Paroxysmal atrial fibrillation with high vs. low arrhythmia burden: atrial remodelling and ablation outcome.

AIMS: The relation between atrial tachyarrhythmia (ATA) burden in paroxysmal atrial fibrillation (AF), atrial remodelling, and efficacy of catheter ablation (CA) is unknown. We investigated whether high vs. low-burden paroxysmal AF patients have distinct clinical characteristics or electro-mechanical properties of the left atrium (LA) and whether burden impacts outcome of CA. METHODS AND RESULTS: Atrial tachyarrhythmia burden, defined as the percentage of time spent in ATA, was assessed by insertable cardiac monitors in 105 patients before and after CA. Clinical characteristics and electro-mechanical properties of LA were compared between patients with high vs. low ATA burden. Catheter ablation efficacy was assessed by reduction in ATA burden and 1-year freedom from any ATA. Median ATA burden was 2.7% (highest tertile 9.3%). Clinical characteristics and electrical properties of LA (refractoriness, conduction velocity, low voltage) did not differ between high (≥9.3%) vs. low ATA burden (<9.3%) patients. High ATA burden patients had larger LA diameter (46.5 ± 6 vs. 42.5 ± 6mm, P < 0.01), volume (93.8 ± 22 vs. 80.4 ± 21mL, P = 0.01), and lower LA reservoir and contractile strain (19.7 ± 6 vs. 24.7 ± 6%, P < 0.01; 10.3 ± 3 vs. 12.8 ± 4%, P = 0.01). Catheter ablation reduced ATA burden by 100% (100-100) in both groups (P = 1.0). Freedom from ATA after CA was equally high (83% vs. 89%, P = 0.38). CONCLUSION: Paroxysmal AF patients with high ATA burden have altered LA mechanical properties, reflected by larger size and impaired function. Despite mechanical remodelling of the atria, they are excellent responders to CA. Most likely the lack of fibrosis and/or advanced electrical remodelling explain why pulmonary veins remain the dominant trigger for AF in this patient cohort.

VT Recurrence After Ablation: Incomplete Ablation or Disease Progression? A Multicentric European Study.

AIM: To determine whether ventricular tachycardia (VT) recurrences in arrhythmogenic RV cardiomyopathy (ARVC) and nonischemic cardiomyopathy (NICM) are related to incomplete ablation or disease progression. METHODS: ARVC and NICM patients with two substrate maps of the same diseased ventricle with an interprocedural delay of ≥12 months were included. Disease progression was defined as ≥1 factor: scar area progression (PROG, +5%), ventricular remodeling (dilatation [+25 mL] or decreased ejection fraction [-5%EF]). Incomplete ablation was defined as index VT recurrence or ablation in previously unablated regions inside index scar without PROG. RESULTS: Twenty patients from nine centers were included (80% male 55 ± 16 years, 7 ARVC and 13 NICM, LVEF 43 ± 14%). Mean delay was 28 ± 18 months. Disease progression occurred in 75% with ventricular remodeling in 70%: ventricular dilation in 45% (ARVC [71%]; NICM [38%]), decreased EF in 60% [RVEF in ARVC (71%); LVEF in NICM (54%)], and scar progression in 50% (in ARVC [57%] and NICM [46%]). Index VT recurrence was observed in 40%. Redo ablation sites were located in previously unablated regions inside the index scar in 70% of patients. VT recurrence following the second procedure was seen in 25%. Fifteen percent died during a follow-up of 17 ± 17 months. CONCLUSION: Disease progression is the rule in ARVC and NICM while scar progression occurs in half. However, even if disease progression is frequently observed, incomplete index ablation is the most common finding, strongly suggesting the need for more extensive ablation.

Duty-cycled multi-electrode radiofrequency vs. conventional irrigated point-by-point radiofrequency ablation for recurrent atrial fibrillation: comparative 3-year data.

AIMS: Pulmonary vein isolation (PVI) is an accepted treatment to relieve symptoms in patients with atrial fibrillation (AF). We studied 3 year outcome after PVI guided by duty-cycled multi-electrode radiofrequency (RF) ablation (pulmonary vein ablation catheter, PVAC) and provided comparative data to outcome after conventional PVI (CPVI) using mapping with irrigated, point-per-point RF ablation. METHODS AND RESULTS: One hundred and sixty-one consecutive patients with symptomatic paroxysmal or persistent AF and minimal heart disease underwent PVI (PVAC, n = 79 vs. CPVI, n = 82). Follow-up (with symptom-guided rhythm monitoring) was truncated at 3 years in all patients. Success was defined as freedom of documented arrhythmia after a single procedure and without antiarrhythmic drug treatment (ADT). Baseline characteristics did not differ between both groups. At 3 years follow-up, single-procedure success without ADT was comparable between PVAC and CPVI (65% vs. 55%, P = NS). The majority of recurrences occurred during the first year (PVAC 79% vs. CPVI 70%, P = NS). The annual rate of very late recurrence (i.e. beyond 1 year) was similar in both groups (10.5% vs. 15%, P = NS). CONCLUSION: At 3 years follow-up, outcome after PVAC-guided PVI is comparable to conventional isolation by irrigated point-by-point RF ablation. In both strategies, the majority of recurrences occurred in the first year of ablation.

Associations of childhood maltreatment with binge eating and binge drinking in emerging adult women.

Background: Binge drinking and binge eating are prevalent, frequently co-occurring, high-risk behaviors among emerging adult women, each with physical and psychological consequences. The mechanisms driving their co-occurrence are not well understood, though a history of adverse childhood experiences (ACEs) may increase the risk for both binge behaviors. Objective: To assess the association between ACE subtypes and individual and co-occurring binge drinking and eating in emerging adult women. Participants and Setting: A diverse sample of women participating in the population-based study EAT 2018: Eating and Activity over Time (N = 788; aged 18-30; 19% Asian, 22% Black, 19% Latino, and 36% White). Methods: Multinomial logistic regression estimated associations among ACE subtypes (i.e., sexual abuse, physical abuse, emotional abuse, household dysfunction), and binge drinking, binge eating, and their co-occurrence. Results are reported as predicted probabilities (PP) of each outcome. Results: Over half of the sample (62%) reported at least one ACE. In models mutually adjusted for other ACEs, physical and emotional abuse showed the strongest associations with binge behaviors. Experiences of physical abuse had the strongest association with a ten-percentage point higher predicted probability of binge drinking (PP = 37%, 95% [CI 27-47%]) and seven-percentage point higher PP of co-occurring binge eating and drinking (PP = 12%, 95% CI [5-19%]). Emotional abuse had the strongest association with an 11-percentage point higher PP binge eating only (PP = 20%, 95% CI [11-29%]). Conclusions: This study found childhood physical and emotional abuse to be particularly relevant risk factors for binge drinking, binge eating, and their co-occurrence among emerging adult women.

Sequelae after AF ablation: Efficacy and Safety go Hand in Hand.

Although nowadays performed on a routine basis, catheter ablation of atrial fibrillation is associated with the potential for major complications. Improving the safety remains therefore an important challenge. This article summarizes the different types of complications associated with AF ablation grouping them into clinically overt major complications, subclinical injury and permanent injury. Furthermore, it describes the potential predictors for complications and highlights the dynamic interplay between efficacy and safety.

Atrial and ventricular electrical and contractile remodeling and reverse remodeling owing to short-term pacing-induced atrial fibrillation in horses.

BACKGROUND: In humans, atrial fibrillation (AF) induces electrical, contractile, and structural remodeling leading to AF stabilization. Little is known about AF-induced atrial remodeling in horses. HYPOTHESIS: Induced AF produces rapid atrial electrical and contractile remodeling in horses. ANIMALS: Six horses, 5 animals completed the study. METHODS: Each horse was instrumented with a pulse generator and pacemaker to maintain AF by burst pacing and to study atrial and ventricular electrophysiology (AF cycle length [AFCL], AF duration, and atrial/ventricular effective refractory period [AERP/VERP] at different pacing cycle lengths [PCL]). Left atrial and ventricular contractile remodeling were assessed echocardiographically by calculation of fractional changes in atrial and ventricular dimensions, respectively, during the cardiac cycle. Measurements were performed at baseline, a 7-day AF period and a 2-day recovery period. RESULTS: Atrial electrical and contractile remodeling could be demonstrated after 4 and 12 hours of AF, respectively. A progressive shortening of the AERP (261 +/- 39-171 +/- 18 ms at a PCL of 1,000 ms, P < .0001), an attenuation of the AERP rate adaptation, a decrease in AFCL (239 +/- 39-194 +/- 7 ms, P < .0001), and a decrease in atrial FS (12 +/- 3% to 0 +/- 2%, P < .05) occurred. AF duration increased progressively and became persistent in 2 animals. VERP did not change significantly. Upon restoration of sinus rhythm, values returned to baseline within 48 hours. CONCLUSIONS AND CLINICAL IMPORTANCE: Atrial electrical and contractile remodeling appears rapidly. After 7 days of AF, reverse remodeling occurred within 2 days. These observations suggest that early conversion of AF might be beneficial for success rate and early return to training.

Efficacy of advanced pace-mapping technology for idiopathic premature ventricular complexes ablation.

PURPOSE: Catheter ablation is an effective treatment for premature ventricular complexes (PVCs). Activation mapping is accurate but requires PVCs at the time of the ablation. Pace-mapping correlation (PMC) is a supplemental tool recently developed as an integrated module for an electro-anatomical mapping platform. Our study sought to investigate whether pace-mapping technology provides similar ablation results in patients with low versus high idiopathic PVC burden at the time of ablation and the relationship between sites with the highest PMC and the earliest local activation time (LAT). METHODS: A total of 59 consecutive patients undergoing catheter ablation for idiopathic PVCs were enrolled. Twelve out of 59 patients (20%) were classified in the low PVC burden group (defined as < 2 PVCs/min) and 47/59 (80%) in the high PVC burden group. RESULTS: The most common origin of PVCs was the right ventricular outflow tract (RVOT) followed by aortic cusps, coronary sinus, parahisian region, and aorto-mitral continuity. Procedural and 1-month success rate were 95 and 87% respectively. PVC burden at the time of ablation did not influence the success rate. The median distance between the earliest LAT points and the highest PMC points was 6.4 (4.9-10.6) mm. CONCLUSIONS: Pace-mapping correlation is useful and accurate in localizing the origin of idiopathic PVCs irrespective of the initial PVC burden. It provides optimal ablation results when combined with LAT. Success rate at mid-term follow-up is higher when the origin of PVCs is located in the RVOT as compared to other locations.

Effects of an adapted intravenous amiodarone treatment protocol in horses with atrial fibrillation.

REASON FOR PERFORMING STUDY: Good results have been obtained with a human amiodarone (AD) i.v. protocol in horses with chronic atrial fibrillation (AF) and a pharmacokinetic study is required for a specific i.v. amiodarone treatment protocol for horses. OBJECTIVES: To study the efficacy of this pharmacokinetic based i.v. AD protocol in horses with chronic AF. METHODS: Six horses with chronic AF were treated with an adapted AD infusion protocol. The protocol consisted of 2 phases with a loading dose followed by a maintenance infusion. In the first phase, horses received an infusion of 6.52 mg AD/kg bwt/h for 1 h followed by 1.1 mg/kg bwt/h for 47 h. In the second phase, horses received a second loading dose of 3.74 mg AD/kg bwt/h for 1 h followed by 1.31 mg/kg bwt/h for 47 h. Clinical signs were monitored, a surface ECG and an intra-atrial electrogram were recorded. AD treatment was discontinued when conversion or any side effects were observed. RESULTS: Three of the 6 horses cardioverted successfully without side effects. The other 3 horses did not convert and showed adverse effects, including diarrhoea. In the latter, there were no important circulatory problems, but the diarrhoea continued for 10-14 days. The third horse had to be subjected to euthanasia because a concomitant Salmonella infection worsened the clinical signs. CONCLUSION: The applied treatment protocol based upon pharmacokinetic data achieved clinically relevant concentrations of AD and desethylamiodarone. POTENTIAL RELEVANCE: Intravenous AD has the potential to be an alternative pharmacological treatment for AF in horses, although AD may lead to adverse drug effects, particularly with cumulative dosing.

Coronary risk factors and inflammation in patients with coronary artery disease and internal cardioverter defibrillator implants.

BACKGROUND: The internal cardioverter defibrillator (ICD) is increasingly used to treat ventricular tachyarrhythmias in patients with coronary artery disease (CAD). The burden of coronary risk factors and inflammation is however not well studied in these high risk patients. STUDY AIMS: The aim of the present study was to describe the prevalence of coronary risk factors (including lipid values) and inflammation (including high sensitive-C-reactive protein, hs-CRP) in patients with CAD and ICD implants. METHODS: Baseline clinical characteristics and laboratory results of all eligible patients for the Cholesterol Lowering and Arrhythmias Recurrences after Internal Defibrillator Implantation trial (CLARIDI trial) were used. All patients had documented CAD, an ICD implant and were not yet treated with statins. Coronary risk factors, lipid values, glycated haemoglobin (HbA(1c)) and hs-CRP levels were determined. RESULTS: In the 110 included patients (mean age 68+/-9 years, LVEF 40+/-17%, NYHA class II-III in 47%), a high prevalence of coronary risk factors was documented: current smoking in 18%, body mass index > or =30 kg/m(2) in 16%, blood pressure > or =140/90 mm Hg in 40%, history of diabetes in 12%, and HbA(1c) > or =6% in 16% of patients not known with diabetes. A total cholesterol >175 mg/dl was found in 76% of patients and an LDL cholesterol >100 mg/dl in 83%. Finally, median hs-CRP was 4.8 mg/l (interquartile range 2.5-13.9 mg/l). Hs-CRP values > or =2 mg/l were noted in 83% of all patients and in 68% of patients who had an ICD implant more than 6 months before inclusion. CONCLUSION: In CAD patients with ICD implants, the burden of coronary risk factors is high, often unrecognized and/or under-treated. Persistent inflammation is found in the majority of these patients.

Intravenous amiodarone treatment in horses with chronic atrial fibrillation.

Six horses without underlying cardiac disease were presented because of atrial fibrillation of between 5 and 12 months duration. These horses received an intravenous amiodarone treatment of 5mg/kg/h for 1 h followed by 0.83mg/kg/h for 23h and subsequently 1.9mg/kg/h for 30h. During treatment, clinical signs were monitored and a surface ECG and an intra-atrial electrogram were recorded. Infusion was discontinued when sinus rhythm or side effects occurred. Four horses successfully cardioverted, of which one showed symptoms of hind limb weakness and weight shifting. Two horses did not cardiovert and showed similar side effects. In all horses, side effects disappeared within 6h after termination of treatment. Cardiac side effects, such as pro-arrhythmia, were not seen in any of the horses. Total bilirubin slightly increased in three horses and normalised within four days. It was concluded that amiodarone has the potential to treat naturally occurring chronic atrial fibrillation in horses, although further research is needed to refine the infusion protocol.

Heart rate dynamics at the onset of ventricular tachyarrhythmias as retrieved from implantable cardioverter-defibrillators in patients with coronary artery disease.

BACKGROUND: The recent availability of implantable cardioverter-defibrillators (ICDs) that record 1024 R-R intervals preceding a ventricular tachyarrhythmia (VTA) provides a unique opportunity to analyze heart rate variability (HRV) before the onset of VTA. METHODS AND RESULTS: Fifty-eight post-myocardial infarction patients with an implanted ICD for recurrent VTA provided 2 sets of 98 heart rate recordings in sinus rhythm: (1) before a VTA and (2) during control conditions. Three subgroups were considered according to the antiarrhythmic (AA) drug regimen. A state of sympathoexcitation was suggested by the significant reduction in HRV before VTA onset compared with control conditions. beta-Blockers and dl-sotalol enhanced HRV in control recordings; nevertheless, HRV declined before VTA independent of AA drugs. A gradual increase in heart rate and decrease in sinus arrhythmia at VTA onset were specific findings of patients who received dl-sotalol. CONCLUSIONS: The peculiar heart rate dynamics observed before VTA onset are suggestive of a state of sympathoexcitation that is independent of AA drugs.

Lipid lowering drugs and recurrences of life-threatening ventricular arrhythmias in high-risk patients.

OBJECTIVES: To evaluate a possible effect of lipid lowering drugs on recurrences of ventricular arrhythmias (VA) after implantable cardioverter defibrillator (ICD) implantation. BACKGROUND: In patients with coronary artery disease (CAD), lipid lowering drugs reduce total and sudden cardiac death. Because the mechanism is not completely understood, we studied whether these drugs have a favorable influence on the occurrence of life-threatening VA in patients with CAD and ICD implants. METHODS: We conducted an observational study in 78 patients with CAD and life-threatening VA, treated with an ICD. After ICD implantation, 27 patients were on treatment with lipid lowering drugs (group I) and 51 were not (group II). Patients were studied for the following end points: recurrences of VA requiring ICD intervention, cardiac death and hospitalization. RESULTS: After a mean follow-up of 490 +/- 319 days, 35 patients (45%) had recurrences of VA requiring ICD intervention. In multivariate analysis, the use of lipid lowering drugs (chi-square 6.33, p = 0.012) and poorly tolerated sustained monomorphic ventricular tachycardia as initial presentation (chi-square 4.84, p = 0.028) remained as independent predictors of recurrences of VA. Patients in groups I and II had similar baseline clinical characteristics, but patients in group I had a lower incidence of recurrences of VA (6/27 or 22% vs. 29/51 or 57%, p = 0.004) and of the combined end points of cardiac death and hospitalization (4/27 or 15% vs. 23/51 or 45%, p = 0.015) compared with patients in group II. CONCLUSIONS: This is the first observation that the use of lipid lowering drugs is associated with a reduction of recurrences of VA in patients with CAD and ICD implants. These data require confirmation in a prospective randomized trial.

Circadian rhythm of core body temperature in two laboratory mouse lines.

The circadian rhythm of core body temperature (Tb) was examined in two mouse lines bidirectionally selected for nest-building behavior (small (SNB) and big nest-builders (BNB)). This selection also resulted in more robust circadian organization of wheel-running activity in the SNB compared to the BNB mice. Tb was measured by an e-mitter implanted in the abdominal cavity. The circadian Tb rhythm of the SNB was more robust compared to the BNB regardless of whether the animals had access to a running wheel or not and regardless of the lighting conditions, i.e., 12 h:12 h light:dark (LD) cycle or constant dark (DD). Wheel-running activity rhythms of SNB were more robust in LD and DD compared to BNB. The amplitude of the circadian Tb rhythm increased significantly in response to wheel access in both mouse lines, but was not significantly different between the BNB and SNB. However, BNB tended to have lower amplitudes of circadian Tb rhythm in the absence of running wheels and a larger increase in the amplitude upon access to a running wheel compared to SNB. No differences were found in LD and DD between the lines in mean Tb and wheel-running activity levels. In addition, no differences between the two mouse lines were found in the free-running period of the Tb or wheel-running activity rhythms in DD. Overall, our findings reveal a more robust circadian phenotype of the SNB compared to the BNB.

Transient complete atrioventricular block following transvenous electrical cardioversion of atrial fibrillation in a horse.

Transvenous electrical cardioversion was attempted in a horse with drug refractory atrial fibrillation. A temporary pacing catheter and two defibrillation catheters were inserted transvenously into the right ventricular apex, the right atrium and the pulmonary artery, respectively. Under general anaesthesia 100, 200, 300 and 360 J monophasic shocks were delivered between both defibrillation catheters but sinus rhythm could not be restored. Immediately after the 200, 300 and 360 J shock, transient third-degree atrioventricular block occurred for a period of, respectively, 15, 40 and 55 s. These periods of profound bradycardia were corrected by temporary right ventricular pacing until spontaneous conduction resumed. It is concluded that temporary right ventricular pacing should be available during electrical cardioversion of atrial fibrillation in horses.

Variations of autonomic tone preceding onset of atrial fibrillation after coronary artery bypass grafting.

Assessment of autonomic tone preceding the onset of atrial fibrillation (AF) after coronary artery bypass grafting (CABG) with heart rate variability was examined in 64 patients scheduled for elective CABG (days 2 to 5). Ninety-six-hour Holter tapes were analyzed in each patient and all events labeled by an experienced technician. The hour preceding AF was divided into 4 quarters (heart rate variability calculated per quarter) and compared with similar time episodes from the group without AF. Twenty-six of 64 patients (40%) had a total of 35 episodes. Only increased age (68+/-5 vs 62+/-9 years) and lower ejection fraction (66+/-16% vs 73+/-8%) were associated with an increased risk for AF. Before onset, a greater number of atrial premature complexes was observed. The standard deviation of all RR intervals (SDNN) showed an increase in the group with AF in the last 15 minutes (significant vs controls and within the AF group). The low-frequency/high-frequency ratio was significantly lower in patients in the first 30 minutes, followed by an increase mainly because the high-frequency spectrum became less important. Thus, initiation of postoperative AF is influenced by autonomic tone variations. A shift in the autonomic balance with a loss of vagal tone and a moderate increase in sympathetic tone are observed before the onset of AF compared with those in controls.

Electrocardiographic and morphometric features in patients with ventricular tachycardia of right ventricular origin.

OBJECTIVE: To study differences between repetitive monomorphic ventricular tachycardia (RMVT) of right ventricular origin, and ventricular tachycardia in arrhythmogenic right ventricular dysplasia (ARVD). PATIENTS: Consecutive groups with RMVT (n = 15) or ARVD (n = 12), comparable for age and function. METHODS: Analysis of baseline, tachycardia, and signal averaged ECGs, clinical data, and right endomyocardial biopsies. Pathological findings were related to regional depolarisation (QRS width) and repolarisation (QT interval, QT dispersion). RESULTS: There was no difference in age, ejection fraction, QRS width in leads I, V1, and V6, and QT indices. During ventricular tachycardia, more patients with ARVD had a QS wave in V1 (p < 0.05). There were significant differences for unfiltered QRS, filtered QRS, low amplitude signal duration, and the root mean square voltage content. In the absence of bundle branch block, differences became non-significant for unfiltered and filtered QRS duration. Mean (SD) percentage of biopsy surface differed between RMVT and ARVD: normal myocytes (74(3.4)% v 64.5(9.3)%; p < 0.05); fibrosis (3(1.7)% v 8.9(5.2)%; p < 0.05). When all patients were included, there were significant correlations between fibrosis and age (r = 0.6761), and fibrosis and QRS width (r = 0.5524 for lead I; r = 0.5254 for lead V1; and r = 0.6017 for lead V6). CONCLUSIONS: The ECG during tachycardia and signal averaging are helpful in discriminating between ARVD and RMVT patients. There are differences in the proportions of normal myocytes and fibrosis. The QRS duration is correlated with the amount of fibrous tissue in patients with ventricular tachycardia of right ventricular origin.

QT dispersion is not related to infarct size or inducibility in patients with coronary artery disease and life threatening ventricular arrhythmias.

OBJECTIVE: To relate QT parameters to infarct size and inducibility during electrophysiological studies. DESIGN: Analysis of a prospective register. SETTING: University hospital. PATIENTS: 64 patients with coronary artery disease and documented life threatening ventricular arrhythmias. INTERVENTIONS: Measurements of QT-max, QTc-max, and QT dispersion (QT-d) on a simultaneous 12 lead ECG (50 mm/s). Estimation of myocardial infarct size with radionuclide left ventricular ejection fraction (LVEF), echocardiography (left ventricular end diastolic diameter, LVEDD), and a defect score based on a quantitative stress redistribution 201-thallium perfusion study. Electrophysiological study to assess inducibility. RESULTS: Mean (SD) QT parameters were: QT-max 440 (50) ms, QTc-max 475 (46) ms, and QT-d 47 (20) ms. Mean (SD) estimates of infarct size were: LVEF 34 (13)%, LVEDD 61 (9) mm, and defect score 18 (11). There was no significant correlation between any index of infarct size and QT parameters. QT parameters were not significantly different between patients with inducible (n = 57) and non-inducible arrhythmias (n = 7) (QT-max: 416 (30) v 443 (51) ms, p = 0.18; QTc-max 485 (34) v 473 (47) ms, p = 0.34; QT-d 47 (12) v 47 (21) ms, p = 0.73). Non-inducible patients had a significant lower defect score: 8 (9) v 19 (11), p = 0.02, but comparable LVEF: 38 (12)% v 34 (12)%, p = 0.58, and LVEDD: 54 (10) v 61 (8) mm, p = 0.13. CONCLUSIONS: QT parameters are not influenced by infarct size and do not predict inducibility during electrophysiological study in patients with coronary artery disease and malignant ventricular arrhythmias. In contrast, the amount of scar tissue determined by perfusion imaging is strongly correlated with inducibility.

An equine model of chronic atrial fibrillation: methodology.

We describe the development and the different features of an experimental model of chronic atrial fibrillation (AF) in equines. In four healthy ponies a dual-chamber pacemaker, with an adapted pacemaker program, was implanted transvenously in the standing animal. This adapted pacemaker induced episodes of AF by delivering a 2s burst of electrical stimuli (42 Hz) as soon as sinus rhythm was detected. Simultaneous with a surface electrocardiogram, the intra-atrial electrogram could be recorded to determine the atrial electrogram morphology. Programmed electrical stimulation (PES) was used to determine the atrial effective refractory period (AERP) and the rate adaptation of the AERP, the sinus node recovery time (SNRT) and the corrected SNRT, AF vulnerability, AF cycle length and AF duration. This experimental AF model can be used to study the pathophysiology of chronic AF in equines.

Dual-chamber pacemaker implantation via the cephalic vein in healthy equids.

The purpose of the present study was to develop a feasible and safe technique for dual-chamber pacemaker implantation in healthy horses. Implantation was performed in a standing, tranquilized horse and in ponies. Atrial and ventricular leads were transvenously inserted through the cephalic vein, and a subcutaneous pacemaker pocket was created between the lateral pectoral groove and the manubrium sterni in 6 equids. Positioning of each lead was guided by echocardiography and by measuring the electrical characteristics of the lead. The implantation procedure lasted about 4 hours in each animal and was well tolerated. In all animals, dual-chamber pacemaker function was obtained, and these results remained good throughout the follow-up period. At the time of implantation, atrial and ventricular sensing were between 2.1 and 7.2 mV and 7.8 and 16.8 mV, respectively, and atrial and ventricular pacing thresholds at 0.5 millisecond varied from 0.5 to 0.7 V and from 0.3 to 1.0 V, respectively. Six months after the implantation, sensing values varied from 2 to 10 mV for the atrial lead and from 2 to 16 mV for the ventricular lead, while pacing thresholds at 0.5 millisecond varied from less than 0.5 to 2.5 V for the right atrium and from less than 0.5 to 5.0 V for the right ventricle. Atrial lead dislodgment occurred in 2 animals, requiring insertion of a new lead. Ventricular lead dislodgment was not observed.

The actual therapy and in-hospital mortality of acute myocardial infarction in Flanders. Mirracle's Investigators.

We studied influences on treatment and mortality in 787 patients with myocardial infarction in the setting of a prospective registry. Fifty % of patients received thrombolytics, 81% aspirin, and 46% beta-blockers. Decisions to give thrombolytics were influenced by gender and function. During hospital stay angioplasty was performed in 21%, and grafting in 11%. In hospital-mortality (11%) was related to age and function. In multivariate analysis, only age influenced the use of angioplasty and revascularization. In conclusion, in-hospital mortality remains high, while 50% of patients receive thrombolytic therapy. Some therapeutic options are highly influenced by age, gender, and cardiac function.