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Ann Thorac Surg 1996;62:949-950
© 1996 The Society of Thoracic Surgeons

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Correspondence

Pulmonary Atresia, IVS, and RV-CAC: Can CABG Alter Choice of Repair?

Department of Cardiothoracic Surgery, Govt. General Hospital, Madras 600 003, India

To the Editor:

I read with interest the two articles on pulmonary atresia and intact ventricular septum by Laks and associates [1] and Waldman and colleagues [2] concerning management of important right ventricle (RV)-to-coronary artery connections.

In this complex congenital anomaly, choice of operation is determined by RV volume, size of the tricuspid annulus (TA), and presence of coronary artery abnormalities. After initial palliation in neonates by a systemic-to-pulmonary shunt, the choice of the next procedure is controversial. Presently, if it is thought that a significant amount of left ventricular myocardium will be placed at risk by decompressing the RV, all treatment protocols lead to a Fontan-type univentricular repair.

It has not yet been possible to identify a group of patients in the neonatal period who have an RV and a TA that are too small to ever provide all the necessary pulmonary blood flow. In the Boston Children's Hospital experience [3], even when RV volumes were less than 8 mL/m² and TA size was less than 9 mm, a two-ventricle repair was ultimately possible. Data from de Leval and coworkers [4] show survival after a two-ventricle repair when tricuspid valve diameters were larger than 3 standard deviations below normal (Z value greater than -3). However, the Congenital Heart Surgeons Society multicenter study has shown that so far no patient with TA diameter more than 4 standard deviations below normal has progressed to a two-ventricle correction [3].

In very small RVs with hypoplastic tricuspid valves, TA diameter does not increase as the patient grows unless the RV is decompressed.

Decompression of the small RV unfortunately is contraindicated by the presence of an RV-dependent coronary circulation. If there is no native coronary artery narrowing, blood flows into the RV in diastole ("coronary steal"), causing ischemia. If the proximal coronary artery is stenotic, on the other hand, antegrade perfusion from the RV will be reduced by lowering RV pressures. In the Boston Children's Hospital analysis [3], RV decompression is tolerated as long as not more than one major coronary artery is stenosed. However, the procedure is associated with increased left ventricular dysfunction, and myocardial preservation is important for survival in these patients, especially in Fontan candidates.

Two approaches were discussed for this situation: (1) closure of the tricuspid valve to reduce coronary steal and prevent antegrade perfusion of deoxygenated blood into the coronary system, and (2) establishment of an aorta-to-RV conduit to perfuse the coronary arteries with oxygenated blood, thus relieving ischemia. Both procedures seem somewhat nihilistic in that they condemn the RV to nondevelopment, resulting in a Fontan-type repair only. In addition, the disadvantages of leaving behind a small but hypertrophied RV include arrhythmogenicity and interference with normal left ventricular contractility [5].

In another rare congenital defect, anomalous origin of the left coronary artery from the pulmonary artery, a somewhat similar situation occurs. Initially the left ventricle is perfused with deoxygenated blood from the pulmonary artery. Once intercoronary collaterals are formed, diversion of blood into the low-resistance pulmonary circuit may result in left ventricular ischemia. The resultant left ventricular myocardial dysfunction has been reversed by grafting the internal thoracic artery to the anomalous left coronary artery in infancy [6].

Conceptually, I think it might be possible to anastomose internal thoracic arteries to the abnormal coronary arteries in pulmonary atresia with intact ventricular septum also. Grafts can be connected distal to the site of obstruction if any. The RV-to-coronary artery connections can then be dealt with just as any other coronary artery-to-RV fistula. The options include surgical (ligation, tangential arteriorrhaphy, or closure from within the RV) or transcatheter closure.

At one stroke this approach would then obviate all limitations imposed by the abnormal coronary circulation and allow further decision regarding surgical management to be made based on the status of the RV and TA, and their predicted growth potentials.

If the RV enlarges sufficiently, a two-ventricle repair can be performed. If not, a one-and-a-half ventricle repair (bidirectional cavopulmonary shunt with RV to pulmonary artery connection) may be feasible and give better long-term outcomes than a Fontan operation. If all else fails, the performance of a Fontan-type procedure would not be precluded, and in fact may be more successfully performed because the left ventricle is no longer ischemic.

References

1. Laks H, Gates RN, Grant PW, Drant S, Allada V, Harake B. Aortic to right ventricular shunt for pulmonary atresia and intact ventricular septum. Ann Thorac Surg1995;59:342–7.[Abstract/Free Full Text]
2. Waldman JD, Karp RB, Lamberti JJ, Ruschhaupt DG, Agarwala A. Tricuspid valve closure in pulmonary atresia and important RV-to-coronary artery connections. Ann Thorac Surg1995;59:933–41.
3. Pulmonary atresia with intact ventricular septum. In: Castañeda AR, Jonas RA, Mayer JE, Hanley FL, eds. Cardiac surgery of the infant and neonate. Philadelphia: Saunders, 1994:240–1, 245.
4. De Leval M, Bull C, Hopkins R, et al. Decision making in the definitive repair of the heart with a small right ventricle. Circulation1985;72(Suppl 2):52–60.
5. Maruyama Y, Nunokawa T, Koiwa Y, et al. Mechanical interaction between ventricles. Basic Res Cardiol1983;78:544–59.[Medline]
6. Vigneswaran WT, Campbell DN, Pappas G, Wiggins JW, Wolfe RW, Clarke DR. Evolution of management of anomalous left coronary artery: a review of surgical approaches. Ann Thorac Surg1989;48:560–4.[Abstract]

Reply

Division of Pediatric Cardiology, University of New Mexico 2211 Lomas Blvd Ne, Albuquerque Nm 87131-5311

To the Editor:

Patients with pulmonary atresia, intact ventricular septum, and important RV-coronary artery connections are known to be at risk for left ventricular ischemia. The possibility of bypass grafting to the coronary arteries has been suggested as a means of ensuring left ventricular perfusion (with oxygenated blood) and allowing surgical modalities that might lead to a two-ventricle repair rather than a Fontan approach. Three points from the letter warrant reply.

1. The concept of bypass grafting and RV decompression to promote growth assumesthe presence of severe stenosis between the native coronary artery system and the connections with the RV. Without such obstruction, coronary artery blood-whether derived from the aorta or the internal thoracic artery-would flow into a decompressed RV rather than the myocardium, causing the very ischemia one wishes to avoid. Furthermore, although much attention has been paid to coronary stenoses, (A) they are infrequent-we had no such patients in the 15 reported with important RV-coronary artery connections [1], and (B) there is no good way at present to grade the severity of obstruction.
   
2. One must view the RV-coronary artery connections pathologically to grasp the difficulty of dealing with them "like any other coronary artery-to-RV fistula." These vessels are thin-walled and often intramyocardial, and they may have multiple orifices into a heavily trabeculated and hypertrophied RV with a hypoplastic tricuspid orifice and endocardial fibroelastosis. The native coronary arteries of neonates average 1.2 to 1.3 mm in diameter [2]. Even with the microsurgery that cardiovascular surgeons routinely perform in neonates, direct approach to such vessels seems a daunting task.
   
3. There is a recent trend to say that "anything is better than a Fontan operation." There are numerous reports about the problems found late after venous-to-pulmonary artery "reparative" procedures including pulmonary vascular obstruction, protein-losing enteropathy, ventricular dysfunction, dysrhythmias, and exercise intolerance. However, not all Fontan patients have problems, and some can be normal for decades. (I have a 12-year-old patient, 8 years after a Fontan procedure, who just swam in the Junior Olympics.) If we accept that the Fontan operation is palliative rather than corrective, andif we remember the problems of chronically shunted patients, especially in their teens-eg, cyanosis, ventricular failure from volume overload, brain abscess, stroke, pulmonary vascular disease, discontinuous pulmonary arteries-then possibly we can put Dr Fontan's contribution into proper perspective. Only when we delete congenital heart disease at the chromosomal level can we truly say that we have "cured" the problem.
   

References

1. Waldman JD, Karp RB, Lamberti JJ, Ruschhaupt DG, Agarwala A. Tricuspid valve closure in pulmonary atresia and important RV-to-coronary artery connections. Ann Thorac Surg1995;59:933–41.[Abstract/Free Full Text]
2. Mavroudis C, Backer CL, Muster AJ, et al. Expanding indications for pediatric coronary artery bypass. J Thorac Cardiovasc Surg1996;111:181–9.[Abstract/Free Full Text]

This Article Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): S. Sivasubramanian Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Sivasubramanian, S. Articles by Waldman, J. D. Search for Related Content PubMed PubMed Citation Articles by Sivasubramanian, S. Articles by Waldman, J. D.