The intrinsic limitations of coronary arteriography to predict the physiological effects of coronary obstructions are well known. Therefore, more direct assessments of the functional significance of coronary stenoses are becoming increasingly important. Study of contrast passage by electrocardiogram-triggered digital radiography has been proposed as a way of assessing changes in myocardial perfusion. The main problems in this approach are the limited time for motionless image acquisition, the potential alteration of vascular volume between different states, and the changing flow pattern induced by contrast agents. This has led to empiric substitution of mean transit time (Tmn) by other time parameters and to representation of vascular volume by maximal contrast intensity (D..). To avoid these problems, intact dogs were studied during almost motionless image acquisition of 20-25 consecutive paced heart beats obtained with synchronous radiographic pulses. In (weight, 26-36 kg) were anesthetized with sodium pentobarbital 25 mg/kg i.v., a left thoracotomy was performed, and epicardial pacing electrodes were sutured on the left atrium. The proximal part of the left circumflex artery (LCx) was gently dissected free, over a distance of 1.0-1.5 cm proximal of the origin of the first large obtuse marginal branch. A ring-mounted 20-MHz pulsed Doppler probe (Crystal Biotech Inc., Holliston, Massachusetts) was placed around the artery and a circular balloon occluder (R.E. Jones, Silver Springs, Maryland) was placed just distal to the Doppler probe. The pericardium and chest were closed, and the instrumentation leads were placed in a subcutaneous pocket until the time of study.At day 11 after instrumentation, each dog was anesthetized by nicomorphine 10 mg/hr i.v. and ethrane. The subcutaneous pocket was opened, and the wires of the Doppler probe were connected to the appropriate recording equipment (545C-4 Directional Pulsed Doppler Flowmeter, Department of Bioengineering, University of Iowa, Iowa City, Iowa). The pacing electrodes were attached to a trigger unit (Department of Bioengineering, University of Nijmegen, The Netherlands) and the occluder tube was connected to a 5-ml syringe. Both femoral arteries were dissected free. An 8F pigtail manometer catheter (Millar microtipped-catheter transducer SPC-780C) was introduced into the left femoral artery and positioned for simultaneous pressure recording in the left ventricle and the ascending aorta. A 5F left Judkins catheter was introduced into the right femoral artery and advanced into the ostium of the left main coronary artery. Electrocardiogram, left ventricular pressure and its first derivative, aortic pressure, and phasic and mean coronary blood flow velocity in the LCx were recorded on an eightchannel recorder (Hewlett-Packard).After intravenous infusion of 5 mg propranolol during 20 minutes to prevent disproportionate increase in heart rate, an initial dose of dipyridamole (0.75 mg/kg) was administered intravenously during 4 minutes to create maximal dilation ...

The total duration of AF is correctly represented by the total duration of AMS and can be considered a reliable measure of total AF duration. AT duration was poorly correlated with AMS duration. The number of mode switches does not reflect the number of episodes of AF/AT. Increased memory capacity allowing the storing of all EGMs triggered by the initiation of AF/AT would be the ideal setting with which to optimize the diagnostic performance of pacemakers.

Objective-To study the possible pathophysiological implications of long continucd dietary sodium restriction in pregnancy. Design-Longitudinal prospcctive randomized study of the effects of a low sodium diet compared with unrestricted sodium intakc in prcgnancy. of Rcproduction T. K. A . B. ESKES Professor P. R. HEIN Senior Lc,ctrirer in Obstetrics promptcd by thc belief that excessive retention of sodium and water is the main cause of prceclampsia and eclampsia in particular (Cramer 1906; Dc Snoo 1Y37).

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