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Patients should be studied in the postabsorptive state and after beta blockers or other antiarrhythmic agents have been discontinued for at least 5 days. Amiodarone should be withdrawn at least 2 months before the procedure if feasible. A transesophageal echocardiogram is recommended to exclude intracardiac thrombi in patients with atrial fibrillation (AF) or atrial flutter and is particularly important in such patients who have not been therapeutically anticoagulated for at least 3 to 4 weeks.
In most cases a diagnostic electrophysiology study (EPS) can be performed without sedation, but conscious sedation is appropriate when needed to attenuate anxiety. Intravenous sedation now can be proceduralist (or operator) directed and nurse administered (i.e., the PDNA model). , An abundance of observational studies have indicated that sedation does not significantly affect basic electrophysiologic properties or inducibility of supraventricular tachycardia (SVT), with the possible exception of automatic atrial tachycardia. , For clinical purposes, this is true not only for the opiate-benzodiazepine combination but even for propofol, despite its dose-related depression of the sinus node and His-Purkinje conduction. The opiate-benzodiazepine combination is safer than propofol but does not necessarily comprise only midazolam and fentanyl. Emulsified diazepam offers a less expensive alternative to midazolam and avoids the irritating effects of intravenously administered diazepam. Morphine or diamorphine (available in the United Kingdom), which lacks the emetic effects of morphine, are alternatives to fentanyl. An initial dose of 5 mg diazepam, followed by 5 mg diamorphine if needed, is usually adequate. However, individual drug and dosing choices depend on drug availability and legal environments in different countries and on the experience of the medical personnel. Dexmedetomidine, an α 2 -adrenergic agonist, is an emerging, attractive sedative because of its short half-life and lack of respiratory depression, although it has been associated with cardiac conduction abnormalities and hypotension.
The femoral veins can be used for insertion of all electrode catheters, including the coronary sinus (CS). Some operators prefer to use the internal jugular vein for the CS catheter. Local anesthesia is administered, and the femoral vein is cannulated. The vein lies just medial to the artery below the inguinal ligament. Many laboratories now require femoral vein cannulation under ultrasound guidance. If this is not feasible, access is accomplished by feeling the femoral artery pulse on the groin crease and puncturing at a point 2 cm medial to and 1 cm higher than the point of maximal impulse. A syringe half filled with heparinized flush solution is attached to the hub of a 18-gauge needle, which is advanced under negative pressure by withdrawing gently on the syringe, at a 45-degree angle from the skin surface. The needle is advanced while gentle aspiration is maintained on the syringe. If the need is inserted quickly, it may penetrate the front and back walls of the vein, reaching the pubic ramus. In this case the needle should be withdrawn slowly back into the vein lumen while maintaining suction. If the femoral artery is inadvertently punctured, the vein puncture is reattempted after 5 minutes of compression on the arterial puncture site.
If the femoral veins are inaccessible or not unsuitable, the internal jugular vein may be used. This is accomplished either by puncturing the vein 2 cm lateral to the carotid pulse in the neck, usually under ultrasound guidance, or by puncturing between the two heads of the sternocleidomastoid muscle that insert into the sternum and clavicle. The needle pierces the skin at the apex of the triangle formed by the two heads of the sternocleidomastoid muscle and is directed inferiorly and posteriorly at a 30-degree angle to the skin. It is important to keep the needle parallel to the midline to avoid the carotid artery. The former approach avoids the risk of pneumothorax at the expense of inadvertent puncture of the carotid artery. In this case 5 minutes of compression of the carotid artery puncture site artery is usually sufficient for hemostasis.
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