Cardiac arrythmia

Question 1

Causes of arrythmia

Answer 1

1. Conduction block
   - a propogating impulse is blocked that is electrical excitably
2. Escape Rhythms
   - SA node is impaired and does not fire frequently
   - Escape beats triggered by pacemaker cells of ventricles
   - protective mechanism to prevent heart becoming pathologically show

Question 2

Nervous control of heart

Answer 2

1.  Increased
• sympathetic stimulation 
- B1 adrrenergic receptor
2. Decreased
- increased parasympathetic activity of vagus nerve

Question 3

Bradycardia

Answer 3

below 60 beats a minute

Question 4

Causes of bradycardia

Answer 4

1. Lev’s disease - idiopathic cases of cardiac conduction defects, fibrosis and scarring
2. Heart disease - ischaemia as heart muscle is deprived of oxygen and causes scar tissue to form which block electrical conduction
3. Cardiomyopathies - diseases of heart muscle wall
4. Myocarditis - inflammation of heart muscle

Question 5

Extrinsic causes of bradycardia

Answer 5

1. Athletes - have high stroke volume thus slow heart rate

2. Obstructive sleep apnea - heart block as a result of soft tissue around the neck

Question 6

Two major types of Brady cardia

Answer 6

1. Atrioventricular node block

2. Sinus node disease

Question 7

Sinus node disease ( Bradycardia)

Answer 7

a group of abnormal heart rhythms caused by malfunction of sinus node, primary pacemaker of heart

• > Sinus pause - SAN fails to generate impulses
• > Sinoatrial exit block - failure of conduction from nodal region to surrounding tissue

Question 8

Atrioventricular node block

Answer 8

1. First degree heart block -
   -> signal is delayed but still makes it to the ventricles
   PR interval > 200ms - no symptoms
2. Second degree heart block
   i. Mobitz type 1 - Wenckebach
   PR interval gets progressively longer until dropped beat occurs, blocked completely
   ii. Mobitz type 2 -
   - no progressive lengthening of PR interval
   - random, intermittent dropped beats
3. Third degree heart block
   - signal from atria to ventricle completely blocked
   - Only escape beats
   - severe dyspnea, chest pain and risk of death

Question 9

Symptoms of bradycardia

Answer 9

• Asymptomatic in first degree heart block
• Fatigue, muscle weakness
• palpitations
• Hypotensive - low bp
• Oligururia - low vol of urine