EKG Basics and Interpretation - part 5 doc

• "Complete" LBBB" has a QRS duration >0.12s oriented leftward and posteriorly because the left ventricle is depolarized after the right ventricle • Terminal S waves in lead V1 indicati

• "Complete" LBBB" has a QRS duration

>0.12s

oriented leftward and posteriorly because the

left ventricle is depolarized after the right

ventricle

• Terminal S waves in lead V1 indicating late

posterior forces

• Terminal R waves in lead I, aVL, V6

indicating late leftward forces

QRS Axis

• Average direction of ventricular

activation in the frontal plane

• First find the isoelectric lead if there is

one

• QRS axis is perpendicular to that lead's

orientation

Atrial Enlargement

• Right atrial enlargement

– P wave amplitude >2.5 mm in II and/or

>1.5 mm in V1

• Left atrial enlargement

– P wave duration > 0.12s in frontal plane (usually lead II)

LV Hypertrophy

• > QRS amplitude

• Delayed intrinsicoid deflection in V6 (i.e., time from QRS onset to peak R is >0.05 sec)

• Widened QRS/T angle (i.e., left ventricular

strain pattern)

• Leftward shift in frontal plane QRS axis

• Evidence for left atrial enlargement

• Cornells voltage criteria

S in V3 + R in aVL > 24 mm (men)

S in V3 + R in aVL > 20 mm (women)

ESTES Criteria for LVH

Voltage Criteria (any of):

a.R or S in limb leads >20 mm

b.S in V1 or V2 > 30 mm

c.R in V5 or V6 >30 mm

3 points

ST-T Abnormalities:

Without digitalis

With digitalis

3 points

1 point

Delayed intrinsicoid deflection in V5 or V6

(>0.05 sec)

1 point

diagnostic >5 points; probable 4 points

RV Hypertrophy

• Right axis deviation (>90 degrees)

• Tall R-waves in RV leads; deep S-waves in LV leads

• Slight increase in QRS duration

Blood Supply

• LAD: anterior and anterolateral walls of the left ventricle and the anterior two-thirds of the septum

• LCX: posterolateral wall of the left ventricle

• RCA: right ventricle, the inferior and true

posterior walls of the left ventricle, and the

posterior third of the septum

• AV nodal coronary artery from RCA in

85-90% of individuals; in the remaining 10-15%, this artery is a branch of the LCX