Heart sounds and ECGs Flashcards by Lian Dimaro

Explain the 3rd heart sound and ddx

Due to rapid ventricular filling

May be normal if

Think volume overload

Causes: congestive cardiac failure, MR, AR, large anterior MI

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Explain and list causes for 4th heart sound

Due to poorly compliant ventricle

Always abnormal

Cannot occur in AF (requires atrial contraction)

Think pressure overload

Causes: AS, HTN, HOCM, post MI fibrosis

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Causes of mitral stenosis

Rheumatic heart disease (99%)

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Causes of mitral regurgitation

RHI

Valve prolapse

Papillary muscle rupture (e.g. MI)

LV dilation

Marfan’s

SLE

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Causes of aortic stenosis

RHD

Calcified bicuspid valvve (age 50-60)

Calcified tricuspid valve (aged 70+)

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Causes of aortic regurgitation

RHD

Syphilis - luetic heart disease

Bicuspid valve

Hypertension

Aortic dissection

Marfan’s

Ankylosing spondylitis

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The absence of P-waves and an irregular rhythm would suggest a diagnosis of…..

Atrial fibrilation

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How do you calculate HR from an ECG

Count the number of large squares in an RR-interval - Divide 300 by this number.

E.g. If there were 3 large squares in an R-R interval - 300/3 = 100bpm

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What would it suggest if lead I became more positive than lead II and lead III became negative?

Left axis deviation

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What would it suggest if lead I became negative, and lead III became more positive than lead II?

Right axis deviation

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A fixed prolonged PR interval is seen in what?

FIRST DEGREE AV BLOCK

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ST-depression classically suggests…

Myocardial ischaemia

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If a patient had an abnormally short PR-interval what would be a likely cause?

Wolf Parkinson White syndrome

A short PR-interval indicates abnormally short conduction time between the atria and ventricles. This is caused by the presence of an accessory pathway between the atria and ventricles. Wolf parkinson white syndrome is an example of this kind of disorder. In WPW the an accessory pathway known as “the bundle of kent” is present. Most individuals are asymptomatic however there is a risk of sudden death.

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What view of the heart do leads II, III, aVF represent?

Inferior

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What is a common cause of right axis deviation?

Right ventricular hypertrophy

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What is the normal duration of a QRS complex?

In most healthy individuals you would expect QRS complexes to be around 0.12 seconds (3 small squares)or slightly less.

If a QRS complex lasts longer it is described as a “wide QRS” and can be a sign of inefficient conduction of the ventricles such as bundle branch block.

What is the duration of a normal PR-interval?

In normal individuals the PR-interval is between 0.12-2.0 seconds (3-5 small squares).

A PR interval longer than this can suggest the presence of heart block and a short PR-interval can suggest an accessory pathway between the atria & ventricles e.g. WPW syndrome

Which artery is most likely to be affected if ST elevation in seen in leads V3 & V4?

Leads V3 & V4 view the heart anteriorly. Therefore ST elevation in these leads suggests an anterior infarct.

The anterior portion of the heart is supplied mainly by the left anterior descending artery therefore this is most likely to have been affected.

What view of the heart do leads V3 & V4 represent?

If the PR interval is fixed but there are dropped beats?

MOBITZ TYPE 2 SECOND DEGREE HEART BLOCK

(clarify that by the frequency of dropped beats e.g 2:1, 3:1, 4:1)

If a rhythm is described as sinus, what does this indicate?

P-wave precedes each QRS-complex.

However a rhythm can still be irregular even if it’s sinus.

What is often the earliest ECG change seen during myocardial infarction?

Tall peaked T-waves can suggest a number of abnormalities.

If seen in all leads then they usually suggest the individual has hyperkalaemia. However if tall T waves are seen in a particular group of leads it suggests early MI. The tall T waves are due to potassium leaking through the damaged membrane over the infarcted area

If the duration of the PR interval becomes progressively prolonged with alongside regular dropping of QRS complexes, what does this suggest?

Second degree - Mobitz Type 1 - Heart Block is a disease of the AV node.

It is seen as progressive prolongation of the PR-interval and then regularly dropped QRS complexes.

What view of the heart do leads V1 & V2 represent?

Septal

If ST-elevation was seen in leads II, III & aVF what would it suggest?

Leads II, III & aVF all look at the heart in the inferior plane. Therefore ST-elevation in only these leads suggests that the inferior portion of the heart has had an infarction.

What does ST-elevation suggest?

What view of the heart do leads I, aVL, V5, V6 represent?

Lateral

What is the common cause of left axis deviation?

Left axis deviation is rarely the result of left ventricular hypertrophy and more often due to defects in the conduction system of the heart

What’s a normal heart rate?

Normal = 60 – 100 bpm Tachycardia \> 100 bpm Bradycardia \< 60 bpm

If the PR interval slowly increases then there is a dropped beat?

MOBITZ TYPE I SECOND DEGREE AV BLOCK (Wenckebach)

If the P waves and QRS complexes are completely unrelated, this is ....

THIRD DEGREE AV BLOCK (complete heart block)

List the anatomical locations of various heart blocks

**First degree AV block**: Occurs between the SA node and the AV node (i.e. within the atrium) **Second degree AV block**: **Mobitz I (Wenckebach)** – occurs IN the AV node. This is the only piece of conductive tissue in the heart which exhibits the ability to conduct at different speeds. **Mobitz II** – occurs AFTER the AV node in the bundle of His or Purkinje fibres. **Third degree AV block**: Occurs anywhere from the AV node down causing complete blockage

What are the different aspects of the QRS complex?

WIDTH Width can be described as NARROW (\< 0.12ms) or BROAD (\> 0.12ms) HEIGHT Small complexes are defined as \< 5mm in the limb leads or \< 10 mm in the chest leads. Tall complexes imply ventricular hypertrophy MORPHOLOGY This is where you assess the individual waves of the QRS complex.waves

Ddx ST depression

Anxiety Tachycardia Digoxin toxicity Haemorrhage, Hypokalaemia, Myocarditis Coronary artery insufficiency MI As a result you must take this ECG finding & apply it in the context of your patient.

What constitutes a tall T wave and what is it associated with?

*T waves are tall if they are:* \> 5mm in the limb leads and \> 10mm in the chest leads (the same criteria as ‘small’ QRS complexes). *Tall T waves can be associated with*: Hyperkalaemia (“Tall tented T waves”) Hyper-acute STEMI

Ddx inverted T waves

Ischaemia Bundle branch blocks (V4 – 6 in LBBB and V1 – V3 in RBBB) PE LVH (in the lateral leads) HCM (widespread) General illness

What is a U wave and when might you see it?

The U wave is a \> 0.5mm deflection after the T wave best seen in V2 or V3. These become larger the slower the bradycardia – classically U waves are seen in various electrolyte imbalances or hypothermia, or antiarrhythmic therapy (such as digoxin, procainamide or amiodarone).

Which leads correspond with the different areas and arteries of the heart?

Inferior - II, III, aVF - RCA Anterior apical- V3, V4 - Distal LAD Anterior Septal - V1, V2 - LAD Anterior Lateral - I, aVL, V5, V6 - Circumflex Extensive anterior - I, aVL and V2- V6 - Proximal LCA True posterior - tall R in V1 - RCA