Arterial hypertension drives arrhythmia progression via specific structural remodeling in a porcine model of atrial fibrillation

Pathophysiology and clinical relevance of atrial myopathy

Atrial myopathy is a condition that consists of electrical, structural, contractile, and autonomic remodeling of the atria and is the substrate for development of atrial fibrillation, the most common arrhythmia. Pathophysiologic mechanisms driving atrial myopathy are inflammation, oxidative stress, atrial stretch, and neurohormonal signals, e.g., angiotensin-II and aldosterone. These mechanisms initiate the structural and functional remodeling of the atrial myocardium. Novel therapeutic strategies are being developed that target the pathophysiologic mechanisms of atrial myopathy. In this review, we will discuss the pathophysiology of atrial myopathy, as well as diagnostic and therapeutic strategies.

Reduction in atrial and pulmonary vein stretch as a therapeutic target for prevention of atrial fibrillation

Atrial fibrillation (AF) is a common cardiac arrhythmia that is associated with increased mortality. Heart failure, hypertension, valvular disease, and obstructive sleep apnea are risk factors for incident AF. A common characteristic of these diseases is that they increase atrial wall stretch. Multiple experimental studies confirm a proarrhythmic effect of atrial stretch. Conversely, a reduction in stretch is antiarrhythmic. A therapeutic target for AF, therefore, lies in local reduction of atrial stretch. This review focuses on atrial stretch and its clinical associations in patients with AF and its downstream effects on electrophysiology. We discuss the possible application of targeted atrial stretch reduction in AF prevention. We conclude that a reduction in local atrial stretch should be considered an essential element in rhythm control.

3D-electroanatomical mapping of the left atrium and catheter-based pulmonary vein isolation in pigs: A practical guide

Aim

To propose a standardized workflow for 3D-electroanatomical mapping guided pulmonary vein isolation in pigs.

Materials and methods

Danish female landrace pigs were anaesthetized. Ultrasound-guided puncture of both femoral veins was performed and arterial access for blood pressure measurement established. Fluoroscopy- and intracardiac ultrasound-guided passage of the patent foramen ovale or transseptal puncture was performed. Then, 3D-electroanatomical mapping of the left atrium was conducted using a high-density mapping catheter. After mapping all pulmonary veins, an irrigated radiofrequency ablation catheter was used to perform ostial ablation to achieve electrical pulmonary vein isolation. Entrance- and exit-block were confirmed and re-assessed after a 20-min waiting period. Lastly, animals were sacrificed to perform left atrial anatomical gross examination.

Results

We present data from 11 consecutive pigs undergoing pulmonary vein isolation. Passage of the fossa ovalis or transseptal puncture was uneventful and successful in all animals. Within the inferior pulmonary trunk 2-4 individual veins as well as 1-2 additional left and right pulmonary veins could be cannulated. Electrical isolation by point-by-point ablation of all targeted veins was successful. However, pitfalls including phrenic nerve capture during ablation, ventricular arrhythmias during antral isolation close to the mitral valve annulus and difficulties in accessing right pulmonary veins were encountered.

Conclusion

Fluoroscopy- and intracardiac ultrasound-guided transseptal puncture, high-density electroanatomical mapping of all pulmonary veins and complete electrical pulmonary vein isolation can be achieved reproducibly and safely in pigs when using current technologies and a step-by-step approach.

The impact of a modified anaesthetic protocol on animal survival and the characteristics of ventricular arrhythmias in the course of acute myocardial infarction in a domestic pig model

Introduction

Acute myocardial infarction (MI) is one of the most common causes of death in humans in highly developed countries. Among its most frequent complications affecting the patient’s prognosis are cardiac arrhythmias: ventricular tachycardia (VT) and ventricular fibrillation (VF).

Material and Methods

The study aimed to characterise arrhythmias in 19 pigs subjected to experimentally induced MI obtained by occlusion of the proximal left anterior descending (LAD) coronary artery using an angioplasty balloon. The anaesthetic protocol was modified to reduce mortality by including procedures stabilising haemodynamic disorders which develop during episodes of ischaemia and arrhythmia. During 30 min of experimentally induced ischaemia, the heart rhythm was recorded using a 12-lead ECG. The time, frequency, and type of arrhythmias were analysed.

Results

Ventricular arrhythmias were found in 94.74% of the treated pigs. The most common were ventricular premature complexes, reported in 88.89% of pigs with arrhythmia. Ventricular tachycardia was recorded in 66.67% and ventricular fibrillation in 50% of pigs with arrhythmias.

Conclusion

Myocardial infarction due to proximal LAD occlusion is characterised by a high incidence of ventricular arrhythmias, especially VT and VF. Because of the high survival rate, this MI porcine model may serve as a model for research on acute ischaemic ventricular arrhythmias in humans. Additionally, it reduces the total number of animals required for testing while yielding meaningful results, which is in line with the 3R principle.

Metoprolol Improves Myocardial Remodeling and Cardiac Function in Patients with Permanent Pacemaker Implantation

In China, the incidence of arrhythmia has also increased to approximately 20% of all cardiovascular diseases. The incidence of cardiovascular diseases in China has certain characteristics, which are generally low in the south and high in the north, and they tend to be younger and growing. Permanent pacemaker implantation is currently the most effective means of treating arrhythmia and preventing sudden death. To explore the clinical application value of metoprolol in patients after permanent pacemaker implantation. Ninety patients with permanent dual-chamber pacemaker implantation in our hospital are selected and divided into a metoprolol group and a control group according to whether metoprolol is used one week after the operation and 45 patients in each group. After one postoperative week, the LVEF%, LVEDd, LAD, and E/A of the metoprolol and the control groups had no statistically significant differences (p > 0.05). Twelve months postoperatively, the E/A of the metoprolol group is higher than that of the control group (p < 0.05), and LVEDd and LAD are lower than those of the control group (P < 0.05). The NT-proBNP and hs-CRP levels between the metoprolol and control groups had no significant differences (p > 0.05) in the values recorded immediately postoperatively. The NT-proBNP of the metoprolol group is lower than that of the control group (p < 0.05) at 12 months following pacemaker implantation. At one week after surgery, QTd, Pd, and Tp-Te are not significantly different (P > 0.05) between the metoprolol group and the control group, whereas the QTd and Pd times in the metoprolol group are lower than those in the control group (p < 0.05) at the 12-month follow-up. At one week postoperatively, the SDNN, SDANN, and RMSSD between the metoprolol and control groups did not show any statistically significant differences (p > 0.05). The SDANN of the metoprolol group is higher than that in the control group (p < 0.05) in the 12-month evaluation. One week after the operation, the serum IL-6 and TNF-α levels are not significantly different between the metoprolol and control groups (p > 0.05). At 12 months after surgery, the serum IL-6 and TNF-α levels in the metoprolol group are lower than those in the control group (p < 0.05). The incidence of adverse events in the metoprolol group is 9.30% lower than 26.83% in the control group within 12 months after the operation (p < 0.05). The use of metoprolol in patients with permanent pacemaker implantation after surgery can reduce the expansionary remodeling of the left atrium and have less impact on the QT-dispersion and Pd time.

Bi‐atrial characterization of the electrical substrate in patients with atrial fibrillation

Background

Methods

Results

Conclusion

Impact of nocturnal hypoxemia on the recurrence of atrial tachyarrhythmia after catheter ablation of atrial fibrillation

Factors causing atrial tachyarrhythmia recurrence after catheter ablation (CA) of atrial fibrillation (AF) remain undetermined. This study aimed to investigate the effect of nocturnal hypoxemia on the recurrence of atrial tachyarrhythmia after CA of AF. Among 594 patients with AF who underwent an ambulatory sleep study at the National Cerebral and Cardiovascular Center, Suita, Osaka, Japan (2014-2019), 365 underwent CA of AF; 290 patients who underwent CA were followed up for > 3 months. Multivariate Cox regression analysis was used to calculate hazard ratios (HRs) using clinical variables, to identify the independent predictors of atrial tachyarrhythmia recurrence after the final CA. Atrial tachyarrhythmia recurred in 45 of 290 (15.5%) patients during the median follow-up period of 479 days (interquartile range 225-1002). On the performing multivariate analysis of the data of patients who did not receive continuous positive airway pressure (CPAP), severe nocturnal hypoxemia [defined as the percentage of sleep time spent with SaO₂ of < 90% (T90) over 20%] [HR 8.53, 95% confidence interval (CI) 1.872-38.814; P < 0.01] and an 1 mL/m² increase in the left atrial volume index (HR 1.02, 95% CI 1.004-1.044; P = 0.02) were found to be independently associated with the recurrence of atrial tachyarrhythmia. In addition, the rates of freedom from atrial tachyarrhythmia after the final AF ablation with CPAP were significantly lower in the group with more severe nocturnal hypoxemia (Log-rank P = 0.03). In conclusion, it is necessary to consider both, AHI and nocturnal hypoxia while performing an ambulatory sleep apnea study. CA may be less effective in patients with more severe nocturnal hypoxia, despite the administration of CPAP.

ESC working group on cardiac cellular electrophysiology position paper: relevance, opportunities, and limitations of experimental models for cardiac electrophysiology research

Cardiac arrhythmias are a major cause of death and disability. A large number of experimental cell and animal models have been developed to study arrhythmogenic diseases. These models have provided important insights into the underlying arrhythmia mechanisms and translational options for their therapeutic management. This position paper from the ESC Working Group on Cardiac Cellular Electrophysiology provides an overview of (i) currently available in vitro, ex vivo, and in vivo electrophysiological research methodologies, (ii) the most commonly used experimental (cellular and animal) models for cardiac arrhythmias including relevant species differences, (iii) the use of human cardiac tissue, induced pluripotent stem cell (hiPSC)-derived and in silico models to study cardiac arrhythmias, and (iv) the availability, relevance, limitations, and opportunities of these cellular and animal models to recapitulate specific acquired and inherited arrhythmogenic diseases, including atrial fibrillation, heart failure, cardiomyopathy, myocarditis, sinus node, and conduction disorders and channelopathies. By promoting a better understanding of these models and their limitations, this position paper aims to improve the quality of basic research in cardiac electrophysiology, with the ultimate goal to facilitate the clinical translation and application of basic electrophysiological research findings on arrhythmia mechanisms and therapies.

Different impact factors for accurate oscillometric blood pressure measurement between sinus rhythm and atrial fibrillation

This study was conducted to evaluate whether the impact factor on the accuracy of oscillometric blood pressure (BP) is different between the patients with atrial affiliation (AF) and sinus rhythm (SR). This study included 124 AF patients and 98 SR patients who underwent coronary arteriography. Upper arm oscillometric and intro-aortic BP were simultaneously measured three times, and the averages were recorded as final values, respectively. The difference between oscillometric and intro-aortic BP was recorded as delta BP. For reducing the influence of baseline BP on delta BP, a percentage difference (PD-BP) was calculated with the formula: PD-BP = delta BP/intro-aortic BP × 100%. The oscillometric SBP and DBP levels slightly underestimated intro-aortic BP (by 2.2/1.6 mmHg) in the SR group, but significantly underestimated (by 5.8/4.8 mmHg) in the AF group. Age was negatively correlated with delta SBP and positively with delta DBP in SR patients, but not correlated in AF patients. Otherwise, ventricular rate (VR) was negatively correlated with delta SBP or delta DBP in AF, which indicated that the accuracy of oscillometric BP declined as the VR increased. With intro-aortic BP as reference, the accuracy of oscillometric BP in AF patients is lower than SR patients. Meanwhile, age may impact the oscillometric BP accuracy in SR patients, but VR may impact that in AF patients.

Hypertension, Prehypertension, Hypertensive Heart Disease, and Atrial Fibrillation

Hypertension (HT) confers the highest population-attributable risk among factors leading to atrial fibrillation (AF). Data also are accumulating regarding the association between pre-HT, aortic stiffness, and increased incident AF or AF recurrence. Atrial remodeling due to HT is progressive but also reversible. Although inhibition of the renin-angiotensin-aldosterone system has shown the greatest promise in improving AF outcomes, optimal blood pressure targets in individuals with HT and AF remain elusive. AF management demands an integrated care approach. HT is best treated alongside a comprehensive risk factor management program where other AF risk factors are targeted, with involvement of a multidisciplinary team.

Quantification of Left Atrial Fibrosis in Patients After Pulmonary Vein Isolation Using the Second-Generation Cryoballoon

Left atrial (LA) fibrosis is associated with a poor outcome after atrial fibrillation (AF) ablation. This study examined the extent of low-voltage areas in patients with recurrence of atrial tachyarrhythmia (ATA) after CB-based pulmonary vein isolation (PVI).Sixty patients (mean age 67 ± 10 years, n = 32 female; n = 34 paroxysmal AF) who received radiofrequency redo-procedure due to recurrence of ATA within 6 months after CB-based PVI were included. A point-by point 3D-map was performed, and low-voltage sites were delineated based on bipolar voltage < 0.5 mV. The extent of fibrosis was categorized as stage A (0-10% of the LA wall), stage B (10-30%), stage C (30-50%), and stage D (> 50%).The median area of LA low-voltage sites was 28.9 (9; 50.3) cm², corresponding to 17.4 (6; 30.6) % of the LA wall surface. 17/60 (28.3%) patients were categorized as fibrosis stage A, 21/60 (35%) as stage B, 18/60 (30%) as stage C, and 4/60 (6.7%) as stage D. Patient age and LA diameter were associated with more pronounced LA fibrosis; the extent of LA fibrosis was significantly higher in patients with LA tachycardia (LAT) during redo-procedures (P < 0.01), and ablation of linear lesions was more often performed (P < 0.01).In patients after CB2-based PVI, expanded LA tissue fibrosis was associated with the occurrence of LAT and more extensive LA ablation during redo-procedures.

Linear periodization of strength training in blocks attenuates hypertension and diastolic dysfunction with normalization of myocardial collagen content in spontaneously hypertensive rats

BACKGROUND AND METHOD

This study evaluated the effects of a linear block strength training programme on the parameters of cardiac remodelling in spontaneously hypertensive rats. Thirty-nine rats were equally distributed in four groups: normotensive sedentary, normotensive trained, hypertensive sedentary and hypertensive trained. The strength training protocol was organized in three mesocycles of 4 weeks, with an increase in the training load organized in a linear fashion for each block, considering the weight established in the maximum loaded load test. The following parameters were evaluated: ventricular function assessed by echocardiogram, caudal blood pressure, ventricular haemodynamics and cardiac masses. Two-way analysis of variance was used to determine the differences between the group and time.

RESULTS

After 12 weeks of training, the hypertensive trained group presented the following results: increased muscle strength, reduced blood pressure, reduced heart rate, isovolumetric relaxation time and total collagen content, with increased cardiac function, without promoting changes in the mass and nuclear volume of cardiomyocytes. Also, blood pressure reduction seems to be associated with both muscle strength adjustments and total load progress.

CONCLUSION

The findings of this study showed that the training programme carried out attenuated systemic arterial pressure and preserved the ventricular function of spontaneously hypertensive rats without cardiac mass change.

Cellular contribution to left and right atrial dysfunction in chronic arterial hypertension in pigs

Aims

Atrial contractile dysfunction contributes to worse prognosis in hypertensive heart disease (HHD), but the role of cardiomyocyte dysfunction in atrial remodelling in HHD is not well understood. We investigated and compared cellular mechanisms of left (LA) and right atrial (RA) contractile dysfunction in pigs with HHD.

Methods and results

In vivo electrophysiological and magnetic resonance imaging studies were performed in control and pigs treated with 11‐deoxycorticosterone acetate (DOCA)/high‐salt/glucose diet (12 weeks) to induce HHD. HHD leads to significant atrial remodelling and loss of contractile function in LA and a similar trend in RA (magnetic resonance imaging). Atrial remodelling was associated with a higher inducibility of atrial fibrillation but unrelated to changes in atrial refractory period or fibrosis (histology). Reduced atrial function in DOCA pigs was related to reduced contraction amplitude of isolated LA (already at baseline) and RA myocytes (at higher frequencies) due to reduced intracellular Ca release (Fura 2‐AM, field stimulation). However, Ca regulation differed in LA and RA cardiomyocytes: LA cardiomyocytes showed reduced sarcoplasmic reticulum (SR) [Ca], whereas in RA, SR [Ca] was unchanged and SR Ca²⁺‐ATPase activity was increased. Sodium–calcium exchanger (NCX) activity was not significantly altered. We used ORM‐10103 (3 μM), a specific NCX inhibitor to improve Ca availability in LA and RA cardiomyocytes from DOCA pigs. Partial inhibition of NCX increased Ca²⁺ transient amplitude and SR Ca in LA, but not RA cells.

Conclusions

In this large animal model of HHD, atrial remodelling in sinus rhythm in vivo was related to differential LA and RA cardiomyocyte dysfunction and Ca signalling. Selective acute inhibition of NCX improved Ca release in diseased LA cardiomyocytes, suggesting a potential therapeutic approach to improve atrial inotropy in HHD.

Phases of decompensation during acute ischemia demonstrated in an ex vivo porcine bladder model

Background

The aim of this project was to develop an ex-vivo porcine bladder model to test the effects of increasing durations of acute ischemia on detrusor function.

Methods

Porcine bladders were perfused through bilateral vesical arteries at physiologic flow (4 mL/min) and filled through a urethral catheter. Intravesical pressures were continuously recorded using standard urodynamics equipment. Bladder contractions, with simulated voiding, were induced by arterial infusion of KCl at 250 mL. Total, passive, and active pressures were recorded for each contraction and data were normalized to the control fill. Bladders underwent the following perfusion protocol by adjusting the arterial flow rates: Equilibration (4 mL/min), control (4 mL/min), partial ischemia (2 mL/min), global ischemia (0 mL/min) and reperfusion (4 mL/min). Perfusion periods were held for 15 min for one group and 30 min for another group of bladders.

Results

Porcine bladders (N=19) including 8 (15 min group) and 11 (30 min group) were used. With 15 min ischemia, passive pressure increased 39% (P=0.03) and the active pressure decreased 23% (P=0.002). Total pressure remained constant, identifying a compensated phase. Values returned to baseline with reperfusion. With 30 min ischemia, passive pressure remained unchanged. However, there was a decrease in total pressure 34% (P<0.001) and active pressure 61% (P<0.001), which incompletely recovered to baseline values, identifying a decompensated phase with incomplete recovery upon reperfusion.

Conclusion

In the porcine bladder, 15 min ischemia resulted in a compensated phase and 30 min ischemia resulted in a decompensated phase of detrusor function. This study provides mechanistic insight into the natural history of ischemia-mediated voiding dysfunction.

Software-based analysis of 1-hour Holter ECG to select for prolonged ECG monitoring after stroke

Objective

Identification of ischemic stroke patients at high risk for paroxysmal atrial fibrillation (pAF) during 72 hours Holter ECG might be useful to individualize the allocation of prolonged ECG monitoring times, currently not routinely applied in clinical practice.

Methods

In a prospective multicenter study, the first analysable hour of raw ECG data from prolonged 72 hours Holter ECG monitoring in 1031 patients with acute ischemic stroke/TIA presenting in sinus rhythm was classified by an automated software (AA) into “no risk of AF” or “risk of AF” and compared to clinical variables to predict AF during 72 hours Holter‐ECG.

Results

pAF was diagnosed in 54 patients (5.2%; mean age: 78 years; female 56%) and was more frequently detected after 72 hours in patients classified by AA as “risk of AF” (n = 21, 17.8%) compared to “no risk of AF” (n = 33, 3.6%). AA‐based risk stratification as “risk of AF” remained in the prediction model for pAF detection during 72 hours Holter ECG (OR3.814, 95% CI 2.024‐7.816, P < 0.001), in addition to age (OR1.052, 95% CI 1.021‐1.084, P = 0.001), NIHSS (OR 1.087, 95% CI 1.023‐1.154, P = 0.007) and prior treatment with thrombolysis (OR2.639, 95% CI 1.313‐5.306, P = 0.006). Similarly, risk stratification by AA significantly increased the area under the receiver operating characteristic curve (AUC) for prediction of pAF detection compared to a purely clinical risk score (AS5F alone: AUC 0.751; 95% CI 0.724‐0.778; AUC for the combination: 0.789, 95% CI 0.763‐0.814; difference between the AUC P = 0.022).

Interpretation

Automated software‐based ECG risk stratification selects patients with high risk of AF during 72 hours Holter ECG and adds predictive value to common clinical risk factors for AF prediction.

Acute hyperglycaemia is not associated with the development of atrial fibrillation in healthy pigs

Development and progression of atrial fibrillation (AF) is driven by comorbidities such as arterial hypertension and diabetes mellitus. In animal models of chronic hyperglycaemia, progression of AF has been proposed to be triggered by oxidative stress, apoptosis and fibrosis. Acute glycosylation of CaMKII has been associated with increased susceptibility to arrhythmias in acute hyperglycaemia. However, the proarrhythmogenic effect of acute hyperglycaemia has not been investigated. Nine healthy, anesthetized pigs (54 ± 6 kg) were instrumented with electrophysiologic catheters and a multielectrode array on the epicardium of the left atrial anterior wall. Left and right atrial effective refractory periods (AERP), inducibility of AF and left atrial epicardial conduction velocities (CV) were measured at baseline (BL), increasing steps of blood glucose (200-500 mg/dL in steps of 100 mg/dL by glucose infusion) and repeated after normalisation of blood glucose levels (recovery). Serum electrolytes were kept constant during measurements by means of sodium and potassium infusion. There were no significant differences in AERP, CV or AF inducibility between BL and recovery. Heart rate remained constant regardless of blood glucose levels (BL: 103 ± 18 bpm, 500 mg/dL: 103 ± 18 bpm, r = 0.02, p = 0.346). Mean left as well as right AERP increased with higher glucose levels. CV increased with glucose levels (1.25 (1.04, 1.67) m/s at BL vs. 1.53 (1.22, 2.15) m/s at 500 mg/dL, r = 0.85, p = 0.034). Rate of AF inducibility in the left atrium remained constant throughout the whole protocol (AF episodes > 10 s: mean inducibility of 80% at BL vs. 69% at 500 mg/dL, p = 0.32, episodes > 30 s: 0% at BL vs. 0% at 500 mg/dL, p = 0.17). Our data imply that acute hyperglycaemia is associated with lower arrhythmogenic substrate and does not promote AF inducibility.

[Electrophysiological Cardiac Parameters and Results of Antiarrhythmic Treatment in Patients with Paroxysmal Atrial Fibrillation (Lone and Associated with Arterial Hypertension)]

PURPOSE

to assess cardiac electrophysiological parameters in patients with paroxysmal atrial fibrillation (AF), lone or with concomitant arterial hypertension (AH), and their prognostic significance relative to treatment effectiveness.

MATERIALS AND METHODS

We included in this study 184 patients with paroxysmal AF (84 with concomitant AH and 100 with presumed lone AF). Cardiac electrophysiological study was performed in accordance with standardized protocol that included assessment of sinus node recovery time, sinoatrial, intraatrial and interatrial conduction time, and effective refractory periods (ERP) of right and left atria and atrioventricular node. Patients with inducible supraventricular reentrant arrhythmias that could potentially trigger AF underwent catheter radiofrequency ablation of those arrhythmias. Other patients received either antiarrhythmic drug therapy (AAD; n=79) or catheter cryo-ablation (CBA; n=81). Treatment was considered ineffective in case of any symptomatic or asymptomatic AF episode documented by ECG or Holter ECG within 12 months of follow-up.

RESULTS

Patients with lone AF compared with those with AH had shorter ERP of the right atrium (219±21 ms vs. 253±44 ms, respectively, p&lt;0.05) and more prominent dispersion of ERP of right and left atria (median 40 ms, interquartile range 10-50 ms vs. median 20 ms, interquartile range 10-22.5 ms, respectively, p&lt;0.05). There was no statistically significant difference in other electrophysiology parameters between the groups. Sustained supraventricular reentrant arrhythmias were induced in 9% (9 of 100) patients with presumed lone AF and in 1.2% (1 of 84) patients with AH (p&lt;0.05). All these arrhythmias were successfully ablated, and patients had no AF recurrence during 12-month follow-up. Among other patient treatment (CBA n=81, AAD n=79) was effective in 64% of those with lone AFib and in 34% - with AH (p&lt;0.05). In multivariate multiple regression analysis, none of electrophysiological parameters could be assumed as a factor associated with the efficacy of CBA or AAD.

CONCLUSION

Patients with lone AF had more prominent atrial electrophysiological inhomogeneity compared with patients with concomitant AH. Cardiac electrophysiological parameters had no influence on effectiveness of antiarrhythmic treatment.