PBL 1 - Heart Block Flashcards
In electrocardiography, what is the PR interval, and what is its normal range?
The PR interval is the period in milliseconds from the beginning of the P wave (1/2 mark) until the beginning of the QRS complex (1/2 mark) it is normally between 120 and 200ms in duration (1 mark)
Explain carefully the difference between first and second degree heart block (2 marks)
In first degree AV block the conduction from AV node to ventricles is slower than normal (1/2 mark) but occurs with a normal regularity (1/2 mark).
In second degree AV block the conduction from AV node to ventricles is irregular so that PR interval is irregular ( 1 mark)
List four common causes of heart block (2 marks)
Plasma electrolyte imbalance
2. Myocardial damage following myocardial infarction;
3. Coronary artery disease
4. Myocarditis or other forms of cardiomyopathy
5. Heart enlargement related to heart failure
(any four ½ mark each)
An implanted pacemaker is not normally indicated for someone with second degree heart block. However, some patients do require a pacemaker. List two signs that indicate that a pacemaker is needed (2 marks)
Block associated with persistent bradycardia (1 mark), heart failure (1 mark), asystole greater than or equal to 3 seconds (1 mark) or associated with neuromuscular diseases (1mark) (any two marks)
Explain why a diet including leafy green vegetables helps reduce blood pressure (2 marks)
Leafy green vegetables contain nitrate (1/2 mark) which is converted in stomach to nitric oxide (1/2 mark). This nitric oxide then enters the bloodstream where it relaxes vascular smooth muscle (1 mark)
Describe the electrical conductivity in the heart (3)
Electrical impulse (SA node- r atrium) –> atrium contracts –> pushes blood into ventricles –> AV node (delay to allow atrium to finish contracting) –> bundle of His –> Purkinje fibres –> apex (papillary muscles)
What is the effect of Beta blockers? Name 2 beta blockers. (3)
Propanolol Bisoprolol Atenolol Bind to b-adrenoreceptors Block the binding of norepinephrine and epinephrine inhibits sympathetic effects Decreases contractility and heart rate
Why was Jennifer taken of Beta blockers? (2)
Related to heart block
What is Jennifer’s diagnosis (1)
Second degree heart block
Mobitz type 1 (wenckenback)
What is the difference between SA node block and AV node block? (1)
SA block - AV takes over from SA, not a cause for concern
AV block - Delay of atrial impulse conduction in AV node/from AV –> ventricles
3 signs and symptoms of second degree AV block? (3)
May be no symptoms Palpitations (means regularly irregular) o Bradycardia o Dizziness/syncope o Chest pain.
Cause of Mobitz Type II
More severe
Structural damage in the conduction system (infarction, fibrosis, necrosis)
Usually fitted with pacemaker
What is third degree heart block
Complete heart block AV --> ventricles conduction fail completely Severe bradycardia PR is irregulat can cause ventricular arrhythmia
How do you manage heart block? (3)
No therapy unless symptomatic Discontinue BB - give ACE inhibitors Moderate exercise Healthy lifestyle Green veg Severe - pacemaker
How can exercise improve BP
NO production –> vasodilation –> reduces total peripheral resistance –> reduces BP
