Electrocardiographic diagnosis of acute coronary syndromes in patients with left bundle branch block or paced rhythm.

The population of patients with a pacemaker is constantly growing in number. Myocardial infarction in these patients, like in patients with left bundle branch block (LBBB), is called the undetermined type and characterizes the highest risk of death. Therefore the early and correct diagnosis of AMI is very important. The electrocardiographic criteria of the recognition of acute myocardial infarction (AMI) in patients with a ventricular pacing are similar to the electrocardiographic criteria of the recognition of AMI in patients with LBBB. They are applicable in the first phase of AMI's diagnostic process and they are known as Sgarbossa's criteria. However, one should remember about differences between these two groups of patients and therefore particular criteria have got different significance in patients from each group. There are three Sgarbossa's criteria: ST-segment elevation of >/= 5 mm in the presence of a negative QRS complex, ST-segment elevation of >/= 1 mm in the presence of a positive QRS complex and ST-segment depression of >/= 1 mm in lead V1, V2 or V3. In spite of all limitations of use ECG records in the recognition of AMI in patients with a ventricular pacing it should be remembered, that this method (together with a typical medical history) is still the simplest, the cheapest and the most available means of an early diagnosis of AMI. In patients with chest pain, the presence of a pacemaker should not defer the execution of ECG recording because ECG may be very helpful in establishing of the diagnosis. (Cardiol J 2007; 14: 207-213).