Case Report

The Sword of Damocles: An Illustrative Example of the Life-Saving Effect of the Collateral Circulation

Pascal Meier, MD
Pascal Meier, MD
ABSTRACT: There is an ongoing debate on the effective importance of the collateral network, especially in the current era, where most patients with significant coronary artery disease are revascularized, be it percutaneously or surgically; thus, people may question a significant benefit of the coronary collateral circulation. However, the presented 61-year-old male patient demonstrates an unambiguous situation of a life-saving effect of the collateral circulation. The patient presented without any angina symptoms and with only mild shortness of breath on moderate to severe exertion. A subsequent angiography revealed a complete chronic occlusion of the main coronary artery. The entire left coronary system was provided by well-developed right to left collaterals. Additionally, the patient had an 80–90% stenosis of his mid-right coronary artery (RCA). The entire blood supply to the heart had to pass this lesion to provide the RCA area and also the left anterior descending and left circumflex areas via collaterals. This extreme example illustrates the potentially lifesaving effect of the coronary collateral circulation. Obviously, the entire myocardium can in some cases be perfused entirely via one critically stenosed vessel.

Case Report. A 61-year-old male presented to his primary care physician in November 2009 because of some shortness of breath at exertion. He only suffered from shortness of breath when he was walking very fast or climbing stairs (New York Heart Association class II). He was absolutely asymptomatic until a few weeks before presentation, when he noticed some shortness of breath on exertion. Over the summer, he was splitting firewood and mowing his lawn with a push mower, but never experienced any chest pain. His cardiovascular risk factors are hypertension, hyperlipidemia and smoking (60 pack years).

On physical exam before coronary angiography, the patient presented in no acute distress. Blood pressure was 137/81 mmHg, heart rate was 65 beats/minute, and oxygen saturation was 98% on room air (pulse oxymetry). The patient’s lungs were clear to auscultation bilaterally. His cardiac exam revealed a regular rate and rhythm, no murmurs, gallops or rubs. The laboratory testing, including complete blood cell count and basic metabolic panel, were unremarkable.

His electrocardiogram showed a sinus rhythm with mild T inversions in lead V1 to V6. A transthoracic echocardiography, however, revealed a severely reduced systolic left ventricular function with global hypokinesis and an ejection fraction of 15%. A nuclear stress test indicated a large-sized, moderately severe, anterior, anterolateral and lateral reversible defect.

A cardiac catheterization was then performed, which very surprisingly in the context of the mild symptoms, showed a completely occluded left main coronary vessel. Such a picture is very rarely seen in vivo because most patient would not survive a total occlusion of such an extensive coronary distribution area. The explanation for the mildness of the patient’s symptoms was found in the RCA injection, i.e., the patient had a very well-developed collateral system from the RCA to the left coronary system. However, the RCA showed an 80–90% stenosis in the mid segment. The complete blood supply to the entire myocardium had to pass this high-degree RCA stenosis with a very narrow cross area. After the angiography, the patient was admitted to the coronary observation unit and underwent coronary bypass surgery 2 days later. He received a left internal mammary artery graft to the mid left anterior descending, a saphenous vein graft to the Ramus and a second one to the right posterolateral branch. His post-surgical course was uneventful. On March 15, 2010, around 3 months after the procedure, his left ventricular function improved to 40–45% by echocardiography, showing only mild global hypokinesis with paradoxical septal motion (consistent with post-operative state). This indicates that his myocardium had significant viability prior to revascularization, probably due to the collateral circulation. Six months after the procedure, the patient was doing fine, denying shortness of breath and angina. Discussion. Impressively enough, this patient survived a total occlusion of his left main artery. Of note, this was only possible because of a well-developed coronary collateral circulation. The collateral function was even sufficient to avoid angina symptoms. Obviously, chronic left main occlusion, even combined with a high-degree right coronary artery stenosis, is compatible with life, given a well-developed collateral system. The patient’s myocardium was clearly hanging by a thread and the tight lesion in his only remaining vessel, the right coronary artery, was the horse hair that suspended the sword of Damocles over the head of this patient.1 It provided the entire heart with blood via an impressive collateral system. This well-developed collateral system was the fragile life saver for this patient. The prognostic importance of coronary collaterals is not beyond debate. Some studies have even claimed a negative effect of coronary collaterals,2 while others have not found any relation between collateralization and outcome.3 More recent studies, on the other hand, have found a lower mortality risk in patients with well-developed collaterals.4 The confusing ambiguity of study results can be explained mainly by different collateral assessment methods used in the different studies. Often, angiographic visual assessment of collaterals was used, which is not an accurate method.5 The presented case certainly adds to the argument that the collateral circulation has life-saving effects, at least in such extreme settings. There are few case reports of chronic total left main occlusions in living patients. The question is whether the prevalence is actually that low, whether they are just not reported or whether the patients usually die before the diagnosis can be made. Even though we decided to send this patient for bypass surgery, we could argue that a complex left main intervention could be attempted after an intervention to the right coronary artery, since this might be regarded as a “protected left main intervention,” protected by a well-developed collateral circulation. The first such high-risk interventions in chronic CTO have been performed recently with success.6,7


  1. Cicero. Tusculan disputations 5.61. (original Latin text) (English translation).
  2. Koerselman J, de Jaegere PP, Verhaar MC, et al. Cardiac ischemic score determines the presence of coronary collateral circulation. Cardiovasc Drugs Ther 2005;19:283–289.
  3. Abbott JD, Choi EJ, Selzer F, et al. Impact of coronary collaterals on outcome following percutaneous coronary intervention (from the National Heart, Lung, and Blood Institute Dynamic Registry). Am J Cardiol 2005;96:676–680.
  4. Meier P, Gloekler S, Zbinden R, et al. Beneficial effect of recruitable collaterals: A 10-year follow-up study in patients with stable coronary artery disease undergoing quantitative collateral measurements. Circulation 2007;116:975–983.
  5. Meier P, Seiler C. Coronary collaterals — Too small to be eyeballed, too large to be meaningless. Am J Cardiol 2010;105:1203.
  6. Trehan V, Mehta V, Mukhopadhyay S, et al. Percutaneous stenting of chronic total occlusion of unprotected left main coronary artery. Indian Heart J 2003;55:172–174.
  7. Aoki J, Hoye A, Staferov AV, et al. Sirolimus-eluting stent implantation for chronic total occlusion of the left main coronary artery. J Interv Cardiol 2005;18:65–69; Discussion, pp. 9.
From the University of Michigan Medical Center and Veterans Affairs Ann Arbor Healthcare System, Ann Arbor, Michigan. The authors report no conflicts of interest regarding the content herein. Manuscript submitted April 20, 2010, provisional acceptance given June 23, 2010, final version accepted June 29, 2010. Address for correspondence: Pascal Meier, MD, Consultant/Attending Cardiologist, University College London Hospital, 16-18 Westmoreland Street, London, United Kingdom. E-mail: or