Haemodynamic effects of buprenorphine after heart surgery.

The effect of buprenorphine on the cardiovascular system was examined in 11 patients during the period of reduced cardiac reserve after open-heart surgery. Within 10 minutes of giving the full analgesic dose (5 microgram/kg) intravenously the mean heart rate had fallen significantly by six beats/min. Although in two patients the mean arterial pressure fell by 24 mm Hg, there was no overall change in mean arterial pressure, cardiac output, or peripheral resistance. In a further six patients buprenorphine was used successfully as the sole analgesic after open-heart surgery. Buprenorphine appears to be safer than morphine for use in patients with reduced cardiac reserve and is of similar analgesic efficacy.

Adult↗
PubMed1978

Measurement of the circulatory effects of dobutamine, a new inotropic agent, in patients following cardiac surgery.

The use of an extractable aortic electromagnetic flow probe to provide a continuous on-line display of ascending aortic flow and cardiac output following open heart surgery is described. Utilizing this equipment, the hemodynamic actions of dobutamine and isoprenaline are compared in 14 patients immediately following cardiac surgery. The study confirmed an inotropic action produced by dobutamine at a heart rate 10 to 15 per cent lower than isoprenaline, with less peripheral vascular action. Arterial and coronary sinus blood analyses revealed little difference in the myocardial metabolic actions of either drug. Because inotropic drugs produce only relatively small increases in stroke volume in this group of patients, the rise in cardiac output caused by these agents is more dependent on the effects upon heart rate rather than improved myocardial contractile state and consequently dobutamine has little advantage over isoprenaline in this situation.

Adult↗
PubMed1978

Methods for the assessment of the effects of drugs on coronary blood flow in man.

The methods currently available for measurement of coronary blood flow in man are reviewed and their advantages and limitations discussed. Most of the techniques are invasive and involve cardiac catheterization. The least invasive isotope techniques are either not quantitative or involve expensive equipment not available in many centres. Two of the most suitable methods for assessing the effects of drugs on coronary flow are coronary sinus thermodilution and isotope washout curves using 133xenon or [125I]-iodo-antipyrine. The ideal technique for measuring coronary blood flow has yet to be developed.

Cardiac Catheterization↗
PubMed1978

Coronary artery ectasia--a variant of occlusive coronary arteriosclerosis.

In a study of 1000 consecutive coronary arteriograms, 12 patients (all men) had coronary artery ectasia. Ectasia was found most frequently in the circumflex or right coronary artery. Only 1 patient had ectasia in the left anterior descending coronary artery. In 11 patients, ectasia of one artery was associated with severe stenosis or occlusion of other vessels, typical of arteriosclerosis. Histology from an ectatic segment in one of this group showed changes of severe arteriosclerosis with extensive intimal fibrosis and destruction of the media. One patient had a mixed collagen vascular disease. Measurement of coronary sinus flow in 2 patients with coronary artery ectasia showed flows in the range of patients with non-ectatic coronary artery disease. At cardiac surgery flows down the graft to ectatic arteries were in the same range as in grafts to non-ectatic vessels. Patients with coronary artery ectasia should be anticoagulated.

Adult↗
PubMed1978

Coronary artery surgery: indications and recent experience.

The comprehensive experience of coronary artery surgery in a Cardiothoracic Unit over a 31-month period is reviewed. Hospital mortality for elective bypass grafting was 3.9% overall and 2.5% in those with good pre-operative left ventricular function. Major influences on hospital mortality were pre-operative left ventricular function, extent of coronary artery disease and extent of the surgical procedure undertaken in terms of number of aortocoronary grafts inserted, coronary endarterectomy and particularly concomitant valve surgery or aneurysm resection. Follow-up experience shows 74% of grafted patients to be symptom-free and 85% symptomatically improved one year after surgery with 70% symptom-free and 80% improved at two years. Early post-operative deaths appear related to early graft closure and recurrence of symptoms postoperatively to late graft closure or progression of coronary disease in the native circulation. The study provides a guide to the relative risks of coronary artery surgery for symptomatic coronary artery disease and expected symptomatic results in the early follow-up period.

Adult↗
PubMed1978

Pulmonary vein blood flow velocity in pulsus paradoxus.

The effect of inspiration on pulmonary vein blood flow velocity and forward pressure gradient from pulmonary vein to left atrium was studied in seven patients with chronic constrictive pericarditis, five of whom had clinically obvious pulsus paradoxus. Compared to patients without pericardial disease, where inspiration produced no change, patients with pericardial disease showed an inspiratory fall in the forward pressure gradient and forward blood flow velocity in the pulmonary veins on inspiration. The mechanism of pulsus paradoxus in these patients can be explained by incomplete transmission of the inspiratory fall of intrathoracic pressure to the left atrium.

Adult↗
PubMed1978

Use of electromagnetic flow probes to assess myocardial performance in man.

Aortic blood flow was measured in 14 patients by means of an electromagnetic flow probe placed around the ascending aorta during cardiac surgery. High fidelity left ventricular pressure was monitored directly, 8 different indices of left ventricular function were derived from these measurements, and compared. Peak aortic blood flow correlated with the conventional indices of left ventricular function derived from left ventricular pressure, but better correlations were obtained for the maximum rate of change of power with respect to time. The clinical advantage of the derivation of this index is small and for clinical purposes peak aortic blood flow and the maximum rate of change of flow provide indices of myocardial performance which are directly available from the instrument.

Adolescent↗