Molecular Mechanisms of Arrhythmias Flashcards
Almost all arrhythmias are ________.
acquired, such as from myocardial infarctions, ischemias, acidoses, alkaloses, drug toxicities, catecholamine exposure, or electrolyte abnormalities
Prolonged QT intervals correspond to ___________.
increased action potential duration, such as from blocked Ik channels or sodium channels that fail to inactivate
Mutations that lengthen the QT interval include those that ____________.
impair current amplitude through K channels and prevent the sodium channels from closing completely
Explain the pathophysiology of Brugada syndrome.
Mutations in sodium channels reduce peak sodium current; ventricular fibrillation results in 40% mortality by age 5.
What are two broad categories of arrhytmia origin?
Inappropriate impulse initiation in sinoatrial node or ectopic foci; disturbed impulse conduction in nodes, conduction cells, or myocytes
Only ________ have been shown to reduce the incidence of sudden cardiac death.
ß-blockers
Familial long QT syndrome results from a defect in ____________.
the phase 2 of fast contractile muscles
Familial long QT syndrome is __________.
polymorphic and autosomal dominant
There is another kind of congenital arrhythmia in which cardiac myocytes can upregulate CaL but not _________.
Iks, thus, the cell cannot repolarize effectively
Delayed afterdepolarizations occur because __________.
the NCX is electrogenic and depolarizes the membrane
A 1° conduction block will lead to a _________ on an ECG.
lengthend P-R time
A 2° conduction block will lead to ________ on an ECG.
some P waves not followed by QRS waves
A 3° conduction block will lead to _________ on an ECG.
no coordination between P waves and QRS waves
What drugs can cause arrhythmias?
Sulfamethoxazole, astemizole, terfenadine, and cardiac glycosides
What causes torsades de pointes?
Prolonged phase 2
