Patent foramen ovale is not a benign pathology in patients undergoing off-pump coronary artery bypass: A word of caution

We thank Bozinovski and Caton1 for their valuable article entitled ‘‘A Benign PFO in OPCAB Can Suddenly Take a Right Turn, but Maybe It Can’t Tolerate It.’’ They present a case with desaturation due to right-to-left shunt through a patent foramen ovale (PFO) during off-pump coronary artery bypass (OPCAB). Although rare, this is an extremely important problem in the OPCAB procedure. PFO is a frequent pathology with an estimated prevalence of 25%. 2 However, in cases without a known PFO, intermittent intra-atrial shunting due to an elevated right atrial pressure may be an important problem during OPCAB. Because most patients undergoing off-pump revascularization are high risk in terms of chronic obstructive pulmonary disease and elevated pulmonary artery pressures, opening of a PFO is not infrequent when the right atrial pressure increases. This is particularly evident in cases with left and posterior wall revascularization due to positioning of the heart leading to right atrial compression. These patients are not always capable of tolerating decreases in systemic oxygenation and cyanosis due to right-to-left shunting