Friday, November 12, 2010

Dr Kiran welcomes all to the new post of NH blog.

I should thank the responses I got for a small (?emotional) outburst in the last post. My teachers whom I revere a lot, my friends who have a cordial relationship, my colleagues who I thought would never have read the blog – all came together to assure that the blog is being read and for various reasons it should be continued. That was indeed a great reinforcement.

There was a suggestion also: that I should invite few big people to write for the blog. To the best of my knowledge, I do it in every post! Of course, neither the name nor the pattern of blog suggests that I own the blog. Let me reiterate once again: The blog belongs to everyone who holds any passion towards its objective put up below the masthead. All are formally invited to be a part of the content of this blog once again.

The section of “Current controversies in Pediatric Cardiology” seems to have evoked better response. I shall try to continue this section till I get drained off the ideas!

This time in this segment, I am dealing with the use of cath data in decision making. This is possibly one area which has minimal consensus and maximal idiosyncratic interpretation. We shall see the available evidence for this.

Q1: Which anesthetic agents should be used for cath studies in children?

Various drug protocols are drawn for this purpose, but the supporting literature is not uniform. Laird et al in 2002 presented their data in the journal Anesthesia and Analgesia under the title ‘Pulmonary-to-systemic blood flow ratio effects of Sevoflurane, Isoflurane, Halothane, and Fentanyl/Midazolam with 100% oxygen in children with congenital heart disease’, in which they discouraged the use of inhaled drugs for their myocardial depressant effects. Of the intravenous choices, long back in 1990, Berman et al in their article titled ‘Hemodynamic effects of Ketamine in children undergoing cardiac catheterization’ published in journal Pediatric Cardilogy had observed that Ketamine given in boluses would increase pulmonary vascular resistance, raking up a controversy. In a study published by Williams et al in 1999 in the journal Anesthesia and Analgesia titled ‘The hemodynamic effects of Propofol in children with congenital heart disease’, it was noted that Propofol given as a single drug seems to decrease systemic vascular resistance, making calculations of shunts unreliable. The same opinion was shared by Oklu and colleagues in 2003 in their article ‘Which anesthetic agent alters the hemodynamic status during pediatric catheterization? Comparison of Propofol versus Ketamine’ published in the Journal of Cardiothoracic and Vascular Anesthesia. In this prospective randomized study, continuously administered ketamine did not affect pulmonary vascular resistance significantly. Few workers in this field decided to go for low dose combination modules. Jobier et al used Midazolam with Ketamine. Their data was published in journal Pediatric Cardiology in 2003 under the title ‘Use of low-dose Ketamine and/or Midazolam for pediatric cardiac catheterization: is an anesthesiologist needed?’ In the same year, Kogan et al published ‘Propofol-Ketamine mixture for anesthesia in pediatric patients undergoing cardiac catheterization’ in the Journal of Cardiothoracic and Vascular Anesthesia. These two studies have formed the basis for the evidence in this regard, under class IIa indication.
In pediatric patients undergoing cardiac catheterization for hemodynamic measurements, sedation and analgesia can be achieved by combining midazolan with fentanyl, or by using low-dose ketamine in association with either midazolan or low-dose propofol. Continuous intravenous administration is preferable. Multi-drug cocktails, inhaled agents, propofol as single drug and bolus administration of any drugs should be avoided. (Level of evidence: B)

Q2. How to assess and interpret Qp, Qs, SVRI and PVRI?

Presumed entities while using Ficks principle have jeopardized the calculations since its onset! Yet, it is continued for the lack of better alternatives. The landmark article by Wilkinson in the journal Heart in 2001 titled ‘Congenital heart disease: haemodynamic calculations in the catheter laboratory’ serves as the basic manual for formulae and technical advice. As per the advice from Wilkinson, if an assumption is considered, then more than one value should be obtained. The classical paper of LaFarge and Miettinen on ‘The estimation of oxygen consumption’ published in journal Cardiovascular Research in the year 1970 serves as the core guide and has universal usage. However, it should be acknowledged that in infants and toddlers, it provides higher oxygen consumption values making the calculations appear ridiculous sometimes. To overcome this issue, two studies have come up. In 1989, Lindahl wrote ‘Oxygen consumption and carbon dioxide elimination in infants and children during anaesthesia and surgery’ in British Journal of Anaesthesia. This was followed by ‘Oxygen consumption in infants and children during heart catheterization’ by Lundell and co-workers in the journal Pediatric Cardiology in 1996. These values settled the issue for some extent but are still far from accurate. The problem intensifies in cyanotic children especially for Fontan circulation. Shanahan et al in 2003 published ‘The influence of measured versus assumed uptake of oxygen in assessing pulmonary vascular resistance in patients with a bidirectional Glenn anastomosis’ in journal Cardiology in the Young. Here, they noted that the measured values of oxygen consumption were far greater than the assumed ones and suitability for Fontan completion may not be reliable with the data obtained. Bergstra et al had published ‘Assumed oxygen consumption based on calculation from dye dilution cardiac output: an improved formula’ in the European Heart Journal in 1995. The same was seconded in 2000 by Berger in European Heart Journal again in article ‘Possibilities and impossibilities in the evaluation of pulmonary vascular disease in congenital heart defects’. Dye dilution can be a suitable bridge before something better comes up. Hence the recommendation:
In patients with congenital heart disease associated with pulmonary hypertension, pulmonary and systemic blood flow and vascular resistance should be calculated preferably using measured oxygen consumption, with attention to all other potential sources of error. (Indication class: IIa, level of evidence: B)
If measured values of oxygen consumption cannot be obtained, calculations should be performed assuming alternative values at the upper and lower limits of the likely range for that given patient, and results expressed as intervals. If the likely range is too wide and a narrow one is required for decision-making, assumed values should not be used at all. (Indication class: IIb, level of evidence: B)

This sounds more logical than the words ‘cath has its own fallacies’ after making the patient and the performer go through the gruesome ordeal!

Q3: Pulmonary vasoreactivity and operability

Historically, the operability assessment was a radical step towards safety of surgery. One among the strong criticisms faced by the present technique is that at high oxygen concentrations, determination of arterial PO2 is necessary and measurement of oxygen consumption is not possible. In 1996, Berner et al published ‘Inhaled nitric oxide to test the vasodilator capacity of the pulmonary vascular bed in children with long-standing pulmonary hypertension and congenital heart disease’ in the American Journal of Cardiology. This was followed by article by Atz et al in 1999 in JACC, titled ‘Combined effects of nitric oxide and oxygen during acute pulmonary vasodilator testing’. These articles accounted pulmonary vascular resistance and pulmonary to systemic resistance ratio, and the way they change during an acute vasodilator challenge have been taken into consideration. The article by Atz also defined maximal achievable stimulation without any toxic side-effects by 10 minute administration of a mixture containing >90% oxygen and 80 ppm nitric oxide. With these values as baseline, many workers tried to improvise the effect. Cannon et al published their study in 2005 in journal Pediatric Cardiology under the title ‘Nitric oxide in the evaluation of congenital heart disease with pulmonary hypertension: factors related to nitric oxide response’ in which they used 20ppm NO without enhancing the oxygen concentration. Alternative strategy of starting at low concentrations with gradual increases until response is also advocated, but would involve longer hours and multiple samplings, both of which are not advocated in children.
Hence, the recommendations would be:
In patients with congenital heart disease and pulmonary hypertension, there are no simple ways to predict outcomes following correction of the cardiac defects. Therefore, operability (which does not imply a warranty of favourable outcome without any residual elevation of pulmonary pressures) should be defined on an individual basis, taking into account a substantial amount of clinical data as well as information derived from noninvasive and sometimes invasive evaluation. (Class I indication, Level of evidence:C)
Also, in patients with biventricular circulations and baseline elevation of pulmonary vascular resistance > 6 Wood units∙m2 and a pulmonary to systemic resistance ratio of >0.3, a >20% decrease in both parameters during inhalation of low concentrations of nitric oxide, with respective final values of <6 Wood units∙m2 and < 0.3 indicates that vasoconstriction plays a role, and suggests that from the hemodynamic point of view, correction of the defect may be considered as a reasonable approach. (Class I indication, Level of evidence:B)

This marks the end of this topic. I have taken up 3 relevant questions and drawn 5 recommendations as per the available evidence. Please let me know if you would like to have a complete bibliographic notation of the studies mentioned in the discussion. If so, I shall provide them at the end of discussion to avoid the incoherence of flow. Please send your comments and suggestions to drkiranvs@gmail.com to enable others to understand your ideas and flow of thoughts.

With this, let us continue towards our regular feature: Interesting learning scenarios.

HYPOPLASTIC LV, HYPER-CORONARIES!

This 9-day-old baby presented to us in a perfectly asymptomatic condition. On echo, we found an aneurysmal IAS with a moderate L to R shunt, small MV (Z-score minus 5), small, non-apex reaching LV with intact IVS, small aortic valve (Z-score minus 3) with near absence of antegrade flow. The hypoplastic LV was decompressing by a moderate MR. Great artery relationship was normal. What surprised us were a normal sized ascending and transverse aortae and the neck vessels. Further distally, there was a small, bidirectionally shunting PDA with not much retrograde filling. How is the brain fed? What can explain the size of proximal aorta? The surprise element of the picture was unusually dilated coronaries filling retrograde. The RCA was massive and coursed along the right AV groove. The LMC was enlarged with normal branching, but could not be traced much. The distal end of any of the coronaries could not be traced on echo. It was clear on colour Doppler that the flow in the coronaries was towards the aorta. Surprisingly, there was no wall motion abnormality or functional impairment of the right ventricle. It is the first time that I had seen such a combination. Is this described? What are the management options in this kid? Would it still require the first stage of Norwood despite having a good sized proximal aorta? Can we create a VSD to decompress the LV so as to minimise the MR? Please let me know your experiences with such scenarios. I shall keep the readership updated if I get any further info on this.

ISOLATED TR

We do come across good number of isolated sever TR in many children. They are usually not much symptomatic. The tolerability of the heart problem is good in them. The symptoms are more often non-cardiac than the other way. How should such children be treated? The ECS guidelines of 2007 specify wait-and-watch policy. Should we actually wait for RV to fail? Isn’t the prognosis worse after RV failure? Can we go by any additional data like MRI for RV volumes? Is this data good for taking a radical decision? Our senior surgeons always maintain that the patient should ‘earn’ his surgery. How would such subgroup earn the surgery? The overall data that I could gather justify the stand taken by ECS. Is the policy any different in other places? Please let me know your takes on this issue.

SEQUENTIAL OBSTRUCTION

Please take a look on this scenario. A toddler with Tricuspid atresia 1B. The VSD is reported as restrictive. Pulmonary valve is good sized and PA sizes are OK. The ASD is restrictive, as evidenced by data on echo and cath. There are no systemic symptoms like edema or pulsatile liver. If the reverse pulmonary venous wedge pressure turns out to be 16mmHg, can we confidently do a BD Glenn and an atrial septectomy? In other words, when there is a sequential obstruction (as restrictive ASD and restrictive looking VSD in this case), can we relieve the proximal (by atrial septectomy) and be confident of the status of distal (VSD)? What would happen to PA pressures with atrial septectomy? How controlled can a concomitant PA band be? When Fontan completion does appear to be on cards, can one take the risk of closing the antegrade flow via PA? These were some of the questions that came up during one of our discussions. If anyone has sorted out this scenario earlier, please let us know the possible alternatives in such cases.

ROLE OF NUMBERS

What is the yield of cath data in ASD with RV dysfunction? We came across a 13-year-old with this picture. He had a large ASD with severe PAH and RV dysfunction. He went through the cath procedure. The PA pressures were half-systemic. The RV EDP was 12mmHg. The RV injection is not done in such cases, so cath assessment of RV function was not possible. The software for calculating the RV volumes is not available with us. There were no additional lesions. There is a clear text-book indication for cath in this scenario. But, what is the yield? What cath data would have influenced a different strategy? If not a complete closure, we would have done a reduction of ASD size, leaving a fossa ovalis defect and contemplating a device closure in future as per need. Is the risk/benefit ratio justified in such scenarios? Should we be drawing a different strategy for such cases? Is my analogy wrong or am I missing something in the entire picture? Please let me know.

BATSON’S PLEXUS

Often, we find the surgical team talking of Batson’s plexus during description of AP collaterals. I found this data on vertebral venous plexus otherwise called Batson’s plexus: Any of four interconnected venous networks surrounding the vertebral column; anterior external vertebral venous plexus, the small system around the vertebral bodies; posterior external vertebral venous plexus, the extensive system around the vertebral processes; anterior internal vertebral venous plexus, the system running the length of the vertebral canal anterior to the dura; posterior internal vertebral venous plexus, the system running the length of the vertebral canal posterior to the dura; the latter two constitute the epidural venous plexus.
Throughout this description, I could not find a single link that can connect Batson’s plexus to AP collaterals of cardiovascular utility. Please let me know if any study has been conducted to show that they are indeed Batson’s plexus.

PEDIATRIC CARDIOLOGY PEARLS

101. When the degree of valvular pulmonary stenosis is severe enough to cause a decrease in fetal right ventricular output, a larger-than-normal atrial right-to-left shunt is established in utero. This condition has been termed critical pulmonary stenosis. (Freed MD, Rosenthal AR, Bernhard WF, et al. Critical pulmonary stenosis with diminutive right ventricle in neonates. In journal Circulation in the year 1973 page 875)

102. Unlike the patient with a duct-dependent pulmonary circulation and pulmonary atresia with ventricular septal defect, the caliber of the pulmonary arteries in patients with pulmonary atresia and intact ventricular septum rarely is a major determinant of outcome. It is important to recognize that significant coarctation of the left pulmonary artery associated with the site of ductal insertion can occur in the neonate and the young infant. This may be, in part, mediated by the observation that the arterial duct tends to close earlier in patients with pulmonary atresia and intact septum than it does in patients with pulmonary atresia and ventricular septal defect. (Marino B, Guccione P, Carotti A, et al. Ductus arteriosus in pulmonary atresia with and without ventricular septal defect. Anatomic and functional differences. In Scandinavian Journal of Thoracic and Cardiovascular Surgery in year 1992 page 93)

103. In Pulmonary Atresia with VSD, the blood supply to the lungs is entirely from the systemic arterial circulation. The sources are the ductus arteriosus, systemic-to-pulmonary collateral arteries, occasionally a coronary artery, and plexuses of bronchial or pleural arteries. Ductal and collateral sources may coexist in the same patient but only rarely coexist in the same lung. (Liao PK, Edwards WD, Julsrud PR, et al. Pulmonary blood supply in patients with pulmonary atresia and ventricular septal defect. In Journal of American College of Cardiology in the year 1985 page 1343)

104. Maternal treatment with trimethadione or paramethadione during the pregnancy has been associated with the development of multiple anomalies, including cardiac septal defects and TOF. (Feldman GL, Weaver DD, Lovrien EW. The fetal trimethadione syndrome. In American Journal of Diseases in Children in the year 1977 page 1389)

105. Truncal valve stenosis, when present, usually is associated with nodular and dysplastic cusps. (Butto F, Lucas R, Edwards J. Persistent truncus arteriosus: Pathologic anatomy in 54 cases. In the journal Pediatric Cardiology in the year 1986 page 95)

With this, I conclude this post. Thanks again for the support. If you come across any controversial topic that needs discussion and evidence search, please let me know. I shall try to discuss the topic, crediting you for the copyright of discussion! Please feel free to put your opinions in the comments box or use my email id drkiranvs@gmail.com to send your suggestions and comments

Regards

Kiran

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