Hello! Thank you for asking on HCM! Regarding your concern, I would explain that during the early hours in the morning catecholamines and cortisol have their higher blood levels. This can explain why heart attacks occur more often in the morning. But facing your actual situation, some different factors may have influenced to your racing heart including the above explanation. As no any additional complains was present (no chest pain, shortness of breathing, etc), there is not any raised suspicions for an acute cardiac problems. Nevertheless, I recommend you a routine check up to your GP for a comprehensive physical exam and some blood tests (fasting glucose, complete blood count, ESR, etc) to exclude any subtle health problem. Hope to have been helpful to you. Greetings! Dr. Iliri