Lecture 15 (Heart blocks and heart failure)

Question 1

What is a partial and complete block caused by? (2)

Answer 1

-Partial block caused by inappropriate depolarisation
-Complete block caused by abnormal anatomy

Question 2

What happens in a 1st degree block? (2) (partial)

Answer 2

-Slowed conduction (1st degree AV block), Longer PR interval

Question 3

What happens in a 2nd degree block? (partial)
What are the two types and what do they do? (4)

Answer 3

-Intermittent block (only some signal conducted)

2 Types
Mobitz type I
-PR interval gets larger unit AV node fails
(lack of ventricular depolarisation)

Mobitz type II
-PR interval constant, every nth ventricular depolarisation is missing
(2:1 AV depolarisation to V depolarisation)

Question 4

What is a rate dependant block (partial block)?
(very uncommon)

Answer 4

Disease in the large branches
-Bundle branch block (delay/blockage to electrical signals that make heart beat) associated with increase in heart rate

Question 5

What is a unidirectional partial block?
What effect does this have to synchronisation?

Answer 5

-Conduction of electrical signal only possible in 1 direction

-Two branches out of sync as one is slowed by unidirectional block and other is not

Question 6

What is pacemaker activity set by?
What are the next two pacemakers in line if there is a problem in the first? (2)

Answer 6

The fastest pacemaker - SA node

AV node, Hispokinje system

Question 7

What happens in a 3rd degree block? (complete block)

Answer 7

-When the electrical impulses that tell your heart when to beat don’t pass between the top (atria) and bottom chambers (ventricles) of your heart

Question 8

How might abnormal anatomy cause a complete block? (e.g Wolff-parkinson-white syndrome)?

Answer 8

-Additional accessory pathway A to V – bundle of Kent.
-AV delay lost.
-V depolarization spread out
-Shorter interval P to QRS (delta wave).
-Re-entry can occur - atrial tachycardia.

Question 9

What is heart failure?

Answer 9

A condition where the heart struggles to maintain an appropriate Cardiac Output (CO)

Question 10

What are the main causes of heart failure? (3)

Answer 10

-Ischaemic HD
-Hypertension
-Diabetes

Question 11

What are the symptoms of Heart Failure? (6)

Answer 11

-Dyspnea (shortness breath)
-Cough
-Lower extremity oedema (build up of fluid)
-Fluid abdomen – poor venous return
-Fatigue
-Palpitations (due to compensatory  HR)

Question 12

How is Cardiac Output (CO) calculated?

Answer 12

Cardiac Output = Stroke Volume x Heart Rate
CO = SV x HR

Question 13

How is Mean Arteriole Pressure (MAP) calculated?

Answer 13

Mean Arteriole Pressure = Total Peripheral Resistance x Cardiac Output
MAP = TPR x CO

Question 14

What happens to Mean Arteriole Pressure (MAP) as Cardiac Output (CO) goes down?

Answer 14

Also goes down