A Difference between the Depolarization Time and QRS Duration in Heart Failure Patients with LBBB: A Simulation Study

Background: A 66-year-old female with no previously recognized heart disease was admitted to a hospital due to loss of consciousness. At the scene, medical rescuers found the victim conscious, in full verbal and logical contact. ECG recording showed nodal rhythm with heart rate 26bpm. The patient was wearing a Holter recorder during the event. AECG was recommended due to dizziness and slow heart rate observed at home measurements. The patient denied dyspnoea, stenocardia or any medication which can cause bradycardia. After admission to a hospital acute coronary syndrome was excluded and echocardiography revealed hypetrophic cardiomyopathy.Holter recording showed intermittent sinus and nodal rhythms with average heart rate 34bpm, and min 20bpm during daytime. Several sinus pauses over 2 sec were observed, including 140 pauses with a duration of 4.0-6.6 sec. At 1:54:25 p.m. (during loss of consciousness) AECG revealed a pause of 93 seconds terminated with an escape ventricular beat followed by nodal rhythm with ventricular arrhythmia (nsVT, ventricular couples and single ventricular beats) [Fig. 1], Discussion: The presented ECG with the longest pause may cause diagnostic problems. The ECG strip with a pause shows an isoelectric line and visible artifacts. Such a pattern can also be observed in case of temporary interruption of ECG recording caused by loss of contact on the skin-electrode-recorder line. Diagnosis of "real" pause is supported by the clinical context (patient with dizziness and loss of consciousness) and analysis of the entire recording that showed frequent shorter sinus. Data on sick sinus syndrome in patients with hypertrophic cardiomyopathy is limited. Dizziness and loss of consciousness in this population is more frequently associated with hemodynamic impairment, AV blocks or ventricular arrhythmia.