Left ventricular shape index and eccentricity index assessed by gated PET/CT. Promising parameters for detection of left ventricular remodelling
Authors: Martinez-Lucio T S , Carvajal-Juarez I , Mendoza-Ibanez A K , Mendoza-Ibanez O I , Tsoumpas C , Slart R H J A , Alexanderson-Rosas E 
Published: June 2023

Abstract

Funding Acknowledgements
Type of funding sources: Public Institution(s). Main funding source(s): University of Groningen/University Medical Center Groningen.

Background
Left ventricular (LV) remodelling has been described as the pathway that precedes heart failure. This process consists of changes in the shape, size, volume and function of the left ventricle; all of this directly associated to increased risk of major adverse cardiac events (MACEs). Different parameters are used to evaluate cardiac geometry in multiple cardiac imaging modalities. In nuclear medicine, LV geometry can be studied through shape index (SI) and eccentricity index (EI). These values examine the degree of sphericity (SI) and elongation (EI) of the left ventricle. However, in cardiac perfusion PET/CT, the LV remodelling has not been extensively studied with SI and EI values, and their role is yet to be elucidated.

Purpose
This project aim to describe the role of SI and EI values in patients examined by gated 13N-ammonia PET/CT in ischemic and infarction scenario.

Methods
We retrospectively randomly selected 140 patients referred to 13N-ammonia PET/CT between 2016 and 2022 for suspected or diagnosed CAD. The patients were classified in 4 groups of 35 patients according to the presence and burden of ischemia or infarction: normal=0% of scar burden and ischemic burden; mild ischemia=5–10% of ischemic burden; moderate-severe ischemia≥10% of ischemic burden and infarction≥5% of scar burden. We collected the information regarding myocardial flows (myocardial blood flow (MBF) at rest, hyperaemic MBF at stress and coronary flow reserve (CFR)) and left ventricular geometry (SI end-diastolic at rest and stress, SI end-systolic at rest and stress, and EI at rest and stress). All the variables were automatically processed with QPS/QGS software. We performed a multicomparison analysis for the mentioned variables with One way ANOVA variance and Dunnett’s Test as Post Hoc, stablishing as the control the infarction group.

Results
The study population consisted of 35.7% women, all patients over 36 years old, with no significant differences between groups regarding the presence of cardiac risk factors. The control group showed important changes in all SI and EI when compared to the rest of the groups. With a maximum change of 0.090 observed in SI end-systolic stress in the mild ischemia group, and a minimum change of −0.041 in EI rest in the moderate-severe ischemia group. Control subjects had statistically significant higher values of SI end-diastolic rest (p&lt;0.001) and stress (p = 0.005), end-systolic rest (p = 0.001)and stress (p&lt;0.001) and statistically significant lower values of EI rest (p&lt;0.001) and stress (p&lt;0.001) when compared with all the other groups. Additionally, all SI and EI values in stress follow a linear change proportional to the degree of myocardial extend (Figure 1 and 2).

Conclusions(s)
SI and EI by 13N-ammonia PET/CT are variables that seem clinically relevant for the early detection of LV remodeling. However, there is still research to do for establishing cut-off values and evaluating the prediction of MACEs.