A 68-year-old woman (body weight, 48 kg; height, 158 cm) was referred to our emergency department for acute-onset chest and back pain. On arrival, her vital signs were as follows: respiratory rate, 17 breaths/min; temperature, 36.4 °C; blood pressure, 94/56 mmHg; heart rate, 73 beats/min; oxygen saturation level, 99% in ambient air; and Glasgow Coma Scale score 15. Physical examination revealed no heart murmur and normal respiratory sounds. A 12-lead electrocardiogram showed no evidence of acute coronary syndrome. Her medical history included Stanford type B aortic dissection, hypertension, and rheumatoid arthritis controlled with anti-rheumatic drugs and alternate-day oral corticosteroids (prednisolone 5 mg per dose). Computed tomography (CT) revealed thrombosed AAD from the aortic root to the renal arteries, no aortic rupture, and no malperfusion. The ascending aortic maximum short diameter was 39 mm, and the maximum thickness of the thrombosed false lumen was 4 mm (Fig. 1). Transthoracic echocardiography (TTE) revealed no evidence of cardiac tamponade, aortic valve insufficiency, or other significant valve diseases. Her vital signs were stable; therefore, an urgent operation at a later date for AAD was planned. Preoperative blood pressure control was performed in our intensive care unit, in combination with bed rest, to prevent recurrent aortic events. Her systolic blood pressure was maintained between 90 and 110 mmHg with continuous infusion of a calcium antagonist (nicardipine 0.3–1.2 µg/kg/min). Her heart rate was between 80 and 100 beats/min, and oxygen saturation was 98% at 2 l/min oxygenation with a nasal cannula.
A day after the onset of aortic dissection, cardiac auscultation revealed a Levine 2/6 systolic murmur at the apex with no diastolic component. Subsequent investigation using TTE led to the detection of SAM of the mitral valve. TTE revealed LV hypovolemia, LV outflow tract (LVOT) obstruction due to SAM without LV hypertrophy (LVH), and interventricular septal (IVS) bulging due to a narrow aorto-mitral angle of 106.4° (Fig. 2a, b). The basal IVS thickness was 18.1 mm. The LV wall motion was hyperkinetic, with an ejection fraction of 81.7%. The peak flow velocity in the LVOT was 6.25 m/s. Abnormal laboratory data included hyponatremia (serum Na: 115.9 mEq/l), and her urine output per day was approximately 3000 ml. An adrenocorticotropic hormone stimulation test revealed suspected relative adrenal failure due to physical stress after acute aortic dissection. The systolic heart murmur due to SAM tended to improve with heart rate control to between 60 and 70 beats/min with beta-blocker therapy (landiolol hydrochloride 2 µg/kg/min) and infusion load.
The aortic false lumen was still thrombosed, but the ascending aortic maximum short diameter was dilated from 39 to 45 mm and the maximum thickness of the thrombosed false lumen increased from 4 to 8 mm in the preoperative CT scan at 14 days after the onset of aortic dissection. In case of postoperative unstable hemodynamics following the physical stressful aortic repair, concomitant IVSM during the ascending aortic replacement was planned for the prevention of SAM. The patient’s adrenal insufficiency recovered gradually with alternate-day oral corticosteroid (prednisolone 5 mg per dose); therefore, we performed the operation 19 days after the onset of aortic dissection. In the operating room, transesophageal echocardiography under total anesthesia still showed SAM. Following median sternotomy, IVSM and ascending aortic replacement with a one-branched J Graft Shield Neo 26-mm Dacron graft (Japan Lifeline Inc., Tokyo, Japan) were performed under usual cardiopulmonary bypass with cannulation via the right femoral artery and right atrium. In the operative findings, there was no pericardial effusion that could compress the LV structure. During the IVSM procedure, the needle stick technique (NST) (Fig. 3a, b) was applied because of easy, quick, and protective exposure to the IVS muscle to be resected. Briefly, three 21-gauge needles were inserted into the interventricular septum just below the aortic valve annulus beyond the far side of the septal bulge. One needle was inserted beneath the mid portion of the right coronary cusp to provide a right-side margin, the second was inserted beneath the commissure of the right and left coronary cusps to provide a left-side margin, and the last was inserted between the previous two as a guide for the thickness of the myectomy (Fig. 3a). The resected muscle weighed 278 mg in total (Fig. 3c). The cardiopulmonary bypass was easily weaned. Postoperative TTE showed improved systolic flow velocity in the LVOT of 0.93 m/sec and no evidence of SAM (Fig. 4a, b). The patient was discharged from our hospital 22 days after the operation, with no major complications.