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Arterial baroreflex impairment in patients during acute coronary occlusion

K. E. Juhani Airaksinen, MD^*, Kari U. O. Tahvanainen, MSc, Dwain L. Eckberg, MD, Matti J. Niemelä, MD^*, Antti Ylitalo, MD^* and Heikki V. Huikuri, MD, FACC^*

^* Cardiovascular Laboratory, Department of Medicine, University of Oulu, Oulu, Finland
Department of Clinical Physiology, University of Tampere, Tampere, Finland
Departments of Medicine and Physiology, Hunter Holmes McGuire Department of Veterans Affairs Medical Center and Medical College of Virginia at Virginia Commonwealth University, Richmond, Virginia, USA

View larger version (22K): [in a new window]   Figure 1 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 90% stenosis in left anterior descending coronary artery in a 58-year-old male patient. The lower panels show respective baroreflex slopes derived from the time windows shown by broken vertical lines in the upper panels. In this case, coronary occlusion (hatched bars, right upper panel) causes a mild, progressive bradycardia already before the phenylephrine bolus. Phenylephrine bolus (150 µg) causes a rise in systolic blood pressure, but at the end of the coronary occlusion RR intervals suddenly shorten despite continuing pressure rise. Baroreflex sensitivity could not be calculated because of the loss of linear relationship between the RR intervals and the preceding systolic blood pressure values despite adequate blood pressure reaction during coronary occlusion in 13 patients.

View larger version (22K): [in a new window]   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.