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

Page created on October 24, 2018. Last updated on October 20, 2020 at 17:31

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.

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.

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, III 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

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