Management of pulmonary atresia or critical pulmonary stenosis and intact ventricular septum with a small or hypoplastic right ventricle

Determination of a new collagen type I alpha 2 gene point mutation which causes a Gly640 Cys substitution in osteogenesis imperfecta and prenatal diagnosis by DNA hybridisation

The molecular defect responsible for a sporadic case of extremely severe (type II/III) osteogenesis imperfecta was investigated. The mutation site was localised in the collagen type I pro alpha 2 mRNA molecules produced by the proband's skin fibroblasts by chemical cleavage of mismatch in heteroduplex nucleic acids. Reverse transcription-polymerase chain reaction DNA amplification, followed by cloning and sequencing, showed heterozygosity for a G to T transversion in the first nucleotide of exon 37 of the COL1A2 gene, which led to a cysteine for glycine substitution at position 640 of the triple helical domain. This newly characterised mutation is localised in a domain which contains several milder mutations, confirming that glycine substitutions within the alpha 2(I) chain do not follow a linear gradient pattern for genotype to phenotype correlations. In a subsequent pregnancy, absence of the G2327T mutation in the fetus was shown by allele specific oligonucleotide hybridisation to the trophoblast derived fibroblast mRNA after reverse transcription and in vitro amplification. (The nucleotide number assigned to the mutant base was inferred from the numbering system devised by the Osteogenesis Imperfecta Analysis Consortium (The OIAC Newsletter, 1 April 1994).)

Influence of right heart size on outcome in pulmonary atresia with intact ventricular septum

BACKGROUND

Neonates with pulmonary atresia and intact ventricular septum (PA-IVS) are frequently born with hypoplastic right heart structures that must grow after right ventricular decompression (RVD) procedures for a complete two-ventricle physiology to be achieved. Previous authors have asserted that neonatal right heart size or morphology will predict right heart growth potential. Since 1983, our bias has favored early RVD regardless of initial right heart size. In 1986, we recognized a subset of patients with coronary artery abnormalities associated with poor outcome after RVD and have defined these patients as having a right ventricular-dependent coronary circulation (RVDCC).

METHODS AND RESULTS

To assess the influence of right heart size on outcome independent of the presence of RVDCC, we measured echocardiographic right ventricular (RV) dimensions in 37 neonates with adequate studies presenting between 1983 and 1990. Coronary artery anatomy was adequately assessed by angiography in 36. RV volume and tricuspid valve (TV) diameter were significantly smaller in patients with RVDCC than in those without. However, there was no statistically significant association between RV volume or TV diameter and survival among patients with or without RVDCC: Among 29 patients without RVDCC, 23 of 24 (95.8%) who achieved RVD are alive compared with 1 of 5 (20%) who did not achieve RVD (P = .001). Twenty-one of the 23 survivors have a complete two-ventricle physiology with low right atrial pressure. Among 7 patients with RVDCC, 2 patients who underwent RVD died early of left ventricular failure, whereas 4 of 5 who did not undergo RVD have survived single ventricular palliation.

CONCLUSIONS

Small right heart size is associated with RVDCC but is not associated with survival in PA-IVS. Patients without RVDCC have improved survival after RVD regardless of neonatal right heart size.

Diagnosis and management of right ventricle-dependent coronary circulation in pulmonary atresia with intact ventricular septum

BACKGROUND

Coronary artery anomalies including 1) right ventricle (RV)-to-coronary artery fistulas, 2) coronary artery stenoses, and 3) coronary occlusions occur in patients with pulmonary atresia with intact ventricular septum (PA-IVS). In some, a large part of the coronary blood supply may depend on the RV. This RV-dependent coronary circulation may determine survival after right ventricular decompression (RVD): RVD may cause RV "steal" in the presence of fistulas alone and ischemia, coronary isolation, or myocardial infarction in the presence of coronary stenoses.

METHODS AND RESULTS

Eighty-two patients with PA-IVS who presented between January 1979 and January 1990 were reviewed; 26 (32%) had RV-to-coronary artery fistulas. Of these 26, 23 had adequate preoperative coronary angiograms for analysis. RVD was achieved in 16. Seven of 16 had fistulas only; each survived RVD. Six of 16 had stenosis of a single coronary artery [left anterior descending coronary artery (LAD), four; right coronary artery (RCA), two]; four of six survived RVD. Three of 16 had stenoses and/or occlusion of both the RCA and LAD; all three died shortly after RVD of acute left ventricular dysfunction.

CONCLUSIONS

1) Potential RV steal alone does not preclude successful RVD. 2) Fistulas with stenoses to a single coronary artery may not preclude successful RVD. 3) RVD appears to be contraindicated in the presence of stenoses and/or occlusion involving both the right and left coronary systems. Nonsurvival after RVD seems to depend on the amount of the left ventricular myocardium at risk, i.e., that which is distal to coronary artery stenoses, especially when involvement of both coronary arteries limits effective collateralization. Precise definition of coronary arterial anatomy is mandatory in neonates with PA-IVS.

Management of neonatal critical pulmonic stenosis in the balloon valvotomy era

We evaluated our recent experience with management of neonatal critical pulmonic stenosis and intact ventricular septum between 1982 and 1988. Thirty-nine patients (aged less than 3 months) were treated initially by operation (group A, n = 19) or with balloon pulmonary valvotomy (group B, n = 20). Patients in group A were younger (5 +/- 1.3 versus 18 +/- 4 days in group B) (mean +/- standard error of the mean) and had a greater degree of hypoxia (oxygen tension, 55 +/- 4 versus 80 +/- 6 mm Hg) (p less than 0.05 for all variables). Ten patients in group A and 8 patients in group B had right ventricular hypoplasia, based on an angiographically determined index. Balloon pulmonary valvotomy was attempted in 20 patients at the time of the initial catheterization but was unsuccessful in 9 owing to inability to catheterize the hypoplastic right ventricular outflow tract (n = 8) and to recurrent infundibular stenosis (n = 1). Patients with failed balloon valvotomy were subsequently operated on within 24 hours. The early operative mortality (less than 30 days) was 25% (7 of 28); one death (9%) occurred after successful balloon valvotomy owing to associated critical aortic stenosis. The early postoperative gradient was 20 +/- 2 mm Hg; the post-balloon valvotomy gradient was 18 +/- 3 mm Hg. We conclude that balloon pulmonary valvotomy yields good results in patients with critical pulmonary stenosis with essentially normal-sized right ventricle, whereas surgical pulmonary valvotomy is required for patients with right ventricular hypoplasia.