NO modulates monocyte chemotactic protein-1 expression in endothelial cells under cyclic strain

Endothelial cells (ECs) under hemodynamic forces increase intracellular reactive oxygen species (ROS) that modulate gene expression. We previously showed that NO attenuated the shear flow-induced gene level. The present study explored the role of endothelial NO in cyclic strain-treated ECs. Treatment of ECs with S-nitroso-N-acetylpenicillamine (SNAP), an NO donor, reduced cyclic strain-induced monocyte chemotactic protein (MCP)-1 expression. Conversely, exposure of ECs to an NO synthase inhibitor augmented MCP-1 mRNA levels. NO attenuated the binding of activator protein-1 to the 12-O-tetradecanoylphobol-13-acetate-responsive element (TRE) in the MCP-1 promoter region. ECs overexpressed with endothelial NO synthase (eNOS) inhibited cyclic strain-induced MCP-1 expression and MCP-1 promoter (-540 bp) activity. Consistently, ECs treated with SNAP or infected with adenovirus carrying eNOS reduced strain-induced superoxide levels. These strain-induced superoxide and MCP-1 expressions were greatly blunted by treating ECs with an NADPH oxidase inhibitor, diphenyleneiodonium chloride or apocynine, but not with a xanthine oxidase inhibitor. ECs infected with adenovirus carrying the dominant-negative mutant of Rac (RacN17), a component of NADPH oxidase, reduced the strain-induced superoxide and MCP-1 expression. In contrast, ECs transfected with a constitutively active Rac (RacV12) increased MCP-1 and 4x TRE promoter activities. However, ECs cotransfected with eNOS and RacV12 reduced those promoter activities. Consistently, the increases of superoxide levels and MCP-1 expression by overexpression of RacV12 were abolished after infecting ECs with eNOS. Our results show that NO from eNOS-inhibiting redox-sensitive MCP-1 expression is mediated via Rac-dependent NADPH oxidase by reducing ROS. This study provides a molecular basis to support the notion that endothelial NO acts as an antioxidant by negatively regulating redox-sensitive gene expression in ECs constantly under hemodynamic influence.

Endothelial exposure to hypoxia induces Egr-1 expression involving PKCalpha-mediated Ras/Raf-1/ERK1/2 pathway

Hypoxia induces endothelial dysfunction that results in a series of cardiovascular injuries. Early growth response-1 (Egr-1) has been indicated as a common theme in vascular injury. Here we demonstrates that in bovine aortic endothelial cells (ECs) subjected to hypoxia (PO(2) approximately 23 mmHg), rapidly increased Egr-1 mRNA expression which peaked within 30 min and decreased afterwards. Treatment of ECs with PD98059, a specific inhibitor to mitogen-activated protein kinase (MAPK/ERK), inhibited this hypoxia-induced Egr-1 expression. The involvement of ERK pathway was further substantiated by the inhibition of Egr-1 promoter activities when ECs were co-transfected with a dominant negative mutant of Ras (RasN17), Raf-1 (Raf 301), or a catalytically inactive mutant of ERK2 (mERK). In addition, the hypoxia-induced transcriptional activity of Elk-1, an ERK substrate, was abolished by administration of PD98059. Addition of calphostin C, a protein kinase C (PKC) inhibitor, completely blocked the hypoxia-augmented Egr-1 expression. The likewise occurred while exposing ECs to D609 to inhibit phospholipase C and BAPTA/AM to chelate intracellular calcium. Hypoxia to ECs increased ERK phosphorylation within 10 min and which was abolished by administration of PD98095, calphostin C, and BAPTA/AM. Hypoxia triggered a transient translocation of PKCalpha from cytosol to membrane fraction concurrent with the association of PKCalpha to Raf-1. Involvement of PKCalpha in mediating ERK activation was further confirmed by the inhibition of ERK and the subsequent Egr-1 gene induction with antisense oligonucleotides to PKCalpha. These results indicate that ECs under hypoxia induce Egr-1 expression and this induction requires calcium, phospholipase C activation, and PKCalpha-mediated Ras/Raf-1/ERK1/2 signaling pathway. Our finding support the importance of specific PKC isozyme linked to MAPK pathway in the regulation of endothelial responses to hypoxia.

Chinese herbal remedy wogonin inhibits monocyte chemotactic protein-1 gene expression in human endothelial cells

Wogonin (Wog), an active component of Scutellaria baicalensis, has antioxidant and anti-inflammatory properties. Monocyte chemotactic protein-1 (MCP-1), a potent chemoattractant for monocytes, plays a crucial role in case of early inflammatory responses, including atherosclerosis. In this study, we investigated the effect of Wog on phorbol ester (PMA)-induced MCP-1 expression in human umbilical vein endothelial cells (ECs). The MCP-1 mRNA levels and MCP-1 release in Wog-treated ECs were measured. Wog inhibited PMA-induced MCP-1 mRNA levels and MCP-1 secretion in a dose-dependent manner. The inhibition of MCP-1 induction by Wog is a transcriptional event, as shown by Wog's significant reduction of both MCP-1 promoter and 4x 12-O-tetradecanoylphorbol-13-acetate response element-luciferase reporter activities. By electrophoretic mobility assay, Wog significantly reduced the AP-1 binding activity induced by PMA. Furthermore, the PMA-induced extracellular signal-regulated kinase 1/2 and c-Jun amino-terminal kinase activities that contributed to AP-1 activity and MCP-1 gene induction were obviously attenuated after pretreating ECs with Wog. The decrease of MCP-1 secretion by Wog pretreatment led to a reduction of monocyte adhesion to ECs. Taken together, our results demonstrate that Wog inhibits MCP-1 induction in ECs; this inhibition is mediated by reducing AP-1 transcriptional activity via the attenuation of ERK1/2 and JNK signal transduction pathways. We conclude that Wog has the potential therapeutic development for use in anti-inflammatory and vascular disorders.

Immediate and long-term outcomes of stent implantation for unprotected left main coronary artery disease

Left main coronary artery (LMCA) disease is now uniformly treated with coronary artery bypass grafting (CABG). However, some patients with LMCA disease do not receive CABG because of high operative risks. The advent of stent implantation has permitted a non-operative improvement in myocardial blood flow in many patients with single- and multi-vessel coronary artery disease. However, the outcomes of stent implantation for unprotected LMCA disease are still unclear. Stent implantation was performed for unprotected LMCA disease in 13 patients; eight patients had high operative risk and five patients had refused CABG. The primary success rate was 100% (13/13 patients). One patient (8%) developed a non-Q-wave myocardial infarction after LMCA stenting. Repeat angiography was obtained in five patients (38%) with recurrent angina, and three patients (23%) received repeated percutaneous transluminal coronary angioplasty (PTCA) for LMCA restenosis. In the follow-up period of 18+/-3 months, 12 patients (92%) remained in satisfactory condition with no further need for surgical intervention. One patient (8%) ultimately required CABG, and she died after CABG at 3 months after LMCA stenting. In conclusion, although CABG remains the standard treatment for LMCA disease, the present study demonstrates that stent implantation is a safe and clinically beneficial revascularization procedure for unprotected LMCA disease in patients who have high operative risk as well as those who refuse CABG.

Sequential activation of protein kinase C (PKC)-alpha and PKC-epsilon contributes to sustained Raf/ERK1/2 activation in endothelial cells under mechanical strain

Endothelial cells (ECs) are constantly subjected to hemodynamic forces including cyclic pressure-induced strain. The role of protein kinase C (PKC) in cyclic strain-treated ECs was studied. PKC activities were induced as cyclic strain was initiated. Cyclic strain to ECs caused activation of PKC-alpha and -epsilon. The translocation of PKC-alpha and -epsilon but not PKC-beta from the cytosolic to membrane fraction was observed. An early transient activation of PKC-alpha versus a late but sustained activation of PKC-epsilon was shown after the onset of cyclic strain. Consistently, a sequential association of PKC-alpha and -epsilon with the signaling molecule Raf-1 was shown. ECs treated with a PKC inhibitor (calphostin C) abolished the cyclic strain-induced Raf-1 activation. ECs under cyclic strain induced a sustained activation of extracellular signal-regulated protein kinases (ERK1/2), which was inhibited by treating ECs with calphostin C. ECs treated with a specific Ca(2+)-dependent PKC inhibitor (Go 6976) showed an inhibition in the early phase of ERK1/2 activation but not in the late and sustained phase. ECs transfected with the antisense to PKC-alpha, the antisense to PKC-epsilon, or the inhibition peptide to PKC-epsilon reduced strain-induced ERK1/2 phosphorylation in a temporal manner. PKC-alpha mediated mainly the early ERK1/2 activation, whereas PKC-epsilon was involved in the sustained ERK1/2 activation. Strained ECs increased transcriptional activity of Elk1 (an ERK1/2 substrate). ECs transfected with the antisense to each PKC isoform reduced Elk1 and monocyte chemotactic protein-1 promotor activity. Our findings conclude that a sequential activation of PKC isoform (alpha and epsilon) contribute to Raf/ERK1/2 activation, and PKC-epsilon appears to play a key role in endothelial adaptation to hemodynamic environment.

Intravenous amiodarone for prevention of atrial fibrillation after coronary artery bypass grafting

BACKGROUND

Atrial fibrillation occurs in 10% to 40% of patients who undergo coronary artery bypass grafting. This prospective study assesses the safety and efficacy of low-dose intravenous amiodarone in the prevention of atrial fibrillation after coronary artery bypass grafting.

METHODS

One hundred forty patients were randomly divided into two groups: an amiodarone group (n = 74) receiving intravenous amiadarone in a loading dose of 150 mg and maintenance dose of 0.4 mg x kg(-1) x h(-1) for 3 days before and 5 days after operation and a control group (n = 76) receiving matching infusions of 5% glucose solution.

RESULTS

Atrial fibrillation occurred in 9 (12%) of the amiodarone group patients and in 26 (34%) of the control group patients during hospitalization (p < 0.01). The maximum ventricular rate during atrial fibrillation was significantly slower in the amiodarone group (107 +/- 21) than in the control group (138 +/- 24 beats per minute, p < 0.01). The duration of atrial fibrillation in the amiodarone group (1.1 +/- 1.2 hours) was significantly shorter than that in the control group (3.2 +/- 1.3 hours, p = 0.01). The two groups had no significant differences in incidence of major morbidity (8 of 74 versus 8 of 76 in amiodarone and control groups, respectively) or mortality (4 of 74 versus 5 of 76). However, the control group had significantly longer intensive care unit stays (132 +/- 24 versus 111 +/- 19 hours, p < 0.01).

CONCLUSIONS

Perioperative low-dose intravenous amiodarone significantly reduces the incidence, ventricular rate, and duration of atrial fibrillation after coronary artery bypass grafting. Furthermore, low-dose intravenous amiodarone is well tolerated and does not increase the risk of intraoperative or postoperative complications.

A randomized, prospective comparison of anterior and posterior approaches to atrioventricular junction modification of medically refractory atrial fibrillation

To compare the safety and efficacy of anterior versus posterior approach for atrioventricular (AV) junction modification, 40 patients with medically refractory paroxysmal (PAF) or chronic atrial fibrillation (AF) were randomly assigned to receive AV junction modification with an anterior or posterior approach. If the ablation session had taken more than 1 hour without success, the alternative ablation approach was attempted. Among the 18 patients assigned to receive the anterior approach, 14 (78%) had a primary success. One (5%) patient had complete AV block after ablation. Three patients crossed over to the posterior approach and had a successful outcome. Fourteen (64%) of 22 patients initially treated with the posterior approach had primary success. One (4%) patient developed complete AV block. Seven patients crossed over to the anterior approach and had a successful outcome. The primary success rate (14/18 vs 14/22, P = NS), incidence of transient AV block (3/18 vs 3/22, P = NS), and complete AV block (1/18 vs 1/22, P = NS) were similar between the anterior approach and posterior approach. The major differences between the two groups showed more radiofrequency pulses (10 +/- 4 vs 6 +/- 3 pulses, P < 0.01), longer procedure duration (50 +/- 24 vs 28 +/- 18 minutes, P < 0.01), and longer fluoroscopy exposure time (28 +/- 17 vs 16 +/- 8 minutes, P < 0.01) in the patients who had primary success with the posterior approach. In conclusion, this study demonstrated that (1) the two techniques had similar efficacies; (2) if one approach was ineffective, switching to the other approach might be safe; (3) combining these two approaches resulted in overall improvement in the success rate of this procedure, and (4) the posterior approach needed more radiofrequency pulses, longer procedural time, and longer fluoroscopy exposure time.

Effect of verapamil on long-term tachycardia-induced atrial electrical remodeling

BACKGROUND

The effect of verapamil on long-term tachycardia-induced atrial electrical remodeling has not been reported.

METHODS AND RESULTS

Forty-eight dogs were randomly divided into verapamil and control groups. The dogs in the verapamil group received verapamil 120 mg every day, those in the control group did not receive verapamil. Atrial effective refractory period (AERP), inducibility of atrial fibrillation (AF), and duration of AF were assessed before and after complete atrioventricular junction ablation with 1-day, 1-week, or 6-week rapid atrial pacing (780 bpm). AERP shortening, AERP dispersion, AERP maladaptation, and inducibility of AF after 1-day pacing was significantly attenuated by verapamil. However, verapamil did not have any significant effect on these parameters in the dogs with 1-week or 6-week pacing. Verapamil did not have any significant effect on the conduction velocity in the dogs with 1-day, 1-week, or 6-week pacing. Before rapid atrial pacing, verapamil significantly prolonged the duration of AF. In the dogs with 1-day pacing, the duration of AF measured immediately after termination of pacing was similar between the control and verapamil groups. However, in the dogs with 1-week or 6-week pacing, the duration of AF after pacing was significantly longer in the verapamil group.

CONCLUSIONS

Verapamil cannot prevent long-term (1 and 6 weeks, respectively) tachycardia-induced changes of atrial electrophysiological properties. Furthermore, verapamil increases the duration of AF in the dogs either before or after long-term rapid atrial pacing.

Cyclic strain induces redox changes in endothelial cells

Our previous studies have shown that cyclic strain to endothelial cells (ECs) increases reactive oxygen species (ROS) that act as second messengers. The potential impact of these enhanced ROS levels on ECs was examined by studying the antioxidant activities and heme oxygenase-1 (HO-1) expression in strained ECs. Cyclic strain to ECs increased lipid peroxidation and augmented oxidation of low-density lipoproteins. ECs subjected to strain increased their superoxide dismutase activities. Concomitantly, glutathione peroxidase activities increased in 3 to 6 hr and returned to basal level 24 hr after continuous cyclic strain treatment. A decrease of glutathione (GSH) was accompanied with an increase of oxidized glutathione (GSSH) level in ECs 3 to 6 hr after strain treatment. This was followed with a return of both GSH and GSSH to basal levels in 24 hr. Consistently, H2O2 treatment of ECs decreased the GSH/GSSG ratio. ECs pretreated with catalase abolished the strain-induced change in GSH/GSSG. Strain treatment, similar to H2O2 exposure, induced HO-1 expression in a time-dependent manner. This induction was inhibited after treating ECs with catalase or free radical scavenger. ECs treated with N-acetyl-cysteine abolished HO-1 gene induction. Our results suggest that cyclic strain-induced ROS cause a transient increase of glutathione peroxidase activity that results in a decrease of GSH level in ECs and that this decrease is crucial to HO-1 induction.

Change of atrial refractory period after short duration of rapid atrial pacing: regional differences and possible mechanisms

It is unknown whether there are regional differences in the change of atrial effective refractory period (ERP) after a short duration of rapid atrial pacing. Furthermore, the effects of calcium channel and potassium channel on this phenomenon have not been extensively investigated. In opened-chest dogs, the endocardial monophasic action potential duration at 90% repolarization (APD90) from the right atrial appendage, and ERP from seven atrial sites were measured before and after rapid atrial pacing at 800 beats/min for 30 minutes. Both atrial ERP and APD90 significantly shortened after rapid atrial pacing. The postpacing atrial ERP and APD90 shortening persisted for 119 +/- 3 and 123 +/- 4 seconds after cessation of pacing, respectively. There was no significant difference in the magnitude or recovery course of atrial ERP shortening after pacing among the seven atrial sites. Pretreatment with nicorandil and d-sotalol had no effects on the magnitude or recovery course of atrial ERP shortening after pacing. However, the degree of ERP and APD90 shortening after pacing was significantly attenuated in the verapamil and ryanodine groups; furthermore, the recovery of ERP and APD90 after cessation of pacing was faster in the two groups. In conclusion, shortening of atrial ERP induced by short-duration rapid atrial pacing was uniform in both atria. Both the adenosine triphosphatase (ATP) dependent potassium current and rapid component of the delayed rectifier did not significantly influence this phenomenon, but both the verapamil and ryanodine could significantly attenuate the degree of atrial ERP and APD90 shortening.

Modulation of Ras/Raf/extracellular signal-regulated kinase pathway by reactive oxygen species is involved in cyclic strain-induced early growth response-1 gene expression in endothelial cells

Endothelial cells (ECs) exposed to cyclic strain induce gene expression. To elucidate the signaling mechanisms involved, we studied the effects of cyclic strain on ECs by using early growth response-1 (Egr-1) as a target gene. Cyclic strain induced a transient increase of Egr-1 mRNA levels that resulted in an increase of binding of nuclear proteins to the Egr-1 binding sequences in the platelet-derived growth factor-A promoter region. ECs subjected to strain enhanced Egr-1 transcription as revealed by promoter activities. Catalase pretreatment inhibited this induction. ECs, transfected with a dominant positive mutant of Ras (RasL61), increased Egr-1 promoter activities. In contrast, transfection with a dominant negative mutant of Ras (RasN17) attenuated this strain inducibility. ECs transfected with a dominant negative mutant of Raf-1 (Raf301) or the catalytically inactive mutant of extracellular signal-regulated kinase (ERK)-2 (mERK2) diminished strain-induced promoter activities. However, little effect on strain inducibility was observed in ECs transfected with a dominant negative mutant of Rac (RacN17) or a catalytically inactive mutant of JNK (JNK[K-R]). Consistently, strain-induced Egr-1 expression was inhibited after ECs were treated with a specific inhibitor (PD98059) to mitogen-activated protein kinase kinase. Moreover, strain to ECs induced mitogen-activated protein kinase/ERK activity. The activation of the ERK pathway was further substantiated by an increase of strain-induced transcriptional activity of Elk1, an ERK substrate. This strain-induced ERK activity was attenuated after ECs were treated with N-acetylcysteine or catalase. Consequently, this Egr-1 gene induction was abolished after ECs were treated with N-acetylcysteine or catalase. Deletion analyses of the promoter region (-698 bp) indicated that cyclic strain and H2O2 shared a common serum response element. Our data clearly indicate that cyclic strain-induced Egr-1 expression is mediated mainly via the Ras/Raf-1/ERK pathway and that strain-induced reactive oxygen species can modulate Egr-1 expression at least partially via this signaling pathway.

The role of P wave in prediction of atrial fibrillation after coronary artery surgery

Atrial fibrillation (AF) is a common arrhythmia after coronary artery bypass surgery (CABG). The purpose of this study was to determine the role of P wave duration, amplitude and dispersion in the prediction of AF after CABG. This study included 120 patients undergoing elective CABG. Clinical characteristics, 12-lead electrocardiogram (ECG), echocardiogram and coronary angiogram were obtained in all patients. We measured P wave duration, amplitude and dispersion from 12-lead ECG in each patient. After CABG, all patients were continuously monitored for AF attacks in the intensive care unit and ordinary ward. Our results showed that age greater than 60 years was the strongest predictor of postoperative AF (p<0.01), with a 3.7-fold greater likelihood of developing postoperative AF compared to ages less than 60 years. Gender was another independent predictor of postoperative AF, with men being 3.0 times more likely to develop postoperative AF compared to women (p = 0.03). The presence of prolonged P wave duration (> or =100 ms in lead II) was also an independent predictor (p = 0.04), with 2.9-fold greater risk of developing postoperative AF compared to a P wave duration of less than 100 ms. The P wave dispersion was similar between patients with and without postoperative AF (29+/-15 vs. 33+/-15 mm, p = NS). In conclusion, old age, male gender and prolonged P wave duration were independent predictors of AF after CABG. However, P wave dispersion and amplitude did not provide significant information in the prediction of postoperative AF.

Regional differences in the recovery course of tachycardia-induced changes of atrial electrophysiological properties

BACKGROUND

Regional differences in recovery of tachycardia-induced changes of atrial electrophysiological properties have not been well studied.

METHODS AND RESULTS

In the control group (5 dogs), atrial effective refractory period (AERP) and inducibility of atrial fibrillation (AF) were assessed before and every 4 hours for 48 hours after complete atrioventricular junction (AVJ) ablation with 8-week VVI pacing. In experimental group 1 (15 dogs), AERP and inducibility of AF were assessed before and after complete AVJ ablation with 8-week rapid right atrial (RA) pacing (780 bpm) and VVI pacing. In experimental group 2 (7 dogs), AERP and inducibility of AF were assessed before and after 8-week rapid left atrial (LA) pacing and VVI pacing. AERP and inducibility and duration of AF were obtained from 7 epicardial sites. In the control group, atrial electrophysiological properties obtained immediately and during 48-hour measurements after pacing did not show any change. In the 2 experimental groups, recovery of atrial electrophysiological properties included a progressive recovery of AERP shortening, recovery of AERP maladaptation, and decrease of duration and episodes of reinduced AF. However, recovery of shortening and maladaptation of AERP and inducibility of AF was slower at the LA than at the RA and Bachmann's bundle.

CONCLUSIONS

The LA had a slower recovery of tachycardia-induced changes of atrial electrophysiological properties, and this might play a critical role in initiation of AF.

Circadian variation of paroxysmal supraventricular tachycardia

BACKGROUND

Various clinical manifestations of cardiovascular diseases have a pattern of circadian variation. In this study, we investigated whether the onset and duration of paroxysmal supraventricular tachycardia (PSVT) has a circadian variation.

METHODS AND RESULTS

In our analysis, we included 105 patients with 498 PSVT episodes. In this study, the onset of PSVT did not have a uniform distribution throughout the 24-h period. There were nearly equal peaks in the time periods from 8:00 to 9:00 AM, 12:00 to 1:00 PM, and 5:00 to 6:00 PM, with a trough at night. The duration of PSVT also did not show a uniform distribution throughout the 24-h period; it increased significantly during the daytime, with a peak between 1:00 and 2:00 PM, another peak between 6:00 and 7:00 PM, and a significant reduction at night.

CONCLUSIONS

The onset and duration of PSVT showed a circadian variation. However, the time-oriented antiarrhythmic therapy for preventing PSVT needs further study.

Mutation of a gene encoding a protein with extracellular matrix motifs in Usher syndrome type IIa

Usher syndrome type IIa (OMIM 276901), an autosomal recessive disorder characterized by moderate to severe sensorineural hearing loss and progressive retinitis pigmentosa, maps to the long arm of human chromosome 1q41 between markers AFM268ZD1 and AFM144XF2. Three biologically important mutations in Usher syndrome type IIa patients were identified in a gene (USH2A) isolated from this critical region. The USH2A gene encodes a protein with a predicted size of 171.5 kilodaltons that has laminin epidermal growth factor and fibronectin type III motifs; these motifs are most commonly observed in proteins comprising components of the basal lamina and extracellular matrixes and in cell adhesion molecules.

Cardiac troponin T, creatine kinase, and its isoform release after successful percutaneous transluminal coronary angioplasty with or without stenting

BACKGROUND

Cardiac troponin T is a sensitive and specific marker for the detection of minor myocardial injury. However, it has been rarely used to monitor myocardial injury after coronary stenting. The purpose of the study was to measure troponin T after apparently successful percutaneous transluminal coronary angioplasty (PTCA) with or without coronary stenting and to compare its result with serum creatine kinase and its isoform, CKMB.

METHODS

The incidence of cardiac troponin T elevation was compared with that of creatine kinase or CKMB in 120 consecutive patients with symptomatic ischemia undergoing visually successful PTCA with (n = 59) or without stenting (n = 61). Troponin T, creatine kinase, and CKMB were measured before, immediately after, and 18 to 24 hours after the procedures were performed.

RESULTS

No patient had abnormal troponin T, creatine kinase, or CKMB levels before and immediately after the procedures. Moreover, no patient showed electrocardiographic evidence of myocardial infarction. Troponin T was elevated in 17 patients at 18 to 24 hours after coronary stenting and in eight patients after PTCA. Both creatine kinase and CKMB were elevated in five patients after coronary stenting and in three patients after PTCA. The frequency of abnormal troponin T levels was significantly higher than that of creatine kinase or CKMB after coronary interventions (21% vs 6.7%; p < 0.01), and it was significantly higher after stenting when compared with angioplasty alone (29% vs 13%; p < 0.05). Patients with abnormal troponin T levels were more likely to undergo repeat revascularization than those without (24% vs 6%; p < 0.01).

CONCLUSION

Cardiac troponin T is more sensitive than creatine kinase and CKMB in detecting minor myocardial injury after coronary interventions. The incidence of troponin T release is higher in the patients undergoing stent implantation than in patients treated with angioplasty alone.

Comparisons of quality of life and cardiac performance after complete atrioventricular junction ablation and atrioventricular junction modification in patients with medically refractory atrial fibrillation

OBJECTIVES

This study compared the long-term effects of complete atrioventricular junction (AVJ) ablation with those of AVJ modification in patients with medically refractory atrial fibrillation (AF).

BACKGROUND

Comparisons between the long-term effects of AVJ ablation with those of AVJ modification in patients with medically refractory AF have not been systematically studied.

METHODS

Sixty patients with medically refractory AF were randomly assigned to receive complete AVJ ablation with permanent pacing or AVJ modification. Subjective perception of quality of life (QOL) was assessed by a semiquantitative questionnaire before and 1 and 6 months after ablation. Cardiac performance was evaluated by echocardiography and radionuclide angiography within 24 h (baseline) and at 1 and 6 months after ablation.

RESULTS

Both methods were associated with significant improvement in general QOL and a significant reduction in the frequency of major symptoms and symptoms during attacks. The frequency of hospital admission and emergency room visits and antiarrhythmic drug trials significantly decreased after ablation in both groups. However, patients after complete AVJ ablation had a significantly greater improvement in general QOL and a significantly reduced frequency of major symptoms and symptoms during attacks (including palpitation, dizziness, chest oppression, blurred vision and syncope). Left ventricular (LV) systolic function and the ability to perform activities of daily life significantly improved after ablation in patients with depressed LV function in both groups. All improvements after ablation or modification were maintained over the 6-month follow-up period.

CONCLUSIONS

AVJ ablation with permanent pacing, as compared with AVJ modification, had a significantly greater ability to decrease the frequency of attacks and the extent of symptoms of AF, and the patients who received this procedure were more satisfied with their general well-being.

Transient ST elevation and left ventricular asynergy associated with normal coronary artery and Tc-99m PYP Myocardial Infarct Scan in subarachnoid hemorrhage

A 72-year-old woman who presented with transient electrocardiographic ST segment elevation and left ventricular asynergy in an acute phase of subarachnoid hemorrhage was found to have normal coronary angiogram and normal Tc-99m PYP myocardial infarct scan. These findings suggested that noninvasive Tc-99m PYP myocardial infarct scan could substitute coronary angiogram for differentiating wall motion and electrocardiographic abnormalities secondary to subarachnoid hemorrhage from those caused by coronary artery disease in patients with subarachnoid hemorrhage.

Cyclic strain-induced reactive oxygen species involved in ICAM-1 gene induction in endothelial cells

Vascular endothelial cells (ECs) are constantly subjected to pressure-induced strain. We have previously demonstrated that strain can induce intercellular adhesion molecule-1 (ICAM-1) expression in ECs. The molecular mechanisms of gene induction by strain, however, remain unclear. Recent evidence suggests that intracellular reactive oxygen species (ROS) may act as second messengers. The potential role of ROS in strain-induced ICAM-1 expression was examined. ECs grown on a flexible membrane base were deformed with various sinusoidal negative pressures to produce an average strain of 12%. Cyclic strain induced an increase in intracellular ROS measured by fluorescent intensity of dichlorofluorescein formed after peroxidation. Maximal levels of ROS were seen after 30 minutes. Levels subsequently decreased but remained elevated compared with unstrained groups. Concomitantly, a sustained increase of H2O2 decomposition activity was observed in strained ECs. Both ROS and H2O2 decomposition activity returned to basal levels after removal of the strain. ECs treated with an antioxidant (N-acetylcysteine or catalase) inhibited strain-induced ROS generation and ICAM-1 mRNA levels followed by decreased ICAM-1 expression on EC surfaces. This inhibition may account for the reduced monocytic cell adhesion in antioxidant-treated ECs but not in strained controls. Our findings indicate that cyclic strain-induced monocyte adhesion to ECs is mediated, at least in part, by an increase of ICAM-1 gene expression via the elevation of ROS levels in strained ECs. Our results support the importance of intracellular ROS in the modulation of hemodynamic force-induced endothelial responses.

Atrioventricular node reentrant tachycardia in patients with a prolonged AH interval during sinus rhythm: clinical features, electrophysiologic characteristics and results of radiofrequency ablation

Among a consecutive series of 600 patients who underwent radiofrequency catheter ablation for AV node reentrant tachycardia, 14 patients (age 29-76 years) had a prolonged AH interval during sinus rhythm (172 +/- 18 ms, range 140 to 200). Seven of them had unsuccessful ablation during the previous ablation sessions. Eight patients with anterograde dual AV node pathway physiology received anterograde slow pathway ablation, and the other 6 patients without dual-pathway physiology received retrograde fast pathway ablation. All patients had successful elimination of AV nodal reentrant tachycardia after a mean of 4 +/- 4 radiofrequency applications, power level 36 +/- 6 watts and a pulse duration of 42 +/- 4 seconds. The postablation AH interval remained unchanged. During a follow-up period of 25 +/- 13 months, one patient who received slow pathway ablation developed 2:1 AV block with syncope. As compared with the other 586 patients without a prolonged AH interval, these 14 patients had significantly poorer anterograde AV nodal function and lower incidence of anterograde dual AV node physiology (P < 0.01). We concluded that slow pathway ablation in patients with dual pathway physiology, and retrograde fast pathway ablation in patients without dual pathway physiology were effective and safe in patients with a prolonged AH interval. However, delayed onset of symptomatic AV block is possible and careful follow-up is necessary.

Atrioventricular node reentrant tachycardia in patients with a long fast pathway effective refractory period: clinical features, electrophysiologic characteristics, and results of radiofrequency ablation

Twenty-two patients (group 1) with AV node reentrant tachycardia and a baseline fast pathway effective refractory period (ERP) > or = 500 msec were compared with 30 consecutive patients (group 2) with AV node reentrant tachycardia and a fast pathway ERP < 500 msec. Both groups underwent slow pathway ablation. In the patients with complete elimination of slow pathway, the fast pathway ERP and shortest 1:1 conduction cycle length shortened significantly after ablation but was greater in group 1 (n = 14) than in group 2 (n = 21) (125 +/- 78 msec vs 48 +/- 29 msec, p < 0.001 and 103 +/- 72 msec vs 52 +/- 30 msec, p < 0.001, respectively). In group 1, the shortening of fast pathway ERP was correlated to baseline difference between anterograde fast and anterograde slow ERP (r = 0.806, p < 0.001, slope = 1.08), and the shortening of fast pathway shortest 1:1 conduction cycle length was correlated to baseline difference between anterograde fast and anterograde slow shortest 1:1 conduction cycle length (r = 0.885, p < 0.001, slope = 1.47). During follow-up bradycardia did not develop in any patient and no one required pacing. This shortening of the fast pathway ERP and shortest 1:1 conduction cycle length after complete elimination of slow pathway reduced the concern of subsequent impairment of AV node conduction.

Radiofrequency catheter modification of sinus node for inappropriate sinus tachycardia: a case report

We present here, the case of a 22-year-old male suffering from persistent tachycardia for the past 3 years. His resting pulse rate was rarely below 100 beats/min, and it frequently increased to as high as 150 beats/min even after a minimal of activity. Associated symptoms included palpitation, chest tightness, dyspnea and presyncope, either during rest or with exercise. Propranolol and verapamil could not control the tachycardia. The application of radiofrequency energy to an area in the superior right atrium that demonstrated a discrete electrogram with earliest endocardial activation during tachycardia resulted in a decrease in sinus rate from 120 beats/min to 70 beats/min. Follow-up on Holter monitor, performed one month later, demonstrated an average heart rate of 84 beats/min (range 60-125). In exercise tolerance test, the patient exercised for 9 minutes, achieving a maximum heart rate of 140 beats/min. This patient remained asymptomatic without any antiarrhythmic drug during the 3-month follow-up period. Medical management in case of patients showing disabling inappropriate sinus tachycardia refractory, sinus node modification could be considered as an suitable alternative to complete atrioventricular junctional ablation.

Cyclic strain-induced monocyte chemotactic protein-1 gene expression in endothelial cells involves reactive oxygen species activation of activator protein 1

Endothelial cells (ECs) are constantly exposed to blood pressure-induced mechanical strain. We have previously demonstrated that cyclic strain can induce gene expression of monocyte chemotactic protein-1 (MCP-1). The molecular mechanisms of gene induction by strain, however, remain unclear. Recent evidence indicates that intracellular reactive oxygen species (ROS) can act as a second messenger for signal transduction and thus affect gene expression. The potential role of ROS in strain-induced MCP-1 expression was investigated. ECs under cyclic strain induced a sustained elevated production of intracellular superoxide. ECs under strain or pretreated with either H2O2 or xanthine oxidase/hypoxanthine induced MCP-1 expression. Strain- or oxidant-induced MCP-1 mRNA levels could be inhibited by treating ECs with catalase or antioxidant N-acetyl-cysteine (NAC). Functional analysis of MCP-1 promoter and site-specific mutations indicates that the proximal tissue plasminogen activator-responsive element (TRE) in the -60-bp promoter region is sufficient for strain or H2O2 inducibility. Electrophoretic mobility shift assays demonstrated an increase of nuclear proteins binding to TRE sequences from ECs subsequent to strain or H2O2 treatment. NAC or catalase pretreatment of ECs inhibited the strain- or H2O2-induced AP-1 binding. These results clearly indicate that cyclic strain inducibility of MCP-1 in ECs uses the interaction of AP-1 proteins with TRE sites via the elevation of intracellular ROS levels in strained ECs. These findings emphasize the importance of intracellular ROS in the modulation of hemodynamic force-induced gene expression in vascular ECs.

Electrophysiologic characteristics and radiofrequency catheter ablation in atrioventricular node reentrant tachycardia with second-degree atrioventricular block

INTRODUCTION

Detailed electrophysiologic study of AV nodal reentrant tachycardia (AVNRT) with 2:1 AV block has been limited.

METHODS AND RESULTS

Six hundred nine consecutive patients with AVNRT underwent electrophysiologic study and radiofrequency catheter ablation of the slow pathway. Twenty-six patients with 2:1 AV block during AVNRT were designated as group I, and those without this particular finding were designated as group II. The major findings of the present study were: (1) group I patients had better anterograde and retrograde AV nodal function, shorter tachycardia cycle length (during tachycardia with 1:1 conduction) (307 +/- 30 vs 360 +/- 58 msec, P < 0.001), and higher incidence of transient bundle branch block during tachycardia (18/26 vs 43/609, P < 0.001) than group II patients; (2) 21 (80.8%) group I patients had alternans of AA intervals during AVNRT with 2:1 AV block. Longer AH intervals (264 +/- 26 vs 253 +/- 27 msec, P = 0.031) were associated with the blocked beats. However, similar HA intervals (51 +/- 12 vs 50 +/- 12 msec, P = 0.363) and similar HV intervals (53 +/- 11 vs 52 +/- 12, P = 0.834) were found in the blocked and conducted beats; (3) ventricular extrastimulation before or during the His-bundle refractory period bundle could convert 2:1 AV block to 1:1 AV conduction.

CONCLUSIONS

Fast reentrant circuit, rather than underlying impaired conduction of the distal AV node or infranodal area, might account for second-degree AV block during AVNRT. Slow pathway ablation is safe and effective in patients who have AVNRT with 2:1 AV block.