Iatrogenic left main coronary artery stenosis following aortic and mitral valve replacement.

Iatrogenic coronary artery disease following prosthetic valve implantation is a rare complication. This may result from mechanical injury in the intraoperative period. The use of balloon tip perfusion catheter presumably provides the initial insult with local vessel wall hypoxia. Once the diagnosis of coronary ostial stenosis is established, the procedure of choice is coronary artery bypass surgery. We report a case of a young lady who underwent aortic and mitral valves replacement for infective endocarditis. She was then diagnosed with ostial left main stem coronary stenosis after presenting with atypical symptoms. The patient eventually underwent coronary artery bypass surgery.

INTRODUCTION

Left main coronary artery stenosis is a serious condition and can result in patient death. Early recognition and intervention is vital. Postoperative valve replacement is rarely complicated by left main coronary artery stenosis.[1]

Symptoms are often clear and patient can develop chest pain during exercise or at rest. The onset of angina usually occurs within 2-6 months after valve replacement. Patient can also present with pulmonary edema and acute left ventricular dysfunction.[2]

In this report, we describe a case of mitral and aortic valve replacement in a young patient complicated by symptomatic critical left main coronary artery stenosis.

CASE REPORT

A 37-year-old female patient with past history of rheumatic heart disease involving mitral and the aortic valves was diagnosed with Streptococcus Viridans bacterial endocarditis causing both moderate mitral and severe aortic regurgitation with multiple embolic events and abscess formation. The patient underwent aortic and mitral valve replacement. The procedure was done using 1.8 Lof antegrade and retrograde blood cardioplegia. At surgery the aortic valve showed redundant vegetations attached to the non-coronary cusp with erosion and abscess formation between the right and the non-coronary commisures in the area of the perimembranous septum. There was also abscess formation below the none and left coronary commisures, almost penetrating the aortic root. These were debrided and painted with Iodine. The mitral valve also showed vegetations in both commisures and excess fibrosis and thickening of both cusps. The mitral valve was replaced using 27 St. Jude's prosthesis and the aortic valve was replaced using 21 St. Jude's prosthesis (St. Jude Medical Company).

Postoperative course and hospital stay was uneventful and she was discharged home on aspirin, atorvastatin, metoprolol, and warfarin. One month following surgery, she started to have central- and left-sided chest pain, progressively worsening over few months. Her symptoms were atypical for angina as they were mostly non-exertional and associated with palpitations and flushing. Her resting electrocardiography (ECG) showed no evidence for ischemia and her echocardiography revealed normal left ventricular function with normally functioning prostheses.

A 24-hour Holter monitor for ST segment changes was done 6 months later and revealed marked ST segment depression whenever she had chest pain. She underwent cardiac catheterization and coronary angiography [Figures 1 and 2] which showed short left main coronary artery with 90% concentric stenosis and significant pressure damping upon cannulation of the left main stem.

Figure 1

Coronary angiogram in the left anterior oblique caudal view showing significant ostial left main stem coronary stenosis (arrows). Aortic and mitral prosthetic valves are shown as well

Figure 2

Coronary angiogram in the anteroposterior (AP) view showing significant ostial left main stem coronary stenosis (arrows). Aortic and mitral prosthetic valves are shown as well

The patient was referred for surgery and she underwent coronary artery bypass surgery consisting of left internal mammary artery to the left anterior descending artery and a saphenous vein graft to the diagonal branch and left circumflex. There were no postoperative complications.

DISCUSSION

Iatrogenic coronary artery disease following prosthetic valve replacement has been previously reported. This may result from mechanical injury or direct trauma to the vessels usually from the use of coronary perfusion cannulae producing immediate dissection and myocardial infarction during the intra-operative period.[3] Thromboembolism to the coronary arteries as late complication is also well documented.[4]

The usual complication of coronary ostial stenosis associated with intimal hyperplasia has been infrequently recognized clinically. The use of balloon tip perfusion catheter presumably provides the initial insult with local vessel wall hypoxia through compression of vasa vasora perhaps in the conjunction with a relatively high perfusion pressure. But the appearance of ostial narrowing in the right coronary artery argues against perfusion as the only etiologic factor. Intimal-medial separation related to direct trauma from manipulation with subsequent hyperplasia is also a consideration.[1] Turbulent flow around the prosthetic valve has been conjectured to produce intimal hyperplasia in the aorta. Intimal thickening in the aortic root including the area of the coronary ostia in patients who died late after surgery has been described.[5]

Symptoms are often clear and overwhelming: Chest pain during exercise or at rest, sudden onset of left ventricular failure without clear cause, and acute pulmonary edema.[6] In our case, the patient symptoms were atypical (short episodes of non-exertional chest pains with palpitations) and that was the major cause in delaying the diagnosis.

The rapid appearance of angina postoperatively presumably correlated with the anatomic narrowing of the coronary ostia by intimal proliferation.[7] In our case, the most likely cause of her left main stenosis post surgery was direct injury during left main cannulation using ante grade cardioplegia.

It is important to recognize that valve prosthesis may obscure the ostium of either coronary artery and coronary angiographic multiple injections in various positions may be required to demonstrate the lesion. Once the diagnosis of coronary ostial stenosis is established the procedure of choice is oartocoronary anastomosis.[5]

Coronary artery stenosis after prosthetic valvular replacement can be avoided by not cannulating the coronary ostia for antegrade cardioplegia, but instead using retrograde delivery as an alternative method for myocardial perfusion during open heart surgery.[8] In the same paper they suggested that there might be a genetic predisposition for developing such lesion, as 70% of the affected population in their series had an epsilon 4 allele apolipoprotein E genotype compared to 10-15% in control group.

CONCLUSION

Left main stem stenosis is a rare but lethal condition following valve replacement surgeries. The etiology of such condition is most likely related to ostial injury during cannulation for antegrade cardioplegia. Early recognition, diagnosis, and treatment are vital for patient survival.