Unidirectional block

A unidirectional block in the conduction of excitation in the heart is the phenomenon that the excitation in a part of the heart muscle tissue cannot be passed on in the forward direction (antegrade), but can be passed on in the backward direction (retrograde). If the tissue blocked while the excitation front is passing on the forward path is then retrograde excited on another path, there is the possibility of a circular excitation occurring .

A unidirectional block does not have to be permanently present in a tissue section; it can also only occur as a functional block under certain conditions.

Initial description

The term unidirectional block was introduced in 1928 by Francis O. Schmitt and Joseph Erlanger .

meaning

The unidirectional block as a prerequisite for circular excitation is therefore an important cause for the development of life-threatening ventricular tachycardias .

causes

A unidirectional block in the heart muscle tissue can itself have a variety of causes:

Ischemia ( coronary artery disease )
Infection ( myocarditis )
Cardiomyopathies
Electrolyte disorders ( hyperkalemia , hypokalaemia )
endocrine diseases ( hyperthyroidism , hypothyroidism )
Cor pulmonale
mechanical factors (congenital and acquired heart defects, trauma )
congenital or acquired heart defects
Poisoning ( digitalis , nicotine , antiarrhythmics )
Mitral valve prolapse
psychological factors ( depression )

literature

Q. Sesto: How does a unidirectional block arise as part of a circular excitation? In: F. Sesto (Ed.): Arrhythmie-Kompendium IV. Springer, Berlin, Heidelberg. 1988. ISBN 978-3-540-19046-2 . Online: doi: 10.1007 / 978-3-642-93378-3_42
Cook-Sup So: Practical EKG interpretation. , Thieme. 4th edition, 2013. ISBN 978-3-13-112684-9 . Online: doi: 10.1055 / b-0034-59924

Individual evidence

↑ J. Jung: Antitachycardia stimulation. In: Stefano Accinelli (Hrsg.): Pacemaker and defibrillator therapy: indication, programming, aftercare. Georg Thieme Verlag, 2006. p. 347. ISBN 978-3-13-117181-8
↑ Schmitt, Francis O., and Joseph Erlanger. Directional differences in the conduction of the impulse through heart muscle and their possible relation to extrasystolic and fibrillary contractions . American Journal of Physiology-Legacy Content 87.2 (1928): 326-347.

[1] J. Jung: Antitachycardia stimulation. In: Stefano Accinelli (Hrsg.): Pacemaker and defibrillator therapy: indication, programming, aftercare. Georg Thieme Verlag, 2006. p. 347. ISBN 978-3-13-117181-8

[2] Schmitt, Francis O., and Joseph Erlanger. Directional differences in the conduction of the impulse through heart muscle and their possible relation to extrasystolic and fibrillary contractions . American Journal of Physiology-Legacy Content 87.2 (1928): 326-347.