Original Article
Transient ischemic dilation or transient RV visualization in patients with normal SPECT stress myocardial perfusion imaging: Correlation with CT coronary artery calcium scoring and coronary angiography

https://doi.org/10.1007/s12350-021-02704-9Get rights and content

Abstract

Background

Ancillary findings on MPI, such as transient ischemic dilation (TID) and transient right ventricular visualization (TRV), are recognized as markers of extensive CAD and predictive of adverse outcomes. They usually occur in association with stress-induced regional MPI abnormalities. However, the clinical significance of these ancillary markers in the presence of normal stress MPI is incompletely understood.

Methods

From a cohort of 564 consecutive patients referred for clinical SPECT stress MPI, 44 patients had normal stress SPECT MPI and either TID (n = 28) or TRV (n = 16). These imaging findings were correlated with CT coronary calcium (CAC), CT coronary angiography (CTA), and invasive coronary angiography (ICA) in patients with severe CAC ≥ 1000 HU. TID and TRV were quantified as stress/rest ratios. Severe CAD was defined as > 70% luminal stenosis on CTA or ICA.

Results

The median TID ratio was 1.23, with a range of 1.13–1.48; the median TRV ratio was 1.30, with a range of 1.20–1.48. Of 44 patients with TID or TRV, only 9 patients (20.5%) had severe obstructive > 70% CAD by angiography (6 of 28 patients (21.5%) with TID and 3 of 16 patients (19%) with TRV). Severe multi-vessel CAD occurred in only 2 of 44 patients (4.5%). In contrast, of 9 patients with CAC > 1000 HU, 6 (67%) had severe obstructive CAD.

Conclusion

In patients with normal stress SPECT MPI and TID or TRV, the incidence of severe obstructive CAD was relatively low and predominantly single-vessel CAD. These findings do not support the concept that TID or TRV with normal stress MPI is predictive of high-risk CAD.

Introduction

Transient ischemic dilation (TID) of the left ventricle and transient right ventricular visualization (TRV) on post-stress MPI are considered ancillary findings of stress-induced myocardial ischemia.1, 2, 3 Potential mechanisms that have been proposed for TID, are circumferential subendocardial ischemia or global myocardial ischemic stunning.4 For TRV, exercise-induced pulmonary hypertension or exercise-induced bronchospasm with increased pulmonary pressure has been hypothesized.3 Usually, these abnormal patterns are associated with stress-induced regional myocardial perfusion defects and were predictive of severe and extensive CAD and poor cardiac outcomes.1,5,6 However, the imaging patterns of TID and TRV after stress testing have also been observed in the absence of associated regional perfusion abnormalities. The latter constellation of findings has been hypothesized to be due to balanced epicardial CAD or diffuse microvascular disease, which would be associated with adverse outcomes.2,7,8 The present study aimed to investigate the clinical significance of isolated TID and TRV, without stress-induced regional perfusion abnormalities, in a prospective cohort of patients referred for stress-rest SPECT MPI, by additional CT coronary calcium scoring and angiography.

Section snippets

Methods

The study patients were prospectively selected from a cohort of 564 consecutive patients referred for clinically indicated stress-rest SPECT MPI at the Research Unit of the Farshchian Heart Center, Hamadan, Iran between 2018 and 2020. Inclusion criteria were (1) normal stress MPI and (2) quantitative transient ischemic dilation (TID) or quantitative transient right ventricular visualization (TRV) on post-stress images. Exclusion criteria were (1) known angiographic epicardial coronary artery

Results

The clinical characteristics of the 44 study patients are shown in Table 1. The clinical indication for stress MPI was chest discomfort in most patients, but typical angina occurred in only 13 patients. In patients with TID, dyspnea was the main complaint in about one half of patients. Eleven patients (25%) had a high pretest likelihood of CAD. Twenty-three patients performed treadmill exercise using the Bruce protocol, and 21 patients had dipyridamole pharmacological vasodilation stress.

Discussion

The results of our study show that the incidence of TID and TRV, in the absence of abnormal stress MPI, occurred in only 15.4% of a cohort of consecutive patients. The incidence of severe obstructive CAD (> 70% stenosis) in patients with either TID or TRV was relatively low at 20.5% and consisted chiefly of single-vessel CAD. Only 2 of 44 patients (4.5%) had severe obstructive double-vessel CAD. These findings do not support the notion that abnormal non-perfusion imaging patterns in the absence

Conclusion

Our study showed that patients with TID or TRV and no stress-induced MPI defects have a low incidence (20%) of severe obstructive CAD that consisted mainly (16%) of single-vessel CAD and few (4%) double-vessel CAD, but no left main CAD or triple-vessel CAD. The use of coronary CTA especially in the patients representing typical angina might be an effective noninvasive imaging procedure to unveil the extent of underlying atherosclerosis for optimizing patient referral to invasive angiography.

New Knowledge Gained

The non-perfusion imaging patterns of TID and TRV, in association with quantitatively normal 99m Tc-sestamibi SPECT MPI, are not predictive of a high incidence of severe obstructive multi-vessel CAD.

Acknowledgments

This article was finalized under the auspices of the ‘‘Mentorship at Distance’’ committee of the Journal of Nuclear Cardiology. We gratefully acknowledge the editorial suggestions by Professor Frans J. Th. Wackers, MD, PhD.

Disclosures

The authors declare that they have no conficts of interest and no funding was received for this study.

References (25)

The authors of this article have provided a PowerPoint file, available for download at SpringerLink, which summarizes the contents of the paper and is free for re-use at meetings and presentations. Search for the article DOI on SpringerLink.com.

View full text