Yuki Tanabe

Quantitative circumferential strain analysis using adenosine triphosphate-stress/rest 3-T tagged magnetic resonance to evaluate regional contractile dysfunction in ischemic heart disease

PURPOSE We evaluated whether a quantitative circumferential strain (CS) analysis using adenosine triphosphate (ATP)-stress/rest 3-T tagged magnetic resonance (MR) imaging can depict myocardial ischemia as contractile dysfunction during stress in patients with suspected coronary artery disease (CAD). We evaluated whether it can differentiate between non-ischemia, myocardial ischemia, and infarction. We assessed its diagnostic performance in comparison with ATP-stress myocardial perfusion MR and late gadolinium enhancement (LGE)-MR imaging. METHODS In 38 patients suspected of having CAD, myocardial segments were categorized as non-ischemic (n=485), ischemic (n=74), or infarcted (n=49) from the results of perfusion MR and LGE-MR. The peak negative CS value, peak circumferential systolic strain rate (CSR), and time-to-peak CS were measured in 16 segments. RESULTS A cutoff value of -12.0% for CS at rest allowed differentiation between infarcted and other segments with a sensitivity of 79%, specificity of 76%, accuracy of 76%, and an area under the curve (AUC) of 0.81. Additionally, a cutoff value of 477.3ms for time-to-peak CS at rest allowed differentiation between infarcted and other segments with a sensitivity of 61%, specificity of 91%, accuracy of 88%, and an AUC of 0.75. The differences in CS values between ATP-stress and rest conditions (ΔCS) in non-ischemic segments (median [first quartile, third quartile] -1.7 [-3.2, -0.1] %) were smaller than in segments with ischemia (+1.1 [+0.3, +2.3] %, p<0.001). A cutoff value of +0.3% for the ΔCS value could differentiate segments with ischemia from non-ischemic segments with a sensitivity of 75%, a specificity of 82%, an accuracy of 82%, and an AUC of 0.86. CONCLUSIONS Circumferential strain analysis using tagged MR can quantitatively assess contractile dysfunction in ischemic and infarcted myocardium.

Estimation of myocardial flow reserve utilizing an ultrafast cardiac SPECT: Comparison with coronary angiography, fractional flow reserve, and the SYNTAX score

BACKGROUND Quantitative assessment of myocardial flow reserve (MFR) by single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is challenging but may facilitate evaluation of multi-vessel coronary artery disease (CAD). METHODS We enrolled 153 patients with suspected or known CAD, referred for pharmacological stress MPI. They underwent a 99mTc-perfusion stress/rest SPECT with an ultrafast cadmium-zinc-telluride (CZT) camera. Dynamic data were acquired and time-activity curves fitted to a 1-tissue compartment analysis with input function. K1 was assigned for stress and rest data. The MFR index (MFRi) was calculated as K1 stress/K1 at-rest. The findings were validated by invasive coronary angiography in 69 consecutive patients. RESULTS The global MFRi was 1.46 (1.16-1.76), 1.33 (1.12-1.54), and 1.18 (1.01-1.35), for 1-vessel disease (VD), 2-VD, and 3-VD, respectively. In the 3-VD, global MFRi was lower than that in 0-VD (1.63 [1.22-2.04], P<0.0001) and 1-VD (P=0.003). Multivariate logistic regression analysis for 3-VD showed significant associations with smoking history (odds ratio [OR]: 4.4 [0.4-8.4]), left ventricular ejection fraction (OR: 61.6 [57.5-66.0]), and global MFRi (OR: 119.6 [111.5-127.7], P=0.002). A cut-off value of 1.3 yielded 93.3% sensitivity and 75.9% specificity for diagnosing 3-VD. Fractional flow reserve positively correlated with regional MFRi (r=0.62, P=0.008), and the SYNTAX score correlated negatively with global MFRi (r=0.567, P=0.0003). CONCLUSION We developed and validated a clinically available method for MFR quantification by dynamic 99mTc-perfusion SPECT utilizing a CZT camera, which improves the detectability of multi-vessel CAD.

Late iodine enhancement computed tomography with image subtraction for assessment of myocardial infarction

AbstractObjectiveTo evaluate the feasibility of image subtraction in late iodine enhancement CT (LIE-CT) for assessment of myocardial infarction (MI).MethodsA comprehensive cardiac CT protocol and late gadolinium enhancement MRI (LGE-MRI) was used to assess coronary artery disease in 27 patients. LIE-CT was performed after stress CT perfusion (CTP) and CT angiography. Subtraction LIE-CT was created by subtracting the mask volume of the left ventricle (LV) cavity from the original LIE-CT using CTP dataset. The %MI volume was quantified as the ratio of LIE to entire LV volume, and transmural extent (TME) of LIE was classified as 0%, 1–24%, 25–49%, 50–74% or 75–100%. These results were compared with LGE-MRI using the Spearman rank test, Bland-Altman method and chi-square test.ResultsOne hundred twenty-five (29%) of 432 segments were positive on LGE-MRI. Correlation coefficients for original and subtraction LIE-CT to LGE-MRI were 0.79 and 0.85 for %MI volume. Concordances of the 5-point grading scale between original and subtraction LIE-CT with LGE-MRI were 75% and 84% for TME; concordance was significantly improved using the subtraction technique (p <0.05).ConclusionSubtraction LIE-CT allowed more accurate assessment of MI extent than the original LIE-CT.Key Points• Subtraction LIE-CT allows for accurate assessment of the extent of myocardial infarction. • Subtraction LIE-CT shows a close correlation with LGE-MRI in %MI volume. • Subtraction LIE-CT has significantly higher concordance with TME assessment than original LIE-CT.

Peak enhancement ratio of myocardium to aorta for identification of myocardial ischemia using dynamic myocardial computed tomography perfusion imaging

BACKGROUND This study aimed to evaluate the feasibility of peak enhancement (PE) ratio of myocardium to aorta (PER) derived from stress dynamic computed tomography myocardial perfusion imaging (CTP) for the detection of myocardial ischemia assessed by magnetic resonance (MR) imaging. METHODS Forty-four patients who underwent stress dynamic CTP and MR imaging were retrospectively evaluated. From the time-attenuation curve, myocardial PE, PER, and myocardial blood flow (MBF) were calculated on a segment-based analysis. The correlation between myocardial and aortic PE was assessed by Spearmans correlation, and the differences in myocardial PE and PER between normal and ischemic myocardium were assessed by the Mann-Whitney U-test. The diagnostic accuracies of myocardial PE, PER, and MBF for detecting myocardial ischemia were compared by receiver operating characteristic analysis. RESULTS Of 704 segments, 258 segments (37%) were diagnosed as myocardial ischemia with MR imaging. Myocardial and aortic PE were significantly correlated in both normal and ischemic segments (r=0.76 and 0.58; p<0.05, in each). The myocardial PE and PER of ischemic segments were significantly lower than those of normal segments (p<0.05, in each). Sensitivity and specificity were 61% [95% confidence interval (CI), 55-70%] and 83% (95% CI, 73-87%) for myocardial PE, 78% (67-88%) and 82% (95% CI, 70-91%) for PER, and 81% (95% CI, 73-87%) and 85% (95% CI, 79-92%) for MBF. There was a significantly larger area under the curve for PER (0.87; 95% CI, 0.84-0.90) and MBF (0.88; 95%CI, 0.85-0.91), compared to myocardial PE (0.75; 95% CI, 0.70-0.79) (p<0.05, in each). There was no significant difference in area under the curve between PER and MBF. CONCLUSIONS The semi-quantitative parameter of PER showed a high diagnostic accuracy for the detection of myocardial ischemia, comparable to that of MBF.

Quantification of Coronary Flow Reserve by 15 O-Water PET with ATP Stress; from a Practical Application Perspective

15 O-water has been considered to be a near-perfect and the most ideal myocardial blood flow (MBF) tracer because it is freely diffusible, metabolically inert, and independent of the myocardial metabolic state, which results in the highest extraction fraction. Absolute coronary flow reserve (CFR) is the ratio of MBF during maximal hyperemia in a coronary artery to MBF in the same artery under resting conditions and can be quantified noninvasively by positron emission tomography (PET). A growing body of literature is accumulating to show that the prognostic value of absolute MBF or CFR, which is quantified by cardiac PET. ATP infusion protocol of 0.16mg/kg/min for 5minutes and its safety profile have been established in humans and it has been widely applied in many clinical and investigative studies including 15 O-water PET. With the use of the 3-min acquisition data, the regions of interest in the left ventricular chamber and myocardium could be set for all of the subjects. Six-min CFR data could be used to separate the CAD patients and controls. A 3-min, but not 2min, scan with 15 O-water PET can be used for the quantitative evaluation of MBF and CFR. A shorter scan time will result in a reduction of body motion of patients, which may lead to the more precise quantification of MBF and CFR.

Fusion Image of Coronary Artery and Myocardial Perfusion Using Computed Tomography

Fig 2. Cpain shows the total occlusion (Fig 1, arrows) in the proximal portion of the left ascending coronary artery (LAD). Stress perfusion cardiac magnetic resonance image (MRI) depicts endocardium hypoperfusion area in the LAD territory and late gadolinium enhancement MRI showed subendocardial infarction. In this case, fusion image of coronary computed tomography (CT) and perfusion CT can present coronary lesions and following myocardial ischemia precisely. Precoronary artery bypass grafting (CABG) epicardial image shows the hypoperfusion area in LAD territory (Fig 2A, arrows), and subendocardial image shows the severe hypoperfusion lesion (Fig 2B, arrows). Transmural ischemic changes that were mainly seen in the anteroseptal wall were improved in the epicardium (Fig 2C)