Atrial Hypertrophy
A normal P wave reflects the sequential activation of the right and then the left atrium, fitting within 0.12 seconds in duration and up to 3 mm in amplitude.
In pathology of the right heart chambers (often against the background of chronic lung diseases), the P-pulmonale phenomenon develops. The electrical activity of the right atrium increases, and a tall (more than 2.5–3 mm) pointed P wave appears on the ECG in leads II, III, aVF, and $V_1$. In lead $V_2$, its first phase also becomes positive and peaked.
Left atrial overload is characteristic of mitral valve disease—this is the P-mitrale phenomenon. Activation of the left chamber is prolonged, causing the P wave to widen and notch, acquiring a double-peaked shape in leads I and II. In lead $V_1$, it becomes biphasic with a predominance of a deep negative left-atrial wave.
Left Ventricular Hypertrophy (LVH)
Changes in the electrical axis of the heart (EAH) are often expressed as left axis deviation, unless the patient has a left bundle branch block. Hypertrophy is judged primarily by voltage criteria:
- Sokolow-Lyon index: the sum of the $S$ amplitude in $V_1$ and the $R$ amplitude in $V_5$ or $V_6$ exceeds 35 mm.
- Cornell index: the amplitude of $R$ in $aVL$ + $S$ in $V_3$ is more than 28 mm in men and more than 20 mm in women.
- Isolated criteria: $R > 11$ mm in $aVL$; $R > 20$ mm in I, II, III, or $aVF$. In chest leads, $S > 25$ mm in $V_1$ or $R > 25$ mm in $V_5-V_6$.
The maximum amplitude of the $R$ wave shifts from $V_4$ to the left chest leads. In these same leads ($V_5-V_6$), as well as in I and $aVL$, secondary repolarization abnormalities are noted: arcuate ST-segment depression (concave upwards) and the appearance of a negative asymmetric T wave with a gentle descending and steep ascending limb.
Right Ventricular Hypertrophy (RVH)
Detecting RVH is difficult: normally, the mass of the left ventricle exceeds the mass of the right by approximately 6 times, so the electrical potential of the left chamber dominates and "masks" the changes. Diagnosis is possible only with significant RV overload.
In pronounced RVH, right axis deviation is observed (tall $R$ in lead III and deep $S$ in lead I). In the right chest leads ($V_1-V_2$), instead of the dominance of the $S$ wave, a tall $R$ wave forms, and their ratio ($R/S$) becomes greater than 1.0. Conversely, in the left chest leads ($V_5-V_6$), a deep $S$ wave forms, and the $R/S$ ratio drops below 1.0 (assuming there is no anterior wall myocardial infarction or left bundle branch block). Secondary ST and T changes (depression and inversion) are localized in $V_1-V_2$, III, and aVF.
Morphological Types of RVH
There are three specific QRS complex patterns indicating right-sided pathology:
- qR type: a pathological $q$ wave appears in lead $V_1$ combined with a tall $R$. Accompanied by a deep $S$ in the left chest leads and a rightogram.
- rSR' (rSr') type: in $V_1$, the QRS complex resembles the letter "M", where the amplitude of the second $R'$ wave is higher than the first $r$. Right axis deviation is not typical for this type, but a deep $S$ persists in I, aVL, and $V_5-V_6$.
- S type: a prominent deep $S$ wave is present in all chest leads (from $V_1$ to $V_6$). Right axis deviation is also usually absent.
Briefly: answers to topical questions
Which diseases and defects most frequently lead to the formation of P-pulmonale on the ECG?
Pulmonary diseases frequently lead to the formation of the P-pulmonale phenomenon on the electrocardiogram.
The clinical context for the development of this ECG pattern includes:
- Chronic lung diseases — characterized by the P-pulmonale phenomenon.
- Cor pulmonale — the term P-pulmonale indicates the frequent association of this pathology with pulmonary diseases.
There is no data in the sources regarding heart defects leading to the P-pulmonale phenomenon. Mitral valve diseases in the source are associated with a different phenomenon — P-mitrale.
In P-pulmonale, a tall, peaked, pointed P wave with an amplitude greater than 2.5 mm is registered on the ECG in leads II, III, aVF, V₁.
P-pulmonale (lungs) — the wave resembles a sharp peak. P-mitrale (mitral valve) — the wave is widened and resembles the letter "M" (notched).
Class and exam questions
How accurately does an ECG detect ventricular hypertrophy?
The method has high specificity (if signs are present, hypertrophy is almost certainly present) but low sensitivity. The absence of signs on the ECG does not rule out the presence of actual hypertrophy.
In which leads is atrial hypertrophy best visualized?
Right atrial changes (P-pulmonale) are best assessed in leads II, III, aVF, and V1. Left atrial changes (P-mitrale) are most pronounced in I, II, and V1.
Why does a deep S wave appear in the left chest leads in RVH?
The deep S wave in leads V5 and V6 is a reciprocal reflection of the hypertrophied right ventricle vector, which is abnormally directed to the right and anteriorly.
What else to study on this topic
- Features of the ECG pattern in myocardial infarction and CHD
- Nonspecific ST-T changes in metabolic and electrolyte disorders
- Left anterior fascicular block: effect on the electrical axis of the heart
- Effect of anterior wall scar changes on ventricular voltage criteria
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