Electrogardiography

Question 1

What is a normal axis on EKG

Answer 1

Between negative 30° and positive 90°

Question 2

What is the normal pattern of cardiac depolarization?

Answer 2

Initial depolarization is left to right across the septum followed by LV and RV free wall, with LV dominating.

Question 3

What are the criteria for right bundle branch block?

Answer 3

1. QRS greater than 120 ms (100 – 119 equals incomplete)
2. rSR’ in our precordial leads (V1, V2).
3. Wide S wave in one V5 and V6.
4. +/- ST depression or T-wave inversion in R precordial leads.

Question 4

What are the criteria for left bundle branch block?

Answer 4

1. QRS greater than or equal to 120 ms
2. Broad, slurred, monophasic R in I and V6 (+-S if cardiomegaly).
3. Absence of Q in I, V5 and V6.
4. Displacement of ST and T wave opposite major QRS deflection.
5. +/- PRWP, LAD, Q’s in the inferior leads.

Question 5

What is Bazett’s Formula?

Answer 5

QTc=QT/Square root sign RR

Question 6

A normal QTc Is less than or equal to______.

Answer 6

440ms

Question 7

Name the major drugs that cause QT prolongation.

Answer 7

1. Anti-arithmetic’s: class I A and class III.
2. Antipsychotics: (Phenothiazines, haloperidol, atypical antipsychotics) lithium.
3. Antimicrobials: macrolides, quinolones, voriconazole, pentamidine, atovaquone, Chloroquine, amantadine, foscarnet.
4. Anti-emetics: Droperidol, Serotonin antagonists
5. Other: methadone, alfuzosin.

Question 8

Name nonpharmacologic causes of prolonged QT.

Answer 8

Electrolyte disturbances: hypocalcemia, possibly hypokalemia, possibly hypomagnesemia.
Autonomic dysfunction: intracranial hemorrhage, Stroke, carotid endarterectomy, neck dissection.
Congenital: long QT syndrome from potassium sodium channel channelopathy (Maybe associated with deafness).
Coronary artery disease, Cardiomyopathy, bradycardia, high-grade AVB, hypothyroidism, hypothermia.

Question 9

Name the different criteria schemes for left ventricular hypertrophy by EKG

Answer 9

Sokolow-Lyon: S in V1 + R in V5 or V6 > 35mm
Cornell: R in aVL + S in V3 > 28 mm in men or >20 mm in women.
Other: R in aVL >11mm in men, >9mm in women; if LAD present then R in aVL > 13mm and S in III >15mm.
Romhilt-Estes point score system: 4 points= probable, 5 points= definite.

Question 10

Name the EKG criteria for RVH.

Answer 10

R >S in V1 or R in V1 > 7 mm, S and V5 or V6 > 7 mm.

Dropping R/S ratio across precordium.

Question 11

What is EKG criteria for biventricular hypertrophy?

Answer 11

Right axis deviation > +110° (LVH + RAD)

Question 12

What is the differential diagnosis for a dominant R waves in V1or V2?

Answer 12

Right ventricular hypertrophy, hypertrophic cardiomyopathy, posterior MI, Duchenne muscular dystrophy, right bundle branch block Wolfe Parkinson white, dextroversion, lead misplacement, normal variant.

Question 13

What is the definition of poor R wave progression?

Answer 13

Loss of anterior forces without Frank Q waves (V1-V3). R wave in V3 < 3mm.