Question

Case study: A 56-year man suffering from shortness of breath, bradycardia, dizziness and fatigue presents to his GP. He is already on medication for hypertension, so she refers him to a cardiologist for further investigations. The doctor orders an echocardiogram and a CT scan. The results of the tests reveal that the man has an abnormal aortic valve that is interfering with the heart function.

1. Define bradycardia and state two causes of this condition [3 marks]
2. Describe the structure and function of the aortic valve and explain the consequences of an incompetent valve. [7 marks].

The patient undergoes surgery to replace the heart valve and is prescribed warfarin. He is released from hospital and while at home he is visited by a nurse who administers the warfarin. During the process, the man collapses and is taken back to hospital. He is diagnosed with a heart block, with atrial fibrillation.

3. Explain why warfarin is prescribed following valve replacement surgery. [1 mark]
4. Explain what is meant by a heart block [3 marks].
5. Explain what is meant by atrial fibrillation. [2 marks]
6. Outlines 2 methods that can be used to treat atrial fibrillation [2 marks]
7. Briefly outline how a pacemaker works. [2 marks]

Answer 1

Answers :

Define Bradycardia :

Bradycardia is a type of heart rhythm disorder, with a resting heart rate of 60 beats per minute or less.

Causes :

• Herat tissue damage related to aging
• infection of heart tissue ( myocarditis )
• hypothyroidism

Structure and functions of the aortic valve :

The aortic valve situated in the human heart between the left ventricle and the aorta. The aortic valve has theree cusps . The aortic valve is the last structure in the heart. The thee cusps , when the valve is closed , contain a sinus called aortic sinus . In two of these cusps , the origin of the coronary arteries found. The width of the sinus in cross-section is wider than the left ventricular outflow tract as well as wider than ascending aorta. The junction of the sinus with the aorta is called the sinotubular junction. The aortic valve is located posterior to the pulmonary valve and the commissure where the anterior two cusps join together points toward the pulmonary valve . It is these two sinuses that contain the origin of the coronary arteries.The congenital diseases transposition of the great arteries, these two valves are reversed and the origin of the coronaries still follows the rule that the origin are in the sinuses facing the pulmonary valve.

Functions and consequences :

• When the left ventricle contracts pressure rises in the left ventricle. when the pressure in the left ventricle rises above the pressure in the aorta , the aortic valve opens., allowing the blood to exist the left ventricle into the aorta. When ventricular systole ends, pressure in the left ventricle rapidly drops. When the pressure in the left ventricle decreases the momentem of the vortex at the outlet of the valve forces the aortic valve to close. The closure of the aortic valve contributes the A2 component of the second herat sound ( S2).
• Insufficiency : Closure of the aortic valve permits maintaing high pressuures in the systemic circulation while reducing pressure in the left ventricle to allow blood circulation from the lungs to fill the left ventricle.
• Abrupt loss of function of the aortic valve result in acute aortic insufficiancy and loss in the normal diastolic blood pressure resulting in a wide pulse pressure and bounding pulses.
• The endocardium perfuses during diastole and so acute aortic insufficiancy can reduce perfusion of the heart , consequently , heart failure and pulmonary edema can develop.
• Slowly worsening aortic insufficiency result in a chronic insufficiency which permits the heart to compensate. This compensation is throgh hypertrophy of the left ventricle and return to normal filling pressure.
• Stenosis : Inadequate opening of the aortic valve , often through calcification , results in higher flow velocities through the valve and larger pressure gradient.

Why warfarin is prescribed ?

Warfarin is an anticoagulent. So it is reduce the formation of blood clotes, mainly in veins and arteries to reduce the risk of strock , heart attck etc. So in this scenerio may the patient get the chance to clotting of blood due to valve replacement surgery, to prevent blood clot it has prescribed.

What is meant by herat block ?

Heart block is a disorder in the heart's rhythm due to a fault in the natuaral pacemaker. Herat beats too slowly , which results in the electrical signals being partially or totally blocked between the upper chambers and lower chambers . It is also called atrioventricular ( AV )block.

Atrial fibrillation :

It is an abnormal heart rhythm charecterised by the rapid and irregular beating of the atrial chambers of the heart that can lead to blood clots, stroke , heart failure and other heart-related complications.

Two method can treat atrial fibrillation :

The treatment goals for atrial fibrillation are to : reset the heart rhythm or control the heart rate and prevent blood clots which may decrease the risk of atrial fibrillation.  

• Prescribed medication to control heart beats , such as : digoxin , beta blockers and calcium channel blockers .
• Electrical cardio version : in this breif procedure , an electrical schock is delivered to heart through paddles or patches placed on chest . The shock stops heart's electrical activity for a short moment, The goal is to reset heart's normal rhythm.

How a pacemaker work ?

A pacemaker helps monitor and control heart beat . The electrodes detect heart 's electrical activity and send data though the wires to the computer in the generator. If heart rhythm is abnormal , the computer will direct the generator to send electrical pulses to heart.