An in vivo comparison of radiofrequency cardiac lesions formed by standard and magnetically steered 4 mm tip catheters.

Background. In vivo comparison of cardiac radiofrequency ablation lesions between standard and magnetically steered 4 mm tip catheters has never been reported.Methods. High and low right atrium (RA) free wall, isthmus, right ventricle (RV) free wall and outflow tract lesions were studied macroscopically and microscopically five days after lesion formation in seven pigs. Shape, size, thrombus formation, and ablation parameters were compared. The effect of minimal, medium and high wall contact was assessed by a contact measurement utility for magnetic catheters.Results. All 14 RA free wall lesions were transmural with a similar epicardial and endocardial surface area. In the RV, the epicardial area usually appeared to be smaller than the endocardial area with standard catheters. Isthmus lesions were difficult to assess transmurality. There was no difference in endocardial area: standard 39 mm(2) (range 16 to 82 mm(2)) vs. magnetic 36 mm(2) (range 23 to 111 mm(2)). If the catheter tip was perpendicular to the tissue, magnetic lesions were more often round or oval, while standard lesions were more often elongated (p<0.05). When the catheter tip was parallel to tissue, lesions always tended to be elongated. Microscopic characteristics were similar. The contact utility was not useful. Average impedance (p<0.0001) and energy delivered (p<0.05) were less with magnetic catheters.Conclusion. Lesions from magnetically steered catheters are transmural of similar size, but with less variability than standard catheter lesions when the tip is perpendicular to the tissue. Magnetic lesions are associated with lower impedance and energy delivery. This suggests a more stable tip-to-tissue contact. (Neth Heart J 2010;18:66-71.).

Acute success and short-term follow-up of catheter ablation of isthmus-dependent atrial flutter; a comparison of 8 mm tip radiofrequency and cryothermy catheters.

OBJECTIVES: To compare the acute success and short-term follow-up of ablation of atrial flutter using 8 mm tip radiofrequency (RF) and cryocatheters. METHODS: Sixty-two patients with atrial flutter were randomized to RF or cryocatheter (cryo) ablation. Right atrial angiography was performed to assess the isthmus. End point was bidirectional isthmus block on multiple criteria. A pain score was used and the analgesics were recorded. Patients were followed for at least 3 months. RESULTS: The acute success rate for RF was 83% vs 69% for cryo (NS). Procedure times were similar (mean 144+/-48 min for RF, vs 158+/-49 min for cryo). More applications were given with RF than with cryo (26+/-17 vs. 18+/-10, p<0.05). Fluoroscopy time was longer with RF (29+/-15 vs. 19+/-12 min, p<0.02). Peak CK, CK-MB and CK-MB mass were higher, also after 24 h in the cryo group. Troponin T did not differ. Repeated transient block during application (usually with cryoablation) seemed to predict failure. Cryothermy required significantly less analgesia (p<0.01), and no use of long sheaths (p<0.005). The isthmus tended to be longer in the failed procedures (p=0.117). This was similar for both groups, as was the distribution of anatomic variations. Recurrences and complaints in the successful patients were similar for both groups, with a very low recurrence of atrial flutter after initial success. CONCLUSIONS: In this randomized study there was no statistical difference but a trend to less favorable outcome with 8 mm tip cryocatheters compared to RF catheters for atrial flutter ablation. Cryoablation was associated with less discomfort, fewer applications, shorter fluoroscopy times and similar procedure times. The recurrence rate was very low. Cryotherapy can be considered for atrial flutter ablation under certain circumstances especially when it has been used previously in the same patient, such as in an AF ablation.

Magnetic assisted navigation in electrophysiology and cardiac resynchronisation: a review.

Magnetic assisted navigation is a new innovation that may prove useful in catheter ablation of cardiac arrhythmias and cardiac resynchronization therapy. The ability to steer extremely floppy catheters and guidewires may allow for these to be positioned safely in previously inaccessible areas of the heart. The integration of other new technology, such as image integration and electroanatomic mapping systems, should advance our abilities further. Although studies have shown the technology to be feasible, with the advantage to the physician of decreased radiation exposure, studies need to be performed to show additional benefit over standard techniques.

Imaging of a coronary artery bypass graft during coronary sinus venography.

Retrograde coronary sinus perfusion to maintain viability during cardiac surgery means that a connection via the capillary system to the coronary arteries, and potentially bypass grafts, may be possible. Coronary sinus (CS) venography prior to resynchronisation therapy in this patient with previous bypass grafting was associated with visualisation of these grafts.

Magnetic navigation in AV nodal re-entrant tachycardia study: early results of ablation with one- and three-magnet catheters.

AIMS: Steering soft, flexible catheters using an external magnetic field could have advantages for heart catheterization, especially for therapy of tachyarrhythmias. Our aims were to assess the feasibility of magnetic navigation to Koch's triangle and reliable ablation of atrioventricular nodal re-entry tachycardia (AVNRT) with a magnetic catheter. METHODS AND RESULTS: Consecutive patients with AVNRT were mapped and ablated with a magnetically enabled catheter (Helios I or II), with, respectively, one and three magnets at the tip. The catheter was remotely advanced with the Cardiodrive system and orientated with the Navigant control system. After initial positioning with the external magnets, adjustment was made in 5 degrees steps. Success rates, procedure, and fluoroscopy times were analysed, and compared with a local contemporary series of conventional AVNRT ablations. Magnetic navigation was feasible in all 20 patients. Targets were easily reached. Catheters remained stable in position during accelerated junctional rhythms. Ablation was successful in 18/20 procedures (90%). No significant complications occurred. Median patient fluoroscopy time was 12 min, median physician fluoroscopy time was 4 min. Fluoroscopy times tended to be shorter than that in the conventionally treated group. Procedure duration decreased significantly over time, median procedure time was similar to that in the conventional group. CONCLUSION: AVNRT can be successfully mapped and ablated using magnetic navigation. A learning curve was evident, unrelated to catheter type, but to increasing operator experience. Physician radiation times were one-third of patient times. No complications occurred. Procedure time is comparable with that of conventional ablation.

Anticoagulation in atrial fibrillation and flutter.

Atrial fibrillation and atrial flutter are important risk factors for stroke. Based on a literature search, pathogenesis of thromboembolism, risk assessment in patients, efficacy of anticoagulation therapy and its alternatives are discussed. Special emphasis is put on issues like paroxysmal atrial fibrillation, atrial flutter and anticoagulation surrounding catheter ablation and cardioversion. A strategy for anticoagulation around the time of pulmonary vein ablation is suggested.

Pulmonary vein antrum isolation guided by phased-array intracardiac echocardiography: A third way to do PV ablation.

BACKGROUND: Pulmonary vein isolation (PVI) has emerged as an important strategy in the treatment of patients with atrial fibrillation (AF). The two most frequently used techniques are segmental PVI and left atrial circumferential ablation. AIM: To describe and discuss pulmonary vein antrum isolation guided by phased-array intracardiac echocardiography (ICE) as an alternative approach, and to present initial results. METHODS: Patients with symptomatic AF were included. The antra (the larger circumferential area around the PVs) were isolated guided by ICE. ICE was also used to titrate the ablation energy. RESULTS: 38 patients (3 with persistent AF) were included. Of the 35 patients with paroxysmal AF, 24 are without recurrences, and in six the incidence of paroxysms was significantly reduced after one procedure and a mean follow-up of 201 days. No major complications occurred. CONCLUSION: Pulmonary vein antrum isolation guided by ICE is a promising technique in AF ablation and has the potential to avoid severe complications.

The dioxin TCDD protects against aflatoxin-induced mutation in female rats, but not in male rats.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant and a potent carcinogen in laboratory rodents. When combined with other environmental toxins, it has been shown to increase the (geno)toxicity of some compounds. In this study, the effect of TCDD on the mutagenicity of aflatoxin-B1 (AFB1) was examined in the rat liver using a lacI transgenic rodent mutation assay. AFB1 induces GC-->TA transversions. Since TCDD is known to have a differential effect in male and female rodents, both sexes were studied. The data showed that a 6-week pre-exposure to TCDD had no significant effect on the frequency of aflatoxin-induced mutation in the liver of male rats. However, the TCDD treatment completely prevented the aflatoxin-induced transversion mutations in female animals.

Visualization of a coronary sinus valve using intracardiac echocardiography.

Cannulation of the coronary sinus (CS) is sometimes difficult due to the presence of anatomical anomalies. Fluoroscopy is of limited value in visualizing these variations. This case is the first to demonstrate how intracardiac echocardiography (ICE) allows visualization of a valve, which is one of the causes of problematic cannulation of the CS. Based on information obtained by ICE an appropriate catheter could be selected.

Electrical isolation of pulmonary veins using cryothermal energy: study design and initial results.

In the September 2003 issue of the Netherlands Heart Journal, the wrong figures where inserted in this article. The article is reprinted here with the correct figures. BACKGROUND: Atrial fibrillation (AF) is the most frequently encountered arrhythmia. Radiofrequency pulmonary vein (PV) ablation is promising for symptomatic paroxysmal AF, but is associated with a significant risk of PV stenosis. OBJECTIVES: To assess the efficacy of cryothermal PV ablation and the incidence of PV stenosis. METHODS: Highly symptomatic patients with paroxysmal or persistent AF were eligible for cryothermal ablation. Multislice spiral CT scans were performed before, and three months after ablation. AF burden was assessed using transtelephonic ECG recording and by telephone enquiry. RESULTS: An attempt was made to isolate 27 PVs in 15 patients. In total, 20 PVs could be isolated (74% acute success). No significant difference in PV diameter was seen before and after ablation. Five out of 12 patients with paroxysmal AF were completely without AF after one ablation procedure. An additional two patients reported a significant reduction in symptoms. In the three patients with persistent AF no improvement was reported. CONCLUSION: Cryothermal PV ablation was effective in isolation of the targeted PVs. It appears to be safe, as no PV stenosis was seen in this study three months after the ablation. Taking into account a learning curve, we consider the clinical results to be very promising.

Electrical isolation of pulmonary veins using cryothermal energy: study design and initial results.

BACKGROUND: Atrial fibrillation (AF) is the most frequently encountered arrhythmia. Radiofrequency pulmonary vein (PV) ablation is promising for symptomatic paroxysmal AF, but is associated with a significant risk of PV stenosis. OBJECTIVES: To assess the efficacy of cryothermal PV ablation and the incidence of PV stenosis. METHODS: Highly symptomatic patients with paroxysmal or persistent AF were eligible for cryothermal ablation. Multislice spiral CT scans were performed before, and three months after ablation. AF burden was assessed using transtelephonic ECG recording and by telephonic enquiry. RESULTS: An attempt was made to isolate 27 PVs in 15 patients. In total, 20 PVs could be isolated (74% acute success). No significant difference in PV diameter was seen before and after ablation. Five out of 12 patients with paroxysmal AF were completely without AF after one ablation procedure. An additional two patients reported a significant reduction in symptoms. In the three patients with persistent AF no improvement was reported. CONCLUSION: Cryothermal PV ablation was effective in isolation of the targeted PVs. It appears to be safe, as no PV stenosis was seen in this study three months after the ablation. Taking into account a learning curve, we consider the clinical results to be very promising.

Mutagenicity of TCDD in Big Blue transgenic rats.

The compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a significant environmental contaminant resulting from such industrial processes as pulp and paper production. TCDD is a suspected human carcinogen and its ability to induce cancer in laboratory rodents is well documented. Its mechanism of tumor initiation, however, is not well understood and in vitro mutagenicity studies have yielded inconsistent results. In this study, Big Blue lacI transgenic rats were used to assess the mutagenicity of TCDD in both male and female animals. After 6 weeks of exposure to 2 microg/kg TCDD neither an increase in mutation frequency nor any change in mutation spectrum was observed in either male or female animals.

Landau-level spectroscopy of a two-dimensional electron system by tunneling through a quantum dot.

A single InAs self-assembled quantum dot is incorporated in the barrier of a tunnel diode and used as a spectroscopic probe of an adjacent two-dimensional electron system from the Fermi energy to the subband edge. We obtain quantitative information about the energy dependence of the quasiparticle lifetime. For magnetic field B, applied parallel to the current, we observe peaks in the current-voltage characteristics I(V) corresponding to the formation of Landau levels. Close to filling factor nu=1 we observe directly the exchange enhancement of the Lande g factor.

Determinants of near fatality in acute severe asthma.

PURPOSE: The data extrapolated from cases of acute severe asthma that narrowly miss being fatal may prove valuable in the identification of the factors implicated in mortality. The purpose of this study was, therefore, to identify determinants of near fatality in patients with acute severe asthma. PATIENTS AND METHODS: We studied 81 patients with acute severe asthma in whom mechanical ventilation was required. Near fatality was defined as the occurrence of respiratory arrest and/or coma necessitating emergency tracheal intubation and resuscitation. In the cases that were not regarded as near fatal, tracheal intubation was performed electively because of deteriorating arterial blood gas values and/or the anticipation of exhaustion. Various continuous and categorical variables were compared in these two groups of patients. Patients with a hyperacute attack (period from onset of attack to mechanical ventilation less than 3 hours) were specifically sought and studied to determine the impact of such a course on near fatality. RESULTS: The "attack duration" (period from onset of attack to mechanical ventilation) was an important determinant of near fatality and of the subsequent clinical course. It was shorter in the group with a near-fatal episode (p < 0.03), and hyperacute attacks were uniformly near fatal. The attack duration correlated positively with the duration of the requirement for mechanical ventilation (p < 0.01). A longer attack duration was associated with an increased likelihood of the occurrence of major atelectasis (p < 0.01). There was no evidence of a relationship between near fatality and the side effects of bronchodilators as regards hypokalemia, arrhythmias, or cardiotoxicity. There was evidence of considerable under-treatment in the patient population as a whole, particularly in regard to the use of corticosteroids. CONCLUSIONS: A short attack duration is associated with an increased risk of near fatality in acute severe asthma. This is particularly evident in hyperacute attacks. Hyperacute attacks resolve rapidly once bronchodilator therapy has been instituted, suggesting that smooth muscle spasm is the predominant pathogenetic mechanism. The importance of routine anti-inflammatory therapy in mild to moderate asthma requires re-emphasis but, in addition, all patients should be provided with, and educated in the use of, bronchodilator rescue therapy, which should be available at all times. Despite current trends, the use of regular, prophylactic bronchodilator therapy in strict conjunction with anti-inflammatory agents may still be indicated. There is little evidence in the present data obtained from near-fatal cases to support the concept that cardiotoxicity related to bronchodilators contributes significantly to mortality from asthma.

Anterior extrathecal ependymoma with systemic metastases--a case report and review of the literature.

A case of anterior extrathecal ependymoma presenting with lung metastases is described. Computed tomography demonstrated the full extent of the mass which was not suspected on myelography.

Significance of tomographic signs in the diagnosis of bronchial carcinoma.

In a previous study the value of conventional tomography was assessed in the diagnosis of 100 potentially malignant opacities on the chest radiograph. To determine which of the radiological signs were most useful the radiologists reviewed 82 of the original 100 radiographs independently, searching for the presence or absence of 36 signs. The five commonest signs of bronchial carcinoma were a mass, coarse linear shadows contiguous to a mass, unilateral hilar enlargement, linear shadows from mass to periphery, and an irregular margin to a mass. The combination of either two or three of these signs was highly sensitive, 95% and 89% respectively, in detecting carcinoma. The most useful specific signs were lobulation of the mass and cavitation with thick or irregular walls.