Webster's New World Medical Dictionary

cardiac defibrillator, implantable
A device
that is designed to be put in the body to recognize
certain types of abnormal heart rhythms (arrhyth-
mias) and correct them by delivering precisely cal-
ibrated and timed electrical shocks to restore a
normal heartbeat. Defibrillators continuously mon-
itor the heart rhythm in order to detect overly rapid
life-threatening arrhythmias, such as ventricular
tachycardia (rapid regular beating of the ventricles,
the bottom chambers of the heart) or ventricular
fibrillation (rapid irregular beating of the ventri-
cles). Today’s implantable defibrillators can be
implanted with less invasive surgical techniques
than in the past.
cardiac index
A cardiodynamic measure based
on the cardiac output, which is the amount of blood
the left ventricle ejects into the systemic circulation
in one minute, measured in liters per minute
(l/min). Cardiac output is indexed to a patient’s
body size by dividing by the body surface area to
yield the cardiac index.
cardiac muscle
A type of muscle tissue that is
found only in the heart and is distinguishable from
the two other forms of muscle, smooth muscle (that
moves internal organs, such as the bowels, and ves-
sels, such as the artery walls) and skeletal muscle
(that powers joints). Cardiac muscle is responsible
for pumping blood throughout the body.
cardiac output
The amount of blood the heart
pumps through the circulatory system in a minute.
The amount of blood put out by the left ventricle of
the heart in one contraction is called the stroke vol-
ume. The stroke volume and the heart rate deter-
mine the cardiac output. A normal adult has a
cardiac output of 4.7 liters (5 quarts) of blood per
minute.
cardiac septum
The dividing wall between the
right and left sides of the heart. That portion of the
septum that separates the two upper chambers (the
right and left atria) of the heart is termed the atrial
(or interatrial) septum; the portion that lies
between the two lower chambers (the right and left
ventricles) of the heart is called the ventricular (or
interventricular) septum.