HEART RATE DEFLECTION POINT AND MYOCARDIAL FUNCTION DURING EXERCISE AFTER MYOCARDIAL INFARCTION 38

Abstract

The purposes of this study were as follows: 1. that in patients after myocardial infarction a turn point (HRTP) of the heart rate/performance curve(HRPC) can be observed; 2. that an upward deflection of the HRPC is correlated with a diminished myocardial function during exercise. 49 male patients performed an cycle ergometer test. Via blood lactate concentration 3 phases of energy supply were defined (I aerobic, II aerobic-anaerobic transition and III: anaerobic). HRTPs were assessed by linear turn point analysis. Degree and direction of the deflection of HRPC was described as factor k (k>0, downwards-; k<0, upwards-deflection). At all phases EDV, ESV, SV and LVEF were calculated by RNA. To assess changes, a quotient (Q) between II and III was calculated for EDV, ESV, SV and LVEF. A downward- (n=2), a linear course(n=5), and an upwards-deflection (n=42) of HRPC was found. Thus, HRTP was seen in 44 cases. The transition point from II to III was determined at 81±17 Watts which correlated (p<0.001) with HRTP (81±18 Watts). From II to III we found a significant decrease of LVEF. Correlation was also observed between the k and Q for EDV (r=.399, p<.0,01), ESV(r=.541, p<.001) and LVEF (r=-.524, p<.001). To prevent myocardial overloading, it is useful to determine HRTP indicating the work load where LVEF decreases, caused by an increase in ESV that is larger than the in EDV.