When an LAD steal event occurs intraoperatively, palpation and clinical observation won't catch it. Transit-time flow measurement will.
~2.3-6.8% of patients undergoing CABG have concurrent subclavian artery stenosis - most undetected before surgery.1
Coronary-Subclavian Steal Syndrome (CSSS) is an uncommon and underrecognized complication in CABG. In the presence of proximal left subclavian artery stenosis, blood can reverse through the LIMA graft, stealing flow from the LAD territory.
CSSS typically presents months or years after surgery. Intraoperative onset is exceedingly rare, with only a handful of documented cases worldwide. When it does occur, the abrupt onset and non-specific signs make diagnosis nearly impossible without objective flow data.
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In this case from Peking University First Hospital, a 65-year-old man with unstable angina underwent urgent off-pump CABG. The LIMA-LAD anastomosis and sequential SVG were completed uneventfully. Then, during proximal SVG anastomosis, the patient developed refractory ventricular fibrillation. Multiple defibrillations failed. Emergency CPB was established.
The Medistim MiraQ™ system was deployed. TTFM returned an unambiguous finding.
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KEY PRINCIPLES
Screen for subclavian disease before every CABG. A bilateral upper-limb blood pressure difference >15 mmHg is a simple, practical indicator of subclavian stenosis, especially valuable in urgent cases where full vascular workup is not possible.
Consider bilateral arterial pressure monitoring. In this case, exclusive left radial monitoring masked true central aortic pressure, potentially contributing to the hemodynamic crisis.
When subclavian disease cannot be excluded, consider alternative conduits such as the right IMA or SVG to avoid compromised LIMA inflow.
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GUIDELINE CONTEXT
TTFM carries a Class IIa, Level B recommendation in the 2018 ESC/EACTS Guidelines on Myocardial Revascularization and the authors argue its value is highest precisely in high-risk, unstable, and emergency CABG cases.
This case is one of the few documented instances of intraoperative CSSS ever reported. The diagnosis was made solely on the basis of TTFM data, in real time, under emergency conditions.
Gong, Zhang & Wang. Intraoperative diagnosis and successful management of acute coronary–subclavian steal syndrome during off-pump coronary artery bypass grafting: a case report. Front. Cardiovasc. Med., 15 May 2026. Sec. Cardiovascular Surgery. DOI: 10.3389/fcvm.2026.1766112
