The contractile apparatus in heart failure

ABSTRACTS

Twenty-Second Annual Scientific Session American College of Cardiology San Francisco, California, February 14-18,1973

Method

and Criteria of Selection

of Abstracts

for Presentation

A record number of abstracts (825) was received by the College for consideration for presentation at the 22nd Annual Scientific Sessions. These abstracts were zarefully reviewed by the Scientific Program Committee, Committee members being divided equally into 2 similar teams comprising individuals representing adult cardiology, pediatric cardiology, cardiovascular surgery, pathology and basic science. Abstracts were sent at random to Team A or B, and 9 members of either team graded the abstracts objectively and independently from 1 to 10, with 10 being the highest. Individual results were returned by each member to the Bethesda Office of the College. When an abstract came from a reviewer’s institution, an abstention was recorded. The scores on each abstract were then averaged by the College staff. All abstracts receiving a grade of 7.6 and above were accepted for presentation after a brief review by the Committee. Those rated between 6.2 and 7.6 were individually discussed in detail by the entire Committee. It was possible to select a total of 202 abstracts for the final program. John Ross, jr., MD, FACC Scientific Program Chairman I

FUNCTIONAL PROPERTIES OF THE VENTRICULAR MUSCLE AND DISTAL CONDUCTING SYSTEM DURING PREMATURE VENTRICULAR STIMULATION. Abdul S. Agha,* MD, Agustin Castellanos,Jr MD, FACC, Robert J. Myerburg, MD, Cesar A. Castillo, MD, and Benjamin Befeler, MD. University of Miami School of Medicine and the Veterans Administration Hospital,Miami, Florida.

THE CONTRACTILE Gail G. Ahumada,

APPARATUS IN HEART FAILURE MD; Philip D. Henry, MD; William

To explore examined (F) rabbit

FACC,

tension curves of intact

F.

UCSD,

in heart failure

we

tension and simultaneous

fibers from 18 normal (N) and 14 failing

right ventricles

and markedly

isometric

length (L), as well

from the same hearts matched tently

MD,

the basis of depressed contmctility sarcomere

ATPase of glycerinated

In four patients the right ventricular apex (RVA) was driven by Sl and the cycle scanned by 52. Driven impulses consistently produced a predominant negative deflection in lead Vl. Filtered 1 mm apart bipolar catheter electrodes were used to record from the His bundle area, right ventricular outflow tract (RVOT) and posterosuperior wall of the left ventricle (LV). The latter was explored through the great cardiac vein. The findings to be described below occurred early in the cycle, between effective refractory period and full recovery time. In two cases retrograde Hl-H2 intervals were longer than the RVOTl-RVOTZ intervals which, in turn, exceeded the LVlLV2 intervals. When this occurred the premature impulses delivered to the RVA produced a positive deflection in lead Vl. In the other two patients Hl-H2 intervals were longer than RVOTl-RVOTZ intervals, both exceeding the Sl-S2 values. However, the LVl-LV2 intervals were at least 15 msec shorter than later in the cycle for a period ranging between 100 and 160 msec. In conclusion: (a) intraventricular propagation can be subnormal or "supernormal" at different recording sites during the same (early) part of the cycle and (b) the (retrograde) functional refractory period of the distal conducting system is significantly longer than that of the ventricular muscle.

Burton E. Sobel,

Friedman, MD, FACC; La Jolla, California.

as mechanics

for cross-sectional

muscles from failing

depressed [50% average

muscles

of papillary area.

The length-

hearts were consisdecrease

in tension at

Lmax, n = 161. However, failing

in glycerinated fibels from normal and hearts tension was similar (1234 f 57 (S.E.) mg/mm2 [N,

n = 181 and 1157 i 47 [F, n = 141) at optimal sarcomere length with pCa (-log free calcium concentration) = 5.4. Absolute glycerinated

fiber ATPase was lower in fibers from failing

at each tension (34 f 4 (F) vs. 68 i 5 (N) spite azide linearly

or detergent

treatment.

and to the same extent

hearts with increasing

tension.

hearts

nmoles/mg/minute)

However,

de-

ATPase increased

in fibers from normal and failing Glycerinated fiber pCa-tension

curves (obtained at Lmax) were virtually identical in fibers from normal and failing hearts when pCa was varied from 7.0 to 5.4. Thus, depressed contractility

of failing

myocardium

is not due to

intrinsic abnormalities of the contractile apparatus reflected by deficiencies in: 1) capacity for tension generation; 2) calcium sensitivity; or 3) augmentation of ATPase associated with tension.

* Abstracts are listed alphabetically according to first author.

January 1973

The American Journal of CARDIOLOGY

Volume 31

115