Quantitative coronary angiography: measurement of the "critical" stenosis in patients with unstable angina and single-vessel disease without collaterals

Quantitative angiographic assessment of proximal coronary artery stenosis was performed in 15 patients with consecutive presentations in two categories defined by clinical and angiographic criteria. Group 1 consisted of 10 patients who had new onset of refractory rest angina and ischemic ST-T changes, but no infarction, single-vessel coronary disease without collateralization, and normal left ventricular (LV) angiograms. Group 2 consisted of five patients who were similar to patients in group 1, but had subendocardial infarction (SEI). Quantitative coronary arteriography, using paired perpendicular angiographic views and digital computation, yielded statistically different lesion dimensions and hemodynamic predictions for the two groups. Minimum stenosis diameters were 0.88 +/- 0.14 (SD) and 0.64 +/- 0.08 mm, respectively, for groups 1 and 2. This corresponded to 72% and 78% diameter reduction and 92% and 95% cross-sectional area reduction for the two groups. These small dimensional differences among lesions in the two groups resulted in large differences in their hemodynamic impact as predicted from classic fluid mechanics theory. We conclude that there are characteristic lesion dimensions for the isolated "critical" stenosis in these selected patients with rest angina. Further small increases in lesions severity result in SEI. Certain practical applications and limitations of these observations are discussed.

Left ventricular volume during maximal supine exercise: a study using metallic epicardial markers

Changes in left ventricular (LV) volumes and ejection fraction between rest and maximal supine exercise were evaluated in 11 patients who had had four epicardial markers placed during coronary artery surgery. After calibrating marker distances with respect to volume (r = 0.92--0.99) over one cardiac cycle for each patient, regression equations were used to compute LV volume from marker measurements for beats before and during exercise. The response of the left ventricle to exercise and the extent of revascularization could not be predicted from resting LV volume or ejection fraction. Ten patients had normal resting end-diastolic volumes and eight had normal resting ejection fractions. With exercise, three had a rise in end-diastolic volume and four had a fall in ejection fraction. Graft patency was greater in the group with an unchanged or increased ejection fraction (86 vs 50%, P less than 0.05). Epicardial clip motion can be used to determine LV volumes and ejection fraction during supine maximal exercise in man. The revascularized ventricle with normal or nearly normal performance in studies done at rest responds by decreasing end-diastolic and end-systolic volume and by increasing the ejection fraction. Increases in volumes or decreases in ejection fraction reflect old myocardial damage from infarction, fibrosis or ischemia from incomplete revascularization.

Immediate effect of contrast medium injection on left ventricular volumes and ejection fraction. A study using metallic epicardial markers

The immediate effect of contrast medium injection on left ventricular (LV) volume, stroke volume (SV) and ejection fraction (EF) was evaluated from postoperative LV biplane cineangiograms of 10 patients with 4-6 epicardial markers placed at the time of coronary artery surgery. After calibrating marker distances with respect to volume (r = 0.97-0.99) over one cardiac cycle for each patient, regression equations were used to compute LV volume from marker measurements for beats prior to, during and following injection. End-diastolic volumes (EDV) prior to injection ranged from 93-263 ml and did not change significantly with injection. End-systolic volumes (ESV) showed a mean decrease of 7.3 ml by beat 7 following injection; this was of borderline significance. Similarly, there was no significant change of SV or EF until beat 7 when there were small but significant increases of 6.4 ml and 0.04, respectively. The injection of moderate amounts of contrast in man does not cause significant changes in LV volume or EF through the sixth post-injection beat.

Quantitative coronary arteriography: estimation of dimensions, hemodynamic resistance, and atheroma mass of coronary artery lesions using the arteriogram and digital computation

More accurate characterization of coronary artery lesions is needed for evaluation of short and long-term interventions in coronary disease. A method of segmental artery analysis has been developed to maximize the information obtained from coronary arteriograms. Coronary lesions are traced from two projected, perpendicular, 35 mm cineangiographic views and transmetted, in digital form, to a PDP 11/45 computer. Magnification and distortion of the image are compensated for in order to determine the actual vessel profiles, using the catheter and its location as a scaling device. The two views are matched; a spatial representation of the vessel centerline is constructed mathematically; and orthogonal vessel diameters are computed at increments along this centerline. Assuming an elliptical lumen, the absolute and percentage reduction in diameter and cross-sectional area in the stenosis are computed. More complex functions (integrated atheroma mass, Poiseuille resistance, and orifice resistance) are then calculated. The accuracy and variability of the different steps involved in lesion analysis have been determined. Dimensional accuracies of +/- 150 microns (SD) are feasible. Examples are given of patients with Prinzmetal's angina and with progressive coronary disease.

Analysis of wall dynamics and directional components of left ventricular contraction in man

The extent and rate of left ventricular wall thickening during systole has previously been shown to be a useful measure of regional ventricular function and to play an important role in the ejection of blood from the left ventricle. The relation among systolic wall thickening, the directional components of contraction, ejection fraction and force velocity measurements is therefore of interest in understanding the dynamics of contraction of the intact ventricle. This report describes a theoretical basis and method for using ventricular angiograms to quantify the separate contributions of longitudinal shortening, circumferential shortening and systolic wall thickening to overall ventricular performance in man. One hundred twenty-two patients with valvular, coronary or myocardial heart disease were studied with biplane angiocardiography during diagnostic cardiac catheterizations. The percent contribution of directional components to total work or power developed by a mid-wall equatorial element of myocardium was shown to be: longitudinal, 14 percent in normal and diseased ventricles; circumferential, 45 percent in normal, increasing to 55 percent in dilated ventricles (P less than 0.005); wall thickening, 40 percent in normal, decreasing to 31 percent in dilated ventricles (P less than 0.001). Thus, left ventricular contraction, which is expressed as systolic wall thickening, quantified separately from inward wall displacement due to mid-wall circumferential shortening, accounts for nearly half of segmental left ventricular work and power. The rate and extent of ventricular wall thickening correlated closely with ejection fraction (r = 0.92 and 0.95, respectively) and with velocity of circumferential shortening (r = 0.90 and 0.80, respectively). Previous models of ventricular and myocardial mechanics that include computations of mid-wall longitudinal and circumferential stress and strain do not appear to account for the large contribution of systolic wall thickening to the performance of the intact heart. Force-velocity relations as heretofore described may therefore be partial descriptors of myocardial function in the intact ventricle.

Quantitative measurement of left ventricular volumes in man from radiopaque epicardial markers

The distances between three or four radiopaque markers located on the left ventricular epicardial surface at the apex and in the region of the minor axes in 22 subjects showed close correlations with left ventricular chamber radii, length, volume and wall thickness determined from biplane angiograms over the range of stroke volume. The markers were previously placed during heart surgery. Regression equations relating the distances between epicardial markers and chamber volumes were used to predict volumes for other beats. There was close agreement of end-diastolic, end-systolic, and stroke volumes as determined by the angiographic and epicardial marker methods for premature atrial contraction beats and post premature contraction beats, and in studies performed during rest and exercise. Time-volume curves determined by the epicardial marker and angiographic methods were similar. It is concluded that epicardial marker measurements can be used to quantitate beat-to-beat left ventricular chamber volume and dimension changes.