Percutaneous Catheter Ablation at the Mitral Annulus in Canines Using a Bipolar Epicardial-Endocardial Electrode Configuration

For potential application in ablating left free-wall accessory AV pathways with direct current shocks, a new epicardial-endocardial electrode configuration, designed to focus the current field across the mitral annulus, was tested in dogs. A catheter electrode in (he coronary sinus (epicardial electrode) was used as the cathode, and a catheter electrode in the left ventricle (endocardial electrode) placed beneath the mitral valve, high against the mitral annulus and directly across from the epicardial electrode formed the anode. Two shocks, each of 30, 40, or 50 joules (J) were delivered in nine, three, and four dogs, respectively. The first shock was applied to the anterior or lateral wail and the second shock to the posterior wall, except in one dog which received one anterior and one lateral shock. Two dogs receiving 50] shocks died acutely, one due to rupture of the coronary sinus and cardiac tamponade and the other had unexplained electromechanical dissociation. The remaining 14 dogs tolerated the two shocks well and were sacrificed 3–5 days later for pathological examination of the heart. Shocks in the anterior and lateral regions produced atrial necrosis (height 1.5–11 mm, width 1.5–12 mm and depth 1–3 mm) in 10 of 14 dogs and ventricular necrosis (height 4–27 mm, width 4–33 mm, and depth 5–14 mm) in all 14 dogs. Ideal lesions with atrial necrosis extending down to the annulus and ventricular necrosis extending to the epicardial aspect of the ventricular crest occurred in five dogs in which the endocardial electrode was positioned high against the annulus. In the other nine dogs, the endocardial electrode was located 6–18 mm below the annulus, as estimated by the center of ventricular necrosis. In these dogs, the ventricular lesions did not extend to the epicardial aspect of the crest and, in four dogs, no atrial necrosis was found. Shocks delivered to the posterior wall produced no atrial or ventricular necrosis except in one dog receiving a 50 J shock. It is concluded that, using the epicardial-endocardial electrode configuration with the LV catheter positioned high against the annulus, shocks of less than 50 J in dogs safely produce atrial and ventricular necrosis adjacent to the mitral annulus in the anterior and lateral regions but not in the posterior regions. Similar lesions in man may be capable of interrupting left anterior and lateral accessory AV pathways.     

Cystic fibrosis—immunological reactions to A. Fumigatus and common allergens

Immunological studies of forty-three patients with cystic fibrosis showed that positive prick tests to at least one common allergen were obtained in 70%, to multiple allergens in 28% and to A. fumigatus in 50%. Specific IgE antibodies against these allergens were found in the appropriate subjects. In spite of this evidence of type 1, IgE, sen-sitization none of the patients had a history of infantile eczema. Intracutaneous tests with A. fumigatus extract gave types 1 and 3 reactions in sixteen patients (37%), only seven of whom were among the sixteen (37%) who gave positive precipitin tests. Raised levels of total serum IgG and IgA were found as compared with healthy controls and asthmatic subjects. No differences were found in total serum IgM and IgD levels. The high incidence of allergy to A. fumigatus in cystic fibrosis is confirmed.     

Bystander Accessory Pathway During AV Node Re-entrant Tachycardia

Between 1970 and July 1980, wide QRS tachycardia due to re-entryconfined to the AV node with bystander involvement of an accessory atrioventricular pathway (AAV) was documented in three of 290 patients with the Wolff-Parkinson-White syndrome studied at Duke Medical Center. In each of the patients, at least one transition between wide and narrow QRS morphology was recorded without change in either the cycle length of tachycardia or the atrial activation sequence. Two of the three patients had a single left-sided AAV (lateral, posterolateral) showing antegrade conduction only. The third patient had two right-sided AAVs (free wall, septal), each capable of bidirectional conduction. Initiation and termination of repetitive concealed conduction into the ventricular insert of an AAV appeared to be one mechanism determining bystander AAV participation. Documentation of the retrograde sequence of atrial activation during tachycardia, and examination of the effects of interpolated premature depolarizations from both the ventricle and midline atrium are the most helpful features in resolving the differential diagnosis of wide QRS tachycardia in patients with W-P-W syndrome.