Severe Subaortic Stenosis

A 61-year-old woman (with a body surface area of 1.63 m2) presented for aortic valve (AV) replacement secondary to moderately severe aortic insufficiency because of aortic valvular and subvalvular stenosis. Preoperative transthoracic echocardiography demonstrated a peak pressure gradient of 108 mm Hg. Her medical and surgical history was significant for hypertension, hypercholesterolemia, and surgical repair of a patent ductus arteriosus with excision of a subaortic web approximately 40 years previously. No preoperative cardiac output was available. The intraoperative transesophageal echocardiograph (TEE) midesophageal long axis image of the AV and left ventricular outflow tract (LVOT) revealed a web-like structure attached to the ventricular side of the base of the anterior mitral leaflet (Fig. 1, please see video clip available at www.anesthesia-analgesia.org). The aortic annular and LVOT dimensions were 16 and 12 mm, respectively (Fig. 2). AV planimetry was 1.2 cm2. Color flow Doppler demonstrated severe aortic insufficiency, with acceleration of flow at the level of the LVOT in systole (Fig. 3). The peak and mean LVOT gradients were 42 and 16 mm Hg, respectively.Figure 1.: Transesophageal echocardiographic midesophageal long axis view of the aortic valve at a multiplane angle of 125 degrees in mid systole. There is a ridge attached to the anterior aspect of the mitral valve. The left ventricular outflow tract is narrowed on all its length.Figure 2.: Transesophageal echocardiographic mid-esophageal long axis view of the aortic valve (AV) at a multiplane angle of 125 degree. The measurement of the AV diameter, aortic (Ao) diameter (diam) of the sinus of Valsalva (SVals), the aortic sinotubular (st) junction (junct), and the ascending (asc) aorta are shown.Figure 3.: Transesophageal echocardiographic mid-esophageal long axis view of the aortic valve at a multiplane angle of 125 degree. The color Doppler acceleration in the left ventricular outflow tract is shown.Because of the small dimension of the aortic root and severe narrowing of the LVOT, the surgeons elected to perform a Konno procedure. This procedure is used to palliate tunnel type subaortic stenosis. It involves full thickness resection of the ventricular septum, patch enlargement of the LVOT with concomitant AV replacement (1). A Carbo Medics Inc 23 model R500 (Sorin Group, Austin, TX) with an effective orifice area of 1.63 cm2 was implanted. The mean gradient by continuous wave Doppler across the revised LVOT and prosthetic AV was 8.95 mm Hg. Her cardiac index was 3.1 L·min−1·m−2. The revised LVOT diameter could not be measured using either a midesophageal or deep transgastric view because of poor image quality and perivalvular edema. Other than a high degree atrioventricular block which required a permanent pacemaker, her perioperative course was uneventful. Fixed subvalvular aortic stenosis is a congenital disease which encompases a spectrum of anomalies ranging from a localized fibrous web of the LVOT 1–1.5 cm below the AV to a long fibrous tunnel with hypoplasia of the aortic annulus. Ventricular hypertrophy can also occur, predisposing to dynamic obstruction of the LVOT (1,2). AV insufficiency is a common associated condition, occurring in about 25% of patients (1). More than half of these patients have additional cardiac malformations, most frequently patent ductus arteriosus, ventricular septal defect, and coarctation of the aorta. The disease is progressive and recurrent, with re-obstruction after surgery in 6%–30% of patients (1,2). Permanent or transient complete heart block is a complication of subaortic obstruction repair, and may occur in up to 15% of patients (3). It appears to be related to the magnitude of the corrective procedure performed (1). In a recent study involving 53 patients undergoing a Konno procedure over a 24-year period, Suri et al. observed a 10-year survival of 86% (4). The risk factors for mortality were the duration of cardiopulmonary bypass (CPB) (hazard ratio of 1.93/h P = 0.04. and the NY Heart Association grade (hazard ratio 2.2, P = 0.04). This case report illustrates the important role of TEE before, during, and after AV surgery. Nowrangi et al. published the results of the impact of intraoperative TEE in 383 patients undergoing AV surgery for aortic stenosis at the Mayo clinic (5). In their study, intraoperative TEE modified the proposed surgery in 13% of cases. In a single-center 417-patient study in Israel, the impact of TEE was reported for 221 patients undergoing AV replacement (6). Immediate surgical corrections were required for perivalvular leak in four patients and coronary obstruction by the aortic bioprosthesis in two patients. Prolonged removal of air was necessary in 45 patients (10.8%) and in 47 patients (11.3%) TEE after CPB was pivotal in evaluating the causes of difficult separation from CPB. There are some limitations, however, in the use of TEE before AV surgery. As observed in our patient, the intraoperative gradients were lower than those reported by the transthoracic examination. This may be explained by the effect of general anesthesia on cardiac performance similar to that which has been shown in patients undergoing mitral valve surgery (7).

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