Assessing baroreflex sensitivity in post-myocardial infarction patients: comparison of spectral and phenylephrine techniques

Department of Biomedical Engineering, Institute of Care and Scientific Research, Rehabilitation Institute of Montescano, Pavia, Italy. bing@fsm.it

OBJECTIVES: This study sought to compare, in post-myocardial infarction patients, baroreflex sensitivity (BRS) measured by the phenylephrine method (Phe-BRS) with that estimated by the Robbe (Robbe-BRS) and Pagani (alpha-low frequency [LF] and alpha-high frequency [HF]) spectral techniques. BACKGROUND: BRS assessed by Phe-BRS has been shown to be of prognostic value in patients with a previous myocardial infarction, but the need for drug injection limits the use of this technique. Several noninvasive methods based on spectral analysis of systolic arterial pressure and heart period have been proposed, but their agreement with Phe-BRS has never been investigated in post-myocardial infarction patients. METHODS: The linear association and the agreement between each spectral measurement and Phe-BRS were assessed by correlation analysis and by computing the relative bias and the limits of agreement in 51 post-myocardial infarction patients. RESULTS: The correlation with Phe-BRS was r = 0.63 for Robbe-BRS, r = 0.62 for alpha-LF and r = 0.59 for alpha-HF. The relative bias was significant for alpha-LF (2.6 ms/mm Hg, p < 0.001) and alpha-HF (2.5 ms/mm Hg, p = 0.01) and not significant (-0.6 ms/mm Hg, p = 0.3) for Robbe-BRS. The normalized limits of agreement ranged from -98% to 95% for Robbe-BRS, from -67% to 126% for alpha-LF and from -108% to 143% for alpha-HF. When patients were classified according to left ventricular ejection fraction (LVEF, cutoff value 40%), the relative bias was higher in patients with a depressed LVEF, although statistical significance was high only for Robbe-BRS and was borderline for alpha-LF. The limits of agreement were similar in both groups of patients (p > 0.3). CONCLUSIONS: Despite a substantial linear association, the agreement between spectral measurements and Phe-BRS in post-myocardial infarction patients is weak because the difference can be as large as the BRS value being estimated. Phe-BRS is the measurement most associated with hemodynamic impairment. Because several factors within each method contribute to the overall difference, neither method can be defined as being better than the other in estimating baroreflex gain, nor can one be used as an alternative to the other. Ad hoc studies are needed to assess which method provides the most useful physiologic or pathophysiologic information or the most accurate prediction of prognosis.

This article has been cited by other articles:

				P. Ptaszynski, T. Klingenheben, B. Gerritse, and L. Kornet Risk stratification after myocardial infarction: a new method of determining the neural component of the baroreflex is potentially more discriminative in distinguishing patients at high and low risk for arrhythmias Europace, February 1, 2008; 10(2): 227 - 234. [Abstract] [Full Text] [PDF]

				Z. Lenard, P. Studinger, B. Mersich, G. Pavlik, and M. Kollai Cardiovagal autonomic function in sedentary and trained offspring of hypertensive parents J. Physiol., June 15, 2005; 565(3): 1031 - 1038. [Abstract] [Full Text] [PDF]

				Z. Lenard, P. Studinger, B. Mersich, L. Kocsis, and M. Kollai Maturation of Cardiovagal Autonomic Function From Childhood to Young Adult Age Circulation, October 19, 2004; 110(16): 2307 - 2312. [Abstract] [Full Text] [PDF]

				R. D. Lipman, J. K. Salisbury, and J. A. Taylor Spontaneous Indices Are Inconsistent With Arterial Baroreflex Gain Hypertension, October 1, 2003; 42(4): 481 - 487. [Abstract] [Full Text] [PDF]

				C. Keyl, A. Schneider, A. Gamboa, L. Spicuzza, N. Casiraghi, A. Mori, R. T. Ramirez, F. Leon-Velarde, and L. Bernardi Autonomic cardiovascular function in high-altitude Andean natives with chronic mountain sickness J Appl Physiol, January 1, 2003; 94(1): 213 - 219. [Abstract] [Full Text] [PDF]

				K. Sevre, J. D. Lefrandt, G. Nordby, I. Os, M. Mulder, R. O. B. Gans, M. Rostrup, and A. J. Smit Autonomic Function in Hypertensive and Normotensive Subjects : The Importance of Gender Hypertension, June 1, 2001; 37(6): 1351 - 1356. [Abstract] [Full Text] [PDF]

				M. T. La Rovere, G. D. Pinna, S. H. Hohnloser, F. I. Marcus, A. Mortara, R. Nohara, J. T. Bigger Jr, A. J. Camm, and P. J. Schwartz Baroreflex Sensitivity and Heart Rate Variability in the Identification of Patients at Risk for Life-Threatening Arrhythmias : Implications for Clinical Trials Circulation, April 24, 2001; 103(16): 2072 - 2077. [Abstract] [Full Text] [PDF]

				N. Takahashi, M. Nakagawa, T. Saikawa, T. Ooie, T. Akimitsu, K. Kaneda, M. Hara, T. Iwao, H. Yonemochi, M. Ito, et al. Noninvasive assessment of the cardiac baroreflex: Response to downward tilting and comparison with the phenylephrine method J. Am. Coll. Cardiol., July 1, 1999; 34(1): 211 - 215. [Abstract] [Full Text] [PDF]