To the Editor:-Ho et al. [1]report on the successful use of combined spinal and epidural anesthesia for the management of labor and delivery in a patient with idiopathic hypertrophic subaortic stenosis (IHSS).

Idiopathic hypertrophic subaortic stenosis, or hypertrophic obstructive cardiomyopathy (HOCM) as it also is known, is a cardiomyopathy characterized by asymmetric septal hypertrophy, and dynamic left ventricular outflow tract (LVOT) obstruction, which worsens with hypovolemia, increased left ventricular contractility, and vascular dilation. [2]The diagnosis is confirmed with two-dimensional echo-cardiography, and the LVOT gradient is quantified by Doppler echo-cardiography. Provocative testing with inhaled amyl nitrate is used to accentuate the gradient.

In the current case, the diagnosis of IHSS was made several years before pregnancy, but we are given no details regarding its severity; specifically, no mention is made of a “provoked” gradient at diagnosis. Without this information, the reader has no way of knowing what the severity of the condition was and therefore no way of knowing the risks of sympathetic blockade with neuraxial anesthesia. For the patient with the potential for severe LVOT obstruction, the risks of central neuraxial anesthesia are profound and should never be underestimated.

Donald Oxorn, M.D., C.M., F.R.C.P.C.

Department of Anaesthesia and the Division of Cardiology; Sunnybrook Health Science Centre and the University of Toronto; 2075 Bayview Avenue; Toronto, Ontario M4N 3M5; Canada

(Accepted for publication September 4, 1997.)

Ho KM, Ngan Kee WD, Poon MCM: Combined spinal and epidural anesthesia in a parturient with idiopathic hypertrophic subaortic stenosis. Anesthesiology 1997; 87:168-9.
Grigg LE, Wigle ED, Williams WG, Daniel LB, Rakowski H: Transesophageal Doppler echocardiography in obstructive hypertrophic cardiomyopathy: Clarification of pathophysiology and importance in intraoperative decision making. J Am Coll Cardiol 1992; 20:42-52.