OBJECTIVES Heart rate recovery (HRR) at 1 minute after peak exercise is a measure of vagal reactivation and is considered a marker of parasympathetic activity. Blood pressure recovery index at 3 minutes (BPRI3) might reflect sympathetic activity. We aimed to assess HRR at 1 minute and BPRI3 in an attempt to determine parasympathetic and sympathetic activity in patients with slow coronary flow (SCF).
STUDY DESIGN The study included 24 patients (19 males, 5 females; mean age 51±7 years) with angiographically diagnosed SCF using the Thrombolysis in Myocardial Infarction (TIMI) frame-count method. Heart rate recovery was calculated as the difference between the heart rate at peak exercise and heart rate at the relevant minute of recovery. Blood pressure recovery indexes were defined as the ratios of recovery systolic blood pressures at 1, 2, and 3 minutes to the systolic blood pressure at peak exercise. The results were compared with those of 26 age- and sex-matched subjects (19 males, 7 females; mean age 52±8 years) with normal flow.
RESULTS Patients with SCF had significantly lower HRRs at 1 minute (19±4 vs 25±6 beats/min; p<0.001) and 2 minutes (36±9 vs 44±13 beats/min; p=0.042) compared to controls with normal coronary flow. Blood pressure recovery index at 3 minutes was not significantly different between the two groups (0.81±0.07 vs 0.84±0.12; p=0.440).
CONCLUSION Attenuation in HRR at 1 minute suggests the presence of reduced vagal tone in patients with SCF. Decreased vagal activity may contribute to the mechanisms responsible for SCF.
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