Mr. Luo, a reader from Guizhou, asked: I am 43 years old and often have heartburn, chest pain and occasional dizziness about 10 minutes after waking up in the morning. However, an electrocardiogram done at the hospital showed left ventricular hypertrophy; the ultrasound suggested no significant abnormalities. Since I had a cerebral hemorrhage 3 years ago, my doctor said I could have a 24-hour ambulatory ECG. What kind of person needs a 24-hour ECG? Answer: Symptoms of panic, chest tightness, and left ventricular hypertrophy are often precursors of heart disease, according to Zhou Tao, Director of Cardiovascular Medicine at the Third Affiliated Hospital of Southern Medical University. To further clarify the diagnosis, it is indeed necessary for this patient to have a 24-hour ambulatory electrocardiogram. Compared with ordinary ECG, 24-hour ambulatory ECG can continuously record about 100,000 times of ECG signals, so the doctor can see the patient’s heart condition at any time and easily detect arrhythmia, myocardial ischemia, angina pectoris, which is an effective detection method to clarify the cause for patients with panic, chest tightness and heart pain, dizziness and black eyes, and unexplained fainting. This is a great reference for people who are not obviously unwell themselves and whose doctors highly suspect cardiovascular disease. Patients are advised to record the duration of panic and chest tightness before having a 24-hour ambulatory electrocardiogram performed in a targeted manner. It should be noted that when performing 24-hour ambulatory ECG testing, patients should not deliberately avoid daily activities and should maintain their usual habits in order to clarify the connection between exercise and symptoms such as arrhythmia, myocardial ischemia and angina; during the testing process, a good diary should be kept to record the activities throughout the day and the exact time of symptom onset for the doctor’s reference when analyzing the ECG.