How to recognize sinus bradycardia on a 3- or 4-lead EKG

Sinus bradycardia is a condition in which the electrical system of the heart initiates an electrical impulse that, in turn, causes the heart to beat abnormally slowly. Although this heart rhythm can be considered normal in patients taking certain medications, such as beta blockers, or in well-conditioned athletes, it can also lead to fatigue, sweaty or clammy skin temperature, syncope (passing out) or dizziness. Identifying sinus bradycardia on an EKG can help lead to a definitive cardiac diagnosis.

Things You'll Need

• EKG monitor with either three or four chest leads
• Electrodes
• EKG printout
• Measuring device, either calipers or a ruler

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Instructions

Assessing an EKG Recording for the Presence of Sinus Bradycardia

• 1

  Attach the patient to the EKG monitor using fresh electrodes. If the patient is sweating or feels clammy, dry the skin before attaching the electrodes to ensure proper adhesion.

• 2

  Look at the oscilloscope to confirm the patient is properly attached to the cardiac monitor.

• 3

  Record at least a six second (or 600 millisecond) EKG strip by pressing the record button on the EKG monitor.

• 4

  Assess the EKG for the presence of P- and R-waves.

• 5

  Measure the distance in milliseconds of the P- to R-wave Interval (PRI) using calipers or a ruler. This is obtained by measuring the length between the point the P-wave begins a positive deflection from the isoelectric line and where the R-wave begins a positive deflection from the isoelectric line.

• 6

  Compare the measurement to accepted standards classifying the length of the PRI as less than 0.20 millisecond.

• 7

  Assess the regularity of the R- to R-wave interval by using calipers or a ruler to measure the amount of milliseconds between each R-wave peak. R- to R-wave peaks can be variable but should be a consistent number of milliseconds from peak to peak.

• 8

  Measure the width of the QRS complex with either calipers or a ruler. Obtain this value by measuring the length between the point the Q-wave begins a shallow negative deflection from the isoelectric line before the R-wave and where the S-wave returns from a negative deflection from the isoelectric line just after the R-wave.

• 9

  Compare the measurement to accepted standards classifying the length of the QRS complex as less than 0.12 millisecond.

• 10

  Examine the EKG strip for the presence of a positively deflected T-wave after every QRS complex for at least 600 milliseconds.

• 11

  Count the rate of contraction of the heart over a 600 millisecond EKG strip recording. If all previous measurement criteria are met, and if the patient's heart rate is less than 60 beats per minute, the rhythm can be identified as sinus bradycardia.