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Ростовский Государственный Медицинский Университет

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Fig. 8.9 Mean QRS axis is −41°. There is left axis deviation

Fig. 8.10 Mean QRS axis is directed towards the negative pole of axis of lead III

8 Left Axis Deviation

Chapter 9

aVF

Right axis deviation

Left axis deviation

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Right Axis Deviation

Learning Objectives

After studying this chapter, the reader will learn about:

• Right axis deviation

• Calculation of right axis deviation

• Causes of right axis deviation

In right axis deviation (RAD), the axis is between +90° and +180° (Fig.9.1). The QRS vector would be directed downward and to the right. Right axis deviation occurs in various conditions including right bundle branch block, left posterior hemiblock, right ventricular hypertrophy, etc.

To calculate axis, let us consider the QRS tracing in lead I and lead aVF of

Fig.9.2. There is a positive deection in lead aVF and a negative deection in lead

Fig. 9.1 Orientation of the cardiac axis. The area shaded light blue is right axis deviation, and the area shaded yellow is left axis deviation

Ltd. 2024 T. K. Koley, Rapid Review of ECG,

https://doi.org/10.1007/978-981-99-9116-7_9

aVR

( )180

(-)150

(+)150

(+)

III

(-)120

120

(-)

(+)

90

(-)

(+) 60



aVL

(-)30

I(+)

0

(+) 30

109© The Author(s), under exclusive license to Springer Nature Singapore Pte

110

aVF

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9 Right Axis Deviation

III III

Fig. 9.2 ECG tracing of standard leads

Fig. 9.3 Plotting of −˗5

on axis of lead I

aVR

aVL

–

aVF

I.If we use the rst method to calculate the QRS axis, we can say that there is a right axis deviation but a more accurate axis can be determined by this method. Let us calculate the axis by the second method and follow the steps as mentioned below.

Step I

At rst, plot the lead axis of lead I and lead aVF.

Step II

Next calculate the total positive and total negative deection of the QRS complex in lead I.For example, it is +4 (r wave) and −9 (S wave) in the given ECG.So, the net resultant is −5 (+4+[−9]=−5).

Now, plot −5in the lead axis of lead I (Fig.9.3).

9 Right Axis Deviation

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111

Step III

Now draw a perpendicular through the plotted point on lead I (Fig.9.4).

Step IV

Similarly, calculate the net resultant in lead aVF.In the given ECG, the net resultant is +6 (+6+0)=+6). Now, plot +6in the lead axis of lead aVF (Fig.9.5).

Fig. 9.4 Perpendicular drawn on lead I axis through −5

–

Fig. 9.5 Plotting of +6 on axis of lead aVF

–

aVF

–

aVF

112

aVF

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9 Right Axis Deviation

Step V

Next draw a perpendicular through the plotted point on lead aVF axis and prolong it to meet the perpendicular drawn on lead I axis (Fig.9.6).

Step VI

In the last step, draw a line joining the point of the intersection of axis of lead I and aVF and the point of intersection of the two perpendicular lines. The QRS axis is +130° (Figs.9.7 and 9.8).

The various causes of right axis deviation are enumerated in Box 9.1.

Fig. 9.6 Perpendicular drawn on axis of lead aVF through +6

–

Fig. 9.7 QRS axis is +130°. There is right axis deviation

–

+130°

aVF

9 Right Axis Deviation

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Fig. 9.8 Right axis deviation (QRS axis+130°). The axis is directed to the positive pole of lead III

113

Box 9.1 Causes of Right Axis Deviation

Right ventricular hypertrophy COPD RBBB Left posterior hemiblock Limb lead reversal Lateral wall myocardial infarction Ostium secundum ASD Pulmonary embolism Dextrocardia Anterolateral myocardial infarction WPW syndrome Normal variant Left pneumothorax

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9 Right Axis Deviation

Tips and Tricks

• In right axis deviation, QRS axis lies between +90° and +180°.

• Check the dominant waves in lead I and lead aVF.

• If lead I has dominant S wave and lead aVF has dominant R wave, it is right axis deviation.

• Any doubt, use method 2.

Self-Assessment Questions

1. Which of the following is the range for the QRS axis in RAD?

a. −30° to +90° b. +90° to +180° c. 0° to +180° d. −180° to 0°

2. Which of the following is associated with RAD on an ECG?

a. LVH b. Sinus arrhythmia c. Atrial brillation d. RVH

3. Which of the following conditions is not typically associated with RAD

on an ECG?

a. Acute myocardial infarction b. Chronic obstructive pulmonary disease c. Pulmonary embolism d. Pulmonary hypertension

4. Which of the following statements about RAD is true?

a. It always indicates some cardiac disease b. It is always a normal nding c. It can be either a pathologic or a normal nding, depending on the underlying cause d. It is always seen in athletes

5. Positive deection is seen in lead aVF and negative deection is seen in lead

I.The QRS axis is:

a. LAD b. RAD c. Normal QRS axis d. Northwest axis

Case Study

1. Calculate the mean QRS axis from the six limb leads shown below (Fig.9.9). If you can detect any axis deviation, name one condition where you will get such axis deviation.

III III

Fig. 9.9 Calculate the mean QRS axis

aVFaVLaVR

9 Right Axis Deviation

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Answers

1. b 2. d 3. a 4. c 5. b

Case Study

1. For calculating the mean QRS axis, method 1 and 2 will be used.

Method 1: There is negative deection in lead I and positive deection in

lead aVF.Hence, there is right axis deviation.

Method 2: The algebraic sum of the deections in lead I is −4 (+2+[−6]=−4). Similarly, the resultant of the deections in lead aVF is +14 (+14+0=+14). Hence, by plotting the resultant on the ECG grid, the mean QRS axis calculated is +105° (Fig.9.10). Thus, the ECG shows right axis deviation.

Because of right axis deviation, there is tall R wave in lead III and lead aVF (mean depolarization wavefront moving towards the positive pole of lead III and lead aVF) (Fig.9.11), and the height of R wave is more in lead III as compared to the height of R wave in lead II (mean depolarization wavefront is moving more towards the positive pole of lead III as compared to the positive pole of lead II). Right axis deviation is seen in right ventricular hypertrophy, about which you will read in subsequent chapters.

Fig. 9.10 Mean calculated QRS axis is +105°. There is right axis deviation

–

115

Fig. 9.11 The axis is directed between the positive poles of lead III and lead aVF

–

+105°

aVF

Chapter 10

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Normal ECG andIts Variants

Learning Objectives

After studying this chapter, the reader will learn about:

• Normal ECG

• Early repolarization syndrome

• Persistent juvenile pattern

• Nonspecic T wave changes

• Method of interpretation of ECG

10.1 Normal ECG

For a beginner, one of the most complex part of learning ECG is to remember the normal morphology of P, QRS and T waves in all the 12 leads. If one can condently interpret a normal ECG, he may consider himself to have crossed one of the major hurdles in the process of learning of ECG.However, one must remember, it comes only by constant practice. Before proceeding further, let us recapitulate what we have learnt about normal ECG.

• In frontal plane leads, the P wave is positive in lead II and negative in lead aVR.This simple observation tells us that impulse has originated from SA node.

• In rest of the limb leads, the P wave is generally positive.

• The QRS complex and T wave morphology are also similar to the P wave morphology in limb leads. However, there are lots of normal variants, which are discussed later in this chapter.

• In lead aVR, all the waves are negative.

• The T wave generally follows the main deection of the QRS complex in any lead.

Ltd. 2024 T. K. Koley, Rapid Review of ECG,

https://doi.org/10.1007/978-981-99-9116-7_10

118

V1 V2

V5 V6

10 mm = 1 mV

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10 Normal ECG andIts Variants

• In chest leads, P wave may be positive, negative or biphasic in lead V1. In rest of the leads, the P wave is positive.

• In lead V1, rS complex is recorded, and in lead V6, qRs complex is recorded. There is progression of R wave amplitude, and the transition zone is recorded in lead V3 or lead V4.

• In electrically vertical heart, QRS complex in lead aVF and lead V6 is similar.

• In electrically horizontal heart, QRS complex in lead aVL and lead V6 is similar.

• S-T segment is isoelectric.

• The normal P-R interval is 0.12–0.20s.

• The normal QRS interval is less than 0.12s.

• The normal range of Q-Tc is 0.35–0.44s (men) or 0.45s (women).

• Heart rate=1500/R-R interval. Normal heart rate is between 60 and 100bpm.

A normal ECG is shown in Fig.10.1. The P, QRS and T waves in all the 12 leads are normal. All the waves are inverted in lead aVR.Transition zone is recorded in lead V3. QRS axis is normal. The different time intervals are also within normal limit. In infants, the ECG will simulate that of right ventricular hypertrophy in adults. Tall R waves are present in right precordial leads. There is right axis deviation. There is no initial q wave in lead V1, and the VAT is not prolonged. The T waves are normally inverted in leads V1–V4. The tall R waves in right precordial leads usually disappear after the age of 5years. But the inverted T waves may persist even up to the second decade. The QRS axis gradually shifts to left.

I III

. 25 mm/s.

Fig. 10.1 Normal ECG.P wave is rounded and upright in lead II.Lead aVR reects completely negative complex. P-R interval and QRS duration are normal. rS complex is recorded in lead V1 and qR complex is recorded in lead V6. Transition zone is recorded in lead V3. QRS axis is normal

aVR

aVL aVF

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