Septal Perforation

Background

EarlyStages keySeptal perforation is a technique in which a small hole is created in the cardiac septum to allow for communication between chambers of the heart. Under normal conditions, deoxygenated blood is pumped from the right side of the heart to the lungs to be oxygenated through the pulmonary circulation. This oxygen rich blood then returns to the left side of the heart to be pumped into the systemic circulation through the aorta. In certain conditions, this closed loop cardio-pulmonary circuit is disturbed.

Common conditions where septal perforation is needed include cyanotic heart defects and pulmonary artery hypertension (PAH). Cyanotic heart defects result in the distribution of deoxygenated blood into the systemic circulation with life-threatening consequences. In PAH, there is elevated pressure in the pulmonary circulation, which places strain on the right side of the heart, ultimately resulting in right heart failure if uncorrected.

Current Treatment

Atrial septostomy (AS) is used to treat these conditions. There are two methods in which AS is currently performed-- balloon atrial septostomy and blade atrial septostomy. Balloon atrial septostomy involves a guiding a balloon catheter into the right atrium of the heart. The catheter is then advanced through a naturally existing hole between the atria (foramen ovale), which normally closes shortly after birth. The balloon prevents it from closing before corrective surgery can be performed. A blade atrial septostomy follows the same procedure, but is performed when balloon septostomy fails or is not possible due to a closed foramen ovale. Risks of this procedure include tearing of the cardiac tissue, balloon rupture and embolization of balloon fragments, stroke and vascular complications, and rarely death.

Focused Ultrasound Research

Focused ultrasound (FUS) is a non-invasive modality for the thermal ablation of tissue. Pilot clinical research has demonstrated the potential of focused ultrasound to accurately and repeatedly create focal perforations in atrial tissue without direct contact. Aside from its thermal ablative effects, focused ultrasound is also capable of precise mechanical tissue destruction through a process known as histotripsy. This procedure utilizes high intensity, pulsed ultrasound to collapse bubbles of gas in tissue, which releases a shockwave capable of liquefying cells in a phenomenon known as inertial cavitation. A preclinical study has already demonstrated the ability of histotripsy to non-invasively create an atrial septal defect in a canine model. As such, focused ultrasound has the potential to be an effective tool for the treatment of conditions which benefit from the presence of a shunt between cardiac chambers. Furthermore, this technique may also be applied for various cardiac treatments other than AS, such as left ventricular ablation for ventricular arrhythmia and left ventricular septal ablation for hypertrophic obstructive cardiomyopathy and congenital aortic/pulmonary valve stenosis.

Notable Papers

Takei Y, Muratore R, Kalisz A, Okajima K, Fujimoto K, Hasegawa T, Arai K, Rekhtman Y, Berry G, Di Tullio MR, Homma S. In vitro atrial septal ablation using high-intensity focused ultrasound. J Am Soc Echocardiogr. 2012 Apr;25(4):467-72.

Owens GE, Miller RM, Owens ST, Swanson SD, Ives K, Ensing G, Gordon D, Xu Z. Intermediate-term effects of intracardiac communications created noninvasively by therapeutic ultrasound (histotripsy) in a porcine model. Pediatr Cardiol. 2012 Jan;33(1):83-9. doi: 10.1007/s00246-011-0094-6. Epub 2011 Sep 11. PubMed PMID:21910018.

Xu Z, Owens G, Gordon D, Cain C, Ludomirsky A. Noninvasive creation of an atrial septal defect by histotripsy in a canine model. Circulation. 2010 Feb16;121(6):742-9. doi: 10.1161/CIRCULATIONAHA.109.889071. Epub 2010 Feb 1. PubMed PMID: 20124126; PubMed Central PMCID: PMC2834201.

Otsuka R, Fujikura K, Abe Y, Okajima K, Pulerwitz T, Engel DJ, Muratore R, Ketterling JA, Kalisz A, Sciacca R, Marboe C, Yi G, Wang J, Homma S. Extracardiac ablation of the left ventricular septum in beating canine hearts using high-intensity focused ultrasound. J Am Soc Echocardiogr. 2007 Dec;20(12):1400-6.

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