Replacement systole I49.4

Synonyms

Replacement Beat; Escape(d) Beat;

A replacement systole is a cardiac action that occurs as a substitute for a failed sinus impulse (Herold 2022).

This occurs as soon as excitation in the sinus node slows down or fails, or when conduction is blocked (Roskamm 2004).

Replacement systole is one of the stimulation 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 systole belongs to the passive heterotopic RBS (Herold 2022).

The replacement systole is caused when

- the pulse frequency of the sinus rhythm falls below a critical limit

- the transmission of the stimulus from the sinus node is disturbed (as is the case, for example, with SA block or AV block ).

If only one sinus pulse fails, this is referred to as a replacement systole; if several sinus pulses fail, this is referred to as a replacement rhythm (Herold 2022).

Replacement systole may be asymptomatic or perceived as palpitation by the patient (Christ 2022).

Prognosis depends on the underlying disease of the heart (Haverkamp 2022).

General information

A replacement systole occurs with a slight delay from the normal interval. It originates in the secondary, tertiary, or deeper excitation formation centers of the heart.

Subsequently, excitation occurs again, originating from the sinus node. The interval replacement systole - sinus beat is shorter than the normal RR- interval (Schley 1986).

Supraventricular replacement activity originates predominantly from the area of the His bundle, the AV node or from the orifice of the coronary sinus. This results in retrograde excitation of the atria, 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).

1. Christ J (2022) Cardiology Basics Elsevier Urban und Fischer Verlag Germany 79
2. Haverkamp W (2022) Focus ECG: ECG knowledge for practice. ExCard Research GmbH https://www.fokus-ekg.de/inhalt-von-a-z/extrasystolen-ersatzrhythmen-und-akzellerierte-rhythmen/ersatzrhythmen/
3. Herold G et al (2022) Internal medicine. Herold Publishers 273 - 274
4. Kasper D L et al (2015) Harrison's Principles of Internal Medicine. Mc Graw Hill Education 1475
5. Roskamm H, Neumann F J, Kalusche D, Bestehorn H P (2004) Heart disease: pathophysiology - diagnosis - therapy. Springer Verlag Berlin / Heidelberg / New York 370
6. Schley G (1986) Electrocardiography: an introduction. Springer Verlag Berlin / Heidelberg / New York / Tokyo 126, 132