QRS Micro-Fragmentation Predicts Mortality
abstract
This abstract is available on the publisher's site.
Access this abstract nowAims
Fragmented QRS complex with visible notching on standard 12-lead electrocardiogram (ECG) is understood to represent depolarization abnormalities and to signify risk of cardiac events. Depolarization abnormalities with similar prognostic implications likely exist beyond visual recognition but no technology is presently suitable for quantification of such invisible ECG abnormalities. We present such a technology.
Methods and results
A signal processing method projects all ECG leads of the QRS complex into optimized three perpendicular dimensions, reconstructs the ECG back from this three-dimensional projection, and quantifies the difference (QRS ‘micro’-fragmentation, QRS-μf) between the original and reconstructed signals. QRS ‘micro’-fragmentation was assessed in three different populations: cardiac patients with automatic implantable cardioverter-defibrillators, cardiac patients with severe abnormalities, and general public. The predictive value of QRS-μf for mortality was investigated both univariably and in multivariable comparisons with other risk factors including visible QRS ‘macro’-fragmentation, QRS-Mf. The analysis was made in a total of 7779 subjects of whom 504 have not survived the first 5 years of follow-up. In all three populations, QRS-μf was strongly predictive of survival (P < 0.001 univariably, and P < 0.001 to P = 0.024 in multivariable regression analyses). A similar strong association with outcome was found when dichotomizing QRS-μf prospectively at 3.5%. When QRS-μf was used in multivariable analyses, QRS-Mf and QRS duration lost their predictive value.
Conclusion
In three populations with different clinical characteristics, QRS-μf was a powerful mortality risk factor independent of several previously established risk indices. Electrophysiologic abnormalities that contribute to increased QRS-μf values are likely responsible for the predictive power of visible QRS-Mf.
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Additional Info
QRS micro-fragmentation as a mortality predictor
Eur Heart J 2022 Feb 21;[EPub Ahead of Print], K Hnatkova, I Andršová, T Novotný, A Britton, M Shipley, B Vandenberk, DJ Sprenkeler, J Junttila, T Reichlin, S Schlögl, MA Vos, T Friede, A Bauer, HV Huikuri, R Willems, G Schmidt, MR Franz, C Sticherling, M Zabel, M MalikFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
Conduction delay and block are critical electrophysiologic elements that serve as the basis for developing a reentrant tachyarrhythmia such as ventricular tachycardia (VT) or ventricular fibrillation (VF). Invasive electrophysiologists search for such abnormal areas to ablate and eradicate VT/VF. Prolonged QRS duration results from similar conduction delay and block, often in the bundle branches, and has served as a risk marker for adverse cardiac events for many years. Fragmented QRS — visible QRS notching on the standard 12-lead electrocardiogram (ECG) — represents depolarization abnormalities more recently recognized as features of intraventricular conduction delay or block,1 most likely from intramural myocardial scarring or interstitial fibrosis, and serves as a risk marker for sudden cardiac death.2
Because the notches in the QRS complex may exist at levels below the resolution of visual identification due to fragmentation and, thus, may be difficult or impossible to see on a standard 12-lead ECG, investigators have developed a signal processing method to project the ECG leads of the QRS complex into three perpendicular dimensions and to quantify the difference (QRS "micro"-fragmentation, or QRS-μf) between the original and reconstructed signals. They investigated the predictive value of such micro-fragmentation on mortality in 7779 cardiac patients with implantable cardioverter-defibrillators, cardiac patients with severe abnormalities, and the general public, of whom 504 did not survive the first 5 years of follow-up. They found that QRS-μf was strongly predictive of survival (P < .001 univariably, and P < .001 to P = .024 in multivariable regression analyses). They pointed out that micro-fragmentation may not be simply a refinement of macro-fragmentation, while still representing a risk for adverse cardiovascular outcomes, perhaps from heart failure.
The take-home message is that QRS-μf is a powerful mortality risk factor independent of several previously established risk indices. What is needed is a prospective randomized trial to demonstrate whether macro- and micro-fragmentation can be used together or independently to identify and therefore prevent sudden cardiac death in high-risk patients.
References