Superior Vena Cava Flutter: Electrophysiology and Ablation

Radiofrequency catheter ablation of cranial vena cava flutter in four dogs

Four dogs were referred to our institution for incessant supraventricular tachycardias causing weakness; congestive heart failure was present in one dog. At admission, all dogs had a surface electrocardiogram showing a narrow QRS complex tachycardia with a ventricular rate ranging from 80 to 300 bpm, variable atrioventricular conduction ratio from 1:1 to 3:1, and positive atrial depolarizations in inferior leads (II, II, III, and aVF), with isoelectric lines between them. Three of four dogs had a dilated cardiomyopathy phenotype; one dog had a heart base tumor involving the cranial vena cava wall. According to the electrocardiographic findings, a presumptive diagnosis of reverse typical or atypical atrial flutter was considered, and endocardial mapping was planned for each dog. During the electrophysiologic study, continuous atrial activation compatible with atypical atrial flutter was observed in all dogs, with concealed entrainment obtained at the level of the isthmus located at the distal portion of the cranial vena cava, close to the entrance into the right atrium. A linear radiofrequency catheter ablation was performed from the right atrial wall to the distal part of the cranial vena cava with a permanent interruption of the isthmic conduction in all dogs at a 6-month follow-up.

Electrical isolation of the superior vena cava by laser balloon ablation in patients with atrial fibrillation

PURPOSE

The aim of the present study is to evaluate the feasibility and safety of SVC electrical isolation by LB ablation in patients with atrial fibrillation (AF) referred for pulmonary vein isolation (PVI).

METHODS

Electrical disconnection of the SVC was attempted by LB in 13 consecutive patients (59 ± 10.5 years, 11 male) with AF following PVI. PVI was successfully achieved by standard LB in all before attempting SVC isolation.

RESULTS

A laser beam was delivered with 6.3 ± 2.3 W and 8.4 ± 2.7 W (P = 0.001) during 5.38 ± 2.4 min and 9.75 ± 1.6 min (P = 0.024) to achieve SVC and PV, respectively. Isolation of the SVC by LB was accomplished in 8 patients (61%) without complications. Phrenic nerve palsy developed in 3 patients (23%), which resulted in early procedure termination before isolation. Technical problems or interposition of a pacemaker lead to prevented SVC isolation in the remaining 2 patients. After a mean follow-up of 19 ± 3 months, no patient recovered from phrenic nerve palsy.

CONCLUSIONS

SVC isolation by LB is feasible but associated with a high risk of phrenic nerve palsy. Limitation of laser delivery time and power appears insufficient to prevent this complication.

Bidirectional superior vena cava: right atrial conduction delay during tachycardia

The superior vena cava, like all the thoracic veins, has myocardial sleeves and plays a role in initiation and perpetuation of atrial fibrillation. Conduction delay between it and the right atrium has been shown previously. This case study shows delay in both directions during different arrhythmias in the same patient.

Thoracic Vein Arrhythmias

The thoracic veins are important foci for the genesis of ectopic atrial tachycardia and play a critical role in the pathophysiology of paroxysmal and permanent atrial fibrillation. The pulmonary veins have the highest arrhythmogenic activity and other venous structures (eg, superior vena cava, coronary sinus and ligament of Marshall) have also been shown arrhythmogenic potential. Thoracic veins contain cardiomyocytes with distinct electrical activities and complex anatomical structures. This review summaries the current understanding of the basic and clinical electrophysiology of thoracic vein arrhythmias.

Acute and Chronic Effects of Extensive Radiofrequency Lesions in the Canine Caval Veins: Implications for Ablation of Atrial Arrhythmias

BACKGROUND

Although radiofrequency (RF) ablation within the caval veins has been increasingly used to treat a variety of atrial tachyarrhythmias, the consequences of RF ablation in the caval veins are unknown. We explored the acute and chronic angiographic and pathological effects of extensive RF ablation in the caval veins.

METHODS

Under fluoroscopy guidance, conventional (4 mm tip, 60 degrees C, 60 seconds) RF applications (n = 6-7) were delivered in each vena cava (from +/-2 cm into the vein to the veno-atrial junction) of 15 dogs (10 +/- 3 kg). Animals were killed 1 hour and 5 weeks after ablation for histological analysis. Angiography was performed before ablation (acute dogs only) and at sacrifice to assess the degree of vascular stenosis.

RESULTS

In acute dogs (n = 5), luminal narrowing was noted in 10/10 (100%) targeted veins (mild in two; moderate in three and severe in five, including two total occlusions). In the six chronic animals that completed the protocol (four died during follow-up), stenosis was also observed in 12/12 (100%) ablated veins (mild in six; moderate in four and severe in two). Of these, one superior vena cava was suboccluded with development of extensive collateral circulation. Histologically, acute lesions displayed typical transmural coagulative necrosis, whereas chronic lesions revealed intimal proliferation, necrotic muscle replaced with collagen, endovascular contraction, and disruption and thickening of the internal elastic lamina.

CONCLUSION

In this model, extensive RF ablation in the caval veins may result in significant vascular stenosis. These findings may have implications for catheter ablation of arrhythmias originating within the caval veins.

Temas de actualidad 2005: electrofisiología y arritmias

Cardiac electrophysiology laboratories deal with a wide range of pathological conditions, diagnostic techniques, and treatments. Since a huge quantity of material has been published in recent months, this article will be limited to discussion of the most significant developments in the prognostic evaluation of arrhythmias, hereditary disease, syncope, atrial fibrillation, implantable cardioverter-defibrillators, cardiac resynchronization therapy, and catheter ablation. Even within these areas, discussion will be restricted to specific concrete topics and to a limited number of publications that were judged to have important implications for clinical practice. Our principal aim was to provide clinical cardiologists with an overview of the latest developments in cardiac electrophysiology.