**12. Interventions**

With the availability of modified catheters and catheter delivery devices, the role of interven‐ tion in pediatric cardiology is increasingly becoming important

Catheter interventions can primarily do three things

**1.** Open things that are closed: Atrial septostomy – done in infants who need mixing of blood for maintaining saturation and cardiac output. Most common indication is transposition of great arteries with intact ventricular septum, other rarer indications are TAPVC with restriction at the interatrial septum, tricuspid atresia, pulmonary atresia, mitral atresia. Septostomy with a blade would be required if the infant is > 6-8 weeks as the septum becomes thicker.

**2.** Widen things that are narrow – involving the blood vessels and heart valves, done using balloon catheters and stents to prevent recoil in case of vessels. The stent gets incorporated into the vessel wall. There can be neointimal proliferation causing restenosis, usually in the first 2 years The procedure uses special plastic polymer balloons which will not inflate beyond predetermined size even under high pressure. This needs a guide wire to be placed across the narrow area with balloon placed across so as to place the waist (middle of the sausage) in the narrow region which is dilated with dilute contrast.

Used commonly for

**c.** Measurement of flow, pressure, reactivity and resistance of pulmonary vasculature to

The cardiac output can be calculated by the thermodilution technique or the Fick's principle.

'The uptake or release of substance by an organ is equivalent to the blood flow to the organ

O2 is used as the indicator and all the systemic organs or lungs are considered as one organ to

We use the 02 consumption in ml/min/m2 and this divided by the arteriovenous difference would give the systemic or pulmonary flows. The consumption is made available through

Systemic output would be the difference between the arterial oxygen content and mixed venous oxygen content (ideally measured in the middle of right atrium to average for the superior vena caval, inferior vena caval or coronary sinus venous blood whose oxygen content

Pulmonary output would be the difference between the pulmonary venous and pulmonary

Qp/Qs can be easily calculated even if we do not have the values of oxygen consumption. We need the systemic arterial, mixed venous and pulmonary arterial and pulmonary venous oxygen content (which is assumed to be 100% in the absence of pulmonary pathology).

Pressure measurements are based on fluid filled catheters, or large bore catheters with multiple side holes which would yield accurate description of intracardiac waveforms. The resistance is calculated using the Ohm's law, which is the difference in the pressure across the organ divided by the amount of blood flowing through it. PVR (Pulmonary vascular resistance) would be transpulmonary gradient (difference between the mean PA and LA pressures)

With the availability of modified catheters and catheter delivery devices, the role of interven‐

**1.** Open things that are closed: Atrial septostomy – done in infants who need mixing of blood for maintaining saturation and cardiac output. Most common indication is transposition of great arteries with intact ventricular septum, other rarer indications are TAPVC with

or Wood units [18]

various drugs in patients with elevated pulmonary artery pressure.

Fick's principle is based on the fact that

240 Principles and Practice of Cardiothoracic Surgery

estimates based on age, sex and heart rate.

may be different)

artery oxygen content.

**12. Interventions**

multiplied by the arteriovenous difference of the substance'

divided by the pulmonary flow. Measured in mmHg/ L/min/m2

tion in pediatric cardiology is increasingly becoming important

Catheter interventions can primarily do three things

estimate the systemic or pulmonary output respectively.

**d.** Estimation of cardiac output, Qp/Qs calculation for assessment of operability.


ASD, VSD and PDA's – ASD's upto 32 mm diameter can be closed, the defect needs a rim of 4 mm for the device to be centred and placed. Amplatzer devices are FDA approved and have the longest track record.

Closure of VSD requires careful assessment to ensure that the device would not interfere with tricuspid or aortic valvar mechanisms. Arrhythmias, stroke, perforation, device embolization, incomplete closures are the risks involved.

Large PDA's > 5mm are closed with Amplatzer I device which has a single aortic rim and is mushroom shaped.

Coils – are metal wires coated with thrombogenic Dacron strands, suitable for vessels < 6-7 mm, with an area of narrowing. The thrombus formation around the coil plugs the vessel. Embolization, incomplete closure and hemolysis are possible risks.

in the presence of increased work of breathing. They have increased closing capacity with airway closure occurring during normal tidal ventilation putting them at risk of developing hypoxemia and atelectasis. In addition dilated pulmonary arteries and left atrium can

The Basis of Management of Congenital Heart Disease

http://dx.doi.org/10.5772/53654

243

**Pulmonary hypertension** both pre and postoperatively plays an important role in the planning

Preoperatively it can be due to large left to right shunt lesions, or due to pulmonary venous

Intraoperatively- light anesthesia, hypoxemia, hypoventilation, lung hyperinflation or hypoinflation, hypothermia, respiratory and metabolic acidosis, protamine, blood products, prolonged bypass with inflammatory response and capillary leak, compression and atelectasis of lung, pulmonary edema from inadequate venting of left atrium can all contribute to

Intravenous drugs can be used to reduce the PVR, but they lack selectivity and can cause systemic hypotension. Nitroprusside, glyceroltrinitrate, milrinone, Prostaglandin E1 and I2, tolazoline and isoproterenol have been used. Inhaled NO is most selective pulmonary vasodilator currently available; it is rapidly taken up and inactivated by haemoglobin as it diffuses from the alveoli. Oral drugs in the form of PDE type V inhibitor, sildenafil and

Preoperative evaluation should keep in mind the physiology of defect, and the changes that the preoperative treatment could have caused (diuretics causing hypokalaemia) and the presence and severity of cyanosis and pulmonary hypertension. Haematocrit greater than 65% can exacerbate tissue hypoxia and can cause stasis and potential thrombosis. Avoiding dehydration is very important to avoid tissue hypoxia and to maintain renal function postop‐

Non-invasive monitoring using electrocardiography, pulse oximetry, capnography, noninvasive blood pressure is placed before induction, invasive arterial and central venous line should be planned according to procedure. Neurologic monitoring and cerebral protection is of concern during congenital heart surgery. Nasopharyngeal temperature, continuous EEG, transcranial Doppler, frontal lobe infrared spectroscopy and cerebral oximetry can be used to evaluate cerebral blood flow velocity and perfusion. Intraoperative echocardiography has achieved a significant role in repair of CHD. It helps in re-evaluation of anatomy before intervention, adequacy of surgical repair and de-airing after weaning from cardiopulmonary

bypass and has become a integral part of monitoring in many units including ours.

choice of induction techniques, inhalational, IV or IM.

Maintenance of diastolic pressure and coronary perfusion is important particularly in the setting of duct dependent lesions and in situations of altered coronary perfusion. There is a

Fentanyl (15-25 ug/kg), ketamine (1-3 mg/kg), Pancuronium (0.2mg/kg) or Suxamethonium (2mg/kg) in combination with glycopyrrolate (10ug/kg) allows prompt induction and airway control without significant increase in PVR. Midazolam (0.1-0.2mg/kg) is also a useful adjunct

endothelin I blocking drugs bosentan have shown encouraging results. [21,22]

compress bronchi causing lobar collapse. [20]

of surgery, anesthesia and postoperative care.

increased pulmonary vascular resistance (PVR).

eratively.

obstruction, rarely due to pulmonary vascular obstructive disease.

Other defects which have been plugged are ruptured sinus of Valsalva especially the ones arising from the non-coronary sinus, aorta LV tunnels, veno-venous collaterals plugging following cavopulmonary connection. [19]
