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Biomedical subjects

M L Simoons

Publications and source records attributed to M L Simoons.

At least 289 records · Page 16Linked to original sources
PubMed1983

Clinical validation of fully automated computation of ejection fraction from gated equilibrium blood-pool scintigrams.

A fully automated procedure for the computation of left-ventricular ejection fraction (EF) from cardiac-gated Tc-99m blood-pool (GBP) scintigrams with fixed, dual, and variable ROI methods is described. By comparison with EF data from contrast ventriculography in 68 patients, the dual-ROI method (separate end-diastolic and end-systolic contours) was found to be the method of choice; processing time was 2 min. Success score of dual-ROI procedure was 92% as assessed from 100 GBP studies. Overall reproducibility of data acquisition and analysis was determined in 12 patients. Mean value and standard deviation of differences between repeat studies (average time interval 27 min) were 0.8% and 4.3% EF units, respectively, (r = 0.98). We conclude that left-ventricular EF can be computed automatically from GBP scintigrams with minimal operator-interaction and good reproducibility; EFs are similar to those from contrast ventriculography.

Adult↗
PubMed1983

Hemodynamic effects of sulmazol (ARL-115 BS), a new vasodilator and positive inotropic agent, in patients with cardiogenic shock.

The imidazol-pyridine ARL-115 BS (sulmazol) has both positive inotropic and vasodilatory effects. Its hemodynamic effects were studied in 13 patients with shock after myocardial infarction. All patients required dobutamine or dopamine, while nine were treated with intra-aortic balloon counterpulsation. After a loading dose of 50 mg, sulmazol was administered at 50 mg/h followed by 100 mg/h during 30 or 60 minutes. At the highest dose of sulmazol, cardiac output increased from 4.3 +/- 1.1 to 4.9 +/- 1.5 1/min; systemic vascular resistance decreased from 1405 +/- 473 to 1228 +/- 439 dynes . s . cm-5, while pulmonary capillary wedge pressure decreased from 22 +/- 6 to 17 +/- 7 mm Hg. No changes occurred in heart rate or mean arterial pressure. The effect of sulmazol was greater than the effect of an increased dosage of dobutamine in five patients in whom this was studied. Episodes of supraventricular tachycardia occurred in two patients. No other side effects were observed. The hemodynamic changes caused by sulmazol favour its use in the treatment of acute cardiac failure, and cardiogenic shock.

Adult↗
PubMed1981

Toward the optimal lead system and optimal criteria for exercise electrocardiography.

To define the optimal lead system for exercise electrocardiography, data of the whole body surface potential distribution were analyzed in 25 normal subjects and in 25 patients with coronary artery disease at rest and during exercise. All patients had a normal electrocardiogram at rest. The sensitivity of the standard chest leads was 60 percent; it improved to 84 percent with the body surface map whereas both methods had a 100 percent specificity. On the basis of these data, and reports from other centers, it is concluded that a single bipolar lead from the right subclavian area to lead V5 is adequate in those laboratories that are restricted to testing subjects with a normal electrocardiogram at rest. In patients with a previous infarction or other abnormalities in the electrocardiogram at rest three (pseudo) orthogonal leads or several standard leads are necessary. Recommendations for optimal measurements from the exercise electrocardiogram are based on quantitative computer analysis of the selected leads in larger groups of patients. Best results were obtained with a combination of S-T amplitude, S-T slope and heart rate. The improvement in sensitivity from 50 percent with visual analysis to 85 percent with computer was similar to that obtained with body surface mapping. Changes of the P wave and QRS complex during exercise appeared to be of little diagnostic value. The pathophysiologic mechanisms that contribute to the changes of the electrocardiogram during exercise are discussed.

Adult↗
PubMed1981

The effects of drugs on the exercise electrocardiogram.

Changes in the exercise ECG caused by five different drugs are presented. Analysis of these changes indicate that these are related to the hemodynamic effects of the drugs, rather than to reduction of myocardial ischemia. Calcium antagonists (Verapamil) as well as drugs which reduce heart rate (Alinidine, Propranolol) do not change the relation between ST depression and heart rate in a given patient. Drugs which lower ventricular volume (Molsidomine, Nitroglycerine) reduce the amount of ST depression at the same heart rate during exercise.

Cardiovascular Agents↗
PubMed1978

Model studies on activation of the heart.

Multiple dipole models of activation of the heart, in combination with a model of the thorax as an electrical conductor relate the action of individual cells to features of the electrocardiogram. The models can be used to develop diagnostic electrocardiographic criteria for ventricular hypertrophy, myocardial infarction or conduction disorders. Criteria derived with the use of Holt, Barnard and Lynn's model proved to be superior to well-established empirical rules. Their approach restricts position, direction and polarity of the current dipole vectors in the model. In the Selvester model, and later in the Ritsema van Eck model, in addition to these restrictions time-constraints are imposed on the dipole activity. In a validation study of the Ritsema van Eck model activation of a beating dog heart is compared in detail with simulated activation in a computer replica of the same heart. Myocardial spread of activation is found to be stimulated correctly. Simulated spread of activation along the Purkinje fiber network however, differs considerably from reality. In apical regions excitation spreads in reality much faster than in the model, in basal regions much slower. The model can be improved by slowing endocardial excitation from apex to base with the time-course of activation. Further improvement is obtained by the use of a more detailed pattern of endocardial excitation, based on studies of endocardial excitation in opened ventricles. The model can predict the time-course of activation with an accuracy of 5% of total ventricular activation time.

Action Potentials↗