Complex hemodynamic effects of paired pacing in the dog compared to those of single pacing at the same driving rate

140

Abstracts

blocking

drugs

negative

inotropic

NCE).

The

that

drugs

action

actions

have

blocked

which The

has

been

were done

By using ously The

isolated,

beating NIE

and NCE

dependent

of

Optical

isomers

and

achieved

(3)

fl-adrenergic

evident

even

or in which blocked

in hearts its release

while

from

some

chronotropic

effect

adrenergic

receptors

sympathetic

Cardiotoxicity specific chemical

at the

results

from

HIRSCH,

PH.D.

Chicago,

Ill. effect

single

pacing

ferent

when

atrium

(RA)

(RV).

PS,

cardiac ventricles,

of the

to

and

when

postextrasystolic hemodynamic pumping in A-V

transmission ventricular

to

the

(1) work

blood

of

Apparently of the responses

to

is difright

to the right ventricle a fall of

pressure,

of both atria.

evidence

rate

and

potentiation

ability.

compared

caused

of the pair in RA stimulation of paired

(PS) driving

SS,

stimulation

J.

and

Applied

in

both (2)

to the

to SS, is the opposite is used. occurs

In and

enhanced

atria1

lengthens so that

to

ventricular

demonstrated second

the RV, leads

delay impulse

minute

and

is

of total the

release

added

which

the

causes.

contribution

and

the in

obscure with

hemodynamic

effect,

due to the loss of presystolic

conduction

presence

the

or counteract

sinus rhythm

of

former. PS

when

the PS driving

this

the sinus

when

two

potentiation

sinus rate.

apt to occur

aberrant

These

rate is that of the pre-existing more

added

reduction

energy

has a detrimental

may

of the

of the

We found rate

in the

in

Aortic

dog was rapid. Late

Diastolic

Mitral

Regurgitation:

Its

Regurgitation

Relation

to the

Austin

Flint

SOMCHART LOCHAYA, M.D., MASAO IGA-

Murmur,

RASHI, M.D. and AARON B. SHAFFER, M.D., Chicago, Ill. The

Austin

Flint

mumur

has long been attributed diastole

of aortic

to vibrations

by impingement

regurgitation

produced

during

of both the aortic

regurgi-

tant jet and forward

mitral

valve flow on the anterior

leaflet

valve.

Left

of the mitral

exceeding

left

diastole

atria1

(reversed

recently aortic

been

pressure

mitral

premature mitral

valve

described

regurgitation.

latter

of the mitral

valve

flow

apical

late

during

this

pressure

latter

gradient)

in certain

This

closure

ventricular in the

part has

cases

valve,

of

more

of severe

finding

indicates

and forward

period

is thus

most

unlikely. variable aortic

length

diastolic

regurgitation

studies.

In

rumbling

was present who

underwent

all 3, a reversed

ventricular

pressure

gradient

the apical

murmur

coincided.

not adequate

to account

murmur

in

diastolic

mitral

aortic

this

normally

valve

wedge-left

was noted,

with which

Classic

concepts

A mild

was

but

are

of the Flint definite

in addition demonstrated

late

to severe cineangio-

in each of these patients.

It is concluded which

hemodynamic

for the genesis

setting.

of

with severe

pulmonary

regurgitation,

regurgitation,

graphically

murmur

in 3 patients

that the absence act

to appose

cusps at the onset of systole

regurgitation

as

the

Late

diastolic

basis

of the Austin

mitral

valve

valve Flint

of certain

perfectly

mitral

may permit

closes

some

prematurely.

regurgitation murmur

factors

the

may be the

in cases

such

as

these. Serial tricular

Hemodynamic Septal

Study

Defect,

in Infants

JOSHUA

with

LYNFIELD,

F.A.C.C. and JAMES S. TANG, M.D., F.A.c.c.,

the interval the second

per

to SS in RA,

ventricular

An Pacing

M.D., L.

output

in systemic

RA

the

M.D., F.A.c.c.,

is applied

the effect of PS, compared

of that

on

of Single Pacing

KATZ,

pacing

stimulus

stroke

to a nonspecific

of Paired

at the same

compared

to be action.

depends

S. LLUCH,

than when applied

output,

cardio-

appears

of any given drug.

N.

paired

(SS)

p-

where

blocking

to Those

a rise in mean pressure RV,

in conditions

Effects

L.

and of

the significant

Rate,

and

is

has been

blockade

which

constitution

Driving

drugs

inotropic

to be related action

Compared

Same

The

negative

Hemodynamic

in the Dog

NIE

agents.

of the

appears

on

endings

p-adrenergic

“quinidine-like”

Complex

nerve

is high)

from

effects (4) The

of this class of compounds

dissociated

be

of norepinephrine,

(especially

activity

toxic effects

can

of p-blocking

depleted

by pharmacologic

Thus,

differing

blockade

period.

(2)

the same

of “quinidine-like”

concentrations

was in-

while

SS in RV

in patients

(1)

potency.

drug,

and the refractory

of appropriate

drugs

blocking

given

that:

time

potentiation effects

i.e.,

use and

impulse

factors

or spontane-

still show essentially

independent

excitability

or

of any

NCE.

driven

recovery

compared

to cause

detrimental dominate,

oxygen

atria1 of

cardiotoxicity.

of 20 P-blocking

potency,

Therefore,

it was found

p-adrenergic

in p-blocking NIE

atria,

two

the

impulses

paired

the contributions

electrically

paired

NIE

of these

situated

Hence,

cardiac

a “quinidine-

however.

less favorably first.

diastolic

function.

to the observed

in producing

rabbit

to the fact

importance

assessed,

a

and

P-sympathetic

to have

to determine

each of these properties

(NIE

myocardial

contributes relative

not

the

moderating

both

effect

attributed

they are thought

NCE.

studies

of producing

are usually

normally

In addition, and

capable

and chronotropic

effects

these

influences like”

are

VenM.D.,

Brookyln,

N. Y. THE AMERICANJOURNAL OF CARDIOLOGY