Bradycardia

There can be many forms of bradycardia. Commonly seen blocks include sinus bradycardia, and for multiple blockages, complete and 3rd-degree heart block.

In this lesson, we’ll look more closely at an example of what bradycardia looks like on an ECG for an adult patient and see what findings and measurements lead us to that conclusion.

It’s vital to remember that if there are signs of bradycardia, regardless of whatever underlying reasons that are causing the patient to display symptoms related to bradycardia, we must first treat for the bradycardia, as it takes precedent over those underlying causes.

*Bradycardia ECG for Adult Patient

1. The Heart Rhythm

The first thing you’ll want to look at is the heart rhythm. Does the heart rhythm look regular? Or does it look irregular? In the above graphic, it’s regular.

2. The Heart Rate

Next, you’ll want to look at the heart rate of the patient. What is the patient’s heart rate? Is it normal? Or is it too slow or too fast? In this case, it’s too slow, as the rate is less than 60 beats per minute.

3. P-Wave

After looking at the heart rate, check to see if the patient’s P-waves look normal by asking yourself the following few questions.

• Are the patient’s P-waves present? In this case, the answer is, yes.
• Do they occur regularly? The answer is yes again.
• Is there one P-wave for each QRS complex? Yes, there is.
• Are the P-waves smooth, rounded, and upright? The answer is again, yes.
• Do all the P-waves have a similar shape? Yes, they all have a similar shape.

4. PR Interval

Next, look at the PR interval on the patient’s ECG readout and ask yourself the following questions:

• Is the PR interval normal, meaning between .12 and .20 seconds or is it contained within one large square on the readout? The answer is yes, it’s between .12 and .20 seconds, consistent, and contained within one large square.
• Is the PR interval constant? Yes, it is.

5. QRS Complex

The last thing you should look at to determine if the sinus rhythm is normal or not is the QRS complex and ask yourself these questions while you do:

• Is the QRS interval less than .12 seconds? Yes, the QRS interval is between .06 and .11 seconds.

Remember, as long as the QRS fits within two small squares on the ECG printout and is not greater than three small squares, it’s within the normal range.

• Is the QRS complex wide or narrow? In this case, it’s narrow.
• Are the QRS complexes similar in appearance or are there noticeable differences? In this case, we can see that each looks similar.

So, what is your cardiac interpretation? Based on these questions and on the findings from the ECG readout above, it’s safe to say that this patient is in sinus bradycardia.

1. We have a regular rhythm.
2. We have a slower than normal heart rate, at less than 60 beats per minute.
3. The P-waves look normal, with each being followed by a QRS complex.
4. The PR interval is between .12 and .20 seconds.
5. The QRS is between .06 and .11 seconds.
6. And the P:QRS ratio is 1:1.

Bradycardia in adults can result from many things – from benign causes like aerobic exercise to pathological causes, such as:

• Structural heart disease
• Damage to the electrical conduction system (usually related to a past heart attack)
• Hypoxia
• Metabolic dysfunction
• Certain medications

Having said that, if the patient is showing symptoms related to their bradycardia, you should begin treating them for it while also asking yourself the following questions:

1. What is the underlying cause of the bradycardia?
2. Is that underlying cause reversible?

Additional Bradycardia Information

Bradycardia is defined as a slower than normal heart rate. The heart rates of adults at rest is usually between 60 and 100 beats per minute. For adults with bradycardia, their hearts beat fewer than 60 times a minute.

Symptomatic Bradycardia

Symptomatic bradycardia is defined as a heart rate less than 60 beats per minute that elicits signs and symptoms. However, the heart rate is typically less than 50 beats per minute. Symptomatic bradycardia exists when the following three criteria are present:

1. The heart rate is slow.
2. The patient has symptoms.
3. The symptoms are due to the slow heart rate.