What is an Abnormal ECG?

An ECG measures the time and electrical activity of the heart. A normal ECG has a regular rhythm and patterns compared to an abnormal one. The abnormal ECG warns us of heart health. We need to know what makes an ECG abnormal as it helps us to diagnose and manage cardiovascular conditions.

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Abnormal ECG patterns are visible as irregular

• heart rhythms.

• an abnormal waveform.

• unusual intervals.

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These changes indicate heart disease, electrolyte imbalance, or the effects of medicines. These patterns help us identify abnormalities in the heart. Their identification is essential for timely intervention and treatment. We need to know what makes an ECG abnormal as it helps us to diagnose and manage cardiovascular conditions.

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Abnormal ECG patterns are visible as irregular

• heart rhythms.

• an abnormal waveform.

• unusual intervals.

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These changes indicate heart disease, electrolyte imbalance, or the effects of medicines. These patterns help us identify abnormalities in the heart. Their identification is essential for timely intervention and treatment. The significance of abnormal ECG extends beyond diagnosis. It is a tool in preventive healthcare.

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Detecting changes in the heart soon helps healthcare providers suggest lifestyle changes or medical interventions to improve patient outcomes and promote cardiovascular health. Understanding abnormal ECG empowers patients to participate in their health journey, offering hope and optimism for a healthy future through lifestyle changes.

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When is an ECG Required?

If someone experiences any of the following symptoms, an ECG may be required.

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• Chest pain or discomfort.

• Difficulty in breathing.

• Palpitations or feeling your heart is beating oddly.

• Racing heart.

• Fainting feeling.

• Sudden weakness.

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What is a Normal ECG?

Features of normal ECG

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1. Heart Rate: Normal heart rate is between 60-100 beats per minute.

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2. Rhythm: Sinus rhythm is the normal rhythm.

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3. Waveform: A normal waveform includes.

• P wave: It is formed as a result of atrial contraction.

• QRS complex: It is formed due to the ventricle contraction.

• T wave: It forms due to the ventricles returning to normal resting state.

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4. Intervals: It is the time interval between two waves.

• PR Interval: The time taken by the electrical signal to travel from the atria to the ventricles (120 and 200 milliseconds).

• QT interval: The time taken by the ventricles to contract and relax.

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What Makes ECG Abnormal?

An abnormal ECG indicates deviations from the standard heart pattern, signaling potential health concerns. P waves, QRS complexes, and T waves help healthcare professionals identify irregularities that suggest abnormalities in heart function. Recognizing these abnormalities allows for timely diagnosis and intervention.

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• ST segment: changes indicate a heart attack.

• Prolonged QT interval leads to arrhythmias.

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Understanding what constitutes an abnormal ECG helps healthcare providers and patients. To manage heart health and detect conditions that could have consequences. It underscores the responsibility and commitment of healthcare professionals to their patients well being‍.

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Causes of Abnormal ECG

Abnormal heart rhythms and abnormal ECG results suggest heart-related conditions like.

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• Coronary artery disease. Narrow blood vessels reduce the supply of blood to the heart.

• Congestive heart failure. The heart is unable to pump sufficient blood.

• Myocardial infarction. When the obstructed blood flow damages the heart tissue.

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Non-heart-related causes that affect ECG are:

• Electrolyte abnormalities. Abnormal potassium, calcium, and magnesium electrolyte levels impact the heart's electrical activity.

• Effect of medications. Drugs like beta blockers and calcium channel blockers cause changes in the ECG.

• Stress. Emotional and physical stress affects heart rate and rhythm.

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Identifying Abnormal ECG

An ECG indicates s heart diseases are:

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• Irregular heart rhythms.

• Abnormal waveform.

• ST segment changes.

• Prolonged QT intervals.

• Wide QRS complexes.

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Each deviation suggests an underlying condition.

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Irregular heart rhythms 

When the heart beats too fast, too slow, or in an irregular pattern, it is classified as an irregular heart rhythm. Atrial fibrillation, ventricular tachycardia, and bradycardia are common conditions associated with rhythm disturbances. These irregularities disrupt normal blood flow, leading to symptoms such as:

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• Palpitations.

• Dizziness.

• Fainting.

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These conditions require evaluation and treatment.

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Abnormal wave patterns

Abnormalities in waveforms that are common are in.

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• P wave: Changes in the P wave (absent) suggest abnormal conduction in conditions like atrial enlargement.

• QRS complex: Changes indicate conditions like ventricular hypertrophy or myocardial infarction.

• T wave inversions or elevations: Changes in T wave signify ischemia, electrolyte imbalances, or other cardiac conditions.

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ST segment changes

Recognizing changes in the ST segment is essential for timely diagnosis and intervention as they affect the lives of the patients.

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• ST elevation indicates acute myocardial infarction (heart attack) or pericarditis.

• ST depression is a sign of ischemia. It can occur during exercise or stress testing.

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Prolonged Intervals

Factors causing prolonged intervals are electrolyte imbalances, medications, or underlying heart conditions. Identifying the prolonged intervals is necessary for early intervention and effective management of life-threatening heart rhythms. A prolonged QT interval on an ECG can increase the risk of dangerous arrhythmias arising from medications and electrolyte imbalances.

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Wide QRS complexes

In conditions such as bundle branch block and hypertrophy of ventricles, ventricles contract late due to a delay in the transmission of electric impulses. It causes a wide QRS complex on the ECG and causes the heart to function inefficiently.

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Types of Abnormalities

They are classified into

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Conduction

The pattern of conduction is

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SA Node      to    AV Node       to       Bundle of His     to   Bundle branches

Conduction abnormalities are best visible in P waves in lead II and V1.

PR Interval is the time taken for depolarization to spread from the SA node to the ventricular muscles. It should not be greater than 0.2 seconds or one big square.

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First-degree heart block

If the PR interval is greater than 0.2 seconds, it is a first-degree AV node block. All waves are present, but a large gap or pause is visible between the P wave and the QRS complex.

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It can be a sign of

• Coronary artery disease.

• Acute rheumatic carditis.

• Digoxin toxicity.

• Electrolyte disturbance.

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Second-degree heart block

There is intermittent absence of the QRS complex. Indicating a blockage between a V node and the ventricles. There are three types.

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Mobitz type 2 phenomena

• Regular rhythm.

• Fairly constant PR interval.

• Occasional absence of QRS complex for every two or 3P waves.

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Wenckebach Phenomena (Mobitz type1)

• Shows progressive lengthening of PR interval followed by an absence of QRS complex.

• A short PR interval and normal QRS. And then the cycle begins.

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The cycle is variable in length, and the RR interval shortens with the lengthening of the PR interval.

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2:1 and 3:1 conduction

A normal cycle, then one cycle with an absent QRS. (2:1)

Or

There is one normal cycle, then 2 cycles without a QRS. (3:1)

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Causes are

• Acute MI.

• Chronic heart disease.

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3rd degree block or complete heart block

• It occurs when no beats are conducted to the ventricles and the atria contract normally.

• Ventricles are excited by their ectopic pacemaker.

• P waves more than QRS complexes.

• QRS complexes are less.

• Variable PR intervals.

• P wave and QRS complexes are present, but no relationship between them.

• Abnormal-shaped QRS complexes due to abnormal spread of conduction throughout the ventricles.

• QRS is broad (160 milliseconds when the normal is 120ms.

• Right axis deviation.

• Escape rhythms present.

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Causes

• MI.

• Due to fibrosis around the bundle of His or both bundle branches blocked.

• Indicates underlying fibrosis always.

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If the number of atrial and ventricular complexes is equal, then it is called AV dissociation and not AV block.

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Bundle branch block

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In a normal heart

The wave of depolarization reaches the intraventricular septum, causing.

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• Normal PR interval.

• Lengthened QRS duration >120 milliseconds.

• The septum depolarizes from right to left.

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Right bundle branch block

In the right bundle branch block, the right bundle branch is blocked, so 

The right ventricle and left ventricles do not polarize at the same time.

Left ventricular depolarization is normal. Producing normal R and normal S wave.

Right ventricle depolarises, causing a second R (R1)wave, creating a distinct pattern, which we see as

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• In V1: Creates M-shaped QRS As R wave is positive, South is negative. An R1 is also positive. It is also known as the RSR pattern.

• In V6: a W-shaped QRS is formed because the R wave is negative. S wave is positive, and R1 is negative.

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QRS complexes are wide > 120 ms.

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Left bundle branch block

Indicates Left-sided heart disease. QRS pattern and physiology of the left bundle branch block is opposite of the right bundle branch block.

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Causes

• If the patient has recent chest pain. The left bundle branch block indicates MI.

• Aortic stenosis.

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Rhythm Abnormalities

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Rhythms originate in

• SA node.

• AV node.

• Ventricular muscles.

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Sinus rhythm

• The originates at the SA node.

• Has a P wave preceding the QRS wave.

• Constant PR interval.

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Sinus tachycardia

• Has an increased heart rate. It is associated with anxiety, fear, exercise, pain, hemorrhage, and thyrotoxicosis.

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Sinus bradycardia

• Has a slow heart rate.

• It occurs while sleeping, in athletic training, myxoedema

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Supraventricular rhythm

• The rhythm originates outside the ventricles, spreading normally to the ventricles.

• The route is from the bundle of His to the left and right bundle branches.

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It forms

• Normal QRS complexes, as the part forming them, are not in the ventricles.

• The QRS formed is wide if a right or left bundle branch block is present.

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Ventricular rhythm-The bradycardias

The spread of the charge is abnormal, causing wide QRS complexes.

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Atrial escape

• It is a supraventricular rhythm.

• It is caused.

• When normal depolarization of the SA node has not occurred, a part of the atrium begins to depolarize.

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On the ECG, atrial escape is visible as

• Abnormal P wave as the excitation begins away from the SA node.

• Normal QRS.

• Normal beats after abnormal ones.

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Junctional Escape

• No P waves.

• Normal QRS.

• Heart rate less than 75 beats per minute.

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Ventricular escape

Commonly seen in complete heart blocks and may even be a one-time event.No waves appear before the escape beat.

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• SA node failing to fire.

• The junctional escape mechanism does not take over.

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It is not due to a bundle block. Ventricular escape beats often return to a normal rhythm afterward

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Extrasystoles

They appear like the corresponding escape beats and occur earlier than expected.

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Junctional Extra Systole

It has an absent or misplaced P Wave. Because the depolarization travels towards the atria upwards and the ventricles downwards. It has a normal QRS, as ventricular conduction is unaffected.

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Atrial extrasystole

• Normal QRS as ventricles depolarise normally.

• Normal looking beat. Except that it occurs early.

• P wave may show some differences as the impulse arises from ectopic focus. PACs are usually harmless.

Supraventricular tachycardia

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Atrial tachycardia

• Atrial depolarization is more than 150 beats per minute.

• P waves are superimposed on T waves of the preceding beat.

• QRS complexes are normal.

• The atrioventricular node cannot conduct faster than 200 beats per minute. If a fast rate occurs, it causes an atrioventricular block with P waves not followed by QRS complexes.

• Atrial tachycardia has a fast rhythm.

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Atrial flutter

• Rate >250 bpm.

• Sawtooth P waves.

• AV block is common since the AV node cannot pass greater than 125bpm.

• If the atrial rate is 250bpm, then the ventricular rate is 125 in a 2:1 block.

• P waves look like T waves and appear at regular intervals. 

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Junctional Tachycardia

• The area around the AV node causes depolarisation.

• P waves are absent or close to the QRS complex.

• QRS is normal as ventricles activate normally.

• Are due to small re-entry circuits around the AV node and are known as atrioventricular nodal re-entry tachycardia.

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Ventricular Tachycardia

• Occurs when a focus in the ventricles discharges at high frequency, causing wide and irregular QRS complexes.

• T waves not found.

• No P waves. 

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Fibrillation

Occurs when muscles contract on their own.

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Atrial Fibrillation

• No P waves, only an irregular baseline.

• Irregular QRS (75-190 bpm) with standard shape.

• Standard T waves.

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Ventricular fibrillation

• No QRS, P, or T waves.

• Unconscious patient.

• Is life-threatening.

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Wolff Parkinson-White syndrome (WPW syndrome)

Impulses travel from the atria to the ventricles through the AV bundle in the heart. Sometimes, accessory pathways for conduction are on the left side of the heart. Impulses travel through this accessory pathway and are not delayed by the AV node. There is pre-excitation of the ventricles.

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• The accessory pathways called the Bundle of Kent.

• The incidence of WPW syndrome is between one to 3% of the general population.

• Most patients are asymptomatic. But sudden death can occur in 0.6% of those with WBW.

• Sudden death can occur when there is paroxysmal tachycardia (when tachycardia is intermittent, it is called paroxysmal). The signal from the atria travels down through the accessory pathway and to the bundle of his and back into the Atria. A loop of depolarization forms and is called a re-entry circuit.

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 Findings in an asymptomatic individual

• Sinus rhythm.

• Right axis deviation.

• Short PR interval.

• Short QRS complex.

• Delta wave- A short upstroke just before QRS.

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Findings during re-entry tachycardia.

• No P waves.

• Tachycardia.

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Pacemaker

Characteristics of a wave with an artificial pacemaker.

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• Occasional P waves not related to QRS.

• The pacemaker's stimulus is seen as a spike before the QRS complex.

• Broad QRS complexes. As the pacemaker stimulates the right ventricle.

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Ectopic beats

An unexpected event that occurs out of sequence is ectopic. Atrial and ventricular ectopics occur when P waves and QRS complexes do not work synchronously with the rest of the heart. Usually these are single events occurring every few seconds or are occasional.

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Atrial ectopics

• Commonly called premature atrial complex, PAC.

• An abnormal P wave precedes a normal QRS. Sometimes, the P wave is not visible and is hidden in the preceding T wave.

• Pulse is irregularly irregular.

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Ventricular ectopics

• They show an abnormally widened QRS complex.

• Pulse is irregularly irregular.

• Usually asymptomatic and do not require treatment.

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After an abnormal ECG

An abnormal ECG does not always mean that there is underlying heart disease. You may be required to undergo a few more tests, such as.

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• Echocardiogram. Ultrasounds take pictures of the heart to assess cardiac structures, internal cardiac walls, and muscles for abnormality.

• Holter Monitor. It is a 24-hour patient-worn device that records the long-term electrical activity of the heart. Usually, it is useful in diagnosing intermittent arrhythmias.

• Stress test. It is a dynamic test where a person exercises and the capacity of his heart to cope with exertion is tested.

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Treatment for an Abnormal ECG

Treatment for an abnormal ECG depends on the underlying cause. 

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• Changes caused by normal body functions, stress, or exercise require no intervention.

• If ECG changes result from medications, adjusting the therapy can be effective.

• Treating electrolyte imbalances due to dehydration may necessitate fluid replacement.

• Irregular heartbeats (arrhythmias) might not always require treatment, but if they lead to specific symptoms, medications or a pacemaker may be necessary.

• A heart attack is an emergency that requires angioplasty to open blocked arteries and minimize damage to the heart.

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Conclusion

An abnormal ECG can mean many things- some may be insignificant, while others may indicate an abnormal heart function. Timely interpretation and diagnosis are essential for managing and treating these heart problems. Gauze and their AI-powered solutions help us understand abnormal ECG results and improve the outcome for the patient.