37. Signs of chronic or acute overload in the ECG (hypertrophy, strain)

Last updated on May 24, 2019 at 11:11

Right atrial enlargement

The right atrium is rarely hypertrophic. Pressure or volume load almost always causes dilatation and not hypertrophy.

Etiology:

  • Pressure load on the atria
    • Stenosis of the tricuspid or pulmonary valve
    • COPD
    • Chronic respiratory failure
    • Right ventricular hypertrophy
  • Volume load on the atria
    • Insufficiency of the tricuspid or pulmonary valve
    • Left-to-right shunts
    • Left-sided heart failure

ECG morphology:

The morphology of the P wave during right atrial enlargement is called “pulmonary P“. The pulmonary P is mostly seen in inferior leads (II, III, aVF). It involves the following:

  • Peaked, tall P wave
  • In lead V1, the P-wave may be biphasic, where the first, positive part is bigger

The depolarization of the right atrium is responsible for the 1st part of the P wave.

Pulmonary P
Biphasic P. The first, positive part of the P-wave is bigger.
Left atrial enlargement

Etiology:

  • Mitral or aortic valve insufficiency
  • Mitral or aortic valve stenosis
  • Systemic hypertension
  • Right-to-left shunt
  • Cardiomyopathy

ECG morphology:

Two special P-wave morphologies are seen in left atrial enlargement:

  • Mitral P
    • Broad, split P wave in leads I, II, V5, V6
  • P terminal force
    • Biphasic P-wave in lead V1 where the second, negative part is bigger

The depolarization of the left atrium is responsible for the 2nd part of the P wave.

Mitral P

Biphasic P. The second, negative part of the P-wave is bigger

Biatrial enlargement

A combination of the causing factor of both right and left atria can lead to biatrial enlargement.

ECG morphology:

  1. A biatriale P-wave can be observed in II, II and aVF.
    • It will be broad and high, more than 0,25 mV tall and more than 0,10 s broad!
  2. Biphasic P wave in V1 and V2.
    • Both components of this biphasic P-wave exceed 0,1 mV
    • Terminal negative component is longer than 0,04 s
Ventricular hypertrophy

Ventricular hypertrophy occurs due to long-term pressure or volume load on the ventricle.

The enlarged myocardium shifts the electrical axis toward the hypetrophic muscle. Depolarization of a big muscle takes longer, so the ventricular activation time (VAT) is prolonged. QRS will therefore be slightly widened (100 – 120 ms). Note that secondary repolarization abnormalities (ST-segment and T-wave) may be present as the ischemia often develops in a hypertrophied heart.

Right ventricular hypertrophy

Etiology:

  • Pulmonary hypertension

ECG morphology:

The chest leads V1 and V2 correspond to the right ventricle, so most of these signs are seen there.

  • Enlarged R-wave (> 0.7 mV) – in V1 and V2
  • VAT > 40 ms – in V1 and V2
  • ST-depression and T-wave inversion in V1 and V2
  • Dominant and deep S-wave – in V5 and V6 (left ventricular leads)
    Right axis deviation
Large R-wave
Deep, dominant S-wave

Acute load on the right ventricle

Etiology:

  • Pulmonary embolism
  • Pneumothorax

ECG morphology:

  • Sinus tachycardia
  • Large R wave – in V1
  • Large S wave – in lead I
  • Large Q – in lead III
  • Negative T – in lead III
Left ventricular hypertrophy

Etiology:

  • Systemic hypertension
  • Aortic stenosis
  • Right-to-left shunt
  • Cardiomyopathy

ECG morphology:

  • Left axis deviation
  • High voltage
    • Positive Sokolow index: Sum of the amplitude of S wave in V1 and the amplitude of the R wave in V5 > 35 mm
    • Positive Lewis index: Sum of the amplitude of S wave in III and the amplitude of the R wave in I > 25 mm
  • Strain signs – in left ventricular leads (I, aVL, V4, V5, V6)
    • Descending ST depression
    • Negative T waves
  • VAT > 40 ms – in leads V5, V6
Large R-wave, ST depression, T-wave inversion
Deep S-wave and ST elevation
Sokolow-index
Lewis-index

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36. Forms and consequences of paroxysmal tachycardia

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38. Primary and secondary repolarization abnormalities in the ECG

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