Usefulness of negative [formula omitted] upstroke pattern for assessment of left ventricular relaxation in coronary artery disease

Abstract

It has been reported that regional asynchrony due to acute ischemia disturbs the exponential nature of left ventricular (LV) pressure reduction and may alter the pattern of (−)dP dt upstroke curve. If LV pressure decreases exponentially during the isovolumic relaxation period ( P = Ae −t T + B , where A and B = constants, t = time and T = time constant), the (−)dP dt upstroke curve should also be exponential and upward-convex because dP dt = A( −t T )e −t T . To test this theory in humans, the LV (−)dP dt upstroke curve was analyzed in 9 normal subjects, 12 patients with effort angina pectoris (AP) and 15 with old myocardial infarction (MI) under the basal conditions. The (−)dP dt upstroke was convex-upward in all normal subjects, but convex-downward in 9 of 12 patients with AP and in all patients with MI, which suggests nonexponential decrease in LV pressure in the groups with AP and MI. The dP dt ( 20 60 ), which is the ratio of the (−)dP dt value at 20 ms after peak (−)dP dt to that at 60 ms after peak (−)dP dt , was significantly lower in the group with AP (1.70 ± 0.07) and in the group with MI (1.61 ± 0.13) than in normal subjects (2.08 ± 0.18) (p < 0.005). This indicates that (−)dP dt upstroke 20 to 60 ms after peak (−)dP dt increases more slowly in the groups with AP and MI than in normal subjects. Theoretical consideration showed that such a slower increase of the upstroke resulted from impaired early to midrelaxation. The dP dt ( 20 60 ) correlated with T (r = −0.75), suggesting that T reflects impaired early to midrelaxation. Thus, disturbance of LV pressure decrease exists during the isovolumic relaxation period in patients with AP and MI, even at rest. The downward-convex contour of the (−)dP dt upstroke curve reflects such a disturbance, and suggests impaired LV early- to midrelaxation, probably due to regional asynchrony.