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Table 4 Comparison of the conventional and the proposed ECG interpretation of the heart cycle phases

From: A vector-free ECG interpretation with P, QRS & T waves as unbalanced transitions between stable configurations of the heart electric field during P-R, S-T & T-P segments

Phases of the ECG cycle The conventional vector interpretation, based on textbook descriptions (1-4) The proposed interpretation based on displacement of the thoracic electric field center
Description Key events
T-P segment Isoelectric line The diastolic attractor defined by positive charges of atria, ventricles and extracardial thoracic tissues Most leads transect left ventricle wall, septal muscle and right ventricle wall along a specified line. The repolarised septal muscle makes distribution of charges symmetric and stable
P-wave Sinoatrial node generates action potential that quickly spreads via internodal fibers. Atrial muscle depolarizes Displacement of the thoracic electric field center due to diminished charges of the right atria, when both atria become depolarized, the center returns to the telediastolic attractor SA node initiates atrial depolarization from right to left and from cranial to caudal
P-R segment isoelectric line Telediastolic attractor defined by positive charges of ventricles and extracardial thoracic tissues The repolarised septal muscle makes distribution of charges symmetric and stable
H-wave AV node depolarizes Hiss bundles before the QRS complex Signal from the AV node depolarizes the septal muscle Disappearance of charges within the septum distorts the thoracic electric field and the moving center makes the Hwave.
Q The septum depolarizes from left to right. With depolarized septal muscle, there is no anchoring central source of positive charges. In each lead, the electric field center depends on peripheral charges in still polarized ventricular walls. Q-waves appear if the muscle mass in the wall near the “UP” electrode is reduced (i.e., ischemia) or if the muscle mass near the “DOWN” electrode is increased (i.e., right ventricle hypertrophy).
RS The anteroseptal region depolarizes first, ventricles depolarize from the endocardium toward the epicardium, spreads from the apex toward the base via Purkinje fibers. Each lead detects depolarization of left ventricle and right ventricle walls as a rapid displacement of the electric field center. Maximal displacement is reached when the peripheral part of left ventricle is not yet depolarized. The displacement of the thoracic field center after that quickly diminishes and the center returns to the systolic attractor
S-T segment The ventricles are fully depolarized. The thoracic electric field center is back to the systolic attractor defined by positive charges of atria and extracardial thoracic tissues Both ventricles and the septal muscle are sources of the weak negative charge, with limited influence on the position of the thoracic electric field center.
T-wave Ventricular repolarization Emergence of positive ventricular charges displaces the center temporary to the left, caudal and peripheral, Normally left ventricle wall prevails at the “UP” electrode. Repolarization of the septal muscles makes the emerging positive field stable and almost symmetric,
U wave in precordial leads Often attributed to repolarisation of papillary muscles or of Purkinje fibers When both ventricles are repolarised, the thoracic field center returns to the diastolic attractor position. U wave might reflect rapid diastolic filling of ventricles that temporary changes anatomical position of ventricular walls.