ABSTRACTS

THB INFLUENCE OF pH ON LACTATE METABOLISM AND OXYGEN UP- LEFT VENTRICULAR FUNCTION ASSESSED BY RADIONUCLIDE TAKE IN WINE SKELETAL MUSCLE. Alden H. Harken, M.D. ANGIOGRAPHY AND ECHOCARDIOGRAPHY IN PATIENTS Walter Reed Army Institute of Research, Washington, D.C. WITH PREVIOUS MYOCARDIAL INFARCTION

All cells have the capacity to produce lactic acid under anaerobic conditions. The liver is responsible for most of the lactate clearance from the blood. Other tissues can consume lactate. however. The ouruose of this study

Hartmut Henning, MD; Heinrich Schelbert, MD; Michael Crawford,

MD; John Ross, Jr., MD, FACC; William Ashburn, MD; Joel S.

Karliner, MD, FACC; Robert A. O’Rourke, MD, FACC, University

of California, San Diego, Calif. was to evaluate the rate of lactate production and oxygen utilization by an isolated canine hindlimb at various hydrogen ion concentfations. A membrane lung perfusion system was established such that blood flow and tempera- ture could be fixed at normal levels. Oxygen, nitrogen, and carbon dioxide (C02) gas flows were independently regulated to provide a fixed arterial oxygen content

(CaO2). By changing CO2 flow and periodic addition of bicarbonate, the pH of the arterial blood was varied be- tween 6.9 and 7.6 at ten minute intervals. Lactate pro- duction and oxygen consumption (VO ) were evaluated in ten 25-30 kg dogs. The mean 02 de f. Ivery (Ca02 x flow) was between 16.3 ml Op/min and 20.5 ml 02fmin. Standard error of the mean in each dog, however, was less than 0.4 ml 02/min. Lactate production was linearly related to pH: lactate produced = 22.5 pH - 162.5 (r = 0.75). Vg2 (ml/ min/kg limb) = 100.1 pH - 643 (r = 0.866). Oxygen con- sumption may be inversely related to PC02 : Vg2 = -0.62 PC02 + 124, but the correlation is less good (r = 0.729). Skeletal muscle can produce and consume lactate. The rate of lactate production may be directly related to pH, and may have a homeostatic effect on pH regulation. OXr- gen consumption of skeletal muscle also appears critic- ally pH dependent. The dangers of alkalosis on increased 02 consumption and lactate production during and follow- ing cardiopulmonary bypass surgery are evident. Post- operative alkalosis may rank with the well recognized risks of acidosis, and should be &voided.

TREA?MENT OF SEVERE CORONARY ARTERY DISEASE WITH QUADRUPLE AND QJINKJF'LE SAPHEhWS VEIN GRAFTS: RJWEW OF ONE HUNDRED CONSECUTIVE CASES Bradley Harlan, M. D., George J. Reul, Jr., M.D.,F.A.C.C., Denton A. Cooley, M. D., F.A.C.C., Frank M. Sandiford, M. D., Don C. Wukasch, M. D., E. Ross Kyger, III, M. D., Grady L. Hallman, M. D., F.A.C.C., Texas Heart Institute, Houston, Texas

In order to establish the anatomical criteria, the func- tional results and the safety of complete myocardial revascularization for severe coronary artery disease (CAD), 100 consecutive patients (pts.) wfio received four (96 pts.) or five (4 pts.) saphenous vein grafts (SVG) were analyzed. The age ranged from 37 to 75 years with a mean of 56. Males predominated by a ratio of 12 to 1. As an indication of the severity of multiple vessel disease, 28% were in Functional Class IV and left ventricular function was classified as: 47% good, 44% fair, 8% poor. Of the 404 arteries receiving SVG, 23% were totally oc- cluded, 39% had 90-99% stenosis and 38% had between 50 and 90% stenosis. Fourteen pts. had significant obstruc- tion of the left main coronary artery. All 100 patients had SVG to the left anterior descending (LAD); 96 to the right coronary artery; 94 to the obtuse marginal branch of the circumflex (Cx); 78 to a diagonal branch of the LAD and 27 to the distal Ck. Overall mortality was 4% and correlated with severity of disease. Two pts. had fatal myocardial infarction; one neurologic complication and one had fatal arrhythmia. Development of new or deeper Q waves occurred in 12% and only one of these had low cardiac output. Fifteen per cent had minor atria1 or ventricular arrhythmias. Follow-up from 8 to 26 mos., postoperative arteriograms and anatomic indications for multiple grafting techniques will be discussed.

We have shown previously that the ejection fraction (EF) deter-

mined by hi h frequency analysis of the time-activity curve of in- travenous 9’ Tc corresponds to the EF calculated by biplane cinean- giography and is independent ofassumptions regarding chamber geom-

etry . Therefore, we have compared the radionuclide method to the

EFand mean rate of circumferential fiber shortening (Vcf)derived by

echocardiography. In 13 of 36 patients (pts) with previous myocar-

dial infarction who had a normal heart size and no wall motion ab-

normalities (WMA)(determined by heart-motionvideotracking), EF

by both methods correlated well (r = .83, p <.OOl), and there was

complete separation between pts with normal and reduced EF. By

contrast, in 23 pts with either WMA (1.5 pts) or cardiomegaly (8 pts),

EF by both methods correlated poorly (r = .45). Among these 23 pts,

14 (61%) with a reduced EF by 99mTc (< .52) had a normal EF by

echo. Similarly, 11 of these 23 pts (48%) with a reduced EF by 99mTc

had a normal mean Vcf (>l .05 circumferences/set) by echo. In all

pts with WMA and reduced EF by 99mTc and a normal EF or mean

Vcf by echo, the WMA involved the anterolateral left ventricular

surface and none had WMA involving the posterior left ventricular

surface. Thus, in pts with anterolateral WMAa reduced EF or mean

Vcf may not be detected by ultrasound because the plane of the echo

beam does not traverse these areas of asynergy. We conclude that

echo overestimates EF and mean Vcf in pts with important antero-

lateral WMA or cardiomegaly, and that EF by 99mTc is a more ac-

curate method of assessing left ventricular performance in such pts.

EFFECT OF PROLONGED SPACE FLIGHT ON CARDIAC FUNCTION AND DIMENSIONS Walter L. Henry, M.D.; Stephen E. Epstein, M.D., FACC; James M. Griffith, MSEE; Robert E. Goldstein, M.D.; David R. Redwood, M.D., NHLI, Bethesda, Md.

Future space programs call for long duration spaceflight. However, the effect of prolonged weightlessness on car- diac dimensions and function is largely unknown. In order to assess the effect of prolonged spaceflight on the heart, echocardiographic studies were performed pre- and postflight in the Skylab 4 Astronauts. Preflight measure- ments in the commander (CDR) revealed the left ventricular end-diastolic volume, stroke volume, and mass to be at the upper limit of normal, while those of the scientist pilot (SPT) and pilot (PLT) were increased significantly above the normal range. These findings in the SPT and PLT re- semble those seen in trained distance runners. Wall thickness measurements were normal in all three crew mem- bers preflight. Postflight measurements were unchanged in the CDR immediately following splashdown and through 68 days postflight. In both the SPT and PLT, however, slight decreases were noted in left ventricular end-diastolic volume (15%), stroke volume (14%), and mass (5%) immediate- ly following splashdown. These decreases persisted through 11 days postflight but had returned to near normal by 31 days following splashdown. Wall thickness measure- ments were unchanged. Left ventricular function curves were constructed for the CDR and PLT by plotting stroke volume versus end-diastolic volume during lower body nega- tive pressure. In both astronauts, pre- and postflight data fell on the same straight line demonstrating that no deterioration in cardiac function had occurred. These data indicate that the cardiovascular system adapts well to prolonged weightlessness and suggest that alterations in cardiac dimensions and function are unlikely to limit man's future in space.

January 1975 The American Journal of CARDIOLOGY Volume 35 143