Table 1 Functional properties and diseases associated with different CM subtypes.

Cardiac subtypeAction potential shapePropertiesAssociated diseases
Sinoatrial nodal cellsEmbedded ImageSpontaneous depolarization; slow
action potential upstroke mediated
by calcium currents and almost
complete absence of fast sodium
currents; lacks IK1 current but has
prominent If current
Sinus bradycardia, sinoatrial block,
bradycardia-tachycardia syndrome
Atrioventricular nodal cellsEmbedded ImageSimilar to the sinoatrial nodal cells
but with slower intrinsic rate
Atrioventricular block,
atrioventricular nodal reentrant
tachycardia
Atrial cellsEmbedded ImageMore negative resting membrane
potential compared to pacemaker
cells; shorter action potential
duration compared to ventricular
CMs; prominent IKur and IKACh
currents
Atrial fibrillation
Ventricular cellsEmbedded ImageAction potentials with a clear plateau
phase; prominent IK1, IKr, and IKs
currents; transmural heterogeneity
Rhythm disorders (long QT
syndrome, LEOPARD syndrome,
catecholaminergic polymorphic
ventricular tachycardia),
cardiomyopathies (hypertrophic
cardiomyopathy, dilated
cardiomyopathy, arrhythmogenic
right ventricular cardiomyopathy)
Purkinje cellsEmbedded ImageLonger action potentials with a more
negative plateau phase;
prominent Ito current compared to
ventricular CMs
Congenital histiocytoid
cardiomyopathy