Lessening of intimal thickening in arteriovenous grafts

ABSTRACTS

SIGNIFICANCE OF "EXERTIONAL HYPOTENSION" IN MEN WITH ISCHEMIC HEART DISEASE. John B. Irving, M.B., Robert A. Bruce, M.D., F.A.C.C., Nina Chinn and Timothy De Rouen, Ph.D., University of Washington, Seattle, Washington.

LESSENING OF INTIMAL THICKENING IN ARTERIOVENOUS GRAFTS Jeptha R. Hostetler, Ph.D; Panayotis E. Karayannacos, MD; Ronald A. Williams, Ph.D; M. Gene Bond, Ph.D; James W. Kllman, MD; John S. Vasko, MD; The Ohio State University, Columbus, Ohio 43210.

Changes in systolic blood pressure during graded levels of treadmill exercise in 6517 men enrolled in the Seattle Heart Watch ranged from -80 to +180 with a mean of 50 t 26 (SD) mm Hg. Of 3 ischemic heart disease (IHD) patients who developed postexertional ventricular fibrillation and were resuscitated, all showed a limited rise, or fall in pressure with exercise. Of 1670 men with IHD and followed for an average of 2 years, 273 (in parenthesis) had coronary by-pass surgery. Pressure responses to testing were subdivided by quartiles of distribution for all men as follows: 2nd 1st Quartiles 3rd 4th &BP, mm Hg -80 to 19 20 to 34 34 to 55 55 to 180 Subsequent MI 15(5) 9(3) 9(l) IO(3) Cardiac Deaths Sudden 6(O) O(0) 19(O) 5(O) Non-sudden 21(O) 19(O) II(O) 2(O) Subtotals 376(72) 387(69) 516(77) 391(55) Sudden cardiac death occurred in 4.9% (0%) of 1st quartile patients and in 0.97% (0%) of 3rd quartile patients; mortality risk ratio for unoperated IHD patients was 5.1. Horizontal or downsloping ST depression of 1 mm or more was observed 1.9% and 1.2% of IHD patients, with risk ratio of 1.5, in the corresponding quartiles. In conclusion, a limited rise, or a fall in systolic pressure responses of IHD patients during maximal exercise may be a precurser to ventricular fibrillation with testing, and a more useful predictor of subsequent sudden cardiac deaths than ischemic ST depression; subsequent coronary by-pass surgery may protect against this risk.

The water-hammer effect of pulsatlle flow and the deprivation of the vasa vasorum are factors responsible for intlmal proliferation in arterialized vein (A-V) grafts. Histological differences in lntimal thickening between normal A-V grafts and grafts firmly supported with artificial prostheses, which permitted or impeded the development of new vasa vasorum, were studied in dogs. Twentyfour A-V grafts were placed in twelve dogs by replacing the cervical carotid arteries with six cm. segments of autologous jugular vein. Eight grafts were wrapped with nondistensible prostheses, reducing the vein diameter by 10%. Only one-half of the supporting grafts allowed the penetration of new vasa vasorum. Six months post-surgery grafts were removed and specimens prepared for light and electron microscopy. Pronounced lntimal thickening in the untreated grafts was evidenced by increased amOunts of collagen, occurrence of occasional fibroblasts, and a thickened basement membrane. Vasa vasorum were observed in both tunica adventltia and media. Grafts supported by nonporous prostheses had extreme lntimal proliferation, equal to the nontreated ones. The histology was very comparable to the previous group, but vasa vasorum were not observed. By contrast, grafts wrapped in porous prostheses had very little lntlmal proliferation. Vasa vasorum were clearly evident in the tunica media. This study strongly suggests that either the freely pulsating vein graft or the absence of vasa vasorum results in severe intimal thickening. Firm support of the vein wall with free access in the development of new vasa vasorum drastically reduces intlmel proliferation.

CROSS-SECTIONAL ECHOCARDIOGRAPHIC ASSESSMENT OF SEVERITY OF AORTIC STENOSIS IN CHILDREN Roger A. Huwitz, M.D., Arthur E. Weyman, M.D., Harvey Feigenbaum, M.D., F.A.C.C., Donald A. Girod, M.D., James C. Dillon, M.D., F.A.C.C., Janle Stewart, Department of Medicine and Pediatrics, Indiana University, Indianapolis, Indiana In a recent report we described the relationship of maximum aortlc cusp separation (MACS) determined during long axis cross-sectional scanning of the aortic valve to the severity of aortlc stenosis in adults. To utilize this measurement in children correction for body size is necessary. Because aortlc size increases relative to body surface ares as patient size decreases, routine correction of aortlc valve orifice diameter for body surface area is misleading. We therefore related (MACS) as an expression of aortlc orifice size to the diameter of the aortlc root (AO) at the valvular level. Thus the estimated aortlc valve orifice diameter is expressed as a percentage of the aortlc diameter. This value was determined in 25 children, ages 1.5 to 16 (mean 7.9 yrs.), with valvular aortlc stenosis and 22 normal subjects. The results are listed in Table I. Significance TABLE I No. MACS/AO Range 32% 21-40%> Sev. h Mod 12 P = c.001 54% 42-63% Mild 13 P = d.001 63-92%' 22 73% Normal These data suggest that the ratio MACS to A0 should be of value in estimating severity of aortlc stenosis in children.

INCIDENCE

OF

PROGRAM

Frank

Jackson,

W.

Exercise

therapy

for

many

coronary

in

exercise is

This

study

in

is

ET

in

2,627

ET

in

this

usually

located

CCU

nurses

supervise

metry cle of

monitoring ergometer

ET. the

(34%)

(70%)

had

(3%)

ture oped

developed

had

premature beats

consecutive

arrest

or

patients of

CCU

nurse

maximum

method

of

supervisors

degree

of

safety.

exercise

58

19

No

ET

and

in

ET.

is ET

telemetry

473 had (5%)

(3%)

cases

developed in

1,972

rate).

(9%) 34

the

The

premadevel-

had

of

relatively with

of 75%

sessions of

resting

Only

after

providing

modes 60% to

675

and

beats).

imnediately

arrhythmias

this

65

resting).

infarction

or

progress

over

tachycardia.

myocardial during

the at

arrhythmias.

beats, over

ventricular

ventricular

Volume 37

nodal

supraventricular

03

and of

Telebicy-

are

arrhythmias.

(>6/min

06/min

in design.

Treadmill, begin

significant

VPC’s

gym

training

average

for

over

Specially

ET.

rate

di-

Centers

sessions.

patients

heart

the

standardized

usual

exercise

for

An

is

all

and

55

hospitals.

the

ET.

infarction in

the

extremity

assessed

increased

atria1

in

rates

3 months. was

Centers,

program

during

upper maximal

first

patient

patients

used

heart

predictive

per

21

and

Target

their in

is

of

arrhythmias

myocardial

from

are

Furthermore,

various

patients

different

arrhythmias

safety

Rehab

and

trained

a

The American Journal of CARDIOLOGY

and

of

Cardiac

Centers

ed

January 1976

to

the

incidence

28

adjunct

of

unknown. for

arrest

period.

Centers

However,

144

in

therapeutic incidence

currently

the

cardiac

related

It-year

all

desirable The

is

patients of

a

Pennsylvania

physicians

assessed

1,972

a

is

patients. by

REHABILITATION

Harrisburg,

(ET)

concern

incidence rectly

M.D.,

programs

there

IN A CAROIAC

ARRHYTHMIA

EXERCISE

VT

cardiac 2,627

incidence high.

specially

monitoring

trainprovides