Cardiovascular Anesthesia: Editorial
Sukernik and Bennett-Guerrero (1) present a thorough and complete review of anatomy and physiology of patent foramen ovale (PFO), followed by an excellent discussion of echocardiographic techniques for diagnosing it. Subsequently, they analyze the pros and cons of surgical closure of an intraoperatively diagnosed “incidental” PFO.
Their article is remarkable because it discusses the indication for PFO closure from an uncommon viewpoint. Most literature dealing with adult PFO revolves around the risk of recurrent paradoxical embolism. The therapeutic options are anticoagulation or interventional PFO closure to prevent recurrency, and the relative ease of interventional closure has led to increasing numbers of such procedures performed by interventional cardiologists. The dilemma is the nearly always putative nature of paradoxical embolism across a PFO. Frequently, neither the embolic nature of the neurologic event nor the absence of other potential sources (e.g., paroxyxsmal atrial fibrillation) are clear, and only the bleak perspective of a repeat event justifies a procedure of unclear benefit and finite risk. The intraoperative situation of incidentally diagnosing a PFO is fundamentally different. There is usually no history of cryptogenic stroke (otherwise, the PFO probably would have been diagnosed earlier) and patients are in an age range in which other sources of embolism, such as atherosclerosis and atrial fibrillation, far outweigh the embolic risk of a PFO.
During cardiac surgery, it seems straightforward to remove a small but potentially harmful anomaly, analogous to what an abdominal surgeon might do with an apparently normal appendix during abdominal surgery or laparoscopy. However, since appendectomy carries a small additional risk of complications (2), this strategy is, too, controversial, especially in older patients (3). Analogously, Sukernik and Bennett-Guerrero aptly point out the additional effort, time, and complication rate incurred by routinely closing an incidental PFO. Surgical closure of PFO is usually performed after cannulation of both caval veins (to be able to empty the right atrium of blood) and atriotomy. Neither is performed during standard bypass surgery. The situation is more simple if mitral (or tricuspid) valve surgery is being performed; in this case, closure of a PFO just requires direct suture of the septa.
It is surprising that, in the cited survey of surgeons’ patients, age was not important when deciding whether to close a PFO. Since the total “burden” of embolic potential can be expected to increase with life expectancy, it is highly unlikely that older patients without a history of unexplained neurologic events and without right ventricular overload would benefit from routine PFO closure during bypass surgery. On the other hand, in a young patient, or in a diver, surgical closure of an incidental PFO is more attractive. However, population- based data estimate, even in a young population (<55 yr), the annual risk of ischemic stroke at approximately 11/100,000 of which one-third may be attributable to PFO (4). Individuals <55 yr with a PFO seem to have a roughly three-fold odds ratio for stroke versus those without PFO (5). Therefore, a staggering amount of PFOs would have to be closed to avoid future PFO-related strokes. In older patients, the relation between PFO and stroke is not even statistically proven (5).
What is the bottom line? If an increased postoperative right atrial pressure is anticipated, PFO closure seems justified to avoid atrial right-to-left shunting and, hence, arterial oxygen desaturation. As the authors mention, this is particularly the case in patients undergoing heart transplantation or those treated with a left ventricular assist device. Luxation of the heart during off-pump bypass surgery to inferior or posterior coronary artery segments may lead to altered hemodynamics, with the potential of intraoperative right-to-left shunting. Divers, especially professional divers, also seem to be at high-risk group for paradoxical embolism (6). Thus, if one of the above-discussed arguments for surgical closure is present, in particular pulmonary hypertension or unexplained previous systemic embolism, incidental PFO should be treated during cardiac surgery. Furthermore, as long as atriotomy is being performed, it seems reasonable to close an incidental PFO in all cases, except perhaps in very old patients. On the other hand, there is no compelling reason to systematically search and close PFO in every patient undergoing bypass surgery.
1. Sukernik MR, Bennett-Guerrero E. The incidental finding of a patent foramen ovale during cardiac surgery: should it always be repaired? Anesth Analg 2007;105:602–10
2. van den Broek WT, Bijnen AB, de Ruiter P, Gouma DJ. A normal appendix found during diagnostic laparoscopy should not be removed. Br J Surg 2001;88:251–4
3. Snyder TE, Selanders JR. Incidental appendectomy—yes or no? A retrospective case study and review of the literature. Infect Dis Obstet Gynecol 1998;6:30–7
4. Kristensen B, Malm J, Carlberg B, Stegmayr B, Backman C, Fagerlund M, Olsson T. Epidemiology and etiology of ischemic stroke in young adults aged 18 to 44 years in northern Sweden. Stroke 1997;28:1702–9
5. Overell JR, Bone I, Lees KR. Interatrial septal abnormalities and stroke: a meta-analysis of case-control studies. Neurology 2000;55:1172–9
6. Reul J, Weis J, Jung A, Willmes K, Thron A. Central nervous system lesions and cervical disc herniations in amateur divers. Lancet 1995;345:1403–5