QRS Fragmentation Patterns Representing Myocardial Scar Need to Be Separated from Benign Normal Variants: Hypotheses and Proposal for Morphology based Classification

Abstract

The presence of a fragmented QRS complex (fQRS) in two contiguous leads of a standard 12-lead electrocardiogram (ECG) has been shown to be an indicator of myocardial scar in multiple different populations of cardiac patients. QRS fragmentation is also a predictor of adverse prognosis in acute myocardial infarction, coronary artery disease, and ischemic cardiomyopathy and a prognostic tool in structural heart diseases. An increased risk of sudden cardiac death associated with fQRS has been documented in patients with ischemic cardiomyopathy and hypertrophic cardiomyopathy. However, fQRS is also frequently observed in apparently healthy subjects. Thus, a more detailed classification of different QRS fragmentations is needed to identify the pathological fragmentation patterns and refine the role of fQRS as a risk marker of adverse cardiac events and sudden cardiac death. In most studies fQRS has been defined by the presence of an additional R wave (R′), or notching in the nadir of the S wave, or the presence of >1 R′ in two contiguous leads corresponding to a major coronary territory. However, this approach does not discriminate between minor and major fragmentations and the location of the fQRS is also neglected. In addition to this, the method is susceptible to large interobserver variability. We suppose that some fQRS subtypes result from conduction delays in the His-Purkinje system, which is a benign finding and thus can weaken the prognostic values of fQRS. The classification of fQRSs to subtypes with unambiguous definitions is needed to overcome the interobserver variability related issues and to separate fQRSs caused by myocardial scarring from benign normal variants. In this paper, we review the anatomic correlates of fQRS and the current knowledge of prognostic significance of fQRS. We also propose a detailed fQRS classification for research purposes which can later be simplified after the truly pathological morphologies have been identified. The research material of our study consist of 15,245 ECGs from the random general population and approximately six thousands (n = 6,241) ECGs from subjects with a known cardiac disease.

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“…QRS fragmentation is a known indicator of a myocardial scar and has been shown to be a predictor of adverse prognosis in different populations of cardiac patients, including patients with acute myocardial infarction, coronary artery disease, ischemic cardiomyopathy, and structural heart diseases. In addition, location of fQRS in ECG correlates with the location of the myocardial scar . For example, fQRS ECG findings are more sensitive and specific than Q waves to detect a previous MI when compared to the nuclear stress test and, fQRS predicted acute MI with high sensitivity in 896 patients with acute coronary syndrome diagnosed by coronary angiography.…”

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“…A new and more precise classification of the various patterns of fQRS aiming at the differentiation between myocardial scar and benign normal variants is currently under investigation [10] (Figure 2). Some have advocated the use of a more quantitative approach of fQRS, for instance the derivative of dV/dT [5].…”

“…Different morphologies of fQRS on 12-lead ECG as described by Das et al [3]. Reprinted from the article « QRS fragmentation patterns representing myocardial scar need to be separated from benign normal variants: hypotheses and proposal for morphology based classification » » by Haukilahti A. et al [10], with permission. Figure 2.…”

“…A multivariate analysis revealed that fQRS was an independent predictor for cardiac events (HR ¼ 1.62) [9]. Several studies have identified fQRS as an independent predictor of ventricular arrhythmias and sudden cardiac death [10]. Recently, in a series of 452 patients with anterior STEMI undergoing primary PCI, fQRS was associated with target vessel failure but did not correlate with infarct size [11].…”

“…Its usefulness was demonstrated in various structural heart diseases, e.g. dilated cardiomyopathy, both ischaemic and non-ischaemic; hypertrophic cardiomyopathy [15]; cardiac sarcoidosis; arrhythmogenic right ventricular dysplasia [5,10]. Even subclinical left ventricular dysfunction assessed by echocardiography has been shown to be associated with fQRS in type-2 diabetic patients [16].…”