Abnormal structural, functional, and electrophysiological properties in the atrial myocardium contribute to the development of atrial fibrillation (AF) and its complications. Several risk factors—such as older age and chronic cardiovascular diseases—have been identified for this pathological progression, yet limited methods exist to monitor the manifestation and evolution of the underlying atrial cardiomyopathy in clinical practice. The electrocardiogram (ECG) offers a non-invasive tool that may reflect these atrial properties through changes in the P-wave, which have been associated with AF incidence, rhythm control failure, and adverse cardiovascular outcomes.

This thesis aimed to identify P-wave parameters that predict ineffective cardioversion (CV) of AF, to improve patient selection thus minimizing procedural risks (I). It further evaluated whether P-wave features are associated with the risk of short- and long-term stroke or systemic embolism (SSE), particularly among patients classified as low risk by conventional methods (II). Finally, it assessed the temporal stability and progression of P-wave parameters to determine their reliability for risk stratification (III).

Patients with prolonged P-wave and a biphasic waveform had over fourfold higher odds of CV failure and threefold higher odds of early AF recurrence compared to those with normal P-waves (I). Similarly, the combination of various extensive abnormalities was associated with over a fivefold increase in odds for SSE within 30 days after CV and a fourfold increase in long-term SSE risk. Moreover, the presence of this composite variable doubled the risk of mortality and tripled the odds of heart failure during follow-up (II). Over a series of ECGs, nearly 75% of all P-wave abnormalities remained stable or progressed to a more severe form, with progression most evident among patients with the longest follow-up.

In conclusion, assessing the ECG of AF patients may aid in clinical decision-making by identifying those unlikely to benefit from CV and those at increased risk for AF-related complications. P-wave parameters appear stable or progressive over time, suggesting that even ECGs recorded prior to the onset of AF may be valuable in patient management.