Reversed flow in internal mammary artery conduit and vertebral artery with left subclavian artery occlusion causing angina and vertigo. The coronary--subclavian steal syndrome

Coronary subclavian steal syndrome

PURPOSE OF REVIEW

Coronary subclavian steal syndrome (CSSS) is the reversal of blood flow in an internal mammary artery bypass graft that results in coronary ischemia. CSSS is an uncommon but treatable cause of coronary ischemia. In this review, we highlight the historical background and epidemiology of CSSS, common clinical presentations, diagnosis of CSSS and management strategies for relieving ischemia. We also present a case report to illustrate the complexity of CSSS and percutaneous management using current technology.

RECENT FINDINGS

Most commonly, CSSS results from atherosclerotic stenosis of the subclavian artery and occurs in 2.5-4.5% of patients referred for coronary artery bypass grafting (CABG). All patients referred for CABG should have bilateral noninvasive brachial blood pressures checked to screen for the underlying subclavian stenosis. A review of 98 case reports with 128 patients demonstrated a diverse clinical presentation of CSSS, including acute myocardial infarction, unstable angina and acute systolic heart failure. Resolution of CSSS symptoms has been reported with both surgical and percutaneous revascularization. Long-term patency with either revascularization strategy is excellent. Percutaneous revascularization is largely considered the first-line therapy for CSSS and can be safely performed prior to CABG to prevent CSSS.

SUMMARY

CSSS should be suspected in patients presenting with angina, heart failure or myocardial infarction after CABG. Successful amelioration of CSSS symptoms can be safely and effectively performed via percutaneous revascularization.

Coronary-subclavian steal syndrome presenting with ventricular tachycardia

Coronary-subclavian steal through the left internal mammary graft is a rare cause of myocardial ischemia in patients who have had a coronary bypass surgery. We report a 70-year-old man who presented with sustained monomorphic ventricular tachycardia 5 years after the surgical creation of a left internal mammary to the left anterior descending artery. Cardiac catheterization illustrated that the left subclavian artery was occluded proximally and that the distal course was visualized by retrograde filling through the left internal mammary graft. Clinical ventricular tachycardia was reproducibly induced with a single ventricular extrastimulus, and antitachycardia pacing terminated the tachycardia. Restoration of blood flow by way of a Dacron graft placed between the descending aorta and the subclavian artery resulted in the total relief of symptoms. Ventricular tachycardia could not be induced during the control electrophysiologic study after surgical revascularization.

Myocardial thievery: the coronary-subclavian steal syndrome

Coronary-subclavian steal syndrome entails the reversal of blood flow in a previously constructed internal mammary artery coronary conduit, which produces myocardial ischemia. The most frequent cause of the syndrome is atherosclerotic disease in the ipsilateral, proximal subclavian artery. Although coronary-subclavian steal was initially reported to be rare, the increasing documentation of this phenomenon and its potentially catastrophic consequences in recent series suggests that the incidence of the problem has been underreported and that its clinical impact has been underestimated. We review the causes and background of coronary-subclavian steal; methods of preventing, diagnosing, and treating it; and the potential influence of various treatment regimens on long-term survival and the likelihood of late adverse events in patients with coronary-subclavian steal syndrome.

Regulation of p21WAF1/CIP1 expression through mitogen-activated protein kinase signaling pathway

p21WAF1/CIP1 is a cyclin-dependent kinase inhibitor whose expression in mammalian tissues is highly induced in response to stress as well as during normal development and differentiation. Induction of p21WAF1/CIP1 in response to DNA damage occurs through a transcriptional mechanism that is dependent on the activation of the tumor suppressor protein p53. Recent evidence indicates that p21WAF1/CIP1 can also be induced independently of p53, but the signal transduction mechanisms involved in regulating p21WAF1/CIP1 expression in these situations have not been elucidated. In this study, we have addressed the role of the mitogen-activated protein kinase signaling pathway in the induction of p21WAF1/CIP1 in response to growth factor treatment. Using an experimental approach involving cotransfection of a p21WAF1/CIP1 promoter-luciferase construct with a variety of plasmids expressing dominant positive or dominant negative mutant proteins involved in this signaling pathway, we provide evidence to support a role for mitogen-activated protein kinase in the transcriptional activation of p21WAF1/CIP1 by growth factor stimulation.