PHSL labs

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

polarity:

• depolarisation towards the positive electrode = positive deflection

• repolarisation away from the positive electrode = positive deflection

amplitude: due to the direction of the eletrical activity compared to the ECG leads

• similar direction = larger amplitude (ventricular depolarization and lead two) - same in visa versa

What factors move the MEA anticlockwise

• changing the position of the heart: short, broad torso, pregnancy, gastric distension, obesity

• by changing the balance of electrically active tissues between the LV and RV: LV hypertrophy (fitness, aortic stenosis, hypertension (age)), myocardial infarction on the right side

What factors moves the MEA clockwise?

• by changing the position of the heart: thin, tall torso, moving from supine to upright, inverted heart

• by changing the balance of electrically active tissue in the LV and RV: right ventricular hypertrophy (pulmonary hypertension, high altitude), myocardial infarction on the left side

what is a normal range of the PR interval?

0.12-0.2 seconds (each square is 0.04 seconds)

describe what happens to the heart rate over a breathing cycle?

breathe in = increase in HR
breathe out = decrease in HR

What are Korotkoff sounds?

sounds of the heart created through turbulent/pulsatile blood flow through a compressed artery. Pulsatile sounds disappear when the pressure of the inflated cuff falls below diastolic pressure, as laminar flow is restored