An RSR’ (pronounced “RSR prime”) pattern on an ECG is usually not dangerous. It appears in up to 7% of people with no apparent heart disease, making it one of the more common findings that shows up on a routine heart tracing. In most cases, it reflects the normal way electrical signals move through your heart rather than a sign of something wrong. That said, the same pattern can occasionally point to real cardiac conditions, so context matters.
What the RSR’ Pattern Actually Is
When your heart beats, electrical signals travel through it in a specific sequence, and an ECG records that activity as a series of waves. The QRS complex is the part of the tracing that represents your ventricles (the heart’s main pumping chambers) contracting. Normally, the leads placed on the right side of your chest (called V1 and V2) show a small upward blip, then a deep downward dip, and that’s it.
With an RSR’ pattern, there’s an extra small upward blip at the end, creating a shape that looks like an “M” or a double peak. The “r” is the first small peak, the “S” is the dip, and the “r prime” is that second small peak. This happens because the last wave of electrical activation through the base of your heart is picked up more prominently by those right-sided leads. Sometimes this is simply due to where the ECG stickers were placed on your chest. If the electrodes sit slightly higher than the standard position, they’re more likely to catch that final electrical wave and produce the pattern even when your heart is perfectly normal.
When RSR’ Is a Normal Variant
The single most important number to look at is the QRS duration, which measures how long it takes for the electrical signal to pass through the ventricles. When the QRS is under 120 milliseconds and the second peak is small, the RSR’ pattern is generally considered a benign normal variant. No treatment, no restrictions, no follow-up needed.
This is especially common in young, healthy people and in athletes. A study of 347 competitive athletes found the RSR’ pattern in about 24% of senior athletes and 17% of junior athletes when ECG leads were placed slightly higher on the chest. In most of those cases, further testing showed nothing concerning. The pattern is so frequent in fit, active people that it’s considered part of what cardiologists call “athlete’s heart,” a collection of harmless ECG quirks caused by regular intense exercise.
Conditions That Can Cause the Pattern
While the RSR’ pattern is often harmless on its own, it can also be a clue to several conditions worth investigating. The key is whether other abnormalities show up alongside it on the ECG, or whether you have symptoms like shortness of breath, fainting, or exercise intolerance.
Right Bundle Branch Block
If the QRS duration is 120 milliseconds or longer, the RSR’ pattern likely represents a right bundle branch block (RBBB), meaning the electrical signal is delayed as it travels through the right side of the heart. An incomplete RBBB falls between 110 and 120 milliseconds, while a complete RBBB is 120 or above. Isolated RBBB without other heart disease is common, particularly as people age, and often doesn’t require treatment. But when it appears alongside symptoms or other ECG changes, it can signal underlying problems like heart muscle disease or elevated pressure in the lungs.
Atrial Septal Defect
An atrial septal defect (ASD) is a hole between the upper chambers of the heart. It’s one of the more well-known causes of an RSR’ pattern, particularly in children. The hole allows extra blood to flow into the right side of the heart, gradually enlarging it. Research has shown that the height of the second peak (the r’) correlates with how enlarged the right ventricle has become, making it a useful screening clue. The RSR’ pattern in this case isn’t caused by a wiring problem in the heart. It’s a direct reflection of the right ventricle being physically bigger than it should be.
Brugada Pattern
This is the one that makes the RSR’ pattern a topic of real concern. Brugada syndrome is a rare genetic condition that can cause dangerous heart rhythms and, in the worst cases, sudden cardiac death. The Brugada pattern also shows up in leads V1 and V2 and can look superficially similar to an RSR’ pattern. The critical difference is what happens after that second peak: in Brugada syndrome, the ST segment (the part of the tracing right after the QRS complex) is elevated in a distinctive coved or saddle-back shape. A plain RSR’ pattern without that ST-segment elevation is not a Brugada pattern.
In the athlete study mentioned above, a small number of athletes with RSR’ patterns also had ST-segment elevation that raised concern for a possible Brugada sign. Those athletes were offered a provocative drug test, which uses medication to unmask the full Brugada pattern. In every case where the test was performed, the result came back negative.
What Separates Harmless From Concerning
A few features help distinguish a benign RSR’ from one that warrants further investigation:
- QRS duration under 120 ms with a small second peak strongly favors a normal variant.
- QRS duration of 120 ms or longer suggests a right bundle branch block and may need further evaluation depending on the clinical picture.
- A tall second peak (r’ taller than the first r) is more likely to reflect right ventricular enlargement or a conduction abnormality.
- ST-segment elevation following the RSR’ raises the question of Brugada syndrome and typically prompts additional testing.
- Symptoms like fainting, palpitations, or unexplained shortness of breath alongside the pattern make further workup more important.
What Happens if Further Testing Is Needed
If your RSR’ pattern has features that raise questions, the next step is usually an echocardiogram, an ultrasound of the heart. This painless, non-invasive test lets your doctor see the heart’s structure in real time: the size of the right ventricle, whether a septal defect is present, and how well the valves are functioning. It’s the most straightforward way to rule out the structural problems that an RSR’ pattern can hint at.
In rare cases where a Brugada-like pattern is suspected, a provocative test may be recommended. This involves receiving a short-acting medication through an IV while connected to an ECG monitor. The drug exaggerates certain electrical properties of the heart, making a true Brugada pattern obvious if it’s present. The test takes about 30 minutes and is done in a controlled setting.
For the vast majority of people who see “RSR’ pattern” on their ECG report, no additional testing is needed. The pattern alone, with a normal QRS duration and no symptoms, is one of the most common and most benign findings in electrocardiography.