24 Interventional Catheterization
24.1 Basics
Today, an increasing number of cardiac catheterization procedures are no longer used for diagnostic purposes only. This means that more and more catheter-based treatment is now performed with interventional catheterization. In many centers today, more interventional catheterizations are performed than cardiac surgeries and catheter interventions constitute 60 to 80% of all cardiac catheterizations. The number of diagnostic catheterization procedures is steadily decreasing as echocardiography and magnetic resonance imaging of the heart gradually replace diagnostic cardiac catheterization. Many simple cardiac defects such as coarctation of the aorta, ASD, PDA, and some VSDs, can now be treated very well by interventional measures. The same is true for almost all valvular stenoses that were previously the domain of surgery. In addition, the development of materials and devices used is continually advancing, so that new areas are becoming accessible for the interventional cardiologist (e.g., percutaneous valve implantation, AV valve reconstruction, pulmonary artery banding, Fontan completion, treatment of subaortic or subpulmonary stenosis).
In the following sections some standard routines will be presented as examples of how patients can be treated using interventional procedures.
24.1.1 Preparation
Careful preparation is essential before a planned intervention, just as it is before surgery. This process usually includes the following preparations and examinations:
Organization of the existing documents, especially outpatient records, old medical reports, operation reports, cardiac catheterization reports, previous imaging (MRI, CT), and other details prior to the investigation
Discussion and clarification of the indication
General admission examination, especially
Neurological status
Ruling out infection
Ruling out clotting disease (petechiae, bruising, medical history)
Pulse or vascular status
Pulse oximetry
Blood pressure in all four limbs
Recent ECG—that is, obtained within the last 2 (to 3) months
Recent echocardiography
Insertion of a peripheral intravenous access port (routine blood sampling is usually not necessary)
Patient information
The patient should always be informed by an experienced colleague from the cardiac catheterization team who knows the nature of the intended catheter investigation and intervention and can explain it accordingly. Ideally, the procedure should be discussed with the patient and his or her parents before the cardiac catheterization. The general and specific risks associated with the planned cardiac catheterization and intervention should always be explained. The risks should also be documented in the patient information sheet. Examples of general risks are:
Sedation → Overreactions → Intubation → Intensive care monitoring
Puncture → Bleeding → Transfusion
Puncture → Thrombosis → Perfusion disturbance → Lysis treatment
Puncture → Thrombosis → Embolism
Puncture → Vascular lesion, vascular occlusion → Operation
Infection → Antibiotic treatment
Rhythm disorder → Pharmacological treatment, pacemaker treatment
Air embolism, systemic thromboembolism
Contrast medium intolerance → Shock→ Intensive care
Perforation → Pericardial effusion → Tamponade → Puncture/surgery
Radiation exposure
The specific complications of the individual cardiac defects and interventions and alternative treatment options are discussed in the respective chapters of this book.
In addition, the cardiac defect and the planned intervention should be illustrated in a diagram in the information sheet, and the questions of the parents and the patient should be discussed in detail. It should be emphasized that the overall risk for a simple diagnostic cardiac catheterization is 5% and the risk is somewhat higher for an interventional procedure. For complex interventions, the risk is sometimes comparable to that of surgery.
Sometimes a vascular puncture in the area of the neck and upper chest is necessary. For example, access to the jugular vein or to the subclavian vein is chosen following an upper cavopulmonary anastomosis or if there is known thrombosis of the leg/pelvic vessels. In these cases, the following additional complications have to be pointed out (risk < 5%):
Accidental puncture of the carotid artery
Puncture of the trachea/larynx
Pneumothorax
Hematothorax
Blood tests
For most interventional procedures, no “routine” blood tests are necessary before the planned operation. Should a patient have clinical signs of infection, for example, cardiac catheterization may be allowed or not based on the clinical examination. Likewise for electrolytes, Hb tests, kidney or liver enzymes: during cardiac catheterization, blood tests can be performed at any time, so electrolytes, Hb levels, and blood gases can be determined if necessary, using modern equipment in the catheterization laboratory. A clinical history of coagulation disorders is an important consideration that may trigger specific additional clotting tests.
When there is an increased risk for blood loss or myocardial perforation in certain examinations or interventions, additional laboratory tests can be ordered on a case-by-case basis (blood typing and cross-matching). An example of such an intervention is the catheter interventional opening of pulmonary atresia.
24.1.2 Sedation/Anesthesia/Monitoring
In most centers, cardiac catheterization is almost always performed in deep conscious sedation. General anesthesia is not usually necessary. This also applies to studies in which transesophageal echocardiography is needed (e.g., ASD closure). However, the safety measures and standards which apply for continuous monitoring by specialized medical and nursing staff are the same as those for surgery and anesthesia.
Premedication
A premed is given before the patient is moved to the cardiac catheterization laboratory (e.g., midazolam 0.1 mg/kg IV).
Monitoring
During catheterization, the patient is monitored continuously with ECG, pulse oximetry, and frequent checks of blood pressure. If necessary, oxygen is administered.
Deep conscious sedation
For deep conscious sedation with ketamine (and atropine) and propofol, the following regimen is recommended:
Monitoring with pulse oximetry, ECG, blood pressure
Oxygen mask / resuscitation bag at hand
Initiate sedation with ketamine 2 mg/kg IV
Atropine: at least 100 μg, max. 500 μg IV
Propofol bolus of 1 mg/kg IV
Propofol infusion of 5 mg/kg/h
If necessary, further doses of ketamine and propofol as indicated
Monitoring after cardiac catheterization
After completion of the procedure, patients are brought directly to the recovery area or ward for further monitoring. Monitoring in an intensive care setting or unit is not necessary in most cases. A physician accompanies the patient during transport to the aftercare station. The patient is given oxygen during transport and is continuously monitored with pulse oximetry and ECG.
Transfer to the ward
The patient is then handed over to the physicians and the nursing staff on the aftercare ward. The clinical condition is documented jointly (oxygen saturation, breathing, circulation).
24.1.3 Postinterventional Measures
Every interventional catheterization should be followed by a standardized and well-defined treatment schedule consisting of pharmacological treatment, checkups, and monitoring according to the procedure performed.
Such an algorithm may be as follows:
Heparinization
Not usually needed after a venous puncture. In cyanotic patients, 200 IU/kg/d until the next morning, continuous IV administration
After an arterial puncture, for 24 hours or until the next morning: 400 IU/kg/d, continuous IV administration
After interventions, for 36 to 48 hours or until the morning of the second day: 400 IU/kg/d, continuous IV administration
Infusion treatment: until the patients are awake and able to drink
Food/drink: As soon as the patients are awake, start with clear liquids; if well tolerated, give food and drink as desired.
Monitoring: Carry out continuous monitoring of pulses, blood pressure, and oxygen saturation through a central monitoring system with documentation; include assessment of the leg perfusion and neurological status.
Post-catheterization bleeding: If there is bleeding at the puncture site, renew (compression) dressing and extend monitoring for 12 hours.
24.2 Special Interventional Catheterization Procedures
24.2.1 Interventional Catheterization for Valvular, Vascular, and Outflow Tract Stenosis
Basics of Balloon Valvuloplasty
Definition
In balloon valvuloplasty, the narrow site of a vessel or a stenotic valve is stretched when the balloon catheter is inflated so that, ideally, only little or no residual stenosis remains.
Material
Balloon catheters of different lengths and diameters are available as well as balloons with different pressure capacities (low-pressure and high-pressure balloons). In addition, there are special balloons with special shapes (e.g., Inoue balloon for mitral valve valvuloplasty) or with special features (such as cutting balloons with small blades attached).
Procedure
First the pressure gradient is determined and the anatomy of the stenosis as well as the upstream and downstream vessels is visualized. A combination of angiography and previous echocardiography or MRI findings is useful for this. Then a guidewire is advanced through the stenosis into the downstream vascular area (e.g., in pulmonary valve stenosis into the pulmonary artery) or, if retrograde probing is performed, into the upstream area (e.g., for aortic stenosis into the left ventricle). Then the deflated balloon catheter is placed in the stenotic area, oriented by cardiac catheter angiography.
When the balloon catheter has been placed correctly in the stenotic area, it is briefly inflated to the maximum pressure specified by the manufacturer. This process is documented (usually 6 frames/s). Then the balloon is deflated and the balloon catheter is withdrawn with the guidewire remaining. An angiography catheter is then placed at the site of the former stenosis, the pressure is measured and an angiography performed. If the stenosis is not sufficiently widened, the dilation procedure may be repeated with a larger or harder balloon or a cutting balloon, or a stent is implanted.
Complications
Uncontrolled tearing of the vessel wall may develop during the dilation process. There is a risk of dissection or rupture, later thrombosis, embolism or even restenosis depending on the tissue repair process. In valvular stenosis, accidental laceration or avulsion of a leaflet may cause severe regurgitation.
Treatment
The procedure is often followed by heparinization for 1 to 2 days and by giving low-dose aspirin (3–5 mg/kg orally) to avoid excessive thrombosis, embolism, or vascular occlusion.
Checkups
Depending on the treated site (valve or vessel), echocardiography checkups are usually sufficient, but sometimes an MRI is also necessary.
Valvular Aortic Stenosis
Indication
Overall, the indication criteria for balloon valvuloplasty of the aortic valve are still evolving as, on the one hand, the interventional results are promising while, on the other hand, the risk of the procedure is relatively low. Generally accepted indications are:
Gradient related (Doppler gradient > 50 mmHg)
Cardiac decompensation or decreasing left ventricular function
Increasing cardiac overload (left ventricular hypertrophy, poor diastolic function)
ST segment changes under stress
A still-competent aortic valve is a precondition (aortic regurgitation ≤ 2°)
Preliminary examinations
An ECG that is no more than 2 months old is recommended; if it is suspicious, a 24-hour Holter ECG or exercise ECG is also recommended. Moreover, a recent echocardiography may be useful including determination of the valve annulus diameter, anatomy of the valve (bicuspid, tricuspid), mean and maximum gradient, aortic regurgitation, left ventricular function, mitral regurgitation, isthmus, ductus, and exclusion of a Shone complex.
Risks/patient information
The overall risk is below 10%, including the risk of rupture of the valve, acute and severe aortic regurgitation, emergency surgery with possible valve replacement, myocardial ischemia, arrhythmias, AV block, development of mitral regurgitation, infection/endocarditis, perfusion disorder, or vascular occlusion at the arterial puncture site.
Procedure
In small children, an antegrade approach (across an ASD or a patent foramen ovale) may be attempted, otherwise a retrograde approach via an arterial puncture should be undertaken.
Cardiac catheterization/treatment
First, pressure measurement and ascendogram, measurement of the valve annulus, probing and angiography of the left ventricle (Fig. 24.1). Then switch the catheter to a long exchange wire, then place the balloon catheter. Balloon dilation (balloon diameter 80–110% of the valve annulus diameter). Check of pressure in the left ventricle, re-angiography of the left ventricle and again ascendogram (aortic regurgitation?). In older children, pacemaker stimulation of the right ventricle. For this, quick VVI stimulation (300–400/min) during balloon dilation can briefly reduce ejection from the left ventricle due to tachycardia so the balloon is not displaced too much by the pulsation of blood flow.
Heparinization
Administration of 100 IU/kg intravenously during cardiac catheterization, then 400 IU/kg/d as a continuous infusion until the morning of the second day.
Echocardiography after cardiac catheterization
Possible aortic regurgitation, the mean and maximum residual gradient, left ventricular function, and a possible new occurrence of mitral regurgitation should be noted.
Medication
Aspirin 3 to 5 mg/kg for 3 months, endocarditis prophylaxis for 6 months if needed.
Critical Aortic Stenosis of the Neonate
Indication
Owing to the typical hemodynamic situation (ductal-dependent systemic perfusion) and the fact that the left ventricular function is usually considerably impaired, there is an indication regardless of the gradient in a still-competent aortic valve (aortic regurgitation < 2°).
Preliminary examinations
Patients are usually admitted under intensive care conditions; they are very often ventilated, critically ill newborns. ECG, detailed echocardiography, chest X-ray, and preparation for surgery with cardiopulmonary bypass is necessary.
Echocardiography
Visualization of the valve annulus diameter, aortic regurgitation, valve anatomy (bicuspid, tricuspid), mean and maximum gradient, left ventricular function, mitral regurgitation, isthmus, ductus arteriosus, pulmonary artery diameter, exclusion of a Shone complex.
Preparation
Preparation should be the same as for cardiopulmonary bypass surgery as dictated by hospital standards. If necessary, this may include first inserting an arterial catheter (umbilical) and a central venous catheter, catecholamine treatment, and in every case prostaglandin treatment. If still possible, give umbilical care (keep navel moist) so that antegrade cardiac catheterization via the umbilical vein remains possible.
Risks/patient information
The risk is high because the patient is usually a critically ill neonate with impaired ventricular function. Risks include a valve rupture, acute and severe aortic regurgitation, emergency surgery, possibly with valve replacement (homograft implantation) or Ross procedure, myocardial ischemia, arrhythmias, AV block, mitral regurgitation, infection/endocarditis; for an arterial puncture, perfusion disturbance or vascular occlusion.
Procedure
Whenever possible, an antegrade approach across an ASD or a patent foramen ovale should be attempted, possibly via the umbilical vein, otherwise a retrograde approach via an arterial puncture should be undertaken.
Cardiac catheterization/treatment
Ascendogram, measurement of the valve annulus, probing and angiography of the left ventricle, switch to an exchange wire, then balloon dilation (balloon diameter max. 80–100% of the valve annulus diameter), check of left ventricular pressure, angiography of the left ventricle, ascendogram (aortic regurgitation?). In a critically ill child, the dilation is often performed based solely on echocardiography findings and without pressure measurements or angiographies.(Fig. 24.2).
Monitoring
Intensive care monitoring, catecholamines and prostaglandin reduced depending on the clinical status, regular echocardiography checkups.
Heparinization
Administration of 100 IU/kg as an intravenous bolus during cardiac catheterization, then 400 IU/kg/d in a continuous infusion until the morning of the second day.
Echocardiography after cardiac catheterization
Aortic regurgitation, mean and maximum residual gradient, left ventricular function, mitral regurgitation, mitral stenosis, PDA, isthmus, exclusion of a Shone complex.
Note
The balloon valvuloplasty of critical aortic stenosis in the neonate is carried out regardless of the gradient. The children often need an adaption phase of varying length until the left ventricle has recovered sufficiently. Long-term catecholamine support and possibly ventilation are often required.
Supravalvular Aortic Stenosis
Indication
In a supravalvular aortic stenosis, an indication for intervention is relatively rare. The results for a “classic” supravalvular aortic stenosis in Williams–Beuren syndrome are poor. Postoperative supravalvular stenosis (e.g., after Damus–Kaye–Stansel anastomosis is practically the only indication):
Gradient related (Doppler gradient over 50 mmHg)
Cardiac decompensation or decreasing ventricular function
Increased cardiac overload
ST segment changes under stress
Preliminary examinations
ECG no more than 2 months old; 24-hour Holter ECG and exercise ECG only if the most recent ECG was abnormal.
Echocardiography
The following questions should be answered: valve annulus diameter, aortic regurgitation, anatomy of the stenosis, mean and maximum gradient, left ventricular function, isthmus, other stenosis of the head and neck vessels.
Risks/patient information
The risk is less than 5%, dissection and coronary problems could lead to myocardial ischemia, arrhythmias, and AV block; perfusion disturbance or vascular occlusion for arterial punctures.
Procedure
In univentricular hearts, an antegrade approach may be possible (across an ASD or the ventricle), otherwise a retrograde approach via an arterial access is used.
Cardiac catheterization/treatment
Ascendogram, measurement of the valve annulus, probe of the left and right ventricle, angiography, switch to exchange wire, balloon dilation, check of ventricular pressure, ventricular angiography, ascendogram (aortic regurgitation?).
Monitoring
Routine monitoring and a 12-lead ECG after the intervention, additional monitoring on an ECG monitor with ST-segment analysis, 24-hour Holter monitoring only if the ECG is abnormal.
Heparinization
Administration of 100 IU/kg as an intravenous bolus during cardiac catheterization, then 400 IU/kg/d as a continuous infusion until the morning of the second day, and aspirin 3 to 5 mg/kg for 3 months.
Echocardiography after cardiac catheterization
Aortic regurgitation, mean and maximum residual gradient, ventricular function, and wall dyskinesia should be documented.
Medication
Aspirin 3 to 5 mg/kg for 3 months, endocarditis prophylaxis for 6 months.
Mitral Stenosis
Indication
Overall, balloon valvuloplasty of the mitral valve is only rarely indicated in children in Europe. From a global perspective, it is a common procedure after rheumatic fever or—rarely—because of endocarditis. The results are satisfactory for stenosis of previously normal valves. In primarily anomalous valves (e.g., parachute or hammock valve), or especially after surgical reconstruction, the results are unsatisfactory. Indications are:
Gradient dependency (Doppler gradient of 10 mmHg)
Signs of “left decompensation” (pulmonary edema, pulmonary congestion)
Atrial arrhythmias
Ectatic left atrium with thrombi
Intermittent pulmonary edema—congestive cough
Significant pulmonary hypertension
Progressive deterioration of physical capacity
Preliminary examinations
ECG no more than 2 months old, 24-hour Holter ECG and exercise ECG only if the most recent ECG was abnormal, cardiopulmonary exercise test for larger patients.
Echocardiography
Valve annulus diameter, anatomy, mean and maximum gradient, left ventricular function, mitral regurgitation, ASD or patent foramen ovale, and pulmonary hypertension should be investigated.
Risks/patient information
Risk less than 5%, rupture of the valve, acute severe mitral regurgitation (often not well tolerated), emergency operation (low risk), valve replacement, dissection, tamponade, death, myocardial ischemia, arrhythmias, AV block, infection/endocarditis.
Procedure
Antegrade approach through the femoral veins.
Cardiac catheterization/treatment
Transseptal probing of the left atrium , if necessary by transseptal puncture; rarely, left atrial angiography and pressure measurement, probe of the left ventricle with wire, insertion of the balloon catheter (e.g., Inoue balloon) and dilation, check of left atrial and left ventricular pressure, angiography of the left ventricle (mitral regurgitation?).
Echocardiography after cardiac catheterization
Mitral regurgitation, mean and maximum residual gradient, left ventricular function, pulmonary hypertension.
Medication
Aspirin 3 to 5 mg/kg for 3 months, endocarditis prophylaxis for 6 months if necessary, possibly treatment/prophylaxis of rheumatic fever.
Note
Balloon valvuloplasty of the mitral valve has become very rare in Europe, but in other countries with more frequent rheumatic fever, it is one of the most commonly performed interventional procedures. Congenital mitral valve defects are not successfully treated by interventional catheterization.
Balloon Valvuloplasty of Coarctation of the Aorta
Indication
Overall, the indication criteria for balloon valvuloplasty of coarctation of the aorta are evolving as, on one hand, the results are promising while, on the other hand, the risk of the procedure is relatively low. In neonates and children under 6 months, the recurrence rate is unsatisfactory (elastic ductal tissue), which is why this group is usually treated surgically. Clinical as well as pharmacological exercise tests (e.g., orciprenaline stress test) are often helpful in determining the indication. Accepted indications are:
Doppler gradient well above 20 mmHg
Absent or severely attenuated inguinal pulses
Blood pressure difference arm/leg well above 20 mmHg
Hypertension (exercise test, long-term blood pressure measurement)
Cardiac decompensation or decreasing left ventricular function
Increasing cardiac overload (left ventricular wall thickness)
ST segment changes on exertion
Increasing aortic regurgitation
Preliminary examinations
ECG not more than 2 months old, echocardiography; if possible, in older children, MRI with 3D reconstruction and dimensions of the aortic arch and isthmus.
Echocardiography
Visualization of the diameter of the arch, the coarctation, the descending aorta at the diaphragm level, aortic valve, valve annulus diameter, aortic regurgitation, mean and maximum gradient, left ventricular function, mitral regurgitation, isthmus, ductus arteriosus, possibly gradient under stress, exclusion of a Shone complex.
Risks/patient information
The risk is well below 5%. There are a few patients beyond the neonatal age who still require surgery owing to insufficient success of catheter intervention (elastic tissue). Possible complications are dissection due to massive overdilation, aneurysm formation, hematothorax, transfusion, chest tube, emergency stent implantation, emergency surgery, death, paraplegia (extremely rare). The restenosis rate is over 20% (same as for a surgical procedure), and perfusion problems or vascular occlusion may occur after the arterial puncture. There is typically mild chest pain after the intervention.
Procedure
In young children, an antegrade approach (across ASD or patent foramen ovale) may be possible. In most patients, however, a retrograde approach via an arterial puncture is undertaken access is used.(Fig. 24.3).
Cardiac catheterization/treatment
Ascendogram, measurement of each arc segment and determining the anatomy, pull-back pressure, possibly orciprenaline stress test (Alupent), switch to an exchange wire, balloon dilation, control angiography, pull-back pressure, possibly another pharmacological stress test.
Monitoring after dilatation
Additional monitoring and documentation of blood pressure at least every 30 minutes through the night and for 24 hours if any questions remain, blood pressure, apply generous analgesia and, systematic antihypertensive therapy (e.g., carvedilol, ACE inhibitors).
Heparinization
Administration of 100 IU/kg as an intravenous bolus during cardiac catheterization, then 400 IU/kg/d in a continuous infusion until the morning of the second day.
Checkups after cardiac catheterization
Echocardiography: documentation of mean and maximum residual gradient, left ventricular function, perfusion of the inguinal vessels.
MRI: Routinely after 6 months to document the result as well as to rule out aneurysms.
Medication
See Aortic Stenosis.
Dilation of Coarctation of the Aorta of the Neonate
Indication
There are currently very few generally accepted indications for the interventional treatment of the coarctation of the aorta of the neonate. Children are not usually treated by interventional catheterization before the age of 6 months because the risk of recurrence is very high (over 70%). The procedure is indicated for sick newborns with additional problems that impede rapid surgery (e.g., necrotic enterocolitis, unclear syndromes, brain hemorrhage) or in critically ill children with cardiac decompensation, as well as children with cardiomyopathy and mild coarctation of the aorta.
Preliminary examinations
Cranial ultrasound (to rule out brain hemorrhage), other organ diagnostic workups under intensive care conditions (the neonate is usually ventilated and critically ill). ECG, echocardiography, chest X-ray, surgical preparation, prostaglandin treatment, possibly catecholamines.
Echocardiography
The diameter of the aortic arch, coarctation of the aorta, descending aorta at diaphragm level, aortic valve, valve annulus diameter, aortic regurgitation, valvular anatomy, mean and maximum gradient, left ventricular function, mitral regurgitation, isthmus, ductus arteriosus should be documented; a Shone complex should be ruled out.
Preparation
Same as for cardiopulmonary bypass surgery; if necessary, insertion of an arterial catheter (umbilical) as well as a central venous catheter, catecholamine treatment, prostaglandin treatment obligatory in all patients.
Risks/patient information
The risk is high as the neonate is critically ill. There is a very high recurrence rate due to elastic ductal issue. Dissection in massive overdilation, hematothorax, transfusion, chest drainage, emergency stent implantation, emergency surgery, death, and perfusion disturbance or vessel occlusion and rupture after arterial puncture may occur. Surgery is usually required soon afterward as the intervention is only a palliative measure.
Procedure
An antegrade approach may be possible (across an ASD or patent foramen ovale), but in most cases a retrograde approach via an arterial access is used.
Cardiac catheterization/treatment
Ascendogram, measurement of each segment of the arch and assessment of the anatomy, change to wire, balloon dilation (Fig. 24.4). Switch to an exchange wire, control angiography, leave arterial catheter in place. Dilation may also be performed also based only on the echocardiography.
Monitoring
Use intensive care monitoring, taper catecholamines, discontinue prostaglandin, carry out regular echocardiography checkups. In addition, blood pressure is monitored every 30 minutes overnight, perfusion of the legs should be monitored with continuous pulse oximetry. Early enteral nutrition intake should be instigated on the same day, and possibly antihypertensive treatment (e.g., diuretics, ACE inhibitors, carvedilol).
Heparinization
Administration of 100 IU/kg as an intravenous bolus during cardiac catheterization, otherwise proceed according to intensive care guidelines and patient need.
Echocardiography after cardiac catheterization
Access aortic regurgitation, mean and maximum residual gradient, left ventricular function, mitral regurgitation, mitral stenosis, PDA, exclusion of a Shone complex.
Stent Implantation in Coarctation of the Aorta
Indication
The indication criteria for stent implantation as treatment of coarctation of the aorta are still evolving because the results are promising and the risk of the procedure is low—also due to the development of new materials with small sheath sizes. The issue as to whether covered stents should be used or not, is still under discussion.
In small children, stents are used only as an emergency solution intraoperatively in hypoplastic vessels. Coronary stents or small vascular stents are used as bailout options in neonates or small children. Specifically designed stents for neonates that can be redilated to adult size are under clinical development. Exercise tests are useful for determining the indication in so called “mild coarctations”. The acceptable indications for body weight of at least 20 kg are the same as for unstented coarctation of the aorta:
Doppler gradient well above 20 mmHg
Absent or severely attenuated inguinal pulses
Blood pressure difference arm/leg well above 20 mmHg
Hypertension (exercise test, long-term blood pressure measurement)
Cardiac decompensation or decreasing left ventricular function
Increasing cardiac overload (left ventricular wall thickness)
ST segment changes under stress
Increasing aortic regurgitation
Preliminary examinations
ECG no more than 2 months old, current echocardiography with documentation of the diameter of the vessels, MRI with 3D reconstruction and dimensions; possibly, exercise tests, 24-hour blood pressure monitoring.
Echocardiography
The diameter of the aortic arch and coarctation, the descending aorta at diaphragm level, aortic valve, valve annulus diameter, aortic regurgitation, valvular anatomy, mean and maximum gradient, left ventricular function, mitral regurgitation, isthmus, ductus arteriosus should be documented; a Shone complex should be ruled out.
Risks/patient information
The risk is less than 5%, possible dissection due to massive overdilation, hematothorax, transfusion, chest drainage, aneurysm formation, emergency implantation of covered stents, emergency surgery, death, paraplegia (rare), low rate of restenosis (< 5%), possibly two-stage procedure with re-dilation in 6 to 12 months, perfusion disorders or vessel occlusion for an arterial puncture. Typically there is mild chest pain after the stent implantation.
Procedure
Usually an antegrade approach via an arterial puncture is attempted.
Cardiac catheterization/treatment
Ascendogram, measurement of each arch segment and determination of the anatomy, pull-back pressure, possibly orciprenaline (Alupent) stress test, switch to an exchange wire (balloon dilation, control angiography), insertion of the long transport sheath, control angiography using hand injections, stent implantation (Fig. 24.5), pull-back pressure, possibly repeated pharmacological stress test. In larger children and arch stenosis, pacemaker stimulation (rare) may be instigated to ensure proper stent placement.
Monitoring
Heparinization, medication, and monitoring are the same as for balloon dilation.
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