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Table of Content - Volume 9 Issue 1 - Januray 2018
A cross sectional study on the assessment of cardiac autonomic dysfunctions among patients with type 2 diabetes mellitus
Katta Subraya Prakash Rao1, Saladi Mahesh2*
1Associate Professor, 2Post Graduate, Department of General Medicine, K.V.G. Medical College, Kurunjibagh. Sullia, D. K. Karnataka, INDIA.
Abstract Background: Neuropathy is a common complication of diabetes mellitus. It may affect both peripheral and autonomic nervous system. The objective of the present study was to investigate the prevalence of cardiac autonomic neuropathy in patients with Type 2 Diabetes Mellitus by using simple bedside tests and also to study its relationship with certain complications of diabetes. Materials and methods: The present study was done among 100 patients of Type 2 Diabetes Mellitus attending Medicine Outpatient department between October 2016 and October 2018. Results: Abnormal E: I ratio was noticed in 31 patients while the 30:15 ratio was found to be abnormal in 42 patients. Postural hypotension was observed in only 8% patients. QTc interval was prolonged in 42% of patients. The prevalence of cardiac autonomic neuropathy was 65%. The association between the presence of autonomic neuropathy and peripheral neuropathy, retinopathy and nephropathy were statistically significant. Conclusion: The prevalence of cardiac autonomic neuropathy was 65%. There was a significant statistical association between autonomic neuropathy and peripheral neuropathy, retinopathy and nephropathy. Key Word: Cardiac autonomic neuropathy, Diabetes Mellitus, QTc interval
INTRODUCTION The world today is witnessing a pandemic of diabetes mellitus1. The WHO report suggests that over 19% of the world’s diabetic population currently resides in India which translates to over 35 million and these numbers are projected to increase. This rising trend predicts a significant health burden due to diabetes and its complications in India2, 3, 4. Diabetes mellitus has been often associated with a wide range of complications like cardiovascular diseases, nephropathy, retinopathy and neuropathy, all of which can result in morbidity, disability and mortality5. Autonomic neuropathy is one of the least recognized or understood, dreaded and troublesome complications of diabetes, which can cast a serious negative impact on the quality of life of a diabetic patient6. The diabetic autonomic neuropathy tends to affect the functioning of multiple systems – cardiovascular, urogenital, gastrointestinal, pupillomotor, thermoregulatory and sudomotor, resulting in a significant proportion of morbidity and mortality associated with the disease7. Poor glycemic control, long duration of diabetes, increasing age, female gender and smoking have been identified as the potential risk factors for diabetic autonomic neuropathy and subsequent cardiac autonomic neuropathy6. Evidence suggests that almost 25-50% of patients with diabetic autonomic neuropath die within 5-10 years of diagnosis and this itself is a significant cause for augmenting the medical cost for patients and family members8, 9. The present study has been conducted with an objective to estimate the prevalence of cardiac autonomic neuropathy among the diabetics in a rural area of Karnataka.
MATERIALS AND METHODS A cross sectional study was conducted at a tertiary care teaching hospital at Karnataka from October 2016 to October 2018. The study was conducted among 100 Type 2 Diabetes Mellitus patients who were selected by systematic random sampling technique. Institutional ethical committee clearance was obtained and a written informed consent was also obtained from the participants before the study. Each of the study participants were subjected to thorough clinical examination and anthropometric measurements. In addition, a routine ECG was done to detect any potential cardiac complication so that high risk subjects can be excluded from the study. The following parameters were checked for: Heart rate variation during deep breathing: The patients were asked to sit quietly and take six deep breaths (10s/breath) for total of 1 minute. Continuous ECG was recorded throughout the period and onset of each inspiration and expiration was marked. The maximum and minimum RR intervals during each breathing cycle was measured and converted to beats/minute. Further, the estimates were expressed in terms of mean to indicate difference between maximum and minimum heart rates for the 6 measured cycles in beats/ minute. The variation of heart rate (HR) during inspiration and expiration of less than 10 beats/ minute is accepted as cardiac autonomic neuropathy (CAN) 10. Blood Pressure response to sudden standing (Postural hypotension): The patients BP were initially measured while lying down quietly and again when he stood up. The postural fall after 2 minutes in BP was taken as difference between SBP lying and SBP standing. A difference of more than 30 mmHg is defined as the presence of postural hypotension10. QTc interval: QT interval is measured on an ECG recording at rest and corrected for the cardiac cycle length (QTc). It is calculated by the equation of Bazett: QTc = QT/√R-R. A QTc interval more than 440 millisecond is considered prolonged and an indicator of CAN11. Inclusion Criteria: All Type 2 Diabetes Mellitus patients with history of onset of disease before 1 year and willing to participate in the study. Exclusion Criteria: Those with history of hypertension, history or electrocardiography (ECG) evidence of coronary artery disease, stroke/transient ischemic attack (TIA), electrolyte imbalance like hypokalemia or hypocalcemia, history of heart failure, renal dysfunction, hypothyroidism, and drugs affecting autonomic tone or QT interval were excluded. Statistical analysis: The data was entered in Microsoft Office Excel 2007 and IBM SPSS version 17 was used for analysis. Frequencies and percentages were used for describing categorical variables. For continuous variables, Mean and standard deviation were used. Inferential statistical tests like Chi square test and Students t test were used to test statistical significance.
RESULTS A total of 100 patients with Type 2 diabetes mellitus patients were examined and investigated for features of diabetic autonomic neuropathy. The baseline characteristics of the study population are tabulated in Table 1. It can be seen that the maximum number of patients (57%) belonged to the age group 50 – 59 years followed by people in the age group 45 – 49 years (19%). Only 9% of the study population belonged to the above 60 years age group. 54% of the study population was male. 59% of the study population suffered from diabetes for more than five years. Among the study population, 46% of them had peripheral neuropathy, 42% had retinopathy and 6% had nephropathy.
Table 1: Baseline characteristics of the study population
Patients were interrogated for symptoms of autonomic neuropathy and it was found that 22% had nocturnal diarrhea, 19% had postural giddiness and 15% had erectile dysfunction as seen in Table 2. Patients were also subjected to various tests to identify cardiac autonomic neuropathy as seen in Table 3.
Table 2: Incidence Of Selected Symptoms Of Autonomic Neuropathy In The Study Subjects
Table 3: Distribution Of Patients With Cardiac Autonomic Neuropathy Based On Various Tests
42% of them had a prolonged QTc interval and abnormal heart rate response to standing. 31% of the patients had an abnormal E: I ratio and 13% had orthostatic hypotension. QTc intervals in patients with and without diabetic neuropathy were tabulated in Table 4 and there was a statistically significant difference that was observed between the two groups.
Table 4: Relationship Between Qtc Interval And Diabetic Autonomic Neuropathy
Table 5: Relationship Between Diabetic Complications And Autonomic Neuropathy
Table 5 shows the relationship between diabetic complications and autonomic neuropathy. It was seen that the patients with complications of diabetic neuropathy, retinopathy and nephropathy had a more chance to have diabetic autonomic neuropathy when compared to those without complications.
DISCUSSION The present study was done among 100 patients of Type 2 Diabetes Mellitus attending Medicine Outpatient department between October 2016 and October 2018. The study was conducted with the aim of investigating the prevalence of cardiac autonomic neuropathy in patients with Type 2 Diabetes Mellitus by using simple bedside tests and also to study its relationship with certain complications of diabetes. Diabetic neuropathy is a serious and a very common complication of diabetes and the incidence ranges from 10 to 90%12. The prevalence of autonomic neuropathy detected by various tests ranges between 40 and 60%13. In the present study, the prevalence of autonomic neuropathy was 65%. The age of the study participants ranged between 40 and 70 years. Majority of the participants were in the age group of 50-59 years age group. This is in contrast to a study done by Birajdar SV et al14 where the commonest age group was reported to be 21 -30 and 41-50 years with 20% of the study population in this age group. There were 54 males and 46 females with a male: female ratio of 1.17:1. It was noticed that 59% of the patients had diabetes for more than 5 years which was in contrast to a study done by Birajdar SV et al14 where there were 22% of patients with more than 5 years history of diabetes mellitus. The incidence of peripheral neuropathy, retinopathy and nephropathy in the present study were 46%, 42% and 6% respectively. Higher incidence was reported in a study done by Patel HS et al15 where 62.35% had neuropathy and 24.36% had retinopathy. High incidence was also reported by Kudrimoti NB16 where peripheral neuropathy was 62.5%, retinopathy was 31.4% and nephropathy in 15.7%. Heart rate variations during deep breathing are a sensitive marker of autonomic dysfunction17. Abnormal E: I ratio was observed in 31% of patients which is different from a study done by Kudrimoti et al16 where the abnormality was observed in 22.9% of the patients. Patnaik et al18 reported a very high incidence of 85.71%. The heart rate response to standing was abnormal in 42% of patients. Ewing et al19 reported a higher incidence of 60% while in a study done by John L et al20 it was 46.6%. Postural hypotension was found in 13% of the patients. John L et al20 observed postural hypotension in 12% of the patients whereas only 6% had it in a study done by Sharma et al21. In the present study, it was observed that parasympathetic involvement was much more than sympathetic involvement. In the study done by Ewing et al19, parasympathetic involvement was observed in 55.73% of patients and sympathetic dysfunction in 26.33%. The symptoms of autonomic neuropathy were observed in the present study and it was seen that diarrhoea was seen in 22% of patients, giddiness in 19%, erectile dysfunction in 15% and gastroparesis and sweating abnormality in 5% and 4% respectively. Study done by Pillai and Madhavan12 showed postural giddiness in 48.5% of patients and erectile dysfunction in 60% of the males whereas gastroparesis was seen in 9.1%, nocturnal diarrhoea in 3% and sweating abnormality in 6.1%. The complications of diabetes like neuropathy, nephropathy and retinopathy showed significant increase with diabetic autonomic neuropathy. Ziegler et al22 confirms that autonomic neuropathy correlates well with the presence of diabetic complications. QTc mean in patients with diabetic autonomic neuropathy and without neuropathy was 413 msec and 393 msec respectively. The difference between the group with autonomic neuropathy and that with no autonomic neuropathy group was statistically significant. Similarly the difference in QTc max was also statistically significant.
CONCLUSION In the present study, cardiac autonomic neuropathy was found in 65% of the patients. Parasympathetic involvement was more than sympathetic dysfunction. There was significnat statistical association between diabetic autonomic neuropathy and diabetic neuropathy, retinopathy and nephropathy. There is an increase in resting heart rate and QTc interval. QTc max was correlating well with severity of autonomic neuropathy. REFERENCES
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