Influence of an upward shift in the V1 electrode position on the P-terminal force.

In this study, an attempt was made to determine how the P-terminal force (P-tf) was influenced by an upward shift of the V1 electrode in 508 normal subjects, 101 patients with hypertension, 22 with chronic obstructive lung disease (COLD), and 55 with old myocardial infarction. An abnormal V1 P-tf (less than or equal to -0.03 mm . sec) was observed in 3.1% of normal subjects, 11.9% of cases with hypertension, 9.1% of cases with COLD, and 21.8% of cases with old myocardial infarction. By shifting the electrode position one intercostal space above the conventional level of V1, an abnormal P-tf was seen in 12.2% of normals, and in 32.7, 36.4, and 43.6% of cases with hypertension, COLD, and old myocardial infarction, respectively. It can be concluded therefore that the P-tf is greatly influenced by a slight upward shift of the V1 electrode, and correct placement of the V1 electrode is essential for P-tf assessment.