Electrocardiography

Question 1

What are the different leads in ECG

Answer 1

Limb leads - 2 types: BIPOLAR LIMB LEADS I, II, III. AUGMENTED LIMB LEADS aVR, aVL, aVF

Chest leads (V1 to V6)

Question 2

Where is each chest lead on the body

Answer 2

V1 -4th ICS (right of sternum)
V2 - 4th ICS (left of sternum
V3 - in between V2 & V4
V5 - 5th ICS on mid-clavicular line
V5 - Anterior axillary line in line with V4
V6 - Mid-axillary line in line with V4 & V5

Question 3

What is blood pressure

Answer 3

Blood that exerts against the inner walls of blood vessels

Question 4

How to take direct arterial blood pressure measurement and its cons

Answer 4

Insert a needle into the artery - connect through a nanometer. However its not very compatible and convenient. Can be uncomfortable for the patient

Question 5

How to calculate Pulse pressure

Answer 5

Systolic blood pressure - diastolic blood pressure (SBP- DBP)

Question 6

Name the 5 phases of the Korotkoff sounds

Answer 6

Phase I - Tapping (110mmHG)
Phase II - Swishing sound. softer and longer (100mmHg)
Phase III - Crisp and loud (90mmHg)
Phase IV - muffled and softer (80mmHg)

Question 7

Describe the likely effects of changes in CO, TPR and blood volume on MAP

Answer 7

Increased chronotropy
Dilation of blood vessels - MAP decreases
Reduced Inotropy (force of contraction) - MAP reduces
Increased fluid retention - SV increases meaning MAP increases
Polycythaemia
Dehydration

Question 7

What is Mean arterial pressure and how do you calculate MAP

Answer 7

Average arterial pressure throughout cardiac cycle

MAP = cardiac output X systemic vascular resistance (CO X TPR or HR SV X TPR

Question 8

What are the factors affecting stroke volume

Answer 8

Preload - Force on ventricular muscle before contraction

Afterload - Force on muscle during contraction

Contractility - strength of contraction at any preload

Question 9

Describe the baroreceptor reflex for control of MAP

Answer 9

Body maintains MAP by baroreceptor reflex (for almost immediate regulation). Baroreceptors are mechanosensors activated by pressure-induced vessel wall stretch. Keeps BP in normal range in response to an abrupt change in position.

Question 10

Describe how hormonal mechanisms, such as the renin-angiotensin-aldosterone pathway, regulate blood pressure over the longer term

Answer 10

• When there is drop in BP or FV, renin is released from kidney.
• Renin then acts on Angiotensinogen (plasma protein) to form Angiotensin I.
• Angiotensin-converting enzyme releases from lungs and acts on Angiotensin I to from Angiotensin II. II also acts on blood vessels stimulating vasoconstriction
• Angiotensin II acts on adrenal gland to stimulate release of aldosterone
• Aldosterone acts on kidneys to stimulate reabsorption of sodium and water.
• This increases BV and MAP by increasing SV

Question 11

What is Angiotensin Ii

Answer 11

• Constricts blood vessels = increase TPR & MAP
• Stimulates thirst and release of ADH
  -Stimulates release of aldosterone

Question 11

What is Hypertension and Hypotension

Answer 11

HYPERTENSION = No known cause that raises BP. Due to high salt diet and more fluid retention. If you have kidney disease, angiotensin mechanism will not work meaning you’ll have hypertension. Hormonal changes e.g Cushing syndrome by increased action of SNS. Tumours of adrenal gland by increased production of adrenaline

HYPOTENSION - Autonomic neuropathy by ineffective sympathetic control of BP. Cardiac failure. Overmedication for hypertension. Adrenocortical insufficiency due to lack of ability to hormones e.g cortisol and aldosterone