Implantable Cardioverter Defibrillators - Improving Risk Stratification

Study Overview
=================
Brief Summary
-----------------
Worldwide three million people a year die from sudden cardiac death (SCD). In most cases there is no warning and the heart is stopped by a sudden arrhythmia. We know that some people are at high risk of sudden cardiac death and can prevent their deaths with an implantable cardioverter defibrillator (ICD) that is implanted in a minor operation. However, most people who die from sudden cardiac death are not found to be at high risk by our current risk markers and 40% of the people who have ICDs do not have therapy within the first 4 years after implant. We need new and better ways of identifying people who are at high risk of sudden cardiac death so that we can prevent their deaths with ICDs. Our understanding of the electrical signals in the heart has increased considerably in recent years; in no small part this is due to our Principal Investigator Professor Andre Ng's basic science work. This study aims to take the understanding of action potential duration (APD) restitution gained through our work and other studies in humans and in computer simulations and translate it into a fresh way of assessing risk of sudden cardiac death. This study will carefully examine electrical activity, using APD restitution, in the hearts of patients who are having ICDs fitted because of their high risk of sudden cardiac death and combine this with a detailed heart scan, assessment of autonomic nervous system and gene expression data. We will then follow these patients up to see who benefits from their ICD. This wide ranging information will give us as complete a picture as possible of the factors that cause sudden cardiac death. We hope to use this to identify better predictors of sudden cardiac death. The study hypotheses are as follows: Primary Regional Restitution Instability Index (R2I2) will be significantly higher in patients reaching the endpoint of ventricular endpoint / sudden cardiac death than in those not. An R2I2 cut-off of 1.03 will partition patients into high and low risk groups. Secondary Peri-infarct zone mass in grams will be significantly higher in patients reaching the endpoint of ventricular endpoint / sudden cardiac death than in those not.

Official Title
-----------------
Improving Risk Stratification of Patients for Implantable Cardioverter Defibrillators Through Electrophysiological Tests, Cardiac Magnetic Resonance Imaging, Autonomic Function Tests, RNA Analysis and Plasma Biomarkers.

Conditions
-----------------
Sudden Cardiac Death, Implantable Defibrillator User, Myocardial Infarction, Arrhythmias, Cardiac

Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Attending for ICD implantation under NICE criteria or attending for an ICD box-change procedure or attending for an Electrophysiological test as part of NICE assessment for ICD implantation Age >18 History of ischaemic heart disease or non-ischaemic cardiomyopathy or inherited sudden cardiac death syndrome. Exclusion Criteria: <28 days since acute coronary syndrome / cardiac surgery Unable to give informed consent Women who are pregnant / planning pregnancy Contraindication for defibrillator safety margin test Haemodynamic instability Severe valvular heart disease Symptomatic, severe, coronary artery disease Recent stroke

Ages Eligible for Study
-----------------
Minimum Age: 18 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Ischaemic cardiomyopathy group<br>Patients with ischaemic cardiomyopathy attending for ICD implantation / Ventricular tachycardia stimulation testing as part of ICD risk stratification | |
| Non-ischaemic cohort<br>Patients attending for ICD implantation / ventricular tachycardia stimulation test who do not have ischaemic cardiomyopathy. | |
| Control group<br>Patients attending for electrophysiological study with no conditions that place them at risk of sudden cardiac death. | |

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Regional Restitution Instability Index | Regional Restitution Instability Index (R2I2) is a measure of electrical instability. R2I2 is calculated as the mean of the standard deviation of the residuals from the mean gradients for each ECG lead across a range of diastolic intervals. An R2I2 cut-off of 1.03 (no units) will partition the study population into high and low risk groups. | 18months - 2years | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Peri-infarct zone | Peri-infarct zone is calculated from cardiac magnetic resonance imaging scans with late gadolinium enhancement. The full width half maximum technique will be used and Peri-infarct zone assessed using peri-infarct zone mass in grams. | 18months-2 years | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Action potential duration restitution, Ventricular arrhythmia, Sudden cardiac death, Peri-infarct zone, Electrocardiogram