Jun Watanabe

Increased von Willebrand Factor in the Endocardium as a Local Predisposing Factor for Thrombogenesis in Overloaded Human Atrial Appendage

OBJECTIVES We investigated immunoreactive von Willebrand factor (vWF), a platelet adhesion molecule, in the endocardial endothelium and its relationship to thrombogenesis in the human atrial appendage. BACKGROUND Intra-atrial thrombogenesis is generally thought to be induced by blood stasis in the atrial appendage involved with atrial fibrillation (AF). Little attention has been paid to alterations of the endocardial endothelium on which the thrombus develops. METHODS Atrial appendage tissue was obtained at heart surgery or at autopsy from AF and non-AF cardiac patients and from noncardiac patients. Immunohistochemistry for endothelial cell markers including vWF, CD31, CD34 and endothelial nitric oxide synthase (eNOS) and platelet glycoprotein Ib/IX or IIb/IIIa was performed and semiquantitatively graded. RESULTS In contrast to the apparent immunostaining for CD31, CD34 and eNOS, only focal or little immunoreactive vWF was seen in the endocardium of noncardiac patients. Immunoreactive vWF in the endocardial endothelium was increased in most cardiac patients, particularly in the left, but not in the right, atrial appendage of patients with mitral valvular disease, irrespective of whether AF was present. Platelet adhesion/thrombus formation in the endocardium was found in limited sites in which the overlying endothelium was deficient in eNOS and CD34. When warfarin-treated cases were excluded, there was a significant correlation between the immunohistochemical grade for vWF and the degree of platelet adhesion/thrombus formation in the endocardium. CONCLUSIONS Immunoreactive vWF in the endocardial endothelium was increased in overloaded human atrial appendage, which may be a local predisposing factor for intraatrial thrombogenesis.

Modification of myogenic intrinsic tone and [Ca2+]i of rat isolated arterioles by ryanodine and cyclopiazonic acid.

The role of the sarcoplasmic reticulum (SR) in regulating myogenic tone and [Ca2+]i was examined with ryanodine and cyclopiazonic acid (CPA) in the rat skeletal muscle arteriole (A(sk)) and mesenteric arteriole (Ams). Arterioles were cannulated at both ends to control luminal pressure in a tissue bath. Luminal diameter was measured with a video-monitored microscopic system. Fura 2-AM was loaded to measure [Ca2+]i using the fluorescence intensity ratio at excitation wavelengths of 340 to 380 nm (F340/380). The myogenic response (luminal pressure was increased from 40 to 100 mm Hg) and the intrinsic tone at 40 mm Hg were observed in A(sk) but not in Ams. Ryanodine (10(-5) M decreased the steady-state diameter of A(sk) from 138 +/- 8 to 85 +/- 9 microns (P < .05) and increased the F340/380 ratio; these effects were reversed by nifedipine or Ca(2+)-free solution. Ryanodine shifted the [Ca2+]o-contraction response curve upward. CPA (10(-5) M) also decreased the steady-state diameter of A(sk) from 131 +/- 7 to 98 +/- 11 microns (P < .05). In contrast, Ams responded to neither ryanodine nor CPA. Caffeine-induced contractions were significantly reduced by either ryanodine or CPA in both arterioles. These results indicate that SR dysfunction increased the susceptibility of the arteriolar tone to [Ca2+]o and enhanced the tone of A(sk). In conclusion, the SR function may play a critical role in regulating [Ca2+]i and the intrinsic tone of A(sk) that was myogenically active at physiological luminal pressure.

Microvolt T Wave Alternans in Human Cardiac Hypertrophy: Electrical Instability and Abnormal Myocardial Arrangement

T Wave Alternans and Hypertrophy. Introduction: Although T wave alternans (TWA) is a promising risk marker for myocardial electrical instability, it remains unclear how the presence of TWA is related to myocardial damage.

Normal and oxidized low density lipoproteins accumulate deep in physiologically thickened intima of human coronary arteries.

Diffuse intimal thickening (DIT) that develops as a physiologic adaptation in the arterial wall has been implicated to have a predilection for atherosclerosis. We histologically investigated the lipid accumulation process in the human coronary DIT by focusing on the localization of normal and oxidized low-density lipoproteins (LDLs). Immunohistochemistry for apolipoprotein B 100 (a major apolipoprotein of LDL) and 8-iso-prostaglandin F2α (an oxidative product in LDL) showed substantial accumulation of oxidized relative to normal LDLs in the deep layers of DIT (52/139 segments). Subendothelial deposition of normal rather than oxidized LDLs, known as an early event of fatty streak formation, was less frequently found (13/139 segments). In contrast with fibrofatty lesions, lipid accumulation localized deep in DIT was characterized by fine lipid droplets scattered in the preserved tissue and by its association with neither macrophage accumulation nor apoptosis in the constituent cells. On the other hand, the deep intimal location of lipid accumulation clearly coincided with increased type I and type III collagen and elastic fibers but rarely with sulfated proteoglycans including decorin, which were all strongly expressed in advanced lesions. This lipid accumulation was found only in sites with DIT of more than 200 μm, occasionally extending to the inner media and involving neovessel formation around it. The presence of deep intimal lipid accumulation was associated with reduced endothelium-dependent relaxation to substance P in isolated coronary rings. These results suggest that normal and oxidized LDLs accumulate preferably in the nutritional border zone of established DIT involving local extracellular matrix alterations but independently of inflammatory or apoptotic processes. This may contribute to the functional and morphologic abnormalities seen in human coronary atherogenesis that progresses slowly with age.

Effects of afterload reduction on global left ventricular and regional myocardial functions in the isolated canine heart with stenosis of a coronary arterial branch.

We examined the effects of graded reduction of afterload on the global left ventricular and regional myocardial functions as well as coronary hemodynamics in hearts with regional ischemia. We used isolated, paced canine hearts that were loaded with a hydraulic system that simulated the aortic input impedance of the dogs arterial tree. The loading conditions could be quantitatively and sequentially changed by the reduction of the systemic vascular resistance of the hydraulic system, while the preload was kept constant using a variable-height reservoir connected to the left atrium. The heart was perfused with arterial blood from a support dog. Mean coronary perfusion pressure was maintained equal to mean aortic pressure (AoP) by a servo-controlled pump. Then, the left circumflex branch was constricted to an approximate 50% flow reduction of the preischemic control condition. The myocardial lengths at ischemic and nonischemic regions were measured with two pairs of ultrasonic crystals.In the hearts without ischemia, cardiac output continued to increase, from 535 ± 14 to 1181 ± 74 ml/min (p < 0.01), as mean AoP decreased from 111 ± 4 to 52 ± 3 mm Hg (p < 0.01), although mean coronary blood flow decreased by approximately 50 %. During regional ischemia, at control pressures, performance of the ischemic region diminished from 0.94 ± 0.15 to 0.77 ± 0.15 mm (p < 0.05). With a small decrease in afterload, from 98 ± 6 to 86 ± 3 mm Hg, performance improved slightly as in the normal region. With a larger reduction in afterload, from 86 ± 3 to 55 ± 6 mm Hg, performance of the ischemic region decreased from 0.77 ± 0.15 to 0.61 ± 0.15mm (p < 0.05) while cardiac output increased. Thus, there appears to be a bimodal change in performance: a baseline performance, perfusion pressure-mediated decrease and a second, afterload-modulated change.

Influences of pressure surrounding the heart and intracardiac pressure on the diastolic coronary pressure-flow relation in excised canine heart.

We investigated the change in the instantaneous diastolic left coronary pressure-flow relation (DPFR) when the pressure surrounding the heart (SHP), right heart pressure (RHP), and left heart pressure (LHP) were systematically varied. Eight excised and maximally vasodilated canine hearts placed in an air-tight chamber were used. To obtain a capacitance-free DPFR, coronary perfusion pressure was slowly decreased (about 2 mm Hg/sec) during a prolonged diastole. The zero-flow pressure (Pf = 0) and the slope of the DPFR were analyzed. The mean values of the slope did not change significantly throughout the interventions. The mean value of Pf=0 in the control state (SHP = RHP = LHP = 0 mm Hg) was 6.0 ± 2.0 mm Hg (mean ± SD, n = 8), significantly higher than the venous outflow pressure, RHP (p<0.001), and the other two pressures (p<0.001). When SHP was raised to 15 and 30 mm Hg, while the other pressures remained at 0 mm Hg, the mean values of Pf=0 increased to 20.9 ± 2.4 and 35.6 ± 3.1 mm Hg (p<0.001 and p<0.0005, respectively, vs. control). The mean values of Pf =0 when only RHP was elevated to 15 and 30 mm Hg were 16.0 ± 1.5 and 29.3 ± 1.5 mm Hg (p<0.001 and p<0.0005 vs. control). On elevation of LHP to 15 and 30 mm Hg, the mean values of Pf = 0 were 12.0 ± 2.8 and 17.3 ± 3.6 mm Hg (p<0.01 and p<0.01 vs. control). When both SHP and LHP were almost evenly elevated to about 15 and 30 mm Hg, the mean values of Pf = 0 were raised to 22.0 ± 2.9 and 35.3 ± 3.2 mm Hg, respectively. These mean values were not significantly different from those when only SHP was elevated to the comparable levels. The observation that Pf = 0 exceeded RHP in the control state and that RHP, which was elevated above the preceding Pf=0, was identical with the present Pf=0 supports the vascular waterfall mechanism when RHP is low. Furthermore, the evidence that the degree of DPFR shift was almost linearly dependent on the SHP level rather than on the LHP level indicates that the pressure on the epicardial side is one of the factors that determines the pressure at the top of the vascular waterfall.

Accumulation of risk markers predicts the incidence of sudden death in patients with chronic heart failure

Sudden death is common in chronic heart failure (CHF). Risk stratification is the first step for primary prevention.

Effects of the pericardium on the diastolic left coronary pressure-flow relationship in the isolated dog heart.

We studied the effects of the pericardium on diastolic left coronary pressure-flow relationships in heart-blocked and isolated canine preparations. In these preparations, the left and right coronary arteries were dilated with adenosine and perfused by means of a pressurized arterial reservoir. The diastolic left heart pressure (LHP) was controlled by the height of a reservoir connected to the left atrium and left ventricle. The right atrial and ventricular pressure i.e., coronary outflow pressure, was kept constant at 0 mm Hg. Before and after pericardiectomy, diastolic coronary pressure-flow relationships were obtained at three values of LHP (0, 15, and 30 mm Hg) with driving pressure decreasing (2 mm Hg/sec or less) from approximately 60 mm Hg to the actual zero-flow pressure (Pf = 0) during a single long diastole induced by cessation of ventricular pacing. The slopes of the coronary pressure-flow relationships were approximated by a linear regression analysis in which the correlation coefficients were greater than .98 in all cases. Before pericardiectomy, with LHP increasing from 0 to 15 and 30 mm Hg, the value of Pf = 0 significantly increased from 7 +/- 1 to 16 +/- 1 (p less than .01) and 28 +/- 2 mm Hg (p less than .01), respectively. After pericardiectomy, it increased from 7 +/- 1 to 14 +/- 1 (p less than .01) and 17 +/- 2 mm Hg (p less than .01), respectively. When LHP was at 0 and 15 mm Hg, the pericardiectomy had no effect on the value of Pf = 0.(ABSTRACT TRUNCATED AT 250 WORDS)

Characteristics of the increase in plasma brain natriuretic peptide level in left ventricular systolic dysfunction, associated with muscular dystrophy in comparison with idiopathic dilated cardiomyopathy

To determine whether the plasma brain natriuretic peptide level increases differentially in muscular dystrophy and idiopathic dilated cardiomyopathy, we investigated the plasma brain natriuretic peptide level and echocardiographic parameters in patients with similarly low left ventricular ejection fraction. The plasma brain natriuretic peptide level was lower, and the left ventricular end-diastolic diameter was shorter in the patients with muscular dystrophy than in those with idiopathic dilated cardiomyopathy. The correlation between the plasma brain natriuretic peptide and left ventricular ejection fraction was shifted downward in the patients with muscular dystrophy compared with those with idiopathic dilated cardiomyopathy. Those between the brain natriuretic peptide and left ventricular end-diastolic diameter were superimposable, although the data from the muscular dystrophy patients were located at the shorter left ventricular end-diastolic diameter side. The plasma brain natriuretic peptide level may differentially increase in the two diseases with similar left ventricular systolic dysfunction. Differences in the left ventricular distension and in the physical activity might explain at least partially the different plasma brain natriuretic peptide levels.

Interaction between sarcomere and mitochondrial length in normoxic and hypoxic rat ventricular papillary muscles

We hypothesized that the mitochondrial length may be altered according to changes in the sarcomere length, and that this relationship may be affected by exposure to hypoxia. Rat ventricular papillary muscles were isolated and immersed in normoxic or hypoxic solutions for 10 min. Sarcomeres of various lengths were obtained by fixing the papillary muscles in a slack or stretched state, or after exposure to a contracture solution containing saponin and CaCl(2). The mitochondrial length measured using electron microscopy significantly correlated to the length of the adjacent sarcomere in both the normoxic (n=767) and hypoxic (n=1145) groups (P<.0001). The slope of the regression line, however, was significantly less steep, and its intercept was significantly larger in the hypoxic group than in the normoxic group (analysis of covariance). When we analyzed the mitochondrial lengths among the three sarcomere-length subgroups (<1.5, 1.5-2.0, and >2.0 microm), the mitochondrial length was significantly shorter in the hypoxic condition than in the normoxic condition at sarcomere lengths greater than 2.0 microm. Staining for desmin, the major muscle-type intermediate filament, the longitudinal system of which connects the mitochondria with the Z bands of sarcomeres, showed a clear cross-striation pattern in both papillary muscles with and without the exposure to hypoxia, suggesting that desmin was preserved after the exposure to hypoxia. These data indicate that the mitochondrial length changes according to changes in the sarcomere length, suggesting the possible role of mitochondria as an internal load against myocyte contraction. It is also suggested that mitochondria exposed to hypoxia may be more resistive to both compression and stretch in a longitudinal direction than those in the normoxic condition.