Q. Can you define P-Waves?

Changes in P-wave morphology have been well described in resting tracings and are very useful in identifying right and left sided hemodynamic alterations due to both volume and pressure load. Careful study has revealed that it is P-wave deviation i.e. altered during ischaemia. As left ventricular end diastolic pressure increases with a loss of ventricular compliance, the left atrial wall distended by increasing pressure, which apparently slows conduction through the atrium and this prolongs the depolarization wave. The low amplitude of the P-waves however, makes the measurements difficult, which probably accounts for the low sensitivity of these findings. When the other signs of ischaemia are absent, the deviation of P-wave from rest to exercise should be measured (best in lead 2). An increased duration of greater than 20 milliseconds provides a specificity of 64 per cent.