A Visual Guide to ECG Interpretation


Chapter 9 • Voltage Abnormalities

Right Ventricular Hypertrophy Due to the opposing forces of the thicker left ventricle, the sensitivity of electrocardiographic criteria for right ventricular hypertrophy (RVH) is generally low. The mass of the left ventricle is still greater than that of the right ventricle in patients with RVH. The presence of several ECG features, however, can be helpful in cases of significant RVH.

ECG Features

Right Axis Deviation QRSVoltage Criteria

This is a consistent sign in RVH. The most common cause of right axis deviation in an adult is RVH (Fig. 9.2).


ECG Features

Right-Sided Leads (V1) R>7mm R:S > 1

Left-Sided Leads (V5 or V6)


R:S ratio ≥ 1

Lung Hyperinflation


S > 7 mm

Air can dampen the ECG signal.

Low Voltage

FIGURE 9.2 ECG appearance of RVH in precordial leads.

Lowered diaphragms cause the heart to be positioned more vertically.

Vertical Heart Position

S1 S2 S3 Pattern Peaked P Waves: Amplitude ≥ 2.5mm in lead II S waves in leads I, II, and III ST/TWave Changes ST Depression and TWI in V1 to V2 are secondary repolarization abnormalities that may accompany tall R waves P Pulmonale

Results from clockwise rotation of the vertical heart. The P-, QRS-, and T-wave vectors are all almost perpendicular to lead I. These waves in lead I have low amplitudes. Due to right ventricular hypertrophy or dilation

Right Axis Deviation

Poor R-Wave Progression

The Lead I Sign (Figure 9.3)

Causes to Consider

Right Atrial Abnormality

Peaked P waves in leads II, III, and aVF often accompany the above ECG changes.

Pressure Overload

Volume Overload

Deep S waves in V5 and V6.


Primary Pulmonary Hypertension COPD Mitral Stenosis Pulmonary Embolism Pulmonic Stenosis Ventricular Septal Defect

Tricuspid Regurgitation Atrial Septal Defect

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FIGURE 9.3 Example of the lead I sign in a patient with severe COPD. P and T waves are unidentifiable. QRS complexes are 1 mm in amplitude.

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