João Melo

Surgery for atrial fibrillation using radiofrequency catheter ablation: assessment of results at one year.

OBJECTIVE The results obtained in 43 patients using direct intraoperative radiofrequency catheter ablation, as an alternative to surgical incisions, to perform atrial fibrillation surgery, are presented. METHODS Forty-three patients with ages ranging from 43 to 74 years (x = 59), with chronic atrial fibrillation with an average duration 6+/-5 years were operated. Eleven patients suffered from clinically relevant tachyarrythmia and eight had previous thromboembolic events. All but one patient had concomitant mitral valve surgery. Direct intraoperative radiofrequency catheter ablation was used to perform endocardial bilateral isolation of the pulmonary veins from the left atrium. RESULTS There were no local or general complications, namely bleeding or thromboembolic events. Of the 33 patients with more than 3 months of follow-up, 36% remained in atrial fibrillation (Santa Cruz score 0); 30% had Score 4; 18% had Score 3; 6% had Score 2; 9% had Score 1. CONCLUSIONS We conclude that the use of intraoperative radiofrequency catheter ablation is fast and safe. Presently, this is our method of choice for surgical treatment of atrial fibrillation in mitral patients.

Endocardial and epicardial radiofrequency ablation in the treatment of atrial fibrillation with a new intra-operative device

OBJECTIVE Atrial fibrillation has been a difficult problem to solve in many surgical patients, especially in those with mitral valve pathology. This study evaluates the results of endocardial and epicardial radiofrequency ablation with a new intra-operative device in the treatment of atrial fibrillation. METHODS We operated on 65 patients with atrial fibrillation, 58 of which had concomitant mitral surgery. Atrial fibrillation was chronic (over 1 year) in 46 patients (group A) and paroxysmal or recent onset in 12 (group B). Group C had lone atrial fibrillation (two), concomitant coronary artery disease (four) or a sarcoma (one). Bilateral pulmonary vein isolation with a new intra-operative device was performed through multiple dry lesions in all patients. Groups A and B had endocardial applications at 70 degrees C during 60 s and group C had epicardial applications at 75 degrees C. Three group C patients had epicardial applications off pump. Atrial wall biopsies were performed in nine patients from groups A and B. RESULTS There were no serious post-operative complications. At 1 month follow-up 54% of all patients were out of atrial fibrillation and 34% were in normal sinus rhythm with bilateral atrial contraction (Santa Crus Score 4). At 6 months follow-up, in spite of some crossover of patients among groups, similar results were obtained. The success of the procedure was 69% (Santa Crus scores 3 and 4) in mitral patients with a left atrial volume smaller than 200 cm(3). Preliminary data on the transmurality of the lesions is presented. The patients submitted to epicardial radiofrequency ablation (group C) have satisfactory results at 1 month (six out of seven were out of AF). CONCLUSIONS Both endocardial and epicardial RF applications are simple and quick to perform and do not pose an additional risk for most patients. Furthermore we believe that it is possible to perform bilateral epicardial radiofrequency ablation of the pulmonary veins without cardiopulmonary bypass. Further refinements of the technique are needed to assure transmurality of all lesions and better results.

When and how to report results of surgery on atrial fibrillation

OBJECTIVE Several medical, interventional and surgical techniques are used to treat atrial fibrillation, aimed at different goals and having variable success rates. To be able to assess and compare all these techniques a methodology of study and a classification is proposed. METHODS We developed a five grade score, named the Santa Crus Score, based upon the post-operative atrial rhythm and the effective atrial contraction. Score 0 corresponds to a persistence of atrial fibrillation, the presence of a regular rhythm is grade 1, 2 or 3 if there is no atrial contraction; right atrial contraction; or bilateral atrial contraction, respectively. Score 4 corresponds to sinus rhythm and bilateral atrial contraction. Surgery for atrial fibrillation was performed on 51 patients since 1992. All patients but two had associated mitrial surgery. Three different maze techniques were performed on 17 patients and the pulmonary veins isolation procedure on 34 patients. Patients were reassessed at 1, 6, 12, 24 and 36 months. RESULTS After the maze I procedure atrial fibrillation eradication was achieved in 88% of patients but none scored 4. Three patients changed score during the first year. All maze III patients scored 0 initially and one changed to score 3 in the first year. Sixty percent of the maze IIIA patients scored 4, but one evolved to score 0 at 6 months. The pulmonary veins isolation technique eliminated atrial fibrillation in 71% of the patients initially, and in 60% after 1 year, and achieved a score of 4 in a third of the patients. CONCLUSION This classification considers the intermediate grades of success that can occur with absence of atrial fibrillation and is applicable to all forms of therapy.

Epicardial radiofrequency applications: in vitro and in vivo studies on human atrial myocardium

OBJECTIVES To obtain a better understanding of tissue damage induced in human atria by epicardial radiofrequency ablation and its correlation with intra-tissue temperatures measured sub-epicardially and sub-endocardially. METHODS Radiofrequency (RF) currents were delivered to human atrial tissues using experimental set-ups to simulate surgical RF epicardial ablation at 80, 85 and 90 degrees C. Sub-endocardial and sub-epicardial temperatures were measured with thermocouples during the ablations. Twelve samples from in vitro epicardial ablations were histologically assessed. Localized RF epicardial ablations at same temperatures were performed on 38 mitral patients with concomitant atrial fibrillation (AF) before full cardiopulmonary bypass and samples histologically assessed. All patients had endocardial RF ablation at 70 degrees C to treat AF. RESULTS In vitro Sub-endocardial temperatures were lower than 50 degrees C except on thin atria (approximately 2-3 mm) in ablations at 80 and 85 degrees C and on thicker atria (approximately 5 mm) in ablations at 90 degrees C. Lesions measured 0.85-1.98 mm, all showed epicardial and myocardial damage but none were transmural. Mitral patients: Lesions measured 0.38-3.25 mm and 13/25 induced at 70 degrees C, 2/8 at 80 degrees C, 1/4 at 85 degrees C and 0/1 at 90 degrees C were confined to the epicardium leaving the myocardium undamaged. The remaining had damage of the epicardium and of variable portions of the myocardium, and three were transmural. CONCLUSIONS The application temperature and the intra-tissue temperature are not the sole factors that determine lesion depth. The thickness and the composition of the epicardium and of the myocardium are major determinants in the formation of the lesion.

Ventral cardiac denervation reduces the incidence of atrial fibrillation after coronary artery bypass grafting

OBJECTIVES Because the autonomic nervous system is an important determinant in the appearance of atrial fibrillation, we have assessed the role of ventral cardiac denervation for its prevention. METHODS Patients undergoing low-risk coronary artery surgery were enrolled. No routine antiarrhythmic drugs were administered before or after the operation. Ventral cardiac denervation was performed in 207 patients, and 219 patients were used as control subjects. Denervation was performed before cardiopulmonary bypass. The groups were comparable regarding demographic, clinical, and operative variables. RESULTS The additional time for the denervation was 5 +/- 2 minutes, and there were no associated complications. Postoperative atrial fibrillation was present in 15 (7%) patients undergoing ventral cardiac denervation (95% confidence interval, 4%-12%) and in 56 (27%) control subjects (95% confidence interval, 18%-35%). Patients submitted to ventral cardiac denervation had fewer and less severe episodes of atrial fibrillation, and no patient had atrial fibrillation after discharge. Ventral cardiac denervation was the most significant predictor of postoperative atrial fibrillation (odds ratio, 0.42; confidence interval, 0.23-0.78; P =.006). Age of greater than 65 years (odds ratio, 1.67; confidence interval, 0.96-2.9; P =.067) was a highly suggestive predictor. The analysis of the effect of ventral cardiac denervation correlated with the patients age showed a more pronounced effect in patients younger than 70 years (odds ratio, 0.43; confidence interval, 0.22-0.86; P =.022) CONCLUSIONS Ventral cardiac denervation is a fast and low-risk procedure. Its use significantly reduces the incidence and severity of atrial fibrillation after routine coronary artery bypass surgery. Patients younger than 70 years of age are expected to have a higher success rate than those older than 70 years.

Atrioventricular valve repair using externally adjustable flexible rings

Initial results obtained with a new flexible ring, adjustable from outside of the heart after interruption of extracorporeal circulation, are presented. Twenty-five rings have been inserted in 20 patients, 14 in the mitral position and 11 in the tricuspid position. In 8 of the 14 patients receiving mitral annuloplasty, other standard mitral valve repair techniques were used. Adjustment, assisted by intraoperative transesophageal color Doppler echocardiography, was done for 10 (71%) of the mitral rings and for 8 (73%) of the tricuspid rings. Residual mitral regurgitation disappeared or became minimal in 9 (90%) patients, and a mild regurgitation remained in 1. In all patients who received tricuspid rings regurgitation was abolished after the adjustment. There was no hospital or late mortality. After a maximum follow-up of 6 months results are comparable in the tricuspid and mitral positions and echocardiographic evaluation revealed stable competent valves in all patients but one, who underwent reoperation because of failure of a mitral valve chordae shortening procedure. The use of externally adjustable rings for the mitral and tricuspid valves is a safe alternative for atrioventricular valve annuloplasty and has the additional advantage of reducing postrepair regurgitation.

Mechanisms underlying degeneration of cryopreserved vascular homografts

OBJECTIVE To analyze the mechanism(s) underlying homograft degeneration, we designed an experimental model in which the behavior of cryopreserved autografts and homografts, as well as fresh autografts, implanted in the same animal was compared. METHODS A cryopreserved homograft was implanted in the aorta of 14 sheep. The excised aortic autologous segment was then subjected to cryopreservation, and 1 to 8 weeks later it was implanted 1 to 2 cm below the cryopreserved homograft. The intermediate segment of the native aorta, the fresh autograft, was dissected at this point. Animals were put to death at different times and the implanted segments were harvested together with a portion of native aorta. Histologic and immunohistochemical analyses, as well as cell viability assessments, were then performed on the explanted segments. Similar studies were also conducted on fragments of cryopreserved autografts and homografts before implantation. RESULTS With the exception of a partial loss of the endothelium, cryopreserved specimens retained cell viability and morphologic integrity before implantation. Explanted cryopreserved homografts showed profound changes affecting all strata, as well as a decline in cell viability. Lymphocyte infiltrates were found up to 12 months after implantation. Endothelium was always absent in cryopreserved homografts. However, a reendothelialization of the cryopreserved autografts was observed. After an initial period of neuronal degeneration, reenervation of the cryopreserved autograft segment occurred 6 to 12 months after the operation. Findings regarding the fresh autografts were similar to those of the cryopreserved autografts. CONCLUSION Our results suggest that the immunologic reaction rather than the cryopreservation process is responsible for the degenerative process occurring in cryopreserved homografts.

No Evidence of Chaos in the Heart Rate Variability of Normal and Cardiac Transplant Human Subjects

Heart Rate in Normal and Cardiac Transplant Subjects. Introduction: The variability observed in the heart rate may reflect fundamental aspects of cardiac activity. It has been under discussion whether heart rate variability (HRV) is due to noise or chaos, which is irregular behavior occurring in deterministic nonlinear systems.

Histologic and genetic assessment of explanted allograft valves

A possible way of analyzing the immune response triggered by the allograft and the cellular viability is to compare immunocompetent and immunosuppressed patients, such as those having valve replacement and heart transplantation, respectively. These groups differ in immunosuppression therapy, preparation methods, valve hemodynamics. In the present study, we investigated polymerase chain reaction-amplified DNA flanking hypervariable (CA)n regions obtained from valve leaflets taken from patients having valve replacement or heart transplantation and performed a histologic analyses of the cells. In addition, we assessed an autograft valve to compare the hemodynamic effects on the cellular composition of the valve leaflet. We conclude that leaflet cellularity of the heart transplantation and autograft patients is superior to that of the valve replacement patients. These differences were consistent with the occurrence of an immune response in the valve replacement group, which was prevented or abrogated by immunosuppressive therapy administered to the heart transplantation group. However, it cannot be excluded that preparation procedures have a long-term effect on the extracellular matrix, leading to deterioration of cell adhesion and homing conditions.

Comparison of the Healing Mechanisms of Myocardial Lesions Induced by Dry Radiofrequency and Microwave Epicardial Ablation

Background: Histological assessment of the evolution of lesions induced on a pigs left atrium by microwave (MW) epicardial applications and comparison with dry radiofrequency (RF) lesions.