What Is an ECG (Electrocardiogram)? Why Is an ECG Performed?

ECG (Electrocardiography) is a fundamental cardiological diagnostic test that detects the heart’s natural electrical impulses from the surface of the skin and converts them into a time and voltage graph. ECG is routinely performed to evaluate the rhythm pattern of the heart, detect blood supply defects caused by vascular blockages, and assess the general functioning of the heart muscle. This method, which maps heart health within seconds, makes structural or electrical problems visible at the earliest stage. These millimetric graphs, which directly reflect the organ’s working performance, identify possible circulatory disorders, create an opportunity for early intervention, and are considered one of the most reliable guides in the diagnosis of cardiovascular diseases.

How Is the ECG Procedure That Records the Electricity of Our Heart Performed?

When you experience discomfort and visit a healthcare institution, ECG recording is one of the primary methods we use at the first moment when a heart-related problem is suspected. No special preparation is required for the procedure. You are only asked to lie comfortably on your back on a bed. Remaining calm, not breathing deeply, and not speaking are important so that the device can capture those delicate electrical changes in the clearest possible way. Because contractions create electrical signals not only in the heart but also in skeletal muscles, being cold, shivering, or moving may cause other waves to interfere with the graph. Small electrodes are attached to specific points on the body, especially around the rib cage and on the wrists and ankles. Clean and dry skin ensures full contact with these electrodes and allows for a much higher-quality reading. During this silent listening process, which lasts only a few minutes, the device takes an electrical photograph of the heart from different angles.

Each of the waves shown in this photograph has a medical meaning. In a healthy heart, a small wave appears first; this wave indicates that the upper chambers of the heart have been electrically stimulated and contracted to push blood downward. The much larger and sharper peak consisting of lines that follows immediately afterward represents the main contraction moment of the heart. In other words, it symbolizes the moment when the lower chambers contract with full force and pump blood throughout the body. The broader wave that follows is the phase in which the heart begins to rest and electrically recharge for the next beat. The distance between all these waves, their proportions relative to one another, and their shapes largely reveal whether something inside is functioning properly.

When Should You Have an ECG Without Delay Based on the Symptoms You Experience?

The cardiovascular system often reveals the difficulties it experiences internally by reflecting them in different parts of the body. Sometimes these signals are very clear and severe, while at other times they may appear in much milder and misleading forms. Conditions that begin in the center of the chest, behind the bone commonly known as the breastbone, and create a feeling of pressure, tightness, burning, or a heavy weight sitting on the chest are among the symptoms that require the greatest attention. This feeling generally does not remain only in the chest; it may spread to the left arm, shoulders, neck, back, and even the jaw. At such moments, reaching a healthcare institution quickly and having the electrical map of the heart recorded is of great importance.

Chest pain is not the only important warning sign indicating that the heart is under strain. These important warning signals given by our body are as follows:

• Palpitations
• Fainting
• Weakness
• Sweating

Severe shortness of breath that begins suddenly and creates the feeling that the person cannot get enough air no matter how much they breathe should be taken just as seriously as chest pain. Moments when you feel your heart suddenly beating very fast, very slowly, or completely irregularly, as if a bird were fluttering inside your chest, indicate that there is a malfunction in the internal electrical network, even if temporary. Likewise, sudden darkening of vision, dizziness, or collapsing with a brief loss of consciousness for no apparent reason may indicate that the brain is not receiving enough blood and that the source of the problem is most likely a rhythm disorder in the heart. All these complaints can be clarified with an electrocardiogram that can be recorded within seconds.

Which Methods Are Used If a Heart Attack Is Suspected on the ECG Result?

Cholesterol plaques that accumulate over the years on the inner walls of the tube-like system called the coronary arteries, which supply the heart, may suddenly crack or rupture. The body immediately forms a blood clot at the rupture site, and this clot may completely block the already narrowed vessel within seconds. When the vessel becomes blocked, the heart muscle in that area is deprived of oxygen. Oxygen deprivation causes the cells to lose their normal electrical conduction properties within seconds. At that moment, the ECG goes into a state resembling a red alert. Certain lines that should normally progress very smoothly become arched upward or, on the contrary, collapse downward. The direction of the waves changes and they become pointed. It is largely possible to understand not only which vessel of the heart is blocked but also how large an area is affected by the damage from the deviations seen on this graph.

When such a picture is detected, a race against time begins to protect the heart muscle. The aim is to mechanically open the blocked vessel. Entry is usually made through a very small needle hole in the artery at the wrist or groin. Thin, flexible tubes are advanced to the heart, and a special contrast substance is administered to map the vessels. Once the blockage point is clearly visualized, a very thin wire is passed through the clot. A tiny balloon advanced over this wire is inflated at the blockage site, compressing the clot and plaque against the vessel wall. However, when the balloon is deflated, the likelihood of the vessel closing again is quite high. To prevent this, a small spiral-shaped metal mesh is placed inside the vessel together with the balloon. This structure, called a stent, supports the vessel in remaining open. The stents used today generally release special medications slowly into the vessel wall, significantly reducing the risk of renewed cell accumulation and blockage in that area. As soon as the vessel is opened, the chest pain gradually decreases, and the alarming elevated waves on the ECG usually begin to return toward normal levels.

Which Different Tests Are Used When an ECG Recorded at Rest Is Insufficient?

Many heart diseases have an insidious nature. While a person is lying down and resting, the heart muscle does not require a large amount of oxygen or blood. Therefore, even if there is significant narrowing in the vessels supplying the heart, the heart may manage at rest with the small amount of blood passing through the narrowed area. As a result, an ECG recorded while resting in the emergency department or outpatient clinic may appear completely normal. However, when the same person walks uphill, climbs stairs, or exerts effort after a heavy meal, the heart needs to accelerate, and the narrowed vessel can no longer meet the increased blood demand. At that moment, chest pain or shortness of breath is triggered.

Certain dynamic methods are used to reveal these hidden narrowings in a laboratory environment. The different test devices used are as follows:

• Exercise test
• Holter
• Recorders

The exercise test is based on the principle of placing controlled strain on the heart by having the patient move on a treadmill or stationary bicycle. While the patient walks, the speed and incline are gradually increased, and the electrodes attached to the chest continuously record during this time. If the lines that are normal at rest begin to shift downward as the person becomes tired, it is considered that the heart muscle is under strain and that there may be a narrowing somewhere restricting blood flow. On the other hand, if the complaints occur not with exertion but at uncertain times during the day, longer-term recordings are needed to capture the moment. A Holter monitor, which is a small portable device, is attached to the patient’s waist, and electrodes are placed on the chest. While the patient continues daily life, work, sleeping, and eating, the device records every heartbeat in its memory for 24 hours or longer. These recordings are later uploaded to a computer, and the periods corresponding to the times when the patient reported symptoms are examined in detail for electrical irregularities. In this way, temporary rhythm disorders or hidden cardiac events that cannot be detected in the hospital environment are revealed.

How Are the Valves Treated After ECG Findings Show Enlargement of the Heart Walls?

The heart is a continuously working mass of muscle. Just as the muscles of an athlete who lifts weights become thicker, when the heart encounters an obstacle, it must contract more strongly to overcome that difficulty, and its walls thicken over time. For example, long-standing high blood pressure or calcification and narrowing of the aortic valve, which is the main exit gate through which the heart sends oxygenated blood to the body, greatly increases the workload of the left chamber of the heart. As the heart muscle thickens, the strength of the electrical current it produces also increases. On the recorded ECG paper, seeing sharp and deep waves that rise far above normal limits and do not fit on the paper is one of the most concrete electrical reflections of this internal enlargement. Because the electrical conduction of the thickened muscle tissue is also impaired, characteristic deviations occur in the downward and upward directions of the waves.

Calcification of the aortic valve due to age or different diseases and the inability of its leaflets to open is a serious condition that causes the patient to experience shortness of breath, become tired easily, and even faint suddenly when insufficient blood reaches the brain. When this valve cannot perform its function, it must be replaced to eliminate the mechanical obstruction. It is now possible to replace the valve without opening the rib cage or stopping the heart in older patients with additional diseases or those considered to be at high risk for open chest surgery. In this method, called TAVI, access is generally obtained through the artery in the patient’s groin. A biological heart valve made from bovine or porcine tissue and compressed at the tip of a thin tube is advanced to the heart. When it reaches the exact level of the old calcified valve, the new valve is placed inside the old valve by expanding with the help of a balloon or by self-expansion and immediately begins to function. In this way, the passageway opens and the obstruction in front of the heart is removed. Patients can usually recover and stand within a few days after this procedure, which is often performed only under local anesthesia. The signs of severe strain on the ECG also tend to progress in a more favorable direction over time as the heart is relieved.

How Is the Risk of Stroke Reduced After Rhythm Disorders That Cause Palpitations Are Detected by ECG?

One of the rhythm disorders most commonly encountered clinically and frequently seen in the community is the condition called Atrial Fibrillation. When you look at the ECG graph, the regular waves that follow one another in harmony are replaced by a completely irregular, chaotic picture in which the distances constantly change and fine vibrations are seen along the baseline. Instead of contracting regularly and emptying blood downward, the upper chambers of the heart only tremble rapidly in place. This condition not only causes the patient to experience palpitations, fatigue, and restlessness but also leads to stagnation of the blood inside. When blood remains motionless in one place, it naturally tends to clot. The place where these clots most commonly remain hidden and grow is a small blind pouch resembling a fingertip located along the edge of the upper chamber of the heart. If a clot formed here breaks loose and enters the bloodstream, it may directly block the vessels leading to the brain and result in stroke.

In patients diagnosed with atrial fibrillation, the aim is to use special medications that reduce the blood’s ability to clot in order to prevent this danger. However, for some patients, using these medications may cause more harm than benefit. The patient groups in whom the use of blood-thinning tablets to prevent stroke may be unsuitable are as follows:

• Bleeding
• Organ failure
• Injuries
• Allergies

In patients with such a very high risk of bleeding, an interventional closure procedure is performed to minimize the possibility of stroke without medication. With the help of a catheter advanced to the heart through the vein in the groin, the opening of the clot-producing blind pouch inside the heart is reached. The pouch is measured precisely using various three-dimensional imaging methods. Special closure devices designed in the shape of an umbrella or plug are then positioned directly at the opening of this pouch. Once the device is placed there, the connection between the blind space and the heart’s main blood circulation is cut off. Blood can no longer enter that space, and the likelihood of clot formation there is largely eliminated. Within months, the body covers the device with its own natural heart-lining cells, transforming the area into a smooth wall. In this way, the patient is relieved from the constant fear of bleeding and the burden of lifelong blood-thinner use, while the risk of a clot traveling to the brain is reduced to a medically satisfactory level.

What Are the Permanent Treatments for ECG-Recorded Palpitation Episodes When Medications Are Insufficient?

Most people may notice their heart beating rapidly at some point in their lives, but in some cases these accelerations are far beyond normal. Sometimes very severe palpitation attacks begin suddenly, during which the heart starts beating 150 to 200 times per minute and the patient says, “It feels as though my heart is going to jump out of my chest.” When an ECG is recorded, it may be determined that these episodes originate not from the heart’s main electrical center but from another focus or an additional congenital electrical pathway. Normally, there should be a single cable carrying electricity from the upper chamber of the heart to the lower chamber, but in these patients there is an extra short-circuit pathway, and electricity continuously circulates within this pathway, causing the heart to work at unnecessarily high speeds.

Instead of trying to slow the heart with continuous medication use, advanced procedures called Electrophysiological Study (EPS) and ablation are used to identify and eliminate these faulty electrical pathways. This procedure is performed in special laboratories equipped with X-ray devices. Flexible electrode wires of millimetric thickness are advanced into the heart through the vessels in the groin. Through these wires, an electrical map of the inner surface of the heart is created. With the help of externally connected computers, small impulses are sent to the heart, and the palpitation episodes are triggered in a controlled manner in the laboratory environment. At the moment the palpitations begin, the location of the unnecessary or additional conduction pathway is identified centimeter by centimeter. Once the problematic region is detected, the tip of the catheter is heated, and that tissue is destroyed in a tiny spot using radiofrequency energy. Sometimes the same procedure is performed based on the principle of freezing the tissue. When the faulty pathway is burned or frozen, the short circuit disappears and the electrical current returns to normal. Thanks to this procedure, the vast majority of patients are freed from the fear of palpitations they have experienced for years and from the medications they have used, allowing them to begin a more comfortable life.

How Are the Dangers Seen on the ECG When the Heart Rate Drops Excessively Controlled with a Pacemaker?

Just as the heart may cause problems by beating too quickly, it may also become life-threatening by slowing excessively or stopping completely. The main switch that determines the heart’s natural rhythm may age over time, or a complete break may occur in the main cable between the upper and lower chambers. On the ECG graph, this condition may appear as long flat lines in which no electrical signals are generated or as block patterns in which the upper and lower chambers contract independently from one another at a very slow rate. When the heart rate falls to the 30s or 40s per minute, the amount of blood reaching the organs, especially the brain, decreases significantly. The patient begins to experience chronic fatigue, reduced exercise capacity, dizziness, sudden darkening of vision, and fainting episodes.

In cases where the heart rate remains permanently very low and this condition cannot be corrected with medications, supportive external power is needed, and permanent pacemakers are used for this purpose. For this procedure, the area immediately below the collarbone in the chest is numbed locally, and a small, flat metal box-shaped battery is placed just beneath the skin. Thin, durable, flexible wires extending from this battery are advanced through the vein in the area to the relevant chambers of the heart and gently attached to the heart tissue. The pacemaker functions like a constantly alert guard. When the heart is beating at an adequate rate on its own, the device does not intervene and only monitors. However, when the dangerous pauses seen on the ECG tracing occur or the heart rate drops below the previously adjusted lower limit, such as 60 beats per minute, the device detects this within fractions of a second. It sends very weak electrical currents that the person cannot feel, allowing the heart to continue functioning normally. In some patients with severely impaired heart function, in addition to devices that correct slow heart rates, much more advanced implantable shock devices are placed that can detect sudden life-threatening rapid rhythms and deliver an internal shock, providing substantial protection.

What Are the Effects of Congenital Heart Defects on the ECG and How Are They Closed Through the Groin?

While the human heart develops in the womb, it initially exists as a single cavity and gradually divides in the middle by a wall into right and left chambers. If the wall does not close during this separation process, the baby is born with a hole in the heart. This hole may be located between the atria or between the ventricles. Because the pressure on the left side is much higher, some of the oxygenated blood passes through this hole with every beat and flows into the right side. Over the years, this additional blood volume entering the right side causes stretching and enlargement of the right heart walls and increased pressure in the pulmonary vessels. Because this mechanical stretching in the right heart also stretches and lengthens the electrical conduction pathways, it produces very clear reflections on the ECG. Conduction is delayed, and a right bundle branch block, known as a rabbit-ear appearance on the graph, develops. Because the enlargement axis of the heart changes, characteristic deviations are observed in the normal directions of the ECG waves.

If the burden created by these holes on the body is very high or if they begin to pose a danger when the patient reaches an advanced age, they must be closed. In the past, open heart surgery was always required for this, and the heart was reached by cutting through the rib cage. Today, much more comfortable options are available for holes with suitable dimensions and sufficient surrounding margins. The inside of the heart is reached through the vein in the groin using very thin and soft tubes. Devices made from a metal alloy called nitinol, selected according to the diameter of the hole, are carried inside these tubes. This device has a flexible structure with shape memory. When pushed through the catheter toward the hole, it opens like a disk on each side and compresses the hole from the middle. After confirming with the help of an ultrasound device monitoring the heart from the esophagus that the device is properly positioned and blood flow has stopped, the device is left in place and the tubes are withdrawn. The absence of a surgical incision, lack of pain, and the ability of the patient to return to normal life within a very short time are among the most important advantages of this method. While the device remains in the body, it integrates with the tissue and largely helps resolve the defect permanently. However, there is a very important detail here: if the patient has presented too late and the pulmonary vascular pressure has become irreversibly impaired, closing the hole may place even greater strain on the heart rather than provide benefit, and therefore the procedure is not performed.

Frequently Asked Questions

Prof. Dr. Kadriye Kılıçkesmez

Prof. Dr. Kadriye Orta Kılıçkesmez is one of the leading figures in the field of Turkish cardiology. She was born on January 24, 1974, in Tekirdağ. After completing her undergraduate education at Istanbul University Cerrahpaşa Faculty of Medicine, she chose cardiology as her specialty and received her specialist training at the Cardiology Institute of the same university. In 2015, she was appointed by the university to establish the Şişli Etfal cardiology clinic and Angio laboratory. Becoming a professor in 2017, Kadriye Kılıçkesmez established the cardiology clinic and Angio laboratory of Prof. Dr. Cemil Taşçı Hospital in 2020 and ensured that the clinic became a training clinic.