CONGENITAL HEART DISEASES  

Clinical features
The physician who, on the basis of symptoms presented by the child and the abnormalities brought out by the examination, suspect a heart disease disposes of different means to make a precise and accurate diagnosis and set the appropriate treatment. Some investigation like ECG, chest, X-Ray, and Echocardiography are relatively simple because they are performed outside the child¹s body. Other investigations like cardiac catheterization and angiocardiography are more complex.

Electrocardiogram (ECG) informs us on heart rate, the regularity of rhythm, atrial and ventricular contraction, thickness of atrial and ventricular septal musculature, dimension of atrial and ventricular chambers. For example in a child with a pulmonary stenosis, to send blood in pulmonary the right ventricle should work at a pressure increased four or five times compared to normal; it finds the strength by hypertrophy and in this the ECG shows a right ventricle hypertrophy. A particular type of ECG is the dynamic ECG (Holter) which allows to record ECG for 24 hours on a tape using a portable tape recorder connected to the patient by adhesives electrodes. For the whole duration of the record the patient or his parents fill up a diary where they note the activities performed and the symptoms. The tape is analyzed by a computer which computes minimum, maximum and mean heart rate, recognizes and computes possible arrhythmia¹s. These can be review by the physician and print on paper. Holter is irreplaceable for the study of cardiac rhythm.

Chest X-Ray was widely used, before the advent of echocardiography, in the evaluation of a child with suspected heart disease. Actually its use is limited but is irreplaceable when we want to have an evaluation of heart global size and the effects of heart disease on pulmonary circulation.

Echocardiography is the highest improvement of cardiovascular diagnosis in the last 20 years. Echocardiography technologies, Doppler and color-Doppler are joined in the same machine, which is the only one able to give so wide, precise and accurate informations on heart anatomy. Echocardiography is based on ultrasounds properties to penetrate tissues being reflected by obstacle or tissues density difference. Ultasounds are produced by a probe, which also functions as receiver of reflect ultrasounds, that is applied on the chest. The beam is elaborated and transformed in images. Two-dimensional echocardiography allows the study of all moving cardiac  structures (vena cava, atria, ventricles atrial and ventricular septum, arteries rising from the heart), the sizing of cardiac chambers and vessels, the evaluation of contractility of myocardium. Doppler investigation is another application of ultrasound based on Doppler effect, a phenomenon described about a century ago by a Czech physicist. When an ultrasounds beam encounters a target in motion in this case red blood cells, it is reflected with a different frequency proportional to the speed of the target. The variation of frequency is indicated as fluximetric graph which shows direction and speed of blood flow.
-Fig. 3.4

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Blood speed will be increased if it should cross an obstacle. From the data of the speed it is possible to compute the pressure in the cardiac chambers, a data which possible to obtain only by cardiac catheterization before the advent of echo-Doppler. Even the color Doppler is based on Doppler effect, but the informations collected are codified in colors and added to the two-dimensional echographic image. This technology allows to see blood flow inside heart structures in motion. The blood flow from the probe is codified in blue and the blood flow toward the probe is codified in red. When the flow is increased green or yellow is added to the codified color, giving a mosaic of colors indicative of abnormal flow. Echocardiography allows the study of heart anatomy and to collected informations and data which could be obtained only with cardiac catheterization before Doppler echocardiography. Echocardiography is an exam free of risk that can easily be performed and repeat every time it is necessary. In a lot of case of congenital heart diseases, informations collected by echocardiography are enough to allow the children to undergo surgery safety. A recent development of ultrasounds technology in pediatric cardiology concerns the transesophageal echocardiography, a particular probe is introduced in the mouth and located in esophagus. This is a preference location to observe the heart because esophagus is adjacent to cardiac structures and ultrasounds do not have to cross muscles or bones. The images extraordinarily clear and clean. It is reserved for selected cases and requires sedation.

-Fig. 3.5
Flow curves obtained by echo-Doppler-.

Fetal echocardiography allows the diagnosis of cardiac malformation in fetus.
It is possible to see clearly  fetus heart anatomy and function, discover the major part of malformations and diagnose fetal arrhythmia¹s.
Fetal echocardiography is performed on women with one of these three indications:

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family history of heart malformations in parents or other sons;
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fetal arrhythmia or fetal malformation discovered during fetal echography
- history of heart disease, diabetes, infections or exposure to teratogenic agent.

Fetal echography is recommended between 18th and 20th  week of pregnancy, it is safety and able to show, not all the fetal heart defects but the severe cardiac abnormalities  In about 7% of the fetal echocardiography performed on the indications above a cardiac defect is found. Sometimes knowing in advance the nature of the defect is useful to start a treatment immediately at birth, for some malformations termination of pregnancy will be considered. An fetal arrhythmia can be treated during the pregnancy to avoid heart failure.

Cardiac catheterization is an accurate diagnostic exam performed in a special laboratory called laboratory of hemodynamic,  with catheters which introduced in arteries and veins reach the heart. The child who undergoes cardiac catheterization receive sedatives by intramuscular or intravenous injection and sleeps during the procedure. Through a percutaneous entry point, after local anesthesia, catheters are introduce in femoral vein and artery and push through the vessels until they reach the heart; catheter are hollow tubes with a diameter ranging from 1,35 mm to 2,2mm for the children. The catheter in the femoral vein arrives in the right atrium and can be guided into the right ventricle and the pulmonary artery (right catheterization);The catheter in femoral artery joins aorta and can be guided through the aortic valve in left ventricle (left catheterization). The catheters can be passed through communications between right and left side of heart. Catheters motion is controlled under fluoroscopy. The catheters allow the gauge of pressure and blood oxygen contain in the cardiac chambers.

-Fig. 3.6
Echo-color-Doppler image; the color indicates blood flow; red for the blood flowing toward  the probe, blue for the blood flowing away from the blood-.

These data are use to confirm the presence of a cardiac abnormality. During cardiac catheterization angiocardiography is performed by injection of contrast material into specific chamber; the motion of the contrast in the heart and vessels is filmed with X-Ray. Angiocardiography allows a precise definition of the defect. At the end of the procedure the pediatric cardiologist extracts the catheters and exerts pressure on the entry point for about 10 minutes until there is no more bleeding.
During the last 15 years with the advent and the progress of echocardiography the number of diagnostic cardiac catheterization is deceased, but remains irreplaceable when physiological informations like pulmonary resistance are necessary or when it is necessary to quantify the flow through an abnormal communication. Angiocardiography allow the evaluation of some details that cannot be adequately investigated with echocardiography. In this case cardiac catheterization and angiocardiography are essential to prepare the patient to surgery. Cardiac catheterization is not free of risk; more than 98% of the procedure are carry out without complication. In about 1,5% there are complications which concern neonate extremely severe for who cardiac catheterization is fundamental for a complete diagnosis. Most of the complications are treatable but some can be fatal. The global mortality of cardiac catheterization is about 1/1000, but considering only the neonates it¹s higher. The parents of a child who should undergo cardiac catheterization should be informed on the risks of the procedure and they should give their consent. Generally hospitalization last two days; before discharge the child is reevaluated with particular attention to the arterial venous circulation on the entry point side. After 3 or 4 days he can return to his normal life.

Magnetic resonance imaging allows to obtain two-dimensional images of heart and vessels rising from the heart. Actually it is used to complete echocardiography and angiocardiography in particular situations.

Electrophysiologic study can be necessary in some patients with cardiac arrhythmia¹s. This study is performed with special catheters which allow the study of electrical activity of the heart from within the heart. It is useful to make an accurate diagnosis of the type of arrhythmia and set the adequate therapy.

Exercise testing
The ability to perform work or to exercise is one of the basic function of live affected by many diseases and states Accurate and reproducible measurement of work performance or exercise capacity provides a means to assess the effects of treatment, severity of disease, in some instances, to identify previously unrecognized disease and assess one aspect of quality of life. Exercise test consist in the record of ECG during the performance of a physical exercise, to assess the cardiovascular system during effort, with particulary regard to the heart rate, blood pressure, and ECG anomalies eventually related to symptoms. In childhood exercise testing can be required for patients who had syncope during effort, tachycardia of unknown origin, to assess arrhythmias.
Exercise test is perform, recording ECG and blood pressure, with the patient running on a travelator (children) or riding a bicycle ergometer (adolescents and adults). The test is performed in an equipped environment, suitable even for emergency (drugs, defibrillator, oxygen) with physicians and nurses experts in the field and well trained to front the rare eventuality of threatening arrhythmias.


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