If you fall asleep and your heart suddenly skips a beat, you may have a cardiac arrhythmia, such as ventricular pre-systole, atrial fibrillation, paroxysmal supraventricular tachycardia, etc., or you may have a cardiac neurosis. 1. Arrhythmia: patients with increased vagal tone during sleep can cause abnormalities in the cardiac conduction system and arrhythmia, common arrhythmias include ventricular pre-systole contraction, atrial fibrillation, paroxysmal supraventricular tachycardia, etc. Patients may suddenly feel palpitations, tachycardia, chest tightness and other manifestations, and wake up from sleep. 2. Cardiac neurosis: patients do not have organic cardiac lesions, but the symptoms of cardiovascular disease as the main manifestations of clinical syndromes, the patient may be manifested as palpitations, chest tightness, chest pain and other discomforts, often accompanied by emotional anxiety, nervousness, insomnia and other manifestations, but also to fall asleep feeling cardiac discomfort and wake up. If patients often fall asleep with a sudden heartbeat, it is recommended that they go to the hospital for further clarification so as not to delay their condition.