Aspects & challenges - Approaches & tools
Head-up-tilt testing (HUTT) and autonomic function testing are essential diagnostic procedures in syncope assessment. With the advent of unique innovative methods to noninvasively monitor beat-to-beat blood pressure, cardiac output, total peripheral resistance as well as autonomic regulation, highly efficient tools to assess cardiovascular and autonomic function have become state-of-the-art for improved diagnosis of patients.
Over the last few decades experts around the world continue to explore the mechanisms of syncope describing different approaches, concepts and factors that might explain what is going on in a fainting patient. Although being a common disease the pathophysiology of syncope is still a rich research topic1 and its “diagnosis and management remain challenging tasks in medical practice.”2
While the approach to diagnose syncope is most often the same for pediatric, adult and geriatric patients1, it is meanwhile well-known that the circulatory adjustment to the stress of a postural change varies markedly over age.2
Recent studies show that considering the full set of continuous cardiovascular parameters is required to enhance the diagnosis and provide age-tailored therapies for syncope:
- Wijnen et al.4 showed that hemodynamic responses are age-related and that the course of syncope definitely differs between young and old patients.
- Gonzales-Hermosillo et al.7 studied young patients in order to compare the hemodynamic and autonomic responses of healthy volunteers with syncope patients during head-up tilt, analyzing heart rate variability and beat-to-beat blood pressure.
Nevertheless, in recent literature the head-up tilt test has been considered a long-term procedure with limited specificity and sensitivity3 to detect all the different mechanisms which are responsible for syncope. There is a claim for “new, more advanced methods for syncope analysis”3 that help to better understand the “complex responses provoked by the HUTT.”3 The authors agree that additional or different approaches and methods might be required.1,2,7,8
Wu et al. investigated the clinical relevance of carotid sinus hypersensitivity as a possible approach and predictor of syncope and autonomic dysfunctions.2
Ruska et al. from the Zagreb Medical University evaluated the COMPASS-31 questionnaire as a supplementary method for HUTT for objective testing of the autonomic nervous system. This method proved “a valuable screening tool to assess symptoms of autonomic dysfunctions as it is associated with impaired ANS.”8
Apart from the evaluation of linear patterns, such as hemodynamic and autonomic parameters, approaches describing the underlying dynamics of cardiovascular responses to syncope might be required.
Makowiec et al. have investigated the so-called multistructure index (MI) describing the asymmetric features of cardiovascular interactions. Differences have been found in the organization of the homeostatic state between healthy people and vasovagal patients.”1
Buszko et al. from the Medical Universities in Warsaw studied vasovagal syndrome occurrence and proposed another nonlinear approach based on differences in sample entropy and even stroke volume as “measures of irregularity.”7
Most studies claim a need for further investigations and suppose that it might finally be a combination of many approaches which has the potential to fully elucidate the complex physiological mechanisms of syncope and which could become the gold standard.
However, real improvement of the diagnosis and treatment is only possible by taking into account the complete set of aspects including the widest possible variety of hemodynamic parameters.
The Task Force® Monitor by CNSystems has proven as commonly used diagnostic tool for the assessment of neuro-cardiogenic syncope8 which “calculates and registers biological signals in a completely reliable and non-invasive way, in the beat-to-beat mode, this being its main advantage.”9
It is an easy to use tool for currently applied protocols and allows for recording and exporting a full set of hemodynamic and autonomic parameters, which is a solid basis for further research studies.
1 Makowiec D, Graff B, Struzik ZR (2017) Multistructure index characterization of heart rate and systolic blood pressure reveals precursory signs of syncope. Scientific Reports 7(1):419.
2 Wu TC, Hachul DT, Darrieux FC, Scanavacca MI (2018) Carotid Sinus Massage in Syncope Evaluation: A Nonspecific and Dubious Diagnostic Method. Arquivos Brasileiros de Cardiologia. Available from doi.org/10.5935/abc.20180114.
3 Peeters SY, Hoek AE, Mollink SM, Huff JS (2014) Syncope: risk stratification and clinical decision making. Emergency Medicine Practice 16(4):1-22. Available from www.ncbi.nlm.nih.gov/pubmed/25105200
4 Dambrink JH and Wieling W (1987) Circulatory response to postural change in healthy male subjects in relation to age. Clinical Science 72(3): 335–41. Available from www.ncbi.nlm.nih.gov/pubmed/3816087
5 van Wijnen VK, Finucane C, Harms MPM, Nolan H, Freeman, RL, Westerhof BE, Wieling W et al. (2017) Noninvasive beat-to-beat finger arterial pressure monitoringduringorthostasis: a comprehensivereview of normal and abnormal responses at different ages. Journal of Internal Medicine 282(6):468–483. Available from doi.org/10.1111/joim.12636
6 González-Hermosillo A, Sierra-Beltrán M, López-Peña U, Kostin A, Hernández-Pacheco G, Lerma C (2018) Cardiovascular and Cerebral Hemodynamics in Asymptomatic Healthy Subjects With/Without Abnormal Head-up Tilt Test Versus Recurrent Fainters. J Clin Neurophysiol 35(1):77-83. Available from doi: 10.1097/WNP.0000000000000430.
7 Buszko K, Piatkowska A, Kozluk E, Fabiszak T, Opolski G. (2018) The complexity of hemodynamic response to the tilt test with and without nitroglycerine provocation in patients with vasovagal syncope. Scientific Reports 8(1):14554. Available from doi.org/10.1038/s41598-018-32718-2.
8 Ruška B, Pavicic T, Pavlovic I, Junakovic A, Adamec I, Crnošija L, Krbot Skoric M, Habek M (2018) Performance of the COMPASS-31 questionnaire with regard to autonomic nervous system testing results and medication use: a prospective study in a real-life setting. Neurol Sci. 39(12):2079-2084. Available from doi: 10.1007/s10072-018-3542-8.
9 Zawadka-Kunikowska M, Slomko J, Tafil-Klawe M, Klawe JJ, Cudnoch-Jedrzejewska A, Newton JL, Zalewski P (2017) Role of peripheral vascular resistance as an indicator of cardiovascular abnormalities in patients with Parkinson's disease. Clin Exp Pharmacol Physiol. 44(11):1089-1098. Available from doi: 10.1111/1440-1681.12809.