A 51-year-old man (height 174 cm, weight 78 kg) was diagnosed with a cardiac murmur in childhood. However, he did not have any further detailed cardiac examinations.
He had been suffering from chest pain since the age of 50. His chest pain was atypical with some non-specific characteristics. At this time, transthoracic echocardiography (TTE) was conducted, which showed a string-like abnormal structure in the LVOT. However, he did not follow up because he was asymptomatic. After a year, his chest pain recurred. TTE revealed the same structural abnormality again. Therefore, he underwent a detailed examination. Except for the cardiac murmur, he had no medical history and was not on any medications, and there was no family history of cardiac problems.
A physical examination revealed a Levine type III to-and-fro heart murmur in the aortic area. His blood pressure was 123/79 mmHg, pulse rate was 64 beats per minute (bpm), and his lungs were clear on auscultation. A chest X-ray showed a normal cardiac silhouette and both lungs were clear and expanded, with no infiltrates or pleural effusions. An electrocardiogram (ECG) showed non-specific changes and a normal sinus rhythm.
Transesophageal echocardiography (TEE) revealed an oval-like tissue with clean margins attached to the anterior leaflet of the mitral valve, causing an LVOT occlusion during systole (Fig. 1a). The maximum gradient pressure through the LVOT was measured at 26 mmHg with a mean gradient of 12 mmHg (Fig. 2a). The left ventricle wall motion was normal. The dimensions of the left ventricle during both systolic and diastolic phases were normal. No other cardiac anomalies were present. A diagnosis of AMVT was made based on the echocardiographic findings. Surgical treatment was recommended because of the presence of AMVT and the significant LVOT obstruction.
Surgery was scheduled for resection of the AMVT. In the operating room, after placing an arterial catheter in the right radial artery to continually measure the patient’s blood pressure, we induced general anesthesia by intravenous administration of midazolam 10 mg, fentanyl 500 μg, and rocuronium 70 mg. A central venous catheter and pulmonary arterial catheter were inserted via the right internal jugular vein. Anesthesia was maintained with oxygen, sevoflurane, and propofol. Bolus intravenous fentanyl infusion was administered as needed. After starting extracorporeal cardiopulmonary bypass (CPB), the AMVT was resected via the aortic valves (Fig. 1b). After resecting the AMVT, we began removing the CPB. We ensured the LVOT was no longer obstructed, but severe mitral regurgitation (MR) was observed on TEE. Therefore, a mitral valvuloplasty was conducted under CPB. MR ceased after mitral valvuloplasty, and subsequently, we stopped using CPB with dobutamine at 4 μg/kg/min and commenced biventricular pacing (90 bpm). The mean arterial blood pressure was maintained at 60–70 mmHg, the central venous pressure (CVP) at 10–15 mmHg, and the pulmonary arterial pressure (PAP) at 20–30 mmHg.
The total surgical duration was 313 mins, CPB duration was 108 mins, and the anesthesia duration was 414 mins.
The patient received a total of 3500 mL of lactated Ringer’s solution, 300 mL of intraoperative blood salvage, and 2 units of fresh frozen plasma during the procedure. His estimated blood loss was 1320 mL. The patient was hemodynamically stable throughout the surgery, with no abnormal findings on the ECG (Fig. 3). After the surgery, the patient was transported to the intensive care unit (ICU) without awakening or extubating.
The patient was extubated 6 h after being transported to the ICU. His hemodynamic state was stable with dobutamine at 0.6–1.3 μg/kg/min. There was no abnormity of the mitral valves including mitral regurgitation, and the maximum gradient pressure through the LVOT was measured at 4 mmHg with a mean gradient of 1 mmHg (Fig. 2b). Dobutamine was stopped on the second postoperative day. He responded well to treatment and was discharged 18 days after surgery.
