Abstracts 1.53

styrcne microspheres or with autologous blood clots

was induced in amounts sufficient to produce pul-

monary hypertension but not sufficient to produce

significant changes in mean femoral artery pressure

or cardiac output. In 10 dogs, LCBF increased from

5 to 122 ml./min., representing a range of increase of

9 to 138%, and an average increase of 30 ml./min.

or 45$&. In 1 dog LCBF remained unchanged, and

arterial partial pressure of oxygen (PO,) remained

normal after PE. Arterial pOz fell below 65 mm.

Hg in 8 dogs after PE. Depression of the S-T seg-

ments or changes of the T waves were noted in the

electrocardiograms of 7 dogs.

The administration of oxygen after PE was associ-

ated with a decrease of LCBF toward control levels

and elimination of the S-T and T wave changes in 3

of 4 dogs to which it was given. No support was found

for the concept of pulmonocoronary reflex spasm. The

S-T and T wave changes that occur after PE and in

the absence of shock appear to be due to hypoxemia.

Slowing of the Left Atrial “Y Descent”: Evidence of

Impaired Rate of Left Ventricular Filling in Idio-

pathic Hypertrophic Subaortic Stenosis and Aortic

Stenosis, SCOTT STEWART, M.D., DEAN T. MASON,

M.D.. F.A.c.c., JOHN Ross, JR., M.D. and EUGENE

BRAUNWALD, M.D., F.A.c.c., Bethesda, Md.

To determine whether there is any interference

with left atria1 emptying and left ventricular filling

in idiopathic hypertrophic subaottic stenosis (IHSS)

and aortic stenosis (AS), the fall in pressure (y de-

scent) of the left atria1 V wave following the opening

of the mitral valve was analyzed in 27 patients with

IHSS and in 10 patients with AS. The results were

compared to those in 13 normal subjects and 23

patients with mitral stenosis (MS).

The y descent in 0.1 second averaged 7.5 mm. Hg

in normal subjects and was significantly lower in

IHSS (3.4 mm. Hg) and in AS (5.0 mm. Hg).

The peak rate of decline of the y descent (negative

dp/dt) averaged 128 mm. Hg/sec. in normal subjects

and was significantly lower in IHSS (67 mm. Hg/

sec.). in AS (88 mm. Hg/sec.) and in MS (91 mm.

Hg/sec.). Thus, a slow y descent of the left atria1

pressure pulse occurs in IHSS and AS and appears to result from reduced left ventricular compliance

and possibly from interference with complete open-

ing of the mitral valve by ventricmar hypertrophy.

It is concluded that there is an impairment of the

left ventricular filling rate in idiopathic hypertrophic

subaortic stenosis and aortic stenosis and that ob-

struction to ventricular inflow, as well as to outflow, contributes to the hemodynamic changes in these

conditions.

VOLUME 19, JANUARY 1967

Transvenous Catheter-Electrode Pacing of the

Heart, ROBERT G. TANCREDI, M.D., Bcv D. MCCAL-

LISTER, M.D. and HAROLD T. MANRIN, .M.LI., Rochester,

Minn.

Experience with 112 separate periods of transvenous

intracardiac pacing in 93 patients is reviewed. Pacing

was accomplished by a bipoiar catheter electrode

placed in the right ventricle. Indications for the use

of catheter-electrode pacing included (1) complete

heart block with and without Adams-Stokes attacks

(53 patients), (2) other arrhythmias with and with-

out cardiogenic syncope (14 patients), (3) malfunc-

tion of previously implanted permanent pacemaker

units (27 patients), and (4) surgical procedures for

patients having disturbances of cardiac rhythm (6

patients).

The combined use of catheter pacing and cardio-

depressant drug therapy in the treatment of paroxys-

mal tachyarrhythmias is emphasized and discussed.

Major complications associated with the use of the

catheter electrode were perforation of the heart (4

cases), bacteremia (1 case), acute myocardial infarc-

tion (1 case), phlebitis of the cephalic vein (1 case).

ventricular tachyarrhythmia (2 cases), and accidental

cessation of pacing (1 case). Two patients died as a

result of major complications. Minor problems were

primarily concerned with catheter positional

difficulties (29 cases) or equipment failure (9 cases)

and were usually of no serious consequence. Technics

are outlined for localization and correction of mal-

functions in catheter-pacing equipment.

A New Simple and Sensitive Method for the Quan-

titative Assay of Angiotensin, GC’RDARSHAN S.

THIND, M.B., LYSLE H. PETERSON, M.D. and HARRY F.

ZINSSER, JR., M.D., F.A.c.c., Philadelphia. Pa.

To investigate the role of renal-adrenal system feed-

back loop in the control and regulation of the cardio-

vascular system, it is essential to have a simple, sensi-

tive, quantitative and reproducible method to deter-

mine the output of the feedback loop. None of the

currently available in viva and in v&o angiotensin

bioassay methods is ideal and fulfills the criteria.

Unlike other smooth muscle preparations, rabbit

thoracic aorta which does not exhibit any spon-

taneous activity was found to be an ideal preparation

to bioassay angiotensin. Also, it was believed that

recording the changes in tension developed (isometric

technic) rather than the changes in length (isotonic

technic) of the contractile tissue may prove to be a

much superior parsmeter.

The usual sensitivity of detecting angiotensin

II by the isometric bioassay technic varies from 0.0001

to 0.0005 pg./ml. in the bath. Under optimal condi-