By S. Cronos. Marywood University. 2019.

This may be related to the high incidence of dual A-V nodal pathways observed in such patients buy crestor american express. Although this is most common in the Wolff–Parkinson–White syndrome during circus movement tachycardia (see Chapter 10) buy crestor discount, we have seen atrial flutter and/or fibrillation develop in the P order discount crestor on line. Upon cessation of pacing there is a V-A-A-V response with the appearance of a right atrial tachycardia. Ap blocks below the His bundle, and it simultaneously gives rise to a sinus node echo (fourth A). This rules out atrial tachycardia and confirms the presence of an innocent bystander nodoventricular bypass tract. P waves that are inverted in the inferior leads can represent reentry using the A-V junction (i. As shown in the ladder diagram on the right, delay below the circuit (in this case the lower part of the A-V node) results in retrograde activation of the atrium prior to the ventricle. The R-P and P-R patterns and their relative incidence are summarized in Figures 8-158 and 8-159. The manner in which such sequential studies are performed is described in Chapter 12. Obviously, studies are required to localize the origin of the tachycardia for catheter ablation as well as to determine the tachycardia-terminating stimulation mode for antitachycardia pacing. The response to overdrive pacing of triggered atrial and ventricular arrhythmias in the canine heart. Characteristics of initiation and termination of catecholamine-induced triggered activity in atrial fibers of the coronary sinus. Transient entrainment and interruption of the atrioventricular bypass pathway type of paroxysmal atrial tachycardia. Demonstration of an excitable gap in the common form of atrioventricular nodal reentrant tachycardia. The resetting response of ventricular tachycardia to single and double extrastimuli: implications for an excitable gap. Entrainment of ventricular tachycardia: explanation for surface electrocardiographic phenomena by analysis of electrograms recorded within the tachycardia circuit. Resetting response patterns during sustained ventricular tachycardia: relationship to the excitable gap. On circulating excitations in heart muscles and their possible relations to tachycardia and fibrillation. Multiple pathways of conduction and reciprocal rhythm with interpolated ventricular premature systoles. Ventricular echo beats in the human heart elicited by induced ventricular premature beats. An unusual variety of atrioventricular nodal re-entry due to retrograde dual atrioventricular nodal pathways. Initiation of two distinct forms of atrioventricular nodal reentrant tachycardia during programmed ventricular stimulation in man. Electrotonically mediated delayed conduction and reentry in relation to “slow responses” in mammalian ventricular conducting tissue. Extracellular potentials related to intracellular action potentials during impulse conduction in anisotropic canine cardiac muscle. Influences of anisotropic tissue structure on reentrant circuits in the epicardial border zone of subacute canine infarcts. Anisotropic conduction and functional dissociation of ischemic tissue during reentrant ventricular tachycardia in canine myocardial infarction. Demonstration of dual A-V nodal pathways in patients with paroxysmal supraventricular tachycardia. Demonstration of dual atrioventricular nodal pathways utilizing a ventricular extrastimulus in patients with atrioventricular nodal re-entrant paroxysmal supraventricular tachycardia. Double atrial responses to a single ventricular impulse due to simultaneous conduction via two retrograde pathways. Morphology of the cardiac conduction system in patients with electrophysiologically proven dual atrioventricular nodal pathways. Treatment of supraventricular tachycardia due to atrioventricular nodal reentry, by radiofrequency catheter ablation of slow-pathway conduction. Elimination of atrioventricular nodal reentrant tachycardia using discrete slow potentials to guide application of radiofrequency energy. Clinical, electrocardiographic and electrophysiologic observations in patients with paroxysmal supraventricular tachycardia. The essential role of atrioventricular conduction delay in the initiation of paroxysmal supraventricular tachycardia. Comparison of right and left atrial stimulation in demonstration of dual atrioventricular nodal pathways and induction of intranodal reentry. Effect of atrial stimulation site on the electrophysiological properties of the atrioventricular node in man. Effects of the pacing site on A-H conduction and refractoriness in patients with short P-R intervals. Multiple anterograde atrioventricular node pathways in patients with atrioventricular node reentrant tachycardia. The effects of propranolol on induction of A-V nodal reentrant paroxysmal tachycardia. Concealed bypasses of the atrioventricular mode in patients with paroxysmal supraventricular tachycardia revealed by intracardiac electrical stimulation and verapamil. Effect of digitalis in patients with paroxysmal atrioventricular nodal tachycardia. Antegrade and retrograde conduction characteristics in three patterns of paroxysmal atrioventricular junctional reentrant tachycardia. Observations in patients with supraventricular tachycardia having a P-R interval shorter than the R-P interval: differentiation between atrial tachycardia and reciprocating atrioventricular tachycardia using an accessory pathway with long conduction times.

These are truly septal and may be approached from either the right side or on rare occasions from the left side and are associated with a 5% incidence of heart block if the catheter is positioned in the triangle of Koch discount crestor 10 mg free shipping. Such bypass tracts should be ablated with the catheter on the tricuspid annulus or on the ventricular side of the tricuspid annulus to decrease the incidence of A-V block generic 5mg crestor overnight delivery. Safety will further be enhanced by using the lowest power required to get an impedance drop of 10 Ω purchase cheap crestor line. They often exhibit a bypass tract potential and/or early activation at a site without a His bundle deflection (Fig. The para-Hisian pathways, by definition, are recorded with simultaneous His bundle activity from which it needs to be distinguished. In this particular instance the ablation catheter was positioned so that the tip produced pressure perpendicularly to the His bundle region. This led to a rather slowly inscribed ventricular depolarization consistent with the onset of ventricular activity as well as a slowly inscribed “inferior” His bundle deflection, which times identically with the discrete bipolar deflection on the His bundle catheter. With the loss of pre-excitation there is loss of the negative deflection between the A and the broad H and disappearance of the delta wave. These fibers are very superficial and protected by a fibrous sheath, so with use of low power and temperatures not exceeding 52°C the risk of permanent heart block is less than 1%. Rapid ventricular pacing is often necessary to discern the onset of atrial activity (Fig. A left lateral bypass tract is present with a long conduction time, which was associated with a local A-V interval of 90 msec. No overt pre-excitation is present because the area of the ventricle that is “pre-excited” occurs after the onset of normal activation. A and B: Ventricular pre-excitation is recorded from a unipolar rove electrode as an intrinsicoid deflection 25 msec before the delta wave during sinus rhythm. Anteroseptal bypass tracts are characterized by the presence of a bypass tract potential and the absence of a His bundle potential in the apex of the triangle of Koch. The most difficult for me have been the right free wall pathways, particularly if approached from the inferior vena cava. This is due to both poor contact and the fact that these bypass tracts are often off the annulus, crossing through a “folded” right atrium over the ventricle. Initial attempts at ablation from the right side produced transient success but the arrhythmia recurred 6 hours later. On the following day a second ablation was successful using the retrograde aortic approach. The third was right free wall pathway that disappeared in 10 seconds after the onset of ablation, only to recover 2 weeks later; repeat ablation resulted in subsequent durable success. The fourth was in right-sided accessory pathway in a patient with Ebstein anomaly. Bypass tract conduction blocked in less than 10 seconds with ablation, but recurred within 2 weeks; a recurrent ablation attempt resulted in the same sequence of events. This tracing compares the electrograms recorded in the His bundle recording and the ablation catheter before (left) and after (right) catheter pressure caused temporary bypass tract block. This is validated with loss of pre-excitation demonstrating consistent positioning of the His bundle potential associated with the slowly inscribed second potential in the first complex and loss of the pre-excitation in the first negative potential in the first complex. Right bundle branch block is present, which facilitates the observation of a broad slowly inscribed His deflection from the ventricular myocardium. In general, the greater the experience of the operator, the higher the success rate and the fewer lesions used. While success rates in many laboratories exceed 95%, the use of multisite “insurance lesions” to achieve these results should be discouraged. The use of two or less sites should be a goal and requires attention to careful mapping to achieve. We have had only two recurrences, both in two patients in whom we failed initially. The other gentleman is currently being treated for active hepatic pulmonary and renal tuberculosis and his tachycardias are readily controlled by antiarrhythmic drugs at this time. Ablation of Pre-excitation Variants The two major variants of pre-excitation that lend themselves to catheter ablation are slowly conducting concealed bypass tracts and atriofascicular bypass tracts. The recognition, diagnosis, and characteristics of both these variants are detailed in Chapter 10. The permanent form of reciprocating tachycardia is generally caused by a slowly conducting bypass tract, which is commonly in the right inferior paraseptal location. In my experience, in almost half (45%) of the patients in whom we have diagnosed a slowly conducting bypass tract, the bypass tract was located in the left inferior or left posterior (free wall, greater than 4 cm inside the coronary sinus). The remaining half were located between the base of the pyramidal space, which is formed by the points of contact of the pericardial reflection with the posterior right and left atrium (right and left inferior paraseptal). An example of a slowly conducting bypass tract inserting 4 cm inside the coronary sinus is shown in Figure 13-38. In most series the majority of these slowly conducting bypass tracts occur around the region of the os of P. The atrial insertion sites of these slowly conducting bypass tracts usually demonstrate multicomponent electrograms. Successful ablation of these bypass tracts exceeds 90% but often requires lesions delivered in the coronary sinus. In (A), circus movement tachycardia in a slowly conducting bypass tract is present. Atrial activation is color coded in the electroanatomical map during circus movement tachycardia. The His bundle is marked by the orange circle and the ablation sites adjacent to it are shown. The earliest atrial activation is shown in dark red with subsequent activation in lighter red, orange, yellow, green, etc. Atriofascicular bypass tracts are the other variant of pre-excitation in which ablative techniques have been useful. Although it was originally thought that these pathways were nodofascicular, it is clear that the vast majority of these pathways originate in the anterolateral right atrial tricuspid annulus and act as a secondary conducting system inserting into the distal right bundle branch. While insertion into the myocardium adjacent to the right bundle branch is possible in some cases, the presence of a retrograde V-H interval of less than 25 msec suggests a direct insertion into the right bundle branch itself. Direct recordings of this pathway at the anterolateral tricuspid annulus look like a typical A-V junctional recording with an atrial deflection, a sharp spike, and a ventricular deflection.

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Duration Most laboratories consider a tachycardia sustained if it lasts ≥30 seconds purchase crestor 10 mg overnight delivery. Repetitive polymorphic responses are also very common (up to 50%) discount 20mg crestor, particularly when multiple (≥3) extrastimuli are used with extremely short coupling intervals (<180 msec) generic 20mg crestor amex. The clinical significance of induced nonsustained polymorphic tachycardia is questionable and requires further evaluation to determine its relevance (to be discussed in subsequent paragraphs). They reported good sensitivity and specificity, but I have not found it significantly better than V1–2 criteria. Furthermore, A-V dissociation can be seen with supraventricular rhythms, fusion complexes can result from two ventricular ectopic foci, and morphologic and/or axis characteristics established for patients with normal P. In the absence of pre-excitation a supraventricular impulse must pass through the His bundle and the specialized ventricular conducting system before initiating depolarization of the ventricles. This may result because no engagement of the His–Purkinje system by the ventricular impulse occurs (probably uncommon), or because retrograde His bundle activation occurs during ventricular activation and is obscured by the large ventricular deflection in the His bundle recording. His deflections can usually be observed if attention is given to catheter position. One may identify His bundle activity before ventricular activation (in this instance, the H-V interval is shorter than normal; e. If His bundle deflections are not seen, one must differentiate the absence of retrograde activation of the His– Purkinje P. This can be fortuitously observed if a sinus impulse conducts antegradely to the His bundle producing a clear His deflection. In these instances, linking of the His bundle potential to atrial activation proves that they are due to antegrade depolarization and are unrelated to the tachycardia. Retrograde block in the A-V node is present because atrial activation is dissociated from the tachycardia. It is often difficult to determine whether the recorded His deflection is antegrade or retrograde—or for that matter whether an apparent His bundle deflection is really a right bundle branch potential. Two techniques that may be used to clarify the situation are (a) recording right and left bundle branch potentials to demonstrate that their activation begins before His bundle activation and (b) His bundle pacing producing a longer H-V interval than the one noted during the tachycardia. Both of these are extremely difficult to do but can help define the mechanism of His bundle activation and the tachycardia origin. The simplest methods for verifying proper catheter position include the following: (a) the immediate appearance of His bundle deflections on termination of the tachycardia, or conversely, disappearance of the His bundle deflection on initiation of the tachycardia, without catheter manipulation; (b) spontaneously occurring or induced supraventricular capture of the His–Purkinje system (with or without ventricular capture) during the tachycardia with the sudden appearance of His bundle deflections; and (c) in the presence of supraventricular capture, H-V intervals comparable to those during sinus rhythm (Figs. We have found that the use of more closely spaced bipolar electrodes (l to 5 mm apart) facilitate identification of His bundle activity when it occurs within the ventricular electrogram. The second atrial impulse (A) conducts through the His bundle but fails to alter the tachycardia. The first and third sinus complexes block in the A-V node due to retrograde concealment. Two complexes later, another supraventricular fusion is observed, again without influencing the tachycardia. This demonstrates lack of requirement of the His bundle for perpetuation of the tachycardia. If His deflections are not spontaneously observed during the tachycardia, because of either poor position or obscuration of the His deflection by the ventricular electrogram, rapid atrial pacing can be used to clarify the issue in some cases. Thus, knowledge of A-V conduction during sinus rhythm may be necessary to define what is a “normal” H-V interval during the tachycardia. Some investigators , suggest that the site of origin of such a tachycardia is within the His–Purkinje system. As stated earlier, pre-excited tachycardia using either an A-V or nodoventricular bypass tract must be excluded (see Chapter 10). It is not rare for a tachycardia to have a V-H interval less than the antegrade H-V interval (Fig. Retrograde conduction time over the His–Purkinje system is actually much greater than the “V-H” observed during the tachycardia. Depending on the relative conduction time up the His–Purkinje system and through slowly conducting P. Atrial pacing is begun (arrow) at a cycle length of 480 msec, which is gradually reduced to 400 msec. As the atrial-paced cycle length decreases, a greater degree of ventricular activation is produced via the normal conducting system. The His deflection typically occurs before the right bundle deflection with an H-V interval approximating the H-V interval during sinus rhythm. Theoretically, if there is prolonged retrograde conduction over the His–Purkinje system, producing a markedly delayed His deflection (very long V-H), the “in parallel” activation of the His bundle would appear as a “normal” H-V interval. In this case, one must demonstrate that the His deflection is not a requisite for subsequent ventricular activation and thus is not a reflection of bundle branch reentry. Certain criteria are necessary for the diagnosis of bundle branch reentry, all of which provide P. The mechanisms of bundle branch reentry and its variants are discussed in greater detail later in this chapter. B: The schema shows that propagation of the impulse from the reentrant circuit to the His–Purkinje system is more rapid than that to the remainder of the myocardium, resulting in a short V-H interval. In this instance, conduction to the His–Purkinje was far more rapid than that to the ventricular myocardium, resulting in early His–Purkinje activation. These differences make it mandatory that these arrhythmias not be lumped together in terms of response to stimulation, effects of pharmacologic therapy, effectiveness of ablation, and clinical outcome. Anatomic Substrate The most common anatomic substrate for all these arrhythmias is chronic coronary artery disease, usually associated with prior infarction. Arrhythmias that are due to coronary artery disease are the only ones for which we have a reasonable understanding of the pathophysiologic substrate required for their genesis. Although sustained uniform monomorphic tachycardia may occur in the presence of either hypertrophic or idiopathic dilated cardiomyopathy, or even in patients with normal hearts, it is relatively uncommon. In these instances, the pathophysiologic basis for the arrhythmia is not well understood although patchy or segmental fibrosis is a common denominator. Arrhythmogenic right ventricular dysplasia has similar pathology as infarction, but it starts on the epicardium and additionally has fatty infiltration of the myocardium. This may occur because in most cases there is patchy fibrosis instead of the large areas of contiguous scar seen in infarction. Regardless of the underlying cardiac pathophysiology, sustained monomorphic tachycardia can be studied electrophysiologically such that interpretation of the mechanism and development of therapy is possible.

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The greater omentum can be used to cover the raw surface of the liver at the end of the procedure order crestor 5 mg. After left lateral segmentectomy purchase generic crestor on-line, the procedure concludes with the placement of two suction drains near the edge of the wound to collect any minor persistent oozing of blood or bile and to prevent hematomas generic 20 mg crestor fast delivery. Smaller resections such as limited segmentectomies are done in the same way, with the same concern for hemostasis and control of the biliary ducts. Vascular white staples can easily control the hemostasis of small pedicles but it is advisable to start the resection by scar- ring the capsule with a hook. In general, as demonstrated in gynecological series, the associated risk in laparoscopic surgery is minimal. The risk is, however, not insignifcant during surgery of solid organs such as the liver and spleen because they are linked directly to the inferior vena cava and to the heart. The effects of emboli are sometimes initially detected only by the recovery room staff, who must be made aware of this possible complication. Right Hepatectomy This is the most advanced laparoscopic liver resection, and perhaps the most complex laparoscopic procedure, that should only be performed by experienced laparoscopic liver surgeons. All instruments are used as described above, including the harmonic shears and the cutters with vascular loads. A Pringle maneuver is always performed frst, and the operation follows the rules of open liver surgery. A camera; B surgeon’s right hand for harmonic shears; C second surgeon’s left hand; D second surgeon’s right hand; E fan or suction irrigation device. Minor hemorrhage can be con- Prevention of trolled with unipolar or bipolar atraumatic forceps. With more serious arterial bleeding where there is clearly spurting of blood, it is Complications necessary to grasp the artery with the atraumatic forceps and apply a clip or ligature. The management of venous bleeding in hepatic surgery tends to be more compli- cated, as there is often constant oozing, making hemostasis extremely diffcult. Often tempo- rary compression using laparoscopic 2 × 2 gauze will stabilize the situation. It is also possible to introduce larger 4 × 4 gauze which should be attached to a suture to identify it laparoscopically, and a clip should be placed on the gauze to make it radiopaque. If the bleeding originates from a small lacerated vein, it can generally be controlled with cau- tery, clips, or the fat blade of harmonic scissors. If the venous injury is more extensive, such as to the hepatic vein or a branch of the portal vein, one should not hesitate to con- vert and perform a limited subcostal incision which will then allow precise action and enable the operation to be concluded safely. It should be stressed that conversion is not an admission of failure, but sound surgical judgment. Patient Selection 63 Control of biliary leaks by the use of clips, is generally easy because the biliary drainage can be seen clearly under the magnifcation provided by the laparoscope. Finally, division of these vessels must take place only after their proper control with elec- trocautery, clips, or ligatures. Surgery 146(4):817–823 Baldini E, Gugenheim J, Ouzan D, Katkhouda N, Mouiel J (1999) Orthotopic liver trans- plantation with or without peritoneal drainage: a comparative study. Transplant Proc 31:556–557 Buscarini L, Rossi S, Fornari F, DiStasi M, Buscarini E (1995) Laparoscopic ablation of liver adenoma by radiofrequency electrocautery. Gastrointest Endosc 41(1):68–70 Castaing D, Vibert E, Ricca L, Azoulay D, Adam R, Gayet B (2009) Oncologic results of laparoscopic versus open hepatectomy for colorectal liver metastases in two special- ized centers. Ann Surg 250(5):856–860 Croce E, Azzola M, Russo R, Golia M, Angelini S, Olmi S (1994) Laparoscopic liver tumowur resection with the argon beam. Surg Laparosc Endosc 5(4):277–280 Edye M, Salky B (1994) Laparoscopic approaches to hepatobiliary surgery. Sem Liver Dis 14(2):126–134 Eubanks S (1994) The role of laparoscopy in diagnosis and treatment of primary or met- astatic liver cancer. Semin Surg Oncol 10(6):404–410 Fabiani P, Katkhouda N, Gugenheim J, Mouiel J (1991a) Laparoscopic treatment of biliary cysts. Br J Surg 84(3):321–322 Fabiani P, Katkhouda N, Chazal M, Gugenheim J, Mouiel J (1991b) Fenestration of biliary cysts under videocoelioscopy. La Lettre Chirurgicale 10:105 Ferzli S, David A, Kiel T (1995) Laparoscopic resection of a large hepatic tumor. World J Surg 20(5):556–561 Gugenheim J, Mazza D, Katkhouda N, Goubaux B, Mouiel J (1996) Laparoscopic resection of solid liver tumors. Br J Surg 83:334–335 Guibert L, Gayral F (1995) Laparoscopic pericystectomy of a liver hydatid cyst. Surg Endosc 9(4):442–443 Hashizume M, Takenaka K, Yanaga K et al (1995) Laparoscopic hepatic resection for hepatocellular carcinoma. Surg Endosc 9(12):1289–1291 Kabbej M, Sauvanet A, Chauveau D, Farges O, Belghiti J (1996) Laparoscopic fenestration in polycystic liver disease. Br J Surg 83(12):1697–1701 Katkhouda N, Mavor E, Mason R, Mouiel J (2000) Laparoscopic management of benign liver cysts. J Hepatobiliary Pancreatic Surg 7:212–217 Katkhouda N, Mavor E (2000) Laparoscopic management of benign liver disease. Surg Clin North Am 80:1203–1211 Katkhouda N, Hurwitz M, Gugenheim J, Mouiel J (1999a) Laparoscopic management of enign solid and cystic lesions of the liver. Ann Surg 4:460–466 Selected Further Reading 65 Katkhouda N, Heimbucher J, Mills S, Mouiel J (1994) Management of problems in lapa- roscopic surgery of the biliary tract. Ann Chi Gynaecol 83:93–99 Katkhouda N (2008) Application of fbrin glue after hepatectomy might still be justifed. Lasers Med Sci 38:55–62 Katkhouda N, Mouiel J (1992) Laser resection of a liver hydatid cyst by videocoelioscopy. Br J Surg 79:560–561 Katkhouda N, Fabiani P, Le Goff P, Mouiel J (1989a) Hepatic parameters as indicators of common bile duct stones. Lettre Chir 72:12–17 Katkhouda N, Tricarico A, Castillo L, Bertrandy M, Mouiel J (1989) Complications of external bile drainage in the surgery of extra-hepatic lithiasis. Surg Endosc 8(9):1105–1107 Marks J, Mouiel J, Katkhouda N, Gugenhein J, Fabani P (1998) Laparoscopic liver surgery.

Some ablation catheters have a cooled tip discount 10mg crestor with mastercard, one through which saline is infused to allow for enhanced tissue heating without superficial charring (Biosense Webster and St Jude) or internal cooling (Chili; Boston Scientific) (Fig purchase crestor 10mg otc. Catheters that are capable of producing linear radiofrequency lesions are being developed to treat atrial fibrillation by compartmentalizing the atria purchase crestor line, but currently the ability of these catheters to produce transmural linear lesions that have clinical benefit and are safe is not proven. Catheters that deliver microwave, laser, cryothermal, or pulsed-ultrasound energy to destroy tissue are currently under active investigation. For this latter use a cryoballoon catheter has been developed (Arctic; Medtronic [Fig. In the second category are included standard catheters with up to 24 poles that can be deflected to map large and/or specific areas of the atrium (e. More recently Rhythmia Medical (Boston Scientific) has developed a 64 pole roving catheter (Fig. This mapping (minibasket) catheter has an 8 F bidirectional deflectable shaft and a basket electrode array (usual mapping diameter 18 mm) with eight 2 splines, each spline containing eight small (0. Mapping can be performed with the basket in variable degrees of deployment (diameter ranging 3 to 22 mm). The location of each of the 64 electrodes is identified by a combination of a magnetic sensor in the distal region of the catheter and impedance sensing on each of the 64 basket electrodes. The location of each basket electrode is obtained whether the basket is fully or only partially deployed. Heparinized saline (1 U/mL) is infused through the central lumen of the catheter shaft at 1 mL/min, emerging at the proximal end of the basket to prevent thrombus. Saline spray through the catheter tip is used to maintain “low” tip temperature to prevent charring while at the same time increasing lesion size. Two sizes of balloon catheters (24 and 28 cm) are available to deliver cryothermal lesions to the pulmonary vein ostia. A flexible lasso insets thru a lumen to identify the osyia and record pulmonary vein potentials. Deflectable catheters with 10 to 24 poles that have bidirectional curves are useful for recording from the entire coronary sinus or the anterolateral right atrium along the tricuspid annulus. While standard 10 to 20 pole woven Dacron or deflectable catheters can be used to record along the anterolateral tricuspid annulus, a “halo” catheter has been specifically designed to record around the tricuspid annulus. This lasso catheter is used to record from and pace inside the pulmonary vein ostia before and after pulmonary vein isolation procedures (see Chapter 14). The catheter can also be used to create an “anatomic” shell of a chamber as well as to acquire multiple simultaneous activation times. A 64-pole retractable “basket” catheter with 8 splines is useful for simultaneous multisite data acquisition for an entire chamber. The schema demonstrates the catheter position in the right atrium when used for the diagnosis and treatment of atrial tachyarrhythmias. This flexible, 20 pole catheter on 5 splines allows for high-density activation mapping. This catheter has a small, flexible basket with 64 poles on 8 splines using small (0. Another catheter that has the characteristics and appearance of a standard ablation catheter that has a magnetic sensor within the shaft near the tip is made by Biosense, Webster (see Fig. Together with a reference sensor, it can be used to precisely map the position of the catheter in three dimensions. This Biosense electrical and anatomic mapping system is composed of the reference and catheter sensor, an external, ultra-low magnetic 5 field emitter, and the processing unit. The amplitude, frequency, and phase of the sensed magnetic fields contain information required to solve the algebraic equations yielding the precise location in three dimensions (x, y, and z axes) and orientation (roll, yaw, pitch) of the catheter tip sensor. A unipolar or bipolar electrogram can be recorded simultaneously with the position in space. This provides precise (∼1 mm) accuracy and allows one to move the catheter back to any desirable position, a particularly important feature in mapping. In addition, the catheter may be moved in the absence of fluoroscopy, thereby saving unnecessary radiation exposure. The catheter, because of its ability to map the virtual anatomy, can display the cardiac dimensions, volume, and ejection fraction. New enhancements include respiratory gating, assessment of catheter stability prior to ablation, and measurement of contact force to optimize the ablation lesion. This is similar to the Rhythmia Medical mapping system which records from 64 poles in unipolar and bipolar modes yielding the highest accuracy, but which requires a separate ablation catheter. Another new mapping methodology, with its own catheter, is Ensite noncontact endocardial mapping system. Endocardial potentials and activations sequences are reconstructed from intracavitary probe signals by a mathematical process called the “inverse solution. It represents both the inverse solution for 64 poles from which several thousand signals are interpolated in space. Whether this technique offers enough spatial resolution to be used to guide precise ablation in large, and/or diseased hearts, requires validation. The number and spacing of ring electrodes on standard, contact mapping catheters may vary. Specially designed catheters with many electrodes (up to 24), an unusual sequence of electrodes, or unusual positioning of bipolar pairs may be useful for specific indications. For routine pacing or recording, a single pair of electrodes is sufficient; simultaneous recording and stimulation require two pairs; and studies requiring detailed evaluation of activation patterns or pacing from multiple sites may require several additional pairs. It is important to realize that while multiple poles can gather simultaneous and accurate data, only the distal pole of an intracavitarily placed electrode will have consistent contact with the wall; thus, electrograms from the proximal electrodes may yield unreliable data. In general, a quadripolar catheter suffices for recording and stimulation of standard sites in the right atrium, right ventricle, and for recording a His bundle electrogram. We routinely use the Bard Electrophysiology multipurpose quadripolar catheter with a 5-mm interelectrode distance for recording and stimulation of the atrium and ventricle as well as for recording His bundle. Mathematically derived electrograms from more than 3,000 sites can be generated from this olive-like probe (see Chapter 14). In studies requiring precise timing of local electrical activity, tighter interelectrode distances are theoretically advantageous. We have evaluated activation times comparing 5- and 10-mm interelectrode distance on the same catheter and have found they do not differ significantly.