Additional electrocardiographic abnormalities can be seen in pericardial disease. In chronic recurrent pericarditis thickenning of the pericardial tissue can result in a generalized decrease in all wave form amplitude, termed low voltage. A triad of changes that is virtually diagnostic of pericardial effusion consists of low voltage, ST segment elevation and alternating QRS voltage, termed electrical alternans. In chronic constrictive pericarditis, there is often generalized T wave inversion accompanied by a decreased voltage.