Merzin Salman

• Exercise.
• Sex.
• Nipple stimulation.
• Acupuncture.
• Acupressure.
• Castor oil.
• Spicy foods.
• Waiting for labor.

Sometimes an electrocardiogram (ECG) reader will mention an rSR’ on the ECG reading. Sounds really important, doesn’t it? In reality, most of the time it is a benign finding. Here, I will tell you what is an rSR prime (rSR’), and some of the common and uncommon etiologies.

Not to belittle anyone, but to understand what an rSR’ is, we first need to know the components of the QRS complex.

Here are some examples of QRS complexes:

Now that we know the parts of the QRS complex, an rSR’ is simple. It is an R-wave, followed by an S-wave, followed by another R-wave. In other words, an upward deflection, followed by a downward deflection, followed by another upward deflection.  Voila! That’s it. When an ECG reader mentions it, though, he/she is referring to an rSR’ in leads V1 and/or V2. An rSR’ in other leads is typically insignificant. Additionally, this finding typically implies that the QRS interval is normal (0.08 – 0.10 seconds) or only mildly prolonged (0.11 seconds). There is little to no significance if this is seen in the other leads.

Another tidbit is that the reader may write a small “r” or a large “R” to denote which upward deflection is bigger. For example, rSR’ suggests a small R-wave, followed by an S-wave, followed by a large R-wave. Likewise, RSr’ suggests a large R-wave, followed by an S-wave, followed by a small R-wave.

As mentioned above, most of the time an ECG reader mentions an rSR’ pattern on the ECG, the QRS complex is narrow or only mildly prolonged. A majority of the time this finding is a benign finding from abnormally high lead placement of V1 and V2, a normal variant seen due to normal depolarization of the intraventricular septum, or an incomplete right bundle branch block. Additionally, this pattern can be seen in athletes or people with sunken chests (pectus excavatum) (1). In some cases, the rSR’ is significant. Pathological conditions causing this include Brugada Syndrome, right ventricular enlargement, right ventricular hypertrophy, or abnormal conduction through a bypass tract with preexcitation or Wolff Parkinson White (WPW) (1). In these cases, hopefully, the ECG interpreter is able to tease these diagnoses out and be more specific with his/her reading.

An rSR’ in V1 or V2 in a widened QRS complex is abnormal. This may be due to a right bundle branch block (RBBB), preexcitation or Wolff Parkinson White (WPW), or a ventricular beat.

As you may have guessed by now, most of the time, and rSR’ is a benign finding. It is often from lead misplacement, is a normal variant, or may indicate a slight right ventricular conduction delay. Clinically this finding is insignificant and does not affect the patient’s prognosis. Remember that this finding is really only mentioned with regard to leads V1 and V2. When I read an ECG, I comment further if the rSR’ represents significant or possible significant pathology. I hope that other ECG readers do the same.

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