Assessment of electrocardiogram abnormality and associated factors among apparently healthy adult type 2 diabetic patients on follow-up at Jimma Medical Center, Southwest Ethiopia: Cross-sectional study

An Institutional based cross-sectional study was conducted from April, 1 to May 30, 2019, at Jimma Medical Center (JMC) which is located in Oromia Regional State, 350 km southwest of Addis Ababa. JMC is the referral teaching hospital giving health services to about 15 million people in the South West of Ethiopia. Diabetic patients getting follow-up service in the diabetic clinic are usually appointed in one to two months regularly.

All adult type 2 diabetic patients who were on follow-up at diabetic clinics at JMC were a source population. The study population was all randomly selected adult type 2 diabetic patients on follow-up at JMC during the study period and who fulfill the eligibility criteria. All type 2 diabetic patients aged 18 years and above, who had no prior diagnosis of cardiovascular diseases were included in this study. Type 2 diabetic patients who were mentally impaired and unable to give information, or had diagnosed CVDs before the onset of diabetes mellitus were excluded. Type 2 diabetic patients with concomitant diseases like chronic liver disease, kidney disease, thyroid diseases, etc., as well as type 2 diabetic with acute complications diabetes ketoacidosis, or hyperosmolar hyperglycemic state, were also excluded.

The sample size was determined using a single population proportion formula by considering the following assumptions: p = 50% since no similar study done in Ethiopia, the margin of error = 5% and 95% confidence level \(n = \frac{{\left( {z{\raise0.7ex\hbox{$\alpha $} \!\mathord{\left/ {\vphantom {\alpha 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}} \right)^{2} p\left( {1 - p} \right)}}{{d^{2} }} = \frac{{(1.96)^{2} \times 0.5 \times 0.5}}{{(0.05)^{2} }} = 384.\) From chronic follow-up record data, the total number of type 2 diabetic patients on follow-up at JMC in 2018 was 1685. Since the source population is less than 10,000 applying the formula for finite population correction the final sample size was calculated as follows.

\(nf = \frac{n}{{\{ 1 + (n/N\} }} = \frac{{384}}{{\{ 1 + (384/1685)\} }} = 313.\) Adding 10% non-response rate = 313 + 31 = 344.

World health organization (WHO) stepwise approach was employed for collecting the risks of CVDs among type 2 diabetic patients during entry [21]. The questionnaire was translated from English to Afan Oromo and back to English to assure its consistency in a blinded manner. A pre-test was done on 5% of the total sample size at Shanan Gibe Hospital before the actual data collection to ensure clarity, understandability, and completeness. Correction and modification on grammar, sequences, and timing were made based on the result of the pre-test before the start of actual data collection. Finally, the Afan Oromo version was used to collect data. Data collection was conducted through a face-to-face interview by trained data collectors using semi-structured questionnaires. The information related to the medical condition was reviewed from patients’ medical charts. The questionnaires were checked for completeness by supervisors and principal investigators every day.

The dependent variable of the study was ECG abnormality. The independent variables were sociodemographic factors (age, sex, educational status, occupation, and place of residence), factors related to a medical condition (duration of treatment and glycemic control), behavioral factors (physical activity, alcohol, tobacco, and khat use), nutritional factors (the type of cooking oil and fruit and vegetable intake), and factors related with body composition (weight, height, body mass index (BMI), waist circumference (WC), blood pressure (BP), and waist to hip ratio (WHR)).

Normal sinus rhythm A regular heart rate between 50 and 100 beats per minute [22] with normal p waves, PR interval, QRS complex, T waves, and p waves preceding each QRS complex.

The measurements of blood pressure, anthropometry (weight, height, waist circumference, and hip circumferences), fasting blood glucose level, and recording of electrocardiography were made according to the respective guidelines. Accordingly, the measurements of anthropometry were measured according to WHO guidelines [23] while BP was measured according to the European society of hypertension recommendation [24]. Fasting blood sugar (FBS) was measured according to Standard Operating Procedures Clinical and Translational Research Center [25] and ECG was recorded according to the standard manual for the Minnesota ECG criteria [22]. The height was measured to the nearest 0.5 cm with a stadiometer (Prestige Tokyo, Japan) as participants stand vertical with no shoes or headwear with their back against the stadiometer, heels together and eyes focused forward. The weight was measured to the nearest 0.1 kg while the participant wore light clothing with a digital weighing scale (Tanita Corporation, Tokyo, Japan) and checked daily with a known weight. WC was measured in a standing position using a non-stretchable measuring tape meter at the midpoint between the costal margin and iliac crests at the end of expiration to the nearest centimeter. HC was measured as the maximum circumference at the level of the greater trochanter (the widest portion of the hip) on both sides using a non-stretchable measuring tape meter. FBS was done with a simple finger prick using a digital glucometer. BP was measured three times in sitting position from the non-dominant arm at heart level using an aneroid sphygmomanometer (Yton sphygmomanometer, Italy) after the participant rested for 5 min before taking the measurement and 3 min before repeating the subsequent measurements, and the average was used for analysis. The resting 12 lead ECGs were obtained after a 10-min rest, with 10 mm/mV amplitude and paper speed of 25 mm/s rates with standard lead positions in a supine position using YORK” 12 lead Electrocardiography (India). The recorded ECG was coded according to the Minnesota code and manually read by two cardiologists in a blinded manner having no information about the patients. The suggested procedure for electrocardiogram was followed in the reference to the standard manual for the Minnesota ECG criteria [22].

The data were entered into Epi-data version 4.0.2. and exported to SPSS version 21 for analysis after checking for completeness. The exported data were explored to check outliers and missing values. Descriptive statistics like frequencies, percentages, mean, and standard deviations were carried out. Cross-tabulations and binary variable analyses were performed to select variables for multivariable analysis. The variables with a p value < 0.25 in the bivariable analysis were taken as candidates for multivariable analysis. Finally, multivariable logistic regression analysis was done using backward selection and the variables with a p value of less than 0.05 were taken as statistically significant determinants of abnormality of ECG. The odds ratio with its 95% CI was used to show the degree of association and estimation between the independent and the outcome variables.

A total of 344 T2DM patients were interviewed and underwent electrocardiography giving a response rate of 100%. The majority of 210 (61%) of the respondents were males. The mean age of the respondents was 53.34 ± 11.07 years with a minimum age of 18 and a maximum of 80 years. More than half, 202 (58.7%) of the respondents were in the age group of 51–70 years. Farmer respondents were 109 (31.7%) while merchants and government employees accounted for 83 and 84 (24%) respectively. More than half 199 (57.8%) of the respondents were urban dwellers (Table 1).

The majority of the respondents, 333 (96.8%) and 319 (92.7%) were nonsmokers and non-alcohol users respectively. Most of the respondents 331 (96.2%) were involved in physical activity less than 150 min of moderate or 75 min of vigorous physical activity per week (less than 600 metabolic equivalents of energy per week). Non-khat chewers accounted for 304 (88.4%) of the respondents.

Most of the respondents 339 (98.5%) were using fruits and vegetables below five servings per day. Five servings of fruit and vegetables per day (equivalent to 400 g of fruits and vegetables) while solid oil users were 235 (68.3%).

An average systolic blood pressure (SBP) was 121.20 ± 7.34 mmHg while the average diastolic blood pressure (DBP) was 77.85 ± 4.15 mmHg (Table 2).

The mean fasting blood glucose was 123.65 ± 17.34 mg/dl. From the total respondents, 210 (61%) had a fasting blood sugar within a normal range whereas hyperglycemia and hypoglycemia were 123 (35.8%) and 11 (3.2%) respectively. The mean duration of diabetes was 7.31 ± 4.54 years with a minimum duration of 1 year and a maximum of 19 years. Most of the respondents 109 (31.7%) and 102 (29.7%) had a diabetes duration of 2–5 and 5–10 years respectively (Fig. 1).

The majority of the respondents 209 (61%) had at least one electrocardiogram abnormality (Fig. 2). ECG abnormality was 101 (29.4%) among participants with abnormal body weight 21 (6.1%) among underweight, 57 (16.6%) among overweight, 23 (6.7%) among obese), 136 (39.5%) in high-risk WC, 69 (20.1%) in DM duration > 10 years, 158 (45.9%) in Solid oil users and 109 (31.7) urban dwellers.