Long-term outcome in patients receiving permanent pacemaker implantation for atrioventricular block: Comparison of VDD and DDD pacing.

A permanent pacemaker (PPM) with dual chamber pacing (DDD) offers atrioventricular synchronization for patients with atrioventricular block (AVB). Single lead atrial synchronous ventricular pacing mode (VDD) is an alternative, but there are concerns about its efficacy and risk of atrial undersensing. Whether VDD can be a good alternative in patients with AVB remains unknown. The aim of the present study was to compare the long-term risk of mortality of VDD with DDD pacing.A total of 207 patients undergoing PPM implantations for AVB with VDD mode were enrolled from 2000 to 2013. Another 828 age- and sex-matched patients undergoing DDD implantations during the same period of time were selected as the control group in a 1 to 4 ratio. The study endpoint was mortality.A total of 1035 patients (64.3% male) were followed up for 46.5 ±â€Š43.2 months. The mean ages were 75.0 years for VDD, and 74.9 years for DDD. The Kaplan-Meier survival analysis showed no significant difference in long-term survival between the VDD and DDD groups (log-rank P = 0.313). After adjustment for baseline characteristics, the VDD and DDD groups had a similar long-term prognosis with an adjusted hazard ratio of 0.875 (P = 0.445). Further analyses for the risk of cardiovascular and noncardiovascular deaths also showed no significant differences between the 2 groups.The long-term prognosis of VDD mode is comparable to that of DDD mode. Single lead VDD can be considered as an alternative choice in patients with AVB without sinus nodal dysfunction.

Long-term prognosis of patients older than ninety years after permanent pacemaker implantation: does the procedure save the patients?

BACKGROUND: The implantation of a permanent pacemaker (PPM) is life-saving for patients with life-threatening bradycardia. However, the effectiveness and prognosis of PPM implantations for extremely old patients (≥ 90 years old) have not been investigated. METHODS: From 2001-2012, a total of 108 patients older than 90 years were identified from 2630 consecutive patients receiving PPM implantations in our hospital as the study group. For each study patient, 4 age-, sex-, and comorbidity-matched subjects who did not have the diagnoses of bradyarrhythmias indicated for PPM implantations were selected from the "Taiwan National Health Research Database" to constitute the control group (n = 432). The study end point was all-cause mortality. RESULTS: The median age of the study population was 91 (interquartile range, 90-93) years. Among the PPM group, 45 patients died during the follow-up with an annual mortality rate of 18.7%. The risk of mortality did not differ significantly between the study and control groups with a hazard ratio of 1.020 (95% confidence interval, 0.724-1.437; P = 0.912) after the adjustment for age and sex. Procedure-related complications occurred in 7.4% of the patients receiving PPM implants, and pocket hematoma was the most common. The preimplantation history of heart failure and cerebrovascular accident, rather than age, were significant predictors of mortality among PPM recipients. CONCLUSIONS: Nonagenarians with severe bradyarrhythmias could retain the same life expectancies as those without bradyarrhythmias through PPM implantations. Extremely old age (≥90 years) should not be a barrier for PPM implants when indications are present.

Long-Term Prognosis in Recipients of Implantable Cardioverter-Defibrillators for Secondary Preventions in Taiwan - A Multicenter Registry Study.

BACKGROUND: The use of an implantable cardioverter-defibrillator (ICD) has a proven capacity to prevent sudden cardiac death (SCD), and can also improve survival duration in well-selected patients. The goal of the present study was to investigate the long-term prognosis and predictors of mortalities among ICD recipients in Taiwan. METHODS: From 1998 to 2009, 238 consecutive patients who experienced SCDs or life-threatening ventricular tachyarrhythmias without correctable causes and received ICD implantations in 3 medical centers (Taipei, Taichung and Kaohsiung Veterans General Hospital) were enrolled in this study. The clinical endpoint was defined as the occurrence of all-cause mortality during the follow-up. RESULTS: The mean age of the patients was 63.0 ± 15.3 years, and 76.5% of them were male. Ischemic cardiomyopathy was the leading cause for the ICD implantations (39.1%). During the mean follow-up duration of 36.8 ± 29.8 months, there were 48 patients (20.2%) who died. Patients with structural heart diseases had a higher mortality rate than those without such diseases. Additionally, old age, low left ventricular ejection fraction (LVEF) and a history of diabetes mellitus (DM) were significant predictors of mortality. The optimal cutoff values for age (70 years) and LVEF (40%) in predicting mortality were further identified using the receiver operating characteristic curves. CONCLUSIONS: Based on the ICD registry from 3 medical centers in Taiwan, the annual mortality rate was around 6.6% and was higher in those patients with structural heart diseases. We observed that old age, low LVEF and a history of DM were significant predictors of mortality. KEY WORDS: Implantable cardioverter-defibrillator; Mortality; Predictor; Taiwan.

Prospective randomized study to assess the efficacy of site and rate of atrial pacing on long-term progression of atrial fibrillation in sick sinus syndrome: Septal Pacing for Atrial Fibrillation Suppression Evaluation (SAFE) Study.

BACKGROUND: Atrial-based pacing is associated with lower risk of atrial fibrillation (AF) in sick sinus syndrome compared with ventricular pacing; nevertheless, the impact of site and rate of atrial pacing on progression of AF remains unclear. We evaluated whether long-term atrial pacing at the right atrial (RA) appendage versus the low RA septum with (ON) or without (OFF) a continuous atrial overdrive pacing algorithm can prevent the development of persistent AF. METHODS AND RESULTS: We randomized 385 patients with paroxysmal AF and sick sinus syndrome in whom a pacemaker was indicated to pacing at RA appendage ON (n=98), RA appendage OFF (n=99), RA septum ON (n=92), or RA septum OFF (n=96). The primary outcome was the occurrence of persistent AF (AF documented at least 7 days apart or need for cardioversion). Demographic data were homogeneous across both pacing site (RA appendage/RA septum) and atrial overdrive pacing (ON/OFF). After a mean follow-up of 3.1 years, persistent AF occurred in 99 patients (25.8%; annual rate of persistent AF, 8.3%). Alternative site pacing at the RA septum versus conventional RA appendage (hazard ratio=1.18; 95% confidence interval, 0.79-1.75; P=0.65) or continuous atrial overdrive pacing ON versus OFF (hazard ratio=1.17; 95% confidence interval, 0.79-1.74; P=0.69) did not prevent the development of persistent AF. CONCLUSIONS: In patients with paroxysmal AF and sick sinus syndrome requiring pacemaker implantation, an alternative atrial pacing site at the RA septum or continuous atrial overdrive pacing did not prevent the development of persistent AF. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. UNIQUE IDENTIFIER: NCT00419640.

Baicalein protects against retinal ischemia by antioxidation, antiapoptosis, downregulation of HIF-1α, VEGF, and MMP-9 and upregulation of HO-1.

PURPOSE: Retinal ischemia-associated ocular disorders are vision threatening. This study examined whether the flavonoid baicalein is able to protect against retinal ischemia/reperfusion. METHODS: Using rats, the intraocular pressure was raised to 120 mmHg for 60 min to induce retinal ischemia. In vitro, an ischemic-like insult, namely oxidative stress, was established by incubating dissociated retinal cells with 100 µM ascorbate and 5 µM FeSO4 (iron) for 1 h. The rats or the dissociated cells had been pretreated with baicalein (in vivo: 0.05 or 0.5 nmol; in vitro: 100 µM), vehicle (1% ethanol), or trolox (in vivo: 5 nmol; in vitro: 100 µM or 1 mM). The effects of these treatments on the retina or the retinal cells were evaluated by electrophysiology, immunohistochemistry, terminal deoxynucleotidyl-transferase-mediated dUTP nick end-labeling (TUNEL) staining, Western blotting, or in vitro dichlorofluorescein assay. In addition, real-time-polymerase chain reaction was used to assess the retinal expression of hypoxia-inducible factor-1α (HIF-1α), matrix metalloproteinase-9 (MMP-9), vascular endothelium growth factor (VEGF), and heme oxygenase-1 (HO-1). RESULTS: The retinal changes after ischemia included a decrease in the electroretinogram b-wave amplitude, a loss of choline acetyltransferase immunolabeling amacrine cell bodies/neuronal processes, an increase in vimentin immunoreactivity, which is a marker for Müller cells, an increase in apoptotic cells in the retinal ganglion cell layer linked to a decrease in the Bcl-2 protein, and changes in the mRNA levels of HIF-1α, VEGF, MMP-9, and HO-1. Of clinical importance, the ischemic detrimental effects were concentration dependently and/or significantly (0.05 nmol and/or 0.5 nmol) altered when baicalein was applied 15 min before retinal ischemia. Most of all, 0.5 nmol baicalein significantly reduced the upregulation of MMP-9; in contrast, 5 nmol trolox only had a weak attenuating effect. In dissociated retinal cells subjected to ascorbate/iron, there was an increase in the levels of reactive oxygen species, which had been significantly attenuated by 100 µM baicalein and trolox (100 µM or 1 mM; a stronger antioxidative effect at 1 mM). CONCLUSIONS: Baicalein would seem to protect against retinal ischemia via antioxidation, antiapoptosis, upregulation of HO-1, and downregulation of HIF-1α, VEGF, and MMP-9. The antioxidative effect of baicalein would appear to play a minor role in downregulation of MMP-9.

How Long Should Prophylactic Antibiotics be Prescribed for Permanent Pacemaker Implantations? One Day versus Three Days.

BACKGROUND: The implantation of a pacemaker is frequently a life-saving procedure. However, the process of implantation may carry an uncommon but potentially life-threatening infective complication. The prescription of prophylactic antibiotics is an effective way to reduce the risk of infection. The aim of the present study was to investigate the efficacy of 2 prophylactic antibiotic schemes and the possible risk factors associated with device-related infections. METHODS: A total of 194 consecutive patients who received permanent pacemaker (PPM) implantations were enrolled in this study. Prophylactic antibiotics were prescribed for every patient with a duration of either 1 day or 3 days. The follow-up period was 3 months, and any event of device-related infection was recorded. RESULTS: Out of the total 194 patients, there were 5 patients who experienced infective complications after PPM implantation (1 patient in the 1-day group and 4 patients in the 3-day group). The rate of infective complications showed no significant difference between the 2 kinds of antibiotic regimens (1.7% vs. 2.9%, p > 0.99). In the multivariate analysis, only the presence of pocket hematoma was an independent risk factor for infective complications (odds ratio = 3.14, p = 0.018). CONCLUSIONS: Our study showed that the efficacies for prevention of PPM-related infections were similar between the 1-day and 3-day regimens of prophylactic antibiotics. Pocket hematoma was an independent risk factor of infective complications, and a longer duration of antibiotic treatment may be considered for these patients. Otherwise, a 1-day course of antibiotic prophylaxis may be effective enough to prevent device-related infections, and may further reduce the lengths of hospitalizations. KEY WORDS: Complication; Infection; Permanent pacemaker implantation; Prophylatic antibiotics.

Relationship between temperature change and the requirement for a permanent pacemaker implantation in bradyarrhythmias.

Some cardiovascular diseases are associated with seasonal or meteorological factors. We tried to identify the relationship between meteorological parameters and the requirement for a permanent pacemaker (PPM) implantation for advanced sinus node dysfunction (SND) and atrioventricular block (AVB). This study enrolled 656 patients (67% male, age = 76 ± 11 years) who underwent a PPM implantation due to SND or AVB from January 2004 to December 2008. Using daily temperature, barometric pressure, humidity, and daylight hour records from Taipei, we evaluated the effect of these meteorological parameters within different time periods on the occurrence of SND and AVB. There were 355 patients in the SND group and 301 in the AVB group. In the AVB group, more patients presented in the spring than in other seasons (P = 0.003). In the SND group, there was no relationship with the seasons (P = 0.137). The proportion of patients with AVB did not depend on the average temperature, barometric pressure, humidity, or daylight hours within 3, 7, and 14 days prior to admission (P = NS). A temperature change of greater than 11°C within 30 days prior to admission was associated with a significantly higher proportion of patients with advanced AVB compared to those with advanced SND (P = 0.009). Extreme change in temperature was the most independent predictor of the development of advanced AVB. The peak occurrence of advanced AVB was in the spring. The occurrence of advanced AVB was associated with extreme temperature changes within 30 days, especially in the spring.

Trends of temporary pacemaker implant and underlying disease substrate.

BACKGROUND: To evaluate contemporary trends of clinical characteristics, etiologies, and underlying diseases, and their relationship between different bradyarrhythmias in patients undergoing temporary pacemakers (TPMs). METHODS: This study included 509 patients (77 ± 11 year, 74% males) with symptomatic bradyarrhythmias requiring TPMs between 2002 and 2008. Demographics, electrocardiographic indications, etiologies, underlying diseases, and the outcome of permanent pacemaker (PPM) implants within 30 days were analyzed. RESULTS: Atrioventricular conduction dysfunction (AVCD) (64.0%) dominated in all bradyarrhythmias, with idiopathic degeneration (61%) as its major etiology. Antiarrhythmic drug (38%) was the leading cause in sinoatrial node dysfunction (SAND). There was an increasing trend in AVCD, while a decreasing trend in SAND. Regarding etiologies for TPM, an increasing trend was found in idiopathic degeneration, whereas a decreasing trend in acute coronary syndrome (ACS). Idiopathic degeneration had an odds ratio (OR) of 1.9 for AVCD (P = 0.001), whereas electrolyte/acid-base disturbances (OR = 3.7, P = 0.001), ß-blockers (OR = 2.4, P = 0.002), and chronic renal disease (OR = 1.9, P = 0.01) were associated with SAND. Patients with intrinsic etiologies for TPM had a high incidence of PPM implantation within 30 days than those with extrinsic causes (67.5% vs 3.8%, P < 0.0001) CONCLUSION: Increasing trends in patients requiring TPMs were observed in the elderly patients and those with AVCD and idiopathic degeneration, while decreasing trends were observed in those with SAND and ACS. Idiopathic degeneration was associated with AVCD, whereas extrinsic etiologies were related to SAND. Patients with intrinsic etiologies had a higher incidence of PPM implantation than those with extrinsic factors for TPM.

Predictors of inappropriate atrial sensing in long-term VDD-pacing systems.

AIMS: The efficacy and stability of the atrial electrode sensing function is essential for maintaining atrioventricular (AV) synchrony. This study aimed to explore the long-term reliability and causes of the long-term sensing failure of VDD systems. METHODS AND RESULTS: We enrolled all the patients with complete or high-degree AV block who received VDD pacemakers between August 1994 to January 2006 and who were followed up for more than 12 months. The interrogation parameters, including the atrial potentials (APs) and AV-synchrony ratio were acquired immediately post-implantation and at 3-6 month intervals thereafter. An inappropriate atrial sensing efficacy was defined as an AV-synchrony ratio of <90%. Totally 157 patients (70 +/- 12 years, 103 males) were enrolled into the study with a follow-up for 4.9 +/- 2.5 years. Twenty-six patients (16.6%) suffered from inappropriate atrial sensing. According to a Kaplan-Meier analysis, the incidence of inappropriate atrial sensing was higher in the patients with an age > or =72 years old (P = 0.047), mean AP during the implantation of <3.0 mV (P = 0.015), concomitant use of non-dihydropyridine calcium channel blockers (CCBs) (P = 0.003), and atrial fibrillation (AF) (P < 0.001). A Cox regression analysis showed that non-dihydropyridine CCBs (hazard ratio, 3.255; 95% confidence interval, 1.148-9.227, P = 0.026) and AF (hazard ratio, 6.507; 95% confidence interval, 2.478-17.104, P < 0.001) predicted inappropriate atrial sensing. CONCLUSION: VDD pacing is a reliable pacing modality. However, we should monitor the pacemaker sensing function in the patients with the concomitant use of non-dihydropyridine CCBs and AF.

A prospective randomized study to assess the efficacy of rate and site of atrial pacing on long-term development of atrial fibrillation.

The Septal Pacing for Atrial Fibrillation Suppression Evaluation (SAFE) study is a single-blinded, parallel randomized designed multicenter study in pacemaker indicated patients with paroxysmal atrial fibrillation (AF). The objective is to evaluate whether the site of atrial pacing--conventional right atrial appendage versus low atrial septal--with or without atrial overdrive pacing will influence the development of persistent AF. The study will provide a definitive answer to whether a different atrial pacing site or the use of AF suppression pacing or both can give incremental antiarrhythmic benefit when one is implanting a device for a patient with a history of paroxysmal AF.

Acute effects of dual-chamber pacing on the left ventricular systolic function and relaxation in patients with advanced AV block and sick sinus syndrome.

BACKGROUND: Abnormal activation of the ventricles via right ventricular apical pacing deteriorates cardiac function, which may explain the increased mortality of patients with congestive heart failure receiving permanent pacemakers. We hypothesized that pacing at alternative sites may cause less detrimental effects on the cardiac function. METHODS: Five symptomatic patients with either advanced AV block (n = 4) or sick sinus syndrome with normal left ventricular (LV) function (n = 1) were studied. During cardiac catheterization, LV pressure was recorded with a high-fidelity catheter-tipped transducer. Baseline rhythms were sinus rhythm or VVI pacing. Sequential VDD pacing with variable AV intervals was performed at the right ventricular apex (RVA), right ventricular septum (RVS), right ventricular outflow tract (RVOT) and coronary sinus (CS). LV systolic function was assessed by calculating dP/dt(max) and LV diastolic function was indexed by calculating the exponential isovolumic relaxation constant (Tau). Percentage changes (mean +/- SE) from baseline to pacing were measured. RESULTS: RVA pacing reduced dP/dt(max) (-0.8 +/- 8.4%) and prolonged Tau (7.0 +/- 5.6%); RVS pacing enhanced dP/dt(max) (20.7 +/- 15.3%) and shortened Tau (-10.4 +/- 9%); RVOT pacing reduced dP/dt(max) (-8.0 +/- 20.0%) and shortened Tau (-6.0 +/- 12.2%); CS pacing reduced dP/dt(max) (-11.7 +/- 13.0%) and prolonged Tau (10.5 +/- 11.9%). Our results demonstrated that different pacing sites have different effects on LV contractility and relaxation in patients with normal LV function. CONCLUSION: Since pacing at the RVS preferably increased LV dP/dt(max) and shortened Tau, it may be a better alternative than the RVA.

Influence of methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism, B vitamins and other factors on plasma homocysteine and risk of thromboembolic disease in Chinese.

BACKGROUND: Thromboembolic disease is a major cause of morbidity and mortality in many countries. Our previous study found that Chinese subjects carried the same polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene as described in Western studies. The aim of the present study was to determine the influence of MTHFR polymorphism, B vitamins and other factors on plasma homocysteine (Hcy) levels and risk of thromboembolic disease in Chinese. METHODS: One hundred and six subjects were enrolled into the study. They were categorized into 4 groups: healthy individuals (n = 42); those with diabetes mellitus (n = 20); those with deep vein thrombosis (DVT) (n = 11); and those with coronary artery disease (CAD) (n = 33). Plasma levels of folic acid, vitamins B6 and B12, Hcy, and fasting blood sugar were measured; total cholesterol, triglycerides, complete blood count, and 677 C-->T mutation in MTHFR were determined. RESULTS: Plasma Hcy was lowest in the healthy subjects, higher in diabetics, followed by patients with DVT, and highest in patients with CAD (p < 0.001, ANOVA). MTHFR C677T polymorphism was the common factor affecting plasma logHcy levels in all 4 groups of subjects. Triglycerides affected plasma logHcy in the CAD patients. For the 4 groups as a whole, MTHFR polymorphism, triglycerides, and vitamin B12 were the most significant factors influencing plasma Hcy. CONCLUSION: We suggest that high plasma Hcy is an important risk factor for CAD. Other factors including MTHFR polymorphism, vitamin B12, triglycerides, total cholesterol, and gender might affect Hcy levels in different diseases and conditions.

Long-term efficacy and stability of atrial sensing in VDD pacing.

BACKGROUND: The efficacy and stability of atrial electrode sensing function is essential in maintaining atrioventricular (AV) synchrony and activity response in VDD pacing. Studies to evaluate the relationship between atrial sensing efficacy, stability, and implantation strategy are few. HYPOTHESIS: This study sought to determine the possible predictors, among the recipients' underlying clinical conditions and the implantation strategies used, of achieving the most stable and effective atrial sensing. METHODS: Eighty consecutive adults implanted with VDD pacemakers were studied retrospectively. Atrial electrodes were positioned where the optimal atrial potentials (APs) were measured during implantation. Interrogation parameters, including AV-synchrony ratio, were acquired immediately post implantation, at 1 year, and at 2 years after pacemaker implantation. Appropriate atrial sensing efficacy was defined as AV-synchrony ratio > or = 90%. The stability of atrial sensing was evaluated by the variation ranges of measured APs. RESULTS: The measured APs showed no statistical difference when age, gender, or comorbidity was considered. However, with pacing-lead bending angles < or = 90 degrees, patients may have presented with larger APs and narrower AP variation than patients with obtuse angles. There were no clinical parameters in our study that could have predicted the proper atrial sensing efficacy with an AV-synchrony ratio > or = 90%. CONCLUSIONS: The long-term sensing efficacy and stability of VDD pacing is reliable. More sophisticated implantation strategies may further improve the atrial sensing stability and efficacy in VDD pacing.

Catheter ablation of atrial fibrillation versus atrioventricular junction ablation plus pacing therapy for elderly patients with medically refractory paroxysmal atrial fibrillation.

BACKGROUND: Catheter ablation of atrial fibrillation (AF) has become another nonpharmacologic therapeutic option for medically refractory paroxysmal AF. Whether this method is better than atrioventricular (AV) junction ablation plus pacing therapy is unknown. The purpose of this study was to compare the very long-term (longer than 4 years) clinical outcomes of the 2 methods in elderly patients (>65 years old) with medically refractory paroxysmal AF. METHODS: From January 1995 to December 2001, 71 elderly patients with medically refractory paroxysmal AF were included; group 1 included 32 patients with successful AV junction ablation plus pacing therapy and group 2, 37 patients with successful catheter ablation of AF. RESULTS: After a mean follow-up of more than 52 months, the AF was better controlled in the group 1 patients than group 2 (100% vs 81%, P = 0.013), however, they had a significantly higher incidence of persistent AF (69% vs 8%, P < 0.001) and heart failure (53% vs 24%, P = 0.001). Furthermore, the incidence of ischemic stroke and cardiac death was similar between the 2 groups. Compared with the preablation values, a significant increase in the NYHA functional class (1.7 +/- 0.9 vs 1.4 +/- 0.7, P = 0.01) and significant decrease in the left ventricular ejection fraction (44 +/- 8% vs 51 +/- 10%, P = 0.01) were noted in the group 1 patients, but not in the group 2 patients. CONCLUSIONS: Although AV junction ablation plus pacing therapy better controlled the AF in elderly patients with medically refractory paroxysmal AF, that method was associated with a higher incidence of persistent AF and heart failure than catheter ablation of AF in the very long-term follow-up.

Hemodynamic significance of heart rate in neurally mediated syncope.

BACKGROUND: Vasovagal and vasodepressor syncope are used interchangeably in the literature to describe the common faint syndrome, now collectively named neurally mediated syncope. The significance of heart rate (HR) in these reflex-induced reactions remains unclear. HYPOTHESIS: The study was undertaken to investigate the hemodynamic significance of HR in tilt-induced neurally mediated syncope. METHODS: In all, 113 patients with syncope of unknown etiology were studied by head-up tilt test with invasive hemodynamic monitoring. Thirty-five patients (15 women, 20 men, age range 21 to 72 years) developed syncope and were enrolled for analysis. The hemodynamic data were compared between patients who developed bradycardia (vasovagal group, n = 15) and those without bradycardia (vasodepressor group, n = 20). RESULTS: The baseline hemodynamic data (mean +/- standard deviation) and the hemodynamic responses after 10-min headup tilt were similar between patients in the vasovagal and vasodepressor groups. During syncope, patients with vasovagal reaction developed hypotension and paradoxical bradycardia (HR = 52.4 +/- 5.9 beats/min), while patients with vasodepressor reaction developed a precipitous drop in arterial blood pressure with inappropriate HR (105 +/- 21 beats/min) compensation. Patients with vasovagal syncope manifested a significantly lower cardiac index and a significantly higher systemic vascular resistance index than patients with vasodepressor syncope (1.47 +/- 0.29 vs. 1.97 +/- 0.41 1/min/m2, p < 0.001 and 2098 +/- 615 vs. 1573 +/- 353 dynes x s x cm(-5) x m2, p < 0.003, respectively). A positive correlation existed between HR and cardiac index (r = 0.44, p = 0.008) during syncope in the patients studied. CONCLUSIONS: These findings suggest that the hemodynamic characteristics of vasovagal and vasodepressor reactions are different, and that HR plays a significant role in neurally mediated syncope.

Leukocyte mitochondrial alterations after cardiac surgery involving cardiopulmonary bypass: clinical correlations.

Cardiac surgery with the use of cardiopulmonary bypass (CPB) is known to initiate systemic inflammatory responses that are associated with immune dysregulations, but the pathomechanisms underlying these changes remain elusive. Mitochondrial transmembrane potential (MTP) is an important determinant of leukocytic functions and viability, and may be altered as a part of the cellular responses to systemic inflammatory insults. Therefore, we examined MTP in three subsets of peripheral leukocytes in 18 patients receiving uncomplicated cardiac surgery involving CPB. The MTP of neutrophils and lymphocytes significantly increased, whereas that of monocytes significantly declined, after the surgery. The alterations in leukocytic MTP were transient, normalizing 3 days to 1 week after the surgery, and were accompanied by transient overproduction of intracellular oxidants, including nitric oxide and superoxide. Despite these perturbations, the viability status of leukocytes remained unaltered. Positive correlations were found between the changes of leukocyte MTP and various clinical parameters, implying that leukocyte mitochondrial alterations are parts of the systemic immune perturbations induced by the bypass surgery.

Development of atrial fibrillation in patients with atrioventricular block after atrioventricular synchronized pacing.

Many studies have evidenced an increased incidence of AF in patients receiving single chamber ventricular pacing (VVI) when compared with those undergoing an atrial-based system (AAI or DDD). However, the difference in incidence of AF between two atrial-based systems (VDD, DDD) in patients with AV block was still controversial. This study was conducted to compare the development of AF between different modes of pacemakers (VDD and DDD) in patients with symptomatic AV block. A retrospective review was conducted of the detailed records of all consecutive patients who received permanent pacemakers due to symptomatic bradycardia from March 1995 to March 2000. The occurrence of AF was documented when there was presence of AF in the free-run or 12-lead ECG, any ECG strips, or persistent AF on 24-hour Holter ECG during the follow-up. The study included 152 patients (44 women, 108 men; mean age 73). The patients were divided into two groups: VDD (n = 100) and DDD (n = 52). The mean follow-up was 48.9 +/- 22.9 months. The incidence of AF was 7.9%. A higher incidence of AF was noted in the DDD group (15.4%) when compared with the VDD group (4.0%, P = 0.023). The incidence of development of AF in patients with AV block was higher in those receiving DDD cardiac pacing when compared with those who received the VDD system. The authors suggest that VDD pacing may be a better choice than the DDD system for patients with AV block, but without clinical evidence of sinus node dysfunction, and if an atrial lead is required, it should be placed close to the Bachmann's bundle.

Characteristics of Chinese patients with symptomatic Brugada syndrome in Taiwan.

Since 1992, the Brugada syndrome has been increasingly recognized worldwide, although its incidence and distribution remain unclear. In Asia, several cases have been reported in Japan, Thailand, Singapore, and Vietnam. However, little information is available from the Chinese population. Since June 1997, we have identified 10 patients with the diagnosis of the Brugada syndrome from six hospitals in Taiwan. All patients were male with the mean age of 46 +/- 7 years (range 36-61). They all had a normal chemistry profile, coronary angiography and echocardiography. Clinical presentations varied from seizure and syncope to sudden cardiac death. MRI and ultrafast CT of the heart did not show any abnormalities. Sustained ventricular tachycardia/ventricular fibrillation (VF) was induced in 7 of 8 patients who underwent an electrophysiologic study. The pharmacological provocation test was positive in 4 of 5 patients. One of the 4 patients who had a genetic study showed SCN5A gene mutation. An implantable cardioverter defibrillator (ICD) was implanted in 8 patients. During a mean follow-up of 29 +/- 17 months (range 2-54), 3 of 8 patients who had an ICD received appropriate ICD discharges after implantation. These 3 patients who were subsequently treated with antiarrhythmic agents have had no further recurrent ICD discharges. Two patients who refused ICD implantation are alive and well without taking antiarrhythmic agents. Our study showed that the clinical characteristics of our patients are similar to those described in the literature and that ICD is an effective treatment modality for patients with recurrent VF. However, antiarrhythmic agents may be beneficial for suppressing arrhythmia recurrences in selected patients.

Impairment of coronary microvascular function in patients with neurally mediated syncope.

Recent evidence suggests that myocardial ischemia may occur in patients with neurally mediated syncope and normal coronary angiograms. This study was conducted to evaluate if coronary microvascular function is impaired in such patients. Coronary hemodynamic studies and head-up tilt table tests (HUTs) were performed on 30 consecutive patients with normal coronary angiograms and recurrent syncope. Another ten subjects with atypical chest pain and no evidence of myocardial ischemia or syncope served as a control. Great cardiac vein flow (GCVF) and coronary sinus flow (CSF) were measured by the thermodilution method at baseline and after dipyridamole infusion (0.56 mg/kg i.v. for 4 minutes). Coronary flow reserve (CFR), derived from CSF and GCVF, was significantly lower in the 15 patients with positive HUT than in the other 15 patients with negative HUT (1.75 +/- 0.48 vs 2.64 +/- 0.8, P < 0.01 and 2.29 +/- 0.45 vs 3.07 +/- 0.63, P < 0.01, respectively). Ischemic-like ECG was noted during treadmill exercise test in 40% of the former and in 7% of the latter group (P = 0.01). There was no significant difference in CFR between patients with negative HUT and control subjects. Coronary microvascular function was impaired in syncopal patients with positive HUT and relatively preserved in those with negative HUT, suggesting the possible linkage between coronary microvascular dysfunction and the development of neurally mediated syncope.

Congenital absence of the left circumflex coronary artery.

We report a rare case of congenital coronary artery anomaly with recurrent chest pain. A 44-year-old Taiwanese female patient presented with exertional chest pain that had lasted for 2 years. An electrocardiogram showed right axis deviation and an rS pattern in leads I and aVL, and an exercise stress test was inconclusive. A thallium-201 myocardial perfusion study revealed perfusion defects in the septal and inferior walls which normalized in the delayed imaging. Coronary angiography revealed the absence of a left circumflex coronary artery and a superdominant right coronary artery with terminal branches supplying the left ventricular inferior and posterolateral walls. An aortogram revealed no evidence of the existence of a left circumflex coronary artery. Administration of nitrates and calcium antagonists could not ameliorate her symptoms, but she remained stable during ordinary activity. In young premenopausal female patients who present with symptoms suggestive of angina pectoris and a positive stress test, congenital anomaly of the coronary artery should be considered and an angiographic study should be performed.