Biology Today - May 2018

THERAPEUTIC DEVICES

Prosthetic cardiac pacemaker/Artificial pacemaker. When the natural pacemaker
SA node does not work properly, in such patients normal heart beat can be restored and
maintained with an artificial pacemaker. The artificial pacemaker was introduced by
Chardack in 1960.

Temporary pace maker is used in emergency such as during bradycardia.

Permanent pacemaker is used in atrioventricular (AV) block, SA node dysfunction,
etc. The artificial pacemaker consists of a pulse generator containing cell (solid state
lithium cell), the lead in the form of a wire and an electrode. During implantation the
pulse-generator is placed in a sub-cutaneous pocket. The lead is inserted into a particular vein which is finally carried to the right
ventricle to make contact with the ventricular myocardium.

Defibrillator : Artificial fibrillation may occur in myocardial infarction and in rheumatic heart disease. Ventricular fibrillation
is immediately life threating unless it can be stopped by defibrillation. The arrest of cardiac muscle (atrial or ventricualr) with
restoration of the normal rhythm is called defibrillation. A machine which is used to do defibrillation is called defibrillator.

Angioplasty (Balloon catheterisation) : In this technique, atherosclerotic plaques from the coronary arteries are removed
through ballooning. During this procedure, a very small balloon-tipped catheter is inserted into the coronary artery under X-ray
observation. Then the balloon is inflated with air to squash the plaques against the blood vessel wall, thereby clearing the lumen
of the vessel for blood. It increases the blood flow through the vessel.

Vascular grafts (Artificial arteries) : Arteries supply blood to various parts of the body. So, any blockade in them would deprive
the organ or the tissue to get blood or in other words the oxygen and various nutrients. This requires reconstructive operation
which is done by the use of artificial arteries or vascular grafts. These artificial arteries are made from porous plastic fibres of
dacron or teflon.

Stent : It is small mesh tube that is used when plaque blocks blood vessels or treat narrow or weak arteries. It is made of either
metal or plastic. Stent grafts are larger stents used for larger arteries. They may be made
of a specialised fabric.

Coronary Artery Bypass Grafting (CABG) : It is normally done when the coronary
artery is totally blocked by clot/clots. In this surgery, a blood vessel is taken from another
part of the body and is used to bypass the blocked region of the coronary artery. The
saphenous vein (from the leg) and the internal mammary artery (from the chest)
are mostly used for this procedure. After this surgery the blood supply to the heart
increases.

Pacemaker

Right

ventricle

Right

artrium

Pacemaker

leads

Stent Catheter

Guide

wire

1. Which of the following waves is not represented in a typical
   ECG?
   (a) Depolarisation of atria
   (b) Depolarisation of ventricles
   (c) Repolarisation of atria
   (d) Repolarisation of ventricles


2. The frequency of heartbeat in our body is maintained by
   (a) AV Node (b) SA Node
   (c) bundle of His (d) chordae tendineae.


3. During ventricular systole,
   (a) oxygenated blood is pumped into the pulmonary artery
   and deoxygenated blood is pumped into the pulmonary
   vein

(b) oxygenated blood is pumped into the aorta and

deoxygenated blood is pumped into the pulmonary

vein

(c) oxygenated blood is pumped into the pulmonary vein

and deoxygenated blood is pumped into the pulmonary

artery

(d) oxygenated blood is pumped into the aorta and

deoxygenated blood is pumped into the pulmonary

artery.

4. Which of the following statement(s) regarding the cardiac
   system is/are correct?
   (i) Human heart is an ectodermal derivative.
   (ii) Mitral valve guards the opening between the right atrium
   and left ventricle.