Synonyms
Replacement Rhythm;
Definition
A replacement rhythm is a substitute cardiac action that starts (Kalkreuth 1996) as soon as there is a slowing or failure of excitation in the sinus node or a blockage of excitation conduction (Roskamm 2004).
If there is only one missing impulse, this is referred to as a replacement systole. However, if several impulses fail, heterotopic replacement centers form a so-called replacement rhythm (Herold 2022).
Replacement rhythm belongs to the stimulus formation disorders (RBS). RBS are divided into:
- nomotopic RBS:
- RBS originating from the sinus node
- heterotopic RBS:
- RBS originating outside the sinus node (active or passive).
The replacement rhythm belongs to the passive heterotopic RBS (Herold 2022).
A replacement rhythm is caused when
- the pulse frequency of the sinus rhythm falls below a critical limit
- the transmission of impulses from the sinus node is disturbed (as is the case, for example, with SA block or AV block ).
(Herold 2022)
Normally, the sinus node - as the primary automatic center - transmits the rhythm transmitted to the entire myocardium as a nomotopic sinus rhythm with a frequency between 60 - 80 / min. In case of failure of the sinus node or in the presence of a disturbance of the conduction of the stimulus, an active or passive heterotopic stimulus formation takes place in the lower situated centers such as the secondary automation center, which includes the AV- node with 40 - 60 beats / min and the tertiary automation center, which includes the Purkinje- fibers and the His- bundle with a frequency between 20 - 40 / min (Nitschkoff 2022 /Pschyrembel 2022).
A replacement rhythm may be asymptomatic or perceived as palpitation by the patient (Christ 2022).
The therapy depends on the underlying disease and can, for example, consist of a pacemaker implantation. For more details see d.
Prognosis depends on the underlying disease of the heart (Haverkamp 2022).
General information
The secondary and tertiary automatic centers of the heart are recognizable in the ECG as supraventricular or ventricular replacement rhythms.
A supraventricular replacement rhythm originates predominantly from the area of the His bundle, the AV node or from the orifice of the coronary sinus. This leads to retrograde excitation of the atria, which is usually recognizable in the ECG by a negative P in II, III and aVF. (Roskamm 2004).
In ventricular replacement activity, the excitation comes from tertiary or ventricular automatic centers. Deformed and dissociated ventricular complexes are found in the ECG (Roskamm 2004).