Hello! Thank you for asking on HCM! You need to be very careful and to avoid excessive physical exertion, facing your reduced LV ejection fraction. I would recommend just waking and continuing to be active that way, but no exaggerated strain. If you experience such high heart rates again, that you need to see your attending cardiologist for a comprehensive evaluation, and define a possibility of ICD implantation (if life threatening arrhythmia results). Hope to have been helpful to you. Greetings! Dr. Iliri