ABSTRACT
Myocardial ischemia after arterial switch operation is most commonly associated with imperfect translocation of coronary arteries to the neoaorta. Early post-operative myocardial ischemia is the main cause of morbidity and mortality in these patients. We present a rare case of intra-operative myocardial ischemia after ASO, detected with transesophageal echocardiography before electrocardiography changes.
Keywords: Arterial switch operation, regional wall motion abnormality, transesophageal echocardiography
INTRODUCTION
Arterial switch operation (ASO) is the procedure of choice in dextro-transposition of the great arteries (d-TGA) patients. The incidence of coronary complications after the procedure is related to coronary anatomy and difficulties in surgical technique.[1,2] The most common causes are anatomical kinking and extrinsic compression, which require immediate coronary revision. In the intra-operative period, it is difficult for the surgeon to rapidly determine the cause of myocardial dysfunction after a surgical procedure. Therefore, intra-operative transesophageal echocardiography (TEE) proved to be a very useful imaging tool for surgeons to check both the cardiac structure and function immediately after surgery.
CASE REPORT
A 6 weeks child presented with cyanosis after 3 weeks of birth. Pre-operative transthoracic echocardiography (TTE) revealed d-TGA, restrictive patent foramen ovale, patent ductus arteriosus, intact interventricular septum, unregressed left ventricle, and normal coronaries for TGA. Prostaglandin E1 infusion was started, and the patient was taken to the operation theater for ASO.
Anesthesia was induced with the inhalational agent sevoflurane and central venous catheterization, and arterial lines were secured after endotracheal intubation. Cardiopulmonary by-pass (CPB) was initiated by cannulation of the distal ascending aorta and the superior and inferior vena cava. Moderate hypothermia (25–28°C) was used during CPB.
The coronary artery buttons were implanted in the neoaortic root, and the neoaortic root was anastomosed directly to the ascending aorta. Neopulmonary artery anastomosis was performed after removal of the aortic cross-clamp. A single piece of fresh pericardium was used to reconstruct the neopulmonary artery. The CPB and aortic cross-clamp times were 138 and 72 min, respectively. On coming off CPB, TEE did not find air in the left side of the heart chamber and also the patent foramen ovale was not visualized. Regional wall motion abnormality (RWMA) was noticed in inferior territory of left ventricle [Video 1]. Again, CPB was initiated and supported for 20 minutes. However, coming off second time CPB, hypokinesia persisted in right coronary artery (RCA) territory and ST elevation in electrocardiography (ECG) was noted in lead II, III, and AvF [Figure 1]. On right coronary button inspection, ostial distortion was detected and the suture causing ostial distortion was removed. On removal of suture, hypokinesia gradually resolved [Video 2].
Figure 1.
Electrocardiography demonstrating ST elevation in lead II, III, and avF
The patient was shifted to the intensive care unit with infusion of milrinone 0.6 ug/kg and adrenaline 0.1 mg/kg. The patient was extubated on the fourth post-operative day and discharged on the 18th post-operative day without any complications.
DISCUSSION
In ASO, the surgical technique involved in transfer of coronary artery pattern is crucial. Biventricular systolic and diastolic dysfunction has been reported in patients with d-TGA after ASO.[3] Ischemic changes and acute or subacute cardiac failure after ASO usually indicate imperfect transfer of the coronary arteries to the neoaorta. The risk is high in TGA with abnormal coronary artery patterns. However, by using appropriate translocation techniques, this high risk is decreased to very low.
The prevalence of coronary events following ASO varies from 2% to 11%.[4] Residual tension, injury to the wall of the coronary artery during surgical dissection, and ostial distortion are the most common predisposing factors for proximal narrowing of the coronary arteries, resulting in myocardial ischemia. In our case, ischemia occurred because of ostial distortion of translocated RCA to the neoaorta with suture.
Detection of myocardial ischemia in the intra-operative period may be possible through the application of the surface ECG with a sensitivity of 47% to 81%,[5] but the ECG changes in ischemia come after the RWMA. An important role of TEE in post-cardiac surgery is to evaluate the adequacy of the surgical repair and assess ventricular function. TEE also helps in real-time monitoring of volume status, and it guides in selection of the inotropic agent and helps in decision making.[6,7] Segmental endocardial motion and myocardial thickening are the foundations for echocardiographic detection of myocardial ischemia. Peri-operatively, regional wall motion changes detected by two-dimensional echocardiography guide us to locate the exact coronary vessel involvement. A study by Smith et al. demonstrated that RWMAs occurs earlier and is a more sensitive indicator of myocardial ischemia than the abnormal changes detected with ECG.[8] Damodaran et al. in their study found that intra-operative TEE is one of the most sensitive modalities in the early diagnosis of myocardial ischemia, detecting RWMA within a minute after inadequate myocardial perfusion, which can be because of inadequate revascularization.[9] In echocardiography, acutely infarcted myocardium may look similar to acutely ischemic myocardium. In contrast, scar tissue presents echocardiographically as a thin, dense, and permanently akinetic or dyskinetic wall.
CONCLUSION
TEE is a very useful imaging modality for patients undergoing ASO. TEE not only guides us in detection of residual lesion but also helps us in an early detection of RWMA before ECG changes.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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