Shunt and pace: a novel experimental model of atrial fibrillation with a volume-loaded left atrium.

BACKGROUND: Atrial fibrillation (AF) is frequently seen in patients with a volume-loaded left atrium (LA) such as mitral valve regurgitation (MR). Previous animal models have incomplete relevance to human AF associated with MR. METHODS: A novel experimental model with a combination of volume loading of LA by creating a shunt from the subclavian artery to pulmonary artery and electrical remodeling induced by continuous rapid LA pacing was designed and the electrophysiological effects were examined in 10 canines. Five weeks after the shunt surgery, the entire atrial epicardium was mapped during sustained AF with form-fitted electrode patches with 246 bipolar electrodes and a three-dimensional dynamic mapping system to characterize the induced AF. RESULTS: Three animals died of severe heart failure and pacing failure occurred in one. Remaining six animals were subjected to the analysis. The LA diameter increased progressively after the shunt surgery. Sustained AF was induced after 3 weeks of continuous rapid LA pacing in all animals. The activation maps revealed repetitive focal activations arising from the pulmonary veins, right or left atrial regions, and reentrant activations in the RA, which patterns of atrial activations are the same as those seen in human AF. CONCLUSION: The animal model with a combination of LA volume load and electrical remodeling was relevant to human AF associated with LA volume load. Studies using the present model may provide further knowledges of AF and may be useful in examining the effects of pharmacological and non-pharmacological therapies.

Inappropriate implantable cardioverter defibrillator shocks-incidence, effect, and implications for driver licensing.

PURPOSE: Patients with implantable cardioverter defibrillators (ICDs) have an ongoing risk of sudden incapacitation that may cause traffic accidents. However, there are limited data on the magnitude of this risk after inappropriate ICD therapies. We studied the rate of syncope associated with inappropriate ICD therapies to provide a scientific basis for formulating driving restrictions. METHODS: Inappropriate ICD therapy event data between 1997 and 2014 from 50 Japanese institutions were analyzed retrospectively. The annual risk of harm (RH) to others posed by a driver with an ICD was calculated for private driving habits. We used a commonly employed annual RH to others of 5 in 100,000 (0.005%) as an acceptable risk threshold. RESULTS: Of the 4089 patients, 772 inappropriate ICD therapies occurred in 417 patients (age 61 ± 15 years, 74% male, and 65% secondary prevention). Patients experiencing inappropriate therapies had a mean number of 1.8 ± 1.5 therapy episodes during a median follow-up period of 3.9 years. No significant differences were found in the age, sex, or number of inappropriate therapies between patients receiving ICDs for primary or secondary prevention. Only three patients (0.7%) experienced syncope associated with inappropriate therapies. The maximum annual RH to others after the first therapy in primary and secondary prevention patients was calculated to be 0.11 in 100,000 and 0.12 in 100,000, respectively. CONCLUSIONS: We found that the annual RH from driving was far below the commonly cited acceptable risk threshold. Our data provide useful information to supplement current recommendations on driving restrictions in ICD patients with private driving habits.

Map-guided surgery for atrial fibrillation.

BACKGROUND: Although current surgical procedures result in a high success rate for atrial fibrillation, they are not guided by electrophysiologic findings in individual patients and thus might include unnecessary incisions in some patients or be inappropriate for other patients. We sought to determine whether intraoperative mapping is beneficial for the surgical treatment of atrial fibrillation. METHODS: A 256-channel 3-dimensional dynamic mapping system with custom-made epicardial patch electrodes was used to examine the atrial activation during atrial fibrillation and to determine the optimal procedure in 37 patients with continuous and 9 patients with intermittent atrial fibrillation intraoperatively. RESULTS: Surgical intervention for atrial fibrillation was not indicated in 3 patients in whom the atrial electrograms had a low voltage over a broad area. Concurrent, multiple, and repetitive activations arising from the pulmonary veins or left atrial appendage were observed in all patients. A simple left atrial procedure consisting of pulmonary vein isolation and left atrial incisions without any right atrial incisions was performed in 8 patients in whom the right atrial activation was passive, and all (100%) were cured of atrial fibrillation. The radial procedure was performed in the remaining 35 patients, and 31 (89%) of the patients were cured of atrial fibrillation. In this subset of patients, 10 exhibited reentrant or focal activation in the posterior left atrium between the right and left pulmonary veins and required an additional linear ablation on the posterior left atrium. The total amount of postoperative bleeding after the simple left atrial procedure was significantly less than after the radial procedure (378 +/- 135 vs 711 +/- 364 mL, P = .03). The right and left atrial transport functions were well preserved after both the radial and simple left atrial procedures. CONCLUSION: Intraoperative mapping facilitates determining the optimal procedure for atrial fibrillation in each patient.

Concurrent multiple left atrial focal activations with fibrillatory conduction and right atrial focal or reentrant activation as the mechanism in atrial fibrillation.

OBJECTIVE: We examined the atrial activation during atrial fibrillation to validate the rationale behind simplified surgical procedures. METHODS: Intraoperative mapping of the entire atrial epicardium was performed in 21 patients with permanent atrial fibrillation and mitral valve disease using a 256-channel, 3-dimensional dynamic mapping system. RESULTS: Concurrent multiple repetitive activations arose from the posterior left atrium adjacent to the pulmonary veins or the left atrial appendage in all patients. The fastest activation propagated toward the right atrium conducting through Bachmann's bundle, leaving the other activations confined to a small atrial region. As the activation propagated toward the right atrium, there was a progressive conduction delay or block in the pathway. As a result, the activation in the right atrium desynchronized with the left atrial activation and became irregular and complex. The average cycle length measured at the right atrial appendage was significantly longer than that at the left atrial foci (206 +/- 32 milliseconds vs 175 +/- 23 milliseconds, P <.001). In addition to the passive activation, a focal activation and reentrant activation were also observed in the right atrium in 5 and 6 patients, respectively. The number of wave fronts in the right atrium was significantly greater than that in the left atrium (2.9 +/- 0.8 vs 0.6 +/- 0.7, P <.001). CONCLUSIONS: Multiple left atrial focal activations with fibrillatory conduction and right atrial focal or reentrant activations are the mechanism in permanent atrial fibrillation associated with mitral valve disease. Intraoperative mapping would facilitate the indication for simplified procedures confined to the left atrium or the pulmonary veins.

Optimal time of surgical treatment for Kawasaki coronary artery disease.

BACKGROUND: The major complication of Kawasaki coronary disease is myocardial infarction caused by thrombus formation inside the aneurysm or by organic obstructive lesion following the regression of aneurysm, while the indications for surgical therapy remain controversial. We have adopted coronary artery bypass grafting (CABG) even in young children for giant coronary aneurysms (more than 8 mm diameter) with or without a stenotic region when myocardial ischemia is detected. We hypothesized that a shorter time-period from diagnosis of acute Kawasaki disease (KD) to CABG would lead to better postoperative results. To elucidate the validity of our strategy, we evaluated preoperative patient characteristics and long-term outcome. METHODS: Twenty-one patients (mean age: 12.0 years old) with Kawasaki coronary disease had undergone CABG during the last 12 years. The mean age at the time of acute KD was 2.7 years and the mean time range from diagnosis of acute KD to CABG was 8.1 years. The incidence of preoperative reduced ventricular function was 10 per 21 patients (47.6%). A multivariate logistic regression analysis using patient characteristics showed that the time range from acute KD to CABG was the only predictor for ventricular functional deterioration (p=0.03, odds ratio 1.55. 95%CI: 1.033 approximately 2.325). Based on these results, we divided the patients into two groups of short time range (mean: 3.7 years; group S) and long time range (mean: 13.9 years; group L). RESULTS: Preoperative left ventricular functional deterioration was recognized more frequently in group L (9/9, 100%) than in group S (1/12, 8.3%)(p<0.01). Myocardial infarction was documented significantly higher in the group L (6/9, 66.7%) than group S (1/12, 8.3%)(p=0.04). There was no surgical mortality in either group. The arterial grafts demonstrated good potential for growth and graft patency was 96.9%. Moreover, seven of the giant aneurysms proximal to the graft anastomosis showed complete thrombotic occlusion after CABG without development of myocardial infarction. The cardiac events free rate of group L and group S was 66.7% and 100%, respectively, during the postoperative follow up periods of 5.5+/-1.1 years (group L) and 4.7+/-1.1 years (group S). CONCLUSIONS: We successfully applied CABG for Kawasaki coronary disease. Based on our experience, a short interval after acute KD appears to be ideal for surgical treatment of Kawasaki coronary disease.

Double potential mapping: a novel technique for locating the site of incomplete ablation.

OBJECTIVE: Double potential mapping using bipolar electrodes that straddle the ablation line should identify the site of incomplete ablation as a conduction gap without constructing the activation maps. METHODS: Bipolar electrograms were recorded during pacing using 11 custom-made bipolar electrodes straddling the ablation line created by a bipolar radiofrequency ablation device on the lateral right atrium in seven canines. A linear ablation was made with an ablation device, of which one jaw was inserted into the atrium through a purse-string suture. A 3-mm-wide tape was placed on both jaws 10 mm from the tip of the ablation electrode to intentionally create an incomplete ablation lesion. The activation times at each dipole across the ablation line were defined as the times of the maximum positive and negative derivatives of the double potentials, and the site of conduction gap was determined as the site of the earliest activation across the linear ablation. The lateral right atrium was mapped simultaneously with 45 different bipolar electrodes to construct the activation maps and the earliest activation site across the ablation line was determined. RESULTS: The double potential mapping located the conduction gap on a real-time basis without displaying any maps. There was no significant change in the accuracy between the different times after ablation and different pacing cycle lengths. CONCLUSIONS: Double potential mapping locates the conduction gap on a real-time basis and would be useful in beating-heart epicardial ablation in off-pump setting.

Intraoperative electroanatomic mapping.

PURPOSE: An electroanatomic mapping system using an electromagnetic navigation technology constructs a 3-dimensional structure of the heart with high geometric accuracy of the data that provides a precise localization of the substrates of arrhythmias. The system was tested for the feasibility and efficacy in intraoperative mapping. DESCRIPTION: The strength of the magnetic field is measured by a location sensor with three different frequencies generated by a location pad placed beneath the operating table, and the spatial location of the sensor is determined. By roving the catheter on the heart while the local electrogram is recorded simultaneously, the 3-dimensional figure of the heart is reconstructed and an activation or voltage map is generated. EVALUATION: The system was used in 19 patients with ventricular tachycardia or other arrhythmias. The focus or reentrant circuit of the tachycardia was precisely located and a map-guided procedure was successfully performed in all patients. Cardiopulmonary bypass allowed for the tachycardias to be mapped without any hemodynamic compromise. CONCLUSIONS: Intraoperative mapping using the electroanatomic mapping system enables a precise localization of the tachycardia substrate.

Interatrial electrical connections: the precise location and preferential conduction.

BACKGROUND: The atria are assumed to be connected electrically to each other at the level of the Bachmann's bundle, coronary sinus (CS) musculature, and interatrial septum, and these connections may have an important role in the interatrial conduction and perpetuation of various types of atrial tachyarrhythmias. However, the number, location, and preferential connections of the interatrial conduction related to the site of activation have not been examined yet. METHODS: The endocardium of both atria and the CS were mapped during continuous pacing from the left superior and inferior pulmonary veins, right pulmonary veins, upper and lower right atrium, or right atrial septum at various paced cycle lengths in 14 canines. The electrograms were recorded by custom-made form-fitted electrodes mounted on a specially designed device that allowed the septal aspects of the electrode forms to be spatially fixed to each other accurately. RESULTS: Four distinct interatrial electrical connections were identified at the Bachmann's bundle, CS, and antero-superior and postero-inferior septa. Decremental conduction was not seen in any of the connections. Bachmann's bundle was the most preferential connection during pacing from any epicardial site. The transseptal connections were evident only during pacing from the interatrial septum. The preference among the four connections was determined by the site of stimulation and the propagation of the activation related to the myocardial architecture. CONCLUSION: These unique preferential connections may play a significant role in the interatrial conduction and perpetuation of atrial tachyarrhythmias.