Contrast echocardiography during exercise stress in a case of congenitally corrected transposition of the great arteries after double-switch operation

Excerpt

A 32-year-old woman, who underwent a double-switch operation combined with the Mustard and Rastelli procedure at age 9 years for congenitally corrected transposition of the great arteries, was referred to our hospital for evaluation of dyspnea on exertion. She exhibited a normal percutaneous oxygen saturation (SpO₂) level (98% on room air) at rest, and her blood biochemistry tests exhibited a mild brain natriuretic peptide elevation (48.7 pg/ml). Transthoracic echocardiography revealed right ventricular (RV) hypertrophy and no left ventricular (LV) enlargement, with end-diastolic/systolic dimensions of 39/29 mm, and an ejection fraction of 52% (Fig. 1A). Significant acceleration with maximum flow velocity of 4.0 m/s was observed in the Rastelli conduit (Fig. 1B). The walking test induced breathlessness within a few minutes, lowering her SpO₂ to 90%. The agitated saline contrast echocardiography test (on exercise stress echocardiography using a spine ergometer) revealed a larger leakage from the Mustard route into the right atrium during exercise than at rest (Fig. 1C, Movie-1), with increased flow acceleration in the Rastelli conduit, rising to approximately 6 m/s. Dyspnea occurred shortly after exercise initiation, and the load was terminated at 25 W as her SpO₂ dropped to 90% within 3 min. Transesophageal echocardiography at rest indicated left to right shunting between the pulmonary veins-to-LV route and the Mustard route (Fig. 1D). The Valsalva maneuver further demonstrated bidirectional shunting (Fig. 1E, Movie-2). The agitated saline contrast echocardiography test revealed significant right to left shunting (RLS) via the Mustard route into the aorta (Fig. 1F). Cardiac magnetic resonance imaging revealed severe stenosis at the proximal end of the Rastelli conduit (Fig. 1G). Exercise-induced RLS occurred via a baffle leak in the Mustard route, causing hypoxemia and contributing to symptoms. A surgical RV outflow tract reconstruction and closure of atrial-level communication was scheduled. Intraoperative findings demonstrated severe calcification, sclerosis, and stenosis of the Rastelli conduit (Fig. 1H). However, baffle leak repair was abandoned because of coronary artery injury during adhesion stripping. Postoperatively, dyspnea on exertion and the decreased SpO₂ improved. The Rastelli operation is a low-risk procedure with regard to early mortality. However, conduit obstruction is inevitable in the long term [1, 2]. Baffle leakage in the Mustard operation is a factor of paradoxical cerebral infarction and cyanosis due to RLS [3]. The pressure difference between the left and right side of the baffle can be reversed by exercise in the setting of pathologically elevated atrial pressure; thus, this case was diagnosed by exercise stress echocardiography combined with an agitated saline contrast echocardiography test.

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