Transient Ischemic Dilation of the Left Ventricle on SPECT: Correlation with Findings at Coronary CT Angiography

Abstract

Transient ischemic dilation (TID) in the setting of abnormal stress-rest cardiac SPECT myocardial perfusion imaging (MPI) has been linked with increased cardiovascular risk. However, the significance of TID in the setting of an otherwise normal SPECT MPI study has not been clearly established. In this study, cardiac CT was used to evaluate the prevalence of atherosclerotic lesions and the severity of coronary artery stenosis in patients with TID of the left ventricle with or without associated myocardial perfusion defects on SPECT MPI. Methods:The study population consisted of 1,553 consecutive patients who had undergone both cardiac CT and SPECT MPI within 1 mo between January 1, 2006, and September 1, 2011. Patients included in the study group had a pathologic TID value defined as ≥1.18 for men and ≥1.22 for women. Coronary CT angiography was used to evaluate each coronary segment for the presence and composition of atherosclerotic plaque and the degree of coronary stenosis. TID-positive patients were compared with a 2:1 risk-factor-matched-pair control cohort without TID. Results: TID was identified in 30 patients who were compared with TID-negative risk-factor-matched controls (n 5 60). When compared with the TID-negative control cohort, TID-positive patients had no significant differences in the presence and extent of atherosclerosis, the degree of coronary artery stenosis, or the calcium score at cardiac CT. Similarly, there were no significant differences in these CT measures in TID-positive patients with a normal perfusion study (n 5 20) when compared with TID-negative patients with a normal perfusion study (n 5 48). In addition, there was no significant difference in the incidence of major adverse cardiac events when comparing both the TID-positive patients and the TIDnegative control cohort and when comparing patients who were TID-positive with normal perfusion with patients who were TID-negative with normal perfusion. Conclusion: The presence of TID with an otherwise normal SPECT MPI study does not translate into a greater extent of coronary artery disease as assessed by cardiac CT or increased risk for future major adverse cardiac events. Tr ansient ischemic dilation (TID) on stress SPECT myocardial perfusion imaging (MPI) is defined as the apparent presence of left ventricular (LV) dilation on poststress relative to rest images. Several mechanisms for this phenomenon have been proposed, however, there is no clear consensus as to the pathophysiology resulting in the finding of TID (1-5). Previous studies have suggested that TID in the context of reversible myocardial perfusion defects is associated with increased risk of severe, extensive multivessel coronary artery disease (CAD) (1,6,7). TID in the setting of an abnormal SPECT MPI study has also been linked with increased cardiovascular risk and poor cardiovascular outcomes (8-11). However, the significance of TID in the setting of an otherwise normal SPECT MPI study has not been clearly established. It is thought that TID in the setting of an other...

Contemporary relevance of TID: Based on the company it keeps

“…Halligan et al confirmed the absence of an increase in multivessel disease in patients with TID and extended the results to include no increase in calcium score or extent of atherosclerosis as measured by cardiac CT in 1,553 consecutive patients who underwent a SPECT MPI and cardiac CT within 1 month between 2006 and 2011. (18) The incidence of MACE was also similar. There is potential selection bias in this cohort, however, as the authors could not control for parameters that drove the decision to perform cardiac CT rather than invasive coronary angiography.…”

“…Given that recent studies show no incremental benefit of TID in this population, these patients can be observed with careful follow-up. (18, 24) Patients with high-risk comorbidities such as known CAD, diabetes mellitus, or chronic kidney disease, have an intermediate risk, and TID may have benefit in this subgroup. (21) However, the majority of these patients will not have obstructive disease on angiography.…”

Reference values for left ventricular systolic synchrony according to phase analysis of ECG‐gated myocardial perfusion SPECT

“…Xu () studied a population with <5% likelihood of CAD and defined the normal limits for transient ischaemic dilatation; the upper limits were 46% for end‐systolic and 23% for end‐diastolic TID in low likelihood of patients with CAD. On the other hand, it has been showed that the presence of TID with otherwise normal SPECT perfusion imaging has benign prognosis (Halligan et al ., ) (Doukky et al ., ). Based on that, information of TID should be interpreted with caution because considerable amount of TID can be observed even without significant myocardial ischaemia.…”

Transient ischemic dilation ratio in regadenoson, single isotope gated single-photon emission computed tomography myocardial perfusion imaging

“…[123] Initial studies, with the use of exercise thallium-201, noted that the size of the left ventricle is sometime larger on the immediate poststress image than on the 4 h redistribution image; the phenomenon of which was named “TID of the left ventricle.”[1] Many patients with multivessel CAD have been found to have an abnormal TID, making this finding an easily derived and highly specific marker of multivessel critical stenosis with potential important prognostic value. [14] Several mechanisms are considered responsible for TID on nuclear images; these include subendocardial ischemia, temporary systolic dysfunction or myocardial stunning, and/or a true increase in left ventricular (LV) size.…”