<p>The drug should be used with caution (which may include monitoring) in patients with cardiac arrhythmias, especially third degree atrioventricular block and tachyarrhythmias (accelerated and/or irregular heart beat), idiopathic subvalvular aortic stenosis, hypertrophic obstructive cardiomyopathy, severe heart disease, particularly acute myocardial infarction, ischaemic heart disease, congestive heart failure, occlusive vascular diseases, particularly arteriosclerosis, arterial hypertension and aneurysm. Caution should also be observed when treating patients with known or suspected prolongation of the QTc interval, either congenital or drug induced (QTc &gt;0.44 seconds). Formoterol itself may induce prolongation of the QTc interval.</p>