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Now let’s take a look at the normal sinus rhythm. When trying to determine the significance of an ECG, I think it’s helpful to know what is abnormal by first understanding It’s always helpful to know what is abnormal by first understanding what’s normal. And that’s why we are going to look more closely at the normal sinus rhythm first, and its ECG and pay special attention to its findings and measurements, waves and complexes. So to do so, we’re going to start with the rhythm: Is the rhythm regular or irregular? In this case, it’s regular. Next, we look at the rate. What is the rate? It’s 80 beats per minute. Is the rate normal, fast or slow? We know that the rate is normal, because the rate is between 60-100 beats per minute. Next, we evaluate the P-wave. Are they present? We can clearly see that the P-waves are indeed present. Do they occur regularly? We see that each of the P-waves does occur regularly. Is there one P-wave for each QRS complex? There is one p-wave for each QRS complex. Are the P-waves smooth, rounded, and upright? Yes! Do all P-waves have similar shapes? Yup, each have a uniform shape and are smooth and rounded. So now, we want to know what the PR interval is for this ECG. The PR interval that is falling within the norm: 0.12-0.20 seconds is okay. And in this case, yes, the PR interval is contained within one large box which equals .2 seconds. Is the PR interval constant? Yes. So now we move on to the QRS complex of the ECG. Is the QRS interval less than 0.12 seconds? Yes it is, and as long as the QRS fits within 2 small boxes and no larger than 3 small boxes, the QRS is within normal range. Is the QRS wide or narrow? Well, in this case, the QRS is narrow. Are the QRS complexes similar in appearance? We can see that each one looks similar. And finally, what is the cardiac interpretation and its clinical significance, which is something we’re going to be asking after each one of the rhythm strips. In this case, based on our findings we can see that we have a regular rhythm with a normal rate. The P-waves all look normal, each P-wave is followed by a nice, normal QRS complex. The PR interval is less than .20 seconds, and the QRS is less than .12 seconds. So with these findings, we can interpret the rhythm to be a normal sinus rhythm. Now unless the patient has no pulse or other serious signs or symptoms, there is no serious significance to this cardiac rhythm.
When talking about treating a patient for something that we consider abnormal, it's always helpful to define and understand what normal looks like, in this case, for a normal sinus rhythm.
In this lesson, we'll look more closely at an example of a normal sinus rhythm on an ECG (aka EKG) for an adult patient and see what findings and measurements are considered normal, and what to be on the lookout for that would be considered abnormal. And at the end of the lesson, we'll provide a Word about acute coronary syndrome.
*Normal Sinus Rhythm ECG/EKG for Adult Patient
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.
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?
Remember, to determine the patient's heart rate you'll want to observe the following areas on the ECG paper printout and perform the following calculations.
The horizontal axis of ECG paper grids is where time is measured. Each small square is 1mm in length and represents .04 seconds. Each larger square is 5mm in length and represents .2 seconds. Therefore a 6 second interval would be 30 large squares.
To determine the heart rate, count the number of QRS complexes over this 6 second interval and multiply by 10.
In the ECG above, the rate is 80 beats per minute, and this is normal. For an adult patient, the normal heart rate range is 60 to 100 beats per minute.
After looking at the heart rate, check to see if the patient's P-waves look normal by asking yourself the following few questions.
The answer to each of those questions is, yes, meaning the P-waves are normal.
Next, look at the PR interval on the patient's ECG readout and ask yourself the following questions:
The answer to both questions is, yes.
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:
Pro Tip: 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.
So, what is your cardiac interpretation? (This is something we'll be asking ourselves each time we look at a new ECG rhythm.) Based on these questions and on the findings from the ECG readout above, it's safe to say that the patient has a normal sinus rhythm.
Unless the patient has no pulse or other serious signs or symptoms, it's safe to assume that there is nothing of significance, in a negative sense, from this patient's cardiac rhythm.
As an ACLS provider, you should have the basic knowledge to assess and stabilize patients with acute coronary syndrome (ACS). In these cases, you will use the ACS algorithm as your guide to clinical strategy.
The initial 12-lead ECG is used in all ACS cases to classify patients into one of three ECG categories. Each of these categories has different strategies of care and management needs.
The three ECG categories are ST-segment elevation suggesting ongoing acute injury, ST-segment depression suggesting ischemia, and nondiagnostic or normal ECG. All three are outlined in the ACS Algorithm.
Key components of these cases are:
Sudden cardiac death and hypotensive bradyarrhythmias may occur with acute ischemia. You should learn to anticipate these rhythms and be prepared for immediate attempts at defibrillation and administration of medication or electrical therapy for symptomatic bradyarrhythmias.