double-inlet ventricle with hypoplastic left or right atrioventricular valves, hypoplastic left heart syndrome (HLHS), and others with the Fontan circulation, atrial septostomy is performed to relieve left or right atrial hypertension Patients with left ventricular failure supported by extracorporeal membrane oxygenation may also need transseptal puncture and atrial septostomy to alleviate left atrial hypertension associated with left ventricular standstill In patients with a patent oval foramen or a restrictive atrial communication, rapid pulling of a septostomy balloon catheter filled with fluid (saline and/or contrast) (Fig 18.12), or static balloon atrial septoplasty, usually will enlarge an existing interatrial communication The flap valve of the oval fossa can be torn to enlarge the defect in a graded manner by increasing the volume of contrast or saline in the balloon Often the rapid pull with a septostomy catheter results in a more durable tear along the fossa, whereas a static balloon septoplasty may temporarily stretch the fossa ovalis Access to the atrium may be through umbilical, femoral, or hepatic veins In the cyanotic neonate with transposition of the great arteries, balloon septostomy can be performed at the bedside using transthoracic echocardiographic guidance FIG 18.12 Balloon atrial septostomy by the pullback technique The balloon, filled with contrast, is pulled back from the left to the right atrium to enlarge the atrial communication In patients with an intact atrial septum, a transseptal atrial puncture may be performed to gain access to left-sided structures The use of the transseptal needle requires experience with fluoroscopic and echocardiographic guidance A Brockenbrough needle is used within a long sheath and dilator The length of the needle tip protruding from the dilator should be marked by noting the distance of the proximal flange of the needle from the hub of the dilator within the sheath The arrow on the flange and its alignment to the needle tip should also be checked before inserting the needle into the right heart The long sheath with the dilator is inserted over a guidewire to position the tip of the dilator in the superior caval vein The wire is replaced with the transseptal needle with its tip still sheathed in the dilator Using echocardiography and fluoroscopy in frontal and lateral projections, the whole assembly is slid down into the oval fossa, indicated by stepping over the superior limb of the margin of the oval fossa A pigtail catheter placed in the noncoronary sinus of the aortic valve helps to identify the posterior wall of the aorta Once the needle tip is engaged in the fossa, the septum can be stained with contrast and tented by pushing (Fig 18.13A) A change in the waveform from right to left atrial pressure traces, injection of contrast in the left atrium, and echocardiographic and fluoroscopic guidance, all indicate entry into the left atrium The needle should then be covered with the dilator and the sheath at all times to prevent trauma to the left atrial wall Depending on the indication for transseptal puncture, the needle could be exchanged for other catheters or guidewires Diligent de-airing maneuvers and anticoagulation are required whenever operating in the left atrium and systemic circulation Static or pullback balloon septoplasty is then performed to create an adequate atrial communication (Fig 18.13B) In some instances, when the atrial septum is very thick, the use of a Park blade catheter or a cutting balloon can facilitate atrial septoplasty (Fig 18.13C) FIG 18.13 (A) Transseptal puncture used to decompress the left heart in a patient with dilated cardiomyopathy on extracorporeal membrane oxygenation, illustrating fluoroscopy on frontal projection and transesophageal echocardiography (probe seen) (B) A static balloon dilation used to enlarge the atrial septal puncture (C) Blade atrial septostomy, with the Park blade catheter open with the blade at an angle of 45 degrees A newer method of creating an atrial fenestration is the use of a radiofrequency tipped wire to perforate the intact atrial septum.116 Defects created by static balloon septoplasty or balloon atrial septostomy tend to restrict over time Various methods to keep the defect patent have been attempted, including implantation of stents and the use of manufactured or operatormodified fenestrated devices for atrial septal defect closure.117,118 Paravalvar Leaks Paravalvar leaks around surgically implanted prosthetic valves in aortic or mitral position may lead to hemodynamically significant valvar regurgitation or chronic hemolysis, anemia, and jaundice The leaks may be single or multiple, circular or crescentic in shape, and may sometimes extend all around the circumference of the valve Various devices have been used to close these leaks, including the Rashkind double umbrella device, the Amplatz ductal occluder, or vascular plug and coils For aortic paravalvar leaks, femoral arterial access is most often used to perform an aortogram to identify the leaks and confirm that the origins of the coronary arteries are not in close approximation (Fig 18.14A) Often, focused TEE is helpful in identifying and localizing the paravalvar leak The leak is crossed with a floppy guidewire and then exchanged for a stiff 0.035-inch guidewire that is passed to the LV apex Balloon-sizing of the leak can be performed with a compliant balloon angioplasty catheter (Fig 18.14B) An Amplatzer ductal occluder (Abbott Medical) is often the best device for paraaortic leaks (Fig 18.14C) The device is delivered retrograde through a long sheath Before release, it is necessary to confirm free movement of the valvar leaflets, and unobstructed flow into the coronary arteries