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Figure 2 Computer output of beat-to-beat RR intervals and invasive systolic blood pressure (SAP) during phenylephrine tests in the baseline (left upper panel) and during balloon occlusion (right upper panel) of a 67% stenosis in left anterior descending coronary artery in a 62-year-old female patient. The lower panels show respective baroreflex slopes derived from the time windows shown by broken vertical lines in the upper panels. During coronary occlusion, the blood pressure falls despite the same phenylephrine dose (150 µg) as in the baseline test and the fall is accompanied by a paradoxical, progressive bradycardia. The resulting baroreflex slope would have been negative, but because of the loss of positive statistical correlation between the RR intervals and preceding systolic pressures these cases (n = 6) were excluded from the statistical analysis of correlation coefficients and baroreflex slopes. Coronary occlusion is shown by hatched bars (right upper panel). Note the differences in the time scales and RR interval scales in the recordings.
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