Automated Quantification of Abnormal QRS Peaks From High‐Resolution ECGs Predicts Late Ventricular Arrhythmias in Hypertrophic Cardiomyopathy: A 5‐Year Prospective Multicenter Study

Figure 1. Quantification of QRSp. A, Illustration of the QRSp method applied to lead V5 of a representative patient. A total of 5 positive (green circles) and 5 negative (green squares) abnormal QRS peaks are identified on the lQRS (solid black line denoting the unfiltered 10‐beat QRS signal average) after identifying 3 normal peaks (red diamonds) using the smoothed gQRS (dashed red line denoting the smoothing filtered 100‐beat QRS signal average). The number of positive and negative abnormal peaks is summed to produce a QRSp score of 10. B, Illustrative example of normal QRS peak classification using a magnified view of the same QRS complex as in A. A negative normal peak is identified on the smoothed gQRS (black x). The most negative normal peak on the lQRS within ±10 milliseconds of the gQRS peak (shaded area) is classified as normal. gQRS indicates global QRS average; lQRS, local QRS average; and QRSp, intra‐QRS peaks.

Figure 2. Performance of QRSp max and QRSp mean in predicting arrhythmic events. Box plots comparing (A) QRSp max and (B) QRSp mean between patients with and without VA events. C, Receiver operating characteristic curves for QRSp max (red solid line) and QRSp mean (blue dashed line) as a predictor of VA events for 5 years. Black circles highlight the sensitivity and 1‐specificity obtained by using a QRSp max cut point ≥4 and a QRSp mean cut point ≥1.08. D, Bar graphs comparing the prognostic performance of the QRSp max and QRSp mean cut points for identifying patients with VA events for 5 years. QRSp mean is the average QRSp of V1 to V6. AUC indicates area under the curve; NPV, negative predictive value; PPV, positive predictive value; QRSp, intra‐QRS peaks; QRSp max, maximum QRSp in V1 to V6; and VA, ventricular arrhythmia.

Figure 3. KM survival curves for VA events. KM survival curves for VA events stratified by (A) QRSp ≥4, (B) age <50 years, and (C) the combined QRSp ≥4 and age <50 years classifications. KM indicates Kaplan–Meier; QRSp, intra‐QRS peaks; and VA, ventricular arrhythmia.

Figure 4. Examples of QRSp in patients aged <50 and ≥50 years with and without VA events. QRSp results for a single 10‐beat window from (A) a younger patient (aged <50 years) with no VA event, (B) a younger patient (aged <50 years) with a VA event, (C) an older patient (aged ≥50 years) with no VA event, and (D) an older patient (aged ≥50 years) with a VA event. Irrespective of their age, the patients with VA events have greater individual precordial lead QRSp values (V1p–V6p) and maximum QRSp in V1 to V6 than those without VA events. Solid black lines indicate the local QRS average (ie, the unfiltered 10‐beat QRS signal average), and dashed blue lines indicate the global QRS average (ie, the smoothing filtered 100‐beat QRS signal average). Normal peaks are annotated with red diamonds, and abnormal peaks are annotated with green circles. QRSd indicates QRS duration; QRSp, intra‐QRS peaks; V1p to V6p, QRSp values of leads V1 to V6; and VA, ventricular arrhythmia.