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Biomedical subjects

I Azancot

Publications and source records attributed to I Azancot.

At least 19 recordsLinked to original sources
PubMed1992

Improvement of digital coronary angiography: high resolution processing coupled with a real time functional synchronization procedure.

The use of Digital Subtraction Angiography in coronary applications is restricted by the difficulty in: 1. Obtaining a good resolution of the distal branches. 2. Avoiding, for the purpose of subtraction, the motion artifacts induced by artery and background displacement during the cardiac and respiratory cycles. 3. Preserving the dynamic vascular motion. 4. And storing the digital dynamic information on a permanent support. We used for this study an angiography system, based upon a high resolution 45 MIPS-32 Mbyte image processor, interfaced with a 2.75 Gbyte Winchester drive allowing the real time storage of either 30 frames/s in the 512*512*8 bits matrix or of 7.5 f/s in the 1024*1024*8 bits matrix. To preserve the most important dynamic informations on the basis of the 7.5 f/s maximal storage rate, we developed a synchronization device able to recognize in real time, from chronologic delays derived by using both ECG and Aortic Pressure curves, the functional End-Diastolic (ED) and the End-Systolic (ES) positions, even in the case of heart rates varying during the procedure. The ED and the ES images are stored together with the Mid-Systolic (MS), the 1/3-Diastolic (1/3D) and 2/3-Diastolic (2/3D) images. To establish the validity of this sampling method, which uses a reduced number of frames per cardiac cycle, 7200 coronary injections performed during 450 routine coronary angiographies were compared by two independent observers (A and B), using: first a Digital (D) 5 frames/cycle sequence, and secondly a cine Film (F) 50 frames/s sequence acquired immediately after the corresponding D injection. The D technique resulted in the best image and diagnostic quality, particularly when the F quality was estimated 'fair' or 'poor' by both observers, and in an important reduction on X-Ray doses. The visualisation of the sequential ED, MS, ES, 1/3D and 2/3D frames gives the possibility: 1. of saving the dynamic information, as a regular sample of functional images can be displayed with a cine loop technique. 2. of facilitating cardiac synchronized subtractions. 3. of reducing the amount of frames per cycle, thus allowing an important reduction of X-ray doses and the digital and permanent storage of the most important cardiac cycles.

Angiography, Digital Subtraction↗
PubMed1992

Left ventricular regional dysfunction induced by intracoronary papaverine in patients with isolated stenosis of the left anterior descending coronary artery.

Intracoronary papaverine was administered to eight subjects with normal coronary arteries and to nine patients with single-vessel disease of the left anterior descending coronary artery. All patients had normal left ventricular function at baseline. After papaverine, global and regional ventricular function were unchanged in the normal group. In patients with left anterior descending coronary artery stenosis, intracoronary papaverine resulted in significant wall motion abnormalities and decrease of ejection fraction (from 65 +/- 6% to 54 +/- 9%, p less than 0.01). A full spectrum of responses was observed, however, in these patients, some having almost no change of regional wall motion while others had large anterior dyskinesis. No relationship was found between the severity of the stenosis and the amount of regional dysfunction induced by intracoronary papaverine. These data demonstrate the lack of relationship between the angiographic severity of a stenosis and its impact on left ventricular segmental contraction. This suggests that techniques aimed at producing wall motion abnormalities by means of coronary anterior vasodilation may not be recommended as first-line strategy for the detection of patients with coronary artery disease.

Constriction, Pathologic↗
PubMed1988

[Quantitative analysis of ventricular volumes by digital two-dimensional echocardiography].

The purpose of this study was to assess the usefulness of digital enhancement of two-dimensional echocardiographic images by cardiac cycle-synchronized summation and digital manipulation of the resulting images. We developed a system which provides for: (1) real-time storage of end-diastolic and end-systolic cardiac cycle images irrespective of rhythm variations; (2) exclusion from summation of end-diastolic and end-systolic images altered by respiratory movements or transducer displacements; (3) performance on the resulting images of various mathematical operations (3*3 convolutions, colour scale-guided manipulation of grey shades); (4) performance of complex mathematical calculations from the extracted edges including, in particular, reconstruction of ventricular volumes by Simpson's crossed method from a transverse and an apical section or from two apical sections. This method was used to collect echocardiographic images from 32 patients who had undergone left ventricular quantitative angiography during the same week. Qualitatively, digital enhancement of two-dimensional echocardiographic images undoubtedly facilitated the identification of endocardial edges and reduced image noise, notably in patients whose ventricular edges were virtually unrecognizable by any other method. Moreover, summation improved correlations with angiography and reduced the variability of quantitative ventricular volume assessment. Finally, the ease and rapidity with which this "real-time" system can be used enables quantitative analysis of left ventricular function to be routinely carried out.

Adult↗
PubMed1985

Relationships between single-vessel coronary artery obstructions and wall motion dysfunction analyzed by four computer-based methods.

We analyzed regional wall motion in 238 patients by using cineangiograms recorded in the 30 degrees right anterior oblique projection. The sample was divided into three groups: a normal group (n = 71), a group with isolated obstruction of the left anterior descending coronary artery and previous anterior myocardial infarction (n = 85), and a group with isolated obstruction of the right coronary artery and previous inferior myocardial infarction (n = 82). Both anterior and inferior groups also had motion abnormality within the corresponding anterior or inferior wall as judged by the qualitative analysis of cineangiograms. Four quantitative methods were compared: a long axis method and a center of mass method using internal reference systems, a method derived from the Stanford model and an area-based method using external reference systems. Normal regional values were determined from the normal group to evaluate the specificity and sensitivity of the methods. The area-based method was the most sensitive in the anterior infarction group, whereas the center of mass method was the most sensitive in the inferior infarction group. We conclude that there is no evidence that any method, among those tested, is superior to others for every expected location of wall motion abnormality.

Adult↗
PubMed1985

Changes in left ventricular performance during chronic pressure or volume overload: importance of physical properties of the arterial system.

The present study was aimed at evaluation of changes in systolic and diastolic left ventricular function during chronic pressure of volume overload, in comparison with normal subjects. Sixty-two patients were included: group 1 was composed of 25 normal subjects, group 2 was composed of 20 subjects with essential hypertension, and group 3 was composed of 17 subjects with aortic regurgitation without congestive heart failure. Cardiac output, aortic and left ventricular pressures (micromanometers), ventricular volume and ascending aortic radius (cineangiography), ejection fraction (EF), mean velocity of fiber shortening (VCF), ventricular mass (m), and the ratio m/EDV (EDV, end diastolic volume) were determined. Also measured were maxima for end systolic pressure (ESP), end systolic stress (ESS), and end systolic volume (ESV) and radius (ESR), as well as the modulus of left ventricular chamber and muscle stiffness (method of Gaash et al.) (1) and characteristic impedance of the ascending aorta (Zc). In hypertensive patients, m and m/EDV were increased, as was the ESP/ESV ratio, whereas EF and VCF were not modified and the ESS/ESR was normal or sometimes decreased. The systolic "pump" function thus appeared to be increased, whereas the muscle function appeared normal or decreased. The moduli of left ventricular chamber stiffness and muscle stiffness were increased. Zc was increased because of a greater pulse wave velocity, although aortic radius was larger. A close relationship was found between Zc and the ratio m/EDV. In patients with aortic regurgitation, the increased left ventricular mass was closely related to the regurgitant fraction (RF). The m/EDV ratio was normal. EF was unmodified and VCF and the ESP/ESV ratio were decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1979

[Effects of the parenteral administration of trinitroglycerin on myocardial function, coronary flow and myocardial oxygen consumption in the coronary artery disease patient (author's transl)].

An angiographic study, combined with the determination of coronary flow (thermodilution) and of coronary arteriovenous difference was performed in 10 patients with coronary artery disease under basal conditions and following an infusion of trinitroglycerine. The following changes were noted under the influence of trinitroglycerine: significant fall in left ventricular telediastolic pressure (40%), telediastolic volume (18%), telediastolic strain (53%), mean aortic pressure (11%) and mean systolic strain (21%). Significant increase in ejection fraction (8%), mean shortening (Vcf: 22%) and thickening (Vep: 22%) rates. Significant fall in coronary flow (11%) without any change in coronary arteriovenous difference. Decrease in myocardial oxygen consumption parallel to the reduction in mean systolic strain. These results indicate that the essential mechanism of haemodynamic and metabolic action of trinitroglycerine is located at the level of "load", in particular "preload".

Adult↗
PubMed1979

Relationships between hemodynamic profiles and topography of acute myocardial infarction.

Initial hemodynamics were studied in 101 patients with acute myocardial infarction complicated by shock or left heart failure. 59 had anterior myocardial infarction (AMI); 42 had inferior myocardial infarction (IMI). Data were processed by univariate analysis and correspondence analysis. AMIs and IMIs were significantly different on conduction disturbances, heart rate, left ventricular filling pressure, mean pulmonary artery pressure and right ventricular function indices. Both patients and parameters were projected on the most meaningful factorial plane generated by correspondence analysis. This two-dimensional graphical representation showed that all the information was roughly distributed along the 2 orthogonal axes defining this plane. Survivors and nonsurvivors were fairly well separated along the first factorial axis (prognostic axis) which was highly correlated with both outcome and left ventricular function parameters. AMIs and IMIs were grossly separated along the second factorial axis (topographical axis) which was rather well correlated with location and right ventricular function parameters. These studies suggest that AMI and IMI hemodynamic profiles are modulated by the presence or absence of right ventricular dysfunction. Moreover right ventricular dysfunction may be held responsible of some lack of information about left ventricular function status.

Acute Disease↗
PubMed1978

[A simplified arteriographic analysis of systolic pressure and of the pressure-time index].

Systolic stress has been measured in 20 ms periods during ventricular ejection by monoplanar angiographic method, both under basal conditions and after infusion of trinitro-glycerine (TNG) in 8 coronary patients. None of them showed significant segmental contraction abnormality. No correlation was found between the corresponding values of mean systolic stress sigma and mean systolic pressure P, either under basal conditions (r=0.48) or after reduction of the load (r=0.24). On the other hand, values of sigma correlated closely with the corresponding values of the stress sigmas at the end of the isovolumic contraction phase, both under basal conditions (r=0.95) and after TNG (r=0.98. A similar correlation was found between the corresponding values of the peak of systolic stress and of sigmas both under basal conditions (r=0.94) and after TNG (r=0.96). Determination of sigmas is technically simple, and only requires the calculation of ventricular end-diastolic volume, together with measurement of end-diastolic thickness and aortic diastolic pressure. This simplified angiographic method is useful to express the determinants of myocardial energy using parietal stress values instead of intracavitary pressure values.

Angiography↗
PubMed1977

Hemodynamic evaluation of hypotension during chronic hemodialysis.

Hypotensive episodes occur frequently during hemodialysis; they are often sudden and difficult to prevent despite careful clinical control. Their etiology was studied by investigating the hemodynamic response of five patients submitted to ultrafiltration during their three first dialyses. A Swan Ganz catheter was inserted and left in position for 5 days. Simultaneous determination of cardiac output, mean pulmonary artery (PAP) and capillary and systemic arterial pressures were recorded. 10 hypotensive episodes were observed. In 3 patients in whom the first hypotensive episode occurred 10 minutes after the start of dialysis, there was a significant drop in PAP, cardiac index and stroke index while heart rate and peripheral resistance remained unchanged. Paradoxical bradycardia was observed. In 4 patients hypotension was observed more than one hour after initiation of dialysis. Before the hypotensive episode there was moderate elevation of heart rate and peripheral resistance and an insignificant reduction in PAP. Cardiac index and stroke index were diminished. The decrease in MAP was only 2 mm Hg. Hypovolemia is the most important factor in hemodialysis-induced hypotension but other factors such as vagal stimulation, autonomic neuropathy and osmotic disequilibrium can interfere with blood pressure control and trigger hypotension. Methods of preventing hypotension during dialysis, including the infusion of low molecular weight dextran, are discussed.

Adult↗
PubMed1974

[SHock states. 1].

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Hemodynamics↗