To help determine if coronary angiography can predict the site of a future coronary occlusion that will produce a myocardial infarction, the coronary angiograms of 42 consecutive patients who had undergone coronary angiography both before and up to a month after suffering an acute myocardial infarction were evaluated. Twenty-nine patients had a newly occluded coronary artery. Twenty-five of these 29 patients had at least one artery with a greater than 50% stenosis on the initial angiogram. However, in 19 of 29 (66%) patients, the artery that subsequently occluded had less than a 50% stenosis on the first angiogram, and in 28 of 29 (97%), the stenosis was less than 70%. In every patient, at least some irregularity of the coronary wall was present on the first angiogram at the site of the subsequent coronary obstruction. In only 10 of the 29 (34%) did the infarction occur due to occlusion of the artery that previously contained the most severe stenosis. Furthermore, no correlation existed between the severity of the initial coronary stenosis and the time from the first catheterization until the infarction (r2 = 0.0005, p = NS). These data suggest that assessment of the angiographic severity of coronary stenosis may be inadequate to accurately predict the time or location of a subsequent coronary occlusion that will produce a myocardial infarction. (Circulation 1988;78:1157-1166
We investigated left ventricular (LV) early diastolic filling in 10 normal conscious dogs that had been previously instrumented to measure LV and left atrial (LA) pressures and three orthogonal LV internal dimensions. LV volume was calculated as a general ellipsoid. The pressure within a passive structure increases as it is filled. If myocardial relaxation is rapid enough to substantially aid LV diastolic filling, it may overcome this effect and cause LV pressure to fall despite an increase in volume. Thus, we defined the amount of LV filling that occurred while LV pressure was falling as relaxation filling, which is a measure of the importance of LV relaxation during early diastolic filling. The time constant of relaxation (T) was derived from the exponential fall of LV pressure during isovolumic relaxation. While LV pressure was falling early in diastole (the relaxation filling period), all three LV diameters increased. Autonomic blockade with hexamethonium (5 mg/kg) and atropine (0.1 mg/kg) reduced relaxation filling from 21 +/- 6% (mean +/- SD) to 12 +/- 3% of the stroke volume (p less than 0.01). The mean LA pressure also was significantly decreased (from 12 +/- 2 to 10 +/- 5 mm Hg, p less than 0.05), while the duration of the relaxation filling period and T were unchanged. Positive inotropic stimulation with dobutamine (10 micrograms/kg/min) shortened T without changing LA pressure. The maximum LA-LV pressure gradient, dV/dtmax, and relaxation filling all increased. Augmented preload produced by dextran infusion (500 ml/10 min) caused an increase in LA pressure (from 11 +/- 3 to 21 +/- 8 mm Hg, p less than 0.05) without altering T. This also increased the maximum LA-LV pressure gradient, dV/dtmax, and relaxation filling. Augmented afterload produced by methoxamine (10 mg/3 min i.v.) significantly increased LA pressure (from 9 +/- 4 to 15 +/- 10 mm Hg, p less than 0.05) and lengthened T (from 35 +/- 4 to 50 +/- 7 msec, p less than 0.05) and the duration of relaxation filling (from 36 +/- 5 to 44 +/- 9 msec, p less than 0.01) without altering the maximum LA-LV pressure gradient, dV/dtmax, or LV relaxation filling. Incremental changes in heart rate induced by atrial pacing (from 100-180 beats/min) resulted in progressive decreases in the time constant of LV relaxation and the duration of relaxation filling. The LA pressure was also decreased. There was no corresponding increase in the amount of active LV filling until the heart rate reached 180 beats/min. During all these interventions, T correlated with the duration of LV relaxation filling (r = 0.99. p less than 0.05). The amount of relaxation filling and dV/dtmax both correlated with the maximum LA-LV pressure gradient.(ABSTRACT TRUNCATED AT 400 WORDS)
Iohexol, a nonionic compound used as a contrast medium for angiography and as a measure of the glomerular filtration rate, was quantified in serum by capillary electrophoresis. Comparable results were obtained for serum samples deproteinized with acetonitrile or analyzed directly after 50-fold dilution with borate buffer. Serum samples were electrophoresed for 2.6 min at 12 kV in a borate buffer with detection at 254 nm and with 3-isobutyl-1-methylxanthine as internal standard. Acetonitrile deproteinization gave a greater sensitivity than did sample dilution. Between-run CVs were between 4.7% and 6.7%, and within-run CVs were between 2.5 and 3.2%. Analytical recoveries were 95-105%. Results of the method compared well with those by high-performance liquid chromatography (slope 0.96, intercept 0.005 g/L). This method demonstrates the potential of capillary electrophoresis for rapid and simple quantification of small molecules.
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