Viral level is an indicator of long-term outcome of hepatitis B virus e antigen-negative carriers with persistently normal serum alanine aminotransferase levels.

The association between viral level and the long-term outcomes of hepatitis B virus (HBV) carriers who test negative for hepatitis B virus e antigen (HBeAg) but have persistently normal serum alanine aminotransferase levels (PNALT) remains unclear. We examined hepatocarcinogenesis, hepatitis reactivation, predictive factors and the time course of HBV DNA levels during follow-up in 104 HBeAg-negative Japanese carriers with PNALT. During a mean follow-up period of 6.4 ± 3.4 years, 5 patients (4.8%) had hepatocarcinogenesis and 14 (13.5%) had hepatitis reactivation. At 5 and 10 years, the cumulative rates of hepatocarcinogenesis were 2.4% and 9.9%, while those of hepatitis activation were 13.7% and 15.5%, respectively. An HBV DNA level of ≥5 log10 copies/mL was the sole predictor of hepatocarcinogenesis with a univariate analysis. An HBV DNA level of ≥5 log10 copies/mL and an alanine aminotransferase (ALT) level of >20 to ≤40 IU/L were independent predictors of hepatitis reactivation in a Cox model. Because there was no association between hepatocarcinogenesis and ALT activity, the HBV DNA level was considered an essential predictor. In addition, the baseline HBV DNA level was related to the future level and was not subject to wide fluctuations. Our results showed that an HBV DNA level of ≥5 log10 copies/mL predicts subsequent hepatocarcinogenesis and hepatitis reactivation in HBeAg-negative carriers with PNALT. As the baseline HBV DNA level reflects the future level, appropriate clinical management according to the viral level is expected to decrease future risk.

Evidence for deactivation of both ectosolic and cytosolic 5'-nucleotidase by adenosine A1 receptor activation in the rat cardiomyocytes.

Adenosine, an important regulator of many cardiac functions, is produced by ectosolic and cytosolic 5'-nucleotidase. The activity of these enzymes is influenced by several ischemia-sensitive metabolic factors, e.g., ATP, ADP, H+, and inorganic phosphate. However, there is no clear evidence that adenosine itself affects 5'-nucleotidase activity. This study tested whether adenosine decreases the activity of ectosolic and cytosolic 5'-nucleotidase. Cardiomyocytes were isolated from adult male Wistar rats and suspended in the modified Hepes-Tyrode buffer solution. After stabilization, isolated cardiomyocytes were incubated with and without adenosine (10(-9) - 10(-4) M). Ectosolic and cytosolic 5'-nucleotidase activity was decreased by exogenous adenosine (ectosolic 5'-nucleotidase activity, 20.6 +/- 2.3 vs. 8.6 +/- 1.6 mumol/min per 10(6) cells [P < 0.05]; cytosolic 5'-nucleotidase activity, 2.47 +/- 0.58 vs. 1.61 +/- 0.54 mumol/min per 10(6) cells [P < 0.05] at 10(-6) M adenosine) after 30 min. The decrease in ectosolic and cytosolic 5'-nucleotidase activity was inhibited by 8-phenyltheophylline and pertussis toxin, and was mimicked by N6-cyclohexyladenosine, an adenosine A1 receptor agonist. Neither CGS21680C, and A2 receptor agonist, nor cycloheximide deactivated ectosolic and cytosolic 5'-nucleotidase. Thus, we conclude that activation of adenosine A1 receptors is coupled to Gi proteins and attenuates ectosolic and cytosolic 5'-nucleotidase activity in rat cardiomyocytes.

Alpha 1-adrenoceptor activation mediates the infarct size-limiting effect of ischemic preconditioning through augmentation of 5'-nucleotidase activity.

We have reported that ischemic preconditioning may limit infarct size by increasing 5'-nucleotidase activity. The present study tested whether alpha 1-adrenoceptor stimulation in ischemic preconditioning mediates the infarct size-limiting effect through augmentation of 5'-nucleotidase activity. The coronary artery was occluded four times for 5 min separated by 5 min of reperfusion (ischemic preconditioning) in 82 dogs. Then the coronary artery was occluded for 90 min followed by 6 h of reperfusion. Infarct size normalized by risk area was smaller after ischemic preconditioning than in the control group (40.6 +/- 2.3 vs 6.7 +/- 2.0%, P < 0.001), even though no difference existed in endomyocardial collateral flow during ischemia (8.7 +/- 1.0 vs 8.9 +/- 1.0 ml/100 g per min). Ectosolic and cytosolic 5'-nucleotidase activity was increased after ischemic preconditioning. However, prazosin blunted the infarct size-limiting effect of ischemic preconditioning (infarct size: 42.8 +/- 3.7%). Intermittent alpha 1-adrenoceptor stimulation by methoxamine mimicked the increase in 5'-nucleotidase activity and the infarct size-limiting effect, which were abolished by alpha, beta,-methyleneadenosine 5'-diphosphate. Identical results were obtained in the conscious model (n = 20). Therefore, we conclude that increases in ectosolic 5'-nucleotidase activity due to alpha 1-adrenoceptor activation may contribute to the infarct size-limiting effect of ischemic preconditioning.

Endogenous adenosine inhibits P-selectin-dependent formation of coronary thromboemboli during hypoperfusion in dogs.

The activation of platelets and the formation of neutrophil- platelet conjugates may lead to the development of thromboemboli. We studied whether blockade of adenosine receptors during coronary hypoperfusion may cause thromboemboli via P-selectin-dependent mechanisms in 30 open-chest dogs. When coronary blood flow was reduced to 20% of the control, it was stable at low levels with increases in adenosine levels. When 8-p-sulfophenyltheophylline, an adenosine receptor antagonist, was infused during coronary hypoperfusion, coronary blood flow decreased gradually and approached almost zero 20 min after its administration. Histological examination revealed thromboemboli in the small coronary vessels. During hypoperfusion in the presence of 8-p-sulfophenyltheophylline, the mAb against P-selectin attenuated both the reduction in coronary blood flow and the formation of thromboemboli, and improved contractile and metabolic dysfunction of the myocardium. Flow cytometric analysis indicated that the expression of P-selectin on platelet and neutrophil-platelet adhesion were increased during coronary hypoperfusion, and that both were further augmented by 8-p-sulfophenyltheophylline. Immunohistochemical examination showed no staining of P-selectin in the ischemic myocardium. Adenosine inhibited the thrombin-induced expression of P-selectin on platelet and neutrophil- platelet adhesion via adenosine A2 receptors. Adenosine appears to inhibit the formation of thromboemboli during coronary hypoperfusion by suppressing the expression of P-selectin on platelets and neutrophil-platelet adhesion.

Hypoxia extends the life span of vascular smooth muscle cells through telomerase activation.

Chronic hypoxia induces smooth muscle cell proliferation and vessel wall remodeling in the vasculature of the lung. One well-characterized component of the hypoxic response is transcriptional activation of genes encoding vascular smooth muscle cell (VSMC) mitogens. We report here that chronic hypoxia can also prolong the growth of human VSMC by inducing telomerase activity and telomere stabilization. We demonstrate that hypoxia induced phosphorylation of the telomerase catalytic component (TERT) and sustained high levels of TERT protein expression in VSMC compared to normoxia. Furthermore, inhibition of telomerase shortened cell life span in hypoxic cultures, whereas constitutive expression of TERT extended the life span of cells under normoxic conditions. Our data indicate that hypoxic induction of telomerase activity could be involved in long-term growth of VSMC and may thus contribute to human vascular disorders.

Advanced Statistical Analyses to Reduce Inconsistency of Bond Strength Data.

This study was designed to clarify the interrelationship of factors that affect the value of microtensile bond strength (µTBS), focusing on nondestructive testing by which information of the specimens can be stored and quantified. µTBS test specimens were prepared from 10 noncarious human molars. Six factors of µTBS test specimens were evaluated: presence of voids at the interface, X-ray absorption coefficient of resin, X-ray absorption coefficient of dentin, length of dentin part, size of adhesion area, and individual differences of teeth. All specimens were observed nondestructively by optical coherence tomography and micro-computed tomography before µTBS testing. After µTBS testing, the effect of these factors on µTBS data was analyzed by the general linear model, linear mixed effects regression model, and nonlinear regression model with 95% confidence intervals. By the general linear model, a significant difference in individual differences of teeth was observed ( P < 0.001). A significantly positive correlation was shown between µTBS and length of dentin part ( P < 0.001); however, there was no significant nonlinearity ( P = 0.157). Moreover, a significantly negative correlation was observed between µTBS and size of adhesion area ( P = 0.001), with significant nonlinearity ( P = 0.014). No correlation was observed between µTBS and X-ray absorption coefficient of resin ( P = 0.147), and there was no significant nonlinearity ( P = 0.089). Additionally, a significantly positive correlation was observed between µTBS and X-ray absorption coefficient of dentin ( P = 0.022), with significant nonlinearity ( P = 0.036). A significant difference was also observed between the presence and absence of voids by linear mixed effects regression analysis. Our results showed correlations between various parameters of tooth specimens and µTBS data. To evaluate the performance of the adhesive more precisely, the effect of tooth variability and a method to reduce variation in bond strength values should also be considered.

Mechanisms of telomerase induction during vascular smooth muscle cell proliferation.

Telomeres are primarily controlled by a highly specialized DNA polymerase termed telomerase. Recent studies have demonstrated that introduction of the telomerase catalytic component (TERT) into telomerase-negative cells activates telomerase and extends cell life span, whereas mice lacking telomerase activity revealed impaired cell proliferation in some organs as well as reduced tumorigenesis. These reports suggest that telomerase plays an important role in long-term cell viability and cell proliferation. However, the mechanism or mechanisms by which telomerase is induced or regulated remains to be elucidated. We report here that primary vascular smooth muscle cells (VSMCs) express telomerase and that increased telomerase activity correlates with cell proliferation. Inhibition of telomerase diminished growth of VSMCs, which suggests a crucial role for telomerase activation in the regulation of VSMC proliferation. We propose a novel model whereby telomerase is first activated in the cytoplasm before cell proliferation, followed by accumulation of activity in the nucleus during the logarithmic phase of cell growth. Activation of telomerase in VSMCs was linked to phosphorylation of TERT. The protein kinase inhibitor H7 suppressed the activation of telomerase in the cytoplasm and also inhibited the accumulation of TERT as well as telomerase activity in the nucleus. These data suggest that posttranslational modification of TERT by phosphorylation is important for activation and accumulation of telomerase into the nucleus in the process of VSMC proliferation.

Inducible gene targeting in postnatal myocardium by cardiac-specific expression of a hormone-activated Cre fusion protein.

Cardiac-restricted expression of Cre recombinase can provoke lineage-specific gene excision in the myocardium. However, confounding early lethality may still preclude using loss-of-function models to study the postnatal heart. Here, we have tested whether inducible, heart-specific recombination can be triggered after birth by transgenic expression of a Cre fusion protein that incorporates a mutated progesterone receptor ligand binding domain (PR1) that is activated by the synthetic antiprogestin, RU486, but not by endogenous steroid hormones. CrePR1 driven by the alpha-myosin heavy chain (alphaMHC) promoter was expressed specifically in heart. Translocation of CrePR1 from cytoplasm to nuclei in ventricular myocytes was induced by RU486. To establish whether this approach can mediate cardiac-specific, drug-dependent excision between loxP sites in vivo, we mated alphaMHC-CrePR1 mice with a ubiquitously expressed (ROSA26) Cre reporter line. Offspring harboring alphaMHC-CrePR1 and/or the floxed allele were injected with RU486 versus vehicle, and the prevalence of beta-galactosidase (beta-gal)-positive cells was determined, indicative of Cre-mediated excision. Little or no baseline recombination was seen 1 week after birth. Cardiac-restricted, RU486-inducible recombination was demonstrated in bigenic mice at age 3 and 6 weeks, using each of 3 independent CrePR1 lines. Recombination in the absence of ligand paralleled the levels of CrePR1 protein expression and was more evident at 6 weeks. Thus, conditional, posttranslational activation of a Cre fusion protein can bypass potential embryonic and perinatal effects on the heart and permits inducible recombination in cardiac muscle. High levels of the chimeric Cre protein, in particular, were associated with progressive recombination in the absence of drug.

Identification of the Tax interaction region of serum response factor that mediates the aberrant induction of immediate early genes through CArG boxes by HTLV-I Tax.

Tax of human T-cell leukemia virus type I (HTLV-I) activates transcription at a CArG box of various immediate early genes such as the proto-oncogene c-fos. To do this, Tax does not directly bind to the CArG box, but instead binds to the CArG binding factor SRF. In this study, we investigated the domain of SRF required for the activation by Tax and studied the role of this domain on transcriptional regulation at the CArG box. Using a fusion protein of SRF with a yeast transcription factor GAL4, the 14 amino acid (aa) portion (aa 422-435) of SRF was identified as the domain required for Tax activation [Tax-responsive region of SRF (TRRS)]. By means of a two hybrid system, we showed that TRRS was essential for the interaction of SRF with Tax in vivo. The over-expression of SRF with a deletion of TRRS inhibited the Tax activation at the CArG box. Thus, TRRS is the domain of SRF that is essential for Tax activation at the CArG box. Unlike to Tax activation, TRRS was not required for TPA (12-o-tetradecanoylphobol-13-acetate) induction at the CArG box, but a TRRS deletion enhanced the basal activity at the CArG box both under serum-starved and TPA-stimulated conditions. These results suggest that TRRS negatively regulates the transcriptional activation function of SRF, and consequently contributes to the low basal activity at the CArG box before TPA induction.

Selective activation of the proto-oncogene c-jun promoter by the transforming protein v-Rel.

The transcription factor v-Rel is a transforming protein of the reticuloendotheliosis virus. We found that v-Rel activates the promoter of the proto-oncogene c-jun. Two elements in the c-jun promoter were required for the activation by v-Rel. One was a kB-site (v-Rel binding site), and the other was a c-jun promoter region between -52 and +148 (c-jun promoter (-52/+148)). Two promoters with the kB-site(s), those of human immunodeficiency virus (HIV) and SV40, were not activated by v-Rel, but their kB-sites were activated when introduced upstream of the c-jun promoter (-52/+148). Thus, the c-jun promoter (-52/+148) had information for the selective activation of the c-jun promoter by v-Rel. v-Rel bound to the c-jun kB-site with the higher affinity than c-Rel, thereby activating the c-jun promoter more efficiently than c-Rel. Moreover, the activity of v-Rel mutants upon the c-jun promoter correlates with their transforming activity. Thus, the c-jun promoter activation by v-Rel may play a role in the transformation caused by v-Rel.

Nifedipine-induced coronary vasodilation in ischemic hearts is attributable to bradykinin- and NO-dependent mechanisms in dogs.

BACKGROUND: Dihydropyridine calcium channel blockers protect endothelial cells against ischemia and reperfusion injury, suggesting that nifedipine may increase the in vivo cardiac NO level and thus coronary blood flow (CBF) in ischemic hearts. We tested this hypothesis. METHODS AND RESULTS: In open-chest dogs, coronary perfusion pressure (CPP) was reduced in the left anterior descending coronary artery so that CBF decreased to one third of the control level, and thereafter CPP was maintained constant (103+/-8 to 43+/-3 mm Hg, n=9). We obtained fractional shortening (FS) and lactate extraction ratio (LER) as indices of regional myocardial contraction and metabolism. Both FS (26.4+/-2.1% to 6.7+/-2.0%, n=9, P<0.001) and LER (32+/-6% to -37+/-5%, n=9, P<0.001) showed a decrease when CPP was reduced. After intracoronary infusion of nifedipine (4 microgram. kg(-1). min(-1)), CBF increased from 30+/-1 to 48+/-4 mL. 100 g(-1). min(-1) (P<0.01) without a change of CPP (n=9). Both FS (14.0+/-1.9%, n=9) and LER (-9+/-7%, n=9) also increased (P<0.01). Nifedipine increased the difference in the level of metabolites of NO (nitrate+nitrite; 9+/-3 to 25+/-5 nmol/mL, n=9, P<0.01) and bradykinin (22+/-5 to 58+/-4 pmol/mL, n=9, P<0.01) between coronary venous and arterial blood. L-NAME (an NO synthase inhibitor) or HOE-140 (a bradykinin receptor antagonist) attenuated (P<0.05) the increase in CBF (29+/-3 and 35+/-2 mL. 100 g(-1). min(-1), n=5 each), FS (4.8+/-0.6% and 6.9+/-1.7%, n=5 each), LER (-47+/-8% and -35+/-9%, n=5 each), and nitrate+nitrite (3+/-2 and 8+/-4 nmol/mL, n=5 each) due to nifedipine infusion. CONCLUSIONS: These results indicate that the calcium channel blocker nifedipine mediates coronary vasodilation and improves myocardial ischemia through both bradykinin/NO-dependent and -independent mechanisms.

A Ca channel blocker, benidipine, increases coronary blood flow and attenuates the severity of myocardial ischemia via NO-dependent mechanisms in dogs.

OBJECTIVES: This study was undertaken to examine whether a dihydropyridine Ca channel blocker, benidipine, increases cardiac NO levels, and thus coronary blood flow (CBF) in ischemic hearts. BACKGROUND: Benidipine protects endothelial cells against ischemia and reperfusion injury in hearts. METHODS AND RESULTS: In open chest dogs, coronary perfusion pressure (CPP) of the left anterior descending coronary artery was reduced so that CBF decreased to one-third of the control CBF, and thereafter CPP was maintained constant (103+/-8 to 42+/-1 mmHg). Both fractional shortening (FS: 6.1+/-1.0%) and lactate extraction ratio (LER: -41+/-4%) decreased. Ten minutes after the onset of an intracoronary infusion of benidipine (100 ng/kg/min), CBF increased from 32+/-1 to 48+/-4 ml/100g/ min during 20 min without changing CPP (42+/-2 mmHg). Both FS (10.7+/-1.2%) and LER (-16+/-4%) also increased. Benidipine increased cardiac NO levels (11+/-2 to 17+/-3 nmol/ml). The increases in CBF, FS, LER and cardiac NO levels due to benidipine were blunted by L-NAME. Benidipine increased cyclic GMP contents of the coronary artery of ischemic myocardium (139+/-13 to 208+/-15 fmol/mg protein), which was blunted by L-NAME. CONCLUSION: Thus, we conclude that benidipine mediates coronary vasodilation and improves myocardial ischemia through NO-cyclic GMP-dependent mechanisms.

Characteristics of frequency content of atrial signal-averaged electrocardiograms during sinus rhythm in patients with paroxysmal atrial fibrillation.

To clarify the characteristics of the frequency content of atrial signal-averaged electrocardiograms (ECGs) during sinus rhythm in patients with paroxysmal atrial fibrillation, P wave-triggered signal-averaged ECGs were recorded in 28 patients with and 34 control patients without paroxysmal atrial fibrillation. Fast Fourier transform analysis was performed on the 100-ms segment starting 75 ms before the end of the P wave. An area ratio (AR50) was calculated by dividing the area under the spectrum curve between 20 and 50 Hz, multiplied by 100, by the area between 0 and 20 Hz. Magnitude ratios (MR20, MR30, MR40 and MR50) were calculated by dividing the magnitude at 20, 30, 40 and 50 Hz, respectively, multiplied by 100, by the maximal magnitude of the entire signal. AR50 was significantly greater in patients with than without paroxysmal atrial fibrillation (62.3 +/- 34.2 vs. 42.4 +/- 18.4). MR20 and MR30 were also significantly greater in patients with than without paroxysmal atrial fibrillation (MR20 76.1 +/- 15.2 vs. 60 +/- 20.2; MR30 41 +/- 18.8 vs. 26.6 +/- 14.4), although no significant differences in MR40 or MR50 were observed between the two patient groups. The difference in MR30 between groups remained significant even after taking into account the presence of organic heart disease. It is concluded that, irrespective of the presence of organic heart disease, the terminal portion of the P wave contained significantly more components in the 20- to 50-Hz range, especially around 30 Hz, in patients with than in patients without paroxysmal atrial fibrillation. These results suggest that frequency analysis could characterize atrial signal-averaged ECGs of patients at risk for paroxysmal atrial fibrillation.

Which subgroup of patients with dilated cardiomyopathy would benefit from long-term beta-blocker therapy? A histologic viewpoint.

OBJECTIVES: The purpose of this study was to elucidate whether the effectiveness of long-term beta-blocker therapy could be predicted before this therapy is started. BACKGROUND: Long-term beta-blocker therapy has recently been reported to provide a favorable effect in treatment of congestive heart failure due to dilated cardiomyopathy. METHODS: Several measurements including histologic variables before administration of metoprolol were retrospectively compared among 18 good responders (showing improvement of at least one New York Heart Association functional class or an increase in ejection fraction > or = 0.10 12 months after drug administration) and 12 poor responders without such improvement. RESULTS: Although there were no significant differences between the two groups in age, gender, functional class, heart rate, blood pressure, pulmonary capillary wedge pressure, cardiac index, left ventricular end-diastolic dimension and ejection fraction, percent fibrosis estimated by the point-counting method in endomyocardial biopsy specimens was significantly lower in good than in poor responders (7.6 +/- 5.7 vs. 14.2 +/- 9.7%, p < 0.05). Moreover, when the types of fibrosis were classified as interfascicular and intercellular by the dominance of counted points, there were 13 cases of interfascicular fibrosis and 5 cases of intercellular fibrosis in good responders and 1 case of interfascicular fibrosis and 11 cases of intercellular fibrosis in poor responders (p < 0.001, sensitivity 72%, specificity 91%, predictive accuracy 80%). These results suggest that improvement with long-term beta-blocker therapy may be more likely to occur in patients with less myocardial fibrosis, with interfascicular fibrosis the dominant type. CONCLUSIONS: The extent and type of fibrosis may be important factors in the prediction of the effectiveness of long-term beta-blocker therapy for dilated cardiomyopathy.

Dobutamine stress echocardiography predicts reversible dysfunction and quantitates the extent of irreversibly damaged myocardium after reperfusion of anterior myocardial infarction.

OBJECTIVES: This study was designed to evaluate dobutamine stress echocardiography in identifying reversible dysfunction and assessing the extent of irreversibly damaged myocardium early in acute myocardial infarction. BACKGROUND: Several experimental and clinical studies have suggested that dobutamine enhances contractile function of stunned or hibernating, or both, myocardium. It is important for clinical strategy to predict the magnitude of improvement in myocardial function early in acute myocardial infarction. METHODS: We studied 21 patients with a reperfused first anterior myocardial infarction. Two-dimensional echocardiography was performed before and during dobutamine infusion (10 micrograms/kg body weight per min) at a mean of 3 days after the infarction. Follow-up echocardiography was performed at a mean of 25 days later. To assess segmental wall motion, we divided the left ventricle into 17 segments and assigned a wall motion abnormality score: 3 = dyskinesia or akinesia; 0 = normal. Improvement in wall motion was indicated by a decrease of at least one grade in segmental score. For quantitative assessment, the ratio of endocardial length showing dyskinesia or akinesia to a left ventricular endocardial length (akinetic length ratio) was determined in the apical long-axis view at each stage. RESULTS: Sensitivity and specificity of dobutamine infusion in detecting improvement in wall motion at follow-up echocardiography were 83% (55 of 66 segments) and 86% (43 of 50 segments), respectively. Excellent correlation was found (r = 0.93, p < 0.001; absolute difference [mean +/- SD] 0.03 +/- 0.05) between the akinetic length ratios measured during dobutamine infusion and in the late convalescent stage. CONCLUSIONS: In the early stage of acute myocardial infarction, low dose dobutamine stress echocardiography provides a useful method for predicting reversible dysfunction with excellent sensitivity and specificity and can also be used to quantitate the extent of irreversibly damaged myocardium.

Beneficial effect of intracoronary verapamil on microvascular and myocardial salvage in patients with acute myocardial infarction.

OBJECTIVES: We assessed the acute effect of intracoronary injection of verapamil on microvascular function after primary percutaneous translumanal coronary angioplasty (PTCA) for acute myocardial infarction (AMI) with myocardial contrast echocardiography (MCE) in relation to functional outcomes. BACKGROUND: Recent clinical studies have documented the potential of verapamil for possible increase in coronary blood flow after primary PTCA. METHODS: Forty patients with a first AMI were randomly assigned to the verapamil group (n = 20) or the control group (n = 20). In the verapamil group, verapamil (0.5 mg) was injected into the infarct-related artery shortly after PTCA, followed by the oral administration. We performed MCE with an intracoronary injection of sonicated microbubbles before and after verapamil. To assess microvascular integrity, we determined the baseline-subtracted peak intensity in the risk area and the ratio of the no reflow zone plus the low reflow zone to the risk area (low reflow ratio). We determined the average wall motion score (dyskinesia/akinesia = 3; normal = 0) in the risk area on the day of AMI and a mean of 24 days later. RESULTS: The low reflow zone was observed shortly after PTCA in 14 verapamil group patients, and the low reflow ratio decreased after verapamil (0.39 +/- 0.23 vs. 0.29 +/- 0.17 [mean +/- SD], p < 0.05). Peak intensity significantly (p < 0.05) increased from 6 +/- 5 to 12 +/- 6 after verapamil. The reduction in wall motion score from the acute (day -1) to the late stage (day -24) was significantly greater in the verapamil group than in the control group (0.7 +/- 0.8 vs. 0.2 +/- 1.3, respectively, p < 0.05). CONCLUSIONS: Intracoronary administration of verapamil after primary PTCA can attenuate microvascular dysfunction and thereby augment myocardial blood flow in patients with AMI, leading to better functional outcome than with PTCA alone.

Role of nitric oxide in regulation of coronary blood flow during myocardial ischemia in dogs.

OBJECTIVES: This study was undertaken to examine whether nitric oxide released in ischemic myocardium decreases the coronary vascular resistance and attenuates the severity of contractile and metabolic dysfunction. BACKGROUND: Endothelium-derived relaxing factor, recently identified as nitric oxide, is a potent relaxant of coronary smooth muscle. METHODS: The left anterior descending coronary artery was perfused through an extracorporeal bypass tube placed in the carotid artery in 56 open chest dogs. After hemodynamic stabilization, we occluded this bypass tube to decrease coronary blood flow to one third of the control flow. Thereafter, we maintained a constant coronary perfusion pressure (40.9 +/- 3.1 mm Hg). RESULTS: Under ischemic conditions, the coronary arteriovenous differences in nitrate and nitrite (end products of nitric oxide) increased (from 3.5 +/- 0.4 [mean +/- SEM] to 12.9 +/- 2.1 mumol/liter, p < 0.01). NG-Monomethyl L-arginine (3 micrograms/kg body weight per min, intracoronary) decreased the coronary arteriovenous differences in nitrate and nitrite (5.0 +/- 0.9 mumol/liter, p < 0.05) and coronary blood flow (from 29.8 +/- 0.5 to 18.1 +/- 1.1 ml/100 g per min, p < 0.001). Fractional shortening (from 3.7 +/- 1.0 to -1.3 +/- 0.7%, p < 0.001) and lactate extraction ratio (from -44.0 +/- 4.1 to -59.2 +/- 4.9%, p < 0.005) of the perfused area also decreased. These values were restored by the concomitant administration of L-arginine. Blood flow to the endomyocardium was decreased relative to the epimyocardium. A reduction in coronary blood flow and worsening of myocardial contractile and metabolic functions due to the administration of NG-monomethyl L-arginine during ischemia were observed in denervated hearts. A reduction in coronary blood flow in ischemic myocardium was observed with the administration of NW-nitro-L-arginine methyl ester as well, although neither NW-nitro-L-arginine methyl ester nor NG-monomethyl L-arginine changed coronary blood flow and myocardial contractile and metabolic functions in the nonischemic myocardium. The cyclic guanosine monophosphate content of epicardial coronary artery increased due to myocardial ischemia; this increase was attenuated with NG-monomethyl L-arginine treatment. CONCLUSIONS: We conclude that endogenous nitric oxide predominantly decreases the coronary vascular resistance of ischemic endomyocardium, thereby improving myocardial contractility and metabolic function.

Effect of angina pectoris on myocardial protection in patients with reperfused anterior wall myocardial infarction: retrospective clinical evidence of "preconditioning".

OBJECTIVES: We examined whether angina pectoris occurring shortly before the onset of acute myocardial infarction can actually preserve postischemic left ventricular function in humans. BACKGROUND: Experimental studies indicate that brief, transient episodes of ischemia render the heart very resistant to infarction from a subsequent sustained ischemic insult, an effect termed ischemic preconditioning. However, no clinical data are available concerning the implications of angina pectoris shortly before the onset of infarction in humans. METHODS: We studied 84 patients with an acute anterior myocardial infarction. All patients had total occlusion of the proximal or medial portion of the left anterior descending coronary artery and achieved reflow within 6 h of onset. Patients were classified into three groups on the basis of duration of antecedent angina pectoris: group 1 = no angina (37 patients); group 2 = new angina pectoris occurring < or = 7 days of onset of infarction (22 patients); group 3 = angina pectoris beginning > 7 days before onset of infarction (25 patients). All patients underwent left ventriculography on the day of, and 28 days after, onset of infarction to determine ejection fraction and regional wall motion in the territory of the left anterior descending coronary artery by the centerline method. RESULTS: Angiographic collateral flow grade was higher in group 3 than in groups 1 and 2 ([mean +/- SD] group 1 = 0.08 +/- 0.7, group 2 = 0.7 +/- 0.7, group 3 = 1.5 +/- 0.8). Although there were no differences in baseline ejection fraction and regional wall motion among the three groups, the degree of improvement was significantly greater in groups 2 and 3 than in group 1 (late minus baseline ejection fraction: group 1 = 0 +/- 8%, group 2 = 7 +/- 10% group 3 = 6 +/- 10% [p < 0.05 group 1 vs. groups 2 and 3]; late minus baseline regional wall motion: group 1 = 0.2 +/- 0.4, group 2 = 0.6 +/- 0.5, group 3 = 0.5 +/- 0.6 SD/chord [p < 0.05, group 1 vs. group 2]). When the study was limited to those patients with no or poor collateral flow (31 in group 1, 19 in group 2, 10 in group 3), only group 2 patients had a significant improvement in wall motion. Angina pectoris within 24 h before onset of infarction was more frequent in group 2 (82%) than group 3 (28%, p < 0.05). CONCLUSIONS: Episodes of angina pectoris occurring shortly before the onset of infarction may preserve myocardial contractile function in reperfused myocardial infarction despite less support from collateral flow channels, although these are suggestive results in a limited number of patients.

Intravenous nicorandil can preserve microvascular integrity and myocardial viability in patients with reperfused anterior wall myocardial infarction.

OBJECTIVES: We assessed whether the intravenous administration of nicorandil, an adenosine triphosphate (ATP)-sensitive K+ channel opener, exerts beneficial effect on microvascular function and functional and clinical outcomes in patients with acute myocardial infarction (AMI). BACKGROUND: Experimental studies documented that ATP-sensitive K+ channel opener exerts cardioprotection after prolonged ischemia. METHODS: We randomly divided 81 patients with a first anterior AMI into two groups, nicorandil (n = 40) and control groups (n = 41). All patients received successful coronary angioplasty within 12 h after the symptom onset and underwent myocardial contrast echcardiography (MCE) with the intracoronary injection of sonicated microbubbles. In the nicorandil group, we injected 4 mg of nicorandil followed by the infusion at 6 mg/h for 24 h and by oral nicorandil (15 mg/day). RESULTS: The improvement in regional left ventricular function, wall motion score and regional wall motion was significantly better in the nicorandil group then in the control group. Intractable congestive heart failure, malignant ventricular arrhythmia and pericardial effusion were more frequently found in the control group than in the nicorandil group (15% vs. 37%, 5% vs. 20% and 8% vs. 37%, p < 0.05, respectively). The frequency of sizable MCE no reflow phenomenon was significantly lower in the nicorandil group than in the control group (15% vs. 33%, p < 0.05). CONCLUSIONS: Intravenous nicorandil in conjunction with coronary angioplasty is associated with better functional and clinical outcomes compared to angioplasty alone in patients with an anterior AMI. Myocardial contrast echocardiography findings imply that an improvement in microvascular function with nicorandil may be attributable to this better outcome.