Toshiharu Himi

Prognostic Utility of Myocardial Blood Flow Assessed by N-13 Ammonia Positron Emission Tomography in Patients With Idiopathic Dilated Cardiomyopathy

Previous studies in patients with idiopathic dilated cardiomyopathy (IDC) have suggested that myocardial perfusion is impaired and spatially heterogeneous in such cases. Our objective was to identify any association between an abnormality in myocardial perfusion and the prognosis of patients with IDC. We collected data on N-13 ammonia positron emission tomography (PET) studies performed in 26 patients with IDC (9 nonsurvivors, 17 survivors) and in 8 normal control subjects. Regional myocardial blood flow (rMBF) was quantified using N-13 ammonia positron emission tomography and the Simple flow model. The spatial heterogeneity of myocardial perfusion was assessed by calculating the coefficient of variance of rMBF. Mean rMBF of the survivors was significantly lower (0.54 +/- 0.13 ml/min/g) than that of control subjects (0.66 +/- 0.06 ml/min/g) (p = 0.03 vs control), but did not differ significantly between nonsurvivors (0.58 +/- 0.15 ml/min/g) and control subjects. The coefficient of variance of rMBF was significantly higher in nonsurvivors than in either survivors or control subjects (0.24 +/- 0.08 vs 0.15 +/- 0.08, p = 0.007, and 0.16 +/- 0.05, p = 0.03, respectively). The probability of 3-year survival (Kaplan-Meier method) was 33.0% in subjects whose coefficient of variance of rMBF was above the median compared with 90.0% in subjects whose coefficient of variance of rMBF was below the median (p = 0.01). The probability of 3-year survival did not differ among subjects whose mean rMBF was above versus below the median (61.5% vs 62.9%, respectively). The results suggest that the prognosis of patients with IDC is associated with the spatial heterogeneity of myocardial perfusion, not with initial absolute rMBF.

Measurement of Arterial Tracer Concentrations from Cardiac Pet Images

Objective Cardiac PET imaging offers the potential capability for the noninvasive measurement of arterial input function. This capability is somewhat limited, however, because of partial volume and spillover effects. The purpose of this study was to validate arterial tracer concentration measurements using PET images by assigning a region of interest (ROI) to the left ventricle, left atrium (LA), and ascending aorta. Materials and Methods We selected [11C]CO and [13N]ammonia as tracers, because the activity of [11C]CO is primarily in the blood pool and that of [13N]amtnonia primarily in myocardial tissue. Six [11C]CO and 11 [13N]ammonia PET scans were obtained in 17 subjects. Arterial tracer concentrations determined by PET were compared with those measured by well counting of arterial blood sampling obtained at the midpoint of each image acquisition. Results Arterial tracer concentrations as determined by LA-PET imaging correlated closely with those measured by blood sampling (r = 0.996, slope = 1.00 for [11C]CO; r = 0.841, slope = 0.974 for [13N]ammonia). Partial volume and spillover effects were minimized by assigning an ROI to the LA. Conclusion Arterial tracer concentrations can be measured noninvasively with cardiac PET. Index Terms Emission computed tomography—Heart—Tracers—Emission computed tomography, techniques.

Prevalence and Clinical Features of Focal Takotsubo Cardiomyopathy

BACKGROUND Because it is difficult to distinguish between focal takotsubo cardiomyopathy and aborted myocardial infarction, there is little information about the prevalence and clinical features of focal takotsubo cardiomyopathy. METHODSANDRESULTS Our cardiac catheterization databases were queried to identify patients with focal takotsubo cardiomyopathy and other types of takotsubo cardiomyopathy. We defined focal takotsubo cardiomyopathy as hypo-, a- or dyskinesis in both anterolateral and septal segments without obstructive coronary artery disease explaining the wall motion abnormality. A total of 10 patients were diagnosed with focal takotsubo cardiomyopathy. The control group comprised patients with takotsubo cardiomyopathy with apical, mid-ventricular, or basal ballooning. Clinical features and in-hospital outcomes were compared between patients with focal takotsubo cardiomyopathy and those with other types of takotsubo cardiomyopathy. Among the 144 patients with takotsubo cardiomyopathy, the apical, mid-ventricular, basal, and focal types occurred in 85 (59.0%), 49 (34.0%), 0 (0%), and 10 patients (6.9%), respectively. The left ventricular ejection fraction was significantly higher in the focal group compared with the apical and mid-ventricular group (56±13 vs. 45±13 vs. 46±12%, P=0.03). In-hospital outcome was not significantly different among the 3 groups. CONCLUSIONS Focal takotsubo cardiomyopathy is not rare. Biplane left ventriculography is useful for its diagnosis. (Circ J 2016; 80: 1824-1829).

Functional evaluation of myocardial viability by99mTc tetrofosmin gated SPECT —A quantitative comparison with18F fluorodeoxyglucose positron emission CT (18F FDG PET)—

To validate functional analysis of gated SPECT in detecting myocardial viability, seventeen patients (male 15, female 2, mean age 58) with angiographically proven chronic ischemic heart disease (RCA 6, LAD 10, LCX 1) and eight normal volunteers (all male) were studied. All patients underwent18F FDG PET and99mTc tetrofosmin (TF) gated SPECT within a week. After being displayed in a polar map, myocardial perfusion was regionally determined by the mean count in 9 segments at end diastole (ED) and end systole (ES) in gated SPECT. Systolic function was determined by the count increase ratio from ED to ES (WTI: ES — ED/ED). Glucose metabolism was assessed by18F FDG PET in the segments correspondent to those defined for SPECT. TF %uptake of < 60% was defined as hypoperfusion, and FDG %uptake of < 50% was defined as reduced glucose metabolism. Results: The myocardial segments were classified into 3 categories: “normal” perfusion (n = 85), “mismatch” (reduced perfusion with reserved FDG uptake, n = 25) and “matched” reduced perfusion and metabolic reduction (n = 26). Mean WTI in “mismatch” segment was 0.38 ± 0.21, and was significantly greater than that in “matched reduced” segments, 0.15 ± 0.20 (p < 0.001). It was also greater than that in “normal” segments, 0.27 ± 0.16. Regression analysis showed that association between WTI and FDG %uptake was significant (r = 0.57, p < 0.0005) for the ischemic segments (“mismatch” + “matched”, n = 51), but the association was weak for the entire segments although it was statistically significant (r = 0.26, p = 0.02, n = 136). Conclusion: For the segments determined as infarct by perfusion image, systolic functional analysis by gated SPECT is helpful in differentiation of a viable myocardial region or artifact from a scar. Nevertheless, further clinical and technical assessment is required for ECG gating to eliminate overestimation of viability and to warrant clinical use.

Safety and Efficacy of Short-Time Compression with Kaolin-Filled Pad after Catheter Ablation

Background: Bleeding and vascular access site complications are an important cause of morbidity after percutaneous femoral procedures. The aim of this study was to evaluate the safety and efficacy of a novel hemostatic device for femoral closure after catheter ablation, in adjunct to short-time compression. Methods: Fourteen consecutive patients (57% male, mean age 64±12 years) undergoing catheter ablation of atrial fibrillation (50%), supraventricular tachycardia (36%), atrial flutter (7%) and premature ventricular contraction (7%) by femoral approach received arterial sheath and multiple venous sheath removal with the QuikClot gauze use. Results: The mean ACT value at hemostasis time was 288 s (range 200–319 s). Hemostasis was achieved in a mean time of 6.0±1.5 min. Only one patient suffered re-bleeding, who was administered aspirin, clopidogrel and warfarin concurrently. Neither major bleeding, nor hematoma occurred. Conclusions: QuikClot gauze could obtain prompt hemostasis. Attention needs to be paid with patients treated with aspirin, clopidogrel and warfarin concurrently.

Fast dynamic study in cardiac positron CT using 13N-ammonia in man

Fast dynamic studies with positron computed tomography (PCT) of the heart have been relatively few because of the technical limitations of prevalently used PCT devices. In the present study, we used a high-sensitivity, whole-body multislice PCT device (POSITOLOGICA-II) and performed serial 6-s PCT scans after the intravenous bolus injection of 13N-ammonia in 15 cardiac patients and 5 normal subjects. On the first image (0–6 s), 13N activity was primarily in the right atrium and ventricle. On the third image (12–18 s), it was primarily in the left atrium and ventricle. These blood-pool images permit evaluation of size and configuration of ventricles and atria in cardiac patients and normal subjects. Clearance of 13N activity in the blood pools and lungs occurred primarily during the 1st min. Thereafter, the myocardial images were delineated. In patients with heart failure, delayed clearance of the tracer from the blood pools and lungs was observed. The results indicate that initial passage of the tracer through the heart can be observed with the use of fast dynamic PCT.