The Tachycardia-Bradycardia Syndrome (also known as sinoatrial disorder or the "sick sinus syndrome") can be caused by a variety of disorders that result in degeneration and/or fibrosis of the sinus node and other portions of the cardiac conduction syndrome.


Transient causes:

(1) acute myocardial infarction

(2) drugs (digitalis, quinidine, beta-blockers, aerosol propellants according to Wagner)


Chronic causes:

(1) ischemia associated with disease of the sinus nodal artery

(2) congenital heart disease affecting the conduction system

(3) cardiomyopathy

(4) amyloidosis

(5) autoimmune disease

(6) metastatic carcinoma

(7) surgical injury

(8) complications of inflammatory/infectious diseases (sepsis, myocarditis)

(9) rheumatic heart disease


It also may occur with no identifiable cause (idiopathic).


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