Hypotension After Arterial Switch: Coronary or Something Else?
3.5 kg term neonate with d-transposition and intact ventricular septum underwent arterial switch with coronary transfer. Eight hours later: HR 165/min, BP 62/38 mmHg, CVP 12 mmHg, LA pressure 14 mmHg, mixed venous saturation 48%, lactate 6.8 mmol/L and rising, urine 0.5 mL/kg/h. Echocardiogram shows LVEF 45%, no tamponade, trivial neo-aortic regurgitation, and no residual shunt. ECG shows ST elevation in leads II, III, and aVF with new Q waves in III. Chest tube output is 2 mL/kg/h.
1. What is your differential diagnosis and immediate bedside plan?
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Differential: coronary insufficiency from kinking, compression, or thrombosis; vasoplegia or sepsis; adrenal insufficiency; tamponade (unlikely with no fluid but consider localized clot); residual shunt or obstruction; arrhythmia; air embolism; anemia or hypocalcemia.
Immediate plan:
- Confirm airway, ventilation, oxygenation, and sedation; check blood gas, glucose, ionized calcium, potassium, hematocrit, platelets, coagulation, ACT, and lactate trend.
- Repeat focused echo for function, filling, pericardial fluid, shunt, and coronary flow; repeat ECG and troponin.
- Treat low diastolic pressure: norepinephrine or vasopressin to raise SVR and coronary perfusion; avoid excessive tachycardia; correct anemia and calcium.
- If cardiac output is low, add inotropy cautiously; milrinone may worsen vasodilation.
- Obtain cultures and consider sepsis, but do not let that delay treatment of ischemia.
- Call the surgeon and cath lab early; keep ECMO on standby.
2. How do you distinguish coronary insufficiency from vasoplegia at the bedside?
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Vasoplegia typically gives a wide pulse pressure, low SVR, brisk capillary refill, high or normal mixed venous saturation, and a hyperdynamic, underfilled ventricle; lactate may rise from poor distribution. Coronary insufficiency gives a narrow pulse pressure, low mixed venous saturation, elevated filling pressures, regional wall motion abnormality, ST-T changes, troponin release, and poor response to vasodilation. This infant has BP 62/38 (narrow pulse pressure), SvO2 48%, rising lactate, and inferior ST elevation, so coronary ischemia is the leading diagnosis. Echo LVEF 45% is not reassuring; look for regional akinesis and coronary flow. A vasoplegic picture with high SvO2 and wide pulse pressure would push me toward volume, norepinephrine, and sepsis treatment instead.
3. When would you return to the operating room, go to the catheterization lab, or activate ECMO?
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If he is unstable with suspected coronary compromise, take him to the OR for exploration and possible coronary revision; bring ECMO cannulas and a perfusionist. If he is stable enough and the anatomy is unclear, cath lab can define coronary kinking or thrombosis and allow intervention. Activate ECMO if he remains hypotensive with worsening acidosis despite maximal support, or if he arrests and cannot be stabilized; central cannulation is usual after sternotomy. Do not wait for a perfect diagnosis if end-organ injury is progressing. The choice depends on team availability and the likelihood of a correctable lesion.