PA-IVS — #2 Coronary Artery Fistula and RV-Dependent Coronary Circulation (RVDCC)

1. Coronary arterial abnormalities in PA-IVS – why they matter

Pulmonary atresia with intact ventricular septum (PA-IVS) is rare, but its prognosis is driven as much by the coronary circulation as by the right ventricle (RV) itself. Coronary arterial abnormalities—ventriculocoronary fistulas, proximal stenoses, and ostial atresia—are identified in roughly two-thirds to three-quarters of patients with PA-IVS.[1–3]

Within this group, about one-third fulfil criteria for right-ventricle–dependent coronary circulation (RVDCC), in which myocardial perfusion relies on a hypertensive RV rather than the aorta.[1–3] This subset carries the highest risk of ischemia, sudden deterioration during RV decompression, and late death.[3–7]

2. Coronary artery fistula (CAF) in PA-IVS

2.1 Definition and basic concept

1. A coronary artery fistula (CAF) is an abnormal communication between a coronary artery and a cardiac chamber or great vessel.
2. In PA-IVS, most fistulas connect an epicardial coronary to the RV cavity, often via intramyocardial sinusoids.[1,2]
3. In “simple” CAF, the proximal coronaries are patent and coronary flow is antegrade from the aorta, with runoff from the distal coronary bed into the low-pressure RV.

Series using angiography and post-mortem examinations suggest that RV–coronary fistulas are present in 60–75% of patients with PA-IVS, but only a subset has critical proximal stenosis or atresia.[1,3]

2.2 Coronary steal and ischemia

Even when the coronaries are primarily aorta-dependent, a large CAF can significantly alter coronary hemodynamics:

• The fistulous connection lowers distal coronary perfusion pressure and provides a low-resistance runoff into the RV.
• This can produce a coronary steal phenomenon, in which blood is diverted away from the myocardial microcirculation despite angiographically normal proximal arteries.[1,3]
• Clinically, patients may present with ischemic ECG changes, regional wall-motion abnormalities, or ventricular dysfunction, particularly during stress or tachycardia.

In such simple CAF, closure or reduction of the fistula may relieve ischemia, provided the coronaries are not RV-dependent.

3. Right-ventricle–dependent coronary circulation (RVDCC)

In a more severe subset, the coronary circulation is partly or completely dependent on RV pressure for perfusion.

3.1 Pathologic substrate and definition

Classic angiographic criteria for RVDCC include:[2,3,6]

1. Stenosis or atresia of the proximal coronary arteries, frequently involving the left coronary ostium or main trunk.
2. Presence of ventriculocoronary fistulas or extensive myocardial sinusoids connecting the hypertensive RV cavity to the intramural coronary network.
3. Demonstration that epicardial coronaries fill retrogradely from the RV and drain into the aortic root, rather than receiving forward flow from the aorta.

In the cohort described by Giglia and colleagues, approximately 32% of PA-IVS patients met criteria for RVDCC, and these patients had a markedly higher risk of ischemic events and death following RV decompression.[3] Calder et al. likewise showed that coronary abnormalities—including ostial stenosis and atresia—were common and strongly linked to adverse outcomes.[1]

3.2 Hemodynamic consequences

Once RVDCC is established:

• Coronary driving pressure becomes tied to RV systolic pressure, not to aortic pressure.
• Blood enters the intramyocardial sinusoids from the RV, perfuses the epicardial coronaries retrogradely, and exits at the aortic root.
• Any fall in RV pressure (e.g., after valvotomy or conduit placement) reduces the gradient driving coronary perfusion, predisposing to:
• Global or regional myocardial ischemia
• Infarction and reduced ventricular function
• Malignant arrhythmias and sudden collapse

Patients with aortocoronary atresia (e.g., complete LCA atresia) represent the extreme of this spectrum and have a particularly poor prognosis.[4]

4. Hazard of RV decompression in RVDCC

4.1 Mechanism of injury

Interventions that “open” the RV outflow—such as percutaneous transcatheter pulmonary valvotomy (PTPV), surgical valvotomy, or RV-to-pulmonary artery conduits—aim to establish antegrade flow into the pulmonary arteries and reduce RV pressure.

In patients with RVDCC, this RV decompression removes the very pressure head that is maintaining coronary perfusion. The result can be abrupt myocardial ischemia precisely at the moment when the procedure would otherwise be considered technically successful.[2–4]

4.2 Clinical experience

Early reports showed that neonates with unrecognized RVDCC could suffer ST-segment changes, ventricular dysfunction, and even sudden death immediately after effective RV decompression.[2,3] Subsequent series confirmed that:

• The presence and severity of proximal coronary obstruction are major determinants of peri-procedural risk.[5,6]
• In the Spigel cohort of 103 neonates with PA-IVS, patients with RVDCC and proximal coronary obstruction had a 1-year transplant-free survival of 33%, compared with 70% in those with distal obstruction and significantly better survival in patients without RVDCC.[6]

These observations underpin the modern view that aggressive RV rehabilitation is contraindicated when the coronary circulation is critically RV-dependent.

5. Impact on treatment strategy and outcomes

The presence or absence of RVDCC is now a central branch point in management algorithms for PA-IVS.

5.1 Patients without RVDCC (RVDCC –)

In patients whose coronaries are predominantly aorta-dependent:

• RV–coronary fistulas may exist but are not the primary source of myocardial perfusion.
• PTPV or surgical valvotomy can usually be performed safely, with the goal of:
1. Establishing antegrade pulmonary blood flow
2. Promoting RV and tricuspid valve growth

Depending on RV size, tricuspid annulus, and functional response:

• Some patients achieve biventricular repair with good long-term outcomes.[4,7]
• Those with borderline RVs may be directed toward a one-and-a-half ventricle or single-ventricle pathway.

In contemporary series, survival for PA-IVS patients without RVDCC who follow a single-ventricle pathway is excellent, approaching 100% transplant-free survival in some cohorts.[5]

5.2 Patients with RVDCC (RVDCC +)

In contrast, patients with bona fide RVDCC have a very different trajectory:

1. Early phase (neonatal and infant period)
• Historical data showed high mortality during systemic-to-pulmonary shunt or RV decompression, often related to coronary ischemia.[2–4]
• Guleserian et al. demonstrated that once the early ischemic hazard is survived, single-ventricle palliation can provide excellent late survival, and thus should be the default strategy for most RVDCC patients.[4]
2. Influence of coronary anatomy on outcome
• Cheung and colleagues, studying PA-IVS patients managed along a single-ventricle pathway, found that those with RVDCC had substantially poorer transplant-free survival than patients without RVDCC (around 40% vs. 100% in their series).[5]
• Spigel et al. refined this further, showing that proximal coronary obstruction carries the worst prognosis, with 1-year transplant-free survival of 33%, compared with 70% in distal obstruction and much better outcomes in non-RVDCC patients.[6]
• Patients with aortocoronary atresia or multivessel proximal disease often warrant early consideration of primary cardiac transplantation rather than prolonged palliation attempts.[4–6]
3. Long-term phase
• Even after successful Fontan completion, RVDCC remains a persistent risk factor. Elias et al. reported that Fontan survivors with RVDCC are prone to late myocardial ischemia and sudden death, necessitating lifelong surveillance.[7]

5.3 Practical management principles

For patients with confirmed RVDCC:

• Avoid RV decompression strategies (PTPV, valvotomy, RV-PA conduit) unless coronary perfusion can be guaranteed by other means.
• Default to a single-ventricle palliation pathway (systemic-to-pulmonary shunt or ductal stent, followed by bidirectional Glenn and Fontan), recognizing that this offers the best long-term survival in most series.[4,5]
• Consider early listing for transplantation in patients with:
• Aortocoronary atresia
• Diffuse proximal stenoses with extensive ischemic injury
• Severely impaired ventricular function or refractory arrhythmias.[4–6]

6. Long-term surveillance and late complications

Even after a “successful” Fontan circulation, the coronary abnormalities do not disappear:

• Elias et al. showed that Fontan survivors with RVDCC remain vulnerable to exercise-induced ischemia, malignant arrhythmias, and sudden death.[7]
• Recommendations from this work and others include:[4,7]
• Periodic exercise testing and ischemia evaluation (stress echocardiography or nuclear perfusion imaging).
• Holter monitoring to detect occult arrhythmias.
• Repeat coronary imaging (catheter angiography or CT) in patients with uncertain anatomy or new symptoms.
• Consideration of implantable defibrillators or early transplant evaluation in patients with significant ischemia or arrhythmia burden.

Thus, RVDCC is not only a neonatal surgical problem but a lifelong coronary disease that continues to influence risk throughout adulthood.

7. Practical summary for the clinician and surgeon

1. Always define the coronary anatomy early in PA-IVS using high-quality angiography; look specifically for ventriculocoronary fistulas, proximal stenoses, and ostial atresia.[1–3,6]
2. Distinguish two broad coronary phenotypes:
• Simple CAF with coronary steal, where closure of the fistula may improve perfusion, and RV decompression is usually safe.
• RVDCC, where fistulas and sinusoids are the primary supply to the coronaries and must not be interrupted or decompressed without an alternative perfusion strategy.[2–4]
3. Use the presence and level of coronary obstruction (proximal vs. distal) as a key determinant of:
• Suitability for RV rehabilitation
• Need for single-ventricle palliation
• Threshold for early transplant referral.[4–6]
4. Provide lifelong follow-up for patients with RVDCC, even after Fontan, with particular attention to ischemia and arrhythmias.[4,7]

This framework explains why PA-IVS with RVDCC remains one of the most challenging lesions in congenital cardiology and surgery: the coronary circulation itself is fragile, pressure-dependent, and easily destabilized by interventions that are otherwise routine in right-sided outflow obstruction.

References

[1] Calder AL, Peebles CR, Occleshaw CJ. The prevalence of coronary arterial abnormalities in pulmonary atresia with intact ventricular septum and their influence on surgical results. Cardiol Young. 2007;17(4):387-396. (OUP Academic)

[2] Calder AL, Co EE, Sage MD. Coronary arterial abnormalities in pulmonary atresia with intact ventricular septum. Am J Cardiol. 1987;59(5):436-442. (Cambridge University Press & Assessment)

[3] Giglia TM, Mandell VS, Connor AR, Mayer JE, Lock JE. Diagnosis and management of right ventricle-dependent coronary circulation in pulmonary atresia with intact ventricular septum. Circulation. 1992;86(5):1516-1528. (OUP Academic)

[4] Guleserian KJ, Armsby LB, Thiagarajan RR, del Nido PJ, Mayer JE. Natural history of pulmonary atresia with intact ventricular septum and right-ventricle–dependent coronary circulation managed by the single-ventricle approach. Ann Thorac Surg. 2006;81(6):2250-2258. (ohsu.elsevierpure.com)

[5] Cheung EW, Richmond ME, Turner ME, Bacha EA, Torres AJ. Pulmonary atresia/intact ventricular septum: influence of coronary anatomy on single-ventricle outcome. Ann Thorac Surg. 2014;98(4):1371-1377. (OUP Academic)

[6] Spigel ZA, Qureshi AM, Morris SA, et al. Right ventricle-dependent coronary circulation: location of obstruction is associated with survival. Ann Thorac Surg. 2020;109(5):1480-1487. (PubMed)

[7] Elias P, Poh CL, du Plessis K, et al. Long-term outcomes of single-ventricle palliation for pulmonary atresia with intact ventricular septum: Fontan survivors remain at risk of late myocardial ischaemia and death. Eur J Cardiothorac Surg. 2018;53(6):1230-1236. (OUP Academic)