Brain natriuretic peptide concentration in pericardial fluid is independently associated with atrial fibrillation after off-pump coronary artery bypass surgery.

OBJECTIVES: Postoperative atrial fibrillation is associated with the increased incidence of morbidities and mortality. Predisposing determinants of atrial fibrillation development after off-pump coronary artery bypass grafting remain unclear. We hypothesized that pericardial fluid natriuretic peptide concentrations have a predictive value for developing postoperative atrial fibrillation in patients who have undergone off-pump coronary artery bypass grafting. METHODS: We prospectively measured atrial natriuretic peptide and brain natriuretic peptide concentrations in plasma and pericardial fluid in 42 consecutive patients undergoing off-pump coronary artery bypass grafting, then continuously observed the occurrence of atrial fibrillation following off-pump coronary artery bypass grafting until the time of discharge. RESULTS: Postoperative atrial fibrillation was documented in nine patients (21%, atrial fibrillation group), and not in 33 patients (no atrial fibrillation group). Between the groups, there was neither significant difference in plasma atrial natriuretic peptide concentrations nor in pericardial atrial natriuretic peptide concentrations. Plasma brain natriuretic peptide concentrations were comparable in both groups [56.2 (interquartile range 42.7-102.8) vs. 35.2 pg/ml (13.8-75.0), P=0.07]. Pericardial fluid brain natriuretic peptide concentrations were significantly higher in the atrial fibrillation group than in the no atrial fibrillation group [188.0 (124.8-411.0) vs. 39.3 pg/ml (10.0-88.4), P=0.0001]. In a multivariable logistic regression model, pericardial brain natriuretic peptide concentration was significantly associated with a higher risk of postoperative atrial fibrillation (odds ratio=3.0 every 50 pg/ml increase; 95% confidence interval, 1.1-8.6; P=0.04). CONCLUSION: Our results suggested that pericardial fluid brain natriuretic peptide concentration is independently associated with the development of atrial fibrillation after off-pump coronary artery bypass grafting.

Mobile stenosis in a left internal mammary artery graft: a case report.

The authors report a case of percutaneous transluminal angioplasty (PTA) with coronary stent for stenosis in a left internal mammary artery (IMA) graft, which led to newly developed stenosis at both sides of the stent in the IMA graft. The intravascular ultrasound (IVUS) revealed that the stenotic lesion consisted of intramural hematoma, which had shifted owing to the stent deployment. They suggest that the cause of stenotic lesions in IMA grafts at the early postoperative period is luminal compression by intramural hematoma, which can be visualized by use of IVUS. The strategy of PTA for IMA grafts performed at the early postoperative period should include consideration for hematoma shift.

Detection of protein tyrosine phosphorylation by open sandwich fluoroimmunoassay.

In the era of proteomics, high-throughput screening of posttranslational modification states of proteins, especially protein phosphorylation, is considered of utmost importance. However, current protein phosphorylation detection methods depend on either the combination of proteolysis and mass spectrometry, or time-consuming immunoassay that requires inevitable washing processes. As a way to rapidly assay protein phosphorylation events, here we propose the use of Open Sandwich immunoassay that detects antigen-dependent stabilization of antibody variable region (Fv). As a model system, the heavy and light chain variable regions (V(H)/V(L)) of anti-phosphotyrosine antibody PY20 were used to evaluate its performance. When V(H)/V(L) interaction was first estimated by phage ELISA, wild-type Fv showed a modest phosphotyrosine (PY)-dependent increase in signal. However, after screening of mutants at an interface residue, one with weak V(H)/V(L) interaction (HQ39R) showed markedly improved (>200%) antigen-dependent signals. Using this mutant, two fusion proteins in which each variable region fragment was tethered to a GFP color variant were made (V(H)-eYFP/V(L)-eCFP) to monitor PY-induced fluorescence resonance energy transfer (FRET) between them. The results showed significant PY- or tyrosine phosphorylated peptide-induced enhancement in FRET in homogeneous solutions, indicating applicability of the method for rapid screening of tyrosine phosphorylation in vitro or in situ and possibly in vivo.

The role of interface framework residues in determining antibody V(H)/V(L) interaction strength and antigen-binding affinity.

While many antibodies with strong antigen-binding affinity have stable variable regions with a strong antibody heavy chain variable region fragment (V(H))/antibody light chain variable region fragment (V(L)) interaction, the anti-lysozyme IgG HyHEL-10 has a fairly strong affinity, yet a very weak V(H)/V(L) interaction strength, in the absence of antigen. To investigate the possible relationship between antigen-binding affinity and V(H)/V(L) interaction strength, a novel phage display system that can switch two display modes was employed. We focused on the two framework region 2 regions of the HyHEL-10 V(H) and V(L), facing each other at the domain interface, and a combinatorial library was made in which each framework region 2 residue was mixed with that of D1.3, which has a far stronger V(H)/V(L) interaction. The phagemid library, encoding V(H) gene 7 and V(L) amber codon gene 9, was used to transform TG-1 (sup+), and the phages displaying functional variable regions were selected. The selected phages were then used to infect a nonsuppressing strain, and the culture supernatant containing V(H)-displaying phages and soluble V(L) fragment was used to evaluate the V(H)/V(L) interaction strength. The results clearly showed the existence of a key framework region 2 residue (H39) that strongly affects V(H)/V(L) interaction strength, and a marked positive correlation between the antigen-binding affinity and the V(H)/V(L) interaction, especially in the presence of a set of particular V(L) residues. The effect of the H39 mutation on the wild-type variable region was also confirmed by a SPR biosensor as a several-fold increase in antigen-binding affinity owing to an increased association rate, while a slight decrease was observed for the single-chain variable region.

Magnetic resonance imaging differentiated partial from complete absence of the left pericardium in a case of leftward displacement of the heart.

A 44-year-old man was referred to hospital for the evaluation of atypical chest pain. His chest X-ray showed leftward displacement of the heart. During echocardiography, the apical window displaced laterally in the usual left lateral position and characteristic motions of the interventricular septum and left ventricular posterior wall were recognized with postural alterations. We presumed a complete absence of the left pericardium. Magnetic resonance imaging (MRI), however, demonstrated a partial left-sided pericardium. The diagnosis was corrected to partial absence of the left pericardium and we have carefully followed up this case without surgical prophylactic intervention. It is very important to differentiate partial from complete absence of the pericardium, because only in patients with partial absence of the pericardium is there a risk of fatal myocardial strangulation. The features of the chest X-ray and echocardiography of this case, which strongly suggested complete absence of the left pericardium, are possibly not always reliable signs. In cases with these abnormal imaging features, MRI may provide additional useful information, as in this case.

Identification of exercise-induced left ventricular systolic and diastolic dysfunction using gated SPECT in patients with coronary artery disease.

BACKGROUND: We investigated whether poststress left ventricular dysfunction in patients with coronary artery disease may be confirmed at 30 minutes after exercise using newly modified quantitative gated single photon emission computed tomography (QGS) software that can evaluate systolic and diastolic function. METHODS AND RESULTS: In this study 28 control subjects, 26 patients with angina pectoris (AP), and 27 patients with old myocardial infarction (MI) who had undergone revascularization were included. Same-day exercise/rest gated technetium 99m tetrofosmin single photon emission computed tomography was performed. QGS was used with a temporal resolution of 32 frames per R-R interval, and a left ventricular volume curve was reconstructed. From the fitted volume curve and its first derivative curve, we derived the ejection fraction (EF), peak ejection rate (PER), peak filling rate (PFR), and time to PFR (TPFR). In patients with AP and MI, the values for EF, PER, and PFR were lower after stress than at rest. TPFR was significantly prolonged in patients with MI after stress. In control subjects, EF, PER, PFR, and TPFR were not changed. CONCLUSIONS: Modified QGS software successfully indicated the changes in systolic and diastolic function. In patients with AP and MI, poststress systolic and diastolic dysfunction was identified 30 minutes after exercise.

A general method to select antibody fragments suitable for noncompetitive detection of monovalent antigens.

Previously, immunological detection of a small hapten was only possible in competitive format, which needed a competitor antigen either labeled by a reporter or attached to a carrier protein. Recently, we proposed the open sandwich (OS) immunoassay, a simple immunoassay that can noncompetitively determine monovalent antigen concentration by measuring the antigen-dependent change in a heavy-chain variable region (VH)/light-chain variable region (VL) interaction of an antibody. However, there was a limitation in the assay that the antibody used should have a suitable property such that the VH/VL interaction would become fairly strong along with the addition of antigen. Here, we devised a phage-based "split-Fv system" to rapidly evaluate and select antibody variable region (Fv) fragments that are suitable to OS immunoassay. When three antibodies raised against endocrine disruptor bisphenol A were tested with this system, all were more or less suitable to OS-ELISA. Among them, the best Fv selected was used to construct fusion proteins of VH tethered to an alkaline phosphatase and a tagged VL that can be site-specifically biotinylated to perform direct OS-ELISA. The results showed that the OS-ELISA detects bisphenol A with higher sensitivity than the corresponding competitive assay, also implying that many antibodies to small haptens have suitable properties for OS-ELISA.

Assessment of left ventricular diastolic function by gated single-photon emission tomography: comparison with Doppler echocardiography.

Gated single-photon emission tomography (SPET) is not yet an established procedure for the evaluation of left ventricular (LV) diastolic function. This study examined diastolic function derived from gated SPET in comparison with an established diagnostic tool, Doppler echocardiography. We examined 37 consecutive patients with normal sinus rhythm who underwent gated technetium-99m tetrofosmin SPET. A gated SPET program was used with a temporal resolution of 32 frames per R-R interval. We obtained the Doppler transmitral flow velocity waveform immediately before gated SPET image acquisition. Patients who showed a ratio of peak early transmitral flow velocity to atrial flow velocity (E/A) of >1 or whose R-R intervals differed by >5% between Doppler echocardiography and gated SPET were excluded from this investigation. We compared diastolic indices and presumed corresponding intervals in diastole using the two methods. The peak filling rate (PFR) derived from gated SPET correlated with the Doppler peak velocity of the early transmitral flow (E) wave ( r=0.65) and deceleration of the E wave ( r=0.71). The time to PFR and percent atrial contribution to LV filling from gated SPET correlated excellently with the Doppler LV isovolumic relaxation time ( r=0.93) and the E/A ratio ( r=-0.85), respectively. There was a significant linear correlation in all the intervals from the R wave to the presumed corresponding diastolic points. The point of PFR in gated SPET and the peak of the E wave in Doppler echocardiography generally coincided. The onset of filling in gated SPET tended to be closer to the second heart sound than the start of the E wave in Doppler echocardiography. We conclude that gated SPET permits the assessment of not only myocardial perfusion and LV systolic function but also diastolic function, although there may be some errors in detection of the precise beginning of LV filling.

Increased plasma brain natriuretic peptide level as a guide for silent myocardial ischemia in patients with non-obstructive hypertrophic cardiomyopathy.

OBJECTIVES: We measured plasma atrial/brain natriuretic peptide (ANP/BNP) levels at rest and during exercise and correlated the results with various clinical findings, particularly with myocardial ischemia, in asymptomatic hypertrophic cardiomyopathy (HCM). BACKGROUND: In patients with HCM, ANP and BNP levels are elevated and exercise-induced myocardial ischemia is common. However, it has not yet been elucidated how these levels at rest and their change with dynamic exercise are related to ischemia. METHODS: Levels of ANP and BNP were measured at rest and at peak exercise during (99m)Tc-tetrofosmin scintigraphy in 31 asymptomatic patients with non-obstructive HCM and in 10 control subjects. RESULTS: Levels of ANP and BNP at rest and the change of ANP and BNP levels (PG/ML) from rest to exercise were significantly greater in HCM than in control subjects (ANP: rest, 53.2 +/- 31.8 vs. 11.6 +/- 6.1; exercise, 114.5 +/- 74.8 vs. 28.3 +/- 23.4. BNP: rest, 156.7 +/- 104.1 vs. 9.8 +/- 9.6; exercise, 201.6 +/- 131.5 vs. 13.2 +/- 14.5). Septal perforator compression (SPC) and exercise-induced ischemia were observed, respectively, in 20 (64.5%) and in 19 (61.3%) patients with HCM. The increment of ANP during exercise was similar between HCM subgroups with or without inducible ischemia. However, BNP levels at rest and BNP increments during exercise were significantly greater in the HCM subgroup with inducible ischemia than in the subgroup without (rest, 190.5 +/- 116.2 vs. 103.1 +/- 48.3; exercise, 250.5 +/- 142.2 vs. 124.2 +/- 58.6). Multiple logistic regression analysis revealed that SPC and BNP levels at rest were independently associated with exercise-induced ischemia. CONCLUSIONS: Measurement of plasma BNP levels at rest may be useful in predicting silent myocardial ischemia in HCM.