Quantitative Complexity Theory Used in the Prediction of Head-Up Tilt Testing Outcome

Background. Head-up tilt testing (HUTT), a well-established tool in the diagnosis of vasovagal syncope, is time-consuming, and every provoked vasovagal reaction may result in consolidating the reflex mechanism. Therefore, identification of parameters that could shorten the duration of HUTT and prevent fainting is desirable. Quantitative complexity theory (QCT) may provide holistic information on the cardiovascular reaction in HUTT. The aim of the present article was to evaluate the prognostic value of complexity in comparison with traditional haemodynamic parameters (HR and BP) in predicting the HUTT outcome. Methods. Eighty-one healthy volunteers (74 men; mean age: 37.8 years) were included in this retrospective analysis of data collected within the project realized in Department of Cardiology and Internal Diseases, Military Institute of Medicine between January 2012 and October 2014. The subjects underwent HUTT, with beat-to-beat haemodynamic monitoring with a Niccomo™. The chosen haemodynamic parameters (including BP, HR, stroke volume, cardiac output, systemic vascular resistance) have been used in complexity analysis. Results. HUTT was positive in 54 (66.7%) study participants. The values of complexity were already higher in fainting subjects than those were in nonfainting ones 300 s before HUTT termination (HUTT_end), with a significant upward trend starting 150 s before (pre)syncope. An area under the curve (AUC) over 0.700 was observed for complexity from 120 s before HUTT_end, with a sensitivity of 63% and specificity of 78% at this time point. The prognostic value of complexity was superior to that of the HR and mean arterial pressure (MAP). Conclusions. Complexity has been shown to be a sensitive marker of cardiovascular haemodynamic response to orthostatic stress and proved to be superior over HR and BP in predicting HUTT outcomes.

Comparison of the finger plethysmography derived stroke volumes by Nexfin CO Trek and suprasternal aortic Doppler derived stroke volume measurements in adults with myalgic encephalomyelitis/chronic fatigue syndrome and in healthy controls

BACKGROUND: Finger plethysmography derived stroke volumes are frequently measured during tilt table testing. There are two algorithms to determine stroke volumes: Modelflow and NexfinCO Trek. Most tilt studies used Modelflow, while there are differences between the two algorithms. OBJECTIVE: To compare stroke volume indices by Nexfin CO Trek (SVINexfinCOTrek) with suprasternal Doppler derived SVI (SVIDoppler) in healthy controls (HC) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) patients during tilt testing. These patients may have a large SVI decrease during the tilt enabling a large range of SVI to be studied. METHODS: One hundred and fifty-four patients and 39 HC with a normal tilt test were included. Supine and end-tilt SVIDoppler and SVINexfinCOTrek were compared using the Bland-Altman analysis. Also, the effect of calibrating supine SVINexfinCOTrek to SVIDoppler was studied RESULTS: Supine and end-tilt SVINexfinCOTrek were significantly higher than SVIDoppler: both P< 0.005. Bias, limits of agreement, and percent error (PE) were high with PE’s between 37 and 43%. The calibration procedure resulted in an acceptable variance with a PE of 29%. CONCLUSIONS: SVINexfinCOTrek overestimates stroke volumes compared to SVIDoppler, leading to high PE’s. Calibration reduced variance to an acceptable level, allowing SVINexfinCOTrek to be used for assessment of SVI changes during tilt testing

Tilt testing remains a valuable asset

Head-up tilt test (TT) has been used for &gt;50 years to study heart rate/blood pressure adaptation to positional changes, to model responses to haemorrhage, to assess orthostatic hypotension, and to evaluate haemodynamic and neuroendocrine responses in congestive heart failure, autonomic dysfunction, and hypertension. During these studies, some subjects experienced syncope due to vasovagal reflex. As a result, tilt testing was incorporated into clinical assessment of syncope when the origin was unknown. Subsequently, clinical experience supports the diagnostic value of TT. This is highlighted in evidence-based professional practice guidelines, which provide advice for TT methodology and interpretation, while concurrently identifying its limitations. Thus, TT remains a valuable clinical asset, one that has added importantly to the appreciation of pathophysiology of syncope/collapse and, thereby, has improved care of syncopal patients.

Age-related tilt test responses in patients with suspected reflex syncope

Aims Tilt testing (TT) is recognized to be a valuable contribution to the diagnosis and the pathophysiology of vasovagal syncope (VVS). This study aimed to assess the influence of age on TT responses by examination of a large patient cohort. Methods and results Retrospective data from three experienced European Syncope Units were merged to include 5236 patients investigated for suspected VVS by the Italian TT protocol. Tilt testing-positivity rates and haemodynamics were analysed across age-decade subgroups. Of 5236 investigated patients, 3129 (60%) had a positive TT. Cardioinhibitory responses accounted for 16.5% of positive tests and were more common in younger patients, decreasing from the age of 50–59 years. Vasodepressor (VD) responses accounted for 24.4% of positive tests and prevailed in older patients, starting from the age of 50–59. Mixed responses (59.1% of cases) declined slightly with increasing age. Overall, TT positivity showed a similar age-related trend (P = 0.0001) and was significantly related to baseline systolic blood pressure (P &lt; 0.001). Tilt testing was positive during passive phase in 18% and during nitroglycerine (TNG)-potentiated phase in 82% of cases. Positivity rate of passive phase declined with age (P = 0.001), whereas positivity rate during TNG remained quite stable. The prevalence of cardioinhibitory and VD responses was similar during passive and TNG-potentiated TT, when age-adjusted. Conclusions Age significantly impacts the haemodynamic pattern of TT responses, starting from the age of 50. Conversely, TT phase—passive or TNG-potentiated—does not significantly influence the type of response, when age-adjusted. Vagal hyperactivity dominates in younger patients, older patients show tendency to vasodepression.

The Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients with Joint Hypermobility Show Larger Cerebral Blood Flow Reductions during Orthostatic Stress Testing Than Patients without Hypermobility: A Case Control Study

Aims: An abnormal reduction in cerebral blood flow (CBF) during orthostatic stress is common in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), a condition with more prevalent joint hypermobility than in the healthy population. As one of proposed underlying mechanisms of orthostatic intolerance in hypermobile patients is vessel laxity, reducing the normal return of blood to the heart during orthostatic stress, we hypothesized that the CBF reduction during tilt-testing would be larger in ME/CFS patients with joint hypermobility than in patients without hypermobility. Methods: In this case-control study, 100 female ME/CFS cases with joint hypermobility, who had undergone tilt-testing with CBF measurements, were compared to 100 female ME/CFS patients without joint hypermobility, matched by age and disease duration. Results: No differences in baseline characteristics were found between groups. The hypermobile patients had significantly more postural orthostatic tachycardia syndrome (POTS) during tilt testing than the non-hypermobile ones. Compared to supine CBF, the degree of CBF reduction during the tilt was significantly larger in hypermobile cases than in the non-hypermobile controls: -32 (6)% vs -23 (7)% (p<0.0001) The larger CBF reduction in hypermobile patients was not only present in POTS patients: -33 (6)% vs -24 (4)%, but also in patients with a normal heart rate and blood pressure response to tilt testing: -31 (6)% vs -22 (9)%: (both p<0.0001). Conclusions: ME/CFS patients with joint hypermobility syndromes have larger CBF reductions during orthostatic stress testing than patients without hypermobility. This larger CBF reduction is independent of the heart rate and blood pressure results of the orthostatic stress test.

Interrelationships between Survival, Sex, and Blood Pressure in Patients with Multiple System Atrophy

Objective: The aim of this study is to estimate survival among patients with multiple system atrophy-parkinsonian type (MSA-P) or cerebellar type MSA (MSA-C) in relation to blood pressure (BP) measurements, by sex. Methods: A cohort of 99 MSA patients was studied retrospectively. Their BP measurements were obtained during prolonged (40 min, vertical position) drug-free tilt testing. We used K-M survival curves and Cox regression to calculate adjusted (to age of onset) hazard ratios (HRs) of BP measurements on time to death by MSA subtype and sex. Results: Fifty-two MSA patients were males and 47 were females. Sixty-three of them had MSA-P and 36 had MSA-C. The mean age at motor symptom onset was 61.1 ± 10.4 years, and mean disease duration at the time of BP assessment was 8.0 ± 4.7 years. The 2 study groups (MSA-P and MSA-C) did not differ significantly in age at MSA onset, sex ratio, or disease duration. Survival time did not differ between the groups {medians: 12 years (95% confidence interval [CI]: 8–28) and 10 years (95% CI: 8–13), respectively}. The MSA-P group showed a trend towards better survival for males (log-rank p = 0.0925). The maximal diastolic orthostatic BP decline during tilt testing had a borderline positive association with death risk among MSA-C males (adjusted HR = 1.18, p = 0.0665), and systolic BP after 10 min in a supine position had a significant positive association with death risk among MSA-P males (adjusted HR = 1.06, p = 0.0354). Conclusions: The findings of a sex-based difference in the effect of BP on death risk may be important for adjusting the therapeutic approach to MSA patients.