Sinus tachycardia is recognized on an ECG with a normal upright P wave ... has been described and is a form of autonomic dysfunction. Sinus node modification or ablation procedures can be done ...

Sinus arrhythmia refers to a changing sinus node rate with the respiratory cycle ... and decreases with expiration. The ECG criteria to diagnose sinus arrhythmia is a variation of the P-P interval ...

Sinus node dysfunction associated with symptoms is a ... this diagnosis is usually apparent by characteristic ECG patterns. However, ECG patterns are not diagnostic for trifascicular block.

In fact, up to 60% of athletes demonstrate ECG changes (in isolation or in combination) such as sinus bradycardia, sinus arrhythmia, first-degree atrioventricular (AV) block, early repolarisation, ...