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Biomedical subjects

J H Reiber

Publications and source records attributed to J H Reiber.

At least 163 records · Page 9Linked to original sources
PubMed1985

Quantitative angiography of the left anterior descending coronary artery: correlations with pressure gradient and results of exercise thallium scintigraphy.

To evaluate, during cardiac catheterization, what constitutes a physiologically significant obstruction to blood flow in the human coronary system, computer-based quantitative analysis of coronary angiograms was performed on the angiograms of 31 patients with isolated disease of the proximal left anterior descending coronary artery. The angiographic severity of stenosis was compared with the transstenotic pressure gradient measured with the dilation catheter during angioplasty and with the results of exercise thallium scintigraphy. A curvilinear relationship was found between the pressure gradient across the stenosis (normalized for the mean aortic pressure) and the residual minimal area of obstruction (after subtracting the area of the angioplasty catheter). This relationship was best fitted by the equation: normalized mean pressure gradient = a + b . log [obstruction area], r = .74. The measurements of the percent area of stenosis (cutoff 80%) and of the transstenotic pressure gradient (cutoff 0.30) obtained at rest correctly predicted the occurrence of thallium perfusion defects induced by exercise in 83% of the patients.

Angiography↗
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↗
PubMed1985

Values and limitations of transstenotic pressure gradients measured during percutaneous coronary angioplasty.

The pressure gradient across coronary stenoses is measured routinely during angioplasty. Due to the finite size of the angioplasty catheter within the stenotic cross section, the remaining luminal area is further reduced and the transstenotic gradient may be overestimating the "true" pressure drop. This "true" pressure gradient can be approximated from the mean coronary blood flow and the stenosis geometry from theoretical models. Goal of this study was to assess the values and limitations of the in vivo measurements of the pressure gradient versus the calculated values. Therefore, flow in the great cardiac vein was measured in 13 patients before and/or after angioplasty of a proximal left anterior descending stenosis, not filled by collaterals. The Poiseuille and turbulent contributions to flow resistance were determined from stenosis geometry assessed by quantitative coronary angiography. A fourfold increase in the luminal area (from 0.7 mm2 pre- to 2.8 mm2 post angioplasty) was associated with a fourfold decrease in the in vivo measured transstenotic gradient (from 59 mm Hg pre- to 13 mm Hg post angioplasty). The occlusion area and the measured gradient were linearly correlated: gradient = 69-17 X occlusion area (r = 0.76). However, as expected, the transstenotic gradient systematically overestimated the theoretical gradient calculated from the laws of fluid dynamics. A nonlinear relation was found between the calculated gradient P and the occlusion area As: P = 15 X As-2 (r = 0.87).

Angina Pectoris↗
PubMed1984

Assessment of percutaneous transluminal coronary angioplasty by quantitative coronary angiography: diameter versus densitometric area measurements.

Cineangiograms of 138 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) were analyzed with a computer-based coronary angiography analysis system. The results before and after dilatation are presented. In a first study group (120 patients), the severity of the obstructive lesions derived from the automatically detected contours was evaluated in absolute terms and in percent-diameter reduction. In a second group of patients, 18 coronary lesions were selected for their extreme severity and symmetric aspect before angioplasty as assessed from multiple views. In the second group, the densitometric percent-area stenosis was used to assess the changes in cross-sectional area after PTCA and was compared with the circular percent-area stenosis computed from the diameter measurements. Before PTCA, a good agreement exists between the densitometric percent-area stenosis and the circular percent-area stenosis. After PTCA, important discrepancies between these 2 types of measurements are observed. It is suggested that these discrepancies in results after PTCA can be accounted for by asymmetric morphologic changes in luminal cross section, which cannot be assessed accurately from diameter measurements in a single-plane view.

Absorptiometry, Photon↗
PubMed1984

Coronary artery changes 3 years after reimplantation of an anomalous right coronary artery.

In this paper we report the sequelae of a patient with an anomalous right coronary artery (RCA) originating from the pulmonary artery (PA) in association with a normal heart, operated upon at the age of 13 years. Three years after the end-to-side reimplantation of the RCA, with a rim of the PA, into the aorta, the surgical result has been evaluated by cineangiography. Before operation both coronary arteries were tortuous and increased in size. Afterwards the left coronary artery showed a normalized calibre, although the RCA remained tortuous with no decrease of the internal diameter. The notable postoperative changes in shape and size of the LCA may be due to the disappearance of the steal phenomenon. The lack of involutive changes in the RCA could be explained by its thinner wall. Left ventricular wall motion, evaluated under resting conditions and during an atrial pacing stress test, was found to be normal.

Adolescent↗
PubMed1984

Prediction of mortality in hospital survivors of myocardial infarction. Comparison of predischarge exercise testing and radionuclide ventriculography at rest.

The relative merits of resting ejection fraction measured by radionuclide angiography and predischarge exercise stress testing were compared for predicting prognosis in hospital survivors of myocardial infarction. Two hundred and fourteen survivors of myocardial infarction out of 338 consecutive patients with acute myocardial infarction were studied over a 14 month period. Hospital mortality was 13% (45 of 338) whereas 19 additional patients out of 214 died in the subsequent year (9%). High, intermediate, and low risk groups could be identified by left ventricular ejection fraction measurement. Mortality was 33% for nine patients with an ejection fraction less than 20%, 19% for 58 patients with an ejection fraction between 20% and 39%, and 3% for 147 patients with an ejection fraction greater than 40%. Mortality was high (23%) in 47 patients who were unable to perform the stress test because of heart failure (19) or other limitations (28). The patients could be stratified further into intermediate and low risk groups according to the increase in systolic blood pressure during exercise: six deaths occurred in 46 patients with a blood pressure increase of less than 30 mm Hg and two deaths occurred in 121 patients with an increase greater than or equal to 30 mm Hg. Maximum workload, angina, ST changes, and ventricular arrhythmias were less predictive than blood pressure changes. It is concluded that the prognostic value of radionuclide angiography at rest and of symptom limited exercise testing is similar. The latter investigation should be the method of choice since it provides more specific information for patient management.

Aged↗
PubMed1983

Influence of intracoronary nifedipine on left ventricular function, coronary vasomotility, and myocardial oxygen consumption.

The effect of intracoronary nifedipine on regional and global left ventricular performance, coronary vasomotility, and myocardial oxygen consumption is reported. Left ventricular pressures and volume indices of contractility and relaxation were simultaneously recorded in five patients without coronary artery disease. In these patients, nifedipine in the left main coronary artery not only delayed (+115 ms) anterior wall contraction but also slowed (3.5 vs 1.9 cm/s) and depressed it (-26%), resulting in a depression of global left ventricular ejection. This asynchrony and depression of regional contraction is considered to be responsible for the slowed isovolumic contraction and relaxation of the whole ventricle. In 10 other patients with coronary artery disease, coronary sinus blood flow and myocardial oxygen consumption were measured before and after intracoronary nifedipine. The observed decrease in myocardial oxygen consumption (-28%) depended primarily on a decrease in contractility and left ventricular performance. In a third study group of 12 patients with coronary artery disease, the effects of intracoronary nifedipine on the coronary vasomotility of 40 coronary segments (normal, prestenotic, stenotic, poststenotic) were quantitatively determined. Left ventricular haemodynamics and coronary sinus saturation were monitored while the cineangiograms were recorded before and after nifedipine. Nifedipine provoked vasodilatation of the normal (+10.3%), prestenotic, stenotic (+4 to 30%), and poststenotic (+16.4%) coronary segments, which persisted after the disappearance of its direct effects on the myocardium. This transient regional "cardioplegic" effect of nifedipine, associated with an increase in coronary blood flow, a reduction in myocardial oxygen consumption, and a vasodilatation of the epicardial vessels is likely to be beneficial during temporary coronary occlusion such as occurs in spasm or transluminal angioplasty.

Adult↗
PubMed1983

Active and passive coronary vasodilation after intracoronary and sublingual nitroglycerin.

Nitroglycerin is known to dilate epicardial coronary arteries. It is not known, however, to what extend pressure-dependent passive vasoconstrictive effects may counteract active vasodilation. Therefore, repeated coronary angiograms were performed in 100 patients under standardized conditions before (C) and after 0.16 mg nitroglycerin intracoronarily as well as after an additional 1.6 mg nitroglycerin sublingually. Coronary diameters were determined in stenotic and nonstenotic coronary artery branches. Aortic blood pressure and heart rate were monitored continuously. Aortic blood pressure decreased slightly after intracoronary injection from 146/70 mmHg (C) to 142/77 mmHg and decreased markedly after additional sublingual administration to 129/70 mmHg. Heart rate increased from 78 beats/min (C) to 79 beats/min after intracoronary injection and to 81 beats/min after sublingual administration. Diameters in nonobstructed coronary segments increased in proximal (+7%), medial (+10%), and distal (+12%) segments after intracoronary injection; after sublingual administration a more pronounced diameter increase was observed in all segments (proximal +12%, medial +13%, distal +14%). In obstructed coronary arteries, a stenotic dilation of more than 10% was found in 73% (58/80) after intracoronary injection, but only in 50% (40/80) of the patients after sublingual administration of nitroglycerin. The average diameter increase within coronary stenoses in all patients was 24% after intracoronary injection, but only 10% after additional sublingual administration. In conclusions dilation of epicardial coronary arteries occurs in nonstenotic and stenotic segments. In nonstenotic coronary arteries, there are additive vasodilative effects after intracoronary and sublingual nitroglycerin; in coronary stenoses, however, a maximal effect is achieved after intracoronary injection which is diminished after sublingual administration.

Adult↗
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

Contribution of dynamic vascular wall thickening to luminal narrowing during coronary arterial vasomotion.

The hypothesis has been developed that increased coronary artery vasomotor tone superimposed on a preexisting obstruction is a possible mechanism responsible for resting and exertional angina. In 18 patients (22 stenotic lesions), the maximal changes in coronary artery diameter (mm) induced by an ergometrine test followed by an injection of isosorbide dinitrate were assessed by a quantitative computer-based angiographic system. If we assume that there is no change in the length of the artery as the result of changes in its diameter, then at any point of the artery the area of the arterial wall on a transverse cross section of the vessel will be constant regardless of its state of its contraction or dilatation. As vasoconstriction occurs, the luminal diameter decreases proportionally more than the outer diameter of the vessel and the wall thickness increases. Using elementary geometric principles, we calculated and reconstructed the changes that might occur at the stenotic sites as the result of vasomotion acting on the entire coronary segment. From the reference diameter in the control state (Ri:3.7 +/- 1.1 mm) and after vasoconstriction (Ric: 3.3 +/- 1.0 mm) and the obstruction diameter in the control state (ri: 2.2 +/- 0.9 mm), the minimal obstruction diameter after vasoconstriction (ric: 1.0 +/- 0.8 mm) was derived using the following equation: ric2 = ri2 - Ri2 + Ric2. In four of 22 lesions, the decrease in diameter of the lumen of the normal vessel was fully translated to the stenotic point and the decrease in diameter at the stenosis was correctly predicted.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗