# ECG Flashcards

What does the p-wave represent

Atrial depolarisation

What causes the p-wave

SA node

How many squares is 1 second

5

What does 5 big squares on the graph represent

1s

What does 1 big square represent

0.2 seconds (200ms)

What is 0.2s on the graph

1 big square or 5 small squares

What is 5 small squares

0.2 seconds

What is 0.04 s (40ms)

1 small square

What is 1 small square

0.04 s 40ms)

What are the typical settings on a voltage time graph

Speed

Voltage

Speed = 25 mm/sec

Voltage = 10 mm/mV

What voltage does one big square represent

0.5 mV

What voltage does 2 big squares represent

1 mV

Used a voltage time graph how do you calculate rate (bpm)

300/no. of large squares between cardiac cycle

OR

cycles in 10 seconds x 6

What is the equation of Ohm’s law

V = IR

Voltage = current x resistance

On an ECG lead what does a positive deflection show

Net current flow towards lead

On an ECG what does a baseline/isoelectric point show

No net current flow in direction of lead

On an ECG what does a negative deflection show

Nett current flow away from lead