ECG

Question 1

P wave

Answer 1

atrial depolarization

Question 2

PR interval

Answer 2

atrial depol to ventricular depol (<200 msec)

Question 3

QRS complex

Answer 3

ventricular depolarization (<120 msec)

Question 4

QT interval

Answer 4

ventricular depol to ventricular repol (includes ventricular contraction)

• reading the USMLE chart makes it seem like about 400 msec

Question 5

T wave

Answer 5

ventricular repol (T-wave inversion = MI)

Question 6

J point

Answer 6

junction between end of QRS and start of ST segment

Question 7

ST segment

Answer 7

isoelectric (flat), ventricles depolarized

Question 8

U wave

Answer 8

prominent in hypokalemia, bradycardia (after the T wave)

Question 9

Conduction pathway

Answer 9

SA node -> atria -> AV node -> bundle of His -> bundle branches -> Purkinje fibers -> ventricles

Question 10

Which bundle branch divides into anterior and posterior fascicles?

Answer 10

Left BB

Question 11

Which nodes is the “pacemaker”?

Answer 11

SA

Question 12

Pacemaker rates

Answer 12

SA is faster than (>) AV is faster than (>) His/Purkinje/ventricles

Question 13

Conduction rates

Answer 13

Purkinje > atria > ventricles > AV node

Question 14

HR on EKG boxes

Answer 14

1 big box = 300 beats/min (fast)
2 big boxes = 150
3 boxes = 100
4 boxes = 75
5 boxes = 60

Any less than 3 boxes is tachy.
Nml: 3-5 boxes

Question 15

Long QT is caused by:

Answer 15

• drugs
• hypoK+
• hypoMg+2
• congenital abnormalities (K+ chan mutations: Romano-Ward/Jervell and Lange-Nielsen syndrome)

Question 16

Treatment for torsades de pointes

Answer 16

magnesium sulfate (which you can kind of remember by hypoMg+2 leading to long QT)

Question 17

What drugs prolong QT? ABCDE

Answer 17

antiArrhythmics (class IA, III)
antiBiotics (macrolides)
anti"C"ychotics (haloperidol)
antiDepressants (TCAs)
antiEmetics (odansetron)