Echocardiography and Electrocardiography
Echocardiography and electrocardiography are the standard investigation techniques in modern cardiology. Echocardiography is a non-invasive method that visualizes the heart and enables the physician to appreciate almost all structural disorders. Electrocardiography detects electrical activity occurring in the heart and thus states the conductivity condition of the myocardium. The technique of electrocardiography is non-invasive, reproducible and inexpensive making these two diagnostic procedures inevitable when investigating the heart.
Congenital heart disorders, especially complex, are typically diagnosed in infancy or early childhood because these cardiac defects expose a heart murmur, cyanosis and other prominent troubles. However, some congenital disorders do not manifest until adulthood and thus may be diagnosed rather late. Therefore, the health care giver must be familiar with certain cardiac conditions that adults may experience. A patent foramen ovale is a small structural cardiac condition of congenital origin that rarely causes any problems, but under certain conditions (such as diving) may contribute to decompression illness. Echocardiography clearly detects the patent foramen ovale and enables physicians to consider appropriate interventions.
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Arrhythmias are disorders of heart rhythm and/or conductivity. Arrhythmias of acquired origin usually develop in the elderly when arterial hypertension and ischemic heart disease take place, while congenital arrhythmias may appear at any age. Arrhythmias are the cause of morbidity and mortality, so when suspecting an arrhythmia, an electrocardiogram must be performed as soon as possible to evaluate the contribution of arrhythmia to an individual’s health condition.
Echocardiography and electrocardiography are particularly beneficial for individuals with structural or electrical disturbances of the heart. These tests carry zero complications, but show high specificity and sensitivity in detecting various heart troubles.
A 25-year old male reports dizziness, weakness and palpitation shortly after diving. The client started scuba diving three months ago. He developed these complaints a couple of times within the previous three months. The instructor explained the danger of decompression sickness and urged the man to follow the decompression procedures strictly, but the troubles persisted. The instructor suspects heart abnormalities that result in either right-to-left shunt or arrhythmias.
The patient reports no poor habits. He is married, and has one child. He is a nonsmoker, drinks 1–2 glasses of red wine per month. His elder brother is a military and has not any health complaints. His parents are alive and do well. His farther has arterial hypertension and takes ACE inhibitors regularly. He is not allergic to anything.
On admission, the client is seen as a pleasant man, no apparent distress. The skin is warm and dry with normal turgor. Vital signs: Temp 98.0 oF, HR 80 bpm, BP 125/78 mmHg, RR: 15pm. Head, eyes, ears, nose, and throat: none. Resp: none. Cardiovascular: regular rate and rhythm, II/VI systolic ejection murmur. Abdominal: liver and spleen not palpable. CNS: alert & oriented.
ECHO: patent foramen ovale d- 3mm with a left-to-right shunt in quiet position. ECG: sinus rhythm, normal voltage of the P-wave and QRS complex, PQ- and ST-intervals of normal length. The 24-hour Holter monitoring did not detect any threatening arrhythmias. Laboratory: hemoglobin, red blood cells, potassium within normal range.
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Patent Foramen Ovale
A patent foramen ovale is an opening in the heart. Normally, the left and right atriums are separated by the interatrial septum. This is not so in the fetus. In the intrauterine period, humans do not breathe with their lungs and the blood circulation is considerably different from that of the newborn. The fetus diverts his blood from placenta through the right atrium to the left atrium via the foramen ovale. After birth, the lungs expand and the blood from the right atrium flows to the right ventricle only. The interatrial septum becomes closed. Some babies lack tissues around the foramen ovale and it is not completely closed. The hole between the atriums remains, called the patent foramen ovale.
Normally, patent foramen ovale causes no complaints or troubles because at rest the shunt is from the left to the right atrium (Lynch & Bove, 2009). However, the divers, especially if dive deeply, produce numerous gas bubbles in their venous system when come up. Should the interatrial septum be intact, the bubbles are filtered by the lungs, but when the foramen ovale is patent, the bubbles flow from the right atrium to the left and reach the brain and neurological effects may follow. In 1986 it was recognized that patent foramen ovale causes gas embolism in scuba divers (Torti et al., 2004). Current findings state that the presence of a patent forman ovale increases the risk of cerebral emblism by 4.5 times (Lynch & Bove, 2009), and the bigger the hole, the higher the risk (Torti et al., 2004).
Echocardiography is an imaging method in cardiology. Ultrasonography is based on the properties of ultrasound to penetrate the skin and other tissues and reflect from the more dense tissues. Echocardiography is the application of ultrasound to the study of the heart anatomy.
The physical aspects of echocardiography are the following. A piezoelectric ceramics vibrates to produce ultrasound. The waves are directed through the skin to the organ of interest (the heart). The structures of the heart have various density. For example, the blood has properties density from those of the myocardium or the valves. Thus, the ultrasound waves will reflect with different angles, power, etc. The piezoelectric crystal accepts the echo waves and the computer analyzes the electrical impulses from the transducer. As a result, the operator receives a non-invasive image of the heart.
Echocardiography allows the operator to visualize the interatrial septum. The septum may be intact, meaning there are no holes within it. If the patent foramen ovale is present, the image will clearly give a signal loss in the compact wall.
Echocardiogram allows to state the diameter of the patent foramen ovale, exclude other disorders of the interatrial septum (absence of the interatrial septum, atrial septal defect, aneurysm of the interatrial septum) and structural abnormalities of the heart. Doppler analysis shows the direction of the blood flow through the patent foramen ovale (Sykes & Clark, 2013). The cardiologist will see the left-to-right shunt at rest and right-to-left shunt shortly after exercice or at exerction imitating the decompression disease (Torti et al., 2004). To make the diagnosis even more specific, cardiologists inject saline intravenously and watch for the patency of the foramen ovale. Small holes cross over only a few bubbles, while bigger holes shunt a cloud of bubbles suggesting the risks.
Echocardiography carries no risks, and there are no contraindications. This method is highly accurate, it is reproducible and it gives high percentage of accuracy. Contrast echocardiography in diagnostics of the patent foramen ovale gives an almost 100% specificity and sensitivity (Torti et al., 2004; Sykes & Clark, 2013).
Electrocardiography detects electrical activity by application of electrodes to the skin in a certain order. The elctrodes pick up electrical impulses that occur during depolarisation and repolarisation of the heart cells. The voltage that ocsilates is recorded on the paper. The spatial direction of the voltage impulse is difficult to describe accurately, so at least 12 leads (spacial outputs) are applied to the body so that horizontal, vertical and frontal planes are assessed. The paper lays the cumulating electrical waveform, the latter is critically appraised .
Typical electrocardiogram consists of waveforms. The waveform consists of peaks and intervals between them. The first peak is called the P-wave, corresponding to the atrial electrical activity. The next group of peaks, called the QRS-complex, depicts the ventricles. The ventricles end up their electricity with the T-wave. The peaks are separated by PR- and ST-segments (Rajmuf, 2013).
The P-wave of the electrocardiogram detects how active the atriums are. For example, it states their regularity or activity. Each atrial contraction is normally followed by ventricular activity. Thus, after the PR interval QRS complex starts. ST segment depicts the contraction of the ventricles and ventricular relaxation gives the T wave. All these waves and intervals must follow certain time and sequence patterns. Moreover, their form is not random. All these data in combination allow the cardiologist to appreciate the electrical activity of the heart.
An electrocardiogram at rest gives a perfect scope of persistent arrhythmias. The sensitivity is generally very high, but some complex arrhythmias do not produce any electrical abnormalities at rest, so the electrocardiogram is performed at exercise or under pharmacological load (Levine, 2013). This is the so-called Holter monitoring. The patient carries a small device that records his electrocardiogram second-by-second for 24 hours.
The key idea of the Holter monitoring is to catch the arrhythmia at normal physical or emotional exertion. It is performed when the rest electrocardiogram does not answer all questions regarding the clinical evidence of heart problems (Mayo Clinic, 2011). Since the Holter monitor is an electricity-recording machine, the client must not swim with it, but other activities are not prohibitied. After the test period is over, the device is taken off and the data is analyzed by computer programs to detect dangerous episodes.
Electrocardiography has become one of the most commonly used diagnostic methods in medicine due to its simplicity, low cost and reproducibility. It is particularly useful and indicated for all individuals who undergo cardiac rhythm evaluation (Levine, 2013). Electrocardiography provides the information that no other method can give concerning electrical phenomena of the heart (Kadish, Buxton, Kennedy, & Knight, 2001). No contraindications or side effects exist (Levine, 2013). However, sophisticated electrocardiograms are performed only under strong clinical supervision (Levine, 2013).
Diagnostics in cardiology was based on personal skills in ancient times. The physicians performed ausculatation of the heart and palpation of the chest. Together with pulse appreciation and neck vessels examination, these were all the doctor could use to deduce the heart condition. Technical achievements of the 20th century introduced numerous investigation methods that add to the personal skills of the health care givers. Instrumental diagnostics gives information unavailable in the previous centuries. Echocardiography, introduced in the 1970s and electrocardiograhy that started in the 1900s are two diagnostic procedures performed on almost all pateints undergoing heart investigation.
Echocardiography enables to visualize the heart and major vessels, while electrocardiography inspects electrical patterns occuring during the cardiac cycle. In combination these methods give an almost complete impression of the central hemodynamics.
Echocardiography and elcetrocardiography share certain common features:
- both techniques are non-invasive, carry no harm to the organism (no X-rays or toxic effects), have no contraindications. This fact allows the physician to use them on a routine basis and repeat as many times as necessary
- any structural abnormality of the heart may be considered as an indication for an ECHO, while any arrhytmia/suspicion is an indication for an ECG
- the tests are particularly beneficial because they are rather independent on the operator. All ECHOs and ECGs can be stored and reviewed by experts. Thus, even if the operator lacks skills, the patient will eventually have his heart condition diagnosed properly
- the specificity and sensitivity of these diagnostic interventions is not low, but can be enhanced. Injecting saline during ECHO helps to visualize intracardiac shunts more precisely suggesting physiological consequences of the patent foramen ovale. Electrocardiogram can be recorded for long periods of time to catch ‘hidden’ arrhytmias.
- echocardiography is the basis for evaluating the heart morphology. Even if further investigation methods need to be applied, any heart diagnostics starts with ECG and ECHO (MGH Ultrasound, 2014).
Electrocardiography is the golden starndard for non-invasive diagnostics of arrhytmias and conduction disorders (Kadish et al., 2001).
Combination of echocardiography and electrocardiography is enough in typical situations to provide rationale for treatment. Generally, a patent foramen ovale is not a contraindication to diving (Lynch & Bove, 2009). Available literature suggests 30% to 40% of the population has this hole, but only a small proportion of divers do develop cerebral embolism and the decompression disease. Thus, routine screening of divers for patent foramne ovale has not been indicated yet. Albeit if the patent foramen ovale is large enough to pass many bubbles on contrast echocardiography, it is recommended either to keep the person from diving or close the hole with a special device (Torti et al., 2004). Thus, ECHO and ECG taken in the young male are sufficient to give recommendations regarding his further sport activities.
Echocardiography and electrocardiography are the diagnostic tools of choice in management cardiac conditions. The health care giver should be familiar with the basic principles of ECHO and ECG since these methods are extremely popular and useful in modern medicine.