To the Editor.
—In your news item (February issue) of my presentation at the American Heart Association meeting, "Clinical Experience With the Unidirectional Dual-Chambered Intraaortic Balloon Assist" (ArchIntern Med127:195, 1971), an important concept has been inadvertently misstated. The sentence should be written "During diastole, sequential inflation of the two sections of the balloon positioned in the descending thoracic aorta results in all blood being pumped toward the heart, thereby maximally increasing coronary blood flow. The balloon is deflated prior to systole by an appropriately timed vacuum applied to the external safety chamber with a resultant decrease in left ventricular work. In contrast to other investigators, we use a fixed volume of carbon dioxide, rather than helium, to effect intraaortic pumping action. We have found the dual-chambered intraaortic balloon to be an extremely safe and effective temporary cardiac assist device which can now enable the physician to stabilize