Understanding the ECG Changes in Pericarditis: A Comprehensive Guide

The changes in ECG patterns observed during pericarditis are quite fascinating and can provide significant diagnostic information. Pericarditis, an inflammation of the pericardium, can manifest with various ECG alterations. This article delves into the specific ECG changes and their underlying mechanisms, providing a detailed explanation to help medical professionals and students understand these complex cardiovascular dynamics.

What is Pericarditis?

Pericarditis is an inflammation of the pericardium, the sac-like structure that envelops the heart. This inflammation can involve both the parietal and visceral layers of the pericardium. The visceral pericardium, being closely associated with the myocardium, can cause injuries that affect the surface of the myocardium, leading to changes in the heart's electrical activity as observed on an ECG.

Understanding the Mechanism of ECG Changes in Pericarditis

The primary ECG changes seen in pericarditis are concave ST-elevation and PR-depression. These changes are the result of electrical conduction anomalies in the myocardium due to the inflammation. Let's break down the key aspects:

Concave ST-Elevation

ST-elevation in pericarditis is not a new or active process of ventricular repolarization but rather a manifestation of the current flow due to the compromised cellular integrity of the myocardium. During phase 3 of the myocardial action potential, when the myocardium is relaxed, a flow of positive charge from the outside to the inside of the heart can be observed. This flow is recorded as a concave ST-elevation on the ECG, particularly in leads I, II, III, aVL, aVF, and V2–6. It’s important to note that this elevation is not true ST-elevation but a reflection of the current flow and should not be confused with ischemic changes.

PR-Depression

The PR segment represents the time it takes for electrical activity to travel from the atria to the ventricles. In pericarditis, the myocardium loses some of its negative electrical potential due to the injury. When the myocardium is at rest, the current flow away from the precordial leads leads to a decrease in the QRS complex amplitude and a depression of the PR segment. This depression is seen in leads I, II, III, aVL, aVF, and V2–6.

Reciprocal ST-Depression and PR-Elevation

In addition to the characteristic anterior ST-elevation and PR-depression, pericarditis can also present with reciprocal changes. A typical reciprocal change is the presence of ST-depression in lead aVR, reflecting the opposite changes in the other leads. Sometimes, there can also be minor PR-elevation in leads V1 and aVR, further emphasizing the reciprocal nature of the changes.

Other ECG Changes in Pericarditis

ECG changes in pericarditis are not limited to ST-elevation and PR-depression. Other common findings include sinus tachycardia, which can be attributed to pain and/or pericardial effusion. This arrhythmia is a physiological response to the discomfort and increased sympathetic activity triggered by inflammation. Other less specific changes may also be observed, including nonspecific T-wave changes and presence of Q-waves in some cases.

Conclusion

The changes in ECG seen during pericarditis, particularly concave ST-elevation and PR-depression, are indicative of the complex electrical dynamics of the myocardium. Understanding these changes requires a thorough knowledge of cardiac physiology and the intricate mechanisms involved. Accurate diagnosis through ECG interpretation can be a crucial step in managing pericarditis effectively.

We welcome input from physiology experts and anyone with further insights into the mechanisms of ECG changes in pericarditis to enhance our understanding.