Cardiac Monitoring EKG Interpretation

Cardiac Monitoring
&
Einthoven's Triangle

Thomas E. O'Brien
AS CCT CRAT RMA CCMA

Part 1

Cardiac monitoring is commonly performed in many areas in critical care. Applying a cardiac monitor is a simple task, but the circumstances may be very different from prehospital to the emergency department to surgery, including pre and post-operatively and the myriad of intensive care units and telemetry.

Part 2

The important thing to remember is that the patient has a monitor applied for a specific reason. Remain diligent in your observation and report any changes noted during "monitoring".

A cardiac monitor is a tool to be used to assist with assessment of the patient. Remember to always treat the patient and not the "monitor".

Part 3

An unresponsive patient with what appears to be Normal Sinus Rhythm may in fact be clinically dead. They may have something called "Pulseless Electrical Activity".

Pay strict attention to your patient's vital signs and level of consciousness during monitoring.

Part 4 (Cont)

Treat the patient, not the monitor.

Loose, or dried out sensors (electrodes) or broken cables may cause a tracing to appear much the same as one of these life-threatening dysrhythmias.

Part 5

What appears to be Ventricular Tachycardia might occur because the patient is brushing their teeth. This is referred to as "toothbrush tachycardia".

This is caused by the repetitive body movement when brushing your teeth.
This is not an actual cardiac event.
Remember if you have an unresponsive patient, call a "code blue" (follow your facility's protocol) and begin emergency procedures.

Part 6

A variety of manufacturers offer a wide variety of cardiac monitors. A majority will have three or five cables. We will focus on the most common type today, the three-cable device.

Triangle

The three sensors applied may be placed in a few different locations, but ultimately they form a "triangle" around the heart.

This often referred to as Einthoven's Triangle.

Locations

One sensor is placed on either the right wrist, right deltoid or upper outer aspect of the chest, just inside the right shoulder.
The next sensor is placed on either the left wrist, left deltoid or upper outer aspect of the chest, just inside the left shoulder.
Finally, this last sensor is placed at either the inner left lower leg (just above the ankle) or at the left lateral costal margin of the ribs.

Introduction

Leads I, II, & III are referred to as "bipolar leads". This is due to having two sensors on the skin surface making the positive and negative pole for this particular view.

When monitoring patients in one of these views, the sensor not involved in the "lead circuit" will become the ground.

Which Leads?

Einthoven's Triangle is formed by which three leads?

Answer

Einthoven's Triangle is formed by which three leads?

Right Shoulder (arm)
Left Shoulder (arm)
Left Leg

Introduction

By use of three sensors, one each placed on the right arm, left arm and left leg, we are able to obtain six different views.

The first three views I will review are called Standard Leads I, II and III These views are referred to as "bipolar leads" due to two sensors utilized on the skin surface (one is positive and the other is negative – just like a battery) to complete the circuit.

The other three views are aVR, aVL and aVF. These will be discussed shortly.

One last comment, direct views of the heart will always be from the position of the positive pole i.e. Lead II and aVF positive pole is the left leg. These would be "inferior" views.