The abnormal appearance of the QRS complex, which was fragmented and has a visible notch on a standard 12-lead electrocardiogram (ECG), was considered to indicate depolarization abnormalities and imply cardiac danger. Defects in depolarization might have similar prognostic implications that go undetected by the human eye, and no technology was currently available to measure such invisible ECG anomalies. The method of signal processing projects all ECG leads of the QRS complex into 3 optimized perpendicular dimensions recreates the ECG back from this 3-dimensional projection. It identified the difference (QRS’ micro’-fragmentation, QRS-μf) between the original and restored signals. In 3 distinct populations, the research found that rate-distortion theory could predict more accurately than standard QRS’ micro’-fragmentation whether patients with cardiac conditions were likely to have an adverse event. The predictive value of QRS-μf for mortality was investigated univariately and in multivariable comparisons with other risk factors, including visible QRS’ macro’-fragmentation, QRS-Mf, as well as biventricular pacing. Researchers conducted a meta-analysis of 5,000 patients involved in the original trial. The analysis included all 5,000 people and was restricted to those that had not died within the first five years after recruitment. QRS-μf was significantly associated with survival in all three groups (P<0.001 univariably, and P<0.001 to P=0.024 in multivariable analyses). When analyzing the association between QRS-μf and outcome prospectively, a similar robust link was discovered when dichotomizing QRS-μf prospectively at 3.5%. When QRS-μf was utilized in multivariable analyses, the predictive value of QRS-Mf and QRS duration vanished. QRS-μf was an independent death risk indicator in 3 populations with diverse clinical profiles. The apparent QRS-Mf had a high sensitivity, which suggested that it could predict the onset of ventricular tachycardia. The abnormalities were likely responsible for the predictive value of visible QRS-Mf.
Link:academic.oup.com/eurheartj/advance-article/doi/10.1093/eurheartj/ehac085/6533247?searchresult=1
