Patients attending the internal Medicine service of the Istanbul Naval Hospital, who were diagnosed as T1DM according to the American Diabetes Association with clinic BP recording in the prehypertensive range and were also categorized according to their dipping status were selected for the study. Informed consent was obtained from all participants. Exclusion criteria were: Previous treatment with antihypertensives, body mass index ≥ 30 Kg/m², presence of any type of cardiac valve disease, not having sinus rhythm, impaired global or segmental LV wall motion, presence of retinal changes on fundoscopy, presence of persistent microalbuminuria (three determinations), use of drugs other than insulin, presence of cardiovascular autonomic neuropathy, or the presence of any other chronic disease in addition to DM. All T1DM patients were treated with two injections a day of neutral protamine Hagedorn (NPH) insulin with variable doses of short-acting insulin before meals that were individually adjusted based on self-blood glucose monitoring results. Research design and methods

Twenty-four hour ABPM measurements were taken automatically in the non-dominant arm by an oscillometric portable monitor (SpaceLabs, Medical Inc, Model: 92512, Redmond WA) every 20 minutes from 07.00 to 22.00 and every 30 minutes from 22.00 to 07.00 h. Day time was defined between 07.00 to 22.00 and night time was defined between 22.00 to 07.00 h. All the cuff sizes were selected according to the arm circumference of the subjects. The monitor was programmed to reject heart rate (HR) values over 110 and lower 50 beats/min (bpm), and SBP>260 and <60 mmHg and DBP >150 and <40 mmHg. All the patients were advised to maintain their daily activities and avoid vigorous exercise during the ABPM. The T1DM patients were recorded the time they went to bed and the time they awoke, exercise periods, if they napped during the day, the time of their meals and, for the patients, the time of insulin injections and any hypoglycemic episodes. Then the recordings of the monitor were downloaded to a PC-compatible computer and the ABPM analyzed for;

1. Mean HR, average SBP, average DBP during awake or sleep over the 24-h period,

2. Percentage nocturnal decline of SBP and DBP calculated as: [(mean daytime BP-mean night time BP)/mean day-time BP] x100 (normal ≥10%).

The ABPM recordings were considered enough and accepted for the diagnosis when at least 80% of all day measurements were recorded and utilized for the diagnosis. Normal considered subjects have ≥50% of BP measurements within the normal range. Pre-hypertension was defined as the systolic blood pressure between 120/139 and the diastolic between 80/89 mmHg (₁₁). The average day time measured by ABPM was taken into account while defining the study population, uncomplicated prehypertensive type 1 DM patients group.

The routine biochemical measurements were fasting and postprandial blood glucose levels, plasma triglyceride, total cholesterol, HDL cholesterol, LDL cholesterol levels were all compared statistically with ABPM outcomes Fasting blood glucose level for the diagnosis of diabetes mellitus was considered as 110 mg/dl (6.1 mmol/L) (₁₂, ₁₃). The definition for DM, was in accordance with the report of the committee of the Japan Diabetes Society for classification and diagnostic criteria of DM; which fasting plasma glucose is 7.0 mmol/L (126 mg/dl) or higher and/or plasma glucose 2 hour after 75 gr of glucose load as 11.1 mmol/L (200 mg/dl) or higher (₁₃). Type I status was diagnosed according to the World Health Organization and American Diabetes Association criteria (₁₄, ₁₅)

All cases underwent a complete two-dimensional transthoracic echocardiographic and Doppler study in the left lateral decubitus position from multiple windows. All studies were performed with Vingmed system V (GE, Horten, NORWAY) echocardiograph by using a 2.5 MHz transducer. Left ventricular dimensions were obtained using the parasternal short-axis view at the level of the papillary muscle. M-mode measurements were obtained using the leading-edge technique in accordance with recommendations as previously described (₁₆). Gain, depth and sector angles were individualized for best measurement. In each echocardiographic method, M mode traces were recorded at a speed of 50 mm/sec and the Doppler signals at 100 mm/sec and measurements of at least three cardiac cycles were averaged in sinus rhythm. Doppler outcomes (Mitral E and A wave, E/A, mitral E wave deceleration time, isovolumetric relaxation time) were utilized to calculate the diastolic function of the LV. Left ventricular ejection fraction was measured according to Teicholz formula and the LV mass according to Devereux formula and the LV mass were indexed to body surface area (₁₇, ₁₈). LV hypertrophy was considered present when LV mass index was >125 g/m2 in men and 110 g/m2 in women (₁₈, ₁₉, ₂₀). Relative wall thickness (RWT) was calculated as (LV Septal wall thickness+LV Posterior wall thickness)/LV internal diameter in diastole. Increased RWT was considered when this ratio is >0.43, which this value has been validated previously (₁₉)

Intraobserver variability was assessed in ten patients by repeating the measurements on two occasions under the same basal conditions. To test the interobserver variability, the measurements, which were obtained from the recordings inside the echo Pac provided by the same company were performed offline by a second observer who was unaware of the results of the first examination. Variability was calculated as mean percent error, derived as the difference between the two sets of measurements, divided by the mean of the observations.

Echocardiograms were read offline with an interobserver reproducibility of 90% and the intra and interobserver variability for measurements derived from M-mode analysis and Doppler-derived parameters (mitral E, A) ranged from 1.2%-7.5%, respectively. The mathematical average of these measurements was used for statistical analysis.

Autonomic nervous system function was evaluated by;

1. Heart rate variation: This was assessed from the measurements of R-R intervals during deep breathing and expressed as the mean of three measurements of HR at maximum inspiration and at full expiration. Normal is >15 bpm, borderline 11-14 bpm, and abnormal ≤10 bpm.

2. Increase in DBP during isometric exercise with a dynamometer (handgrip test) mean of three measurements was taken (21). Normal is ≥16 mmHg, borderline 11-15 mmHg and abnormal is ≤10 mmHg.

At least one abnormal result or one borderline result in each of the two tests was accepted as presence of autonomic dysfunction.

An ophthalmologist performed retinal examination with fundus photography in all subjects with T1DM. Retinal alterations were described as previously reported (₂₂).

Values of selected variables were summarized by standard descriptive statistics and expressed as mean ± SD. The statistical software SPSS, version 11.5 was utilized for all data processing. Independent-Samples T test (Mann-Whitney U test when Levene test is significant) and chi-square tests were used to compare continuous and categorical variables between groups, respectively. Median analysis was performed where appropriate using the Kruskal-Wallis test. All the echocardiographic variables were compared with HR, SBP, and DBP during the day and night both for T1DM and control groups were evaluated by Pearson correlation analysis. All tests considered 95% confidence interval and the statistical significance were defined by a p value < 0.05.

Most of our subjects are young male that we couldn't perform 24-hour ABPM in sufficient number of female and older subjects. Another limitation is classifying individuals on the basis of a nocturnal BP pattern, which were evaluated with a single 24-hour BP monitoring. Evaluation of the LV diastolic function was only based from the mitral inflow Doppler recordings, which cannot rule out pseudonormalization for the LV diastolic function evaluation. The design of this study is a cross-sectional rather than a longitudinal.

Exclusion of high heart rates makes us hard to diagnose autonomic neuropathy, which is a phenomenon occur during the course of T1DM reported previously (₂₇).