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Biomedical subjects

T R Evans

Publications and source records attributed to T R Evans.

At least 73 records · Page 4Linked to original sources
PubMed1986

The acute haemodynamic effects of nicardipine in patients with chronic left ventricular failure.

Nicardipine is a new slow channel calcium blocker. It has been shown to be effective in the treatment of hypertension and angina pectoris. Nine patients with mild to moderate left ventricular failure were given intravenous infusions of nicardipine and the haemodynamic effects measured. In patients receiving 20 mg of nicardipine, mean cardiac index rose to a peak 1.81 X min-1 X m-2 (64%) above the preinfusion level, stroke volume index rose by 12 ml X m-2 (35%) and heart rate rose by 16 beats X min-1 (20%). There was a significant fall in systemic vascular resistance of 50% manifested by a reduction of 22 mm Hg in systolic blood pressure (18%) and 18 mm Hg in diastolic blood pressure (22%). Pulmonary vascular resistance fell by 45%. Mean pulmonary artery pressure and capillary wedge pressure did not change significantly. This study suggests that concomitant mild to moderate left ventricular failure is not a contra-indication to nicardipine therapy in patients with angina.

Adult↗
PubMed1984

Long-term beneficial effects of endralazine, a new arteriolar vasodilator at rest and during exercise capacity in chronic congestive heart failure.

Hemodynamic measurements were made at rest and during submaximal and maximal exercise in 12 patients with chronic congestive heart failure before and after oral endralazine (EN). After acute assessment, patients received endralazine, twice daily, for a mean of 2.8 months, when hemodynamic measurements were repeated. The drug was withdrawn for 3 to 4 days and subsequently reintroduced. Three patients with greatly elevated pulmonary wedge pressures were assessed after 30 mg of isosorbide dinitrate, which was also chronically administered. Resting mean cardiac and stroke volume indexes increased by 44 and 33%, respectively (p less than 0.01), with concomitant reduction of the systemic resistance. This improvement was maintained on a long-term basis in 8 of the 11 surviving patients. Withdrawal and subsequent reintroduction of EN confirmed that there was worsening of left ventricular dysfunction in the other 3 subjects. Chronic but not acute therapy produced a modest reduction in wedge pressure. At maximal exercise, cardiac and stroke volume indexes increased by 29 and 18%, respectively (p less than 0.01), after EN; the duration of exercise increased in 7 of the 10 subjects after acute therapy and this was maintained on a long-term basis. Mean creatinine clearance increased by 34% (p less than 0.01). The results confirm that EN produces acute and long-term hemodynamic and functional improvement without tolerance in congestive heart failure.

Aged↗
PubMed1984

Investigation of left ventricular function by digital subtraction angiography.

Twenty five patients who had undergone conventional coronary arteriography and left ventriculography for suspected coronary artery disease had left ventriculography performed by digital subtraction angiography as outpatients; there were no complications requiring admission to hospital. A catheter was introduced percutaneously and positioned in the superior vena cava; 40-50 ml of contrast medium was injected at 16-18 ml/s. Left ventriculograms were recorded in the 30 degrees right anterior oblique projection. Diagnostic images were recorded in each case. Left ventricular wall movement was assessed as normal in nine patients, globally hypokinetic in 10, and aneurysmal in six. In each case there was agreement between the two methods. Ejection fraction varied between 17% and 78%. It is concluded that digital subtraction angiography provides a reliable assessment of overall left ventricular function and distinguishes between those patients with a potentially resectable lesion and those with global impairment of function.

Adult↗
PubMed1983

Acute hemodynamic effects of endralazine: a new vasodilator for chronic refractory congestive heart failure.

Invasive hemodynamic measurements were made in 10 supine patients with chronic refractory congestive heart failure (CHF) due to ischemic heart disease or cardiomyopathy before and after oral administration of a new arteriolar vasodilator, endralazine. In 9 patients, a 10 mg dose of endralazine produced maximal increases in cardiac and stroke volume indexes of 56 and 41%, respectively, with a 45% reduction in total systemic resistance. After a 5 mg dose of endralazine, cardiac index increased maximally by 38% and stroke volume index by 34%, with a 31% decrease in total systemic resistance. Mean arterial pressure decreased 11 +/- 4 mm Hg (mean +/- standard error of mean) with the 5 mg dose and 17 +/- 5 mm Hg after the 10 mg dose. There were no significant changes in the right atrial, pulmonary arterial, or pulmonary capillary wedge pressures. After administration of a single dose of endralazine, statistically significant hemodynamic changes were observed from 1 to 8 hours with peak responses at 3 to 4 hours. These observations suggest that endralazine has hemodynamic properties similar to those of its structural analog, hydralazine. However, endralazine metabolism is largely independent of the patients' acetylator status, and no cases of systemic lupus erythematosus have been reported after long-term oral administration. These findings suggest that endralazine may be an efficacious drug that is potentially safer than hydralazine in the treatment of chronic CHF.

Adult↗
PubMed1978

Clinical value of tests of sino-atrial function.

Sinus node recovery times and the premature atrial stimulus test were studied in 36 patients, seven with gross sinus node disease, 25 with possible sinus node disease and four with no clinical evidence of sinus node disease. The corrected sinus node recovery time proved of most value in predicting which patients needed and would benefit from permanent pacemaker implantation, though there was one false negative diagnosis and two patients with abnormal corrected sinus node recovery times were asymptomatic. The premature atrial stimulus test usually proved to be of no practical value once severe sinus node disease was present and, in the group of patients with suspected sino-atrial disease, only 13 of 25 graphs could be analysed due to gross "scatter" in the others. When patients with symptoms have unequivocal evidence of sino-atrial dysfunction, invasive study seems unnecessary. With lesser degrees of sino-atrial disease, premature atrial stimulation may provide confirmatory evidence; but when sinus arrhythmia, atrial escape beats, or more marked dysfunction are present, one is likely to encounter useless "scatter" graphs. In the absence of regular sinus rhythm on the ECG, overdrive sinus node suppression in the only invasive study worth attempting.

Adolescent↗
PubMed1976

"Torsade de pointes" initiated by electrical ventricular stimulation.

Four cases are described in which electrical stimulation of the right ventricle produced the ventricular arrhythmia known as "torsade de pointes". This arrhythmia has previously been described as classically occurring in the context of the chronic bradycardias, particularly when there is also hypokalemia and a long QT interval, being most frequently initiated by a ventricular extrasystole occurring relatively late during ventricular repolarization. One patient had suffered a recent anterior myocardial infarction and developed the arrhythmia during rapid pacing for atrial flutter, when the electrode catheter had inadvertently entered the right ventricle. In the other three patients the arrhythmia was produced during the ventricular extrastimulus test performed during routine diagnostic electrophysiological investigation.

Adult↗
PubMed1976

Continuous imaging of regional myocardial blood flow in dogs using krypton-81m.

The unique physical properties of the freely diffusible gas krypton-81 m allowed continuous imaging of regional myocardial blood flow in dogs when infused into the aortic root. Regional changes in myocardial perfusion related to transient coronary artery occlusion were demonstrated both as high resolution gamma camera images and as a quantitative strip chart record.

Animals↗
PubMed1975

Measurement of stroke volume from pulmonary artery pressure record in man.

Stroke volume was determined from the pulmonary artery pressure record by application of the pulse contour method. Pulmonary artery pressure records were obtained in 17 patients using a high fidelity catheter-tip pressure transducer and simultaneous measurements of cardiac output were obtained from indicator dilution curves. The formula used was SV = KP sa (i plus T s/Td) where Psa is the planimetered area beneath the systolic portion of the pulmonary artery pressure curve. Ts and Td are the durations of systole and diastole, and K is a constant. Stroke volume was altered by isometric handgrip exercise and/or pharmacological agents in 15 patients. Serial measurementswere made in 2 patients in acute pulmonary oedema after myocardial infarction. Comparison of a wide range of values of stroke volume by the pulse contour method with those obtained from dye dilution curves showed a good correlation (r plus 0.97, P smaller than 0.001) regression line y = 1.01 times - 0.47. Measurement of stroke volume from the pulmonary artery pressure contour is a technique of potential value in serial haemodynamic monitoring.

Blood Pressure↗
PubMed1971

Reliability of patient monitoring apparatus.

Assessment of a patient monitoring system used in a general medical intensive care ward showed that the blood pressure subsystem was unreliable. The method used in this study is discussed in relation to the clinical requirements of patient monitoring apparatus.

Blood Pressure Determination↗
PubMed1971

A review of experience operating a general medical intensive care unit.

From 18 months' experience of operating a four-bedded general medical intensive care unit a high staff-to-patient ratio was the most important factor in its success. Heavy capital spending does not appreciably reduce the importance of adequate numbers of trained staff, though patient-monitoring equipment can be useful and sometimes vital. As the scope for intensive care widens, the problems of clinical care become difficult, because no doctor is likely to be competent enough to provide for all categories of patients, and there is no intensive care equivalent of the general physician. Intensive care is likely to function best in a divisional specialist system of clinical care.

Acute Kidney Injury↗