Table 1.

Basic Clinical and Expressional Study Characteristics of Described Human Mutant HCN4 Channels

Mutation	Patients (pt)	Bradycardia at Rest	Symptoms	Chronotropic Incompetence	Need for Permanent Pacemaker	Loss of Channel Function Due to
						Trafficking Defect	Change in Biophysical Properties
573× 20	Single pt	Yes	Syncope	Yes	Yes	No	Yes
D553N21	Single pt	Yes	Syncope	No	Yes	Yes	No
S672R19	One family	Yes	No	No	No	No	Yes
G480R22	One family	Yes	No	No	No	Yes	Yes
A585V46	Three families	Yes	Presyncope	No	No	Yes	Yes