A 60-year-old patient with heart failure (NYHA II) due to non-ischemic cardiomyopathy with a left ventricular end-diastolic diameter (LVEDD) of 73 mm and left ventricular ejection fraction (LVEF) 20% presented with intraventricular conduction delay (IVCD) and rate-dependent left bundle branch block (LBBB) at a rate above 90/min. During IVCD, ultra-high-frequency ECG (UHF-ECG) ventricular dyssynchrony was 40 ms