Gated SPECT assessment of left ventricular function is sensitive to small patient motions and to low rates of triggering errors: a comparison with equilibrium radionuclide angiography

Polarity status of trigger signal during ECG-gating affects parameters of LV function in gated myocardial perfusion SPECT

INTRODUCTION AND BACKGROUND

The polarity status is one of the important items of specifications of trigger signal from cardiac trigger monitors with two options, either positive or negative. Some systems allow the user to set the polarity of trigger signal before imaging. Efforts should be made to set the polarity status according to the recommendations provided by the manufacturers. In case of inappropriate selection, changes in computation of end-systolic and end-diastolic volumes as well as ejection fraction may occur.

OBJECTIVE

To investigate the effect of the polarity status of trigger signals in synchronization process during 8- and 16-frame gated SPECT imaging on the systolic and diastolic parameters of LV function.

METHODS

Thirty-four patients referred for a myocardial perfusion SPECT were consecutively included in the study. The rest scan for each patient was performed with 8- and 16-frame gating simultaneously with positive trigger signal set by the operator in a cardiac trigger monitor and then repeated after manual selection of negative polarity. In total, the 4 imaging modes acquired were 8-frame/positive-trigger, 16-frame/positive-trigger, 8-frame/negative-trigger, and 16-frame/negative-trigger. All SPECT images were reconstructed and processed with the same values of parameters. Systolic and diastolic indices of LV function were derived in QGS of the Cedars-Sinai software and then were compared using various statistical tests, and a reliability analysis was also performed.

RESULTS

The age of patients recruited in the study was 58.41 ± 8.94, and 16 (47.1%) males and 18 (52.9%) females. All the correlation coefficients between corresponding parameters in positive and negative trigger signals were statistically significant. The difference between the parameters of systolic function including EF, EDV, and ESV in positive and negative trigger signals was statistically significant in paired sample t test. Likewise, a statistically significant difference was also found between mean phase angle in scans with positive and negative trigger signals by a phase difference of 147.91 (41.0% of an average cardiac cycle) and 149 (41.3% of an average cardiac cycle) degrees in 8- and 16-frame gating modes, respectively. Strong agreement (according to high values of intra-class correlation coefficient) was found for all four pairs. According to Bland-Altman results, an offset of about 3 percentage units was found, both between imaging in 8-frame gating compared to 16-frame gating, higher value in favor of 16-frame gating, and also between imaging with positive polarity trigger compared to negative-polarity trigger, again higher value in favor of positive-polarity triggering.

CONCLUSION

The status of the polarity of trigger signals or similar CTM-camera delays in synchronization process during 8- and 16-frame gated SPECT imaging can be considered as one of the factors that may influence systolic and diastolic indices of LV function.

Left ventricular ejection fraction determined with the simulation of a very low-dose CZT-SPECT protocol and an additional count-calibration on planar radionuclide angiographic data

PURPOSE

To determine whether the left ventricular ejection fractions (EFs), measured on a high-sensitivity CZT single photon emission computed tomography (SPECT)-camera with a 70% reduction in recording times and a prevention of EF overestimation through an additional count-calibration, are concordant with reference EF from planar radionuclide angiography (2D-RNA).

METHODS

An additional 10-minute CZT-SPECT recording was performed in patients referred to 2D-RNA for cardiomyopathy (n = 23) or chemotherapy monitoring (n = 50) with an in vivo red blood cell labeling with 850 MBq [Formula: see text]. The EF, obtained from CZT-SPECT with 100% (SPECT100) or 30% (SPECT30) projection times and with a SPECT-count calibration on the 2D-RNA counts of corresponding cavity volumes, were compared to EF from 2D-RNA.

RESULTS

Strong and equivalent relationships were documented between the EF from 2D-RNA and the calibrated EF from SPECT100 (y = 0.89x + 6.62; R2 = 0.87) and SPECT30 (y = 0.87x + 8.40; R2 = 0.85), and the mean EF from SPECT100 (54% ± 15%) and SPECT30 (53% ± 16%) were close to that from 2D-RNA (55% ± 15%). However, upward shifts in these mean values were documented in the absence of count calibration for both SPECT100 (60% ± 18%) and SPECT30 (60% ± 18%).

CONCLUSION

Left ventricular EF may be determined on a high-sensitivity CZT-camera, a 70% reduction in injected activities, and an additional count-calibration for further enhancing the concordance with 2D-RNA values.

Primary percutaneous coronary intervention in ST-elevation myocardial infarction with an ectatic infarct-related artery

OBJECTIVE

The aim of this study was to describe the procedural characteristics, myocardial perfusion, and long-term outcomes in ST-elevation myocardial infarction patients with an ectatic infarct-related artery (IRA).

PATIENTS AND METHODS

The retrospective analysis included 1270 consecutive ST-elevation myocardial infarction patients treated by primary percutaneous coronary intervention who were categorized according to the coronary anatomy of the IRA as follows: ectatic group (n=91) and control group (n=1179).

RESULTS

Compared with the control group, patients in the ectatic group experienced lower Thombolysis in myocardial infarction grade 3 flow rate after percutaneous coronary intervention (64.8 vs. 88.2%: ectatic group vs. nonectatic group, P<0.001) and more frequent distal embolization (44.4 vs. 11.1%, P<0.001). ECG ST resolution was significantly lower in the ectatic group (P<0.001). Paradoxically, the left ventricular ejection fraction values at discharge were significantly higher in the ectatic group (P=0.032) and the infarct size assessed within 6-12 months after discharge tended to be smaller (P=0.06). The 30-day mortality rate was not significantly different between the two groups (3.3 vs. 5.0%, P=0.378) as well as Kaplan-Meier analysis for long-term overall survival in both groups (P=0.8).

CONCLUSION

Patients with ectatic IRA were characterized by discrepancies between high angiographic thrombus burden in a larger vessel and impact on left ventricular function that may influence their long-term survival.

Motion correction and myocardial perfusion SPECT using manufacturer provided software. Does it affect image interpretation?

PURPOSE

Myocardial perfusion SPECT is an excellent tool for the assessment of coronary artery disease (CAD); however, it is affected by several artifacts, such as patient motion during acquisition, which increases false-positive rates. Therefore, the purpose of this work is to analyze changes in perfusion scores after motion-correction software application.

METHODS

The population included 160 (99m)Tc-sestamibi CAD studies, divided into two groups: with and without perfusion defects, equally divided into subgroups according to movement during standard acquisition. A Siemens ECAM 180 was used for processing without correction and with automatic and manual e.soft 2.5 modalities. Visual interpretation as well as QPS software was compared using Pearson correlation and kappa agreement statistics.

RESULTS

Moderate agreement was observed between SPECT interpretations after motion correction versus the original report, according to the presence of perfusion defects. Manual correction using the software obtained the lowest agreements. Perfusion summed stress scores (SSS) correlation from different processing modalities versus non-corrected studies differed significantly independent of the degree of motion. Mean SSS in 40 patients with no motion was 3.9 + or - 3.9 when no correction was applied; with automatic correction was 8.8 + or - 10 (p = 0.03) and with manual correction was 3.1 + or - 3.5 (p = ns versus non-corrected). Automatic correction was better when applied to patients with mild to moderate motion. In those with mild or no motion, software overestimated or created new perfusion defects.

CONCLUSION

Motion-correction software must be used with caution when trying to optimize myocardial perfusion SPECT based on individual analysis. Acquisition should be always repeated in cases with severe motion and in no or mild motion it seems preferable to avoid correction.

Nitrate-enhanced gated SPECT in patients with primary angioplasty for acute myocardial infarction: evidence of a reversible and nitrate-sensitive impairment of myocardial perfusion

PURPOSE

Reperfusion of myocardial infarction (MI) leads to a reversible dysfunction of coronary vessels. We hypothesised that vasodilating drugs such as nitrates might improve sestamibi uptake within viable areas of recently reperfused MI, thereby enhancing prediction of subsequent improvements in perfusion and contractility. This study was aimed at assessing nitrate-enhanced sestamibi gated SPECT after MI reperfusion.

METHODS

Twenty-nine patients underwent rest followed by nitrate sestamibi gated SPECT at 9 +/- 3 days after primary angioplasty for acute MI and at follow-up, 4-10 months later. Four MBq/kg of (99m)Tc-sestamibi was injected at rest, and 12 MBq/kg after nitroglycerin spray.

RESULTS

Follow-up improvements were documented for both perfusion (P+) and contractility (C+) in 18% of the 180 initially abnormal segments, in neither perfusion (P-) nor contractility (C-) in 44%, in contractility only (C+P-) in 16% and in perfusion only (C-P+) in 22%. Perfusion improvement was related to lower sestamibi uptake on baseline rest SPECT (P+: 42 +/- 15% vs P-: 50 +/- 15%, p = 0.001) and, moreover, to a higher increase between rest and nitrate uptake (P+: +9.5 +/- 6.5% vs P-: +2.0 +/- 5.9%, p < 0.001). Contractility improvement was related to sestamibi uptake on baseline nitrate SPECT (C+: 58 +/- 15% vs C-: 38 +/- 16%, p < 0.001), a variable enhancing the prediction provided by sestamibi uptake at rest (p < 0.05).

CONCLUSION

The improvement in perfusion which is documented in the months following MI reperfusion is predicted by initial nitrate enhancement of sestamibi uptake, suggesting a mechanism of reversible vascular injury. In this particular setting, sestamibi uptake is a better predictor of contractility recovery when determined after nitrate administration rather than under conventional resting conditions.

Residual stress ischaemia is associated with blood markers of myocardial structural remodelling

BACKGROUND

Long-term prognosis of coronary artery disease (CAD) patients is worsened when stress ischemia persists on treatment, but the relationship with adverse cardiac remodelling had never been investigated.

AIM

To analyze changes in blood markers of fibrosis in patients with chronic CAD exhibiting exercise ischaemia.

METHODS

Circulating markers of collagen: (i) turnover (amino-terminal propeptide of collagen-III [PIIINP]) and (ii) degradation (matrix metalloproteinase 1 [MMP-1]), were obtained in 139 CAD patients referred for exercise 201Tl-SPECT.

RESULTS

In the 57 patients who had SPECT-ischaemia, PIIINP was higher (4.3+/-2.9 microg L-1 vs. 3.1+/-1.5 microg L-1, p=0.002) and MMP-1 lower (3.8+/-2.1 microg L-1 vs. 4.7+/-2.8 microg L-1, p=0.04) than in the 82 patients without SPECT-ischaemia. PIIINP was independently related to LV volume, SPECT-ischaemia and age, whereas MMP-1 was related to current treatment with ACEI and beta-blockers (p<0.05). In the 104 patients with a normal LV ejection fraction, only PIIINP was related to SPECT-ischaemia (4.1+/-2.2 microg L-1 vs. 3.1+/-1.5 microg L-1, p=0.01).

CONCLUSION

In patients with chronic CAD, exercise ischaemia is associated with increased collagen-III turnover, independently of concomitant medications and even when LV ejection fraction is normal. Long-term, this increase might relate to adverse cardiac remodelling even when cardiac function is not clearly affected at baseline.