How to Read a Heart Monitor

An electrocardiogram, ECG or EKG is a display method for the electrical activities of the heart. While reading a cardiogram is usually done by cardiologists, their assistants and nurses, you can also benefit by getting to know what the various ECG graphs and figures stand for. However, remember that this does not make you a cardiologist. You will still need to consult the professionals for proper interpretation and diagnosis of your heart’s rhythms.

How to Read a Heart Monitor

Understanding and interpreting an electrocardiogram can only be properly done by trained personnel. Moreover, an ECG is not used to make a diagnosis of a heart condition on its own. Physical examination and a patient’s medical history as well as patient interview are the important basis for diagnosis of heart ailments.

Learn the Basics

Step 1

A heart monitor usually has 12 leads which pick up electrical impulses originating from the heart and transfers them to the monitor. To read the ECG, you start by picking the leads. The waveforms of the different leads are different as they relate to different perspectives of the heart. Leads number V1 to V4 have a frontal perspective; leads coded V5, V6 and aVL have a side perspective and leads coded II, III, aVF have a back and lower perspective of the heart. 

Step 2

Observe the grid in the monitor. The horizontal lines represent time, with each of the little boxes 0.04 second, while each larger box represents 0.2 second and every five larger boxes represents one second.

The vertical lines show the voltage; one small box is 0.1mV. For most heart monitors, two larger boxes representing 1.0mV are marked with a darker line. 

Step 3

Now that you have learnt the basics of how to read a heart monitor, try to locate and mark the P-wave, usually most outstanding on lead I. P-waves are normally small bumps that appear before the rest of the complex of waves and figures. It may be shallow, appear several times in a row or be hard to detect due to the heart’s rhythm. 

Step 4

Locate and mark the main wave form (QRS complex). Q-wave is rare and when present, usually dips below the baseline at the start of the main waves complex. These are followed by the R-wave which is normally tall and spiky. The S-wave is next. It normally dips below the baseline in a long and sharp spike. 

Step 5

Next, look for and mark the T-wave. This is normally a small bump following the main wave complex. In some patients, the T-wave is hard to locate as it may be flat, inverted or easily confused with P-wave.

Interpret the Results

Step 1

Normal intervals between a P-wave and an R-wave ranges between 0.12 and 2.0 seconds. A longer interval could be the sign of conduction abnormalities, while the appearance of several P-waves or seemingly fluttering P-waves might signify arterial fibrillation or similar conditions.

Step 2

Locate any Q-wave formations. Their presence is an indication of heart damage or a past heart attack. Ventricles’ discharge and contraction are represented within QRS complex. You can determine the heart rate by counting the big boxes from one R-wave to the next and dividing 300 by this number.

Counting the R-waves in a 6-second strip and multiplying this number by 10 can help determine the presence of irregular heartbeats. Results higher than 100 bpm indicate tachycardia, while those below 60 bpm indicate bradycardia. When QRS wave complexes appear close together and P-waves are missing, the life-threatening ventricular fibrillation is indicated.

Step 3

ST segment lies between S-wave and T-wave. Elevations here are indicative of a heart attack or myocardial infarction.

What Does an Abnormal EKG Indicate?

An electrocardiogram measures many aspects of the heart’s activities as you would find out by learning how to read a heart monitor. For this reason, an abnormal ECG’s result can signify many things which include:

  • Abnormalities or defects in the shape and size of the heart –such as some aspects of the heart walls being larger than others. This may mean that the heart could be working much harder than normal when pumping blood.
  • Incidence of electrolyte imbalances. Because electrolytes are the means by which electricity is conducted in the body, imbalances of calcium, potassium and magnesium electrolytes will result in an abnormal ECG reading.
  • Ischemia or heart attack. In the event of a heart attack, blood flow is disrupted so that some heart tissues don’t get sufficient oxygen and may therefore die. The affected tissues are unable to conduct electricity effectively, which leads to abnormal ECG. Similar results occur in case of lack of blood flow or ischemia.
  • Abnormal heart rate. The normal heart ranges from 60 to 100 bpm. When the EKG shows a rate outside this range, it indicates a heart rate that is either too high or too low.
  • Abnormal heart rhythms. A normal heart beats in a fairly steady rhythm. A case of an abnormal rhythm may be indicated on an EKG.
  • Side effects of medication. Some medications, including those used to correct some heart conditions, affect the rhythm of the heart and the heart rate, causing arrhythmias. Such medications include calcium channel blockers, sodium channel blockers and beta blockers.

How Is an Abnormal EKG Treated?

Treatment following an abnormal EKG depends on the cause of the abnormality.

  • In the case of a person with very slow heartbeat due to poor electricity conduction in the heart, a pacemaker may be required to correct the heart rate and rhythm. In other cases, medications may be required to achieve and maintain a normal heart rhythm.
  • In the case of a patient who is having a heart attack, surgery or cardiac catheterization may be needed to restore blood flow to and through the heart.
  • When an abnormal EKG is a result of electrolyte imbalance, medication or fluids may be used to restore electrolyte balance.
  • In some cases, the doctor will not recommend any form of treatment even when the EKG is abnormal. This happens when a patient is not experiencing any symptoms and in case the abnormal reading is not significant enough for remedial action. Learning how to read a heart monitor can help you understand this.