Fragmented QRS: Electrophysiological Bases, Pathophysiological Mechanisms, and Clinical Prognostic Significance

Background: Fragmented QRS (fQRS) is characterized by morphological irregularities in ventricular depolarization on a standard 12-lead surface electrocardiogram (ECG) and is considered a non-invasive indicator of myocardial conduction heterogeneity. Microstructural changes such as non-uniform anisotropy, gap junction reorganization, and interstitial fibrosis can disrupt the propagation of the electrical impulse, leading to notching in the QRS complex.Methods: This study is designed as a narrative review to evaluate the electrophysiological basis and clinical implications of fQRS. A literature search was conducted in the PubMed, Scopus, and Web of Science databases to include peer-reviewed articles published between 2006 and 2025 that addressed fQRS, myocardial scarring, and ventricular arrhythmias (VA).Results: Current data indicate that the presence of a fQRS shows a strong correlation with myocardial scarring, particularly in ischemic cardiomyopathies, and may serve as an independent risk marker for VA and cardiac mortality. Additionally, it has been reported that in heart failure (HF) and certain channelopathies, fQRS carries prognostic value as a superficial reflection of electrical remodeling. However, the fact that evaluation methods are largely visual and qualitative, along with interobserver variability and dependence on ECG filter settings, limits the clinical utility of this finding.Conclusion: Fragmented QRS has the potential to provide important prognostic information as an electrocardiographic indicator of myocardial fibrosis and conduction heterogeneity. However, standardized definition criteria, quantitative analysis methods, and large-scale prospective studies are required for its integration into routine clinical practice.