Congestive heart failure (CHF) is a clinical
syndrome with multiple causes and involve
the right or left ventricle or both and in CHF,
cardiac output is usually below the normal
range. This ventricular dysfunction may be
systolic, which leads to inadequate force
generation to eject blood normally and
diastolic, which leads to inadequate
relaxation to permit normal filling. Systolic
dysfunction, with decreased cardiac output
and significantly reduced ejection fraction
is typical of acute heart failure, especially
that resulting from myocardial infarction.

CARDIAC GLYCOSIDES

There are the drugs having cardiac inotropic
property. They increase myocardial
contractility and cardiac output in a
hypodynamic heart without increase in
oxygen consumption and overall
myocardial efficiency is increased.

The cardiac glycosides are mainly
obtained from plants e.g. digitalis,
stropanthus and squill species and also
present in certain other plants and animals.
In 1776, William Withering, a Birmingham

physician and botanist identified digitalis

and other ingredients, which was found

useful in the treatment of dropsy. In 1911,

Mackenzie and Cushney studied the effect

of digitalis on heart and its use in congestive

heart failure.

The important cardiac glycosides are

listed in table 4.1.1.

Pharmacological Actions

Effect on Heart

Contractility: Digitalis increases the force of

myocardial contraction without causing

corresponding increase in the oxygen

consumption. This pharmacological action

forms the basis of its use in treatment of

CHF. In a patient of CHF, force of

contraction of the heart at a given fibre

length is decreased, thus the stroke volume

is decreased. As digitalis increases the force

of contraction of the heart and subsequently,

it increases the cardiac output, increase in

circulating velocity, residual volume is

decreased, diastolic volume is decreased

and size of heart is decreased but these

effects are noticed secondary to increase in

(Mode of Action of Drugs)

PharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamicsPharmacodynamics

Chapter

1.4

Chapter

4.1

Cardiotonics

(Cardiac Glycosides)(Cardiac Glycosides)(Cardiac Glycosides)(Cardiac Glycosides)(Cardiac Glycosides)

Cardiotonics