rSR' on an ECG (electrocardiogram) refers to a specific type of QRS complex morphology where there are two positive (upward) deflections, often described as "rabbit ears." Specifically, it describes a QRS complex that displays a small 'r' wave, followed by a deep 'S' wave, and then another 'R' wave (denoted as 'R').
Understanding the rSR' Complex
The rSR' pattern signifies a delay in ventricular depolarization. While sometimes a normal variant, it can also indicate underlying cardiac conditions. Importantly, when ECG readers note an rSR' pattern, the QRS interval is typically normal (0.08-0.10 seconds) or only slightly prolonged (0.11 seconds). The relative sizes of the 'r' and 'R' waves can also be documented (e.g., small "r" or large "R").
Clinical Significance
The presence of an rSR' pattern, especially when associated with a widened QRS complex (greater than 0.12 seconds), is often associated with:
- Right Bundle Branch Block (RBBB): This is the most common cause, where the electrical impulse is delayed in the right ventricle, leading to the characteristic rSR' pattern, often seen in leads V1 and V2. In RBBB, you'd also expect to see a wide S wave in leads I and V6.
- Incomplete Right Bundle Branch Block (IRBBB): This is a variation of RBBB with QRS duration between 0.10-0.12 seconds. The rSR' morphology is frequently observed in the right precordial leads (V1-V3).
- Ventricular Hypertrophy: Right ventricular hypertrophy can also lead to an rSR' pattern.
- Other Cardiac Abnormalities: rSR' can also be seen in conditions affecting the right ventricle or conduction system.
Differentiating rSR' Patterns
It is important to consider the entire clinical context and ECG tracing when interpreting an rSR' pattern. The presence of other ECG abnormalities and the patient's medical history are crucial for accurate diagnosis. Factors that help differentiate causes include QRS duration, the morphology of the T wave, and the presence of other conduction abnormalities.
Summary
The rSR' complex on an ECG represents a specific type of QRS morphology that may indicate delayed ventricular depolarization. While it can be a normal variant, it's essential to consider potential underlying cardiac conditions, particularly right bundle branch block. A thorough evaluation of the entire ECG and patient history is necessary for accurate interpretation.
