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.

Surgery for atrial fibrillation: recent progress and future perspective.

Development and introduction of radiofrequency ablation devices allowed the maze procedures to be performed safely and easily, further enabling off-pump pulmonary vein isolation through a mini-thoracotomy or thoracoscope. The effects of the maze procedure include prevention of stroke and other complications related to atrial fibrillation, improved cardiac performance, and relief of symptoms. Indications for the maze procedure have been discussed on the basis of the evidence. Pulmonary vein isolation has been shown to be effective in most patients with paroxysmal atrial fibrillation and can be performed with endocardial catheter ablation and minimally invasive epicardial ablation. These two modalities should be compared in terms of the success rate, occurrence of cerebral microembolic signals, capability of additional lesions indicated for persistent or long-standing persistent atrial fibrillation, and closure of the left atrial appendage. Noncontinuous or nontransmural lines of conduction block as a result of incomplete ablation can result in recurrence of atrial fibrillation and induction of atrial tachycardia. Intraoperative verification of conduction block across the ablation lines is recommended to prevent these complications. Volume reduction of the enlarged left atrium or a boxlesion to isolate the entire posterior left atrium may be effective in patients with a dilated left atrium, but the potentially impaired atrial transport function should be considered. Mapping of active ganglionated plexi and their ablation may improve the outcome of the procedure, but the long-term effect on atrial fibrillation and autonomic nerve activities should be examined.

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.

Vagal denervation and reinnervation after ablation of ganglionated plexi.

OBJECTIVE: Surgical ablation of ganglionated plexi has been proposed to increase efficacy of surgery for atrial fibrillation. This experimental canine study examined electrophysiologic attenuation and recovery of atrial vagal effects after ganglionated plexi ablation alone or with standard surgical lesion sets for atrial fibrillation. METHODS: Dogs were divided into 3 groups: group 1 (n = 6) had focal ablation of the 4 major epicardial ganglionated plexi fat pads, group 2 (n = 6) had pulmonary vein isolation with ablation, and group 3 (n = 6) had posterior left atrial isolation with ablation. All fat pads were ablated. Sinus and atrioventricular interval changes during bilateral vagosympathetic trunk stimulation were examined before and both immediately and 4 weeks after ablation. Vagally induced effective refractory period changes and mean QRST area changes (index of local innervation) were examined in 5 atrial regions. RESULTS: Sinus and atrioventricular interval changes and heart rate variability decreased immediately after ablation, but only sinus interval changes were restored significantly after 4 weeks in all groups. Ablation-modified vagal effects on effective refractory period or QRST area changed heterogeneously in groups 1 and 2. In group 3, regional vagal effects were attenuated extensively postablation in both atria. Posterior left atrial isolation with ablation incrementally denervated the atria. In the long term, vagal stimulation increased QRST area changes relative to control values in all groups. Heart rate variability was also assessed. CONCLUSIONS: Ganglionated plexi ablation significantly reduced atrial vagal innervation. Restoration of vagal effects at 4 weeks suggests early atrial reinnervation.

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.

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.

Incisional atrial reentrant tachycardia: experimental study on the conduction property through the isthmus.

BACKGROUND: Incisional atrial reentrant tachycardia is a life-threatening tachyarrhythmia after surgery for congenital heart disease. Slow conduction through an isthmus between anatomical barriers, such as a right atriotomy or the sites for cannulation, has been shown to be a prerequisite for perpetuation of the incisional atrial reentrant tachycardia. However, the conduction property through the isthmus has not been examined in detail. METHODS: To examine the conduction property, 2 tandem incisions were made on the lateral right atrium with various distances (3 to 20 mm) between the incisions in 16 canines. Four weeks after the surgery, the lateral right atrium was mapped epicardially during pacing to examine the conduction property through the isthmus. The conduction property was characterized by approximated curves of the conduction velocity through the isthmus in accordance with the pacing cycle lengths. The atrial tissue at the isthmus was examined microscopically. RESULTS: The approximated curves of the conduction velocity were classified into 3 different types. Decremental conduction was observed only in the isthmi between 5 and 15 mm in width. A small amount of surviving myocardium between the scars formed the critical isthmus microscopically (decremental type). In the isthmi wider than 15 mm in width, slow conduction was not seen at any paced cycle length (nondecremental type). In the extremely narrow isthmi less than 5 mm in width, all of the atrial myocardium at the isthmus was replaced by fibrous tissue. Conduction was blocked at the isthmus and the activation detoured around the incisions (block type). There was a statistically significant difference in the approximated curves between the 3 different types of conduction properties (P <.01). CONCLUSION: The width of the isthmus determines the conduction property through the isthmus that contributes to the development of the incisional atrial reentrant tachycardia. Thus, the incisional atrial reentrant tachycardia may be preventable by leaving a sufficient amount of surviving myocardium between the incisions or by connecting the incisions by an ablative procedure.