ECG Interpretation FAQs

An arrhythmia is simply an abnormality of the rhythm of the heart. More specifically, it is an abnormality of cardiac impulse formation or conduction. That means that the areas of the heart that produce impulse may not function correctly leading to heart rhythms being too fast, too slow, or even cease. Additionally, an arrhythmia may affect the conduction of the electrical impulse. This too may cause abnormal heartbeats or rhythms that are too fast, or too slow. Some arrhythmias are insignificant whereas other arrhythmias are very serious and life-threatening. People with arrhythmias may feel palpitations. Arrhythmias are diagnosed using electrocardiograms (ECG), heart monitors, or on home rhythm monitoring devices.

Reading electrocardiograms (ECG) is a skill learned by many medical providers. The electrical activity of the heart is generally printed on a special piece of graph paper. A typical ECG looks at this electrical activity from 12 different views. ECG interpreters learn to identify patterns of normal cardiac conduction as well as changes that are seen with abnormal conduction or cardiac disease. A skilled ECG reader can identify a heart attack, thickening of the heart muscle, abnormal heart rhythms, and many other cardiac conditions.

An electrocardiogram EKG is the most common cardiac test performed, It analyzes the electrical activity of the heart to detect abnormal heart rhythms and other cardiac abnormalities. An EKG may tell a medical provider that there is an arrhythmia that makes a patient prone to having a stroke. Additionally, the EKG may show a heart attack, thickening of heart muscle, inflammation of the lining around the heart, toxicity of certain medications, or anomalies of electrolytes in the blood, like too much or too little potassium. A skilled EKG reader can detect many other cardiac problems.

The heart, just like a house, has an electrical system and a plumbing system. The electrical system and “wiring” in the heart cause it to beat and circulate blood throughout the body. An ECG is a test looking at the electrical activity of the heart. A normal ECG shows the heart beating in the proper order and at the correct rate. This is identified by P-waves, which show the activity of the atria (upper chambers of the heart), QRS complexes, which demonstrate the activity of the ventricles (lower chambers of the heart), and the T-waves, which exhibit the resetting of the electrical system of the ventricles. There are established norms for the size and shapes of all of these ECG complexes as well as the cadence, rates and intervals between complexes and individual beats. A normal ECG illustrates a rhythm between 60 and 100 beats per minute.

An electrocardiogram (EKG) may detect a heart attack. `

Strictly speaking, the EKG of a patient with a myocardial infarction has a blip called a Q-wave. The age of the heart is determined by the ST and T waves. An acute heart attack (< 24 hours old) demonstrates ST and T-wave elevation. A recent heart attack (24-48 hours old) show some ST segment elevation and T-wave inversion. Age-undetermined heart attacks (48 hours to months-old) display baseline ST segments, but inverted or flat T-waves. Finally, an old myocardial infarction (months to years-old) exhibits Q-waves with normal ST and T waves. Heart attacks can also be divided into two groups – STEMI and non-STEMI. The first, ST segment Elevation Myocardial Infarction, presents with elevated ST segments on the EKG of a patient with cardiac-type chest pain. The second, non-ST segment Elevation Myocardial Infarction does not have these obvious ST segment changes and is recognized by identifying the patient’s symptoms and abnormal cardiac enzymes (blood tests)

Many things can cause an electrocardiogram (ECG) to appear abnormal. Some of these things may relate to the heart rhythm, and some may relate to other heart problems. It needs to be recognized, though, that an abnormal ECG may not be pathologic or problematic. For example, the ECG of a patient with bradycardia (slow heart rhythm) will be read out as abnormal, although this finding is also typical of a well-conditioned athlete. It is important that ECGs be interpreted by a qualified medical provider to decide the ECG’s significance.

A typical electrocardiogram (EKG) consists viewing the electrical activity of the heart from 12 different views. Rhythm strips are longer tracings of heart rhythm or pattern of beats. Reading a rhythm strip requires the interpreter to understand where in the heart the rhythms starts, and then how the impulse conducts throughout the rest of the heart tissue. Rhythm strip readers look at the different waveforms (e.g. P-waves, QRS complexes and T-waves), the intervals (e.g. PR interval, P-P interval, and R-R interval), the heart rate, as well as the cadence, and regularity of the beats.

Atrial fibrillation is an abnormal heart rhythm that can be detected on an ECG or rhythm strip. For simplicity, the ECG shows a squiggly horizontal baseline with intermittent, irregularly spaced vertical lines over this baseline. So, imagine if a person with a tremor, drew a horizontal line from left to right across a page – this is the baseline. Then imagine if another person scribbled vertical up-and-down lines perpendicular and intermittently on top of the line.

Calculating the heart rate on an electrocardiogram (ECG) is similar to how you might measure a patient’s pulse. Simply you count the number of beats in one minute. With a person, you might feel their pulse and count the number of beats in 60 seconds, or you may count the number of beats in 15 seconds and multiply this by 4, which then gives you the number of beats in 60 seconds. Determining the heart rate on an ECG is no different. The easiest way is to recognize that a typical ECG shows a 10-second tracing of the heart’s impulse. If you start at one side of the ECG and count up all of the similar-looking large complexes all the way over to the other side, and then multiply this number by 6 (which is the number of 10-second periods in a minute) then you get the heart rate in beats per minute.

The QRS complex of an electrocardiogram (ECG) represents depolarization of the ventricles (lower, pumping chambers of the heart). Depolarization is an electrical change within a cell causing a shift in the electrical charge. Depolarization of the ventricles then leads the muscle cells to contract, which in turn causes the ventricles to pump blood. The P-wave on an ECG comes before the QRS complex and represents depolarization of the atria (upper, receiving chambers of the heart). Depolarization of the atria, cause them to contract, which in turn pushes blood into the ventricles. The T-wave is a deflection on the ECG that follows the QRS complex. T-waves represent repolarization of the ventricles. Repolarization essentially means that the electrical changes that occurred during depolarization reset in preparation for the next cycle. The normal waveforms on an ECG are P, QRS, T, which repeat for each beat.

ACLS, which stands for advanced cardiac life support, is a set of guidelines designed to help medical providers respond in a medical emergency. Many medical providers obtain ACLS certification. These providers include but are not limited to, doctors, nurse practitioners, physician assistants, nurses, and emergency medical technicians (EMT) to name a few. ACLS requires the trainee to pass BLS (basic life support), do pre-class training, take an ACLS class, and pass the written and hands-on skills test.

For simplicity, sinus arrhythmia is a normal heart rhythm that originates from the normal pacemaker of the heart (SA node), beats at a normal heart rate of 60 -100 beats per minute, but is a little irregular in cadence. It is not pathologic and is considered a normal variant. It is seen most often in young, healthy people.

Nowadays, most electrocardiogram (ECG) machines are programmed with an automated interpretation program. They use pattern recognition to make ECG diagnoses. At the end of these diagnoses, this automated system concludes one of three things – Normal ECG, Borderline ECG, or Abnormal ECG. This system prompts providers to look for conditions, but often confuses and worries patients. For simplicity, the ECG is only called normal if every aspect is felt to be normal by the ECG machine. Any abnormalities, even ones that are benign and of no clinical consequences. Get labeled as Borderline or Abnormal. If you see Borderline or Abnormal on an ECG, do not panic and ask your medical provider.