P wave of electrocardiogram in early ischaemic heart disease.

The P wave 'terminal force' in lead Vi of the electrocardiogram has been measured in I59 patients with early ischaemic heart disease and in 206 normal subjects. For subjects over the age of 40, a P wave terminalforce more negative than -00o2o mm sec wasfound in under i per cent of the normals and in i8 per cent of the patients with ischaemic heart disease. The P wave terminal force was more negative than o-o3o mm sec in none of the normals and in 7 per cent of the patients. In the group with ischaemic heart disease the QRST patterns were normal in 17 of the 27 with a P wave terminalforce more negative than 0020 mm/sec and in 5 of the ii with terminal force more negative than -o o3o mm sec. It is concluded that the P wave may be the first component of the electrocardiogram to become abnormal in ischaemic heart disease. A P wave terminal force more negative than o 0o2o mm sec in an apparently normal subject should lead to the suspicion of this diagnosis and further investigation.