Original Article
Comparison of left ventricle mechanical dyssynchrony parameters in ischemic and non-ischemic patients using 13N-NH3 PET/CT

https://doi.org/10.1007/s12350-020-02466-wGet rights and content

Abstract

Background-Aim

The relationship between perfusion pattern and stress-induced changes in Left Ventricular Mechanical Dyssynchrony (LVMD) has been previously described with controversial results using stress-rest perfusion imaging studies. The aim of this study was to assess the relationship between perfusion pattern and stress-induced changes in LVMD usingo regadenoson/rest13N-NH3 PET/CT.

Methods

There were 74 patients who underwent stress-rest 13N-NH PET/CT from January 2014 to October 2018 excluding patients with left bundle branch block, ventricular pacing and myocardial necrosis. The patients were divided into those with reversible perfusion defects at stress (Ischemic group, n = 18) and patients without reversible perfusion defects (non-ischemic group, n = 56). The LVMD parameters included: phase standard deviation (PSD) and phase histogram bandwidth (PHB), after stress and at rest. The ΔPSD (post-stressPSD-restPSD) and ΔPHB (post-stressPHB—restPHB) were calculated to measure stress-induced changes in LVMD.

Results

There were no significant differences in LVMD parameters between post-stress and at rest in both groups. The PSD post-stress, ΔPSD and PHB post-stress were significantly higher in the ischemic group.

Conclusions

Using a vasodilator as a stress, the PSD and PHB post-stress and ΔPSD were significantly higher in the ischemic patients than the non-ischemic group, while there were no significant differences in each cohort between stress and rest indices.

Introduction

Left ventricular mechanical dyssynchrony (LVMD) is defined as the differences in the timing of onset of contraction between the different myocardial segments and it may have prognostic value for risk stratification.1,2 LVMD by phase analysis of gated myocardial perfusion imaging (MPI) has emerged as a robust, automated, and reproducible technique to quantify mechanical dispersion.3 13N-ammonia (13N-NH3) may be used in PET/TC imaging and allows quantification of coronary flow reserve (CFR), myocardial blood flow (MBF) LV perfusion, wall motion, LV function and LVMD in patients with Coronary artery disease (CAD). Previous studies4, 5, 6 with different radiotracers such as Rubidium-82 and 99mTc-sestamibi, demonstrated that stress-induced ischemia causes dyssynchronous contraction in the ischemic region, leading to worsening of LVMD, but no previous study has examined the use of 13N-NH3. The aim of this study was to evaluate the relationship between perfusion pattern and stress-induced changes in LVMD using 13N-NH3 PET/CT after regadenoson stress and at rest.

Section snippets

PET/CT Imaging and Interpretation

Patients were in fasting state for stress studies. Maximal vasodilatation was obtained after I.V. injection of 400 mg of regadenoson over 10 seconds in the right antecubital vein followed by a bolus administration of a standard dose of 370 MBq of 13NH3 40 seconds after the end of regadenoson injection. The PET studies were acquired in 3D and list mode for 10 minutes starting acquisition immediately before 13NH3 injection by a discovery PET/CT 690 (GE Healthcare, Milwaukee, h Wisconsin, USA). A

Results

The demographics are in Table 1. Non significant differences were observed between ischemic and non-ischemic groups except of sex and history of diabetes. The LVMD parameters are in Table 2. The LVMD parameters (PSD and PHB) were not significant differences between stress and rest in each group. All LVMD parameters were higher in the ischemic patients compared to non- ischemic ones, but only PSD post- stress—ΔPSD—and PHB post stress were statistically significant. The correlation matrix between

Discussion

Intraventricular dyssynchrony reflects inhomogeneous timing of contraction of different myocardial segments, caused by disturbed myocyte stimulation or impaired contractility.8,9 It is helpful to recognize that even structurally normal hearts exhibit some degree of non-uniformity in contraction due to its complex spatial and geometric architecture. Contraction movements depend on the complex distribution of myocardial fibers within the epicardial and endocardial regions as they are oriented

New Knowledge Gained

13N-NH3 PET/TC represent a reliable method for estimating myocardial dyssynchrony parameters. The presence of ischemia is confirmed by a non-synchronous contraction of myocardial tissue and a decrease of myocardial blood flow, parameters evaluated after pharmacological stress test conducted with the use of regadenoson.

Funding

Open access funding provided by Università degli Studi di Brescia within the CRUI-CARE Agreement.

Disclosure

The Authors do not have any conflict of interest to declare.

Ethical standards

This human study has been approved by the institutional ethics committee and has therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.

Informed consent

All persons gave their informed consent prior to their inclusion in the study.

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