Original ArticleThree-dimensional Fusion of Myocardial Perfusion SPECT and Invasive Coronary Angiography Guides Coronary Revascularization
Introduction
The degree of coronary stenosis on invasive coronary angiography (ICA) is considered as the gold standard for the diagnosis and treatment of coronary artery disease (CAD). However, anatomical stenosis does not always contribute to inducible ischemia on perfusion imaging. Hemodynamically significant coronary artery stenosis refers to coronary artery lesion, from atherosclerosis, or spasm resulting in hypoperfusion of a given myocardial territory.1 The ideal tool to evaluate coronary circulation should provide both anatomical and physiological information.
Myocardial perfusion imaging (MPI) using single-photon emission computed tomography (SPECT) is a well-established non-invasive method that has been widely used to assess the functional significance of coronary stenosis. SPECT MPI has been recommended as a gatekeeper prior to ICA, to inform revascularization2 and such an approach is associated with an excellent prognosis. However, as a non-invasive test, values of SPECT MPI are limited by low sensitivity, issues with image quality, and the possibility of balanced ischemia. Moreover, the misassignment of myocardial segments to the concerned coronary arteries obtained by coronary computed tomography angiography (CCTA) is quite common. It has been reported that 72% of patients have arterial distribution different from the standard assignment in at least one myocardial segment due to patient-specific variations of the coronary anatomy.3
The combination of anatomy and physiology by fusion of imaging data may have a role in improving the diagnosis and management of CAD.4 Current guidelines recommend that patients with low-to-intermediate pretest probability for stable CAD undergo CCTA, which has a high negative predictive value, while patients with intermediate-to-high pretest probability should be referred for functional testing, including SPECT MPI. Nevertheless, most of the existing studies focused on the fusion between SPECT MPI and CCTA, but few studies have reported results on the utility of fusion of SPECT MPI and ICA data. We have previously developed a 3D fusion approach that combines SPECT MPI and ICA with a high technical accuracy to guide myocardial revascularization.5,6 In this study, we aim to evaluate the diagnostic and prognostic values of the 3D fusion approach compared to the side-by-side analysis.
Section snippets
Study Population
We retrospectively analyzed SPECT MPI and ICA data from 36 patients, all of whom had suspected CAD. For each patient, SPECT MPI was acquired before ICA and the time interval between them was 10.5 ± 14.5 days (all < 3 months). All patients included in this analysis had at least one segment stenosis (≥ 50%) diagnosed by ICA. The exclusion criteria were (1) previous bypass graft lesion or stent implantation, (2) previous myocardial infarction, (3) dilated cardiomyopathy (DCM), (4) hypertrophic
Patient Characteristics
Thirty-six patients who meet the inclusion criteria were analyzed. Baseline characteristics of the study population are listed in Table 1.
SPECT MPI Results
SPECT revealed abnormal perfusion in 27 patients, including 9 fixed, 20 reversible, and 1 mixed perfusion defect. Among the perfusion defects, 18 defects were in the anterior and septal wall, 11 were in the inferior wall, and 11 were in the posterior and lateral wall. Nine patients did not have any perfusion abnormality on MPI.
ICA Results
A total of 697 coronary segments
Discussion
Our study demonstrates that compared with the side-by-side analysis, the SPECT/ICA fusion could (1) significantly reduce the number of coronary stenosis segments with uncertainty, especially for the LCX artery, (2) guide the decision making for patient treatment which could improve the prognosis of CAD.
Revascularization based only on the anatomical criteria has been proved to have no additional benefit for long-term survival, and guidelines recommend the proof of ischemia prior to
Study Limitations
The study is limited by its observational nature. Due to the small number of patients studied, independent predictors of MACE could not be assessed. A larger prospective study will be needed to confirm the independent prognostic value of our fusion methodology. Additionally, abnormalities on MPI were not categorized as ischemia or infarction or both. While categorizing these defects may have a value in predicting outcomes after revascularization, this is not the focus of this pilot study and
New Knowledge Gained
The fusion between perfusion data from SPECT MPI and coronary anatomy from invasive coronary angiography reduced the number of equivocal coronary segments. Patients who received the same treatment as the guidance of 3D fusion results had superior outcomes when compared with those who did not.
Conclusions
Compared with the side-by-side analysis, 3D fusion between SPECT MPI and ICA provided incremental diagnostic and prognostic values for revascularization.
Acknowledgments
The authors have indicated they have no financial conflict of interest.
Disclosures
None of the authors, including Zhihui Xu, Haipeng Tang, Saurabh Malhotra, Minghao Dong, Chen Zhao, Zekang Ye, Ying Zhou, Shun Xu, Dianfu Li, Cheng Wang and Weihua Zhou, has any relevant conflicts of interest.
Funding
This research was supported by a new faculty grant from Michigan Technological University Institute of Computing and Cybersystems (PI: Weihua Zhou), a seed grant from Michigan Technological University Health Research
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Zhihui Xu and Haipeng Tang contributed equally to this work.