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J Laurier

Publications and source records attributed to J Laurier.

12 recordsLinked to original sources
PubMed1999

Geometric features of coronary artery lesions favoring acute occlusion and myocardial infarction: a quantitative angiographic study.

OBJECTIVES: We sought to identify the angiographic predictors of a future infarction, to study their interaction with time to infarction, patient risk factors and medications, and to evaluate their clinical utility for risk stratification. BACKGROUND: Identification of coronary lesions at risk of acute occlusion remains challenging. Stenosis severity is poorly predictive but other stenosis descriptors might be better predictors. METHODS: Eighty-four patients with an acute myocardial infarction and a coronary angiogram performed within the preceding 36 months (baseline angiogram), and after infarction were selected. All coronary stenoses (from 10% to 95% lumen diameter reduction) at baseline angiogram were analyzed by computer-assisted quantification. Each of the 84 lesions responsible for the infarction (culprit) was compared with the nonculprit stenoses (controls) in the same patient. RESULTS: Culprit lesions were more symmetrical (symmetry index +15%; p < 0.001), had steeper outflow angles (maximal angle +4 degrees; p < 0.001), were more severe (percent stenosis +5%; p = 0.001) and longer (+ 1.5 mm, p = 0.01) than controls. The symmetry index and the outflow angles were the two independent predictors of infarction at three-year follow-up. Stenosis severity predicted only infarctions occurring within 1 year after angiography. In moderately severe stenoses (40% to 70% stenosis), stratification using the symmetry index and outflow angles accurately predicted lesions remaining free of occlusion and infarction at three-year follow-up. CONCLUSIONS: Better characterization of stenosis geometry might help to understand the pathophysiologic mechanisms triggering coronary occlusion and to stratify patients for improved care.

Coronary Angiography↗
PubMed1998

Comparison of ionic and nonionic low osmolar contrast media in relation to thrombotic complications of angioplasty in patients with unstable angina.

BACKGROUND: Acute complications of percutaneous transluminal coronary angioplasty (PTCA) are more common in patients with unstable coronary syndromes. The objective of this study was to prospectively determine the differences between ionic and nonionic low osmolar contrast media (LOCM) on potential risk of acute complications, particularly abrupt vessel closure, in patients with unstable angina undergoing PTCA. METHODS: A total of 210 patients with 278 lesions were randomized to receive either ionic or nonionic LOCM during PTCA. Quantitative coronary angiographic measurements and assessment of filling defects were made by experienced observers who were blinded to the type of contrast media used. RESULTS: The baseline clinical and angiographic characteristics, the immediate postangioplasty results, and clinical outcome were similar in both groups. Subacute recoil, defined as the difference between minimal luminal diameter (in millimeters) at 0 and 15 minutes after angioplasty, was significantly greater in patients receiving nonionic LOCM (0.17 +/- 0.36 mm vs 0.07 +/- 0.18 mm, p = 0.004). A filling defect abnormality attributable to dissection, thrombus, or a combination of the two was noted in similar proportions of the two groups. Although nonsignificant, more thrombus was noted in the nonionic group (21 of 129 vs 15 of 141, p = NS). The abrupt vessel closure rate was similar in the two groups and was only 1.9% in the first 24 hours. However, 17 (8.3%) patients had a repeat PTCA at 15 minutes (9 ionic vs 8 nonionic). CONCLUSION: In patients with unstable angina the choice of ionic or nonionic LOCM does not appear to significantly affect the clinical outcome of PTCA.

Adult↗
PubMed1996

Validation of coronary artery saphenous vein bypass graft diameter measurements using quantitative angiography.

The accepted value for reproducibility (true change) is two standard deviations (SD) of the differences between repeat measurements. It has been well established for coronary artery measurements using several different quantitative coronary angiography (QCA) systems, but it has not been well documented for saphenous vein grafts (SVG). The purpose of this study was to assess, using the Cardiovascular Measurement System (CMS), the measurement reproducibility of 24 vein grafts from 24 patients who had symptom-directed control angiography. Three equal graft segments were studied separately. Focal narrowings expressed in percent stenosis varied from 5 to 80% (mean 20.8 +/- 15.9%). The average minimum lumen diameter (MLD) was 3.07 +/- 0.81 mm and the average interpolated reference diameter (Ref. D) was 3.87 +/- 0.58 mm. We assessed the reproducibility of measurements obtained from two separate imagings of the graft in the same view but at least 20 minutes apart, near the beginning and at the end of the angiographic procedure (simulating baseline and end-trial examinations). The SD for differences in measurements (variability) was 0.183 mm for the MLD, 0.193 mm for the Ref.D, 0.184 mm for the mean diameter (Mean D) and 3.72% for the percent diameter stenosis (PDS). A reasonable true change cut-off for SVG measurements in our laboratory is > or = 0.4 mm for the minimum and mean lumen diameters, and > or = 10% for the PDS, when QCA is obtained with the QCA-CMS analytical software package.

Cineangiography↗
PubMed1993

Definition and measurement of restenosis after successful coronary angioplasty: implications for clinical trials.

Angiographic restenosis represents the most established measure of long-term outcome in most prospective clinical trials of coronary angioplasty (PTCA). The accuracy of assessing this endpoint is of utmost importance. The purpose of this article is to propose guidelines for the use of coronary angiography in this setting. First, the cineangiograms must be of high technical quality and performed in a high proportion of consecutive patients in follow-up under controlled study conditions that are reproducible. Second, computer-assisted quantitative coronary angiographic analysis is essential to minimize interobserver and intraobserver variability in stenosis measurement between successive studies. The following recommendations are presented for quantitative coronary angiographic analysis. Because biplane orthogonal views cannot always be performed both at baseline and at follow-up, stenosis measurement in the single-plane, most severe view often constitutes the most consistent and practical approach. The edge-detection method is still much more reproducible and accurate than densitometry and should be the preferred method of analysis. Measurement of reference diameter by the interpolated method is more objective than measurement by the user-defined approach and should be used whenever possible. Finally, measurements of absolute minimum diameter and percent diameter stenosis are both important in the assessment of outcome in clinical trials. Absolute minimum diameters are independent of variations in reference diameter, and the extent of reduction in minimum diameter between the immediate postangioplasty and follow-up angiograms, when expressed in dichotomous or continuous fashion, accurately defines the extent of vessel wall hyperplasia as an endpoint. On the other hand, vessel size corresponds in general to the size of myocardium subserved, and absolute changes do not take into account this physiologic fact. Therefore defining restenosis in terms of significant reduction in percent diameter stenosis is also a useful approach because of its clinical relevance. Thus clinical restenosis requires that a successfully dilated segment (< 50% diameter stenosis) show a > or = 50% diameter stenosis at follow-up angiography with, in addition, a meaningful degree of change, that is, exceeding 2 SDs of observer variability in quantitative measurements which, in our experience, translates into > or = 15% difference between early postangioplasty and follow-up angiography measurements.

Angioplasty, Balloon, Coronary↗
PubMed1992

Time course of left ventricular function after cardiac denervation in conscious dogs.

The time course of left ventricular (LV) function was compared in normal (N) and cardiac-denervated (CD) dogs over an 8-week period after instrumentation with solid-state LV pressure gauges and three pairs of ultrasonic crystals to measure LV long and short axes and wall thickness. Baseline LV systolic, end-systolic, and end-diastolic pressures did not differ in N and CD dogs. Heart rate was higher (p less than 0.01) and LV dP/dt was lower (p less than 0.05) in CD dogs. LV short-axis shortening, shortening fraction, velocity of circumferential fiber shortening, and ejection fraction were consistently lower (p less than 0.01) in CD dogs. With angiotensin II to increase LV afterload, relations of LV short-axis shortening, shortening fraction, velocity of circumferential fiber shortening, and ejection fraction to average LV systolic wall stress were shifted downward (p less than 0.01) in CD dogs at 2, 4, and 8 weeks. Relations of LV short-axis shortening to LV end-diastolic wall stress also differed (p less than 0.01) in N and CD dogs. Ganglionic blockade abolished differences in LV function between N and CD dogs during elevated LV systolic wall stress with angiotensin II. Thus, in conscious dogs, cardiac denervation results in a sustained reduction of LV function over a wide range of ventricular loading conditions.

Animals↗
PubMed1990

Computerized determination of lactate threshold during three modes of exercise.

The lactate threshold (LT) and corresponding exercise levels (rate-pressure product, workload, and exercise duration) have been proposed as objective quantitative parameters of functional capacity and cardiovascular status. The purpose of the present study was to compare three modes of exercise and to evaluate the influence of the body position, using a rapid lactate analyser and computerized determination of the LT. Eight healthy male subjects were studied. No significant difference was found between the LT measured during treadmill (1.55 +/- 0.22 mmol/l), upright bicycle (1.61 +/- 0.17 mmol/l), and supine bicycle (1.41 +/- 0.05 mmol/l) exercises. However, while exercise levels corresponding to the lactate threshold were similar in running and upright bicycling, the supine bicycle was associated with lower exercise duration and workload corresponding to the LT.

Adult↗
PubMed1989

Comparison by quantitative angiographic assessment of coronary stenoses of one view showing the severest narrowing to two orthogonal views.

Quantitative coronary arteriographic measurements were compared in 2 orthogonal views with the view that clearly showed the stenosis at its most severe in 147 lesions from 147 patients before, immediately after and 6 months after PTCA. In 21 of 147 patients (14%), 2 views could not be measured for technical reasons, even though all angiographers had tried to film 2 views. Lesion severity was slightly worse for 1 compared with 2 views (3.3 +/- 3.3% before PTCA, 3.6 +/- 3.8% after PTCA and 3.1 +/- 3.8% at follow-up). Similarly, minimal diameter was less for 1 view (0.11 +/- 0.09 mm before PTCA, 0.15 +/- 0.12 mm after PTCA and 0.13 +/- 0.09 mm at 6 months). When this systematic difference was taken into account, the 2 methods were within +/- 0.1 mm for minimal diameter in 288 of 376 measurements (77%) and within +/- 0.2 mm in 96%. For percent diameter stenosis the 2 methods were within +/- 5% in 90% and within +/- 10% in all but 2.7% (10 of 376). Thus, for routine clinical assessment, measurement of 1 view is adequate; for research purposes orthogonal views may sometimes be required.

Angiography↗
PubMed1988

Assessment of left ventricular function using digital angiography.

We have demonstrated that selective digital left ventricular angiography using small amounts of contrast material minimized both symptoms and hemodynamic alterations and provided good images for assessment of regional ventricular function. However, comparisons of ejection fraction (EF), end-systolic volume (ESV), and end-diastolic volume (EDV) from digital angiography, at 10 frames per second, with measurements derived from conventional angiography, showed only a fair correlation between the two methods. Using a new generation of digital equipment and an acquisition time of 30 frames per second, we studied the correlation between digital and conventional angiography in 29 patients with coronary artery disease for a wide spectrum of left ventricular functions. Ventricular volumes and EF were calculated by computer using the area-length method. The correlation coefficient (r) between both the methods was 0.93 for EF, 0.95 for ESV and 0.89 for EDV. Thus digital left ventricular angiography provides an accurate evaluation of left ventricular function and can with advantage replace conventional angiography for this purpose.

Adult↗
PubMed1984

Usefulness of digital subtraction left ventriculography in patients with ischemic heart disease: comparison with cineangiography.

Digital subtraction and computer enhancement of left ventriculography allow the injection of small amounts of contrast medium into the left ventricle. Image quality measurements of cardiac volumes, and ejection fraction and evaluation of regional wall motion were compared following digital subtraction and cine ventriculography in 30 patients undergoing coronary arteriography for suspected or proven ischemic heart disease. At concentrations of 13% to 19% (iodine contents: 2.0 to 5.0 g) meglumine sodium diatrizoate used for digital subtraction ventriculography, no alterations of ventricular pressures were noted; premature ventricular contraction and cineventriculography in 30 patients undergoing coronary arteriography for suspected wall motion by two independent observers showed complete agreement between digital and cineventriculography in 141 of 150 segments (94%), including 114 normal segments; digital ventriculography led to underestimation of four segments and to overestimation of five. Left ventricular ejection fraction and volumes calculated using both techniques correlated relatively well (ejection fraction: r = 0.86; end systolic volume: r = 0.88; end diastolic volume: r = 0.665). Thus, intraventricular injection of low concentrations of contrast medium provides good digital angiographic images and may eventually replace cine ventriculography for invasive assessment of left ventricular performance. However, ECG gating and shorter exposure times will be required for accurate measurement of ventricular volumes and ejection fractions.

Adult↗
PubMed1984

Comparison of digital and radionuclide left ventriculography in patients at risk from conventional left ventriculography.

In this study, two alternative methods of assessing left ventricular (LV) sequential wall motion and ejection fraction (EF) were used in 28 consecutive patients in whom an unstable clinical condition (unstable angina pectoris or severe LV dysfunction) precluded the use of high volume contrast cineventriculography. A new approach, direct small volume contrast digital ventriculography, was compared to radionuclide blood pool ventriculography considered as a "standard" and reliable technique. The qualitative analysis of regional LV contraction by three independent observers showed a complete agreement in 64% of segments studied in the left anterior oblique (LAO) projection and in 69% in the right anterior oblique (RAO) projection; a one-degree disagreement was observed in 13% and 19% respectively, and a discrepancy of two degrees or more in 23% and 12% respectively. Left ventricular ejection fraction calculated from both techniques correlated relatively well (r = 0.82). The radionuclide examination still remains the fastest, easiest and most objective way to appraise global LV function in high risk patients. However, optimal analysis of segmental wall motion requires invasive digital contrast left ventriculography. In future, a more general use of non-ionic contrast media including their intravenous injection and the advent of portable digital devices should permit their widespread use as a safe, rapid and reliable procedure even in the intensive care unit.

Adult↗