It is universally recognised that current methods for risk stratification of sudden cardiac death (SCD) are limited. A novel SCD risk marker, the Regional Restitution Instability Index (R2I2), measures the degree of heterogeneity in electrical restitution using data obtained from a standard 12 lead ECG acquired during an invasive electrophysiological study.

In an ischaemic cardiomyopathy (ICM) cohort of 66 patients, an R2I2 of ≥1.03 identified subjects with a significantly higher risk of ventricular arrhythmia (VA) or death (43%) compared with those with an R2I2 <1.03 (11%) (P=0.004).

This study will use non-invasive techniques to acquire electrical restitution data: exercise and pharmacological stress, and will incorporate body surface potential mapping to develop a non-invasive and high-resolution form of R2I2. Suitable patients will be recruited into a prospective, observational study.

HYPOTHESES:

PRIMARY:

1. R2I2 is predictive of ventricular arrhythmia (VA) / SCD in patients with ICM.
2. The exercise stress protocol will create a dynamic range of heart rates that allows ECG quantification of electrical restitution heterogeneity that correlates with invasive R2I2 and is predictive of VA/SCD. The pharmacological stress protocol will create a dynamic range of heart rates that allows ECG based quantification of electrical restitution heterogeneity that correlates with invasive R2I2 and is predictive of VA/SCD.

SECONDARY:

1. A high-resolution electrical map acquired using body surface potential mapping will correlate with R2I2 and these data can be included in the R2I2 calculation to improve its prediction of SCD/VA.
2. Serial measurement of R2I2 will produce consistent values.

Inclusion Criteria:

• Age >18
• History of ischaemic cardiomyopathy

Exclusion Criteria:

• Unable to give informed consent
• <28 days since cardiac surgery or acute coronary syndrome

Patients with ischaemic cardiomyopathy attending for ICD implantation