Lecture 28 - ECG Basics

Question 1

Unipolar EKG leads have one ____ (positive or negative?) electrode and a Neutral reference point. Bipolar leads have one Positive and one Negative lead. How does the deflection appear on the EKG if the current in the heart travels toward the Positive lead? How does it appear if it travels Perpendicular to the positive lead?

Answer 1

Positive

If it travels toward the Positive lead –> positive deflection

If it travels perpendicular –> Isoelectric deflection

Question 2

Depolarization moves from the ______ (which layer of the heart?) toward the _____. Repolarization is the opposite.

Answer 2

Endocardium toward the Epicardium

Question 3

Only limb leads ____, ____, and _____ are BIPOLAR. The rest are unipolar. The Right Arm (RA) lead is always ______ (Positive or Negative) and the Left Leg (LL) lead is always _____ (Positive or Negative?).

Answer 3

I, II, and III

RA –> Negative

LL –> Positive

Question 4

Electrical activity is always tracked from _____ (Positive or Negative?) to _____ (Positive or Negative?)
.

Answer 4

Positive to Negative

Question 5

The tracing of electrical activity through the EKG leads provides information about the ______ ventricle of the heart. Thus, lead I provides info about the _____ wall; Leads II + III + aVF provide information about the _____ wall. The aVR lead should always be looked at for _____ elevation.

Answer 5

Left Ventricle

Lateral wall

Inferior wall

ST elevation –> indicates MI

Question 6

The 6 chest leads are called the Percordial leads, and their axes lie perpendicular to the Frontal plane of the Limb leads. Percordial leads V1 through V4 provide info about the _____ wall of the Left Ventricle (V1 and V2 also provide info about the ________ septum); V5 and V6 monitor the _____ wall.

Answer 6

Anterior wall

Interventricular septum

Lateral wall

Question 7

Look to the V4R lead to identify Coronary Artery occlusion.

ST elevation and Positive T-waves indicate proximal occlusion of the ______.

Normal ST segments and Positive T-waves indicate _____ occlusion.

Normal ST segments and Negative T-waves indicate ______ artery occlusion.

Answer 7

RCA

RCA occlusion

Circumflex

Question 8

Ischemia and/or Infarction is represented in ALL leads by _____ elevation, ____-wave inversion, or the presence of ___ waves.

Keep in mind ______ infarction accompanies Inferior infarction about 50% of the time, and Right Ventricle involvement occurs in about 40% of ______ wall infarcts.

Answer 8

St elevation

T-wave inversion

Q waves

Posterior infarction

Inferior wall infarcts

Question 9

Most patients with Ventricular Tachycardia have issues with Phase 4 of the AP, so Inward-rectifier ____ channels are dysfunctional.

Answer 9

Inward-rectifier K+ channels

Question 10

The AV node has an intrinsic decremental property, meaning the faster you stimulate it, the ______ it conducts.

Answer 10

Slower

Question 11

A normal P-wave in an EKG is approximately ___ small boxes long and ___ to ____ boxes high (0.08s long and 0.2-0.25mV). If the ____ node is dysfunctional or there is hypertrophy of the _____, this wave will appear different.

Answer 11

2 small boxes long

2 to 2.5 boxes high

SA node

Atria

Question 12

Normally, the P wave shows _____ deflection in lead II, _____ deflection in the aVR lead, and is regularly spaced in Rhythm strips.

Answer 12

Positive in lead II

Negative in aVR

Question 13

The __-__ interval is normally 4 to 5 small boxes long, and it represents the time necessary for conduction from the SA node all the way through the Purkinje fibers (the entire conduction system). When it is prolonged, it is usually indicative of some type of ____ block.

Answer 13

P-R interval

AV block

Question 14

The QRS complex represents ____ depolarization and is typically 2 to 2.5 small boxes long. If it is 3 small boxes or longer, this may indicate a ____ ____ block.

Answer 14

Ventricular depolarization

Bundle Branch block

Question 15

Q waves represent the normal Left-to-Right depolarization of the ______ _____. They are considered pathological if they are more than ___ box long, more than ____ boxes deep, are more than ____% of the depth of QRS complex, or are seen in leads V__ to V___.

Answer 15

Interventricular Septum

1 box long

2 boxes deep

25% of the QRS

V1 to V3

Question 16

The ST segment represents the time delay between systole and repolarization of the ventricle. It is the ONLY _____ segment (falls on the baseline). ST elevation is indicative of MI.

Answer 16

Isoelectric

Question 17

T wave represents Ventricular repolarization and is usually _____ deflected. If it is flattened or inverted, it represents _____.

Answer 17

Positively deflected

Ischemia

Question 18

The QT interval is measured from the beginning of the Q wave to the end of the T wave, and it represents the time from Ventricular depol through repol. It is INVERSELY proportional to heart rate, so as heart rate increases, QT interval _____. QT prolongation is associated with increased risk of Ventricular _____, especially ____ ___ _____.

Answer 18

Decreases

Ventricular Arrhythmia

Torsades de Pointes

Question 19

The QT interval should be measured in either lead ____ or V__-V__.

Answer 19

Lead II or V5-V6

Question 20

Long QTS1 (LQTS) and 2 are both ____ of function mutations in K+ channels. For which one does Exercise most often cause Sudden Cardiac Death (SCD), and for which is Emotional stress the cause?

LQTS3 is a ____ of function of Na+ channel. SCD usually occurs during ____.

Answer 20

Gain of function

LQTS1 –> Exercise

LQTS2 –> Emotional Stress (Particularly loud noises)

Gain of function

LQTS3 –> sleep

Question 21

Pregnant women are most susceptible to SCD from LQTS__.

Answer 21

LQTS2

Question 22

_____ ____ can be used to treat LQTS1 and 2, but not LQTS3.

Answer 22

Beta Blockers