A 52-year-old man with moderately impaired left ventricular systolic and diastolic function was scheduled for coronary artery bypass grafting on cardiopulmonary bypass (CPB) via median sternotomy. The patient gave consent for publication of this report. After induction of anesthesia, a 3D transesophageal echocardiography (TEE) matrix-array probe (X7-2t transducer; Philips Healthcare, Andover, MA) was inserted, and during routine examination the coronary sinus (CS) anatomy was noted to be abnormal. While obtaining the midesophageal (ME) views of the mitral valve, the CS appeared to be in communication with the left atrium (LA) and an unroofed CS was confirmed with color flow Doppler (Fig. 1; Video 1, Supplemental Digital Content 1, http://links.lww.com/AA/B177). Full-volume 3D imaging of the LA supported the diagnosis of unroofed CS by demonstrating multiple communication channels between the CS and the LA (Fig. 2; Video 2, Supplemental Digital Content 2, http://links.lww.com/AA/B178). In the ME 4-chamber view with the multiplane angle at 0° and the probe retroflexed to view the CS in long axis, the CS ostium did not open into the right atrium (RA) and appeared walled off, consistent with CS ostial atresia (Fig. 3A; Video 3, Supplemental Digital Content 3, http://links.lww.com/AA/B179). The CS was dilated with a diameter of 17 mm. Color flow Doppler evaluation (Nyquist limit scale at 19 cm/s) revealed low-velocity flow within the CS that did not communicate with the RA (Fig. 3B). The surgeon’s initial plan to use retrograde cardioplegia was thus aborted. Instead, the heart was arrested with a larger initial dose of antegrade cardioplegia. After 2-vessel coronary artery bypass grafting, the patient was hyperkalemic (7.2 mEq/L) and required ultrafiltration, extending CPB time by an hour (total time 128 minutes). Post-CPB, poor left ventricular function required insertion of an intraaortic balloon pump and inotropic support (dobutamine, epinephrine). Postoperatively, the patient was slowly weaned off of inotropic support and was discharged home 2 weeks later.
CS ostial atresia is extremely rare; in a single-center study of 13,842 patients undergoing cardiac computed tomography over 5 years, Shum et al.1 found an incidence of 0.1% (15 patients). This rare anomaly occurs when, for unknown reasons, the CS orifice fails to communicate with the RA.2 Normally, the CS develops from the left horn of the sinus venosus in the left posterior atrioventricular groove and drains the cardiac veins into the RA via the CS orifice.1–3 CS ostial atresia necessitates alternative pathways for venous drainage of the heart, which manifest as associated congenital abnormalities, including unroofed CS, persistent left superior vena cava, CS atrial septal defect, or other anomalous venous connections (Table 1).1–3
CS ostial atresia is often clinically insignificant and diagnosed incidentally or on autopsy.1,3 When it occurs with unroofed CS, as in our case, direct communication between the CS and the LA results in right-to-left shunting.1,4 Significant left-to-right shunting can only occur with the addition of an atrial septal defect. Joffe et al.5 reported a case of a CS atrial septal defect resulting in a large left-to-right shunt from an unroofed CS via the normal CS ostium. While large left-to-right shunts require surgical correction, the right-to-left shunting in CS ostial atresia is hemodynamically insignificant because the walled off ostium prevents blood from entering the RA and does not warrant complex surgical repair. CS ostial atresia becomes clinically relevant during cardiac resynchronization therapy3 or cardiac surgery2,3 when the CS needs to be cannulated.
Unroofed CS is itself a rare congenital anomaly that may serve as an alternative means for venous drainage of the heart in CS ostial atresia. Of the 15 patients with CS ostial atresia identified by Shum et al.,1 2 (13.3%) had unroofed CS. In addition, 60% of cases were associated with dilated CS (diameter larger than 12 mm), ranging from 13 to 24 mm; 53.3% had other congenital cardiac anomalies.1 In the postmortem analysis by Adatia and Gittenberger-de Groot2 on 26 hearts with CS anomalies from a congenital heart collection, CS ostial atresia was present in 46% (n = 12), unroofed CS in 54% (n = 14), and the 2 occurred together in 4 hearts. While a persistent left superior vena cava is commonly associated with CS ostial atresia,1,3,4 this was not the case in 3 of the 4 hearts with both anomalies.2 In addition, no obstructing anatomical structures were seen in the expected location of the CS orifice.2 Prior Echo Rounds have described obstructing anatomical variants, such as thebesian valves or Chiari networks, making cannulation of the CS difficult6,7; CS ostial atresia differs because the CS orifice does not exist, making cannulation impossible.
Imaging a structure that does not exist is understandably difficult; thus, a variety of views and techniques must be used to convince oneself of its absence. Three-dimensional TEE is especially helpful for imaging complex anatomy and was useful in this case in both diagnosing CS ostial atresia and unroofed CS. Once an anomaly is suspected, an initial survey using live 3D full volume of the ME 4-chamber view at 0° can identify areas needing further inquiry. Real-time, full-volume imaging has the advantage of the largest possible acquisition sector and is not subject to artifact from arrhythmias or motion. Gain settings of at least 50% should be used in 3D TEE imaging to reduce the risk that structural drop out will be mistaken for a truly absent wall between the CS and the LA. CS ostial atresia can be excluded by identifying a patent CS orifice. Three-dimensional TEE has the advantage of rotation and cropping and can be used to visualize the CS orifice en face by rotating 90° clockwise from a 4-chamber view. Alternatively, it can support the diagnosis by not clearly imaging a CS orifice in its expected location medial to the eustachian valve, as well as by identifying an associated abnormality such as unroofed CS. An unroofed CS may be further investigated by obtaining a 3D zoom of the LA for improved spatial resolution; rotating the image to the atrial side (to obtain the surgeon’s view of the mitral valve) will reveal the lack of separation between the CS and the LA.
Perioperative diagnosis with computed tomography, magnetic resonance imaging, or TEE forewarns the impossibility of CS cannulation.1 Furthermore, it should prompt a search for other cardiac anomalies associated with CS ostial atresia that may have clinical or surgical implications. In our patient, who had left ventricular hypertrophy and coronary artery disease, retrograde cardioplegia could not be used, likely resulting in suboptimal cardiac protection. Thus, the inability to cannulate the CS likely contributed to the patient’s worsened biventricular dysfunction and the need for substantial mechanical and pharmacologic support postoperatively.
In conclusion, CS ostial atresia is a rare anomaly that precludes cannulation of the CS during cardiac surgery. CS ostial atresia is frequently associated with other cardiac anomalies that may have additional surgical implications. CS anatomy should be investigated in surgeries where TEE is used and retrograde cardioplegia is planned.
Clinician’s Key Teaching Points
By Martin M. Stechert, MD, and Roman M. Sniecinski, MD
- Coronary sinus atresia is a rare cardiac anomaly that can exist in isolation or in combination with other congenital malformations, including a persistent left superior vena cava and atrial septal defects (ASDs). When it is combined with an unroofed portion of coronary sinus in the left atrium, coronary venous return will be directed into the left atrium instead of its normal flow into the right atrium. This right-to-left shunt is usually well compensated and not clinically apparent unless an ASD is also present, which may result in significant left-to-right shunt.
- The long axis of the coronary sinus is reliably imaged using a modified midesophageal (ME) 4-chamber view, with the transesophageal echocardiography (TEE) probe retroflexed and further advanced toward the stomach. In the ME 2-chamber view, the coronary sinus is seen on screen left in short axis. A dilated coronary sinus, defined as a diameter >1 cm, should alert the echocardiographer for potential anomalies. Contrast is often injected into the left upper extremity veins, which will flow into the dilated coronary sinus instead of the superior vena cava, making the diagnosis of a persistent left superior vena cava.
- In this case of a 52-year-old patient undergoing a coronary artery bypass graft using cardiopulmonary bypass, coronary sinus atresia with an unroofed coronary sinus was incidentally noted on the routine TEE examination. Color flow Doppler failed to demonstrate the normal flow into the right atrium, suggesting coronary sinus atresia. Further examination illustrated the small right-to-left shunt going into the left atrium from the unroofed portion of the coronary sinus. Importantly, an ASD causing left-to-right shunt was excluded, and planned cannulation of the coronary sinus was appropriately aborted.
- A comprehensive TEE examination includes examination of the size and function of the coronary sinus. A dilated coronary sinus, or one that fails to demonstrate flow into the right atrium by color flow Doppler, should prompt further investigation into possible coronary sinus atresia, an unroofed coronary sinus, and other associated anomalies such as an ASD or persistent left superior vena cava. All these findings can have important surgical implications.
Name: Kimberly L. Kesner, MD.
Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.
Attestation: Kimberly L. Kesner approved the final manuscript.
Name: Mark A. Chaney, MD.
Contribution: This author helped design the study, analyze the data, and write the manuscript.
Attestation: Mark A. Chaney approved the final manuscript.
Name: Takeyoshi Ota, MD, PhD.
Contribution: This author helped analyze the data and write the manuscript.
Attestation: Takeyoshi Ota approved the final manuscript.
This manuscript was handled by: Martin J. London, MD.
1. Shum JS, Kim SM, Choe YH. Multidetector CT and MRI of ostial atresia of the coronary sinus, associated collateral venous pathways and cardiac anomalies. Clin Radiol. 2012;67:e47–52
2. Adatia I, Gittenberger-de Groot AC. Unroofed coronary sinus and coronary sinus orifice atresia. Implications for management of complex congenital heart disease. J Am Coll Cardiol. 1995;25:948–53
3. Lim PC, Baskaran L, Ho KL, Teo WS, Ching CK. Coronary sinus ostial atresia and persistent left-sided superior vena cava: clinical significance and strategies for cardiac resynchronization therapy. Int J Angiol. 2013;22:199–202
4. Ootaki Y, Yamaguchi M, Yoshimura N, Oka S, Yoshida M, Hasegawa T. Unroofed coronary sinus syndrome: diagnosis, classification, and surgical treatment. J Thorac Cardiovasc Surg. 2003;126:1655–6
5. Joffe DC, Rivo J, Oxorn DC. Coronary sinus atrial septal defect. Anesth Analg. 2008;107:1163–5
6. Kuroda M, Takahashi T, Mita N, Kagaya S, Miyoshi S, Saito S. Difficult cannulation of the coronary sinus due to a large Thebesian valve. Anesth Analg. 2013;116:563–6
7. Teo EY, Ittleman F, Hamlin MP. A Chiari network and difficult cannulation of the coronary sinus for retrograde perfusion. Anesth Analg. 2010;111:79–81