Novel Imaging Approaches for Predicting Arrhythmic Risk

Abstract

Abstract-Determination of ventricular arrhythmic risk is crucial for guiding management of cardiac disease. Although for patients at increased risk an implantable cardioverter-defibrillator is recommended, it is widely acknowledged that current criteria for device use based predominantly on left ventricular ejection fraction are deficient. Genesis of ventricular arrhythmias involves a complex interaction of myocardial substrate abnormalities, precipitating triggers, and modulating factors. There are much data showing that by more directly assessing these factors, noninvasive imaging using echocardiography, radionuclide imaging, and cardiac magnetic resonance enhances arrhythmic risk stratification beyond ejection fraction and commonly used electrocardiographic and serum biomarkers. It is anticipated that further technological advancements studied in well-designed clinical trials will provide both more precise determination of risk and guide therapies to enhanced survival and patient well-being.

RyR2R420Q catecholaminergic polymorphic ventricular tachycardia mutation induces bradycardia by disturbing the coupled clock pacemaker mechanism

“…Besides the intrinsic defect related to the RyR 2 mutation, other mechanisms may account for the observed sinus bradycardia, such as a decreased sympathetic tone due to a lower β-AR density and/or a reduced presynaptic catecholamine recycling. The resulting sympathetic denervation may create a proarrhythmic substrate, which could contribute to the initiation of sustained ventricular arrhythmias (22). In this scenario, a given increase in the systemic autonomic tone may trigger a life-threatening arrhythmia in a denervated hypersensitive myocardium, which may accentuate electric heterogeneities of primary arrhythmic conditions (22).…”

“…Besides SAN dysfunction primarily caused by abnormal ion channel activity in SAN cells, there existed the possibility that β-adrenergic signaling could be modified in these patients, as neurons also express RyR 2 (26). In fact, patients with arrhythmogenic right ventricular cardiomyopathy, right ventricular outflow tract tachycardia, and ischemic heart disease have been shown to exhibit left ventricular patchy defects in radionuclide distribution, which may identify patients at risk of ventricular arrhythmias and SCD (22). Planar or SPECT imaging with 123 I-MIBG is a pharmaceutical suitable test for the presynaptic portion of the cardiac adrenergic innervation (27)-although recently, other techniques have also been used, such as PET with 11 C-labeled norepinephrine analog [ 11 C]-hydroxyephedrine (22).…”

“…In fact, patients with arrhythmogenic right ventricular cardiomyopathy, right ventricular outflow tract tachycardia, and ischemic heart disease have been shown to exhibit left ventricular patchy defects in radionuclide distribution, which may identify patients at risk of ventricular arrhythmias and SCD (22). Planar or SPECT imaging with 123 I-MIBG is a pharmaceutical suitable test for the presynaptic portion of the cardiac adrenergic innervation (27)-although recently, other techniques have also been used, such as PET with 11 C-labeled norepinephrine analog [ 11 C]-hydroxyephedrine (22). A decreased β-AR function has been reported in heart failure, which may also be associated with SAN dysfunction (28).…”

Assessing arrhythmic risk with 123I-mIBG and analogous tracers: Image interpretation from a different viewpoint

“…4 With current practice, [80% of primary prevention patients do not use their ICD over a duration of as long as 8 years, with the device costing as high as $235,000 per year of life saved, and with a significant potential for serious device complications. 5 It is clear that a better approach to selecting HF patients for primary prevention ICD implantation is needed.…”

Noninvasive myocardial blood flow assessment: Another marker of arrhythmic risk?

“…7 Many imaging modalities can assess the arrhythmogenic substrate. 8 Global longitudinal strain on echocardiography has been shown to predict ventricular arrhythmias independent of LVEF in patients with ischemic and nonischemic cardiomyopathy.…”