Automatic calculation of myocardial external efficiency using a single <Superscript>11</Superscript>C-acetate PET scan

Background

Myocardial external efficiency (MEE) is defined as the ratio of kinetic energy associated with cardiac work [forward cardiac output (FCO)*mean systemic pressure] and the chemical energy from oxygen consumed (MVO₂) by the left ventricular mass (LVM). We developed a fully automated method for estimating MEE based on a single ¹¹C-acetate PET scan without ECG-gating.

Methods and Results

Ten healthy controls, 34 patients with aortic valve stenosis (AVS), and 20 patients with mitral valve regurgitation (MVR) were recruited in a dual-center study. MVO₂ was calculated using washout of ¹¹C -acetate activity. FCO and LVM were calculated automatically using dynamic PET and parametric image formation. FCO and LVM were also obtained using cardiac magnetic resonance (CMR) in all subjects. The correlation between MEE_PET-CMR and MEE_PET was high (r = 0.85, P < 0.001) without significant bias. MEE_PET was 23.6 ± 4.2% for controls and was lowered in AVS (17.2 ± 4.3%, P < 0.001) and in MVR (18.0 ± 5.2%, P = 0.004). MEE_PET was strongly associated with both NYHA class (P < 0.001) and the magnitude of valvular dysfunction (mean aortic gradient: P < 0.001, regurgitant fraction: P = 0.009).

Conclusion

A single ¹¹C-acetate PET yields accurate and automated MEE results on different scanners. MEE might provide an unbiased measurement of the phenotypic response to valvular disease.

     

Attenuated right ventricular energetics evaluated using 11C-acetate PET in patients with pulmonary hypertension

Purpose

The right ventricle (RV) has a high capacity to adapt to pressure or volume overload before failing. However, the mechanisms of RV adaptation, in particular RV energetics, in patients with pulmonary hypertension (PH) are still not well understood. We aimed to evaluate RV energetics including RV oxidative metabolism, power and efficiency to adapt to increasing pressure overload in patients with PH using ¹¹C-acetate PET.

Methods

In this prospective study, 27 patients with WHO functional class II/III PH (mean pulmonary arterial pressure 39.8?±?13.5 mmHg) and 9 healthy individuals underwent ¹¹C-acetate PET. ¹¹C-acetate PET was used to simultaneously measure oxidative metabolism (k _mono) for the left ventricle (LV) and RV. LV and RV efficiency were also calculated.

Results

The RV ejection fraction in PH patients was lower than in controls (p?=?0.0054). There was no statistically significant difference in LV k _mono (p?=?0.09). In contrast, PH patients showed higher RV k _mono than did controls (0.050?±?0.009 min^?1 vs. 0.030?±?0.006 min^?1, p?<?0.0001). PH patients exhibited significantly increased RV power (p?<?0.001) and hence increased RV efficiency compared to controls (0.40?±?0.14 vs. 0.017?±?0.12 mmHg·mL·min/g, p?=?0.001).

Conclusion

The RV oxidative metabolic rate was increased in patients with PH. Patients with WHO functional class II/III PH also had increased RV power and efficiency. These findings may indicate a myocardial energetics adaptation response to increasing pulmonary arterial pressure.     

Repeatable and reproducible measurements of myocardial oxidative metabolism,blood flow and external efficiency using <Superscript>11</Superscript>C-acetate PET

Background

Non-invasive approaches to investigate myocardial efficiency can help track the progression of heart failure (HF). This study evaluates the repeatability and reproducibility of ¹¹C-acetate positron emission tomography (PET) imaging of oxidative metabolism.

Methods and results

Dynamic ¹¹C-acetate PET scans were performed at baseline and followup (47 ± 22 days apart) in 20 patients with stable HF with reduced ejection fraction. Two observers blinded to patients’ clinical data used FlowQuant^® to evaluate test–retest repeatability, as well as intra- and inter-observer reproducibility of ¹¹C-acetate tracer uptake and clearance rates, for the measurement of myocardial oxygen consumption (MVO₂), myocardial external efficiency (MEE), work metabolic index (WMI), and myocardial blood flow. Reproducibility and repeatability were evaluated using intra-class-correlation (ICC) and Bland–Altman coefficient-of-repeatability (CR). Test–retest correlations and repeatability were better for MEE and WMI compared to MVO₂. All intra- and inter-observer correlations were excellent (ICC = 0.95-0.99) and the reproducibility values (CR = 3%-6%) were significantly lower than the test–retest repeatability values (22%-54%, P < 0.001). Repeatability was improved for all parameters using a newer PET–computed tomography (CT) scanner compared to older PET-only instrumentation.

Conclusion

¹¹C-acetate PET measurements of WMI and MEE exhibited excellent test–retest repeatability and operator reproducibility. Newer PET–CT scanners may be preferred for longitudinal tracking of cardiac efficiency.

     

Reverse blood flow-glucose metabolism mismatch indicates preserved oxygen metabolism in patients with revascularised myocardial infarction

Purpose

Positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (FDG) has been reported to be unreliable for identifying viable myocardium in acute myocardial infarction (AMI), especially in areas with discordance in myocardial blood flow (MBF) and glucose metabolism. In myocardium with decreased FDG uptake but preserved MBF, referred to as exhibiting reverse mismatch, myocardial viability remains controversial and little is known about the metabolic state. The aims of this study were to clarify substrate use and to estimate myocardial viability in infarct areas exhibiting reverse mismatch.

Methods

Eighteen AMI patients with successful revascularisation were included in this study. Two weeks after onset, ¹¹C-acetate and ¹⁸F-FDG PET were performed to evaluate regional oxygen consumption (k _mono), MBF and glucose metabolism. Free fatty acid (FFA) metabolism was evaluated with ¹²³I-15-(p-iodophenyl)-3-(R, S)-methylpentadecanoic acid (BMIPP) single photon emission computed tomography (SPECT). To assess wall motion, movement in left ventricular endocardial surface was calculated using ECG-gated ^99mTc-tetrofosmin SPECT.

Results

The %k _mono values in reverse mismatch segments (52.6?±?13.6 %) were not significantly different from those in non-infarct segments (60.4?±?12.8 %, p?=?0.071) and normal match segments (preserved MBF and FDG uptake) (58.6?±?11.6 %, p?=?0.396), although regional wall motion was more severely impaired (3.06?±?2.52 mm vs 6.78?±?3.17 mm, p?<?0.0001, and vs 5.30?±?2.33 mm, p?=?0.042, respectively). Compared to segments with reduced match (reduced MBF and FDG uptake), %k _mono and %BMIPP uptake were significantly higher in reverse mismatch segments (52.6?±?13.6 % vs 37.4?±?8.9 %, p?=?0.0002, and 58.8?±?10.6 % vs 40.2?±?10.7 %, p?<?0.0001).

Conclusion

Reverse mismatch in reperfused AMI patients, high oxygen consumption and FFA metabolism were observed despite decreased glucose metabolism. We conclude that reverse mismatch indicated the myocardium with early restoration of MBF and aerobic FFA metabolism.     

Left ventricular mass from gated SPECT myocardial perfusion imaging: Comparison with cardiac computed tomography

Background

Increased left ventricular mass (LVM) has been correlated with adverse cardiac events, such as sudden cardiac death. However, LVM quantitation with widely utilized gated SPECT myocardial perfusion imaging (MPI) software, has little validation and clinical application. Thus, we compared LVM from two commonly employed gated SPECT packages [4D-MSPECT^® (4DM) and Quantitative Perfusion SPECT^® (QPS)] with the 3-dimensional reference standard, CT angiography (CTA).

Methods

Comparisons were made in 56 patients (mean age 61.4 ± 14.6; 32% female) referred for dual-isotope or low-dose/high-dose Tc-99m-tetrofosmin rest/stress MPI and cardiac CTA (mean 1.5 ±4.5 months apart). LVM measurement was performed for both CTA and MPI by two independent observers blinded to clinical information.

Results

Correlation with CTA was best for post-stress MPI than at rest; thus, post-stress values are reported. Values obtained with each of the techniques were very highly reproducible (interobserver correlation r = 0.99 for each technique). The mean LVM values were 142 g by CTA, 145 g by 4DM, and 135 g by QPS (P = NS for CTA vs SPECT, but P < .001 for 4DM vs QPS). There was moderately good correlation between CTA and SPECT LVM data (r = 0.74 and 0.72 for 4DM and QPS, respectively; both P < .001). However, on Bland-Altman analysis there was significant overestimation of lower values and underestimation of higher CT LVM values by both QPS and 4DM (both r = 0.68 and 0.69, P < .001). The limits of agreement relative to CT LVM were wide (?52.1 g to 64.1 g for QPS; and ?60.0 g to 53.5 g for 4DM).

Conclusions

SPECT and CTA give reproducible measures of LVM. Using CTA as the reference standard, the mean SPECT LVM values are similar, but lower values are overestimated and higher values are underestimated. Thus, the SPECT values are not substitutable for CTA without mathematical correction.     

Myocardial oxidative metabolism is increased due to haemodynamic overload in patients with aortic valve stenosis: assessment using 11C-acetate positron emission tomography

Purpose

The relationship between myocardial oxidative metabolism and pressure overload in aortic valve stenosis (AS) is not fully elucidated. We identified the determinants of myocardial oxidative metabolism by measuring its changes after aortic valve replacement (AVR) in patients with AS.

Methods

Myocardial ¹¹C-acetate clearance rate constant (Kmono), an index of oxidative metabolism, was measured non-invasively by using positron emission tomography in 16 patients with moderate to severe AS and 7 healthy controls. The severity of AS was assessed by echocardiography. Of 16 patients, 5 were reexamined at 1 month after AVR.

Results

Kmono was significantly higher in patients with AS than healthy controls by 42% (0.068?±?0.014 vs 0.048?±?0.007/min, p?<?0.01). Kmono was significantly correlated with age (r?=?0.58, p?<?0.01), left ventricular (LV) mass index (r?=?0.61, p?<?0.01) and estimated systolic LV pressure (r?=?0.81, p?<?0.001) measured by echocardiography. By multivariate analysis, estimated LV systolic pressure was an independent predictor of Kmono (β?=?0.93, p?<?0.01). After AVR, Kmono (from 0.075?±?0.012 to 0.061?±?0.014/min, p?=?0.043) and LV mass index (from 183?±?49 to 124?±?41 g/ml², p?=?0.043) were significantly decreased despite no significant changes in rate-pressure product.

Conclusion

Myocardial oxygen metabolism was increased in patients with AS, which was decreased after AVR. The increased myocardial oxidative metabolism in AS was largely attributable to the pressure overload of the LV.     

The effects of dobutamine stress on cardiac mechanical synchrony determined by phase analysis of gated SPECT myocardial perfusion imaging in a canine model

Background

Precise identification of left ventricular (LV) systolic mechanical dyssynchrony may be useful in optimizing the response to cardiac resynchronization therapy in heart failure (HF) patients. However, LV dyssynchrony is mostly measured at rest; patients often suffer from the HF symptoms during exercise.

Objectives

Our objective was to examine the impacts of stress on LV synchronism with phase analysis of gated SPECT myocardial perfusion imaging (GMPS) within a normal animal cohort.

Methods

Stress was induced with different levels of dobutamine infusion in six healthy canine subjects. Hemodynamic properties were assessed by LV pressure measurements. Also, LV mechanical synchronism (coordination of LV septal and lateral wall at the time of contraction) was determined by phase analysis of GMPS using commercially available QGS software and in-house MHI₄MPI software, with the thickening- and displacement-based method. Synchrony indexes in MHI₄MPI included the septal-to-lateral delay and homogeneity index, derived from each of the two methods. Also, bandwidth, SD, and entropy (synchrony indexes) of the QGS software were assessed.

Results

LVEF increased from 36.7% ± 8.7% at rest to 53.67% ± 12.34% at 20 μg·kg^?1·minute^?1 (P < .001). Also, cardiac output increased from 3.67 ± 1.0 L·minute^?1 at rest to 8.4 ± 2.6 L·minute^?1 at 10 μg·kg^?1·minute^?1 (P < .001). The same trend was observed for dP/dt _max which increased from 1,247 ± 382.7 at rest to 5,062 ± 1,800 mm Hg·s^?1 at 10 μg·kg^?1·minute^?1 (P < .01). Entropy decreased from 55.2% ± 8% at baseline to 43.5% ± 8.5% at 5 and 43.0% ± 3.7% at 10 μg·kg^?1·minute^?1 dobutamine (P < .01). Thickening homogeneity index showed a difference from 91.7% ± 5.53% at rest to 98.2% ± 0.75% at 20 μg·kg^?1·minute^?1 (P < .05).

Conclusions

Dobutamine stimulation could amplify the ventricular synchronism, and the thickening-based approach is more accurate than wall displacement for assessment of mechanical dyssynchrony in GMPS.     

Myocardial 123I-MIBG scintigraphy predicts an impairment in myocardial functional reserve during dobutamine stress in patients with idiopathic dilated cardiomyopathy

Purpose

We investigated whether myocardial ¹²³I-metaiodobenzylguanidine (¹²³I-MIBG) scintigraphy predicts impairment of myocardial functional reserve in response to dobutamine stress in patients with idiopathic dilated cardiomyopathy (DCM).

Methods

Forty DCM patients (LVEF 39?±?12 %) underwent myocardial ¹²³I-MIBG scintigraphy, echocardiography, and cardiac catheterization. Myocardial ¹²³I-MIBG uptake was quantified as the delayed heart to mediastinum (H/M) ratio and washout rate (WR). Local denervation was evaluated on polar map images. LV dP/dt _max and T_1/2 were determined from left ventricular pressure curves at baseline and during dobutamine infusion (15 μg/kg?/min). Patients were classified into two groups as follows: group A comprised 21 patients showing a delayed H/M ratio of <1.9 (median value); group B comprised 19 patients showing a delayed H/M ratio of ≥1.9.

Results

The percentage change in heart rate (%HR), LV dP/dt _max (%LV dP/dt _max), and T _1/2 (%T _1/2) from baseline to dobutamine stress were significantly more reduced in group A than in group B (39.3?±?20.2 %, 55.2?±?24.1 %, p?<?0.01; 102.3?±?46.3 %, 152.0?±?72.3 %, p?<?0.05; 38.7?±?15.3 %, 46.9?±?15.4 %, p?<?0.05, respectively). No significant differences between the two groups were observed in the echocardiographic parameters or baseline cardiac catheterization parameters. Significant correlations were found between delayed H/M ratio and %HR (r?=?0.35, p?<?0.05), %LV dP/dt _max (r?=?0.45, p?<?0.05) and %T _1/2 (r?=?0.34, p?<?0.05). Significant inverse correlations were also found between WR and %HR (r?=??0.37, p?<?0.05), %LV dP/dt _max (r?=??0.60, p?<?0.0001), and %T _1/2 (r?=??0.34, p?<?0.05). SPECT images revealed enhanced denervation from the inferoposterior to anterior wall in accordance with the advancement of global denervation.

Conclusion

Reduced ¹²³I-MIBG uptake and increased washout were related to impairment in adrenergic myocardial functional reserve in idiopathic DCM.     

Heterogeneity of longitudinal and circumferential contraction in relation to late gadolinium enhancement in hypertrophic cardiomyopathy patients with preserved left ventricular ejection fraction

Purpose

To evaluate heterogeneity of myocardial contraction in relation to extensive late gadolinium enhancement (LGE) in hypertrophic cardiomyopathy (HCM) patients with preserved left ventricular ejection fraction, using fast strain-encoded magnetic resonance imaging.

Materials and methods

Twenty-two HCM patients and 24 age-matched control subjects were included in this retrospective study. The regional and global peak values of longitudinal and circumferential strain (LS_regional, LS_global, CS_regional, CS_global), and their regional heterogeneities were evaluated using coefficients of variation (LS_CoV, CS_CoV) in relation to LGE. Receiver operating characteristic curve analysis was performed to identify patients with a total left ventricular myocardial LGE ≥ 15%.

Results

LS_global in HCM patients was significantly decreased compared to that in controls (? 14.4 ± 2.4% vs ? 17.2 ± 2.0%; p = 0.0004), while CS_global was not (p = 1.0). Negative LGE segments demonstrated decreased LS_regional in HCM patients compared to in controls (p < 0.0001), while CS_regional was not decreased. CS_CoV demonstrated the largest area under the curve (AUC) (0.91), with high sensitivity (83%) and specificity (94%) for detection of HCM patients with extensive LGE, while the AUC of LS_CoV was low (0.49).

Conclusion

The heterogeneity in CS_regional has a high diagnostic value for detection of HCM patients with extensive LGE.

     

Multiple antiplatelet therapy contributes to the reversible high signal spots on diffusion-weighted imaging in elective coiling of unruptured cerebral aneurysm

Introduction

Our aim was to systematically investigate radiographic characteristics and outcome of diffusion-weighted imaging (DWI) changes in the elective coiling of unruptured cerebral aneurysm with analyzing the correlation of antiplatelet therapy (APT).

Methods

In a total of 34 consecutive patients with unruptured cerebral aneurysms initially treated by coiling without stent assist, 26 (76.5 %) had DWI changes with 91 high signal spots within 24–48 h after the procedure. We recorded DWI parameters (location, volume, mean, and minimum values of the apparent diffusion coefficient: expressed as ADC_AVE and ADC_MIN) for each lesion, and evaluated its radiographic outcome on conventional MRI at follow-up (interval, 58.4?±?37.2 days) in the modes of APT.

Results

All patients with DWI high spots had no clinical symptoms. There was a strong correlation between ADC_AVE and ADC_MIN (r?=?0.82, p?<?0.0001). The mean ADC_AVE and rADC_AVE were 0.74?±?0.14?×?10^?3?mm²/s and 87?±?10 %. DWI high spots were small with a mean volume of 0.13?±?0.12 cm³, ranging from 0.04 to 0.86 cm³. A negative correlation was observed between the volume and values of ADC_AVE (r?=??0.48, p?<?0.0001). The DWI volume was significantly larger in single APT than in multiple (0.15?±?0.14 versus 0.10?±?0.07 cm³, p?=?0.0091). The permanent signal change was more observed in single APT than in multiple (24.5 % versus 5.2 %, p?=?0.02).

Conclusion

DWI high spots after elective coiling were small without significant decrease of ADC, and do not correspond to brain infarction. Periprocedural use of multiple antiplatelet agents is expected to reduce the volume of thromboembolism and permanent tissue damages.     

MRI differentiation of cardiomyopathy showing left ventricular hypertrophy and heart failure: differentiation between cardiac amyloidosis, hypertrophic cardiomyopathy, and hypertensive heart disease

Purpose

To evaluate the capability of MRI to differentiate cardiac amyloidosis (CA), end-stage hypertrophic cardiomyopathy (HCM), and hypertensive heart disease (HHD), which are important etiologies of left ventricular hypertrophy (LVH) and heart failure.

Materials and methods

We enrolled 26 patients presenting with both LVH and heart failure: six with CA, nine with end-stage HCM, and 11 with HHD. Cardiac function, presence of pericardial or pleural effusion, and the extent and patterns of late gadolinium enhancement (LGE) were compared among the three diseases.

Results

Myocardial LGE was observed in all six CA patients, eight end-stage HCM patients, and six HHD patients. The number of LGE segments was significantly greater in CA than in HCM or HHD (p = 0.02 for both), and all patients with CA showed a global endocardial pattern of LGE. There were significant differences among CA, HCM, and HHD in ejection fraction and end-diastolic and end-systolic volume indices (p < 0.05 for all). Pericardial effusion was observed more frequently in CA than in HCM or HHD (p = 0.04 or 0.01, respectively).

Conclusion

MRI is valuable for distinguishing among CA, end-stage HCM, and HHD, all of which present with LVH and heart failure.     

1,25-Dihydroxy vitamin D and coronary microvascular function

Purpose

The active form of vitamin D (1,25(OH)₂D) contributes to blood flow regulation in skeletal muscle. The aim of the present study was to determine whether this hormone also modulates coronary physiology, and thus whether abnormalities in its bioavailability contribute to excess cardiovascular risk in patients with disorders of mineral metabolism.

Methods

As a clinical model of the wide variability in 1,25(OH)₂D bioavailability, we studied 23 patients (62 ± 8 years) with suspected primary hyperparathyroidism referred for myocardial perfusion imaging because of atypical chest pain and at least one cardiovascular risk factor. Dipyridamole and baseline myocardial blood flow indexes were assessed on G-SPECT imaging of ^99mTc-tetrofosmin, with normalization of the myocardial count rate to the corresponding first-transit counts in the pulmonary artery. Coronary flow reserve (CFR) was defined as the ratio between dipyridamole and baseline myocardial blood flow indexes. In all patients, parathyroid hormone, 25-hydroxy vitamin D (25(OH)D) and 1,25(OH)₂D serum levels were determined.

Results

Primary hyperparathyroidism was eventually diagnosed in 15 of the 23 patients. The mean 25(OH)D concentration was relatively low (21 ± 10 ng/mL) while the concentrations of 1,25(OH)₂D varied widely but within the normal range (mean 95 ± 61 pmol/L). No patient showed reversible perfusion defects on G-SPECT. CFR was not correlated with either the serum concentration of 25(OH)D nor that of parathyroid hormone, but was strictly correlated with the serum level of 1,25(OH)₂D (R = 0.8, p < 0.01). Moreover, patients with a 1,25(OH)₂D concentration below the median value (86 pmol/L) had markedly lower CFR than the other patients (1.48 ± 0.40 vs. 2.51 ± 0.63, respectively; p < 0.001).

Conclusion

Bioavailable 1,25(OH)₂D modulates coronary microvascular function. This effect might contribute to the high cardiovascular risk of conditions characterized by chronic reduction in bioavailability of this hormone.     

Evaluation of chronic ischemic heart disease with myocardial perfusion and regional contraction analysis by contrast-enhanced 256-MSCT

Purpose

To investigate myocardial viability in chronic ischemic heart disease by myocardial perfusion and regional contraction analysis using 256-slice MSCT coronary angiography (CCTA).

Methods

In 30 patients with prior myocardial infarction (MI), CCTA with retrospective ECG-gating and stress-redistribution thallium-201 SPECT were performed. Using the same raw data as used for CCTA, myocardial perfusion imaging (CT-MPI) was reconstructed at four phases during the cardiac cycle. Mean myocardial attenuation and wall thickness at end-systole and end-diastole were measured in the MI areas depicted by SPECT, and they were compared between viable and non-viable segments categorized by SPECT.

Results

End-systolic thickness was significantly greater for viable than for non-viable segments (12.0 ± 3.2 vs. 9.6 ± 3.5 mm, p = 0.0017). There was no difference in end-diastolic thickness. Myocardial attenuation was significantly higher for viable than for non-viable segments in the subendocardium (62 ± 13 vs. 70 ± 11 HU, p = 0.003) and the epicardium (65 ± 13 vs. 80 ± 15 HU, p = 0.0002).

Conclusion

The systolic wall thinning and epicardial low-attenuation areas were the indicative findings of CT-MPI for non-viable segments in the prior MI.     

Blood flow, flow reserve, and glucose utilization in viable and nonviable myocardium in patients with ischemic cardiomyopathy

Purpose

The aim of the study was to determine whether glucose uptake in viable myocardium of ischemic cardiomyopathy patients depends on rest myocardial blood flow (MBF) and the residual myocardial flow reserve (MFR).

Methods

Thirty-six patients with ischemic cardiomyopathy (left ventricular ejection fraction 25?±?10 %) were studied with ¹³N-ammonia and ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET). Twenty age-matched normals served as controls. Regional MBF was determined at rest and during dipyridamole hyperemia and regional FDG extraction was estimated from regional FDG to ¹³N-ammonia activity ratios.

Results

Rest MBF was reduced in viable (0.42?±?0.18 ml/min per g) and nonviable regions (0.32?±?0.09 ml/min per g) relative to remote regions (0.68?±?0.23 ml/min per g, p?<?0.001) and to normals (0.63?±?0.13 ml/min per g). Dipyridamole raised MBFs in controls, remote, viable, and nonviable regions. MBFs at rest (p?<?0.05) and stress (p?<?0.05) in viable regions were significantly higher than that in nonviable regions, while MFRs did not differ significantly (p?>?0.05). Compared to MFR in remote myocardium, MFRs in viable regions were similar (1.39?±?0.56 vs 1.70?±?0.45, p?>?0.05) but were significantly lower in nonviable regions (1.23?±?0.43, p?<?0.001). Moreover, the FDG and thus glucose extraction was higher in viable than in remote (1.40?±?0.14 vs 0.90?±?0.20, p?<?0.001) and in nonviable regions (1.13?±?0.21, p?<?0.001). The extraction of FDG in viable regions was independent of rest MBF but correlated inversely with MFRs (r?=?0.424, p?<?0.05). No correlation between the FDG extraction and MFR was observed in nonviable regions.

Conclusion

As in the animal model, decreasing MFRs in viable myocardium are associated with increasing glucose extraction that likely reflects a metabolic adaptation of remodeling hibernating myocytes.     

Usefulness of gated SPECT myocardial imaging in evaluation of patients with inferior myocardial infarction

Objective

Gated single photon emission computed tomography (gated SPECT) myocardial imaging gives useful information about the extent and severity of perfusion abnormalities (PA) and global left ventricular (LV) function in patients with coronary artery disease. The aim of this study was to evaluate by gated SPECT myocardial imaging differences in perfusion scores and LV function between stress and rest in patients with mild left ventricular dysfunction and/or normal function and previous inferior myocardial infarction (IMI) and to detect myocardial stunning.

Materials and methods

The study included 77 patients (age 53 ± 8.21) with mild left ventricular dysfunction and previous IMI divided into two groups. Group 1 consisted of 34 patients with IMI and additional ischemia on perfusion scan and group 2 with 43 patients with previous IMI without ischemia on perfusion scan. All patients underwent a 2-day stress-rest gated SPECT myocardial imaging protocol with 99m technetium-methoxyisobutylisonitrile (^99mTc-MIBI).

Results

There was a more significant post-stress to rest decrease in ejection fraction (EFps) in patients with IMI and additional ischemia (group 1) than in patients with IMI (group 2) (?1.5 ± 2.5 vs. 1.5 ± 2.3, p < 0.001). In group 1, there was a significant increase in post-stress end-systolic volume (ESVps) in comparison to ESVr (70.4 ± 29.8 vs. 66.2 ± 26.2 ml, p = 0.044). However, the decrease in EF post-stress to rest did not reach the level of significance (51.7 ± 10.8 vs. 53.2 ± 10.2%, p = 0.147). The extent and severity of perfusion abnormalities were higher on stress (SSS) than on rest images (SRS) (13.9 ± 8.6 vs. 8.3 ± 7.8, p < 0.001). There was no difference in global LV parameters or perfusion abnormalities in patients in group 2 between stress and rest except for a significant increase in the post-stress EF to rest value (57.9 ± 11.9 vs. 56.2 ± 10.5%, p = 0.018). Severe decrease of post-stress EF to rest was found in 12 (16%) patients indicating stunning.

Conclusion

In patients with mild left ventricular dysfunction and IMI with additional ischemia there is evidence of a decrease in the post-stress EF with an increase in the post-stress ESV. In addition, a significant association between the decrease of post-stress EF with the extent and severity of perfusion abnormalities was detected. Gated SPECT myocardial imaging has an important role in the evaluation of perfusion and LV function in patients with IMI especially in patients with additional ischemia.     

Correlation of metabolic tumor volume and 11C-choline uptake with the pathology of prostate cancer: evaluation by use of simultaneously recorded MR and PET images

Purpose

This study was conducted to assess the relationship between ¹¹C-choline uptake and pathologic findings obtained by combined use of magnetic resonance (MR) and positron emission tomography (PET) imaging of patients with prostate cancer.

Materials and methods

We retrospectively evaluated 69 patients with prostate cancer who underwent ¹¹C-choline PET-CT and magnetic resonance imaging before radical prostatectomy. Combined MR–PET images were acquired to obtain precise anatomic information. The maximum standardized uptake value (SUV_max) and metabolic tumor volume (MTV) were compared with pathologic findings from resected specimens as the reference standard.

Results

The mean and standard deviation of tumor SUV_max and MTV were 3.9 ± 1.8 and 12.9 ± 16.4, respectively. Tumors with high MTV (≧8.2) were more likely to be admixed with prostatic intraepithelial neoplasia (PIN) (p < 0.0001) or hyperplasia (p < 0.0001) in the background than those without these findings. Multiple regression analysis also revealed that the presence of hyperplasia (OR; 4.25, 95 % CI 1.25–14.4, p = 0.02) and PIN (OR; 9.22, 95 % CI 2.60–32.7, p = 0.001) were associated with tumors with high MTV.

Conclusion

We have demonstrated, by pathologic evaluation of patients with prostate cancer, that ¹¹C-choline uptake volume is greater for prostate cancer admixed with PIN and hyperplasia than that without.     

Reduced cardiac 123I-metaiodobenzylguanidine uptake in patients with spinocerebellar ataxia type 2: a comparative study with Parkinson’s disease

Purpose

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant neurodegenerative disorder characterized by cerebellar ataxia, supranuclear ophthalmoplegia, and peripheral neuropathy. Autonomic nervous system dysfunction is often present. This study evaluated the cardiac sympathetic function in patients with SCA2 using ¹²³I-metaiodobenzylguanidine (MIBG) in comparison with patients with Parkinson’s disease (PD) and control subjects.

Methods

Nine patients with SCA2, nine patients with PD, and nine control subjects underwent ¹²³I-MIBG imaging studies from which early and late heart-to-mediastinum (H/M) ratios and myocardial washout rates were calculated.

Results

Early (F?=?12.3, p?<?0.0001) and late (F?=?16.8, p?<?0.0001) H/M ratios were significantly different among groups. In controls, early and late H/M ratios (2.2?±?0.12 and 2.1?±?0.20) were significantly higher than in patients with SCA2 (1.9?±?0.23 and 1.8?±?0.20, both p?<?0.05) and with patients with PD (1.7?±?0.29 and 1.4?±?0.35, both p?<?0.001). There was also a significant difference in washout rates among groups (F?=?11.7, p?<?0.0001). In controls the washout rate (19.9?±?9.6 %) was significantly lower (p?<?0.005) than in patients with PD (51.0?±?23.7 %), but not different from that in SCA2 patients (19.5?±?9.4 %). In SCA2 patients, in a multivariable linear regression analysis only the Scale for the Assessment and Rating of Ataxia score was independently associated with early H/M ratio (β?=??0.12, p?<?0.05).

Conclusion

¹²³I-MIBG myocardial scintigraphy demonstrated an impairment of cardiac sympathetic function in patients with SCA2, which was less marked than in PD patients. These results suggest that ¹²³I-MIBG cardiac imaging could become a useful tool for analysing the pathophysiology of SCA2.     

Epicardial adipose tissue thickness as a predictor of impaired microvascular function in patients with non-obstructive coronary artery disease

Objective

To determine if increased epicardial adipose tissue (EAT) measured by cardiac CT could be associated with impaired myocardial flow reserve (MFR) in patients with non-obstructive coronary artery disease (CAD).

Background

Studies have shown that EAT volume is related to epicardial obstructive CAD, myocardial ischemia and major adverse cardiac events. However, the association between EAT with coronary microvascular dysfunction and impaired MFR has not been well clarified.

Methods

Consecutive patients who underwent Rb-82 positron emission tomography (PET), coronary artery calcium (CAC) scoring and non-invasive coronary computed tomography angiography (CCTA) were screened. PET scans were analysed for standard myocardial perfusion (MPI) and MFR. CCTA results were analysed and only patients with non-obstructive CAD (<50% luminal diameter stenosis) were included. EAT thickness and volumes were measured from CT scans.

Results

Of 137 patients without obstructive CAD by CCTA and with normal Rb-82 PET relative MPI, 26 (19.0%) patients had impaired MFR < 2 and 87 (64%) patients had CAC. EAT_thickness, EAT_volume and CAC values were higher in patients with impaired MFR < 2 than those with normal MFR ≥ 2 (6.7 ± 1.6 mm vs 4.4 ± 1.0 mm, P < .0001; 119.0 ± 25.3 cm³ vs 105.8 ± 30.5 cm³, P < .04 and 508.9 ± 554.3 vs 167.8 ± 253.9, P < .0001, respectively). However, EAT_thickness had a stronger negative correlation with MFR than EAT_volume and CAC (r = ?0.78 vs r = ?0.25 and ρ = ?0.32, P < .0001). With multivariable logistic regression analysis, only EAT_thickness was independently associated with impaired MFR (OR 20.7, 95% CI 4.9-87.9, P < .0001). Importantly, the receiver-operator characteristic (ROC) curves demonstrated a superior performance of EAT_thickness vs EAT_volume and EAT_thickness vs CAC in detecting impaired MFR (AUC: 0.945 vs 0.625, difference between AUC: 0.319, P < .0001; AUC: 0.945 vs 0.710, difference between AUC: 0.235, P < .0006, respectively). On ROC curve analysis, an EAT_thickness cut-off value > 5.6 mm was optimal in detecting impaired MFR with a sensitivity and specificity of 81% and 92%, respectively.

Conclusions

Increased EAT appears to be associated with impaired MFR. This parameter may help improve detection of patients at risk of microvascular dysfunction.     

Iodine-123 metaiodobenzylguanidine imaging can predict future cardiac events in Japanese patients with Parkinson’s disease

Objectives

Iodine-123 metaiodobenzylguanidine (¹²³I-MIBG) myocardial scintigraphy provides useful diagnostic information in differentiating Parkinson’s disease (PD) from other neurological diseases. Moreover, a number of studies have reported that ¹²³I-MIBG imaging provides powerful diagnostic and prognostic information in congestive heart failure (HF) patients. The aim of the present study was to investigate the cardiovascular predictive value of cardiac ¹²³I-MIBG imaging in patients with PD.

Methods

Seventy-eight patients with PD were retrospectively studied. All patients underwent ¹²³I-MIBG imaging at 30 min (early) and 240 min (delayed) after the tracer injection, and clinical parameters were also investigated.

Results

During a mean follow-up of 27 ± 12 months, 5 patients required hospitalization for HF. There were no occurrences of myocardial infarction, fatal arrhythmia or sudden death. There was no significant coronary artery stenosis, significant valvular heart disease, or cardiomyopathy in the HF patients. The left ventricular ejection fraction (LVEF) was normal in the HF patients. ¹²³I-MIBG delayed heart to mediastinal ratio (delayed H/M) was lower and washout rate (WR) was higher in HF patients than non-HF patients (1.62 ± 0.21 vs. 1.34 ± 0.08, p = 0.019; 31.9 ± 5.5 vs. 38.2 ± 3.3, p = 0.005, respectively). Both WR and delayed H/M did not correlate with Hoehn and Yahr stage. The WR showed a weak negative correlation with delayed H/M (R = ?0.357, p < 0.001) upon simple linear regression analysis. A multivariate Cox regression analysis revealed that WR and delayed H/M were independently associated with HF (p = 0.014, p = 0.029, respectively). Kaplan–Meier analysis revealed that patients with abnormal WR (>37 %) and delayed H/M (<1.48) had a higher incidence of HF than those with normal WR and delayed H/M (p = 0.014, p = 0.04, respectively).

Conclusions

WR showed stronger predictive power than delayed H/M in Kaplan–Meier analysis. WR has more useful cardiovascular predictive value than delayed H/M in Japanese patients with PD. Further studies are needed to clarify the significance of abnormal MIBG uptake in PD patients.     

Intravoxel incoherent motion perfusion imaging in acute stroke: initial clinical experience

Introduction

Intravoxel incoherent motion (IVIM) imaging is an MRI perfusion technique that uses a diffusion-weighted sequence with multiple b values and a bi-compartmental signal model to measure the so-called pseudo-diffusion of blood caused by its passage through the microvascular network. The goal of the current study was to assess the feasibility of IVIM perfusion fraction imaging in patients with acute stroke.

Methods

Images were collected in 17 patients with acute stroke. Exclusion criteria were onset of symptoms to imaging >5 days, hemorrhagic transformation, infratentorial lesions, small lesions <0.5 cm in minimal diameter and hemodynamic instability. IVIM imaging was performed at 3 T, using a standard spin-echo Stejskal-Tanner pulsed gradients diffusion-weighted sequence, using 16 b values from 0 to 900 s/mm². Image quality was assessed by two radiologists, and quantitative analysis was performed in regions of interest placed in the stroke area, defined by thresholding the apparent diffusion coefficient maps, as well as in the contralateral region.

Results

IVIM perfusion fraction maps showed an area of decreased perfusion fraction f in the region of decreased apparent diffusion coefficient. Quantitative analysis showed a statistically significant decrease in both IVIM perfusion fraction f (0.026?±?0.019 vs. 0.056?±?0.025, p?=?2.2?·?10^?6) and diffusion coefficient D compared with the contralateral side (3.9?±?0.79?·?10^?4 vs. 7.5?±?0.86?·?10^?4 mm²/s, p?=?1.3?·?10^?20).

Conclusion

IVIM perfusion fraction imaging is feasible in acute stroke. IVIM perfusion fraction is significantly reduced in the visible infarct. Further studies should evaluate the potential for IVIM to predict clinical outcome and treatment response.