Kaoru Komuro

Novel quantitative assessment of myocardial perfusion by harmonic power Doppler imaging during myocardial contrast echocardiography

Objective: To test the hypothesis that the power of the received signal of harmonic power Doppler imaging (HPDI) is proportional to the bubble concentration under conditions of constant applied acoustic pressure, and to determine whether a new quantitative method can overcome the acoustic field inhomogeneity during myocardial contrast echocardiography (MCE) and identify perfusion abnormalities caused by myocardial infarction. Methods: The relation between Levovist concentration and contrast signal intensity (CI) of HPDI was investigated in vitro under conditions of constant acoustic pressure. MCE was performed during continuous infusion of Levovist with intermittent HPDI every sixth cardiac cycle in 11 healthy subjects and 25 patients with previous myocardial infarction. In the apical views myocardial CI (CImyo) was quantified in five myocardial segments. The CI from the left ventricular blood pool adjacent to the segment was also measured in dB and subtracted from the CImyo (relative CI (RelCI)). Results: CI had a logarithmic correlation and the calculated signal power a strong linear correlation with Levovist concentration in vitro. Thus, a difference in CI of X dB indicates a microbubble concentration ratio of 10X/10. In normal control subjects, CImyo differed between the five segments (p < 0.0001), with a lower CImyo in deeper segments. However, RelCI did not differ significantly between segments (p  =  0.083). RelCI was lower (p < 0.0001) in the 39 infarct segments (mean (SD) −18.6 (2.8) dB) than in the 55 normal segments (mean (SD) −15.1 (1.6) dB). RelCI differed more than CImyo between groups. Conclusions: The new quantitative method described can overcome the acoustic field inhomogeneity in evaluation of myocardial perfusion during MCE. RelCI represents the ratio of myocardium to blood microbubble concentrations and may correctly reflect myocardial blood volume fraction.

Increased plasma concentrations of N-terminal pro-brain natriuretic peptide reflect the presence of mildly reduced left ventricular diastolic function in hypertension.

BackgroundThe potential use of assays of N-terminal pro-brain natriuretic peptide for detection of diastolic abnormalities associated with alterations in blood pressure has not been elucidated. This study was designed to determine whether increased plasma concentrations of N-terminal pro-brain natriuretic peptide sensitively reflect abnormal diastolic function associated with hypertension. MethodsConcentrations of N-terminal pro-brain natriuretic peptide in plasma were assayed in 40 previously untreated hypertensive patients without overt congestive heart failure and in 20 age and sex-matched controls. Hypertensive patients were studied with the use of pulsed Doppler and color M-mode Doppler echocardiography for the evaluation of left ventricular diastolic function. ResultsConcentrations of N-terminal pro-brain natriuretic peptide were elevated in hypertensive patients [75.1±75.2 (SD) pg/ml compared with 37.9±38.5 in controls, P<0.05]. In hypertensive patients, concentrations of N-terminal pro-brain natriuretic peptide were negatively correlated with the ratio of color M-mode flow propagation velocity to transmitral E velocity consistent with the view that increased concentrations of N-terminal pro-brain natriuretic peptide are indicative of alterations in diastolic function. Hypertensive patients with N-terminal pro-brain natriuretic peptide values above the mean value in the control group exhibited significantly increased brachial intimal–medial thickness and reduced wall stress, consistent with the view that increased N-terminal pro-brain natriuretic peptide was associated with favorable peripheral arterial remodeling. ConclusionsElevated concentrations of N-terminal pro-brain natriuretic peptide in plasma reflect the presence of left ventricular diastolic abnormalities and peripheral arterial remodeling in asymptomatic patients with hypertension.

Integrated backscatter for the assessment of myocardial viability.

Purpose of review Ultrasonic tissue characterization is a non-invasive diagnostic method that uses myocardial integrated backscatter analysis to determine contractile performance and myocardial viability independent of wall motion. This review discusses recent clinical findings regarding the application of ultrasonic tissue characterization for the assessment of myocardial viability. Recent findings As this technique is non-invasive, ultrasonic tissue characterization can be used to predict the patency of infarct-related arteries in patients in the early stage of acute myocardial infarction. Several recent studies have shown that this technique is useful in identifying myocardial contractile reserve. The accuracy of ultrasonic tissue characterization for predicting functional recovery after coronary reperfusion is comparable to dobutamine echocardiography and radionuclide methods. Several studies have suggested that the cyclic variation of myocardial integrated backscatter reflects myocardial viability rather than contractile reserve. The cyclic variation of integrated backscatter is associated with myocardial viability confirmed by the integrity of the microvasculature identified by contrast echocardiography. In addition, the cyclic variation of integrated backscatter better reflects myocardial viability confirmed by the integrity of cellar metabolism than contractile reserve. Summary Ultrasonic tissue characterization with integrated backscatter is a useful non-invasive method that can provide unique information for the assessment of myocardial viability.

A fundamental study for quantitative measurement of ultrasound contrast concentration by low mechanical index contrast ultrasonography

PurposeIn high mechanical index (MI) contrast ultrasonography it has been shown that the power of contrast signal intensity (CI) has a strong linear correlation with the concentration of the ultrasound contrast agent under conditions of constant applied acoustic pressure. However, it is unclear whether the linearity is preserved in low-MI contrast ultrasonography. Thus, we investigated the relationship between ultrasound contrast concentration and CI in vitro.MethodsSolutions of the ultrasound contrast agents Definity and Imagent were prepared at concentrations of 0.5, 2, 8, 32, and 128 μl/l. Placing a jelly block between the transducer and the solution, the solutions were transmitted using pulse subtraction imaging with an MI of 0.05, 0.1, and 0.5. CI was measured in dB in a region of interest 3 mm in height placed just below the border between the jelly and the solution. Data were plotted using double logarithm scales, where the concentration was expressed in dB as 10 × log (concentration).ResultsCI in dB had a strong linear correlation with concentration in dB for both agents with any MI. Best fitted slopes were close to 1, indicating that the power of CI is proportional to the concentration.ConclusionsIn low-MI contrast ultrasonography, the power of CI is proportional to contrast concentration, and CI in dB is logarithmic to the concentration. Thus, the microbubble concentration can be quantitatively measured even in low-MI contrast ultrasonography.

Apicoaortic Valved Conduit for a Patient with Porcelain Aorta

A 69-year-old woman had severe aortic stenosis with a circumferentially calcified aorta from the ascending aorta to the aortic arch, and moderately impaired left ventricular function. Implantation of an apicoaortic valved conduit was performed as aortic clamping was not feasible. The early results were excellent.

Measuring Medium-Sized Muscular Arteries Using a Novel Broadband 15-MHz Linear Array Probe

We recently developed a wideband 15-MHz linear array probe (15 M) with a band width of 8 MHz (9–17 MHz). Both axial and lateral resolution of 15 M, evaluated using a phantom model, were better than those of the current 10-MHz linear probe. To compare interobserver variability in measurement of medium-sized muscular arteries acquired using a 7.5-MHz linear probe (7.5 M), a 10-MHz linear probe (10M) and 15 M, two observers independently acquired images of the brachial and radial arteries, and measured the diameter and intima-media thickness (IMT) of those arteries in 17 male volunteers. Intraobserver variability in determining percent flowmediated dilatation (%FMD) was assessed in the same subjects using 15 M. Coefficients of variation (CV) in arteries measured using 7.5 M, 10 M, and 15 M were 7.0%, 2.5%, and 1.5%, respectively, for the diameter of the brachial artery; 10.3%, 5.8%, and 3.2%, respectively, for the diameter of the radial artery; and 17.0%, 13.8%, and 8.5%, respectively, for IMT of the far wall of the brachial artery. The CV of measurement of %FMD was 4.6%. The new 15-MHz probe thus warrants use in evaluating morphology and function of muscular arteries of medium size.

Left ventricular noncompaction with intractable heart failure responsive to empagliflozin

Despite several reports on the mechanism of the effect of empagliflozin, which has the potential for improved prognosis in heart failure, it is still not fully understood. We experienced a case of left ventricular noncompaction that caused fluid retention in a patient who showed resistance to existing diuretics. By using empagliflozin, we successfully treated this case of acute heart failure and observed stabilized symptoms with no renal dysfunction and deterioration of patient condition. Although the potential for improved prognosis with this drug in a high-risk group for cardiovascular events has been reported, based on EMPA-REG OUTCOME trial results, there are few reports on its effect of treatment and mechanism in treating acute heart failure. The effect of this drug in treating heart failure from the acute phase to the chronic phase can be expected. <Learning objective: Empagliflozin is a drug that works from the acute phase and is effective from the acute phase to the chronic phase, in treating intractable heart failures that demonstrate resistance to existing drug treatments.>.

A Fundamental Study for Quantitative Measurement of Ultrasound Contrast Concentration by Low Mechanical Index Contrast Ultrasonography

目的 : 高音圧コントラストエコー法において, 局所の入射音圧が一定である条件下では造影剤濃度とコントラスト強度 (CI) のパワー値の間に良好な線形性があることが分かってきた. しかし, 低音圧コントラストエコー法でも同様の線形性が保たれるか否かは不明である. そこで, 低音圧コントラストエコー法における造影剤濃度とCIとの関係を確認するためにin vitro実験を行った. 方法 : 造影剤はDefinity®とImagent®の2種類を用いた. 0.5, 2, 8, 32, 128μL/Lの5濃度の溶液を用意し, mechanical index (MI) 0.05, 0.1, 0.5のパルスサブトラクションイメージングで, ゼリーを介して溶液を撮像した. 画像上の溶液の水面直下に厚さ3mmの関心領域を置き, CIをdBで計測した. 濃度は0.5μL/Lを基準値として10×log (濃度) でdB表示し, 両側対数グラフ上で直線回帰分析を行った. 結果 : 両造影剤とも, いずれのMIにおいても, 造影剤濃度とCIとはきわめて良好な直線相関を示し, 回帰直線の傾きはCIのパワー値が造影剤濃度に比例する場合の理論値1に近かった. 結語 : 低音圧コントラストエコー法においても, CIのパワー値が造影剤濃度に比例し, CIのdB値は濃度に対して対数関係にある. 低音圧コントラストエコー法で気泡密度の定量計測が可能である.