J INVASIVE CARDIOL 2009;21:e101–102 Case Presentation. A 73-year-old male was admitted generally unwell to our hospital in October 2007. Clinically, he was in atrial fibrillation and had signs and symptoms of pulmonary edema. He had a long history of ischemic heart disease, hypertension, hyperlipidemia and had been diagnosed with heart failure 3 months prior to his admission. He underwent coronary artery bypass grafting (CABG) surgery twice. During his first operation in 1992, saphenous vein grafts (SVGs) were anastomosed to the left anterior descending (LAD), circumflex (Cx) and right posterior descending (PD) arteries. In 1999, cardiac catheterization showed considerable left main disease, occlusion of the SVGs to the LAD and Cx, and proximal stenosis of the SVG to the PD artery. There was no evidence of aortic stenosis at the time. Re-do CABG was thus performed. This involved the anastomosis of the right internal mammary artery to the intermediate artery and the grafting of SVGs to the LAD, right PD (at the site of the previous graft) and (as a jump graft) to the first and second Cx arteries. During his recent admission, transesophageal echocardiography revealed significantly reduced left ventricular systolic function (ejection fraction 20–25%) and severe aortic stenosis (valve area 0.8 cm2) secondary to extensive cusp calcification. A low-dose dobutamine stress echocardiogram further verified the severity of the stenosis. Cardiac catheterization was thus carried out to evaluate the patency of his grafted and native vessels for a prospective percutaneous aortic valve replacement. Interestingly, dynamic narrowing of the mid-segment of the SVG graft to the PD artery was observed during diastole (view A in accompanying figure), with the vessel assuming its normal patency during systole (view B). Angiographically, this “milking effect’”produced a significant degree of stenosis to the graft, with minimum vessel diameter at the end of diastole. Discussion. Dynamic compression of native coronary vessels is well known to occur during systole in the context of myocardial bridging.1Systolic narrowing of bypass grafts (left internal mammary artery to the LAD and SVG to right PD arteries) has also been reported.2 In contrast, reports of this event occurring in native vessels during diastole are scarce.3,4 Furthermore, to the best of our knowledge, only a single case report exists that refers to bypass grafts; this describes the diastolic segmental compression of a SVG to the right coronary artery.5 Given the surgical history of our patient, we hypothesize that the diastolic “milking effect” exhibited by the vein graft to the PD artery may be attributed to fibrotic tethering of the vessel to the chest wall or nearby structures and extrinsic compression by the enlarging right ventricle. A similar mechanism has also been described by Chokshi and Meyers to explain the angiographic results in their patient.5 Though constrictive pericarditis has previously been implicated in the diastolic obliteration of an obtuse marginal branch, echocardiographic investigations excluded such a possibility in our patient.4 The management of this phenomenon poses a challenge. The use of medical and surgical treatments, as well as percutaneous coronary intervention (PCI) in treating the effects of vessel compression in myocardial bridges has been reviewed,1 with intracoronary stenting showing promising results.6 However due to the rarity of this event in bypass grafts, no clear guidance exists. Our patient had a high surgical risk associated with his cardiac morbidity. He had thus been scheduled for a percutaneous valve replacement procedure in combination with stenting of the affected graft. Unfortunately he suffered a fatal acute coronary event shortly after his catheterization and prior to implementing his suggested management plan. We were thus unable to obtain supplementary data with further investigations or to quantify any ischemic effects of this “milking phenomenon”. Conclusion. Dynamic compression of grafted vessels at different parts of the cardiac cycle may be recognized as a new long-term complication of CABG. This may result in myocardial ischemia with subsequent implications for patient management. More research is required to identify the true incidence and underlying mechanisms of this event and the utilization of PCI as a potential therapeutic modality. ____________________________ From Whittington Hospital NHS Trust, London, United Kingdom, and Nicosia General Hospital, Nicosia, Cyprus. The authors report no conflicts of interest regarding the content herein. Manuscript submitted December 12, 2008, provisional acceptance given March 2, 2009, and final version accepted March 30, 2009. Address for correspondence: Theodoros Christophides, MD, Department of Medicine, Whittington Hospital NHS Trust, Magdala Avenue, London, N19 5NF, United Kingdom. E-mail: firstname.lastname@example.org
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