Pacemaker syndrome refers to a group of symptoms that includes nausea, palpitations, chest pain, fatigue, breathlessness, pre‑syncope and syncope. The underlying cause of pacemaker syndrome is not fully understood. It is thought to be caused by loss of the heart's natural AV sequence, causing simultaneous contraction of the atria and ventricles. Under these circumstances, blood in the atrial chamber is not efficiently expelled into the ventricles, which results in large reductions in systolic blood pressure and cardiac output. There are difficulties in the diagnosis of pacemaker syndrome because of the overlap of the symptoms of pacemaker syndrome with many symptoms typical of cardiac disease, and with symptoms arising from comorbidities, particularly in elderly patients. Pacemaker syndrome may develop in patients with functional atria who receive a single‑chamber ventricular pacemaker. Severe pacemaker syndrome can be eradicated by an upgrade to a dual‑chamber pacemaker, although this may be associated with an increased risk of perioperative complications. Patients with mild pacemaker syndrome often adapt over time to the condition and do not require a pacemaker upgrade.