Thais Nascimento

Impact of prophylactic corticosteroids on systemic inflammation after extensive atrial ablation in pigs

AIMS Prophylactic corticosteroids have been reported to attenuate the increase in C-reactive protein (CRP) and the incidence of atrial fibrillation (AF) both after heart surgery and AF ablation. We tested the impact of a single prophylactic corticosteroid dose on ultrasensitive CRP 24 h and 14 days after extensive linear atrial ablation (8 mm or 3.5 irrigated tip) guided by electroanatomical mapping (NavX) in pigs with normal hearts. METHODS AND RESULTS Pigs (n = 19; 35 kg) were divided into three groups: corticoid (n = 7), atrial ablation with administration of 500 mg methylprednisolone intravenous at anaesthetic induction; control (n = 7), atrial ablation only; and sham (n = 5), surgical procedure without ablation. Troponin and CRP were measured before, 24 h and 14 days after the procedure. After sacrifice, lesions were analysed macroscopically and histologically. Linear lesions were created in the right (n = 23) and left (n = 21) atrium of 14 animals, with no difference between groups. In all groups there was elevation of troponin and CRP 24 h after ablation, with a return to baseline values after 14 days. However, CRP levels of the control, corticoid, and sham groups were similar at all three time points analysed (baseline P = 0.52, 24 h P = 0.21, 14 days P = 0.66). Histological analysis did not show any difference between corticoid and control groups. CONCLUSION In this model, extensive biatrial RF ablation, per se, does not promote systemic inflammation. The use of a prophylactic single corticoid dose before ablation did not prevent systemic inflammation or alter the healing of the lesions.

Impact of corticosteroids on late growth of radiofrequency lesions in infant pigs: histopathological and electroanatomical findings

AIMS Corticosteroids attenuate late growth of radiofrequency (RF) lesions in the thigh muscle of infant rats. We sought to assess the impact of these drugs on the late growth of RF lesions in immature swine myocardium and to determine the electroanatomical mapping (EAM) characteristics of these lesions. METHODS AND RESULTS Radiofrequency (60°C; 60 s) lesions were created in the right atrium (n = 2) and ventricle (n = 2) of 14 piglets (age 65 days; weight 5 kg) and 3 adults. Piglets were divided into: controls (n = 7) and treated (n = 7), receiving hydrocortisone (10 mg/kg iv after RF) and prednisone (1 mg/kg/day) for 29 days. After 8 months, animals were sacrificed for histological analysis. In four piglets, endocardial and epicardial voltage EAM were performed. In infant groups, the dimensions of atrial (11 ± 5 vs. 13 ± 7 mm) and ventricular (12 ± 3 vs. 11 ± 3 mm) lesions were similar. In adults, atrial (6 ± 1 mm) and ventricular (6 ± 1 mm) lesions were smaller. In controls, ventricular lesions depicted dense fibrosis and multiple strands of fibrous tissue extending from the lesion into normal muscle. Treated piglets revealed scars exhibiting less dense fibrosis with predominance of fibroadipose tissue and less collagen proliferation. Large atrial and ventricular low-voltage areas corresponding to the macroscopic lesions were identified in all animals. CONCLUSION Radiofrequency lesions in infant pigs reveal late growth and invasion of normal muscle by intense collagen proliferation. Corticosteroids do not prevent late enlargement of the lesions but modulate the fibrotic proliferation. The expressive growth of the lesion may generate low-voltage areas detectable by EAM.

Are the virtual lines created with the ensite electroanatomical mapping system really continuous

Background EnSiteNavx electroanatomic mapping system is widely used in radiofrequency (RF) atrial fibrillation ablation, helping the creation of linear lesions. However, the correspondence of the virtual line created by EnSite with the pathological lesion has not yet been evaluated. Objective to assess the continuousness of Ensite-guided virtual lines in a swine model. Methods we performed RF ablation linear lesions (8mm and irrigated catheters tips) in both atria of 14 pigs (35Kg) guided by the EnSite. The animals were sacrificed 14 days post-ablation for macroscopic and histological analysis. Results a total of 23 lines in the right atrium and 21 lines in the left atrium were created in 14 animals. The medium power, impedance and temperature applications were 56 W, 54 ºC and 231 Ω for the 8mm tip, and 39W, 37ºC, 194 Ω for the irrigated tip catheter, respectively. All (100%) lines were identified on the epicardial and endocardial surfaces, denoting transmurality. At macroscopic examination, lesions were extensive and pale, continuous, with 3.61 cm long and 0.71 cm deep. The transmurality of the lesions was confirmed by microscopy. There was a correlation in the location of the lines at the virtual map and the anatomical lesions in 21 of 23 (91.3%) of the right atrium and 19/21 (90.4%) of the left atrium. Conclusion In this model, the lines created in the virtual map by EnSiteNavX system correspond to continuous transmural linear lesions in anatomical specimen, suggesting that this method is suitable for linear ablation of atrial fibrillation.

Effects of Corticosteroid Therapy on the Long‐Term Outcome of Radiofrequency Lesions in the Swine Caval Veins

Background: We explored the angiographic and pathological effects of corticosteroids on the long‐term outcome of radiofrequency (RF) ablation lesions in the swine caval veins.