Heart Rate Variability (HRV) in Prediabetics - ACross Sectional Comparative Study in North India

Background: Cardiac autonomic dysfunction (CAD) and neuropathy is common in diabetes mellitus but theabnormalities in Autonomic nervous system (ANS) and the influence of altered glycaemic indices oncardiovascular parameters by using HRV has not been elucidated in prediabetics. Hence, the present studywas aimed to measure HRV and to find out the association, if any, between the parameters of HRV andglycaemic index in Prediabetics.Methods: Recording of short term HRV in thirty prediabetics and thirty apparently healthy controls of eithersex in the age group of 40 to 65 years were done. The subjects were enrolled as per American DiabetesAssociation (ADA) criteria on the basis of their glycaemic indices viz: Fasting blood sugar (FBS), 2h Oralglucose tolerance test (OGTT) and Glycated haemoglobin (HbA1c).Result: Prediabetic subjects showed a significant decrease (p=0.007) in SDNN (Time Domain parameter ofHRV) when compared with the control group, whereas the RMSSD and other frequency domain parametersof HRV did not show any significant difference in the two groups. However, the correlation analysis betweenvarious parameters of HRV and glycaemic indices showed a significant negative association.Conclusion: A significant decrease in SDNN along with significant negative association between HRVparameters and glycaemic indices indicates towards a decrease in parasympathetic activity of cardiacautonomic function and hence the possibility of initiation of CAD in Prediabetic stage itself.

Cognitive Function Assessment In Mild To Moderate Copd Patients Through P300, Erp Study

Event-related potentials (ERPs) provide a non-invasive method of studying ain neural activity, with P300 wave components reflecting the speed of cognitive processes. In our study we primarily focused on finding cognitive impairment in the initial stage of the Chronic obstructive pulmonary disease (COPD) through latency and amplitude study of P300 wave. We enrolled equal number (n = 35) of COPD cases and healthy controls. Mean value of Latency at Fz, Cz, Pz was significantly decreased in cases as compared to control group (p = 0.007, p = 0.001, p = 0.006 respectively). Similarly, mean averaged latency was also decreased in COPD vs controls (p = 0.008). Furthermore, a significant positive correlation between MEF25-75% and amplitude at Cz in the COPD cases (r = 0.3534, p = 0.037) was observed. The results obtained in our study suggests that the cognitive dysfunction is present even in mild to moderate COPD patients. The positive association between the spirometric parameters and P300 variables obtained in our study also suggests that with deterioration in lung functions there is decline in cognition.

Post-task changes in visual P300 and their reversibility through brief hyperventilation.

Long hours of continuous, mental task reportedly increase the average auditory P3 latency of the normal subjects significantly, a change that is thought to be related to mental fatigue. We have tried out several protocols of varying task difficulty and duration in an effort to study the onset of the assumed fatigue-related changes. The present study shows that changes in visual event-related potential occur in less than two minutes if the task is sufficiently rigorous. The changes occur both in latency and in amplitude. Moreover, the changes are reversible with a brief (30 second) period of hyperventilation. The changes were most marked at Fz. Following the difficult task, the P3 amplitude at Fz decreased from 8.588 micro/V +/- 0.966 to 5.800 microV +/- 0.795 and the P3 latency increased from 368 +/- 4 ms to 380 +/- 3. Following hyperventilation, the P3 amplitude at Fz reverted to 8.457 +/- 5 and the P3 latency reverted to 371 +/- 5 ms. These observations call for further investigations on the cause of the post-task changes and their quick reversibility.

Post-task P3-changes following a brief, rigorous visual task indicate individual differences in the task-specific ability.

The P3 latency in an auditory oddball ERP paradigm is known to get prolonged after a few hours of mental task. The present study shows that it takes merely a few minutes of challenging visual mental activity to produce significant changes in P3 latency in the visual oddball ERP paradigm. However, the mental activity results in a shortening of P3-latency almost as often as it results in its prolongation. Similarly, the post-task P3 amplitude is higher or lower with nearly equal incidences. Following the task, the reaction time shortens as often as it prolongs. It seems that the P3 changes and their variations through electrode sites signify individual differences in the amount and extent of additional neuronal resources tapped by the subject in coping with the challenging task, and that it leaves an aftereffect for several minutes after the mental workload is withdrawn. These aftereffects get indexed in the P3 wave characteristics of a much simpler ERP paradigm with more change occurring in the better performers. In the clinical context, these observations raise doubts about the diagnostic value of P3 latency or amplitude without knowledge of the immediate history of mental workload.

Correlation of autonomic indices with thyroid status.

The autonomic status in female thyroid patients was compared with healthy, age matched normal females taken as controls. The patients (29 +/- 7 years) were categorised into two groups: hyperthyroid and hypothyroid. The valsalva manoeuvre, standing to lying ratio (S/L ratio) and immediate heart rate response to standing (30:15 ratio) to assess the parasympathetic status while the galvanic skin response (GSR) was recorded to assess the sympathetic status. Statistical analysis was done using Student's t-test for comparing between the different groups and regression analysis were performed between autonomic indices and thyroid hormone levels. Although the mean values were not significantly different in hypothyroid and hyperthyroid patients, yet the correlation between autonomic function and thyroid hormone levels indicates a statistically significant difference (P-value<0.05), with the S/L ratio. The correlation was negative for log [T3] and log [T4], while it was positive for log [TSH]. This indicates that there is decreased parasympathetic activity with increased T3 and T4, which is in agreement earlier reports. The GSR, which is one of the measures of sympathetic activity, was found to be unaffected.