Chronic Cor Pulmonale: Key ECG Findings and Diagnostic Insights

Chronic cor pulmonale, a condition characterized by right ventricular enlargement due to long-standing lung disease, presents distinct electrocardiogram (ECG) patterns that are crucial for early detection and management. Recognizing these electrical changes helps clinicians assess cardiac strain related to chronic respiratory disorders such as COPD, pulmonary fibrosis, or severe emphysema.

Common ECG Criteria for Chronic Cor Pulmonale

Several ECG findings are strongly associated with chronic cor pulmonale. While any single criterion may suggest the condition, a combination of features increases diagnostic confidence. It's important to note that ECG has a sensitivity of approximately 75% for detecting this disorder—meaning it's a helpful tool but not definitive on its own.

1. Right Axis Deviation (RAD)

One of the hallmark signs is an extreme rightward shift in the frontal plane axis. When the mean QRS axis is ≥ +90 degrees, it indicates significant right ventricular dominance. This deviation occurs because prolonged pulmonary hypertension causes the right ventricle to enlarge and take over the electrical forces of the heart.

2. R/S Ratio ≥ 1 in Lead V1

In lead V1, a tall R wave relative to the S wave (R/S ratio ≥ 1) reflects increased right ventricular muscle mass. Normally, V1 shows a small R and deep S; when this pattern reverses, it suggests right ventricular hypertrophy (RVH), a core component of cor pulmonale.

3. Severe Clockwise Rotation with R/S ≤ 1 in V5

Severe clockwise rotation of the heart around its long axis shifts typical right-sided ECG patterns toward the left precordial leads. As a result, lead V5—which normally shows a dominant R wave—displays an R/S ratio ≤ 1, resembling what's usually seen in more rightward leads like V1 or V2.

4. Increased R Wave in V1 + S Wave in V5 (Rv1 + Sv5 ≥ 1.05 mV)

This voltage criterion combines the amplitude of the R wave in V1 and the S wave in V5. A sum equal to or exceeding 1.05 mV supports the diagnosis of RVH. Although less sensitive than other imaging methods, this finding remains a practical indicator in routine ECG interpretation.

5. R/S or R/Q ≥ 1 in Lead aVR

Lead aVR often mirrors activity in the right side of the heart. An elevated R wave compared to the S or Q wave (R/S or R/Q ≥ 1) further supports right-sided electrical dominance and correlates with structural changes seen in chronic lung disease.

6. QS, Qr, or qr Patterns in Leads V1–V3

The presence of QS (no R wave), Qr, or qr complexes in the right precordial leads (V1–V3) can mimic anterior infarction but in the context of lung disease, they often represent loss of left ventricular forces and enhanced right ventricular signals due to anatomical repositioning or remodeling.

7. Presence of P Pulmonale

A prominent P wave in leads II, III, and aVF—tall, peaked, and often referred to as "P pulmonale"—indicates right atrial enlargement. This occurs due to increased pressure in the pulmonary circulation forcing the right atrium to work harder, leading to electrical changes visible on ECG.

Limitations and Clinical Interpretation

While meeting just one of these criteria may raise suspicion for chronic cor pulmonale, relying solely on ECG can be misleading. The overall diagnostic accuracy hovers around 75%, meaning false negatives and positives do occur. Therefore, ECG should be interpreted alongside clinical history, physical examination, chest imaging, echocardiography, and pulmonary function tests.

For patients with known chronic obstructive pulmonary disease (COPD) or interstitial lung disease, serial ECG monitoring can help track progression toward cor pulmonale. Early identification allows for timely intervention, including oxygen therapy, bronchodilator optimization, and management of exacerbating factors.

In summary, recognizing the characteristic ECG patterns of chronic cor pulmonale enhances diagnostic precision and supports comprehensive patient care. However, always consult a qualified healthcare provider for accurate assessment and treatment planning based on a full clinical picture.