S1Q3T3 Pattern in Right Heart Strain
Jul 20, 2026The S1Q3T3 pattern is one of the classic ECG findings associated with acute right heart strain, although it is neither sensitive nor specific for pulmonary embolism. It reflects a sudden increase in right ventricular afterload that causes the right ventricle to acutely dilate and struggle against an elevated pulmonary vascular resistance.
As the right ventricle becomes pressure overloaded, electrical activation through the ventricle is altered, producing several characteristic ECG findings that reflect acute right heart strain. While S1Q3T3 is one of the best known patterns, it is only one piece of a much broader physiological response.
In the accompanying video, we will dive into the anatomy and physiology of acute right heart strain and explain how these changes produce the characteristic ECG patterns seen in conditions such as pulmonary embolism.
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