Life-Threatening Ventricular Arrhythmias: Current Role of Imaging in Diagnosis and Risk Assessment

Abstract

Sudden cardiac arrest continues to be a major cause of death from cardiovascular disease but our ability to predict patients at the highest risk of developing lethal ventricular arrhythmias remains limited. Left ventricular ejection fraction is inversely related to the risk of sudden death but has a low sensitivity and specificity for the population at risk. Nevertheless, it continues to be the main variable considered in identifying patients most likely to benefit from implantable defibrillators to prevent sudden death. Imaging myocardial sympathetic innervation with PET and SPECT as well as imaging characteristics of myocardial infarcts using gadolinium enhanced cardiac magnetic resonance are emerging as imaging modalities that may further refine patient selection beyond ejection fraction. This review will primarily focus on employing advanced imaging approaches to identify patients with left ventricular dysfunction that are most likely to develop lethal arrhythmias and benefit from inserting a primary prevention implantable cardiac defibrillator. While not yet tested in prospective studies, we will review risk prediction models incorporating quantitative imaging and biomarkers that have been developed that appear promising to identify those at highest risk of sudden death.

Risk Stratification for Sudden Cardiac Death After Myocardial Infarction

“…If this excess norepinephrine is present in areas containing viable myocardium, the myocytes may be subject to denervation hypersensitivity, which in turn may predispose to catecholamine-mediated arrhythmias. Studies using these agents found that patients exhibiting greater degrees of myocardial denervation (less uptake of the tracer) have higher mortality and more arrhythmic events (101)(102)(103). This technique for SCD risk stratification remains in the early stages, and significantly more data are needed before it can be incorporated into routine clinical practice.…”

Myocardial substrate after cardiac resynchronization therapy and the risk of ventricular arrhythmias

“…Use of a risk prediction model will understandably have a low sensitivity for predicting arrhythmic events; however, it offers a high specificity and a high negative predictive value to identify those at the lowest risk. This has been suggested in multiple prior studies utilizing imaging and biomarker-based risk prediction tools to predict arrhythmic events in various HF populations, 16 including a gated SPECT-based model of LV ejection fraction, myocardial scar. and dyssynchrony.…”