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HEART RHYTHM DISTURBANCES

Beat-to-beat analysis of pressure wave morphology for pre-symptomatic detection of orthostatic intolerance during head-up tilt

Department of Internal Medicine and Cardiology, University of Florence, School of Medicine, Florence, Italy

Manuscript received March 17, 2004; revised manuscript received July 26, 2004, accepted July 29, 2004.

^* Reprint requests and correspondence: Dr. Salvatore M. Romano, Department of Critical Care, School of Medicine, University of Florence, Viale Morgagni 85, I-50134 Florence, Italy (Email: m.romano{at}dac.unifi.it).

OBJECTIVES: The aim of this study was to noninvasively define the hemodynamic profile characterizing the early response to tilting.

BACKGROUND: The mechanisms causing orthostatic intolerance have not been fully elucidated. Usually, patients undergoing tilt test are studied in a time-consuming way. Moreover, the test can cause discomfort to the patient and even be potentially hazardous.

METHODS: Nineteen orthostatic intolerant patients (OIP), compared with 22 healthy subjects (HS), performed head-up tilt test while their arterial pressure waveform was noninvasively recorded. We elaborated data using the Pressure Recording Analytical Method to obtain hemodynamic parameters, then analyzing the variables by discriminant analysis.

RESULTS: Compared with HS, OIP showed lower stroke volume index (SVI) values even in baseline conditions associated with higher values of systemic vascular resistance (SVR) and heart rate (HR). From the third minute of the tilted position and until symptoms appeared, patients exhibited lower values of blood pressure (BP) and SVI and higher HR values but no difference in SVR. At termination, patients showed a further significant reduction in BP and SVI and a persistent increase in HR.

CONCLUSIONS: This investigation underlines: 1) the possibility of beat-to-beat monitoring of hemodynamic changes during tilting; 2) the cardiovascular profile of OIP at rest, characterized by lower SVI and higher SVR and HR; 3) the maladaptive response to postural challenge of OIP mainly identifiable in impaired vascular regulation; and 4) the possibility of detecting parameters that enable prompt identification of the positive response to tiltingin these patients, thus guiding the duration of the test.

Abbreviations and Acronyms   BP = blood pressure   DBP = diastolic blood pressure   DICBP = dicrotic blood pressure   HR = heart rate   HS = healthy subjects   OIP = orthostatic intolerant patients   PCM = Pulse Contour Method   PRAM = Pressure Recording Analytical Method   SBP = systolic blood pressure   SVI = stroke volume index   SVR = systemic vascular resistance