This is Dr Kiran welcoming the readers to the present post of NH pediatric cardiology blog. As discussed in the previous post, a new addition was to be made to the blog. After thinking for quite some time, I came up with this idea. A pediatric cardiologist is always in need for the current updates on the management of medical problems faced by the patient community. Seldom have we seen the busy practitioner sparing time to update himself on these issues. I have seen some of the very big names in the field erring badly in scientific sessions, not for the lack of knowledge but for the lack of updating it. I would be dealing with the current update in the management of some of the critical issues in our field. Let me get some feedback on this attempt, so that I can decide whether to continue this segment or not.

To begin with, let me touch upon Pulmonarty atresia with VSD with MAPCA dependent pulmonary circulation: The current concepts and dilemmas.

Some of the special characteristics of MAPCAs for revision:
• Derived from Splanchnic vascular plexus (DeRuiter et al in journal Circulation in 1993, titled ‘Development of the pharyngeal arch system related to the pulmonary and bronchial vessels in the avian embryo: with a concept on systemic-pulmonary collateral artery formation’)

• Intracardiac defects are fairly simple in MAPCA dependence rather than vertical PDA.

• MAPCAs are highly variable in their size, number, course, origin, arborization and histopathologic makeup. (Liao P et al in 1985 in JACC as ‘Pulmonary blood supply in patients with pulmonary atresia and ventricular septal defect’)

• The natural history of major aorta pulmonary collaterals includes progressive stenoses and occlusion, sometimes making any segment of lung supplied by these collaterals inaccessible or unusable if incorporated into definitive correction.

• Manipulation of these aorta pulmonary collaterals through attempts at unifocalization can produce iatrogenic occlusion in the form of scarring or anastomotic stenoses.

• Major aorta pulmonary collaterals without obstruction can lead to pulmonary vascular obstructive disease in the segments supplied by these collaterals.

• No intervention is needed for cyanosis in the neonatal period and in the overwhelming majority of patients, any attempt to manipulate the collaterals early in life is usually disastrous.

Some of the strategies for the management:

Unifocalization:

• Haworth and McCartney in 1980 published ‘Growth and development of pulmonary circulation in pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries’ in the British Heart Journal. They conceptualised the unifocalization or bringing together of the abnormal collateral segments to ultimately form a pulmonary arterial confluence through a staged approach. However, the results with the staged approach of unifocalization have been extremely variable, ranging from 12 to 60% in various studies.

• Reddy et al in 1995 published ‘Midline one-stage unifocalization and repair of pulmonary atresia with ventricular septal defect and major aortopulmonary collaterals’ in JTCS. They opined that only 20–30% of a cohort of newborn infants with this combination of anomalies will have complete repair with acceptable right ventricular hemodynamics if a delayed staged approach is taken. These authors reasoned that a single stage correction in early infancy before stenoses in collaterals could occur, and before irreversible pulmonary vascular destructive disease could occur, would logically be an ideal strategy for managing this otherwise frustrating condition. It was reasoned that the earlier in life that the greatest number of healthy lung segments could be incorporated into the unifocalized pulmonary circulation, the more likely one is to capitalize upon the tremendous potential for additional growth and development of the pulmonary circulation and parenchyma that exists in early infancy.

• The single stage unifocalization as proposed by Reddy et al was achieved in much younger age group by Lofland. In a study titled ‘The management of pulmonary atresia, ventricular septal defect, and multiple aorta pulmonary collateral arteries by definitive single stage repair in early infancy’ published in European Journal of Cardiothoracic Surgery in year 2000, eleven consecutive infants over an 18-month period ranging in age from newborn to five months went through the protocol with great success.

Growth of Native PAs

• In 1991, Iyer and Mee published their study titled ‘Staged repair of pulmonary atresia with ventricular septal defect and major systemic to pulmonary artery collaterals’ in ATS. The study strongly proposed promotion of growth of central pulmonary arteries with a shunt, either a central shunt or a direct aorta to native pulmonary arterial anastomosis.

• Duncan et al continued the hypothesis in 2003 JTCS article titled ‘Staged repair of tetralogy of Fallot with pulmonary atresia and major aortopulmonary collateral arteries’. They proposed intervention beginning at approximately six months of age with the creation of a central shunt or a direct aorta to pulmonary arterial anastomosis.

• Ishibashi et al in 2007 published ‘Clinical results of staged repair with complete unifocalization for pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries’ in European Journal of Cardiothoracic Surgery.

• Mumtaz et al in 2008 brought out their study in ATS titled ‘Melbourne shunt promotes growth of diminutive central pulmonary arteries in patients with pulmonary atresia, ventricular septal defect, and systemic-to-pulmonary collateral arteries’. Both the articles showed good results even in staged procedures.

• Griselli et al in 2004 had observed the relationship between the size of native PAs and the surgical outcome. In their article titled ‘The influence of pulmonary artery morphology on the results of operations for major aortopulmonary collateral arteries and complex congenital heart defects’ published in JTCS, they evaluated 164 patients over an 11-year period. A 69% complete repair was achieved. Most importantly, the best prognosis was with intrapericardial pulmonary arteries that were at least 75% of predicted size. The worst prognosis was in patients with no native pulmonary arteries, and the entire pulmonary blood supply supplied by collaterals only. There were no survivors at 10 years in this patient subgroup. Patients with diminutive but present native pulmonary arteries had an intermediate survival.

How can one go about:

Pulmonary atresia with VSD is a relatively less common entity. Hence, unless the centre is doing a high volume work, it may be difficult to get substantial numbers to bring up a management algorithm. The approach is more likely to be case based, as the possible variants are multiple. Yet, it may be possible to bring about the general guidelines in this issue. Let us see few tips on how to go about. This segment is open to additions from the readership. Please feel free to add on your views via comments box or by emailing me at drkiranvs@gmail.com. I shall moderate the additions as per need.

• The chief determinant of outcome is the provision of proper pulmonary circulation. Hence, good sized confluent pulmonary arteries carry the best prognosis. This is followed by potentially unifocalizable subset. To determine the pulmonary anatomy at any given age, Cardiac CT with 3D reconstruction can be very helpful. This modality shows how the collaterals course relative to other important mediastinal structures such as the trachea, esophagus and main stem bronchi.

• The next step would be a complete unifocalization as early in life as possible. The rationale for an early complete unifocalization is that there should be early normalization of cardiovascular physiology and correction of cyanosis. There should also be protection against pulmonary hypertension related to high flow through the collaterals or through a systemic shunt.

• If adequate pulmonary circulation is achieved by confluent PAs, the next step would be an elective VSD closure and RV to PA homograft conduit. The timing of such procedure differ between institutes and is largely left to the comfort of surgical team and availability of appropriate sized homograft.

• If the pulmonary arteries remain diminutive and the collaterals are small, it may be prudent to perform a central shunt to promote growth of the native pulmonary arteries at early stages. The child can then be serially evaluated to determine the status of PA growth.

• The most disappointing subgroup is the absence of native PAs with suboptimal collaterals. In this group, neither the unifocalization nor the central shunt is possible. Such children are left for the natural history, but they evoke interest in the genetic analysis.

Genetics of PA-VSD

In 1996, Digilio et al made an attempt to explain the genetics of TOF and its variants. In their study published in AJC titled ‘Comparison of occurrence of genetic syndromes in ventricular septal defect with pulmonic stenosis (classic tetralogy of Fallot) versus ventricular septal defect with pulmonic atresia’ they proposed a possible genetic syndrome as underlying defect.

In the same year, Momma et al in the same journal published ‘Cardiac anomalies associated with a chromosome 22q11 deletion in patients with conotruncal anomaly face syndrome’. In this article, they proposed that tetrology of Fallot with pulmonary atresia belongs to a spectrum of conotruncal cardiac malformations that are often associated with monosomy 22q11.

Matsuoka et al in 1994 in American Journal Of Medical Genetics had shown that the clinical presentation of monosomy 22q11 includes patients with conotruncal anomaly face syndrome, velo–cardio–facial syndrome and DiGeorge syndrome in the article titled ‘Confirmation that the conotruncal anomaly face syndrome is associated with a deletion within 22q11’.

Conclusion

The fascination of correct diagnosis often leads to frustration in complex pulmonary atresia, VSD and MAPCAs. Most of the effort should be invested in correct diagnosis and to ascertain the possibility of unifocalization. Whenever possible, the initial palliation should be to promote the growth of native PAs. Better understanding of genetic issues might modify the future strategies of approach to the problem.

Please forward your questions and suggestions to the comments box or to drkiranvs@gmail.com This should be an interactive section and those who can answer can post them in the same way.

With this, let us get back to our regular feature: interesting learning scenarios

THE DUCTAL PUZZLE

How many times one comes across a large PDA in TAPVC? Theoretically, it is rare. High Qp of CCHD and large PDA generally does not go together. We had a neonate with obstructed TAPVC. We did notice a large PDA on echo, but the confirmation took a side line because I could not visualize the vertical vein. The common confluence of pulmonary veins were visualised but the distal connections were not. I could not ascertain whether it was supracardiac or infracardiac variant. Since no abnormal vascular structure was found crossing the diaphragm, I presumed it to be non-infracardiac. In the mess of finding the vertical vein, the attention on the large PDA was lost. On the table, however, the surgeons did find the PDA. Since it was not mentioned to them, the surgery got tougher than expected. Thanks to the amazing analysis and skill of our surgical team, the neonate made an uneventful recovery. The lesson was on focus and on accepting what is seen than what is written in books! Now, the idea is clear. TAPVCs can have a large PDA as association!

ONE-AND-A-HALF IN TRICUSPID ATRESIA

Actually, I never thought of this possibility. Can tricuspid atresia, despite having a reasonable sized RV, go into one-and-a-half pump repair? Tricuspid atresias are always associated with single pump corrections. How can the mandatory ASD and VSDs be closed to achieve one-and-a-half repair in the absence of tricuspid valve? One of our senior surgeons was talking about this possibility and some of the case reports about this. The technique, as I can imagine, must be very different than the conventional one-and-a-half repair. Anyone has data on this? Please let us all know.

NATURAL REGURGITATION

What is the natural history of AV valve regurgitation in AV canal defects? “It is the PAH that finishes them before anyone can study the natural history of AVVR” was the retort by one of our senior surgeons. The point is well taken. However, the question is, in partial and transitional AV canal defects or in canal-TETs, is the AVVR different from that of innate AVVR in non-AV canal defects? When we talk of unbalanced AV canals which are destined for single ventricle pathways, does the AVVR increase with age or the heart gets adapted for AVVR and ends up working better over time? “AVVR begets AVVR” is an adage in general. Is it true for AV canal defects too? If anyone has the answer on the natural history of AVVR in AV canal defects of non-PAH type, please let me know.

Q WAVES OF ALCAPA

This one was another eye-opener. We came across a 2-month-old with recent history of viral infection and deterioration of general condition. Chest radiograph taken outside showed cardiomegaley. An echo done outside was reported as dilated cardiomyopathy. The parents were referred to us for second opinion. On echo at our place, I could see a tortuous RCA with normal calibre. Three small vessels erupted out of the left coronary sinus instead of one LMC. The flow across MPA was normal and I did not find any diastolic flow across the sinuses of pulmonary artery. On ECG, we found prominent Q wave in aVL and aVR. Small q waves were seen in V2. There were no reciprocal changes. Our senior consultant, Dr Sejal Shah was not happy with the disparity between the ECG and clinical picture. On repeating the echo, we found the atypical origin of LMC from main pulmonary arterial sinus. The small vessels which seemed to erupt from the LMC location of left coronary sinus were probably artefacts. The diagnosis of ALCAPA was established and the novelty of picture was educative. The question was “Can significant Q wave in a single lead in ECG be predictive of ALCAPA?” The answer I found that day was, YES.

X IN THE MIDDLE

We found one of our patients presenting with indeterminate loop of ventricles in a situs ambiguous situation. The great arteries were d-malposed, but even with best of the effort, we could not clarify the ventricular looping. The final report went as {A,X,L}! How many times do such situations happen? Please let us know your experiences with indeterminate ventricular loops.

PEDIATRIC CARDIOLOGY PEARLS

116. In Sudden Cardiac Death, the term SUDDEN has been used to describe various intervals, but usually refers to a time <1 hour from the onset of symptoms to death or irreversible neurologic injury. In distinction, sudden death is defined by the World Health Organization as “a natural death within 24 hours of the onset of symptoms” irrespective of the cause. However, if the interval between the onset of symptoms and biologic death is limited to <2 hours, a cardiovascular cause of death is identified in 88% of all cases. (Kuller L, Lilienfeld A, Fisher R. An epidemiological study of sudden and unexpected deaths in adults. In journal Medicine in the year 1967 page 341)

117. When administered as a rapid intravenous bolus, adenosine produces transient AV node block, terminating tachycardias using the AV node. (Camm AJ, Garratt CJ. Adenosine and supraventricular tachycardia. In New England Journal of Medicine in the year 1991 page 1621)

118. Historically, neural mediated syncope was classified according to the response to a tilt table test. The response to tilt table testing was classified according to isolated or combined changes of heart rate and blood pressure. Sutton's first definition referred to (i) a vasodepressor type, reflecting mainly a drop in blood pressure at the time of syncope without changes in heart rate; (ii) a cardioinhibitory type with a decrease in heart rate and/or asystole; and finally (iii) a mixed type reflecting both a decrease in heart rate and blood pressure. (Sutton R, Peterson M, Brignole M, et al. Proposed classification of tilt induced vasovagal syncope. In European Journal of Cardiac Pacing and Electrophysiology in the year 1992 page 180). A new classification has been proposed by the European Task Force on Syncope in 2001.

119. The standard ECG record consists of 12 leads recorded from nine body surface locations with the patient in the supine position. (Bailey JJ, Berson AS, Garson A Jr, et al. Recommendations for standardization of leads and of specifications for instruments in electrocardiography and vector cardiography: Report of the Committee on Electrocardiography and Cardiac Electrophysiology of the Council on Clinical Cardiology, American Heart Association. In journal Circulation in the year 1990 page 730)

120. By light microscopy, the cells of the sinus node are morphologically distinct from the surrounding atrial myocardium; they are smaller, more compact, and contained within a fibrous matrix. (Ho SY, Anderson RH. Embryology and anatomy of the normal and abnormal conduction system. In: Gillette PC, Garson A Jr, eds. Pediatric Arrhythmias: Electrophysiology and Pacing. Philadelphia: WB Saunders, published in year 1990 page 227)

That brings us to the end of another post. Please send your comments and criticism to drkiranvs@gmail.com Also, for the information of everyone interested in pediatric cardiology, NH is organising a CME on pediatric cardiology, mainly meant for paediatricians on Saturday, 29th January, 2011. It is interestingly titled “What, When and How: Anecdotal approach to pediatric cardiology”. There is no registration fee. Entry is only by a prior free registration. If anyone is interested in participating, please send an email to my mail id. I shall let you know the procedure.

Regards

Kiran