SummaryThe decision to administer thrombolysis in submassive pulmonary embolism is undertaken based on risk stratification to prevent further cardiorespiratory deterioration. Although right ventricular dysfunction has been used to risk stratify haemodynamically stable patients with acute pulmonary embolism, there is still much controversy in the use of thrombolysis for its treatment. The European Society of Cardiology guidelines suggest thrombolysis should be reserved for rescue reperfusion. However, we present a unique case of submassive pulmonary embolism in which transthoracic echocardiography visualised dynamic left ventricular outflow tract obstruction secondary to right ventricular dilatation, which led to the decision to instigate thrombolysis therapy. A 68‐year‐old man presented with submassive pulmonary embolism with evidence of right ventricular dysfunction but was haemodynamically stable. He was initially commenced on anticoagulation but echocardiography revealed significant right ventricular dilatation and left ventricular outflow tract obstruction, signifying a high risk of impending cardiac arrest. After deliberation, full‐dose thrombolysis was administered. Subsequently the patient's symptoms and haemodynamics improved significantly and repeat echocardiography demonstrated that the right ventricular and left ventricular size and function had returned to normal. We suggest echocardiography is used to assess right heart, left heart and outflow dynamics to individualise thrombolysis therapy in patients with submassive pulmonary embolism.