The purpose of this study is to collect surface electrograms from standard and several non-standard configurations in patients with long QT syndrome, heart failure, cardiac resynchronization therapy or wide QRS during a routine outpatient assessment. The ECGs collected will be used as test signals by the sponsor for the development of a subcutaneous implantable defibrillator

The objective of this study is to record standard ECG signals is each of the 4 patient populations together with signals from 4 non-standard surface positions when these patients attend the outpatient department for follow-up. The non-standard electrode positions mimic the positions of the subcutaneous electrodes of the subcutaneous implantable defibrillator (S-ICD) system in development by Cameron Health.

The collection of these signals will allow bench testing of the algorithms proposed for the S-ICD system. Additionally, it will allow a comparison of the response of different defibrillators to these same signals to asses how each would treat a particular rhythm.

Inclusion Criteria:

• Patients attending the outpatient for routine follow-up for their cardiac disease or to have an implanted device follow-up

Exclusion Criteria:

• Patients unable or unwilling to provide informed consent
• Any condition which precludes the subject's ability to comply with the study requirements, including completion of the study

Patients with long QT syndrome, heart failure, cardiac resynchronization therapy or wide QRS.