By definition, a single coronary artery (SCA) is a congenital coronary artery anomaly (CCAA) with anomalous coronary artery (CA) connection to the aorta/systemic circulation in which all of the coronary blood flow is provided by an artery that arises by one ostium from an arterial trunk [1,2].

Although this condition, accounts for less than 3% of all CCAA, affecting 0.0024%–0.066% of those undergoing coronary angiography and 0.019%–0.4% of the general population, SCA carries both natural and/or procedural risks that may affect normal life expectancy, causing sudden cardiac death in 23% of carriers. In more than 40% of the reported cases, SCA is associated with other complex congenital anomalies [2–5].

We present a patient with unstable angina pectoris who underwent successful combined coronary artery bypass grafting (CABG) and aortic valve replacement (AVR) surgery for moderate aortic stenosis, in a presence of Lipton’s R-III type of isolated SCA [6].

Since we could not find such preoperative and surgical characteristics in the available literature, we found it useful to emphasize some natural and procedural risks and to distinguish casual from causal in this extremely rare clinical and surgical scenario [7].

The combination of underlying pathologies, clinical presentation, and surgical treatment in the case we presented here is extremely rare. Having performed an extensive literature review, we could not find a single case report of an adult patient with isolated SCA, CA disease, and AoV stenosis submitted to combined CABG and AVR surgery. Katsetos have reported a similar case in 2003, but in a patient with AoV insufficiency [8]. Kawano et al. also reported AVR for AoV insufficiency but without CABG [9,10]. In four other cases, AVR was done in patients with SCA and associated congenital anomalies [8,9].

Clinical or morphologic evidence of myocardial ischemia, as a natural risk, is present in about 15% of isolated SCA cases, without any angiographic evidence of atherosclerotic CA disease. On the other hand, 40%–45% of isolated SCA cases have significant atherosclerotic narrowing of one or more major epicardial CA [11]. Rigatelli found that benign forms of CCAA, in the absence of significant known risk factors, do not accelerate CA atherosclerosis [12]. Accordingly, the isolated SCA in our case is probably just a casual finding in a presence of CA atherosclerosis. On the other hand, Lo Rito has found that RCA with anomalous aortic origin fails to expand its lumen and increase flow at incremental loading conditions, suggesting that this may be the anatomic substrate responsible for the reduction of coronary blood flow reserve, regardless of inability to demonstrate inducible ischemia on the exercise stress testing [13]. Accordingly, if not related to atherogenesis, SCA may be a reason for different reactivity of the CA network, facilitating the clinical presentation of accompanying atherosclerotic CA disease.

Beyond SCA and CA disease, the third part of this complex underlying pathology was moderate AoV stenosis. In a series of 1099 consecutive patients submitted to AoV surgery, Naito found CCAA in 4% of cases, but none of them with SCA. They believe that younger patients, who were referred for AoV surgery, had a certain congenital component in their AoV disease, leading towards a higher prevalence of anomalous coronary ostium, thus giving a possible causal link for these pathologies. He could not find any significant correlation between CCAA and functional AoV lesions, but they did so for the root-type aortopathy [14]. As the risk factors for atherosclerosis and degenerative disease of the trileaflet AoV are similar [15], it is reasonable to consider that the presence of SCA in our case is only a casual finding. However, the complex embryological blueprint is linking the aortic root and proximal CAs, thus making different anomalous origins and courses of CAs commonly associated with aortic root malformations and patterning anomalies of great arteries [16,17]. Accordingly, a slightly dilated periostial aortic wall, forming a kind of secondary sinus within the right sinus of Valsalva, is probably congenital (see Figs. 4 and 2C). Its presence may subsequently induce adaptive modification and degenerative changes of the AoV, by changing the stress loading of the aortic valve leaflets [9,15,18]. Thus, again, the line between casual and causal becomes obscure.

Invasive coronary angiography remains the gold standard in patients with a high clinical likelihood of CA disease but has limited ability in demonstrating the anatomy of complex CCAA. Accordingly, whenever it accidentally reveals the presence of CCAA, an additional preoperative MDCT coronary angiography is an excellent complementary technique to precisely delineate the origin, branching patterns, and the course of the anomalous arteries [19]. In our case (Fig. 2), MDCT revealed three important SCA features, being specific procedural risks: 1) very short common mixed trunk-bearing possible difficulties during the direct cardioplegia delivery, 2) anterior LAD course-being prognostically better than interarterial course but in the risk of injury during the epicardial pacing, and 3) retroaortic RCx course-running very close to the aortic root and in the risk of injury during and after AoV implantation.

Isolated SCA is an extremely rare, neither benign nor malignant form of CCAA, carrying both the natural risk for sudden cardiac death of 23% and significant procedural risks if casually and/or causally associated with CA and/or AoV diseases. As for all other CCAA, both invasive and MDCT coronary angiography is mandatory for patients with isolated SCA. By presenting the patient who underwent successful combined CABG and AVR surgery in a presence of Lipton’s R-III type of isolated SCA, we emphasized the importance of meticulous, case-specific preoperative analysis, to ensure the optimal outcome.