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Biomedical subjects

C J Slager

Publications and source records attributed to C J Slager.

At least 73 records · Page 4Linked to original sources
PubMed1987

Spark erosion of arteriosclerotic plaques.

For the recanalization of occluded arteries by means of plaque ablation an electrical technique, called spark erosion, has been developed. In vitro tests have shown that well-defined holes can be produced easily in fibrous, collagenous and lipid plaques, with minimal thermal side effects. As the method is not, by its nature, selective in vivo application will require an additional guidance technique to avoid arterial perforation. For this purpose, the potential use of tissue impedance as a sensing parameter has been tested. Main advantages of spark erosion are that it is a well controllable, low cost and highly effective tissue ablation technique.

Animals↗
PubMed1986

Effect of coronary occlusion during percutaneous transluminal angioplasty in humans on left ventricular chamber stiffness and regional diastolic pressure-radius relations.

The effect of repeated (3 to 10 second) and transient (15 to 75 second) abrupt coronary occlusion on the global and regional chamber stiffness was studied in nine patients undergoing angioplasty of a single proximal left anterior descending coronary artery stenosis. The left ventricular high fidelity pressure and volume relation was obtained before and after the procedure as well as during coronary occlusion, after 20 seconds (n = 9) and after 50 seconds (n = 5). During ischemia, there was an upward shift of the pressure-volume relation. The nonlinear simple elastic constant of chamber stiffness increased from 0.0273 +/- 0.017 before angioplasty (mean +/- SD) to 0.0621 +/- 0.026 after 20 seconds of occlusion (p less than 0.05) and 0.0605 +/- 0.015 after 50 seconds of occlusion (p less than 0.01). In five patients, the postangioplasty value remained higher than the control value, but at the group level the mean value (0.0529 +/- 0.037) was not statistically different. The regional stiffness was determined from the changes in the length of six segmental radii during diastole, from the lowest diastolic to the end-diastolic pressure. The regional constant of elastic stiffness was unaffected in the nonischemic zone. In the adjacent and ischemic zones, the regional stiffness was increased during occlusion (p less than 0.05). These regional abnormalities in diastolic function persisted at the time of postangioplasty measurements, 12 minutes after the end of the procedure. This suggests that recovery of normal diastolic function after repeated ischemic injuries is delayed after restoration of normal blood flow and systolic function.

Angioplasty, Balloon↗
PubMed1986

Quantitative assessment of regional left ventricular motion using endocardial landmarks.

In this study the hypothesis is tested that the motion pattern of small anatomic landmarks, recognizable at the left ventricular endocardial border in the contrast angiocardiogram, reflects the motion of the endocardial wall. To verify this, minute metal markers were inserted in the endocardium of eight pigs with a novel retrograde transvascular approach. Marker motion was subsequently recorded with roentgen cinematography and compared with the motion of the landmarks on the endocardial contours detected from the contrast ventriculogram with an automated contour detection system. Linear regression analysis of the directions of the systolic metal marker and endocardial landmark pathways yielded a correlation coefficient of 0.86 and a standard error of the estimate of 10.3 degrees. Landmark pathways were also measured in 23 normal human left ventriculograms. Normal left ventricular endocardial wall motion during systole, as observed in the 30 degrees right anterior oblique view, is characterized by a dominant inward transverse motion of the opposite anterior and inferoposterior walls and a descent of the base toward the apex. The apex itself is almost stationary. On the basis of these observations, a widely applicable model for the assessment of left ventricular wall motion is described in mathematical terms.

Animals↗
PubMed1985

Vaporization of atherosclerotic plaques by spark erosion.

An alternative to the laser irradiation of atherosclerotic lesions has been developed. A pulsed electrocardiogram R wave-triggered electrical spark erosion technique is described. Controlled vaporization of fibrous and lipid plaques with minimal thermal side effects was achieved and documented histologically in vitro from 30 atherosclerotic segments of six human aortic autopsy specimens. Craters with a constant area and a depth that varied according to the duration of application were produced. The method was confirmed to be electrically safe during preliminary in vivo trials in the coronary arteries of seven anesthetized pigs. The main advantages of this technique are that it is simpler to execute than laser irradiation and potentially more controllable.

Aged↗
PubMed1985

Assessment of short-, medium-, and long-term variations in arterial dimensions from computer-assisted quantitation of coronary cineangiograms.

A computer-assisted technique has been developed to assess absolute coronary arterial dimensions from 35 mm cineangiograms. The boundaries of optically magnified and video-digitized coronary segments and the intracardiac catheter are defined by automated edge-detection techniques. Contour positions are corrected for pincushion distortion. The accuracy and precision of the edge detection procedure as assessed from cinefilms of contrast-filled acrylate (Perspex) models were -30 and 90 micrometers, respectively. The variability of the analysis procedure itself in terms of absolute arterial dimensions was less than 0.12 mm, and in terms of percentage arterial narrowing for coronary obstructions less than 2.74%. Short-, medium-, and long-term variability measurements were assessed from repeated coronary angiographic examinations performed 5 min, 1 hr, and 90 days apart, respectively. For all studies the mean differences in absolute diameters were less than 0.13 mm. The variability in obstruction diameter ranged from 0.22 mm for the best-controlled study (medium-term) to 0.36 mm for the least-controlled study (long-term); variability in reference diameter ranged from 0.15 to 0.66 mm, respectively. It is concluded that the biological variations are a source of major concern and that further attempts toward standardization of the angiographic procedure are seriously needed.

Cineangiography↗
PubMed1984

Is nisoldipine capable of reducing left ventricular preload?

In ten anesthetized pigs, nisoldipine (2-4 micrograms X kg-1 X min-1), a calcium channel blocker structurally related to nifedipine, reduced left ventricular systolic pressure (40%) and systemic vascular resistance (35%), whereas maxLVdP/dt decreased by 20% and cardiac output was unchanged. Left ventricular end-diastolic volume (15%) and end-diastolic pressure (40%) decreased, while ejection fraction slightly increased (13%). In normal hearts, nisoldipine reduces left ventricular pre- and afterload, without a depression of myocardial contractility, which results in a more efficient emptying of the left ventricle.

Animals↗
PubMed1983

Use of the fluid column in a cardiac catheter for emergency pacing.

Given the not infrequent need for intracardiac pacemaking during intensive cardiac care, a new type of cardiac pacemaker has been designed and tested [1]. With this pacemaker the heart can be stimulated through the fluid column of any conventional catheter, provided it is filled with a 0.9% NaCl solution. This fluid column pacemaker (FCP) is of the "constant current" type. The FCP was tested in 37 animals, in 30 patients in sinus rhythm, and also in two critical patients. In addition to the pacemaker circuit, a special connector was designed, enabling a fast, effective, and safe contact between patient and pacemaker. The FCP is considered to be ideally suited for use in emergency cardiac pacing in intensive care units and other areas where sudden bradycardias may occur and where intrathoracic catheters are inserted for a variety of reasons.

Animals↗
PubMed1983

A new model for coronary thrombosis in the pig: preliminary results with thrombolysis.

A new model for the electrical induction of coronary thrombosis in the pig is described. In 35 out of 47 experiments (74%) a 100% occluding thrombus developed. In 16 experiments (34%), at least one episode of coronary spasm occurred at the site of electrical stimulation. Flow in the region of the left ventricle supplied by the thrombosed coronary artery decreased from 1.04 +/- 0.21 to 0.09 +/- 0.04 ml/min/g tissue (mean +/- SD). Histological examination showed that the lesion caused by the electrical current occurred through the arterial wall and was quite discrete, measuring a few millimetres in length. Scanning and transmission electron microscopy revealed that the occlusions were caused by typical platelet thrombi. Lysis of the thrombi by the intracoronary administration of porcine plasmin was successful in 15 out of 19 animals (79%). Preliminary results show that thrombolysis after 40 min occlusion restores flow to nearly base-line values, but does not improve regional function in the first 3 h.

Animals↗
PubMedDate not supplied

Early identification of patients at risk for significant left ventricular dilation one year after myocardial infarction.

We prospectively investigated criteria to identify patients in the early phase of acute myocardial infarction at risk for significant left ventricular (LV) dilation 1 year after myocardial infarction. In 54 patients receiving thrombolysis within 4 hours after onset of symptoms, the end-diastolic volume index (EDVI) and the end-systolic volume index were assessed by two-dimensional echocardiography initially (within 23 +/- 21 hours) and 1 year after myocardial infarction. After 1 year, LV dilation occurred in 51 patients (94%) and was significant (> mean normal value + 2 SDs) in 14 patients (26%). Significant univariate predictors (p < 0.05) for LV dilation were age, anterior myocardial infarction, initial EDVI and end-systolic volume index, enzymatic infarct size, LV end-diastolic pressure, and mitral regurgitation. No other variables obtained from clinical information, two-dimensional echocardiography, or angiography, including residual coronary perfusion or stenosis, had predictive value. The optimal multivariate predictive model was the combination of the initial EDVI and the enzymatic infarct size, which correctly predicted significant LV dilation in 12 of 14 patients and falsely in eight of 39 patients (sensitivity 86%; specificity 79%). Patients at risk for significant LV dilation 1 year after myocardial infarction were identified adequately 3 days after myocardial infarction by the combination of the initial echocardiographic assessment of EDVI and the enzymatic infarct size. Thus a simple method could facilitate the selection of patients for intervention after acute myocardial infarction.

Cardiac Catheterization↗
PubMedDate not supplied

Reference systems in echocardiographic quantitative wall motion analysis with registration of respiration.

Registration of respiration allows analysis at the end-expiratory phase and may thus favor the use of the fixed-reference system versus the floating-reference system in echocardiographic quantitative wall motion analysis. Analysis is performed on two-dimensional echocardiograms of 44 normal subjects, 38 patients with anterior myocardial infarction, and 17 patients with posterior myocardial infarction. Two different models for wall motion analysis are applied, each using the fixed-reference system and the floating-reference system, respectively. In patients with anterior myocardial infarction, the fixed-reference system indicates severe wall motion abnormalities at the anterior, septal, and apical walls, whereas the floating-reference system indicates less severe wall motion abnormalities almost equally at every wall. In patients with posterior myocardial infarction, the fixed-reference system indicates severe wall motion abnormalities at the posterior wall, whereas the floating-reference system indicates less severe wall motion abnormalities almost equally at every wall. These findings indicate that the fixed-reference system is superior to the floating-reference system in quantification of wall motion of end-expiratory two-dimensional echocardiograms.

Adult↗
PubMedDate not supplied

Quantitative echocardiographic analysis of global and regional left ventricular function: a problem revisited.

We recorded two-dimensional echocardiograms simultaneously with the respiration measurements of 20 normal subjects and 20 patients with anterior myocardial infarction. The apical long-axis and four-chamber views were quantitatively analyzed. Measurement variability of global ejection fraction and regional ejection fraction of 100 regions was calculated during inspiration and at end-expiration for two observers. To minimize variability, the endocardial contour was redefined and traced with an improved computer-assisted tracing system. Variability (absolute mean difference) between two beats at end-expiration was significantly less than during inspiration (p less than 0.05): for ejection fraction the variability at end-expiration was 3.4% and the variability during inspiration was 6.4% (mean, 54%; SD, 7%); for regional ejection fraction the variability at end-expiration was 11.8% and the variability during inspiration was 21.5% (mean, 56%; SD, 15%). Intraobserver and interobserver variability values of one beat at end-expiration for ejection fraction were 3.1% and 3.8%, respectively, and 9.5% and 12.8%, respectively, for regional ejection fraction. Variability in patients with myocardial infarction was comparable. This method of recording respiration and analyzing left ventricular function at end-expiration, with a new contour definition and tracing system, provides a measurement variability that is considerably less than that reported in previous echocardiographic studies and that is comparable to angiographic methods.

Adult↗
PubMedDate not supplied

Two-dimensional echocardiographic analysis of the dynamic geometry of the left ventricle: the basis for an improved model of wall motion.

To establish an appropriate echocardiographic model for wall motion analysis we first determined the precise dynamic geometry of the left ventricle during systole, as visualized by two-dimensional echocardiography. With the epicardial apex and the aortic-ventricular and mitral-ventricular junctions as anatomic landmarks, we quantitatively analyzed apical long-axis views in 61 normal subjects, 41 patients with anterior myocardial infarction, and nine patients with posterior myocardial infarction. Thoracic impedance registration allowed exclusion of extracardiac motion from the measurements. In normal subjects the epicardial apex moved outwardly only 0.6 +/- 0.3 mm (mean +/- standard error). Examination of 15 hearts fixed in formalin revealed apical myocardial thickness of 1.5 +/- 0.2 mm. These data suggest that the observed inward motion of the endocardial apex (4.1 +/- 0.7 mm) resulted from obliteration of the apical cavity as a result of inward motion of the adjacent walls. Translation of the base was considerable in normal subjects (14.1 +/- 0.4 mm) and decreased in myocardial infarction (9.1 +/- 0.5 mm, p less than 0.0001). Unequal shortening of the adjacent walls in anterior and posterior myocardial infarction caused basal rotation in the opposite direction (-9.1 +/- 0.8 degrees and 9.7 +/- 1.4 degrees, respectively, p less than 0.0001 versus that of normal subjects, -3.4 +/- 0.7 degrees). Long-axis rotation was not clinically significant (less than 1 degree). We conclude that during ventricular contraction the apex serves as a stable point, whereas the base translates toward the apex because of shortening of the adjacent walls. We then propose a model for analyzing regional wall motion from two-dimensional echocardiograms on the basis of these observations.

Adult↗
PubMedDate not supplied

Comparison of different methods to define a target volume for external beam radiation therapy of restenotic coronary arteries.

PURPOSE: Different methods have been described to define a target volume for the treatment of restenotic (stented) coronary arteries by external beam radiation therapy (EBRT). The purpose of this study was to explore two methods to define a target for such therapy, and to compare these with previously investigated methods. MATERIALS AND METHODS: The 3-D position of a stent throughout the cardiac cycle in the three major epicardial coronary arteries was measured in three patients by single-breathhold multislice spiral CT and breathhold biplane conventional X-ray angiography, both indexed in time with the ECG. The volume through which the stent traversed (STV) during the cardiac cycle was determined by use of displacement measurements. RESULTS: For multislice CT and biplane angiography, respectively, the mean STV was 1.23 cm(3) (range 0.65-2.22 cm(3)) and 2.81 cm(3) (range 1.60-4.99 cm(3)). The STV represented only a fraction of the whole heart volume in all patients, that is, equal to or less than 0.4%. CONCLUSIONS: Multislice CT and biplane angiography allowed the measurement of a relatively small potential target, that is the STV, for EBRT of restenotic stented coronary arteries. Both studied imaging modalities are instrumental for targeting the STV by highly conformal radiation therapy in case of restenotic stented coronary arteries.

Coronary Angiography↗