Diagnostic Power of Head-Up Tilt Test Enhanced by Autonomic ECG Parameters and Beat-to-Beat Hemodynamic Monitoring

Abstract

Objectives: The head-up tilt test (HUTT) is a well-established diagnostic procedure used to differentiate between the types of syncope. Since its introduction in 1986, the protocol has undergone several refinements aimed at increasing diagnostic accuracy. Despite growing interest in advanced autonomic ECG parameters and beat-to-beat blood pressure monitoring, their integration into routine HUTT protocols remains limited. Methods: In this study, we compared the conventional HUTT protocol using two-minute interval monitoring with an advanced protocol incorporating autonomic ECG parameters-periodic repolarization dynamics (PRD) and deceleration capacity (DC)-as well as continuous beat-to-beat hemodynamic monitoring. Results: The extended protocol improves diagnostic resolution by detecting more pronounced hemodynamic fluctuations, enabling real-time trend analysis, and allowing earlier recognition of impending syncope. The tilt phase was characterized by a significant initial increase in PRD, and patients with syncope showed significantly higher PRD values during the tilt phase (8.14 vs. 3.91 deg², p=0.043). Conclusions: Continuous hemodynamic monitoring during HUTT improves the diagnostic quality by detecting changes at an early stage, thus allowing to anticipate syncope and to clearly identify its etiology. While beat-to-beat blood pressure monitoring is already recommended by current syncope guidelines, we propose the additional evaluation of autonomic ECG parameters as a valuable extension to standard protocols.

Keywords: autonomic function; blood pressure; noninvasive monitoring; syncope; tilt test.

Figure 1

Continuous noninvasive blood pressure monitoring.

Figure 2

Graphical illustration of a representative examination. Depicted is a representative examination for reflex syncope type 2 with manual interval measurements (upper panel) and continuous Finapres NOVA (Finapres medical systems, the Netherlands) measurements (middle and lower panels). Gray vertical lines illustrate the tilting time point (after 15 min); black vertical arrows indicate the time point of syncope. BP, blood pressure; sys, systolic; dia, diastolic; HR, heart rate; man, manual; FP, finapres.