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Retrospective Cardiac Gating with A Prototype Small-Animal X-ray Computed Tomograph
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Relationship between transient ischemic dilatation and changes in heart rate during gated SPECT acquisition in a
Fernando Mut1, María P Gaudiano, Miguel Kapitán
1Nuclear Medicine Service, Italian Hospital, Montevideo, Uruguay.
Insights
Transient ischemic dilatation (TID) in myocardial perfusion SPECT can be influenced by heart rate differences (HRD). Caution is advised when interpreting TID without perfusion defects if HRD is 10 BPM or higher.
Area of Science:
- Cardiology
- Nuclear Medicine
- Medical Imaging
Background:
- Transient ischemic dilatation (TID) on myocardial perfusion SPECT is a known poor prognostic marker.
- Apparent TID may result from heart rate (HR) variations during imaging acquisition.
- Investigating the link between HR and TID in low-risk patients is crucial.
Purpose of the Study:
- To assess the correlation between transient dilatation and heart rate differences (HRD) in patients without perfusion defects.
- To determine if HRD influences the interpretation of TID in myocardial perfusion SPECT.
- To evaluate TID in relation to ventricular volumes at different heart rates.
Main Methods:
- Retrospective analysis of 99mTc-MIBI SPECT studies using a 2-day protocol.
- Recorded median HR during acquisition and HRD between rest and post-stress phases.
- Calculated TID using medium ventricular volume (TIDMV), end-diastolic volume (TIDEDV), and end-systolic volume (TIDESV), including patients with TIDMV ≥1.2.
Main Results:
- 63 low-risk patients (mean age 63.8 years) met inclusion criteria.
- A positive correlation was found between HRD and TIDMV (r=0.51, P<0.001) and TIDEDV (r=0.5, P<0.001).
- Correlation was stronger with HRD ≥10 BPM (r=0.67, P<0.001), but not significant for TIDESV (r=0.23, P=0.07).
Conclusions:
- Transient ischemic dilatation (TID) in myocardial perfusion SPECT without perfusion defects warrants cautious interpretation.
- Significant heart rate differences (HRD) ≥10 BPM during post-stress acquisition can contribute to apparent TID.
- HRD is a significant factor to consider when evaluating TID in low-risk patient populations.
Objectives:
Transient ischemic dilatation (TID) in myocardial perfusion single photon emission computed tomography (SPECT) is considered a marker of poor prognosis. However, it has been suggested that some cases are due to apparent volumetric changes secondary to differences in heart rate (HR) at the time of acquisition. We assessed the correlation between transient dilatation and HR in low risk patients with no perfusion defects.
Methods:
We retrospectively analyzed patients sent for 99mTc-MIBI SPECT using a 2-day protocol. We recorded the median HR during acquisition and the HR difference (HRD) between the rest and post-stress. We obtained the medium ventricular volume, end-diastolic volume (EDV), and end-systolic volume (ESV). We included patients in which TID using medium ventricular volume (TIDMV) was ≥1.2. TID was also calculated for the EDV and ESV (TIDEDV, TIDESV). We excluded patients with known coronary artery disease, perfusion defects, various ECG disorders, positive stress test, or ESV < 10 ml.
Results:
From a total of 2006 patients, 63 (50 exercise, 13 dipyridamole) met the criteria for analysis (age 63.8 ± 9.7, 44 men). TIDMV was 1.29 ± 0.09 and HRD 9.8 beats per minute (BPM) (range -10 to 41). There was positive correlation between HRD and TIDMV ( r = 0.51, P < 0.001) and TIDEDV ( r = 0.5, P < 0.001), but not TIDESV ( r = 0.23, P = 0.07). Correlation was stronger when HRD was ≥10 BPM ( r = 0.67, P < 0.001).
Conclusion:
TID without perfusion defects should be interpreted with caution in the presence of HRD ≥ 10 BPM during post-stress acquisition.
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