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EKG Reference Manual – 5/5/11

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PRINT HARD COPY AND BRING TO EACH EKG SESSION

EKG Reference Manual Use this manual FIRST to answer questions that arise as you work through EKG Series #1 & 2 with HyperGram and the “Yellow Card”. Table of Contents Page 2. Summary of Basic Concepts: What must an MS3 master. Naming the waves in QRS Complex: Definition of the Q, the R, & the S wave. Rules: I and II rule for axis; 6 sec. rule for Heart Rate Page 3. Origin of QRS: Sequence of vectors during Ventricular Depolarization. Qualitative description of the 3 QRS abnormalities (BBB, L/RVH, Q-MI). Page 4. The single condition that must be present in BBB. (sine qua non). Diagram: R & L BBB. “What happens when” determines the shape of the QRS. Page 5. How to determine which bundle is blocked using the concept of “The Vector from the Late Ventricle”. Learn to NEVER confuse RBBB and LBBB. Page 6. Ventricular Hypertrophy, the concept. Why you cannot make the diagnosis of ventricular hypertrophy with BBB- not with LBBB, not with RBBB. Why you CAN make the diagnosis of Q-MI with RBBB but NOT with LBBB. Page 7. Q-Wave Myocardial Infarction Scar: the loss of initial vector. How to determine if a Q wave is significant: wide but not too wide. The 2 big Oooops! Calling LBBB an MI; Confusing an S wave with a Q wave. Page 8. A coronary anatomy based approach to determination of MI site: typical leads involved for the usual Left Ventricular MIs. Ischemia, Injury, Infarction. ST elevation MI vs. Early Repolarization – How to tell the difference. Page 9. How to determine if T waves are normal or abnormal. How to determine atrial hypertrophy or enlargement, Left and Right. Page 10. How to determine if the QT is prolonged, a quick technique. The EKG changes with Hyper and Hypokalemia. Page 11. A guide to Basic Arrhythmias. (How to recognize each easily) Page 12. Alphabetical Index by Subject

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EKG INTERPRETATION – MS3 COMPETENCIES What Must an MS3 Master? What will be Tested at the End of the Medicine Clerkship 1. Be Systematic (Know the 10 point Interpretation System) 2. Differentiate Normal from Abnormal without the “Yellow Card” 3. Know a Few Common Abnormalities A. Ectopy: PVC, PAC or Premature Supraventricular Complex B. Heart Block (First, Second and Third Degree AV Block) C. Atrial Fibrillation (and Flutter vs. reentrant PSVT) D. The 3 QRS Abnormalities A. Ventricular Hypertrophy (LEFT and right) B. BBB (Differentiate LBBB from RBBB) C. Q Wave Myocardial Infarction (Inferior, Septal, Anterior, Lateral Wall locations) E. Acute Current of Injury (ST elevation MI) ______________________________________________________________

Basic Concepts – Naming the waves of the QRS Complex

Infarction

R

First Upward Deflection

Q

FIRST Downward Deflection

S

Downward Deflection AFTER the R

RSR’ (R, S, R prime)

Q or QS. Not an S

Slurred R

RULES: AXIS - I and II rule: If leads I and II are both positive, the axis is normal (-30° to +90°). If not, check if aVL is + (=LAD) or if III is + (=RAD). HEART RATE - 6 second RULE: Count the # of QRS complexes in 6 sec (150mm) and x 10. (Use calipers; 25mm = 1 sec). First QRS is “zero”!!!

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The Genesis of the QRS Complex

B Sequence of Electrical Vectors

A Sequence of

Ventricular Depolarization 4 1

Generated during Ventricular Depolarization

4

3

Time

1

2

2 3

Time

3

3

3 3

C Recording of the

Sequence of Electrical Vectors Generated during Ventricular Depolarization

Recording Electrode

2 1

4

Time 1-2-3-4 _______________________________________________________________

The Three QRS Abnormalities – Qualitative Description 1. Bundle Branch Block Left and Right Ventricles Depolarize Separately. The ventricle with the blocked bundle depolarizes late. 2. Ventricular Hypertrophy Too Much Left or Right Ventricular Muscle. The hypertrophied muscle produces a large electrical vector that alters the magnitude (LVH) or direction (RVH) of the mean QRS vector. 3. Q Wave Myocardial Infarction Death of a Large Segment of LEFT VENTRICULAR Muscle. There is a loss of electrical vector from the dead muscle that is most easily seen during the first 0.04 sec of LV depolarization.

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Minimum Criterion for Bundle Branch Block: Increased Duration of the QRS Complex !! The QRS Interval Must be Wide (≥0.12 sec.) If the QRS Duration is not Long…at least 3 little boxes IT IS NOT BBB !! BBB ( = 0.12 sec) NOT BBB

RBBB

LBBB 6

4 1 7

3

2

5

1

2

4

6 5

3 3

LV depolarizes NORMALLY; RV depolarizes LATE

RV depolarizes NORMALLY; LV depolarizes LATE

RV depolarization

LV depolarization

is ABNORMAL

is ABNORMAL

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HOW TO DETERMINE WHICH BUNDLE IS BLOCKED To determine which bundle is blocked, look at the last part of the QRS complex. The vector from the ventricle depolarizing last (terminal vector) is unopposed. It determines what the last half of the QRS will look like. Look at leads at the extremes, V1 and V6. Does the vector from the second half of the QRS complex point toward V1 (large R prime) or away from V1 (deep QS wave)? Look atV6. Does the terminal vector point toward V6 (large R wave, no S), or away from V6 (deep S wave)? Understanding the physiology explains why RBBB has an rSR' in V1 and a deep S in V6. And why LBBB produces a QS in V1 and a Large R in V6. If you measure a wide QRS and a L/RBBB pattern is absent, Measure again!

Bundle Branch Block

Normal LV and RV Simultaneous

Bundle Branch Block

RBBB

Terminal Vector

LV----TIME----RV

Terminal Vector

LBBB RV----TIME----LV

Bundle Branch Block widens the QRS complex AND alters the TERMINAL QRS Vector Terminal Vector

Terminal Vector

RBBB

RBBB

V1 LBBB

V6 LBBB

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Ventricular Hypertrophy Normal

LVH

RVH

LV RV

RV

LV

LV

Mean Vector

Mean Vector

LVH alters the MAGNITUDE of the Mean QRS Vector

Mean Vector

RVH alters the DIRECTION of the Mean QRS Vector

Normally, simultaneous RV & LV vectors compete to create the mean QRS vector. With LVH and RVH one of these vectors has more influence on the mean QRS vector than the other. To see the effects of this competition of the vector from one hypertrophied ventricle with the other ……… BOTH VENTRICLES MUST DEPOLARIZE AT THE SAME TIME.

RBBB

LBBB 6

4 1 3 2

7

5

1

2

4

6

3 5

LV and RV are NOT simultaneous In RBBB you cannot Dx HYPERTROPHY

BUT …LV depolarization is NORMAL *In RBBB you CAN Dx LV MI Scar*

3 LV and RV are NOT simultaneous In LBBB you cannot Dx HYPERTROPHY LV depolarization is ABNORMAL In LBBB you CANNOT Dx LV MI Scar

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Normal

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Myocardial Infarction Scar

Normal : Initial .04 sec.Vector in direction of mean QRS Vector

Initial Vector AWAY from Infarction

Q Wave

Q Wave Myocardial Infarction alters the

INITIAL QRS Vector

The Q wave MI scar represents an absent initial vector (due to dead LV tissue) during the initial 0.04sec.of a normally depolarizing LV. You can see this initial (absent) vector since all of the LV subendocardium depolarizes at the same time. To make the diagnosis of an LV Q wave myocardial infarction THE LV MUST DEPOLARIZE NORMALLY.

In RBBB

In LBBB

LV depolarization is normal. LV depolarization IS ABNORMAL In RBBB you CAN Diagnose Q-MI. In LBBB you can NOT Diagnose Q-MI.

Q Wave – Is it significant or not? Too wide & LBBB? Not wide enough (