Cardiac Rotation/ R Wave Progression

Objectives:

The Horizontal Plane/ Precordial Leads

The six precordial leads V1 to V6 are also called horizontal or transverse leads since they represent the horizontal or transverse plane of the chest. The horizontal plane includes the left/right as well as the anteroposterior sides of the chest
Leads V1 and V2: Leads V1 and V2 are right-sided precordial leads and are positioned directly over the right ventricle. The QRS complexes in V1 and V2 represent electrical forces generated from the right ventricle and generally show small r and deep S waves.
Leads V5 and V6: Leads V5 and V6 are left-sided precordial leads that directly overlie the left ventricle. The QRS complexes represent electrical forces generated from the left ventricle, which show small q waves followed by tall R waves.
Leads V3 and V4: The QRS complexes are equiphasic in leads V3 and V4 because these leads represent the septal area and is the transition zone between the deep S waves in V1 and V2 and the tall R waves in V5 andV6.

Cardiac Rotation: 2 Types

In the horizontal plane, a change in the electrical position of the heart is described as rotation. The heart may rotate clockwise or counterclock wise, resulting in a shift of the transition zone to the left or to the right of V3 or V4.
In cardiac rotation, it is important to recognize that the heart is being visualized from under the diaphragm looking up. This is opposite from the way the precordial electrodes are conventionally visualized, which is from the top looking down. Thus, in cardiac rotation, the anterior and posterior orientation of the body and the direction of cardiac rotation is reversed.
Rotation of the heart is determined by identifying the transition zone where the QRS complex is equiphasic.

Clockwise rotation or delayed transition: (A)

When the heart rotates clockwise, the transition zone, which is usually in V3 or V4, moves to the left toward V5 or V6. This is called clockwise rotation, delayed transition, or late transition.
When the apex of the heart is viewed from under the diaphragm, the front of the heart moves to the left, causing the right ventricle to move more anteriorly.

Counterclockwise rotation or early transition: (C)

When the heart rotates counterclockwise, the transition zone moves earlier, toward V1 or V2. This is called counterclockwise rotation or early transition.
When the apex of the heart is viewed from under the diaphragm, the front of the heart moves to the right causing the left ventricle to move more anteriorly.

Transition Zones:

(A, B) Normal transition where the R and S waves are equiphasic in V3 or V4.
(C, D) Early transition or counterclockwise rotation with the transition zone in V1 or V2.
(E, F) Late transition or clockwise rotation with the equiphasic QRS complex in V5 or V6. The transition zones are circled.

Tall R waves in V1 Examples:

Unusal in adults. When R wave is taller than the S wave in V1, the following should be excluded before this finding is considered a normal variant.

Differentiating different causes of Tall R waves in V1

RBBB: QRS complexes are wide measuring =>0.12 seconds. Terminal R waves are also present in V1 and wide S waves are present in V5 and V6 or lead I.

Pre-excitation or WPW ECG: Short P-R interval and presence of a delta wave. The R waves are tall in V1 when the bypass tract is leftsided.

Posterior MI: Straight posterior MI is usually seen in older patients, not in children or young adults. It is often associated with inferior MI with pathologic q waves in leads II, III, and aVF or history of previous MI.

Pacemaker rhythm: A pacemaker artifact always precedes the QRS complex. Generally, a pacemaker- induced QRS complex has a QS or rS configuration in V1 because the right ventricle is usually the chamber paced. However, when the R wave is tall in V1 and is more prominent than the S wave (R or Rs complex), left ventricular or biventricular pacing should be considered.

Ventricular ectopic impulses: Ventricular ectopic impulses may show tall R waves in V1. This can occur when the ectopic impulses originate from the left ventricle.

Normal variant: Before considering tall R waves in V1 and V2 as normal variant, other causes should be excluded.

Clockwise Rotation Examples:

Left ventricular hypertrophy: This can be due to several causes, including dilated cardiomyopathy or left-sided valvular insufficiency.
Right ventricular hypertrophy: Depending on the cause of the right ventricular hypertrophy, clockwise rotation may be present instead of a tall R in V1. This often occurs when there is mitral stenosis, pulmonary hypertension and chronic obstructive pulmonary disease
Biventricular hypertrophy: Both ventricles are enlarged.
Chronic obstructive pulmonary disease: In chronic obstructive pulmonary disease such as emphysema or chronic bronchitis, the diaphragm is displaced downward, causing the heart to rotate clockwise and become vertically oriented. (Figure below)
Acute pulmonary embolism
LAFB

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Learning EKG ~ Simrat Batth