Cardiac regulation and electrocardiographic factors contributing to the measurement of repolarization variability

Schema summarizing the list of factors influencing the VR process of the heart and the various electrocardiographic signs revealing the presence of myocardial arrhythmogenic substrate or myocardial vulnerability. In this schema, circles with common areas represent interaction between the associated groups of factors. For instance, a drug is defined as a clinical factor that can influence the VR directly or by modifying heart rate (HR), HR adaptation, and the ANS. Also, the effect of a drug might be dependent on an individual's age, sex, and genetic profile and electrolyte balance. The physiological and clinical factors can depend on the genetic makeup, age, and sex of a given individual. Reprinted with permission from Couderc.¹⁶

Power spectrum density of the RT apex interval variability measured from different leads. From top to bottom, leads X, Y, and Z revealed very different temporal and spectral profiles (left to right columns). Reprinted with permission from Porta et al.⁴³