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Biomedical subjects

M L Simoons

Publications and source records attributed to M L Simoons.

At least 307 records · Page 17Linked to original sources
PubMed1978

ST-vector orientation and location of myocardial perfusion defects during exercise.

In 34 patients with chest pain the spatial orientation of the ST-vectors in the exercise electrocardiogramm 30 and 80 msec after the end of QRS were compared with the location of exercise induced local defects of myocardial uptake of 201Tl. The following results were obtained: 1. The sensitivity and specifity of myocardial perfusion imaging after exercise were the same as those of exercise electrocardiograms; 2. No relation could be observed between the location of reduced 201Tl uptake during exercise and the spatial orientation of the ST-vectors.

Angina Pectoris↗
PubMed1977

Quantitative analysis of exercise electrocardiograms and left ventricular angiocardiograms in patients with abnormal QRS complexes at rest.

The ECG changes during exercise are described in 71 patients with a previous anteroseptal or anterolateral infarction (ANT-MI) and in 73 patients with an old posterior or inferior wall infarction (INF-MI). Left ventricular angiograms in 95 patients yielded a good correlation between areas of dyssynergy and the QRS pattern at rest. The ST changes in patients with coronary artery disease and a normal ECG at rest, and in normal subjects, were oriented toward the right, posteriorly and superiorly. In patients with INF-MI and inferior wall dyssynergy, the ST changes were more inferiorly oriented. Anteriorly-oriented ST changes were associated with anterior wall or apical dyssynergy and with ANT-MI. Thus the spatial direction of the ST changes during exercise is related to three independent factors: those factors which cause the ST changes in normal subjects, the degree of myocardial ischemia in that particular case, and the extent of dyssynergic areas in the wall of the left ventricle.

Angiocardiography↗
PubMed1977

Estimation of the probability of exercise-induced ischemia by quantitative ECG analysis.

In order to improve the value of exercise tests for the detection of coronary artery disease (CAD) a system for on-line computer processing of the Frank lead exercise ECG was developed. Data were analyzed from 95 patients with CAD and 129 ostensibly healthy men. All subjects had a normal ECG at rest. Visual ECG interpretation during exercise yielded a sensitivity of 50% and a specificity of 95%. A large number of QRS and ST measurements were compared by discriminant function analysis in a group of 86 normal subjects and 52 patients (designated training group). Best results were obtained with a combination of two ST amplitudes from lead X: sensitivity, 85%, specificity, 90%. This was confirmed in a test group of 43 patients and 43 normal subjects. The results of the discriminant function were expressed as the likelihood ratio for an abnormal or normal ST segment at a given heart rate, a figure which provides a quantitative assessment of the degree of exercise-induces ischemia. This is a more realistic approach than classification into normal or abnormal since persons with and without CAD fall along the same continuous spectrum.

Adult↗
PubMed1975

Gradual changes of ECG waveform during and after exercise in normal subjects.

The directions and magnitudes of time-normalized P, QRS, and ST vectors, and other ECG parameters were analyzed during and after multistage exercise in 56 ostensibly healthy men aged 23 to 62. By selective averaging with a digital computer system a single representative beat was obtained from each stage. Measurements were taken from this beat. During exercise, the interval between the spatial maximum of the P wave and the onset of the QRS complex decreased while the magnitude of the P wave increased. The direction of the P vectors did not change. This pattern corresponds to the electrocardiographic manifestations of predominant right atrial overload. No significant changes in the QRS duration were observed. Also the magnitude and spatial orientation of the maximum QRS vectors remained constant. The interval between the QRS onset and the maximum spatial magnitude of the T wave shortened. The terminal QRS vectors and the ST vectors gradually shifted toward the right, and superiorly. The T magnitude lessened during exercise. In the first minute of the recovery period the P and T magnitudes markedly increased. Afterward all measurements gradually returned to the resting level. Mechanisms which may explain the observed ECG changes during and after exercise are discussed, including changes in the blood conductivity and intracardiac blood volume. Age did not contribute to the variance of the ECG measurements, but a significant reduction of this variance could be otained in some ST-segment measurements by relating them to heart rate with linear regression equations (P less than or equal to 0.05). Therefore it is expected that the sensitivity of the exercise ECG for detection of ischemic heart disease would be increased when heart rate dependent normal limits for ST-segment measurements are used. Different criteria should be employed for the interpretation of the ECG during and after exercise.

Adult↗
PubMedDate not supplied

Value of immediate coronary angioplasty following intracoronary thrombolysis in acute myocardial infarction.

A total of 533 patients with acute myocardial infarction of less than 4-h duration were enrolled in the multicenter randomized trial of intracoronary thrombolysis compared to conventional treatment. In two of the five participating centers, an additional coronary angioplasty immediately after thrombolysis was attempted in 46 patients. According to the treatment allocation and early and late patency of the infarct related vessel, patients were subdivided into three groups: conventionally treated (group A); successful coronary angioplasty following thrombolysis with persistent patent infarct related vessel (group B); and late patency of the infarct related vessel postthrombolytic therapy without angioplasty (group C). The highest global ejection fractions were observed in group B (54% +/- 10%) and group C (55% +/- 13%), while the lowest ejection fraction was found in group A (47% +/- 14%). The sequential changes in global ejection fraction from the acute to the chronic stage was + 4% (p = 0.05) in group B, while no significant changes could be demonstrated in group C. Furthermore, in the group successfully treated by angioplasty, the improvement in global ejection fraction was more pronounced and persisted up to three months after the intervention. This was supported by analysis of regional myocardial function of the infarct zone (+ 16% improvement, p = 0.01). The long-term clinical follow-up (median 24 months) of the patients successfully treated by combined procedure of thrombolysis and angioplasty (group B) was most favourable with a lower incidence of re-infarction (6%), and late coronary bypass surgery (13%) and/or (re)-percutaneous transluminal coronary angioplasty (3%) was performed less frequently. These results suggest that reperfusion may need to be supplemented by additional revascularization procedures in order to optimize the changes of obtaining full functional recovery and so to improve the prognosis.

Angioplasty, Balloon↗
PubMedDate not supplied

Passive immunization against cytomegalovirus in allograft recipients. The Rotterdam Heart Transplant Program experience.

We analyzed the results of passive immunization against CMV in 146 heart transplant recipients. The 65 seronegative recipients were prophylactically treated with anti-CMV immunoglobulins during and after the operation. Twenty-nine of these 65 patients received a seropositive donor heart. CMV infection occurred in 21/65 seronegative and in 40/81 seropositive recipients (difference not significant). The incidence of CMV infection in seronegative recipients of a CMV-matched donor heart (3/34) was significantly lower than in seronegative recipients of a positive donor heart and lower than in seropositive recipients, but no significant difference in infection rate was found between the two latter groups (18/29 vs. 40/81). Although primary infection more frequently resulted in CMV disease than secondary infection (11/21 vs. 10/40) no difference in incidence of disease was noted between seronegative and seropositive patients (11/65 vs. 10/81), nor was there a difference in the severity of symptoms following primary or secondary infection. There was a higher incidence of CMV disease in all patients who received a heart from a seropositive donor versus a seronegative donor. However, after transplantation of a heart from a seropositive donor the incidence (27%) of CMV disease observed in our passively immunized seronegative patients was the same as in the patients with naturally acquired seropositivity. There was no difference in the prevalence of coronary artery disease between patients with and without CMV infection or disease. We conclude that using the current passive immunization scheme the occurrence of CMV infection and disease is largely dependent on the serostatus of the donor.

Adolescent↗
PubMedDate not supplied

Optimal use of coronary care units: a review.

Patients at a low probability of acute cardiac pathology constitute a considerable proportion in many coronary care units (CCUs), such that physicians should consider more effective alternatives than CCU admission "to rule out myocardial infarction." In this article, strategies to increase the efficiency of managing patients with acute chest pain are reviewed. Algorithms aiming to improve the diagnostic accuracy of the general practitioner have been developed but require an electrocardiogram recorded at the home of the patient. Another method of triage encompasses the identification in the emergency room of the hospital of patients at a low probability of acute cardiac pathology by using predictive models that include laboratory assessments. A third strategy includes alternatives to CCUs for patients at a low risk of acute cardiac pathology, such as the creation of a simple observation unit. Finally, some investigators have sought to identify patients with good prognosis for early transfer from the CCU to lower levels of care. It is concluded that a combination of these approaches will be most efficient, and that the most appropriate choice will be determined by local circumstances.

Chest Pain↗
PubMedDate not supplied

Individual risk assessment for intracranial haemorrhage during thrombolytic therapy.

Thrombolytic therapy improves outcome in patients with myocardial infarction but is associated with an increased risk of intracranial haemorrhage. For some patients, this risk may outweigh the potential benefits of thrombolytic treatment. Using data from other studies, we developed a model for the assessment of an individual's risk of intracranial haemorrhage during thrombolysis. Data were available from 150 patients with documented intracranial haemorrhage and 294 matched controls. 49 patients with intracranial haemorrhage and 122 controls had been treated with streptokinase, whereas 88 cases and 148 controls had received alteplase. By multivariate analysis, four factors were identified as independent predictors of intracranial haemorrhage; age over 65 years (odds ratio 2.2 [95% Cl 1.4-3.5]), body weight below 70 kg (2.1 [1.3-3.2]), hypertension on hospital admission (2.0 [1.2-3.2]), and administration of alteplase (1.6 [1.0-2.5]). If the overall incidence of intracranial haemorrhage is assumed to be 0.75%, patients without risk factors who receive streptokinase have a 0.26% probability of intracranial haemorrhage. The risk is 0.96%, 1.32%, and 2.17% in patients with one, two, or three risk factors, respectively. We present a model for individual risk assessment that can be used easily in clinical practice.

Age Factors↗
PubMedDate not supplied

Planning, implementation, and process monitoring for prehospital 12-lead ECG diagnostic programs.

Prehospital 12-lead electrocardiographic (ECG) diagnostic strategies have been proven feasible and effective, provided they are designed and implemented properly. The authors of this communication have expended considerable time and effort in determining appropriate planning, implementation, and process monitoring necessary for successful implementation of a variety of prehospital diagnostic strategies. Many of these issues may not be obvious to an emergency medical services (EMS) director initiating a 12-lead ECG program. This level of attention to protocol development, education, training, inservice education, coordination of the health-care community, objective program assessment, monitoring and continuous quality improvement can serve as a model for other diagnostic EMS programs that may develop as an expanded role for EMS.

Electrocardiography↗
PubMedDate not supplied

Cardiologists' use of clinical information for management decisions for patients with unstable angina: a policy analysis.

Previous studies of management of unstable angina have revealed substantial differences in management between different hospitals, especially with respect to the use of coronary angiography. Physicians in a hospital with angiography facilities were more inclined to perform angiography than were physicians in hospitals without these facilities, even when differences in patient populations were taken into account. The authors compared the management strategies of 18 cardiologists, working in hospitals with and without angiography facilities, using a series of paper-case summaries, in order to assess the contribution of individual variability between physicians to practice differences. Physicians who worked in a hospital with in-house angiography facilities were more inclined to request angiography in similar case summaries, but the inter-individual variation exceeded the between-hospital variation. The variation in individual policies with respect to the decision to initiate coronary angiography could be associated with differences in weighting clinical information. These results confirm that practice variations may have many causes: variability in patients' characteristics, variations in how physicians react to these, differences in the availability of services, and variability in thresholds for action.

Angina Pectoris↗