Aorta Segmentation in 3D CT Images by Combining Image Processing and Machine Learning Techniques.

PURPOSE: Aorta segmentation is extremely useful in clinical practice, allowing the diagnosis of numerous pathologies, such as dissections, aneurysms and occlusive disease. In such cases, image segmentation is prerequisite for applying diagnostic algorithms, which in turn allow the prediction of possible complications and enable risk assessment, which is crucial in saving lives. The aim of this paper is to present a novel fully automatic 3D segmentation method, which combines basic image processing techniques and more advanced machine learning algorithms, for detecting and modelling the aorta in 3D CT imaging data. METHODS: An initial intensity threshold-based segmentation procedure is followed by a classification-based segmentation approach, based on a Markov Random Field network. The result of the proposed two-stage segmentation process is modelled and visualized. RESULTS: The proposed methodology was applied to 16 3D CT data sets and the extracted aortic segments were reconstructed as 3D models. The performance of segmentation was evaluated both qualitatively and quantitatively against other commonly used segmentation techniques, in terms of the accuracy achieved, compared to the actual aorta, which was defined manually by experts. CONCLUSION: The proposed methodology achieved superior segmentation performance, compared to all compared segmentation techniques, in terms of the accuracy of the extracted 3D aortic model. Therefore, the proposed segmentation scheme could be used in clinical practice, such as in treatment planning and assessment, as it can speed up the evaluation of the medical imaging data, which is commonly a lengthy and tedious process.

The Role of ECG Strain Pattern in Prognosis after TAVI: A Sub-Analysis of the DIRECT Trial.

BACKGROUND: The presence of an electrocardiographic (ECG) strain pattern-among other ECG features-has been shown to be predictive of adverse cardiovascular outcomes in asymptomatic patients with aortic stenosis. However, data evaluating its impact on symptomatic patients undergoing TAVI are scarce. Therefore, we tried to investigate the prognostic impact of baseline ECG strain pattern on clinical outcomes after TAVI. METHODS: A sub-group of patients of the randomized DIRECT (Pre-dilatation in Transcatheter Aortic Valve Implantation Trial) trial with severe aortic stenosis who underwent TAVI with a self-expanding valve in one single center were consecutively enrolled. Patients were categorized into two groups according to the presence of ECG strain. Left ventricular strain was defined as the presence of ≥1 mm convex ST-segment depression with asymmetrical T-wave inversion in leads V5 to V6 on the baseline 12-lead ECG. Patients were excluded if they had paced rhythm or left bundle branch block at baseline. Multivariate Cox proportional hazard regression models were generated to assess the impact on outcomes. The primary clinical endpoint was all-cause mortality at 1 year after TAVI. RESULTS: Of the 119 patients screened, 5 patients were excluded due to left bundle branch block. Among the 114 included patients (mean age: 80.8 ± 7), 37 patients (32.5%) had strain pattern on pre-TAVI ECG, while 77 patients (67.5%) did not exhibit an ECG strain pattern. No differences in baseline characteristics were found between the two groups. At 1 year, seven patients reached the primary clinical endpoint, with patients in the strain group demonstrating significantly higher mortality in Kaplan-Meier plots compared to patients without left ventricular strain (five vs. two, log-rank p = 0.022). There was no difference between the strain and no strain group regarding the performance of pre-dilatation (21 vs. 33, chi-square p = 0.164). In the multivariate analysis, left ventricular strain was found to be an independent predictor of all-cause mortality after TAVI [Exp(B): 12.2, 95% Confidence Intervals (CI): 1.4-101.9]. CONCLUSION: Left ventricular ECG strain is an independent predictor of all-cause mortality after TAVI. Thus, baseline ECG characteristics may aid in risk-stratifying patients scheduled for TAVI.

Lipoprotein(a) and inflammation- pathophysiological links and clinical implications for cardiovascular disease.

The role of lipoprotein(a) (Lp[a]) as a significant and possibly causal cardiovascular disease (CVD) risk factor has been well established. Many studies, mostly experimental, have supported inflammation as a mediator of Lp(a)-induced increase in CVD risk. Lp(a), mainly through oxidized phospholipids bound to its apolipoprotein(a) part, leads to monocyte activation and endothelial dysfunction. The relationship between Lp(a) and inflammation is bidirectional as Lp(a) levels, besides being associated with inflammatory properties, are regulated by inflammatory stimuli or anti-inflammatory treatment. Reduction of Lp(a) concentration, especially by potent siRNA agents, contributes to partial reversion of the Lp(a) related inflammatory profile. This review aims to present the current pathophysiological and clinical evidence of the relationship between Lp(a) and inflammation.

Study Level Meta-Analysis of Transcatheter Aortic Valve Implantation With the ACURATE neo Self-Expanding Transcatheter Heart Valve.

The ACURATE neo transcatheter aortic valve is a self-expanding device. Several studies have investigated safety and efficacy, but meta-analysis and pooled data are lacking. We aimed to provide a comprehensive systematic review and meta-analysis on the clinical outcomes of transcatheter aortic valve implantation with the ACURATE neo valve. A systematic literature search for eligible records was conducted. The primary endpoint was device success as designated by Valve Academic Research Consortium-2 criteria. The secondary endpoints (time frame: 30 days) were all-cause mortality, stroke, myocardial infarction, need for new permanent pacemaker, major vascular complications, major bleeding, acute kidney injury stage II or III, and paravalvular regurgitation grade moderate or severe (II or III). Our search yielded a total of 355 records, 20 of those (n = 5858 ACURATE neo receivers) were included in our meta-analysis. Device success was achieved in 94.5% (95% confidence interval [CI], 91.4-96.5%) of the patients. The 30-day all-cause mortality incidence proportion was 1.8% (95% CI, 1.3-2.4%). New pacemaker implantation was required in 7.7% (95% CI, 6.4-9.2%) of the patients, stroke occurred in 1.9% (95% CI, 1.6-2.3%), myocardial infarction in 0.5% (95% CI, 0.3-0.7%), major bleeding in 5.0% (95% CI, 3.9-6.5%), major vascular complication in 5.6% (95% CI, 4.0-7.8%), acute kidney injury stage ≥2 in 2.5% (95% CI, 1.8-3.4%), and paravalvular leak grade ≥moderate was observed in 4.3% (95% CI, 3.0-6.2%). Balloon predilatation and postdilatation incidence was 93.9% (95% CI, 87.0-97.3%) and 43.2% (95% CI, 37.9-48.6%), respectively. ACURATE neo appears to be safe and effective in our analysis with high device success incidence, low mortality, and low new pacemaker implantations.

Transcatheter mitral valve-in-valve replacement transeptally using a novel balloon-expandable device.

We describe a patient with symptomatic severe mitral regurgitation, due to a failed 33-mm Epic (St. Jude Medical, St. Paul, MN) bioprosthetic heart valve surgically implanted 10-year before. For this specific purpose, we implanted a novel balloon-expandable transcatheter heart valve, the MyVal (Meril Life Science, Vapi, India). To the best of our knowledge, this is the second case describing the implantation of MyVal in a degenerative, surgically placed bioprosthesis.

Role of cardiac CT in the diagnostic evaluation and risk stratification of patients with myocardial infarction and non-obstructive coronary arteries (MINOCA): rationale and design of the MINOCA-GR study.

INTRODUCTION: Myocardial infarction with non-obstructive coronary arteries (MINOCA) occurs in 5%-15% of all patients with acute myocardial infarction. Cardiac MR (CMR) and optical coherence tomography have been used to identify the underlying pathophysiological mechanism in MINOCA. The role of cardiac CT angiography (CCTA) in patients with MINOCA, however, has not been well studied so far. CCTA can be used to assess atherosclerotic plaque volume, vulnerable plaque characteristics as well as pericoronary fat tissue attenuation, which has not been yet studied in MINOCA. METHODS AND ANALYSIS: MINOCA-GR is a prospective, multicentre, observational cohort study based on a national registry that will use CCTA in combination with CMR and invasive coronary angiography (ICA) to evaluate the extent and characteristics of coronary atherosclerosis and its correlation with pericoronary fat attenuation in patients with MINOCA. A total of 60 consecutive adult patients across 4 participating study sites are expected to be enrolled. Following ICA and CMR, patients will undergo CCTA during index hospitalisation. The primary endpoints are quantification of extent and severity of coronary atherosclerosis, description of high-risk plaque features and attenuation profiling of pericoronary fat tissue around all three major epicardial coronary arteries in relation to CMR. Follow-up CCTA for the evaluation of changes in pericoronary fat attenuation will also be performed. MINOCA-GR aims to be the first study to explore the role of CCTA in combination with CMR and ICA in the underlying pathophysiological mechanisms and assisting in diagnostic evaluation and prognosis of patients with MINOCA. ETHICS AND DISSEMINATION: The study protocol has been approved by the institutional review board/independent ethics committee at each site prior to study commencement. All patients will provide written informed consent. Results will be disseminated at national meetings and published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT4186676.

Transluminal attenuation gradient derived from coronary CT angiography to predict ischemia in SPECT myocardial perfusion imaging: Effect of coronary cross-sectional area.

BACKGROUND: Coronary computed tomography angiography (CCTA)-based transluminal attenuation gradient (TAG) was suggested to determine the functional significance of a stenosis. However, evidence that TAG acquired by wide-volume scanners can assess the hemodynamic significance of stenosis assessed by single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is lacking. Moreover, coronary cross-sectional area may influence TAG. Hence, we aimed at assessing the diagnostic value of TAG to predict ischemia in SPECT-MPI and the correlation between TAG and the transluminal cross-sectional area gradient (TCG). METHODS: Patients undergoing CCTA and SPECT-MPI for suspected coronary artery disease were included. TAG and TCG were calculated measuring the mean vessel attenuation and the cross-sectional area along major coronary vessels at 5-mm intervals. RESULTS: A total of 255 coronary arteries of 87 patients were included. TAG and TCG did not discriminate between coronary arteries with or without ischemia as assessed by SPECT-MPI (p = .44 and p = .25, respectively). The area under the curve to predict ischemia was not increased by adding TAG (0.88, 95% CI 0.83-0.92) or TCG (0.87, 95% CI 0.81-0.90) to CCTA alone (0.85, 95% CI 0.80-0.89). There was a significant correlation between TAG and TCG (r = 0.43; p < .001). CONCLUSIONS: CCTA-derived TAG and TCG do not offer any value in predicting ischemia assessed by SPECT-MPI. TAG is partly affected by differences in the coronary luminal area.

Splenic switch-off as a novel marker for adenosine response in nitrogen-13 ammonia PET myocardial perfusion imaging: Cross-validation against CMR using a hybrid PET/MR device.

BACKGROUND: No methodology is available to distinguish truly reduced myocardial flow reserve (MFR) in positron emission tomography myocardial perfusion imaging (PET MPI) from seemingly impaired MFR due to inadequate adenosine response. The adenosine-induced splenic switch-off (SSO) sign has been proposed as a potential marker for adequate adenosine response in cardiac magnetic resonance (CMR). We assessed the feasibility of detecting SSO in nitrogen-13 ammonia PET MPI using SSO in CMR as the standard of reference. METHODS AND RESULTS: Fifty patients underwent simultaneous CMR and PET MPI on a hybrid PET/MR device with co-injection of a gadolinium-based contrast agent and nitrogen-13 ammonia during rest and adenosine-induced stress. In CMR, SSO was assessed visually (positive vs negative SSO) and quantitatively by calculating the ratio of the peak signal intensity of the spleen during stress over rest (SIR). In PET MPI, the splenic signal activity ratio (SAR) was calculated as the maximal standard uptake value of the spleen during stress over rest. The median SIR was significantly lower in patients with positive versus negative SSO in CMR (0.57 [IQR 0.49 to 0.62] vs 0.89 [IQR 0.76 to 0.98]; P < .001). Similarly, median SAR in PET MPI was significantly lower in patients with positive versus negative SSO (0.40 [IQR 0.32 to 0.45] vs 0.80 [IQR 0.47 to 0.98]; P < .001). CONCLUSION: Similarly to CMR, SSO can be detected in nitrogen-13 ammonia PET MPI. This might help distinguish adenosine non-responders from patients with truly impaired MFR due to microvascular dysfunction or multivessel coronary artery disease.

Visceral adipose tissue phenotype and hypoadiponectinemia are associated with aortic Fluorine-18 fluorodeoxyglucose uptake in patients with familial dyslipidemias.

BACKGROUND: The role of adipose tissue (AT) in arterial inflammation in familial dyslipidaemias is poorly studied. We investigated the relationship between AT and arterial inflammation in patients with heterozygous familial hypercholesterolemia (heFH) and familial combined hyperlipidemia (FCH). METHODS AND RESULTS: A total of 40 patients (20 heFH/20 FCH) and a subgroup of 20 of non-heFH/FCH patients were enrolled. Participants underwent blood sampling for serum adipokine measurements and Fluorine-18 fluorodeoxyglucose (18F-FDG) PET/CT imaging. Abdominal visceral (VAT) and subcutaneous (SAT) AT volumes and AT and abdominal aorta 18F-FDG uptake were quantified. FCH patients had increased VAT (pANOVA = 0.004) and SAT volumes (pANOVA = 0.003), lower VAT metabolic activity (pANOVA = 0.0047), and lower adiponectin levels (pANOVA = 0.007) compared to heFH or the control group. Log(Serum adiponectin) levels were correlated with aortic TBR (b = - 0.118, P = 0.038). In mediation analysis, VAT volume was the major determinant of circulating adiponectin, an effect partly mediated via VAT TBR. Clustering of the population of heFH/FCH by VAT volume/TBR and serum adiponectin identified two distinct patient clusters with significant differences in aortic TBR levels (2.11 ± 0.06 vs 1.89 ± 0.05, P= 0.012). CONCLUSIONS: VAT phenotype (increased VAT volume and/or high VAT TBR) and hypoadiponectinemia may account for the observed differences in arterial inflammation levels between heFH and FCH patients.

Carotid Artery Temperature Reduction with Statin Therapy in Patients with Familial Hyperlipidemia Syndromes.

BACKGROUND: Microwave radiometry (MWR) assesses non-invasive carotid artery temperatures reflecting inflammation. In the present study, we aimed to investigate the impact of hypolipidemic therapy either with simvastatin or with combination simvastatin plus ezetimibe on carotid artery temperatures of patients with familial hyperlipidemia syndromes (FHS). METHODS: Consecutive patients with diagnosis of either familial heterozygous hypercholesterolemia (heFH) or familial combined hyperlipidemia (FCH) were included in the study. Patients were assigned to either simvastatin 40 mg or simvastatin 40 mg plus ezetimibe 10 mg, according to the discretion of the physician. FHS patients who refused statin therapy were used as a control group. Common carotid intima-media thickness (ccIMT) was measured and ΔΤ (maximum-minimum) temperature measurements were performed across each carotid during MWR evaluation. RESULTS: In total, 115 patients were included in the study. Of them, 40 patients received simvastatin (19 heFH and 21 FCH), 41 simvastatin + ezetimibe (31 heFH and 10 FCH), and 34 (21 heFH and 13 FCH) no statin. Carotid artery temperatures were significantly reduced at 6 months in FH patients who received hypolipidemic treatment (0.83 ± 0.34 versus 0.63 ± 0.24 °C, p = 0.004 for simvastatin, 1.00 ± 0.38 versus 0.69 ± 0.23 °C, p < 0.001 for simvastatin + ezetimibe), but no change was recorded in controls (0.72 ± 0.26 versus 0.70 ± 0.26 °C, p = 0.86). CONCLUSIONS: Hypolipidemic therapy reduced carotid temperatures in FHS patients.

Prognostic value of regional myocardial flow reserve derived from 13N-ammonia positron emission tomography in patients with suspected coronary artery disease.

PURPOSE: To assess the prognostic value of regional quantitative myocardial flow measures as assessed by 13N-ammonia positron emission tomography (PET) myocardial perfusion imaging (MPI) in patients with suspected coronary artery disease (CAD). METHODS: We retrospectively included 150 consecutive patients with suspected CAD who underwent clinically indicated 13 N-ammonia PET-MPI and who did not undergo revascularization within 90 days of PET-MPI. The presence or absence of a decreased global myocardial flow reserve (i.e., MFR < 2) as well as decreased regional MFR (i.e., ≥ 2 adjacent segments with MFR < 2) was recorded, and patients were classified as having preserved global and regional MFR (MFR group 1), preserved global but decreased regional MFR (MFR group 2), or decreased global and regional MFR (MFR group 3). We obtained follow-up regarding major adverse cardiac events (MACE, i.e., a combined endpoint including all-cause death, non-fatal myocardial infarction, and late revascularization) and all-cause death. RESULTS: Over a median follow-up of 50 months (IQR 38-103), 30 events occurred in 29 patients. Kaplan-Meier analysis showed significantly reduced event-free and overall survival in MFR groups 2 and 3 compared to MFR group 1 (log-rank: p = 0.015 and p = 0.013). In a multivariable Cox regression analysis, decreased regional MFR was an independent predictor for MACE (adjusted HR 3.44, 95% CI 1.17-10.11, p = 0.024) and all-cause death (adjusted HR 4.72, 95% CI 1.07-20.7, p = 0.04). CONCLUSIONS: A decreased regional MFR as assessed by 13 N-ammonia PET-MPI confers prognostic value by identifying patients at increased risk for future adverse cardiac outcomes and all-cause death.

Vascular Inflammation and Cardiovascular Burden in Metastatic Breast Cancer Female Patients Receiving Hormonal Treatment and CDK 4/6 Inhibitors or Everolimus.

Background: Chemotherapy regimens for breast cancer treatment can promote vascular dysfunction and lead to high cardiovascular risk. Purpose: To investigate the cardiovascular burden and vascular inflammation in metastatic breast cancer patients receiving CDK 4/6 inhibitors or everolimus in addition to standard hormonal treatment. Methods: 22 consecutive female patients with metastatic breast cancer were enrolled. Relative wall thickness (RWT) and left ventricle mass (LVM) measurements by transthoracic echocardiography were obtained followed by 24-h ambulatory blood pressure monitoring, and 18F-fluorodeoxyglucose positron-emission tomography/computed tomography imaging. Uptake of the radiotracer in the aortic wall was estimated as tissue-to-background ratio (TBR). Each patient was assessed for the aforementioned parameters before the initiation and after 6 months of treatment. Results: At follow up, patients assigned to CDK 4/6 treatment demonstrated increased 24-h systolic blood pressure (SBP) (p = 0.004), daytime SBP (p = 0.004) and night time SBP (p = 0.012) (Group effect). The 24-h mean arterial pressure measurements were also higher in CDK 4/6 population, in comparison to everolimus that displayed firm values (Group effect- p = 0.035, Interaction effect-p = 0.023). Additionally, 24 h diastolic blood pressure recordings in CDK 4/6 therapy were higher opposed to everolimus that remained consistent (Interaction effect- p = 0.010). In CDK 4/6 group, TBR aorta also increased significantly, whereas TBR values in everolimus remained stable (Interaction effect-p = 0.049). Both therapeutic regimens displayed statistically significant damaging effect to RWT and LVM. Conclusion: CDK 4/6 inhibitors and hormonal treatment can lead to increased vascular inflammation, and higher blood pressure compared to the combination of everolimus and hormonal treatment. Moreover, both treatment strategies promoted left ventricle remodeling.

Long-Term Outcomes and Valve Performance in Patients Undergoing Transcatheter Aortic Valve Implantation.

Transcatheter aortic valve implantation (TAVI) is an established method for treating patients with aortic valve stenosis. We sought to determine the long-term clinical outcomes and performance of a self-expanding bioprosthesis beyond 5 years. Consecutive patients scheduled for TAVI were included in the analysis. Primary end points were all-cause and cardiovascular mortality, structural valve deterioration (SVD) and bioprosthetic valve failure (BVF), based on the VARC-2 criteria and consensus statement by ESC/EAPCI. The study prospectively evaluated 273 patients (80.61 ± 7.00 years old, 47% females) who underwent TAVI with CoreValve/Evolut-R (Medtronic Inc.). The median follow-up duration was 5 years (interquartile range: 2.9 to 6; longest: 8 years). At 1, 5, and 8 years, estimated survival rates were 89.0%, 61.1%, and 56.0%, respectively, while cardiovascular mortality was 8% at the end of follow-up. Regarding valve performance, 5% of patients had early BVF and 1% had late BVF. Concerning SVD, 16 patients (6% of the total population) had moderate SVD (91% had an increase in mean gradient), with no severe SVD cases. Five patients with SVD died during follow-up. Actual analysis of the 8-year cumulative incidence of function of moderate SVD was 5.9% (2.5% to 16.2%). At multivariate analysis, the factor that emerged as an independent predictor for future SVD, was smaller bioprosthetic valve size (HR 0.58, 95% CI 0.41 to 0.82, p = 0.002). Long-term evaluation beyond 5 years after TAVI with a self-expanding bioprosthesis demonstrated low rates of cardiovascular mortality and structural valve deterioration. Valve size was an independent predictor for SVD.

Coronary artery lumen volume index as a marker of flow-limiting atherosclerosis-validation against 13N-ammonia positron emission tomography.

OBJECTIVES: Coronary artery volume indexed to left myocardial mass (CAVi), derived from coronary computed tomography angiography (CCTA), has been proposed as an indicator of diffuse atherosclerosis. We investigated the association of CAVi with quantitative flow parameters and its ability to predict ischemia as derived from 13N-ammonia positron emission tomography myocardial perfusion imaging (PET-MPI). METHODS: Sixty patients who underwent hybrid CCTA/PET-MPI due to suspected CAD were retrospectively included. CAVi was defined as total coronary artery lumen volume over myocardial mass, both derived from CCTA. From PET-MPI, quantitative stress and rest myocardial blood flow (MBF) and myocardial flow reserve (MFR) were obtained and correlated with CAVi, and semi-quantitative perfusion images were analyzed for the presence of ischemia. Harrell's c-statistic and net reclassification improvement (NRI) analysis were performed to evaluate the incremental value of CAVi over the CCTA model (i.e., stenosis > 50% and > 70%). RESULTS: CAVi correlated moderately with stress MBF and MFR (R = 0.50, p < 0.001, and R = 0.39, p = 0.002). Mean stress MBF and MFR were lower in patients with low (i.e., ≤ 20.2 mm3/g, n = 24) versus high (i.e., > 20.2 mm3/g, n = 36) CAVi (p < 0.001 for both comparisons). CAVi was independently associated with abnormal stress MBF (OR 0.90, 95% CI 0.82-0.998, p = 0.045). CAVi increased the predictive ability of the CCTA model for abnormal stress MBF and ischemia (c-statistic 0.763 versus 0.596, pdiff < 0.05 and 0.770 versus 0.645, pdiff < 0.05, NRI 0.84, p = 0.001 and 0.96, p < 0.001, respectively). CONCLUSIONS: CAVi exhibits incremental value to predict both abnormal stress MBF and ischemia over CCTA alone. KEY POINTS: • Coronary artery volume indexed to left myocardial mass (CAVi), derived from coronary computed tomography angiography (CCTA), is correlated with myocardial blood flow indices derived from 13N-ammonia positron emission tomography myocardial perfusion imaging. • CAVi is independently associated with abnormal stress myocardial blood flow. • CAVi provides incremental diagnostic value over CCTA for both abnormal stress MBF and ischemia.

Prognostic Value of Quantitative Metrics From Positron Emission Tomography in Ischemic Heart Failure.

OBJECTIVES: The aim of this study was to investigate the prognostic and clinical value of quantitative positron emission tomographic (PET) metrics in patients with ischemic heart failure. BACKGROUND: Although myocardial flow reserve (MFR) is a strong predictor of cardiac risk in patients without heart failure, it is unknown whether quantitative PET metrics improve risk stratification in patients with ischemic heart failure. METHODS: The study included 254 patients referred for stress and rest myocardial perfusion imaging and viability testing using PET. Major adverse cardiac event(s) (MACE) consisted of death, resuscitated sudden cardiac death, heart transplantation, acute coronary syndrome, hospitalization for heart failure, and late revascularization. RESULTS: MACE occurred in 170 patients (67%) during a median follow-up of 3.3 years. In a multivariate Cox proportional hazards model including multiple quantitative PET metrics, only MFR predicted MACE significantly (p = 0.013). Beyond age, symptom severity, diabetes mellitus, previous myocardial infarction or revascularization, 3-vessel disease, renal insufficiency, ejection fraction, as well as presence and burden of ischemia, scar, and hibernating myocardium, MFR was strongly associated with MACE (adjusted hazard ratio per increase in MFR by 1: 0.63; 95% confidence interval: 0.45 to 0.91). Incorporation of MFR into a risk assessment model incrementally improved the prediction of MACE (likelihood ratio chi-square test [16] = 48.61 vs. chi-square test [15] = 39.20; p = 0.002). CONCLUSIONS: In this retrospective analysis of a single-center cohort, quantitative PET metrics of myocardial blood flow all improved risk stratification in patients with ischemic heart failure. However, in a hypothesis-generating analysis, MFR appears modestly superior to the other metrics as a prognostic index.

Myocardial creep-induced misalignment artifacts in PET/MR myocardial perfusion imaging.

PURPOSE: Misalignment between positron emission tomography (PET) datasets and attenuation correction (AC) maps is a potential source of artifacts in myocardial perfusion imaging (MPI). We assessed the impact of adenosine on the alignment of AC maps derived from magnetic resonance (MR) and PET datasets during MPI on a hybrid PET/MR scanner. METHODS: Twenty-eight volunteers underwent adenosine stress and rest 13N-ammonia MPI on a PET/MR. We acquired Dixon sequences for the creation of MRAC maps. After reconstruction of the original non-shifted PET images, we examined MRAC and PET datasets for cardiac spatial misalignment and, if necessary, reconstructed a second set of shifted PET images after manually adjusting co-registration. Summed rest, stress, and difference scores (SRS, SSS, and SDS) were compared between shifted and non-shifted PET images. Additionally, we measured the amount of cranial movement of the heart (i.e., myocardial creep) after termination of adenosine infusion. RESULTS: Realignment was necessary for 25 (89.3%) stress and 12 (42.9%) rest PET datasets. Median SRS, SSS, and SDS of the non-shifted images were 6 (IQR = 4-7), 12 (IQR = 7-18), and 8 (IQR = 2-11), respectively, and of the shifted images 2 (IQR = 1-6), 4 (IQR = 7-18), and 1 (IQR = 0-2), respectively. All three scores were significantly higher in non-shifted versus shifted images (all p < 0.05). The difference in SDS correlated moderately but significantly with the amount of myocardial creep (r = 0.541, p = 0.005). CONCLUSION: Misalignment of MRAC and PET datasets commonly occurs during adenosine stress MPI on a hybrid PET/MR device, potentially leading to an increase in false-positive findings. Our results suggest that myocardial creep may substantially account for this and prompt for a careful review and correction of PET/MRAC data.