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Methods used to detect beats include ECG, blood pressure, ballistocardiograms, [2] [3] and the pulse wave signal derived from a photoplethysmograph (PPG). ECG is considered the gold standard for HRV measurement [ 4 ] because it provides a direct reflection of cardiac electric activity.
Electrocardiography is the process of producing an electrocardiogram (ECG or EKG [a]), a recording of the heart's electrical activity through repeated cardiac cycles. [4] It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the heart [ 5 ] using electrodes placed on the skin.
The term normal sinus rhythm (NSR) is sometimes used to denote a specific type of sinus rhythm where all other measurements on the ECG also fall within designated normal limits, giving rise to the characteristic appearance of the ECG when the electrical conduction system of the heart is functioning normally; however, other sinus rhythms can be ...
The cycle also correlates to key electrocardiogram tracings: the T wave (which indicates ventricular diastole); the P wave (atrial systole); and the QRS 'spikes' complex (ventricular systole)—all shown as color purple-in-black segments. [1] [2] The Cardiac Cycle: Valve Positions, Blood Flow, and ECG The parts of a QRS complex and
differential vector element of surface area A, with infinitesimally small magnitude and direction normal to surface S: square meter (m 2) differential element of volume V enclosed by surface S: cubic meter (m 3) electric field: newton per coulomb (N⋅C −1), or equivalently, volt per meter (V⋅m −1)
The shape of the T wave is usually asymmetrical with a rounded peak. T wave inversions from V2 to V4 leads are frequently found and normal in children. In normal adults, T wave inversions from V2 to V3 are less commonly found but can be normal. [4] The depth of the T wave also becomes progressively shallow from one to the next lead. [5]
Schematic representation of normal ECG In electrocardiography , the ST segment connects the QRS complex and the T wave and has a duration of 0.005 to 0.150 sec (5 to 150 ms). It starts at the J point (junction between the QRS complex and ST segment) and ends at the beginning of the T wave.
The mean, normal SA in healthy young adult females and males is 66° and 80°, respectively, [9] and very similar magnitudes are found in the elderly population (65 years and older). [10] In ECG analysis, the SA is categorized into normal (below 105°), borderline abnormal (105–135°) and abnormal (greater than 135°). [11]