PubMed · 13591390
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J STERNE. 1958. [The electrocardiogram].. https://pubmed.ncbi.nlm.nih.gov/13591390/
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Cyclic bursts of ventricular premature contractions (VPC) coming at minute-order intervals have been discerned by analyzing ambulatory ECG recordings, and their mechanism has not been clarified. The present study simulates this phenomenon by constructing a bidirectional modulated parasystole model. With Ts and Te as the intrinsic periods of the sinus and ectopic pacemakers, there are distinct and initial condition-dependent solutions in the model with Ts / Te values close to 1, 1/2, 1/4, etc. Typically, two distinct stable solutions are found existing together around Ts / Te = 1/2. We have verified theoretically the coexistence of different solutions and their dependence on the model parameters. The solution presented switches between those by a premature stimulus and those by fluctuations in the model parameters such as Ts. Patterns of RR intervals were generated by simulation with randomly fluctuating Ts. They included cyclic bursts of bigeminy of the "flat type" and the "dome type" reported by Takayanagi et al. (1999) and other transient types with Wenckebach or reverse Wenckebach rhythm of coupling intervals. This model provides a mathematical representation of the atrioventricular feedback mechanism and enables the modulated parasystole hypothesis to be applied to wider classes of VPCs.
Signal-averaged electrocardiograms (SAECGs) were recorded with bipolar orthogonal and standard 12-lead settings in 29 term healthy newborn infants. SAECGs performed with the two lead configurations were similar in quality and quantity. For the duration of the QRS complex (QRSD), the upper limit of normality for newborn infants can be set to 100 ms. It is similar in individual bipolar orthogonal and individual standard 12-lead recordings as well as in filtered QRSD in the vectorcardiograms (the vector magnitude, VM, and the sum of extremity leads). In individual leads of bipolar orthogonal and standard 12-lead recordings, root-mean-square voltage of the terminal 40 ms of the QRS complex (RMS40) is widely scattered and unsuitable as discriminant variable. For VM and the sum of the extremity leads, the same reference values for RMS40 and duration of low-amplitude signal can be used as applied in adults. Individual lead recordings provide complementary information in addition to vectorcardiograms. There are practical advantages using standard 12-lead compared to conventional bipolar orthogonal configurations. The widespread use of standard 12-lead ECG in routine medical practice makes its utility advantageous also in performing signal-averaged electrocardiography.
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