Both systolic and diastolic dysfunction have been described during pacing-induced ischemia, but the temporal sequence of systolic and diastolic impairment has not been established. Accordingly, 22 patients with coronary artery disease were paced at increasing heart rates and studied with simultaneous hemodynamic monitoring, electrocardiographic recording, and radionuclide ventriculography. In addition, with synchronized left ventricular pressure tracings and radionuclide volume curves, three sequential pressure-volume diagrams were constructed for each patient corresponding to baseline, intermediate, and maximum pacing levels. Eleven patients (group I) demonstrated a nonischemic response to pacing tachycardia without chest pain, significant electrocardiographic changes, or significant rise in left ventricular end-diastolic pressure (LVEDP) in the immediate postpacing period. These patients demonstrated a progressive decrease in LVEDP, end-diastolic volume, and end-systolic volume, no change in cardiac output or left ventricular ejection fraction, and a progressive increase in left ventricular diastolic peak filling rate and the end-systolic pressure-volume ratio. Pressure-volume diagrams shifted progressively leftward and slightly downward, suggesting both an increase in contractility and a mild increase in left ventricular distensibility. The remaining 11 patients (group II) exhibited an ischemic response to pacing tachycardia, with each patient experiencing angina pectoris, demonstrating greater than 1 mm ST segment depression on the electrocardiogram, and exhibiting greater than 5 mm Hg rise in LVEDP immediately after pacing. LVEDP, end-diastolic volume, and end-systolic volume in these patients initially decreased and then subsequently increased during angina, with no change in cardiac output but a decrease in ejection fraction. Left ventricular peak diastolic filling rate and the left ventricular end-systolic pressure-volume ratio both increased at the intermediate pacing rate but fell at maximum pacing. Pressure-volume diagrams for these patients shifted leftward initially, then back to the right, during intermediate and peak pacing levels, often with an upward shift in the diastolic pressure-volume relationship. LVEDP in group 1I was significantly higher than that in group I at the intermediate pacing level with no difference in end-diastolic or endsystolic volumes, suggesting decreased left ventricular distensibility in these patients before the onset of systolic dysfunction at the maximum pacing level. We conclude that an ischemic response to pacing tachycardia involves both systolic and diastolic dysfunction, with diastolic impairment often preceding systolic depression. Circulation 71, No. 5, 889-900, 1985

Subjective estimates of the angiographic severity of coronary artery stenoses show variability and inaccuracy. We therefore tested the accuracy of a newly developed computerized image analysis system for quantitating vessel diameter from cineangiograms. Fourteen cylindrical phantoms of known diameter were filled with contrast medium and filmed over a wide range of clinically relevant radiographic conditions in order to develop regression equations that related computer-derived to anatomic diameters. Computer measurements of vessel diameter were unaffected by vessel size, magnification, focal spot size, thickness of scattering medium, kilovolt peak, or location within the radiographic field, but a correction factor was necessary for a small but significant (p < .01) linear dependence on contrast medium concentration. The accuracy of computerized vessel diameter measurements ranged between + 59 and 137 ,u for all conditions except for rapid vessel motion and contrast medium concentrations of 50% or less meglumine diatrizoate (Renografin 76), both of which resulted in reduced accuracy as well as in the inability to locate lumen edges of vessels less than 1 mm in diameter.Circulation 68, No. 2, 453-461, 1983. SUBJECTIVE VISUAL ESTIMATES of percent stenosis of a coronary artery from cineangiograms have been shown to be characterized by a large interobserver variabilityl-3 and a descrepancy between angiographic and postmortem estimates of lesion severity has been noted in a number of studies. further objectify measurements of luminal dimensions. Although the reproducibility of various objective methods of diameter measurement has been studied, the accuracy of these measurements has received little attention.The fact that radiographic vessel images have edge gradients rather than sharply demarcated edges is not widely appreciated by angiographers. 14 Accurate diameter measurement is dependent on precise localization of the anatomic vessel edge within the edge gradient, and the magnitude of error in diameter measurements associated with arbitrary assignment of the vessel edge within the edge gradient may be considerable. A new method for computerized edge detection of coronary arteries from digitized 35 mm cineangiographic images with the use of specific algorithms to locate spatially disparate points within the edge gradient has been developed. The hypothesis that each of these points can be mathematically related to the anatomic edge was tested by filming contrast mediumfilled cylindrical phantoms over a wide range of cineradiographic conditions and comparing computer-derived measurements of diameter from digitized frames with the known diameters.

Nine patients with acute myocardial infarction had cardiac catheterization and intracoronary infusions of streptokinase 2.3 to 4.3 hours (mean, 3.5) after the onset of symptoms. Occluded coronary arteries were opened within approximately 20 minutes in all patients, but reocclusion occurred in one patient. The immediate effect of thrombolysis on myocardial salvage was assessed with the intracoronary injection of thallium-201. Improved regional perfusion, indicating myocardial salvage after recanalization, was observed in seven of the nine patients. One patient, who had also sustained a nontransmural infarction one week before, had no change after thrombolysis. In the ninth patient, recanalization of a coronary artery was followed by reocclusion and worsening of the myocardial-perfusion defect. Intracoronary thallium-201 studies two weeks and three months after streptokinase infusion in two patients were unchanged in comparison with scintiscans performed 1.5 hours after thrombolysis. These short-term observations suggest that recanalization of obstructed coronary arteries after intracoronary thrombolysis can salvage jeopardized myocardium, However, evaluation of the long-term effects of this procedure on survival and myocardial function will require controlled clinical trials.

Abstract. Twenty acute spinal cord injury patients were surveyed for deep venous thrombosis (DVT) by 1251 fibrinogen leg scanning, impedance plethysmography (IPG), and venography. Leg scanning was a more sensitive indicator of thrombotic events than IPG or venography. IPG was a reliable indicator of accumulated thrombosis. The incidence of DVT assessed by leg scanning alone was 100 per cent. Its occurrence as determined by either of the screening techniques was found to be considerably greater than those of previous reports.