Ultra High Resolution CT to Assess Role of Intramyocardial Fat and Delayed Enhancement in Ventricular Arrhythmogenesis

Study Overview
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Brief Summary
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This research is being done to determine how well cardiac computed tomography (CT) scanning measures of fat within the heart can predict abnormal heart rhythms and how well cardiac CT can measure scar within the heart versus cardiac magnetic resonance imaging (MRI). People who have been enrolled in PROSe-ICD (NA_00045142) and Reynolds (NA_00037404) studies may join The procedures, tests, drugs or devices that are part of this research and will be paid for by the study

Detailed Description
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The investigators aim to investigate the role of intramyocardial fat on ventricular arrhythmogenesis. Intramyocardial fat deposition has been frequently observed in patients with ischemic heart disease and is readily detectable by multi-detector computed tomography (MDCT) with high sensitivity and specificity, unlike other modalities. Like intramyocardial fat, reentrant ventricular tachycardia (VT) tends to occur late after the onset of myocardial infarction and the investigators hypothesize that lipomatous metaplasia within the infarct may precipitate later onset ventricular arrhythmias (VA). Prior studies have shown that intramyocardial fat correlates with slow myocardial conduction velocity and with critical circuits for VA but the investigators do not know the causal relationship between intramyocardial fat and future risk of VA. Intramyocardial fat deposition or lipomatous metaplasia has been frequently observed in patients with ischemic heart disease and is readily detectable by multi-detector computed tomography (MDCT) with high sensitivity and specificity. Like intramyocardial fat, reentrant ventricular tachycardia (VT) tends to occur late after the onset of myocardial infarction and the investigators hypothesize that there may be a causal relationship. Prior studies have shown that intramyocardial fat correlates with slow myocardial conduction velocity and with critical circuits for VT in patients referred for VT ablation who already manifest VA. However, the correlation of intramyocardial fat on CT with late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) in a general population of patients with ischemic cardiomyopathy with no prior history of VA has not been reported. Specifically, it is unknown whether the presence, distribution and/or volume of fat is an independent predictor of VA. Further CMR is less widely available in medical centers, and is more expensive with longer scanning times compared to CT. CT provides higher spatial resolution, is widely available and is not as susceptible to magnetic interference from internal cardiac defibrillator (ICD) generators and thus makes it an attractive imaging modality for risk stratification, particularly longitudinally over time. Hypothesis: The investigators' objective is to define the prevalence and distribution of intramyocardial fat in patients with ischemic heart disease scheduled for or with in-situ implantable defibrillators. Further, the investigators aim to assess the independent association of intramyocardial fat with VA and determine whether it adds any utility above LGE measured by CMR. Finally, the investigators will assess how well delayed enhanced CT correlates with LGE on MRI and test its association with ventricular arrhythmias. Importance: The significance of the investigators' research is that the investigators will: 1) test whether intramyocardial fat on CT can be used as a non-invasive tool for sudden cardiac death risk stratification in patients who have or are scheduled to undergo ICDs, and 2) define whether delayed enhancement CT is comparable to the current non-invasive gold standard of CMR for identifying myocardial scar.

Official Title
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Ultra High Resolution CT to Assess Role of Intramyocardial Fat and Delayed Enhancement in Ventricular Arrhythmogenesis

Conditions
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Ventricular Arrhythmias

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients aged 18 or older with history of ischemic cardiomyopathy enrolled in the current Reynolds study or PROSe-ICD study will be asked to participate Women of child bearing potential must demonstrate a negative pregnancy test within 24 hours of the study CT Ability to understand and willingness to sign the Informed Consent Form Exclusion Criteria: Known allergy to iodinated contrast media Patients with glomerular filtration rate (GFR) ≤ 30 mL/min will not be enrolled in the study due to the use of intravenous iodinated contrast agents Atrial fibrillation or uncontrolled tachyarrhythmia Evidence of severe symptomatic heart failure (NYHA Class III or IV)

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 85 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| PROSe-ICD<br>PROSe-ICD [NCT00733590/ Institutional Review Board (IRB) NA_00045142], a large prospective cohort study of patients who received an ICD for primary prevention. | |
| Reynolds study<br>Functional Energetics (Reynolds study, NA_00037404), a study with conventional contrast-enhanced 1H MRI to determine ventricular geometry, global and regional function, as well as infarct size characteristics following delayed contrast enhancement. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Prevalence of intramyocardial fat in patients with ischemic heart disease | The primary aim is to test whether intramyocardial fat on MDCT is as effective or adds additional utility to risk stratification for VA above that of CMR-LGE characteristics in ischemic cardiomyopathy patients who are candidates for ICD therapy or have in situ ICDs. Our objective is to define the prevalence and distribution of intramyocardial fat in patients with ischemic heart disease scheduled for or with in-situ implantable defibrillators. Further, we aim to assess the independent association of intramyocardial fat with VA and determine whether it adds any utility above LGE measured by CMR. | 2 years | 
| Prevalence of delayed enhanced CT detected scar | Comparison of the scar distribution on delayed enhanced CT with LGE on cardiac MRI. The significance of our research is that we will test whether delayed enhanced CT can be used as a non-invasive tool for sudden cardiac death risk stratification in patients with ischemic heart disease and whether delayed enhancement CT is comparable to the current non-invasive gold standard of CMR for identifying myocardial scar. | 2 years | 
| Quantification of delayed enhanced CT detected scar | Comparison of the scar distribution on delayed enhanced CT with LGE on cardiac MRI. The significance of our research is that we will test whether delayed enhanced CT can be used as a non-invasive tool for sudden cardiac death risk stratification in patients with ischemic heart disease and whether delayed enhancement CT is comparable to the current non-invasive gold standard of CMR for identifying myocardial scar. | 2 years | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Ischemic Cardiomyopathy