Electrophysiological testing: Tools and techniques

Types of anesthesia

The anesthetic plan must be individually tailored, depending on the nature of procedure, patient characteristics, hospital resources, patient preference, and anesthesia skill/training of the EP team. Furthermore, changes in the level of sedation and in the type of drugs used can be necessary during the course of the procedure and must be aligned with the needs of the interventional procedures. For example, the optimal degree of anesthesia can vary from minimal (during induction of arrhythmias) to deep (during painful ablation or electrical cardioversion). Also, the anesthesiologist should be asked to avoid or minimize nondepolarizing muscle relaxants when the evaluation of phrenic nerve function is required during ablation. Therefore, close communication and collaboration between the electrophysiologists and anesthesia providers are crucial to perform EP procedures safely and successfully.

One of the following anesthesia techniques or their combinations may be used: (1) local anesthesia at the site of vascular access; (2) conscious (moderate) sedation with intravenous (IV) sedatives; (3) deep sedation with IV sedatives; and (4) general anesthesia.

Electrophysiological effects of anesthetic medications

The exact influences anesthetics have on cardiac EP in the clinical setting are not entirely certain. In general, sedation of any kind decreases endogenous catecholamine release, potentially suppressing arrhythmic activity, which can impede the mapping and ablation procedure. Nonetheless, some anesthetics (e.g., ketamine) induce sympathetic stimulation, which can potentially facilitate or induce arrhythmias.

Benzodiazepines reduce blood pressure by decreasing peripheral vascular resistance leading to reflex tachycardia. Opioids, especially at high doses, have a central vagotonic effect with resultant bradycardia. Propofol can trigger vagally mediated bradycardia and inhibit spontaneous ventricular arrhythmias.

Inhalational anesthetics enhance automaticity of latent atrial pacemakers relative to the sinus node, promoting ectopic atrial rhythms and wandering atrial pacemakers. Additionally, these agents demonstrate varying effects on the atrioventricular node (AVN) and His-Purkinje system (HPS). Isoflurane prolongs the atrial refractory period and delays ventricular repolarization, but the clinical significance of these effects appears minimal.

Neuromuscular relaxants modulate autonomic tone; some agents can precipitate vasodilatation and reflex tachycardia, while others can cause bradycardia, particularly if used in combination with other vagotonic drugs. Ketamine can increase heart rate and blood pressure by increasing central sympathetic outflow. Also, ketamine is a direct myocardial depressant.

Jet ventilation

Jet ventilation employs low-volume, high-frequency ventilation via endotracheal tube, maintaining adequate gas exchange while minimizing respirophasic cardiac excursion. Using high-frequency ventilation during general anesthesia decreases the regular chest wall motion associated with standard mechanical ventilation, thus minimizing respiration-related cardiac movement.

Recent data suggest that the use of jet ventilation in the EP laboratory can enhance catheter stability during mapping and ablation and potentially improve the efficacy and safety of the ablation procedure, especially when a stable field needs to be established. On the other hand, several disadvantages of high-frequency jet ventilation have been reported, including the lack of airtight sealing of airway to decrease secretions, the inability to use inhaled anesthesia, and the difficult measurement of resulting ventilator parameters and efficiency of gas exchange. Furthermore, the risk of barotrauma (e.g., volutrauma, pneumothorax, mediastinal emphysema) is increased, especially in patients with chronic obstructive pulmonary disease. Mucosal damage, especially necrotizing tracheobronchitis, has been reported and can be prevented by adequate humidification of the ventilator circuit.

Right atrial catheter

A fixed-tip, 5 or 6 Fr quadripolar electrode catheter is typically used. The RA may be entered from the IVC or SVC. The femoral veins are the usual entry sites. Most commonly, stimulation and recording from the RA is performed by placing the RA catheter tip at the high posterolateral wall at the SVC-RA junction in the region of the sinus node or in the RA appendage ( Fig. 5.4 ).

Right ventricular catheter

A fixed-tip, 5 or 6 Fr quadripolar electrode catheter is typically used. All sites in the RV are accessible from any venous approach. The RV apex is most commonly chosen for stimulation and recording because of stability and reproducibility ( Fig. 5.4 ).

His bundle catheter

A fixed- or deflectable-tip, 6 Fr quadripolar electrode catheter is typically used. The catheter is passed via the femoral vein into the RA and across the tricuspid annulus until it is clearly in the RV (under fluoroscopic monitoring, using the right anterior oblique [RAO] view; Fig. 5.4 ). It is then withdrawn across the tricuspid orifice while maintaining a slight clockwise torque for good contact with the septum until a His potential is recorded. Initially, a large ventricular electrogram can be observed; then, as the catheter is withdrawn, the right bundle branch (RB) potential can appear (manifesting as a narrow spike less than 30 milliseconds before the ventricular electrogram). When the catheter is further withdrawn, the atrial electrogram appears and grows larger. The His potential usually appears once the atrial and ventricular electrograms are approximately equal in size and is manifest as a biphasic or triphasic deflection interposed between the local atrial and ventricular electrograms. If the first pass was unsuccessful, the catheter should be passed again into the RV and withdrawn with a slightly different rotation. If, after several attempts, a His potential cannot be recorded using a fixed-tip catheter, the catheter should be withdrawn and reshaped, or it may be exchanged with a deflectable-tip catheter. Once the catheter is in place, a stable recording can usually be obtained. Occasionally, continued clockwise torque on the catheter shaft is required to obtain a stable HB recording, which can be accomplished by looping the catheter shaft remaining outside the body and fixing the loop by placing a couple of towels on it, or by twisting the connection cable in the opposite direction so that it maintains a gentle torque on the catheter.

When the access is from the SVC, it is more difficult to record the His potential because the catheter does not lie across the superior margin of the tricuspid annulus. In this case, a deflectable-tip catheter is typically used, advanced into the RV, positioned near the HB region by deflecting the tip superiorly to form a J shape, and then withdrawing the catheter so that it lies across the superior margin of the tricuspid annulus. Alternatively, the catheter can be looped in the RA (“figure-of-6” position); then the body of the loop is advanced into the RV so that the tip of the catheter is pointing toward the RA and lying on the septal aspect of the RA. Gently withdrawing the catheter can increase the size of the loop and allow the catheter tip to rest on the HB location.

Recording of the HB electrogram also can be obtained via the retrograde arterial approach. Using this approach, the catheter tip is positioned in the noncoronary sinus of Valsalva (just above the aortic valve) or in the LV along the interventricular septum (just below the aortic valve).

Coronary sinus catheter

A femoral, internal jugular, or subclavian vein can be used to access the CS. It is easier to cannulate the CS using the right internal jugular or left subclavian vein versus the femoral vein because the CS valve is oriented anterosuperiorly and, when prominent, can prevent easy access to the CS from the femoral venous approach. A fixed-tip, 6 Fr decapolar electrode catheter is typically used for access from the SVC, whereas a deflectable-tip catheter is required for CS access from the femoral veins. If used, the CS catheter preferably is placed first, because its positioning can be impeded by the presence of other catheters.

The standardized RAO and left anterior oblique (LAO) fluoroscopic views are used to guide placement of catheters in the CS. Although the CS cannot be directly visualized with standard fluoroscopy, the epicardial fat found in the posteroseptal space just posterior to the CS ostium (CS os) can be visualized as a characteristic radiolucency on cine fluoroscopy in the RAO projection, where the cardiac and diaphragmatic silhouettes meet.

When cannulating the CS from the SVC approach, the LAO view is used, the catheter tip is directed to the left of the patient, and the catheter is advanced with some clockwise torque to engage the CS os; electrodes should resemble rectangles rather than ovals when the catheter tip is properly oriented to advance into the CS. Once the CS os is engaged, the catheter is further advanced gently into the CS so that the most proximal electrodes lie at the CS os ( Fig. 5.4 ).

During cannulation of the CS from the IVC approach, the tip of the catheter is first placed into the RV, in the RAO fluoroscopy view, and flexed downward toward the RV inferior wall ( Video 5.1 ). Subsequently, the catheter is withdrawn until it lies at the inferoseptal aspect of the tricuspid annulus. In the LAO or RAO view, the catheter is then withdrawn gently with clockwise rotation until the tip of the catheter drops into the CS os. Afterward, the catheter is advanced into the CS concomitantly with gradual release of the catheter curve ( Fig. 5.5 ). Alternatively, the tip of the catheter is directed toward the posterolateral RA wall and advanced with a tight curve to form a loop in the RA, in the LAO view, with the tip directed toward the inferomedial RA. The tip is then advanced with gentle up-down, right-left manipulation using the LAO and RAO views to cannulate the CS. In the RAO view, the atrioventricular (AV) fat pad (containing the CS) appears more radiolucent than surrounding heart tissue.

When attempting CS cannulation, the catheter can enter the RV, and PVCs or VT can be observed. Catheter position in the RV outflow tract (RVOT) can be misleading and simulate a CS position. Confirming appropriate catheter positioning in the CS can be achieved by fluoroscopy and recorded electrograms. In the LAO view, further advancement in the CS directs the catheter toward the left heart border, where it curves toward the left shoulder. Conversely, advancement of a catheter lying in the RVOT leads to an upward direction of the catheter toward the pulmonary artery. In the RAO view, the CS catheter is directed posteriorly, posterior to the AV sulcus, whereas the RVOT position is directed anteriorly. Recording from the CS catheter shows simultaneous atrial and ventricular electrograms, with the atrial electrogram falling in the later part of the P wave, whereas a catheter lying in the RVOT records only a ventricular electrogram. The catheter can also pass into the LA via a patent foramen ovale, in which case it takes a straight course toward the left shoulder, and all recordings are atrial. In younger individuals, the course of the CS can be almost diagonally toward the left shoulder, whereas in older patients, a more horizontal course is typical for the proximal portion of the CS.

Anatomical considerations

Knowledge of septal anatomy and its relationship with adjacent structures is essential to ensure safe and effective access to the LA. Many apparent atrial septal structures are not truly septal. The true interatrial septum is limited to the floor of the fossa ovalis (primary septum), the flap valve, and the anteroinferior rim of the fossa. Therefore, the floor of the fossa (with an average diameter of 18.5 ± 6.9 mm [vertically] and 10.0 ± 2.4 mm [horizontally], and 1 to 3 mm in thickness) is the target for atrial septal crossing ( Fig. 5.7 ). The area between the superior border of the fossa and the mouth of the superior vena cava (SVC) is an infolding of the atrial musculature filled with adipose tissue (corresponding to the pericardial transverse sinus and the anterosuperior interatrial groove, known as Waterston groove). Although this area is often described, incorrectly, as the “septum secundum,” it is not really a true septum, and puncture in this region would lead to exiting the heart. The infolded groove ends at the superior margin (superior rim) of the fossa ovalis. The anteroinferior muscular buttress anchors the primary septum to the muscular ventricular septum and attaches to the central fibrous body (which is composed of the right fibrous trigone and the AV portion of the membranous septum) just beneath the noncoronary aortic sinus. Anterior and superior to the fossa ovalis, the RA wall overlies the aortic root. Advancing the transseptal needle in this area can puncture the aorta. ^,

The fossa ovalis can have different sizes and shapes. Generally, the larger sizes are found in patients with large atria, while the smallest sizes are often associated with the so-called “lipomatous hypertrophy of the interatrial septum,” whereby accumulation of adipose tissue in the interatrial groove (and not in the true septum) exhibits a characteristic hourglass appearance on echocardiography ( Fig. 5.8 ). Furthermore, displacement of the fossa ovalis and the orientation of the septal plane can be observed, especially in patients with atrial dilatation, severe kyphoscoliosis, or an enlarged aorta.

Understanding the attitudinal anatomical relationships of the atrial septum and adjacent structures as well as the fluoroscopic anatomy based on conventional landmarks is critical for a safe and successful transseptal puncture procedure. When the heart is viewed in an attitudinally correct orientation (as it lies within the chest), the RA lies rightward and anterior, while the LA lies posterior, leftward, and slightly superior in relation to the RA. The aortic root runs along the anterior aspect of the interatrial septum (see eFig. 13.1 ). The fossa ovalis is located inferior and posterior relative to the noncoronary aortic sinus, and posterior to the triangle of Koch. The plane of the interatrial septum is slanted from left anterior to right posterior, with a mean orientation of 37°, but can vary from 19° to 53°. The orientation of the atrial septum was found to strongly correlate with the direction of the CS, despite a wide range of variability. Hence, typically, the interatrial septum is almost perpendicular to the plane of the screen in the LAO 50° to 60° projection angle, and horizontal in the RAO 30° to 40° projection angle. However, adjustment of the RAO and LAO projection angles can be required to account for rotation of the interatrial septum observed in some patients. This can be facilitated by aligning the RAO projection to an angle where the proximal part of CS catheter lies perpendicular to the screen or a His recording catheter is pointing directly toward the screen.

Additionally, when looking perpendicularly onto the atrial septum, as viewed in the mid-RAO fluoroscopy projection, the line indicated by the guidewire running between the IVC and SVC projects approximately onto the area of the fossa ovalis.

Anticoagulation

Anticoagulation is essential for prevention of thromboembolism during any left-sided heart catheterization. Current recommendations advocate that IV heparin bolus be administered immediately after or, preferably, just before puncturing the atrial septum, followed by intermittent boluses or continuous heparin infusion to maintain an elevated ACT (300–400 seconds), even in patients on uninterrupted therapeutic doses of oral anticoagulation. However, recent evidence found that unfractionated heparin displays unexpected slow anticoagulation kinetics in a significant proportion of patients for up to 20 minutes after infusion (reflected in ACTs less than 300 seconds). Hence, some investigators have suggested administering IV heparin at least 10 minutes before transseptal puncture and assessing ACT at 10 minutes with additional heparin doses in patients with subtherapeutic ACT.

Fluoroscopy-guided transseptal catheterization

Equipment required for atrial septal puncture includes the following: an 8 Fr transseptal sheath for LA cannulation (e.g., SR0, SL series, Mullins, or Agilis Steerable sheath, Abbott, Chicago, IL, USA), a 0.032-inch J guidewire, a Brockenbrough needle (e.g., BRK, Abbott, Chicago, IL, USA), and a 190-cm, 0.014-inch guidewire. The transseptal sheaths and Brockenbrough needles are available in two different lengths; it is important to ensure that the length of needle matches that of the sheath.

Venous access is obtained via the femoral vein, preferably the right femoral vein because it is closer to the operator. The sheath, dilator, and guidewires are flushed with heparinized saline. The transseptal sheath-dilator assembly is advanced over a 0.032-inch J guidewire under fluoroscopy guidance into the SVC. The guidewire is then withdrawn, thus leaving the sheath and its dilator locked in place. The dilator within the sheath is flushed and attached to a syringe to avoid introduction of air into the RA.

Attention is then directed to preparing the transseptal needle. The Brockenbrough needle comes prepackaged with an inner stylet, which may be left in place to protect it as it is advanced within the sheath and to avoid perforation or scraping of the plastic dilator. Alternatively, the inner stylet may be removed and the needle connected to a pressure transducer line (pressure monitoring through the Brockenbrough needle will be required during the transseptal puncture); continuous flushing through the Brockenbrough needle is used while advancing the needle into the dilator. If resistance is met while advancing the needle within the dilator, the needle should not be forced, to avoid severing the dilator and the sheath); instead, the needle and dilator assembly need to be removed and expected for any imperfections and replaced if necessary. A third approach, when the use of contrast injection is planned, is to attach the Brockenbrough needle to a standard three-way stopcock via a freely rotating adapter. A 10-mL syringe filled with radiopaque contrast is attached to the other end of the stopcock, while a pressure transducer line is attached to the third stopcock valve for continuous pressure monitoring. The entire apparatus should be vigorously flushed to ensure that no air bubbles are present within the circuit.

Before making an attempt at puncturing the atrial septum, it is important to ensure that all equipment is working properly, especially the pressure transducer attached to the needle. If this detail is not attended to prior to the septal puncture attempt, it becomes difficult to interpret a flat pressure tracing when the needle tip is supposedly in the LA cavity. This may mean the needle is in fact in the LA but the stopcock on the pressure tubing is turned incorrectly, or that the wrong tubing was connected to the needle hub, or that the needle tip is not in the LA. Assuring that the pressure system is working properly by “flicking” the needle shaft and seeing its corresponding pressure reverberation waveform obviates uncertainty as to whether the connections are correct. In addition, taking note of baseline blood pressure and appearance of the left heart border on fluoroscopy are important for reference; unanticipated decreases in BP or decreased motion of the left heart border, compared to baseline, can be early clues to a developing pericardial effusion.

Confirming position at the fossa ovalis

Several fluoroscopic markers are used to confirm the position of the dilator tip at the fossa ovalis. As noted, an abrupt leftward movement (jump) of the dilator tip below the aortic knob is observed (in the LAO view) as the tip passes under the muscular atrial septum onto the fossa ovalis. In addition, the posterior extent of the aortic root can be marked by a pigtail catheter positioned through the femoral artery in the noncoronary cusp or by the HB catheter (recording a stable proximal HB potential), which lies at the level of the fibrous trigone opposite and caudal to the noncoronary aortic cusp ( Fig. 5.9 ). When the dilator tip lies against the fossa ovalis, it is directed posteroinferiorly to the proximal HB electrode (or pigtail catheter) in the RAO view and to the left of the proximal HB electrode (or pigtail catheter) in the LAO view. Another method that can be used to ensure that the tip is against the fossa ovalis is injection of 3 to 5 mL of radiopaque contrast through the Brockenbrough needle to visualize the interatrial septum. The contrast stains the fossa and the needle tip then can be seen tenting the fossa ovalis membrane with small movements of the entire transseptal apparatus. Typically, septal staining remains visible after contrast injection, which allows for real-time septal visualization while monitoring the pressure during transseptal puncture.

Intracardiac echocardiography–guided transseptal catheterization

Although fluoroscopy provides sufficient information to allow safe transseptal puncture in most cases, variations in septal anatomy, atrial or aortic root dilation, the need for multiple punctures, and the desired ability to direct the catheter to specific locations within the LA can make fluoroscopy inadequate for complex LA ablation procedures. Intraoperative TEE allows identification of the fossa ovalis and its relation to surrounding structures and provides real-time evaluation of the atrial septal puncture procedure, with demonstration of tenting of the fossa prior to entry into the LA and visualization of the sheath advancing across the septum. However, the usefulness of TEE is limited by the fact that the probe obstructs the fluoroscopic field, and it is impractical in the nonanesthetized patient. ICE, which provides similar information on septal anatomy, can be used for the conscious patient and does not impede fluoroscopy ( Videos 5.4 and 5.5 ).

The intent of ICE-guided transseptal catheterization is to image intracardiac anatomy and identify the exact position of the distal aspect of the transseptal dilator along the atrial septum—in particular, to assess for tenting of the fossa ovalis with the dilator tip.

Two types of ICE imaging systems are currently available, the electronic phased-array ultrasound catheter and the mechanical ultrasound catheter. The phased-array ultrasound catheter sector imaging system uses an 8 or 10 Fr catheter that has a forward-facing 64-element vector phased-array transducer scanning in the longitudinal plane. The catheter has a four-way steerable tip (160° anteroposterior or left-right deflections). The catheter images a sector field oriented in the plane of the catheter. The mechanical ultrasound catheter radial imaging system (Ultra ICE, EP Technologies, Boston Scientific, San Jose, CA, USA) uses a 9-MHz catheter-based ultrasound transducer contained within a 9 Fr (110-cm length) catheter shaft. It has a single rotating crystal ultrasound transducer that images circumferentially for 360° in the horizontal plane. The catheter is not freely deflectable.

When using the mechanical radial ICE imaging system, a 9 Fr sheath (preferably a long, preshaped sheath) for the ICE catheter is advanced via a femoral venous access. To enhance image quality, all air must be eliminated from the distal tip of the ICE catheter by flushing vigorously with 5 to 10 mL of sterile water. The catheter then is connected to the ultrasound console and advanced until the tip of the rotary ICE catheter images the fossa ovalis. Satisfactory imaging of the fossa ovalis for guiding transseptal puncture is viewed from the mid-RA ( eFig. 5.3 ).

The phased-array ICE catheter is introduced through a femoral venous sheath. Once the catheter is advanced into the mid-RA with the catheter tension controls in neutral position (the ultrasound transducer oriented anteriorly and to the left), the RA, tricuspid valve, and RV are viewed. This is called the home view ( Fig. 5.10 A). Gradual clockwise rotation of a straight catheter from the home view allows sequential visualization of the aortic root and the pulmonary artery ( Fig. 5.10 B), followed by the CS, the mitral valve, the LA appendage orifice, and a cross-sectional view of the fossa ovalis ( Fig. 5.10 C and D). The mitral valve and interatrial septum are usually seen in the same plane as the LA appendage. Posterior deflection or right-left steering of the imaging tip in the RA, or both, is occasionally required to optimize visualization of the fossa ovalis; the tension knob (lock function) can then be used to hold the catheter tip in position. Further clockwise rotation beyond this location demonstrates images of the left PV ostia ( Fig. 5.10E , Video 5.4 ). The optimal ICE image to guide transseptal puncture demonstrates adequate space beyond the interatrial septum on the LA side and clearly identifies adjacent structures, but it does not include the aortic root because it would be too anterior for the interatrial septum to be punctured safely. In patients with an enlarged LA, a cross-sectional view that includes the LA appendage is also optimal if adequate space exists beyond the atrial septum on the LA side.

The sheath-dilator-needle assembly is introduced into the RA, and the dilator tip is positioned against the fossa ovalis, as described earlier. Before advancing the Brockenbrough needle, continuous ICE imaging should direct further adjustments in the dilator tip position until ICE confirms that the tip is in intimate contact with the middle of the fossa, confirms proper lateral movement of the dilator toward the fossa, and excludes inadvertent superior displacement toward the muscular septum and aortic valve. With further advancement of the dilator, ICE demonstrates tenting of the fossa ( eFig. 5.3 ; Fig. 5.11 ). If the distance from the tented fossa to the LA free wall is small, minor adjustments in the dilator tip position can be made to maximize the space. The Brockenbrough needle is then advanced. With successful transseptal puncture, a palpable pop is felt, and sudden collapse of the tented fossa is observed ( Fig. 5.11 ). Advancement of the needle is then immediately stopped. Saline infusion through the needle is visualized on ICE as microbubbles in the LA, thus confirming successful septal puncture. With no change in position of the Brockenbrough needle, the transseptal dilator and sheath are advanced over the guidewire into the LA, as described earlier.

Additionally, ICE can be used instead of fluoroscopy to guide positioning of the transseptal sheath-dilator-needle assembly at the fossa ovalis. Using the fluoroless approach, the ICE catheter is advanced into the RA. From the ICE home view, clockwise rotation of the ICE catheter brings into view the interatrial septum and LA. From this position, a posterior tilt and minimal counterclockwise rotation allows visualization of the SVC. The guidewire is then advanced into the SVC under direct ICE visualization. The transseptal sheath–dilator assembly is advanced over the guidewire. Then, the guidewire is removed, and the transseptal needle is placed in the sheath–dilator and advanced until the needle tip is within 1 to 2 cm of the dilator tip. The transseptal assembly is then withdrawn into the RA while being tracked by ICE, until tenting of the interatrial septum is seen observed on ICE (see above). This requires simultaneous release of the posterior torque on the ICE catheter to allow visualization of the interatrial septum and fossa ovalis.

Alternative methods for transseptal catheterization

In some cases, the conventional approach using a Brockenbrough needle sheath fails to pierce the septum because of the presence of a small fossa area, a thick interatrial septum, fibrosis and scarring of the septum from previous interventions, or an aneurysmal septum with excessive laxity. Applying excessive force to the needle-dilator-sheath assembly against a resistant septum (which can be seen as bending and buckling of the assembly in the RA) can lead to building pressure of the needle tip on the septum, which can potentially lead to an uncontrolled sudden jump of the assembly once across the fossa ovalis, thus perforating the opposing lateral LA wall. Similarly, excessive tenting of the interatrial septum (beyond halfway into the LA) can bring it in proximity to the lateral LA wall so that the needle can potentially puncture the lateral LA wall once across the septum. Some of these difficulties can be overcome by manually reshaping the curvature of the Brockenbrough needle tip, applying slight rotation on the needle and sheath assembly to puncture a different point on the fossa ovalis, or using a sharper transseptal needle type (BRK-1 extra sharp). Alternatively, the stylet provided with the needle or the back end of a 0.014-inch or 0.018-inch wire can be advanced through the Brockenbrough needle to enhance puncture success.

Other tools designed specifically for transseptal puncture, including the SafeSept Transseptal Guidewire and the RF-powered needle or RF wire, can help minimize pressure application to the needle as it crosses the septum and tenting of the septum, which can potentially reduce the chances of sudden advancement through the lateral LA as the needle crosses the septum.

Transseptal puncture in the presence of atrial septal defect repair

Transseptal catheterization is feasible and safe in most patients with prior surgical repair of an atrial septal defect or patent foramen ovale. Nonetheless, because of the altered anatomical landmarks after repair, fluoroscopic guidance for transseptal puncture is not as reliable, and the procedure can be challenging. In these patients, an understanding of the method of repair and utilization of ICE guidance are essential.

In patients with a septal stitch or pericardial or Dacron patch, puncture can be achieved through the thickened septum or the patch. However, transseptal access is typically not achievable through a Gore-Tex patch (W.L. Gore & Associates, Flagstaff, AZ, USA) because of its resistant texture; instead, puncture can be performed directly through neighboring native interatrial tissue. However, when the patch is wide, sufficient free septal tissue for transseptal puncture may not be available, in which setting transseptal access to the LA may not be feasible.

In patients with atrial septal defect closure devices, most of the occlusion device is positioned in the anterior superior location; therefore, puncture is preferably performed at the portion of the septum located inferior and posterior to the closure device, and not through the device itself ( Fig. 5.12 , Video 5.8 ). When areas of native septum are not available for transseptal access, recent reports described successful LA access through a direct puncture of the closure device. In the latter situation, advancing and manipulating the transseptal sheath can be challenging; thus, dilating the access site across the device can be necessary. This can be achieved by advancing an extra-stiff guidewire through the device into a left PV and using an upsized dilator (11 Fr) over the wire to further dilate the access site across the device and facilitate sheath passage and manipulation. Alternatively, an angioplasty guidewire can be advanced through the device into a left PV and sequential dilatation is performed using 3.0–5.0-mm noncompliant angioplasty balloon under pressure of 14 to 18 atm.

Complications of atrial transseptal puncture

Injury to cardiac and extracardiac structures is the most feared complication. Because of its stiffness and large caliber, the transseptal dilator should never be advanced until the position of the Brockenbrough needle is confirmed with confidence. Advancing the dilator into an improper location, such as the aortic root, can be fatal. Therefore, many operators recommend the use of ICE-guided transseptal puncture, especially for patients with normal LA chamber size.

Anatomical considerations

The pericardium is a double-walled sac that contains the heart and the roots of the great arteries, SVC, and PVs. By separating the heart from its surroundings—the descending aorta, lungs, diaphragm, esophagus, trachea, and tracheobronchial lymph nodes—the pericardial space allows complete freedom of cardiac motion within this sac.

The pericardium consists of two sacs intimately connected with one another: an outer fibrous envelope (the fibrous pericardium) and an inner serous sac (the serous pericardium). The fibrous pericardium (0.8–2.5 mm in thickness) consists of fibrous tissue and forms a flask-shaped bag, the neck of which is closed by its fusion with the adventitia of the great vessels, while its base is attached by loose fibroareolar tissue to the central tendon and to the muscular fibers of the left side of the diaphragm. The fibrous pericardium is also attached to the posterior sternal surface by superior and inferior sternopericardial ligaments. These attachments are essential to maintain the normal cardiac position in relation to the surrounding structures, to restrict the volume of the thin-walled cardiac chambers (RA and RV), and also to serve as direct protection against injuries.

The serous pericardium is a delicate membrane that lies within the fibrous pericardium and lines its walls; it is composed of two layers: the parietal pericardium and the visceral pericardium. The parietal pericardium is fused to and inseparable from the fibrous pericardium. On the other hand, the visceral pericardium, which is composed of a single layer of mesothelial cells, is part of the epicardium (i.e., the layer immediately outside of the myocardium) and covers the heart and the great vessels except for a small area on the posterior wall of the atria. The visceral layer extends to the beginning of the great vessels and is reflected from the heart onto the parietal layer of the serous pericardium along the great vessels in tube-like extensions. This happens at two areas: where the aorta and pulmonary trunk leave the heart and where the SVC, IVC, and PVs enter the heart.

The pericardial cavity or sac is a continuous virtual space that lies between the parietal and visceral layers of serous pericardium. The heart invaginates the wall of the serous sac from above and behind and practically obliterates its cavity, the space being merely a potential one. The pericardial sac normally contains 20 to 40 mL of clear fluid that occupies the virtual space between the two layers and serves as a lubricant.

The lateral surfaces of the heart are predominantly covered by the lungs, prohibiting a direct percutaneous access to the pericardial space. The anterior borders of the lungs extend vertically downward along the midsternal line. The right lung anterior border curves laterally and downward at the level of the sixth costal cartilage on the right side. On the left side, however, the anterior border of the lung diverges laterally at an earlier point (at the level of the fourth costal cartilage), forming the cardiac notch, and reaches the parasternal line at the fifth costal cartilage (about 1 inch from the sternal border) before turning medially and downward (as the lingula) to the sixth sternocostal junction ( eFig. 5.4 ). Thus, the subxiphoid region offers a window for direct pericardial access without traversing the lungs. Nonetheless, even with the subxiphoid approach, a needle angulated too far in the lateral direction can potentially puncture the left lung and result in pneumothorax.

In the subxiphoid pericardial access approach, the needle traverses the skin, subcutaneous tissue, and rectus abdominis and then travels above the dome of the diaphragm before arriving at the fibrous pericardium. In the vicinity of the path of the needle lie several important structures that can be vulnerable to damage, including the diaphragm and diaphragmatic vessels, left internal mammary artery, lung, left lobe of the liver, stomach, and transverse colon.

The diaphragm is a dome-shaped muscular structure that separates the thoracic cavity from the abdomen. The muscle fibers of the diaphragm emerge from the circumference of the inferior thoracic aperture and converge in a central tendon , which forms the crest of the dome. The pericardium rests on the central tendon, an almost flat area of the dome of the diaphragm (the cardiac plateau). Anteriorly, the muscle fibers of the diaphragm emerge from the xiphoid process and along the costal margin and arch back in a “parachute” shape to a maximum height equivalent to the xiphisternal junction at the midline. The left hemidiaphragm conforms to the left lobe of the liver, the fundus of the stomach, the spleen, and the left kidney. The left lobe of the liver is near the xiphoid process and can be particularly at risk in patients with hepatomegaly. Manual pressure over the right upper quadrant can help displace the liver and abdominal contents posteriorly away from the path of the needle.

The internal mammary (internal thoracic) artery arises from the subclavian artery and descends vertically 1 to 1.5 centimeters lateral to the sternal border, behind the first six costal cartilages, accompanied by the internal thoracic vein. After passing the sixth intercostal space, the internal mammary artery bifurcates into the superior epigastric artery (which continues downward into the abdominal wall) and the musculophrenic artery (which roughly follows the costal margin, approximately 2 cm from the xiphisternum). The risk of puncturing the internal mammary artery is increased when the needle entry or trajectory is too lateral.

Technical considerations

The subxiphoid percutaneous epicardial access can be performed under conscious sedation, deep sedation with the support of an anesthesiologist, or general anesthesia. General anesthesia allows better control of respiratory motion, which can potentially reduce the chance of unintentional RV puncture, as well as better pain control, given the fact that epicardial RF ablation is usually associated with significant pain and discomfort. IV antibiotics are routinely administered within an hour prior to the procedure. Previous heparin administration should be reversed before pericardial access.

Advancing the needle

The pericardial space is accessed using a 17- or 18-gauge, blunt-tipped Tuohy needle (6 inch in length), which is also used to enter the epidural space when administering epidural anesthesia ( eFig. 5.5 ). The Tuohy needle has a curved, spatula-like tip, which is advantageous to directing the guidewire away from the epicardium upon entry into the pericardial space.

The puncture is performed at the angle between the left border of the subxiphoid process and the lower left rib cage (approximately 1 cm to the left of the xiphoid process and 1–2 cm below the costal margin). Too lateral a puncture site is avoided to help minimize the risk of injury to the internal mammary or superior epigastric arteries. In patients with more abdominal adiposity, a more caudal skin entry site may be necessary to allow for a sufficiently shallow angle under the costal margin. A small incision on the skin at the puncture site helps reduce the resistance when introducing the pericardial access needle and enhance tactile feedback upon puncturing the fibrous pericardium.

The needle is then introduced aiming toward the left midclavicle or the left shoulder and at a shallow angle (<20°) in order to penetrate the skin and slide under the left rib cage, above and parallel to the dome of the diaphragm while avoiding injury to diaphragmatic vessels and subdiaphragmatic organs. Occasionally, manual pressure over the epigastrium is required to push away the liver from the path of the needle.

Once over the dome of the diaphragm, the needle can be angled to a steeper degree (according to whether an anterior or posterior approach is preferred, see below) and advanced under fluoroscopic guidance until close to the cardiac silhouette. A straight left lateral fluoroscopy projection can be of value as it allows for visualization of the main landmarks used to guide epicardial access: xiphisternum, dome of the diaphragm, and cardiac silhouette ( eFig. 5.6 ). Alternatively, RAO and LAO fluoroscopy projections can be used.

Directing the needle superiorly at a relatively shallow angle (passing just posterior to the sternum on a steep lateral fluoroscopy projection), aiming for the RV apex in the RAO projection, generally allows entry into the pericardial space anteriorly over the RV and facilitates access to the anterior aspect of the RV and LV. Directing the needle more posteriorly and toward the left shoulder allows it to enter the pericardium over the diaphragmatic portion of the heart, such that the sheath typically tracks along the posterior aspect of the LV, as observed in the LAO projection. In the RAO view, the middle third of the RV is the preferred entry region because of the absence of major coronary vessels in this region (which are typically located in the AV groove as well as in the apex [such as a wraparound left anterior descending artery]).