Hiromi Shimizu

Comparative usefulness of myocardial velocity gradient in detecting ischemic myocardium by a dobutamine challenge.

OBJECTIVES We tested the hypothesis that ischemic myocardium can be sensitively detected using tissue Doppler-derived myocardial velocity gradient (MVG) by a dobutamine challenge. BACKGROUND Although tissue Doppler imaging (TDI) has recently emerged to quantify regional myocardial contraction, increased translational motion during a dobutamine challenge may affect the measurements. MVG is an indicator of regional myocardial contraction independent of the translational motion. METHODS We studied 19 patients with (n = 13) and without (n = 6) confirmed single-vessel coronary artery disease. Left ventricular short-axis tissue Doppler images were obtained along with conventional echocardiograms during a submaximal two-step dobutamine challenge (10 and 30 microg/kg body weight per min). Endocardial velocity as well as MVG were derived from TDI using computer analysis in the anteroseptal and posterior segments and were compared with visual interpretation. RESULTS MVG demonstrated a significant dose-responsive increase in the nonischemic segments (anteroseptal: 2.6 +/- 0.8/s to 6.0 +/- 1.0/s [mean +/- SD], p < 0.05; posterior: 3.9 +/- 0.7/s to 7.6 +/- 1.8/s, p < 0.05) but remained unchanged in the ischemic segments (anteroseptal: 2.5 +/- 0.8/s to 2.7 +/- 0.7/s, p = NS; posterior: 3.4 +/- 1.0/s to 4.1 +/- 0.9/s, p = NS). Endocardial velocity failed to clearly demonstrate the differing responses between the nonischemic (anteroseptal: -2.3 +/- 1.2 to -2.7 +/- 1.6 cm/s, p = NS; posterior: 3.8 +/- 1.1 to 73 +/- 2.7 cm/s, p < 0.05) and ischemic segments (anteroseptal: -2.1 +/- 0.5 to -2.8 +/- 0.8 cm/s, p = NS; posterior: 4.2 +/- 0.8 to 6.5 +/- 2.6 cm/s, p = NS). Wall motion abnormality was hardly detectable with visual interpretation (wall motion score range 1.00 to 1.33). CONCLUSIONS Abnormal segments could be sensitively detected by using MVG in a submaximal dobutamine challenge, even where conventional methods failed to detect the abnormality.

Peak negative myocardial velocity gradient in early diastole as a noninvasive indicator of left ventricular diastolic function: Comparison with transmitral flow velocity indices

OBJECTIVES We sought to assess the clinical significance of peak negative myocardial velocity gradient (MVG) in early diastole as a noninvasive indicator of left ventricular (LV) diastolic function. BACKGROUND Peak systolic MVG has been shown useful for the quantitative assessment of regional wall motion abnormalities, but limited data exist regarding the diastolic MVG as an indicator of LV diastolic function. METHODS Peak negative MVG was obtained from M-mode tissue Doppler imaging (TDI) in 43 subjects with or without impairment of systolic and diastolic performance: 12 normal subjects, 12 patients with hypertensive heart disease (HHD) with normal systolic performance and 19 patients with dilated cardiomyopathy (DCM), and was compared with standard Doppler transmitral flow velocity indices. In a subgroup of 30 patients, effects of preload increase on these indices were assessed by performing passive leg lifting. In an additional 11 patients with congestive heart failure at the initial examination, the measurements were repeated after 26+/-16 days of volume-reducing therapy. RESULTS Peak negative MVG was significantly depressed both in HHD (-3.9+/-1.3/s, p < 0.01 vs. normal=-7.7+/-1.5/s) and DCM (-4.4+/-1.4/s, p < 0.01 vs. normal). In contrast, transmitral flow indices failed to distinguish DCM from normal due to the pseudonormalization. Transmitral flow velocity indices were significantly altered (peak early/late diastolic filling velocity [E/A]=1.1+/-0.5 to 1.5+/-0.7, p < 0.01; E deceleration time=181+/-41 to 153+/-38 ms, p < 0.01), while peak negative MVG remained unchanged (-5.3+/-2.2 to -5.3+/-2.0/s, NS) by leg lifting. Volume-reducing therapy resulted in the apparent worsening of the transmitral flow velocity pattern toward abnormal relaxation, as opposed to peak negative MVG, which improved by the therapy (p < 0.05). CONCLUSIONS Peak negative MVG derived from TDI may be a noninvasive indicator of LV diastolic function that is less affected by preload alterations than the transmitral flow velocity indices, and thereby could be used for the follow-up of patients with nonischemic LV dysfunction presenting congestive heart failure.

Improved Visualization of the Left Atrial Appendage by Transthoracic 2-Dimensional Tissue Harmonic Compared with Fundamental Echocardiographic Imaging ☆ ☆☆ ★

We compared fundamental and tissue harmonic transthoracic echocardiographic imaging for the delineation of the left atrial appendage (LAA) in 32 subjects. The LAA images recorded in the parasternal short-axis view were divided into 4 segments and 2 observers independently graded for each segment using a visual scoring system ranging from 0 to 3 (0 = no, 3 = clearly visible over the entire length of the segment). For the 128 segments, the averaged segment scores were significantly increased after switching to harmonic imaging (1.32 +/- 0.69 versus 1.60 +/- 0.81 for fundamental and tissue harmonic imaging, respectively; P <.0005 for observer 1, and 1.38 +/- 0.65 versus 1.61 +/- 0.82, respectively; P <.001 for observer 2). In a patient with LAA thrombus, the image contrast of the thrombus was improved in harmonic compared with fundamental imaging. These data suggest that tissue harmonic imaging significantly improves image quality of the LAA.

An inhibitor of inducible nitric oxide synthase decreases forearm blood flow in patients with congestive heart failure

OBJECTIVES The functional activation of inducible nitric oxide synthase (iNOS) was evaluated as a source of nitric oxide (NO) in the forearm of patients with heart failure. BACKGROUND Although endogenous NO is normally produced by constitutive NO synthase (cNOS) in patients with congestive heart failure (CHF), expression of iNOS provides an additional source of NO. However, there are no in vivo studies showing functional activation of iNOS in humans. METHODS A nonselective NOS inhibitor, N(G)-monomethyl-L-arginine (L-NMMA), and a selective inhibitor of iNOS, aminoguanidine, were administered intra-arterially in graded doses into the brachial arteries of 13 patients with CHF and 10 normal control subjects. Forearm blood flow (FBF) was measured simultaneously in the infused and noninfused arms by plethysmography. Arterial and venous plasma concentrations of nitrite/nitrate (NOx) were measured at baseline and at the highest dose of each drug. RESULTS L-NMMA significantly reduced the FBF ratio between the infused and noninfused arms in both the control and patient groups (35 +/- 12% and 34 +/- 10%, respectively; both p < 0.001). Aminoguanidine at the same concentration significantly reduced the ratio in the patient group (15 +/- 9%, p < 0.01), with no change in the control group. The arterial NOx concentration was not affected by either drug; however, venous NOx concentrations were significantly decreased in both the control and patient groups by L-NMMA (18 +/- 5% and 18 +/- 17%, respectively; both p < 0.05) and in the patient group only by aminoguanidine (7 +/- 6%, p < 0.05). CONCLUSIONS These findings suggest that NO production in the forearms of patients with CHF is induced partly by iNOS activation, whereas in normal subjects, it can be ascribed to cNOS activation.

Doppler estimation of pulmonary artery end-diastolic pressure using contrast enhancement of pulmonary regurgitant signals

Pulmonary artery (PA) end-diastolic pressure is used as an estimate of PA wedge pressure. We evaluated contrast enhanced pulmonary regurgitant signals in the assessment of PA end-diastolic pressure in 24 patients in a critical care unit. Right atrial pressure was estimated by the percent decrease of the inferior vena caval diameter with inspiration. Weak or absent pulmonary regurgitant signals were enhanced by sonicated albumin (Albunex) in 23 patients (96%). The Doppler-determined PA end-diastolic pressure (the sum of the pulmonary regurgitant pressure gradient at end-diastole and the right atrial pressure) was significantly correlated with the catheter-determined PA end-diastolic pressure (y = 0.85x + 1.72, r = 0.93). Compared with invasive hemodynamic monitoring, the contrast-enhanced Doppler technique using Albunex is effective for measuring PA end-diastolic pressure, even in critically ill patients.

Nitric oxide-mediated vasodilatory effect of atrial natriuretic peptide in forearm vessels of healthy humans.

1. The aim of the present study was to determine whether the vasorelaxant effect of atrial natriuretic peptide (ANP) is, in part, endothelium dependent in humans.

Usefulness of Low Doses of Atropine to Quantify the Vagal Stimulus-Response Relation in Patients With Congestive Heart Failure☆

The response of low doses of atropine is reported to be attenuated in patients with congestive heart failure (CHF). Judging from the main site of action of low doses of atropine, we may be able to assess the functional state of the vagal center in the central nervous system. This study examines the clinical significance of heart rate (HR) response to a low dose of atropine in patients with CHF. Low and high doses of atropine were administered intravenously in 72 patients with CHF. HR after a low (parasympathomimetic) dose injection was assessed by the ratio Rm (minimal HR/basal HR), and after a high (parasympatholytic) dose by the ratio R1 (augmented HR/basal HR). Rm and R1 were related to indexes of CHF. Rm increased with progression of CHF (0.92 +/- 0.03 in New York Heart Association functional class I, 0.98 +/- 0.05 in class II, and 1.00 +/- 0.04 in class III). It also correlated with ejection fraction (r = -0.48, p <0.01) and more importantly, with peak oxygen uptake (r = -0.59, p <0.01). R1 exhibited weak correlation with basal HR (r = -0.33, p <0.05) and ejection fraction (r = 0.31, p <0.05), but had no correlation with other indexes. The vagal center may be already blunted in New York Heart Association class II with respect to increased Rm, which may be related to depressed exercise capacity. A low dose of atropine injection offers a simple and safe method for providing important information on the functional state of the vagal center in the central nervous system in patients with CHF.

Improved definition of left atrial thrombus by tissue harmonic imaging

Harmonic imaging is one of the newest echocardiographic imaging techniques enabled by the recent development of newer broadband transducers used to detect harmonic frequencies, which are multiples of the transmitted frequency. Tissue harmonic imaging is useful to improve the definition of left ventricular endocardial borders. 1-5 We describe a case in which the technique facilitated the transthoracic diagnosis of a left atrial thrombus difficult to detect by fundamental imaging.

Left atrial appendage function in patients with single-chamber ventricular pacing.

Abstract In conclusion, left atrial appendage dysfunction may occur in VVI pacing with persistent retrograde ventriculoatrial conduction, and offers a potential explanation for an increased risk of thrombus formation.

Detection of coronary blood flow associated with right coronary ostial stenosis by means of transthoracic Doppler echocardiography

We report a case of ostial stenosis of the right coronary artery. Transthoracic echocardiography combined with Doppler flow velocity measurement and color flow imaging allowed noninvasive evaluation of disordered flow caused by stenosis.