Day-to-day variability of global left ventricular functional and perfusional measurements by quantitative gated SPECT using Tc-99m tetrofosmin in patients with heart failure due to coronary artery disease

Low-dose single acquisition rest (99m)Tc/stress (201)Tl myocardial perfusion SPECT protocol: phantom studies and clinical validation

PURPOSE

We developed and tested a single acquisition rest (99m)Tc-sestamibi/stress (201)Tl dual isotope protocol (SDI) with the intention of improving the clinical workflow and patient comfort of myocardial perfusion single photon emission computed tomography (SPECT).

METHODS

The technical feasibility of SDI was evaluated by a series of anthropomorphic phantom studies on a standard SPECT camera. The attenuation map was created by a moving transmission line source. Iterative reconstruction including attenuation correction, resolution recovery and Monte Carlo simulation of scatter was used for simultaneous reconstruction of dual tracer distribution. For clinical evaluation, patient studies were compared to stress (99m)Tc and rest (99m)Tc reference images acquired in a 2-day protocol. Clinical follow-up examinations like coronary angiography (CAG) and fractional flow reserve (FFR) were included in the assessment if available.

RESULTS

Phantom studies demonstrated the technical feasibility of SDI. Artificial lesions inserted in the phantom mimicking ischaemia could be clearly identified. In 51/53 patients, the image quality was adequate for clinical evaluation. For the remaining two obese patients with body mass index > 32 the injected (201)Tl dose of 74 MBq was insufficient for clinical assessment. In answer to this the (201)Tl dose was adapted for obese patients in the rest of the study. In 31 patients, SDI and (99m)Tc reference images resulted in equivalent clinical assessment. Significant differences were found in 20 patients. In 18 of these 20 patients additional examinations were available. In 15 patients the diagnosis based on the SDI images was confirmed by the results of CAG or FFR. In these patients the SDI images were more accurate than the (99m)Tc reference study. In three patients minor ischaemic lesions were detected by SDI but were not confirmed by CAG. In one of these cases this was probably caused by pronounced apical thinning. For two patients no relevant clinical follow-up information was available for evaluation.

CONCLUSION

The proposed SDI protocol has the potential to improve clinical workflow and patient comfort and suggests improved accuracy as demonstrated in the clinical feasibility study.

Fractional flow reserve and myocardial viability as assessed by SPECT perfusion scintigraphy in patients with prior myocardial infarction

BACKGROUND

In patients with previous myocardial infarction (MI), assessment of myocardial viability and physiological significance of coronary artery stenoses are essential for appropriate guidance of revascularization. The aim of the study was to evaluate the relation between fractional flow reserve (FFR) and myocardial viability as assessed by gated SPECT MIBI perfusion scintigraphy in patients with previous MI undergoing elective PCI.

METHODS

The study population consisted of 26 patients (mean age 55 ± 7 years; 21 male) with a previous MI and a significant coronary stenosis in a single infarct-related coronary vessel for which PCI was being performed. In all patients, FFR was evaluated before and immediately after PCI. SPECT imaging was done before and 3 ± 1 months after PCI. A region representing the MI was considered viable if MIBI uptake was ≥55% of the normal region. Improvement in perfusion after revascularization was considered achieved if perfusion abnormalities decreased by 5% or more and there was a decrease in segmental score of ≥1 in three segments in PCI-related vascular territory.

RESULTS

Extent of perfusion abnormalities decreased from 32 ± 16% to 27 ± 19% after PCI (P < .001). In patients with myocardial viability in comparison to patients with no viability, there was significant difference in FFR before PCI (.57 ± .14 vs .76 ± .12, P = .002), despite almost the same values of diameter stenosis of infarct-related artery (63 ± 8% vs 64 ± 3%, respectively, P = .572). In addition, FFR prior to PCI was related to improvement in perfusion abnormalities after revascularization (P = .047), as well as with peak activity of creatine-kinase measured during previous MI (r = .56, P = .005).

CONCLUSION

Lower values of FFR before angioplasty are associated with myocardial viability and functional improvement as assessed by SPECT perfusion scintigraphy.

Cardiovascular determinants and prognostic significance of CC Chemokine Ligand-18 (CCL18/PARC) in patients with stable coronary artery disease

Chemokines are important mediators of angiogenesis, hematopoiesis and leucocyte trafficking. CC Chemokine Ligand-18 (CCL18)/ pulmonary and activation-regulated chemokine (PARC) is a circulating chemokine that plays a role in injury healing, physiological homing of mononuclear blood cells and inflammatory responses. CCL18/PARC is also expressed in atherosclerotic plaques. We prospectively evaluated CCL18/PARC levels and their cardiovascular and biological determinants in a large cohort of 285 patients with stable coronary heart disease who were subsequently followed for 3 years for hard cardiac events. It was found that CCL18/PARC levels were associated with decreased cardiac function, decreased exercise capacity and increased inflammatory parameters including interleukin-6 (IL-6) and hs-CRP. More importantly high CCL18/PARC levels were an independent predictor of future cardiovascular events. Therefore, CCL18/PARC is a potential diagnostic and prognostic parameter in patients with stable coronary artery disease.

The expanding role of left ventricular functional assessment using gated myocardial perfusion SPECT: the supporting actor is stealing the scene

BACKGROUND

Gating of single-photon emission computed tomography (SPECT) has significantly improved the reliability and diagnostic accuracy of myocardial perfusion imaging. The functional parameters derived from this technique, mainly left ventricular volumes and ejection fraction, have been demonstrated to be accurate and reproducible. They are able to increase the detection of severe and extensive coronary artery disease and show a significant incremental prognostic power over perfusion abnormalities. Therefore, the importance given to gated SPECT functional data has progressively grown.

DISCUSSION

This circumstance has further expanded the indications for myocardial perfusion imaging and strengthened its position among the different imaging modalities. Moreover, several studies show that the evaluation of ventricular function may have a leading part in justifying the execution of perfusion scintigraphy in various clinical conditions.

AIM

Aim of this review is to describe this evolution of gated SPECT functional assessment from a supporting rank with respect to perfusion, to a main actor position in the field of cardiac imaging.

Intra- and interatrial asynchrony in patients with heart failure

Heart failure (HF) is associated with atrial conduction delay. Color tissue Doppler imaging was used to evaluate intra- and interatrial asynchrony in patients with HF, patients with structural heart disease without HF, and controls. Twenty-three controls (mean age 65 +/- 13 years), 29 patients with structural heart disease without HF (mean age 68 +/- 9 years), and 29 patients with HF (mean age 67 +/- 9 years) were studied. Patients had no histories of atrial fibrillation. Echocardiographic color tissue Doppler imaging of the atria was performed. Measurements below the atrioventricular plane were selected on the right atrial (RA) free wall, interatrial septum (IAS), and left atrial (LA) free wall. The time difference from the onset of the P wave to the onset of the A wave at the right atrium (P-RA), the IAS (P-IAS), and the left atrium (P-LA) was measured. Asynchrony was defined as the differences between P-IAS and P-RA (RA asynchrony), P-LA and P-IAS (LA asynchrony), and P-LA and P-RA (interatrial asynchrony). In patients with HF, a significant increase in RA asynchrony was observed compared with controls and patients without HF (30 +/- 21 vs 12 +/- 13 and 14 +/- 15 ms, p <0.001). LA asynchrony was not different (19 +/- 26 vs 25 +/- 13 vs 25 +/- 14 ms, p = NS). Interatrial asynchrony was significantly increased in patients with HF (49 +/- 24 vs 37 +/- 9 and 39 +/- 17 ms, p = 0.04). There were moderate but significant correlations of RA asynchrony with log N-terminal-pro-B-type natriuretic peptide (r = 0.3, p = 0.01) and the ejection fraction (r = -0.4, p <0.001). In conclusion, in patients with HF, significant RA and interatrial asynchrony was documented, evaluated by noninvasive color tissue Doppler imaging. Asynchrony was related to N-terminal-pro-B-type natriuretic peptide and to the ejection fraction.

Fasting blood glucose levels are related to exercise capacity in patients with coronary artery disease

BACKGROUND AND AIM

Previous studies have demonstrated reduced exercise capacity in patients with diabetes mellitus. This study evaluated the relationship between fasting blood glucose (FBG) levels and exercise capacity in patients with coronary artery disease (CAD).

METHODS

We evaluated 986 consecutive patients with CAD referred for bicycle spiroergometry combined with gated myocardial perfusion imaging. Maximum oxygen consumption (VO2max) and maximal watts were measured. Patients were divided into 4 FBG categories: < 100 mg/dL (n = 611), 100 to 109 mg/dL (n = 144), 110 to 125 mg/dL (n = 102), and > or = 126 mg/dL (n = 129). Differences in clinical characteristics, exercise hemodynamics, perfusion imaging, and univariate as well as multivariate predictors of exercise capacity were determined.

RESULTS

Maximal watts and VO2max were significantly lower (P < .0001) in patients with higher FBG levels and were related to FBG values in univariate and multivariate analyses. Left ventricular volumes and ejection fractions did not differ between the FBG categories. Myocardial perfusion imaging showed a comparable degree of ischemia in the 4 FBG groups. However, patients with higher FBG levels had higher heart rate and blood pressure values at rest resulting in a higher rate-pressure product (values in the 4 FBG groups 8299 +/- 2051, 8733 +/- 2008, 9558 +/- 2583, and 9588 +/- 2468 beat/min x mm Hg, P < .0001), suggesting increased myocardial oxygen consumption per unit time at rest.

CONCLUSION

Exercise capacity in patients with CAD is related to FBG levels. Patients with impaired fasting glucose or an FBG level > or = 126 mg/dL reached lower peak watts and lower VO2max values. This could be attributed to a higher myocardial oxygen consumption per unit time at rest and the inability to adapt their coronary flow adequately to higher metabolic demands during maximal exercise.

Relationship between QRS duration, left ventricular volumes and prevalence of nonviability in patients with coronary artery disease and severe left ventricular dysfunction

BACKGROUND

Patients with coronary artery disease (CAD), a QRS duration >or=120 ms and left ventricular ejection fraction (LVEF) <or=30% are potential candidates for cardiac resynchronization therapy (CRT). Our aim was to investigate the relationship between QRS duration, left ventricular volumes and prevalence of nonviable tissue in this patient population.

METHODS

We studied 132 patients (118 men, age 68+/-5 years) with CAD and LVEF <or=30% (mean LVEF 24+/-6%). LV volumes and myocardial viability were determined by gated myocardial perfusion imaging.

RESULTS

A QRS duration >or=120 ms was present in 91 patients (69%). Although there were no differences in LVEF, patients with longer QRS durations had significant larger end-diastolic and end-systolic volumes (p<0.01). Substantial nonviable tissue in the inferior or lateral wall was present in 29% of patients with a QRS duration >or=120 ms versus 7% of those with a QRS duration <120 ms (p<0.01).

CONCLUSIONS

An increased QRS duration is associated with more advanced remodeling in patients with CAD and poor LV function. Almost one third of these patients with a prolonged QRS duration have no viable tissue in the inferolateral wall, an area that is usually stimulated with CRT.

Incremental prognostic value of combined perfusion and function assessment during myocardial gated SPECT in patients aged 75 years or older

BACKGROUND

Perfusion and functional data obtained during gated single photon emission computed tomography (SPECT) have proven prognostic value in the middle-aged patient population. The aim of this study was to investigate whether perfusion and functional cardiac gated SPECT data have prognostic value in patients aged 75 years or older.

METHODS AND RESULTS

We studied clinical and gated SPECT predictors of cardiac and all-cause death in 294 patients aged 75 years or older with known or suspected coronary artery disease who were referred for tetrofosmin cardiac gated SPECT imaging. Summed perfusion scores were calculated in a 17-segment model by use of commercially available software (4D-MSPECT). Left ventricular functional data were calculated by use of QGS gated SPECT software. The median age of the study population was 78 years (range, 75-91 years). There were 160 men (54%) and 134 women (46%). During a median follow-up of 25.9 months (range, 1.8-36 months), 47 patients (16%) died (27 cardiac deaths). In a multivariate Cox proportional hazards regression analysis, the summed rest score (chi2 gain = 8.0, P = .009), transient ischemic dilatation index (chi2 gain = 6.3, P = .012), and resting left ventricular ejection fraction (chi2 gain = 7.0, P = .030) were independent predictors of all-cause death. The summed rest score (chi2 gain = 8.2, P = .004) and resting end-systolic volume (chi2 gain = 13.7, P = .005) were independent predictors of cardiac death.

CONCLUSIONS

This study showed that gated SPECT left ventricular functional data assessed during myocardial gated SPECT provide independent and incremental information above clinical and perfusion SPECT data for the prediction of cardiac and all-cause death in patients aged 75 years or older referred for myocardial SPECT imaging.

Assessment of left ventricular function and volumes for patients with dilated cardiomyopathy using gated myocardial perfusion SPECT and comparison with echocardiography

AIM

Left ventricular function, volumes and regional wall motion provide valuable diagnostic information and are of long-term prognostic importance in patients with dilated cardiomyopathy (DCM). This study was designed to compare the effectiveness of two-dimensional echocardiography and gated single photon emission computed tomography (SPECT) to evaluate these parameters in patients with DCM.

METHODS

Gated SPECT and two-dimensional echocardiography were performed in 45 patients with DCM, and in 10 normal subjects as the control group. Patients were divided into two groups according to the aetiology of DCM: group I, ischaemic DCM (n=30); group II, non-ischaemic DCM (n=15). All patients and the control group underwent resting myocardial gated SPECT, 45 min after injection of 555 MBq of Tc-methoxyisobutyl-isonitrile (Tc-MIBI). Gated SPECT data, including left ventricular volumes and left ventricular ejection fraction (LVEF), were processed using an automated algorithm. Simpson's method was used to evaluate these parameters. Regional wall motion was evaluated using both modalities and scored using a 16-segment model with a five-point scoring system. Perfusion defects were expressed as a percentage of the whole myocardium planimetered by a bull's-eye polar map of composite non-gated SPECT. Myocardial perfusion was scored using a 16-segment model with a four-point scoring system.

RESULTS

Mean perfusion defects and perfusion defect scores were 25+/-13% and 1.12+/-0.36 in group I and 4+/-8% and 0.76+/-0.26 in group II (P<0.01). The overall agreement between the two imaging modalities for the assessment of regional wall motion was 57% (403/720 segments: 269/480 segments in group I and 134/240 segments in group II). With gated SPECT, LVEF was 27+/-9%, the end-diastolic volume (EDV) was 212+/-71 ml and the end-systolic volume (ESV) was 160+/-67 ml. With echocardiography, these values were 29+/-8%, 197+/-56 ml and 139+/-47 ml, respectively. The correlation between gated SPECT and two-dimensional echocardiography was good (r=0.72, P<0.01) for the assessment of LVEF. The correlation was also good for EDV and ESV, but with wider limits of agreement (r= 0.71, P<0.01 and r=0.71, P<0.01, respectively) and with significantly higher values with gated SPECT (P<0.01). For patients with a perfusion defect of <20% or low myocardial perfusion scores, a higher correlation was found between the two methods for the assessment of LVEF, EDV and ESV. On the other hand, the correlation was lower for the assessment of wall motion.

CONCLUSIONS

Gated SPECT and two-dimensional echocardiography correlate well for the assessment of left ventricular function and volumes. Gated SPECT has the advantage of providing information about left ventricular function, dimensions and perfusion.

Repeatability of left ventricular ejection fraction and volume measurement for 99mTc-tetrofosmin gated single photon emission computed tomography (SPECT)

OBJECTIVES

This study was carried out to assess the repeatability of left ventricular ejection fraction (EF) and volume values obtained using Cedars-Sinai quantitative gated single photon emission computed tomography (SPECT) (QGS) software and relatively low doses of 400-600 MBq of 99mTc-tetrofosmin.

METHODS

Repeatability was assessed in a group of 75 patients, with both normal and reduced EF, who underwent repeat 99mTc-tetrofosmin gated SPECT studies and showed no clinical change in cardiac status. Gated SPECT data were acquired 1 h after injection at rest of 400-600 MBq of 99mTc-tetrofosmin. The standard patient dose was 400 MBq; however, some patients with a weight of >90 kg were given increased doses up to a maximum of 600 MBq.

RESULTS

There was good correlation of EF and volumes between the first and repeat measurements, and no significant difference between the mean EF and volumes for both the initial and repeat measurements. Background-corrected counts in the left ventricle were calculated and patients were divided into two groups: one with low counts and one with high counts. The mean difference in EF between the first and repeat measurements was significantly higher for patients in the low count group compared with those in the high count group, but there was no significant change in volume. Similarly, the mean sequential difference in EF was significantly higher for patients with normal EF, but there was no significant difference in volume.

CONCLUSIONS

We have demonstrated that EF measured using 99mTc-tetrofosmin gated SPECT is repeatable, particularly for patients with low EF, provided that adequate left ventricular counts are obtained. This will require doses greater than 400 MBq in larger patients. Ventricular volumes calculated using QGS may not be sufficiently repeatable for clinical use.