Cardiac cycle, ECGs & MurmursBECKY & SHEF

ECGs

What does an ECG show?

Normal electrical activity of the heart

Abnormal electrical activity of the heart Abnormal Heart Rhythms Myocardial Infarction Enlarged Heart

ECG Leads

Limb leads Coronal plane

Placement: Right arm Left arm Left leg Right leg (Neutral electrode – serves as reference electrode)

Chest leads Transverse/Horizontal place

Placement: (See next)

Chest leads positioning

V1 - Right 4th ICS, just lateral to sternum V2 - Left 4th ICS, just lateral to sternum V3 - Between electrodes V2 & V4

V4 – 5th Left ICS, MCL V5 - Between electrodes V4 & V6

V6 – 5th Left ICS, MAL

Summary of limb lead placementElectrode Electrode placement

RA Right arm, avoiding thick muscle.

LA Left arm, avoiding thick muscle.

RL Right leg, lateral calf muscle.

LL Left leg, lateral calf muscle.

V1 Fourth right intercostal space, just lateral to the sternum

V2 Fourth left intercostal space, just lateral to the sternum

V3 Between electrodes V2 and V4.

V4 Fifth left intercostal space, mid-clavicular line.

V5 Between electrodes V4 and V6.

V6 Fifth left intercostal space, midaxillary line.

Lead view of the heart

12-lead ECG

Analysing ECGs

ECGs

1

45

2

3

8

6

7

9

10

Atrial depolarisation

Ventricular depolarisation

Ventricular repolarisation

STEMI vs Non-STEMI (NSTEMI)NSTEMI account for about 30% and STEMI about 70% of all MI’s.

NSTEMI – Occlusion of a minor coronary artery or partial occlusion of a major coronary artery

STEMI – Complete occlusion of a major coronary artery.Transmural damage.

Symptoms – Chest pain, vomiting, sweating, difficulty breathing

SAME IN BOTH

Theory!

Injured cells are leaky, will repolarise quicker than the healthy cells.

Injured area repolarises quicker, causes a flow of electrical signal towards the injured area – detectable on an ECG

Absence of electrical activity. A myocardial infarction can be thought of as an electrical 'hole' as scar tissue is electrically dead.

Hyperkalaemia

High/tented T wave Prolonged PR interval Widened QRS complex P waves low or absent Depressed ST segment Atrial standstill Intraventricular block Bradycardia Ventricular fibrillation Asystole

Hypokalaemia

Low T wave

High U wave

Low ST segment

Approach to treatment of hyperkalaemia & hypokalaemia

Hyperkalaemia (≥7.0 mmol/L, or any increase associated with ECG changes) Immediate

Stop any K+ supplements or K+ conserving drugs Administer calcium gluconate intravenously (for cardiac protection)

Short term Insulin/dextrose to encourage K+ uptake into cells – MONITOR GLUCOSE Salbutamol (Beta2-agonist)

Long term Loop diuretics Calcium resonium Dialysis

Hypokalaemia (<3.5 mmol/l, but may not have symptoms until <2.5 mmol/l) Change diet (Bananas very K+ rich) Change/stop diuretic Can infuse with K+ if needed

Cardiac Cycle

1

2

34

6

5

A

(See notes below for full summary)

B

C D

Heart Sounds & Murmurs

Heart Sounds

I + II + 0

S1 (‘Lub’) + S2 (‘Dub’) + No added heart sounds S1 – Closure of mitral & tricuspid valve S2 – Closure of aortic and pulmonary valves

S3 Oscillation of blood back and forth between ventricle walls Occurs following S2 Suggestive of congestive heart failure

S4 Atria contracting forcefully in an effort to overcome an abnormally stiff or hypertrophic ventricle Occurs just before S1 (Mitral valve closure) Suggestive of a failing or hypertrophic ventricle

Heart valve auscultation points

What is a murmur?

Turbulent flow of blood strong enough to produce audible noise

AS MR. ARMS SAYS…

ASMR|ARMSSYSTOLE DIASTOLE

AS – ejection systolic (Mid-systolic) MR – pansystolic AR – early diastolic MS – mid-diastolic