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I've got hypertension > Lab 1 > Flashcards

Lab 1 Flashcards

1
Q

What five things does an ECG contain information about?

A
  • the normal conduction of the cardiac action potential
  • possible arrhythmias, and disorders of cardiac conduction
  • hypertrophy of the ventricles and atria
  • existence and location of ischaemic areas in the heart
  • changes in the myocardium caused by drugs
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2
Q

Where are the standard limb leads placed? Which end is positive and which is negative?

A

Lead 1: has the negative on the right arm and positive on the left arm
Lead 2: has the negative on the right arm and the positive on the left leg
lead 3: had the negative on the left arm and the positive on the left leg

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3
Q

What are standard limb leads?

A

These are bipolar leads that record the voltage between any two corners of the Einthoven’s triangle

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3
Q

What ate standard limb leads?

A

These are bipolar leads that record the voltage between any two corners of the Einthoven’s triangle

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4
Q

What are augmented limb leads?

A

These are unipolar leads that record the voltage difference between one apex of the Einthoven’s triangle and a reference formed by the electrodes on the other two apices of the triangle

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5
Q

What are the names of the three different augmented leads and where is the positive and negative located?

A

AVR: the positive end is at the right arm and the negative end is halfway between the left arm and the left leg
AVL: the positive end is at the left arm and the negative end is halfway between the right arm and the left leg
AVF: the positive end is at the left leg and the negative end is halfway between the left arm and right arm

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5
Q

What are the names of the three different augmented leads and where is the positive and negative located?

A

AVR: the positive end is at the right arm and the negative end is halfway between the left arm and the left leg
AVL: the positive end is at the left arm and the negative end is halfway between the right arm and the left leg
AVF: the positive end is at the left leg and the negative end is halfway between the left arm and right arm

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6
Q

When depolarisation travels towards/away from a positive electrode and away from a negative electrode is causes a positive deflection

A

towards

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7
Q

Taller, thinner people tend to have an anatomically more horizontal or vertical heart?

A

more vertical heart and more vertical electrical axis

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8
Q

What will the ECG appear as?

A

It will appear as small positive and negative changes (waves and complex) in skin potential that coincide with the depolarisation and repolarisation occurring in the atria and ventricles

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9
Q

The amplitude of each component of an ECG depends on what?

A
  • the location of the ECG electrodes
  • the direction of the wave of activity in the heart (depolarisation or repolarisation) relative to the polarity of the recording electrodes
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9
Q

The amplitude of each component of an ECG depends on what?

A
  • the location of the ECG electrodes
  • the direction of the wave of activity in the heart (depolarisation or repolarisation) relative to the polarity of the recording electrodes
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10
Q

Explain why the amplitude and polarity of the P, QRS and T waves vary in your recordings of the 6 different limb leads

A

Polarity: the polarity will either be positive or negative.
Amplitude: this depends on the location of the electrodes and the direction of the activity in the heart relative to the polarity of the recording electrodes. If it is a depolarisation towards the positive electrode, it is a positive deflection. If it is a repolarisation away from the positive electrode, it is a positive deflection

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11
Q

Why does the recording of the aVR lead appear to be an inversion of the recording of the standard limb lead 2?

A

This is because the negative electrode is on the left ankle and the positive electrode is on the right arm which is the opposite to lead 2. This means that the depolarisation towards the positive electrode is seen as a positive deflection in lead 2 but it is seen as a negative deflection of aVR.

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12
Q

Why is the amplitude of a typical ECG R-wave (1 mV) is less than 1% of the amplitude of the action potential recorded from a single myocardial cell (100mV)?

A

This is because the ECGs are recorded on the skin and the amplitude is lost. The heart electrical activity is isolated from the body by the pericardium and cartilage around the valves. If it was not isolated, our skeletal muscle would contract every time the heart beats so the heart is insulated with the cardiomyocytes and the cartilaginous valves

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13
Q

What is the mean arterial axis of the heart?

A

This is the mean of all the instantaneous vectors from depolarising cardiac muscle fibres that are generated when the ventricles depolarise.

14
Q

What is the MEA reference range?

A

-30° and +120°

15
Q

How do you calculate the net amplitude of the QRS complex?

A

net amplitude = R wave amplitude - Q wave - S wave

16
Q

How do you use Einthoven’s triangle to find the MEA?

A

You plot the calculated net amplitudes along the appropriate side of the triangle for each lead (positive net amplitude values are measured to the right of the midpoint and negative values to the left).
Draw lines perpendicular to the direction of each vector. Another line is drawn from the centre of the triangle to the intersection of these two perpendicular lines and this is the vector for the MEA.

17
Q

What effect does breathing have on the measurement of the MEA?

A

When you breathe out, the heart is pushed more horizontally and when you breathe in, the heart is pushed more vertically

18
Q

What could make the heart is more horizontal?

A
  • short, broad torso
  • pregnancy
  • obesity
  • left ventricular hypertrophy
  • fitness
  • aorticstenosis
  • hypertension
  • myocardial infarction on the left side
19
Q

What could make the heart more vertical?

A
  • tall, thin torso
  • moving from supine to upright
  • inverted heart
  • right ventricular hypertrophy
  • pulmonary hypertension
  • high altitude
  • myocardial infarction on the left side
20
Q

What is AV block? How many degrees are there?

A

There are three degrees of AV block which describe the increasingly abnormal AV conduction and associated heart rhythm

21
Q

During a 2nd degree AV block (Type 1) the P-R interval progressively increases until a QRS complex is skipped. True or false?

A

True

I've got hypertension (47 decks)

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