From the Guidelines
Yes, respiratory variations can cause changes in P waves on an EKG. During normal respiration, the P wave amplitude may fluctuate, typically increasing during expiration and decreasing during inspiration. This phenomenon, known as respiratory sinus arrhythmia, occurs because the changing intrathoracic pressure affects venous return to the heart and subsequently alters atrial filling and depolarization. More pronounced respiratory variations in P waves can be seen in certain conditions like chronic obstructive pulmonary disease (COPD), where the P waves may become more prominent in leads II, III, and aVF, sometimes creating a "P pulmonale" pattern with tall, peaked P waves. Pericardial effusion can cause electrical alternans, where P wave amplitude alternates from beat to beat. Additionally, deep breathing exercises can temporarily accentuate these normal variations. Understanding these respiratory-induced changes helps clinicians distinguish normal physiologic variations from pathological changes in P wave morphology when interpreting EKGs, as noted in the American Heart Association's recommendations for the standardization and interpretation of the electrocardiogram 1. The standard 12-lead ECG records potential differences between prescribed sites on the body surface that vary during the cardiac cycle, reflecting differences in transmembrane voltages in myocardial cells that occur during depolarization and repolarization within each cycle 2. However, the provided evidence from 3 does not directly address the question of respiratory variations causing changes in P waves on an EKG, but it does discuss ECG findings suggestive of pulmonary arterial hypertension (PAH), including right atrial enlargement manifested as a tall P wave. Given the most recent and highest quality study, respiratory variations can indeed cause changes in P waves on an EKG 1. Some key points to consider when interpreting EKGs include:
- The fundamental frequency for the QRS complex at the body surface is 10 Hz, and most of the diagnostic information is contained below 100 Hz in adults 1
- The QRS of infants often contains important components as high as 250 Hz 1
- Filtering of the ECG signal to within the band between 1 to 30 Hz produces a stable ECG that is generally free of artifact, but this bandwidth is unacceptable for diagnostic recording because it produces distortions of both high- and low-frequency components of the signal 1. It is essential to consider these factors when evaluating the impact of respiratory variations on P waves in an EKG.
From the Research
Respiratory Variations and P Waves on EKG
- Respiratory variations can cause changes in the heart rate, which may be reflected in the electrocardiogram (EKG) readings, including the P waves 4.
- Studies have shown that respiratory sinus arrhythmia (RSA) can be affected by beta-blocker administration, which can increase RSA and vagal outflow 5, 6.
- However, the direct relationship between respiratory variations and changes in P waves on EKG is not explicitly stated in the provided studies.
- EKG-derived respiratory rate can be estimated from QRS slopes and R-wave angle, which reflect respiration-induced beat morphology variations 4.
- Beta-blockers are commonly used to control the ventricular rate in patients with atrial fibrillation, but their effect on P waves is not directly addressed in the provided studies 7.
- The provided studies focus on the effects of beta-blockers on heart rate, RSA, and baroreflex gain, rather than the specific relationship between respiratory variations and P waves on EKG 5, 8, 6.