Coronary Ostial Stenosis

Coronary ostial stenosis is narrowing within about 3 mm of the origin of a coronary artery from the aorta. It can be isolated or part of a left main or aortic root process. It restricts flow at rest or with exertion and is easily missed on angiography.

It is uncommon. Causes are atherosclerosis of the aortic root, syphilitic aortitis, Takayasu arteritis and other vasculitis, radiation, aortic valve surgery (cardioplegia cannula injury, valve prosthesis or sewing ring obstruction, reimplantation stenosis), congenital ostial hypoplasia or atresia, fibromuscular dysplasia, spasm, and extension of calcific aortic valve disease. After transcatheter aortic valve implantation, the valve frame or a displaced calcified leaflet can obstruct an ostium.

Most of these patients are young or middle aged with few risk factors, apart from atherosclerotic disease. Prognosis is poor without revascularisation, particularly with left main involvement.

Pathophysiology.

Atherosclerotic plaque of the aortic wall spreads into the ostium. In syphilis, endarteritis of the vasa vasorum and scarring contract the ostium. In Takayasu arteritis, granulomatous inflammation thickens the aortic wall and ostia.

Surgical injury follows cardioplegia delivery through direct ostial cannulas or bypass of an ostium by a prosthetic ring, giving fibrous stenosis weeks to years afterwards.

Reduced ostial flow produces ischaemia and sudden death in severe left main involvement. Exertional syncope and arrhythmia may occur.

Angina, exertional dyspnoea, syncope, acute coronary syndrome, heart failure or sudden death. Features of the cause: aortic regurgitation murmur and wide pulse pressure (syphilis), absent or asymmetric pulses and bruits (Takayasu arteritis), previous aortic valve or root surgery, previous thoracic radiotherapy, or recent transcatheter valve implantation. Hypertension and weak limb pulses suggest Takayasu arteritis.

• Coronary angiography: a stenosis at the ostium. Engagement of the catheter can damp the pressure trace or cause "ventricularisation" (loss of the dicrotic notch), and non-selective injection may be needed. Multiple projections, including an aortic root injection, help.
• Intravascular ultrasound is the most reliable test for ostial and left main lesions: minimal lumen area under 6.0 mm2 in the left main (under 4.5 mm2 is used in some populations) is significant. Ostial pressure wire measurements are unreliable because the catheter obstructs the origin.
• CT coronary angiography or MRI for the ostium, aortic root wall thickening, calcification and aortic involvement. PET-CT shows active arteritis.
• Aortic imaging, ESR, C-reactive protein and syphilis serology (treponemal antibody, confirmed with a non-treponemal test such as RPR with titre). Lumbar puncture when neurological or ocular features are present. HIV test.
• Echocardiography for aortic regurgitation and ventricular function.

Differential diagnosis.

• Catheter induced spasm of the ostium.
• Coronary dissection extending from the aorta.
• Embolic ostial occlusion.
• Congenital anomalies of origin and acute coronary occlusion by a prosthetic valve component.

Treat the cause.

• Syphilitic aortitis: benzathine benzylpenicillin 2.4 million units intramuscularly once weekly for 3 weeks. With penicillin allergy, doxycycline 100 mg orally twice daily for 28 days (desensitisation is preferred in pregnancy). Cover the first dose with prednisolone 40 to 60 mg daily for 3 days, starting the day before, to reduce the Jarisch-Herxheimer reaction, which can precipitate coronary compromise. Treat HIV and test and treat partners. Revascularisation is not delayed when ischaemia is severe.
• Takayasu arteritis: prednisolone 0.5 to 1 mg/kg orally daily (usually 40 to 60 mg) for 4 weeks, tapered over 6 to 12 months to the lowest effective dose; add methotrexate 10 to 25 mg orally once weekly with folic acid 5 mg weekly (avoid when eGFR is under 30 mL/min/1.73 m2; full blood count and liver tests every 2 weeks for 2 months, then every 3 months) or tocilizumab 162 mg subcutaneously weekly (check neutrophils, platelets and liver tests; exclude tuberculosis first). Defer elective revascularisation until inflammation is controlled, because restenosis is high in active disease. Co-trimoxazole 960 mg three times each week and bone protection during prolonged steroids.
• Atherosclerosis: aspirin 75 to 100 mg daily and atorvastatin 40 to 80 mg daily (LDL cholesterol under 1.4 mmol/L), with blood pressure, glucose and smoking control.

Revascularisation.

• Isolated ostial right coronary or left anterior descending lesion: drug eluting stent with 1 to 2 mm protruding into the aorta and flaring of the ostium under intravascular ultrasound direction, using a technique that avoids stent displacement (Szabo or wire marking techniques). Avoid deep intubation of the guide catheter. Post-dilate at high pressure.
• Left main ostial disease: bypass surgery is favoured when anatomy is complex, in younger patients, or in arteritis. Percutaneous intervention is acceptable for isolated, simple left main lesions in patients at high surgical risk.
• Prosthetic valve or surgical obstruction: re-operation, or percutaneous stenting for suitable ostia.
• Post-transcatheter aortic valve obstruction: urgent stenting with a wire placed before valve deployment, or bypass grafting.
• After stenting: aspirin 75 to 100 mg daily with ticagrelor 90 mg twice daily (or clopidogrel 75 mg daily) for 12 months after an acute coronary syndrome and 6 months otherwise. Pantoprazole 40 mg daily.

Monitoring. Symptoms and ECG at 4 weeks and 3 months, imaging of the ostium at 6 to 12 months (restenosis is common), ESR and C-reactive protein every 4 to 8 weeks in arteritis, repeat syphilis serology (RPR titre) at 6, 12 and 24 months.

Referral and escalation. Refer all suspected cases to a centre with interventional and cardiac surgical capability. Urgent referral for left main involvement, syncope, ventricular arrhythmia or an acute coronary syndrome.

Special groups.

• Pregnancy: doxycycline is avoided, so desensitise to penicillin; steroids are continued; delivery in a cardio obstetric centre.
• Children and young adults: congenital ostial stenosis needs surgical unroofing or reimplantation.
• Kidney impairment: contrast sparing; adjust methotrexate and tocilizumab monitoring.
• Region specific: syphilis and Takayasu arteritis are important in the differential for young patients with ostial disease.