Cardiac Surgery for Arrhythmias

Integrated Au-Nanoroded Biosensing and Regulating Platform for Photothermal Therapy of Bradyarrhythmia

Bradyarrhythmia is a kind of cardiovascular disease caused by dysregulation of cardiomyocytes, which seriously threatens human life. Currently, treatment strategies of bradyarrhythmia mainly include drug therapy, surgery, or implantable cardioverter defibrillators, but these strategies are limited by drug side effect, surgical trauma, and instability of implanted devices. Here, we developed an integrated Au-nanoroded biosensing and regulating platform to investigate the photothermal therapy of cardiac bradyarrhythmia in vitro. Au-nanoroded electrode array can simultaneously accumulate energy from the photothermal regulation and monitor the electrophsiological state to restore normal rhythm of cardiomyocytes in real time. To treat the cardiomyocytes cultured on Au-nanoroded device by near-infrared (NIR) laser irradiation, cardiomyocytes return to normal for long term after irradiation of suitable NIR energy and maintenance. Compared with the conventional strategies, the photothermal strategy is more effective and convenient to regulate the cardiomyocytes. Furthermore, mRNA sequencing shows that the differential expression genes in cardiomyocytes are significantly increased after photothermal strategy, which are involved in the regulation of the heart rate, cardiac conduction, and ion transport. This work establishes a promising integrated biosensing and regulating platform for photothermal therapy of bradyarrhythmia in vitro and provides reliable evidence of photothermal regulation on cardiomyocytes for cardiological clinical studies.

Manifest preexcitation with a prolonged PR interval: What is the mechanism?

A 44-year-old woman with a past history of surgical ablation of an accessory pathway presented to our facility with episodes of palpitations and dizziness. An ECG showed sinus rhythm with a prolonged PR interval and a preexcited QRS complex. An EP study revealed AV conduction through a postero-septal accessory pathway and a prolonged PR interval due to severe intra-atrial conduction delay.

The Belgian experience with concomitant surgical ablation of atrial fibrillation: a multi-centre prospective registry

Background: The Belgian 'National Institute for Health and Disability Insurance (RIZIV-INAMI)' requested prospective collection of data on all ablations in Belgium to determine the outcomes of surgical ablation of atrial fibrillation (AF) during concomitant cardiac surgery.Methods: 890 patients undergoing concomitant ablation for AF between 2011 and 2016 were prospectively followed. Freedom from AF with and without anti-arrhythmic drugs was calculated for 817 patients with follow-up beyond the 3-month blanking period and for 574 patients with sufficient rhythm-related follow-up consisting of at least one Holter registration or a skipped Holter due to AF being evident on ECG. Besides preoperative AF type, concomitant procedure and ablation, potential covariates were entered into uni- and multivariable regression models to determine predictors of outcome.Results: The overall freedom from AF beyond 3 months was 69.9% (571/817) and without anti-arrhythmic drugs at last follow-up 51.0% (417/817), respectively, 61.3% (352/574) and 44.4% (255/574) for patients with sufficient rhythm-related follow-up. Using a Kaplan-Meier estimate, freedom from AF was 89.3%, 74.9% and 59%, without antiarrhythmic drugs 74.4%, 47.8% and 32.3% at 6, 12 and 24 months, respectively. In-hospital mortality was 1.7% (15/890) and the overall survival was 95.0% at 1 year and 92.3% at 2 years. Preoperative left atrial diameter and AF type were significant predictive factors of freedom from AF in a multivariable analysis.Conclusion: Analysis of the Belgian national registry shows that concomitant surgical ablation of atrial fibrillation is safe, achieves favourable freedom from AF and, therefore, deserves to be performed in accordance to the guidelines.

The Factors Affecting Rhythm Control for Cryoablation of Atrial Fibrillation in Mitral Valve Surgery

OBJECTIVE

To evaluate the factors impacting on the conversion to sinus rhythm and on the postoperative rhythm findings in the six-month follow-up period of a mitral valve surgery combined with cryoablation Cox-Maze III procedure, in patients with atrial fibrillation.

METHODS

In this study, we evaluated 80 patients who underwent structural valve disease surgery in combination with cryoablation. Indications for the surgical procedures were determined in the patients according to the presence of rheumatic or non-rheumatic structural disorders in the mitral valve as evaluated by echocardiography. Cox-Maze III procedure and left atrial appendix closure were applied.

RESULTS

The results of receiver operating characteristics analysis indicated that the rate of conversion to the sinus rhythm was significantly higher in patients with left atrial diameters ≥ 45.5 mm and with ejection fraction (EF) ≥ 48.5%. However, the statistical differences disappeared in the sixth month. Thromboembolic (TE) events were seen only in three patients in the early period and no more TE events occurred in the six-month follow-up period.

CONCLUSION

The EF and the preoperative left atrial diameter were determined to be the factors impacting on the conversion to sinus rhythm in patients who underwent mitral valve surgery in combination with cryoablation. Mitral valve surgery in combination with ablation for atrial fibrillation does not affect mortality and morbidity in the experienced health centers; however, it remains controversial whether it will provide additional health benefits to the patients compared to those who underwent only mitral valve surgery.

The history of the wolff-Parkinson-white syndrome

While Drs Wolff, Parkinson, and White fully described the syndrome in 1930, prior case reports had described the essentials. Over the ensuing century this syndrome has captivated the interest of anatomists, clinical cardiologists, and cardiac surgeons. Stanley Kent described lateral muscular connections over the atrioventricular (AV) groove which he felt were the normal AV connections. The normal AV connections were, however, clearly described by His and Tawara. True right-sided AV connections were initially described by Wood et al., while Öhnell first described left free wall pathways. David Scherf is thought to be the first to describe our current understanding of the pathogenesis of the WPW syndrome in terms of a re-entrant circuit involving both the AV node-His axis as well as the accessory pathway. This hypothesis was not universally accepted, and many theories were applied to explain the clinical findings. The basics of our understanding were established by the brilliant work of Pick, Langendorf, and Katz who by using careful deductive analysis of ECGs were able to define the basic pathophysiological processes. Subsequently, Wellens and Durrer applied invasive electrical stimulation to the heart in order to confirm the pathophysiological processes. Sealy and his colleagues at Duke University Medical Center were the first to successfully surgically divide an accessory pathway and ushered in the modern era of therapy for these patients. Morady and Scheinman were the first to successfully ablate an accessory pathway (posteroseptal) using high-energy direct-current shocks. Subsequently Jackman, Kuck, Morady, and a number of groups proved the remarkable safety and efficiency of catheter ablation for pathways in all locations using radiofrequency energy. More recently, Gollob et al. first described the gene responsible for a familial form of WPW. The current ability to cure patients with WPW is due to the splendid contributions of individuals from diverse disciplines throughout the world.

[Treatment of atrial fibrillation]

Atrial fibrillation is a common and in most patients recurrent arrhythmia. Atrial fibrillation can increase mortality and causes at times severe symptoms in affected patients. Timely initiation of sustained oral anticoagulation is indicated in patients with atrial fibrillation at risk for stroke to prevent thromboembolic complications. Patients at risk for stroke can be identified by clinical characteristics using validated score systems, e.g., the CHADS(2) score or the Framingham score. Drugs that slow AV nodal conduction can improve symptoms associated with high ventricular rate. Cardioversion can acutely terminate atrial fibrillation in almost all patients, but many patients suffer from recurrent atrial fibrillation. The prevention of arrhythmia recurrences ("rhythm control therapy") is indicated in patients with severe arrhythmia-related symptoms. Antiarrhythmic drugs can approximately double the maintenance rate of sinus rhythm. Other drugs that were not primarily developed as antiarrhythmic agents, e.g., ACE inhibitors, sartans, and possibly statins, can further improve maintenance of sinus rhythm in selected patient groups. Catheter-based isolation of the pulmonary veins is a recently developed intervention that can cure some forms of atrial fibrillation. It is likely that a multimodal therapeutic approach will in the future allow rhythm control therapy to become more effective.

[New antiarrhythmic drugs for therapy of atrial fibrillation: I. Ion channel blockers]

During the last ten years we have made substantial progress in our understanding of the underlying mechanisms of atrial fibrillation. The high rate associated alterations in electrical and structural properties of the atria, referred to as atrial remodeling, promote the progression of atrial fibrillation. The development of new therapeutic approaches addresses three different directions: (i) prevention of atrial remodeling, especially of structural remodeling; (ii) increase of long-term efficacy of currently used drugs and improvement of their side-effect profile; and (iii) design of atria- and pathology-specific antiarrhythmic drugs without concomitant proarrhythmic effects in the ventricles. The current review outlines the pathophysiology of atrial fibrillation and focuses on electrical remodeling. The properties of new antiarrhythmic drugs for atrial fibrillation are discussed in detail.

[Anticoagulation with atrial fibrillation]

Atrial fibrillation is associated with a relevant risk for ischemic stroke: Observational studies suggest that one in four to five strokes is due to atrial fibrillation. Depending on the risk profile of an individual patient, the yearly risk for a stroke is between 2% and 14%. Continuous oral anticoagulation is indicated if atrial fibrillation is accompanied by at least one additional risk factor for thromboembolic complications. This recommendation is supported by several large randomized trials. Due to their low therapeutic range, vitamin K antagonists (phenprocoumon, warfarin, and others), the most commonly used oral anticoagulants, require regular anticoagulation monitoring. If well-controlled (international normalized ratio 2-3, in elderly patients preferably 2-2.5), oral anticoagulation prevents more than half of ischemic strokes related to atrial fibrillation, while bleeding complications are rare. In the follow-up of low risk patients (CHADS2-Score 0), oral anticoagulation becomes necessary when risk factors for thromboembolic complications develop. If a stroke occurs during oral anticoagulation and an INR>2 in a patient with atrial fibrillation, other causes than thromboembolic events should be considered. New anticoagulants--especially direct thrombin antagonists--are currently evaluated in clinical trials and may in the future facilitate anticoagulation in patients with atrial fibrillation.

Image-based guidance for minimally invasive surgical atrial fibrillation ablation

PURPOSE

Atrial fibrillation (AF) is the most common arrhythmia and results in an increased risk of ischaemic stroke. Recently, a European consortium has developed a new ablation device for minimally invasive surgical AF treatment. The device is controlled by a medical robot. Due to the minimal invasive usage, surgery using the new device needs appropriate navigation support. In this paper, we describe an image-based navigation application to guide the new device intraoperatively.

METHODS

The navigation procedure is based on intraoperative ultrasound. Variations in the position of the ablation device are transferred from the software controlling the robot to the navigation system. Due to the flexibility of the ablation device, a deformation model predicts the behaviour during repositioning. Ablation lines are interactively planned. Actually burned ablation lines are visualized during surgery. Several in vitro and ex vivo experimental set-ups were built up to test the feasibility.

RESULTS

The navigation workflow was implemented into navigation software using well-known open-source software toolkits. The navigation system has been integrated and tested successfully within the overall system. The ablation device could be localized on in vitro and ex vivo ultrasound images.

CONCLUSION

The performed trials proved the applicability of the navigation procedure. More in vivo tests are currently being performed to make the new device and the described navigation procedure ready for clinical use.

Targeted pharmacological reversal of electrical remodeling after cardioversion--rationale and design of the Flecainide Short-Long (Flec-SL) trial

Persistent atrial fibrillation (AF) causes relevant mortality and cardiovascular and noncardiovascular morbidity. Therefore, maintenance of sinus rhythm is an important clinical goal, especially when the patient is symptomatic, despite the fact that current treatment strategies are not sufficient to completely prevent recurrent AF. In addition to underlying atrial disease that predisposes to AF, AF in itself induces structural and electrical adaptations ("electrical remodeling" and "structural remodeling"). Underlying disease processes and parts of structural remodeling are not always reversible. Electrical remodeling, in contrast, is reversed by a few weeks of maintenance of sinus rhythm under experimental conditions. This corresponds to the period when most of the recurrent episodes of AF occur after cardioversion. Antiarrhythmic drugs that prolong the atrial action potential can assist in the prevention of recurrent AF by promoting the reversal of electrical remodeling. Such drugs, which are currently used over long periods after cardioversion, may only be needed until the physiological action potential duration is restored, for example, during the first few weeks after cardioversion of persistent AF. This treatment concept that we call "targeted pharmacological reversal of electrical remodeling" would limit both cost and drug-induced side effects of antiarrhythmic drug therapy after cardioversion. The Flec-SL trial, ISECTN62728743, therefore tests the main hypothesis that targeted pharmacological reversal of electrical remodeling by short-term antiarrhythmic drug therapy for 4 weeks after cardioversion is not inferior to standard long-term antiarrhythmic drug therapy for the prevention of recurrent AF after cardioversion in a parallel group, randomized, multicenter, open, blinded end point analysis design. Based on its effectiveness and pharmacokinetic profile, flecainide is used to test the study hypothesis. The trial uses daily transtelephonic electrocardiographic monitoring for all patients and will be conducted within the German Atrial Fibrillation Competence NETwork (AFNET) to facilitate inclusion of patients from electrophysiologically oriented cardiology centers, ordinary hospitals, and office-based physicians.

History of Wolff-Parkinson-White syndrome

While Drs. Wolff, Parkinson, and White fully described the syndrome that bears their names in 1930, prior case reports had already described the essentials. Over the ensuing century this syndrome has captivated the interest of anatomists, clinical cardiologists, and cardiac surgeons. Stanley Kent described lateral muscular connections over the atrioventricular (AV) groove, which he felt were the normal AV connections. The normal AV connections were, however, clearly described by His and Tawara. True right-sided AV connections were initially described by Wood et al., while Ohnell first described left free wall pathways. David Scherf is thought to be the first to describe our current understanding of the pathogenesis of the Wolff-Parkinson-White (WPW) syndrome in terms of a reentrant circuit involving both the AV node--His axis as well as the accessory pathway. This hypothesis was not universally accepted and many theories were applied to explain the clinical findings. The basics of our understandings were established by the brilliant work of Pick, Langendorf, and Katz who by using careful deductive analysis of ECGs were able to define the basic pathophysiological processes. Subsequently, Wellens and Durrer applied invasive electrical stimulation to the heart in order to confirm the pathophysiological processes. Sealy and his colleagues at Duke University Medical Center were the first to successfully surgically divide an accessory pathway and ushered in the modern area for curative therapy for these patients. Morady and Scheinman were the first to successfully ablate an accessory pathway (posteroseptal) using high-energy direct-current shocks. Subsequently, Jackman, Kuck, Morady, and a number of groups proved the remarkable safety and efficiency of catheter ablation for pathways in all locations using radiofrequency energy. More recently, Gallob et al. first described the gene responsible for a familial form of WPW. The current ability to cure patients with WPW is due to the splendid contributions of individuals from diverse disciplines from throughout the world.

Advances in the approach to treatment of supraventricular tachycardia in the pediatric population

Supraventricular tachycardia is relatively common in children. Although most forms are not life threatening, treatment options depend on appropriate diagnosis. In certain patients, medical treatments are adequate for controlling symptoms. For those in whom medical therapy is inadequate or undesirable, invasive electrophysiology techniques are a viable treatment option. Increasing experience with radiofrequency catheter ablation techniques has led to improved success rates and decreased complication rates. New technologies, such as nonradiographic mapping systems and novel ablation catheters, are additional tools that can improve the ability of pediatric electrophysiologists to approach treating tachycardia mechanisms that have previously been too challenging to treat safely.