I45.9
Conduction disorders (ICD-10 I45.9, unspecified) are disturbances in the way the electrical impulse travels through the heart: from the sinus node through the atria, the AV node, the His bundle and the bundle branches to the ventricles. Arrhythmias and conduction disorders are caused by abnormalities in the formation of the impulse, its conduction, or both. Any heart disease can disturb them, including congenital structural abnormalities (for example an accessory pathway) and inherited ion channel diseases. Some conduction disorders are harmless; others can cause a very slow heart rate, fainting or sudden death.
Main types
- Sinus node dysfunction: slow sinus rate, pauses, alternating slow and fast rhythms (tachy-brady syndrome)
- First-degree AV block: PR over 200 ms, every impulse conducted
- Second-degree AV block: Mobitz I (Wenckebach, PR lengthens until a beat is dropped, usually benign, in the AV node) and Mobitz II (sudden non-conducted beats without PR change, below the AV node, risk of complete block)
- Third-degree (complete) AV block: no impulses reach the ventricles; a slow escape rhythm keeps the heart beating
- Bundle branch and fascicular blocks, non-specific intraventricular conduction delay
Causes
Age-related fibrosis of the conduction system, coronary disease and myocardial infarction, cardiomyopathies, myocarditis, infiltrative diseases, Lyme disease, valve disease and procedures, heart surgery, inherited disorders, medicines (beta-blockers, calcium-channel blockers, digoxin, antiarrhythmics), high potassium, hypothyroidism and high vagal tone.
Diagnosis and treatment
ECG, Holter or long-term rhythm monitoring (including implantable loop recorders), exercise testing and sometimes an electrophysiological study. Reversible causes (medicines, electrolytes, ischaemia, Lyme carditis) are treated first. A permanent pacemaker is indicated for symptomatic sinus node dysfunction, and for second-degree Mobitz II, advanced or complete AV block regardless of symptoms when no reversible cause is found.
for fainting, a very slow pulse (for example below 40/min) with dizziness, breathlessness, chest pain or confusion.
References
- Glikson M, Nielsen JC, Kronborg MB, et al. 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy. Eur Heart J. 2021;42(35):3427–3520. doi:10.1093/eurheartj/ehab364
- Kusumoto FM, Schoenfeld MH, Barrett C, et al. 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay. Circulation. 2019;140(8):e382–e482. doi:10.1161/CIR.0000000000000628
This article is for general information and does not replace a consultation with a doctor. Diagnosis and treatment must be decided by a physician on the basis of symptoms, examination and tests.
Published on 23 March 2019