Coronary ischemia induced by radiofrequency ablation in the left atrium

Pathophysiological Effects on Coronary Arteries Following Radiofrequency Ablation: A Comprehensive Review

Radiofrequency ablation (RFA) is a safe and effective treatment for patients experiencing ventricular and atrial tachyarrhythmias. While complications after RFA are generally rare, the occurrence of coronary artery (CA) injury, albeit infrequent, can have significant clinical implications. Given the proximity of CAs to common ablation sites, understanding the interplay between RFA and CA perfusion pathophysiology is paramount. Although previous studies have discussed the presentation and outcomes of CA injury post-ablation, a comprehensive review consolidating the mechanisms of CA injury following RFA remains absent in the cardiology literature. In this review, we conducted an extensive literature search spanning the past three decades to explore the link between the biophysics of RFA and CA perfusion pathophysiology, focusing on injury mechanisms. We delve into RFA lesion pathology, elucidate the mechanisms of CA injury resulting from RFA, and examine factors influencing lesion formation, such as convective cooling and the "shadow effect." Furthermore, we outline methods to mitigate CA injury post-RFA and propose novel research avenues to optimize lesion formation and ensure the safety of arrhythmia treatments, particularly in cases where tissue ablation is performed close to CAs.

The Blinding Period Following Ablation Therapy for Atrial Fibrillation: Proarrhythmic and Antiarrhythmic Pathophysiological Mechanisms

Atrial fibrillation (AF) causes heart failure, ischemic strokes, and poor quality of life. The number of patients with AF is estimated to increase to 18 million in Europe in 2050. Pharmacological therapy does not cure AF in all patients. Ablative pulmonary vein isolation is recommended for patients with drug-resistant symptomatic paroxysmal AF but is successful in only about 60%. In patients in whom ablative therapy is successful on the long term, recurrence of AF may occur in the first weeks to months after pulmonary vein ablation. The early recurrence (or delayed cure) of AF is not understood but forms the basis for the generally accepted 3-month blinding (or blanking) period after ablation therapy, which is not included in the evaluation of the eventual success rate of the procedures. The underlying pathophysiological processes responsible for early recurrence and the delayed cure are unknown. The implicit assumption of the blinding period is that the AF mechanism in this period is different from the ablation-targeted AF mechanism (ectopy from the pulmonary veins). In this review, we evaluate the temporary and long-lasting pro- and antiarrhythmic effects of each of the pathophysiological processes and interventions (necrosis, ischemia, oxidative stress, edema, inflammation, autonomic nervous activity, tissue repair, mechanical remodeling, and use of antiarrhythmic drugs) occurring in the blinding period that can modulate AF mechanisms. We propose that stretch-reducing ablation scar is a permanent antiarrhythmic mechanism that develops during the blinding period and is the reason for delayed cure.

Incidence and characteristics of transient St-segment elevation during transseptal puncture

PURPOSE

Delineate retrospectively and prospectively the incidence and characteristics of transient ST-segment elevation during transseptal puncture.

METHODS

The study retrospectively evaluated 307 patients from January 1, 2015, to December 31, 2017, and prospectively evaluated 231 patients from January 1, 2018, to July 31, 2019.

RESULTS

The presence of ST-segment elevation was significantly higher in the prospective sample than in the retrospective sample (5.2% vs. 1.3%, p < 0.05). Between the two groups, there was no significant difference in age, sex, comorbidities, left atrial volume index, and the etiology of atrial fibrillation among patients with ST-segment alteration. In all patients, the ST-segment elevation was observed in the inferior wall derivations, except for one patient with ST elevation in lead I, AVL, V1-V4 during the septal puncture, associated with sinus bradycardia and reversed hypotension with intravenous fluids. Comparative analysis of the systolic and diastolic arterial pressure and the minimum heart rate during the phenomenon demonstrated more severity in the retrospectively evaluated population than in the prospective population. There was a significant association between the occurrence of ST-segment elevation > 2 mm and the presence of symptoms. In these patients, coronary angiography showed no alterations. Atropine was administered to one patient who presented with junctional bradycardia after the puncture. This medication reversed the situation.

CONCLUSION

ST-segment elevation is a short-term phenomenon that can occur during transseptal catheterization without clinically evident symptoms. The catheter ablation procedure can be safely concluded despite the occurrence of the phenomenon.

ST-Segment Elevation Associated with Mobitz II Atrioventricular Block During Transseptal Puncture for Atrial Fibrillation Ablation

Pulmonary veins electrical isolation as an invasive treatment of atrial fibrillation has been widely used in electrophysiology laboratories. This case report presents a rare and transient complication, during transseptal puncture for atrial fibrillation ablation. ST-segment elevation, hypotension and bradyarrhythmia related to catheterization were observed despite cineangiocoronariography without obstructive lesions. Clinical stability was achieved after administration of intravenous atropine and saline solution. It is speculated that the phenomenon is attributed to an increased vagal tone after the mechanical effect of transseptal puncture in the interatrial vagal network. The procedure was completed despite the phenomenon.

Short-term outcomes of atrial flutter ablation

BACKGROUND

Understanding the factors associated with early readmissions following atrial flutter (AFL) ablation is critical to reduce the cost and improving the quality of life in AFL patients.

METHOD

The study cohort was derived from the national readmission database 2013-2014. International Classification of Diseases, 9th Revision (ICD-9-CM) diagnosis code 427.32 and procedure code 37.34 were used to identify AFL and catheter ablation, respectively. The primary and secondary outcomes were 90-day readmission and complications including in-hospital mortality. Cox proportional regression and hierarchical logistic regression were used to generate the predictors of primary and secondary outcomes respectively. Readmission causes were identified by ICD-9-CM code in primary diagnosis field of readmissions.

RESULT

Readmission rate of 18.19% (n = 1,010 with 1,396 readmissions) was noted among AFL patients (n = 5552). Common etiologies for readmission were heart failure (12.23%), atrial fibrillation (11.13%), atrial flutter (8.93%), respiratory complications (9.42%), infections (7.4%), bleeding (7.39%, including GI bleed-4.09% and intracranial bleed-0.79%) and stroke/TIA (1.89%). Multivariate predictors of 90-day readmission (hazard ratio, 95% confidence interval, P value) were preexisting heart failure (1.30, 1.13-1.49, P < 0.001), chronic pulmonary disease (1.37, 1.18-1.58, P < 0.001), anemia (1.23, 1.02-1.49, P = 0.035), malignancy (1.87, 1.40-2.49, P < 0.001), weekend admission compared to weekday admission (1.23, 1.02-1.47, P = 0.029), and length of stay (LOS) ≥5 days (1.39, 1.16-1.65, P < 0.001). Note that 50% of readmissions happened within 30 days of discharge.

CONCLUSION

Cardiac etiologies remain the most common reason for the readmission after AFL ablation. Identifying high risk patients, careful discharge planning, and close follow-up postdischarge can potentially reduce readmission rates in AFL ablation patients.

Acute myocardial infarction after radiofrequency catheter ablation of typical atrial flutter

A 53-yr-old man underwent radiofrequency ablation to treat persistent atrial flutter. After the procedure, the chest pain was getting worse, and the electrocardiogram showed ST-segment elevation in inferior leads with reciprocal changes. Immediate coronary angiography showed total occlusion with thrombi at the distal portion of the right coronary artery, which was very close to the ablation site. Intervention with thrombus aspiration and balloon dilatation was successful, and the patient recovered without any kind of sequelae. Although the exact mechanism is obscure, the most likely explanation is a thermal injury to the vascular wall that ruptured into the lumen and formed thrombus. Vasospasm and thromboembolism can also be other possibilities. This case raise the alarm to cardiologists who perform radiofrequency ablation to treat various kinds of cardiac arrhythmias, in that myocardial infarction has been rarely considered one of the complications.

Transient ST Elevation in Vagally Mediated Atrial Fibrillation

We report a case of vagally mediated atrial fibrillation on a young otherwise healthy man, with straight type ST-segment elevation in inferolateral leads that resolved a few hours after restoration of sinus rythm, a phenomenon that has never been previously reported. Even though no definite conclusion about the underlying mechanism of the ST-elevation can be made, this effect might probably be the result of intense parasympathetic tone and could be used to differentiate the causality.

Coronary artery pathophysiology after radiofrequency catheter ablation: review and perspectives

BACKGROUND

Radiofrequency ablation (RFA) has proven to be an effective and safe treatment in patients with ventricular and atrial tachyarrhythmias. Among complications arising after RFA, the incidence of coronary artery (CA) injury is exceedingly low. When CA injury does occur, however, it can be clinically devastating. The proximity of CAs to common ablation sites suggests that the relationship between RFA and CA perfusion pathophysiology is important for optimal lesion formation and safe arrhythmia treatments.

OBJECTIVE

Although others have described the presentation and outcomes of patients with CA injury after ablation, a review that consolidates the mechanisms of CA injury after RFA has yet to be presented in the cardiology literature.

METHODS

We conducted an extensive literature search of studies published over the past 30 years that relate the biophysics of RFA with CA perfusion pathophysiology and injury.

RESULTS

We present a review of the dynamic relationship between RFA and CA perfusion. We describe RFA lesion pathology, mechanisms of CA injury from RFA, and factors that influence lesion formation, such as convective cooling and the shadow effect.

CONCLUSION

We summarize methods to mitigate CA injury after RFA and propose new research avenues to optimize lesion formation and safe arrhythmia treatments when tissue is ablated in the vicinity of CAs.

CT of the Pulmonary Veins

Atrial fibrillation (AF) is a common cardiac rhythm disturbance and its incidence is increasing. Radiofrequency catheter ablation (RFCA) is a highly successful therapy for treating AF, and its use is becoming more widespread; however, with its increasing use and evolving technique, known complications are better understood and new complications are emerging. Computed tomography (CT) of the pulmonary veins, or more correctly, the posterior left atrium (LA), has an established role in precisely defining the complex anatomy of the LA and pulmonary veins preablation and has an expanding role in identifying the myriad of possible complications postablation. The purposes of this article are: to review AF and RFCA; to discuss CT evaluation of the LA and pulmonary veins preablation; and to review the complications of RFCA focusing on the role of CT postablation.

ST-segment elevation induced during the transseptal procedure for radiofrequency catheter ablation of atrial fibrillation

We report two cases of transient coronary artery ischemia manifested as chest discomfort with ST-segment elevation in inferior leads during the transseptal procedure for radiofrequency catheter ablation of atrial fibrillation. This unexpected complication was resolved by intravenous administration of nitrates. All patients exhibited normal coronary arteries in angiography. A neurally mediated pathway activated by the mechanical effects of the transseptal puncture on the interatrial vagal network leading to coronary artery spasm may be considered as a possible explanation of this phenomenon. Coronary artery embolism following the transseptal procedure represents a different underlying mechanism.

Transient ST-segment-elevation during pulmonary vein ablation using circumferential coiled microelectrodes in a prospective multi-centre study†

AIMS

Paroxysmal atrial fibrillation (PAF) is predominantly triggered by focal ectopies located within the pulmonary veins (PV). The BITMAP Study (Breakthrough and Isolation Trial: Mapping and Ablation of Pulmonary Veins) investigated prospectively the safety and efficacy of a catheter design with circumferential mapping and ablation electrodes. We report the phenomenon of ST-segment-elevation during catheter placement in the left atrium (LA) and superior PVs in this multi-centre study.

METHODS AND RESULTS

Forty-three patients (57+/-10 years) with PAF were included in this study. Radiofrequency catheter (RFC) ablation supported by the 4F REVELATION Helix microcatheter (Cardima Inc., Freemont, CA, USA) with eight distal-coiled microelectrodes for bipolar mapping and ablation. RFC was applied at the ostial region of PV (30 W, 45-50 degrees C) with a maximum of four RFC applications per electrode. In four of the 43 patients from three centres, we recorded the occurrence of ST-segment-elevation greater than 0.2 mV and accompanying left thoracic discomfort. The ECG changes and the symptoms started abruptly and lasted for 4.2+/-2.2 min. Pericardial effusion could instantaneously be excluded by echocardiography in all cases. Coronary angiograms were performed in three patients with the longest episodes; no thrombotic material or air emboli were present. The symptoms and the ECG changes resolved completely in all patients.

CONCLUSION

The phenomenon of ST-segment-elevation during LA- and PV-mapping in patients with PAF may be a common occurrence. In this prospective multi-centre trial, we demonstrated the reversibility of this phenomenon; no cardiovascular or cerebral damage was reported during both the procedure and the follow-up. Although the mechanism is still unclear, vasospasm may contribute to this phenomenon because of autonomic dysregulation.

Transcatheter cryoablation of tachyarrhythmias in children

OBJECTIVES

We sought to describe the early pediatric experience of transcatheter cryoablation, and identify whether specific arrhythmia substrates and/or ablation locations were particularly suited to cryoablation.

BACKGROUND

Radiofrequency (RF) ablation has become established therapy for pediatric tachyarrhythmias. However, challenges remain in terms of the safety and efficacy of RF ablation in specific locations; new methods may address these issues.

METHODS

Prospective data were available for 64 patients age 13 +/- 4 (mean +/- SD) years undergoing cryoablation at 14 centers participating in the Cryocath International Patient Registry. Dysrhythmia duration was 5.0 +/- 4.2 years, with diagnoses of atrioventricular node re-entrant tachycardia (AVNRT) (n=30), anteroseptal (n=11), midseptal (n=5), or other (n=15) accessory pathway (AP) mediated AV re-entry, ventricular tachycardia (VT) (n = 3), and ectopic atrial tachycardia (EAT) (n=2). Two patients had more than one arrhythmia substrate. Transcatheter cryoablation was offered by cardiologist preference after written informed procedural consent of each patient and/or legal guardian. Cryomapping was performed at -30 degrees C and cryoablation was delivered with 4-min applications at -75 degrees C.

RESULTS

Acute success was achieved in 45 of 65 (69%) cryoablation patients, with best success rates in AVNRT (83%) and right septal AP (75%), and lower success rates in other AP (43%), VT (66%), and EAT (0%). No device-related adverse events were reported. The success of radiofrequency (RF) ablation applied in 14 cryoablation failures was 4 of 4 for AVNRT patients, 1 of 1 for anteroseptal AP patients, 5 of 6 for other AP patients, 0 of 1 for VT patients, and 0 of 2 for EAT patients.

CONCLUSIONS

Transcatheter cryoablation is a safe and well-tolerated alternative to RF ablation in pediatric patients on the basis of our initial experience. Success is highest in AVNRT and in substrates recognized as technically challenging or risky for RF ablation.