Blood pressure and heart rate responses during 24-hour ambulatory monitoring and exercise in men with diabetes mellitus

Arterial stiffness, central blood pressure and body size in health and disease

BACKGROUND

Body size is associated with increased brachial systolic blood pressure (SBP) and aortic stiffness. The aims of this study were to determine the relationships between central SBP and body size (determined by body mass index (BMI), waist circumference and waist/hip ratio) in health and disease. We also sought to determine if aortic stiffness was correlated with body size, independent of BP.

METHODS

BMI, brachial BP and estimated central SBP (by SphygmoCor and radial P2) were recorded in controls (n=228), patients with diabetes (n=211), coronary artery disease (n=184) and end-stage kidney disease (n=68). Additional measures of waist circumference and arterial stiffness (aortic and brachial pulse wave velocity (PWV)) were recorded in a subgroup of 75 controls (aged 51 ± 12 years) who were carefully screened for factors affecting vascular function.

RESULTS

BMI was associated with brachial (r=0.30; P<0.001) and central SBP (r=0.29; P<0.001) in the 228 controls, but not the patient populations (r<0.13; P>0.15 for all comparisons). In the control subgroup, waist circumference was also significantly correlated with brachial SBP (r=0.29; P=0.01), but not central SBP (r=0.22; P=0.07). Independent predictors of aortic PWV in the control subgroup were brachial SBP (β=0.43; P<0.001), age (β=0.37; P<0.001), waist circumference (β=0.39; P=0.02) and female sex (β=-0.24; P=0.03), but not BMI.

CONCLUSION

In health, there are parallel increases in central and brachial SBP as BMI increases, but these relationships are not observed in the presence of chronic disease. Moreover, BP is a stronger correlate of arterial stiffness than body size.

Relationship between esophageal dysfunction and neuropathy in diabetic patients

OBJECTIVE

Few studies have compared esophageal dysfunction with diabetic neuropathy, and their relationship is not yet clear. The aim of this study was to investigate the relationship between esophageal function and diabetic neuropathy.

METHODS

A total of 59 patients with type 2 diabetes were studied. Long-term ambulatory esophageal pH and motility monitoring were performed. The motor nerve conduction velocity (MCV) and coefficient of variation of R-R intervals (CVRR) were also examined.

RESULTS

The 59 patients were classified into four groups: group 1 consisted of patients with both diabetic autonomic neuropathy (DAN) and diabetic motor neuropathy (DMN), group 2 had DMN alone, group 3 had DAN alone, and group 4 had neither DAN nor DMN. In pH monitoring, differences were observed among the four groups in DeMeester score, total number of acid reflux episodes, and % time pH < 4 (p < 0.05). A correlation was observed between % time pH < 4 and MCV; however, no correlation with CVRR was observed. In motility monitoring, differences were observed among the four groups in amplitude of peristaltic waves (p < 0.001), rising velocity of peristaltic waves (p < 0.01), and percentage of effective peristalsis (p < 0.01). A correlation was observed between esophageal motility and MCV; however, no correlation with CVRR was observed.

CONCLUSIONS

Esophageal motility disorder and abnormal acid reflux were related to DMN in diabetic patients. A significant correlation was found between esophageal dysfunction and MCV. However, no significant correlation was found between esophageal dysfunction and CVRR.

Diabetes and exercise

Exercise is frequently recommended in the management of type 1 and 2 diabetes mellitus and can improve glucose uptake by increasing insulin sensitivity and lowering body adiposity. Both alone and when combined with diet and drug therapy, physical activity can result in improvements in glycaemic control in type 2 diabetes. In addition, exercise can also help to prevent the onset of type 2 diabetes, in particular in those at higher risk, and has an important role in reducing the significant worldwide burden of this type of diabetes. Recent studies have improved our understanding of the acute and long term physiological benefits of physical activity, although the precise duration, intensity, and type of exercise have yet to be fully elucidated. However, in type 1 diabetes, the expected improvements in glycaemic control with exercise have not been clearly established. Instead significant physical and psychological benefits of exercise can be achieved while careful education, screening, and planning allow the metabolic, microvascular, and macrovascular risks to be predicted and diminished.

Time course of changes in heart rate and blood pressure variability in streptozotocin-induced diabetic rats treated with insulin

Autonomic neuropathy is a frequent complication of diabetes associated with higher morbidity and mortality in symptomatic patients, possibly because it affects autonomic regulation of the sinus node, reducing heart rate (HR) variability which predisposes to fatal arrhythmias. We evaluated the time course of arterial pressure and HR and indirectly of autonomic function (by evaluation of mean arterial pressure (MAP) variability) in rats (164.5 +/- 1.7 g) 7, 14, 30 and 120 days after streptozotocin (STZ) injection, treated with insulin, using measurements of arterial pressure, HR and MAP variability. HR variability was evaluated by the standard deviation of RR intervals (SDNN) and root mean square of successive difference of RR intervals (RMSSD). MAP variability was evaluated by the standard deviation of the mean of MAP and by 4 indices (P1, P2, P3 and MN) derived from the three-dimensional return map constructed by plotting MAPn x [(MAPn + 1)-(MAPn)] x density. The indices represent the maximum concentration of points (P1), the longitudinal axis (P2), and the transversal axis (P3) and MN represents P1 x P2 x P3 x 10(-3). STZ induced increased urinary glucose in diabetic (D) rats compared to controls (C). Seven days after STZ, diabetes reduced resting HR from 380.6 +/- 12.9 to 319.2 +/- 19.8 bpm, increased HR variability, as demonstrated by increased SDNN, from 11.77 +/- 1.67 to 19.87 +/- 2.60 ms, did not change MAP, and reduced P1 from 61.0 +/- 5.3 to 51.5 +/- 1.8 arbitrary units (AU), P2 from 41.3 +/- 0.3 to 29.0 +/- 1.8 AU, and MN from 171.1 +/- 30.2 to 77.2 +/- 9.6 AU of MAP. These indices, as well as HR and MAP, were similar for D and C animals 14, 30 and 120 days after STZ. Seven-day rats showed a negative correlation of urinary glucose with resting HR (r = -0.76, P = 0.03) as well as the MN index (r = -0.83, P = 0.01). We conclude that rats with short-term diabetes mellitus induced by STZ presented modified autonomic control of HR and MAP which was reversible. The metabolic control may influence these results, suggesting that insulin treatment and a better metabolic control in this model may modify arterial pressure, HR and MAP variability.

Effects of posture on the plasma hormonal and renal water-electrolyte excretory responses to acute water loading in diabetic subjects with hypoadrenergic orthostatic hypotension

The effects of posture on the plasma hormonal and renal water-electrolyte excretory responses to acute water loading (20 mL/kg BW, orally) were studied in six non-insulin-dependent diabetes mellitus (NIDDM) subjects with hypoadrenergic orthostatic hypotension (HOH), eight NIDDM subjects without HOH, and seven nondiabetic subjects. The three groups were similar with respect to basal levels of mean blood pressure (MBP), serum sodium and osmolality, plasma renin activity (PRA), the plasma volume regulatory hormones alpha-atrial natriuretic peptide (ANP), arginine vasopressin (AVP) and aldosterone, and urinary water and sodium excretion. In the supine state, while allowing the subjects to stand only to void, water loading resulted in no changes in MBP and similar responses of these plasma and urinary parameters in the three groups. In the standing state, water loading produced responses of MBP, and plasma and urinary parameters comparable to those in the supine state in the diabetic group without HOH and the nondiabetic group. In the diabetic group with HOH, however, MBP and hourly urinary water and sodium excretion rates were low compared to those in the other two groups. During water loading, plasma ANP decreased, and, despite the fall of MBP, plasma AVP remained unchanged, and PRA and plasma aldosterone increased normally in the diabetic group with HOH. These results demonstrate that, in NIDDM subjects with HOH, changing from lying to standing induces deranged renal water and sodium handling after water loading, accompained by a decrease in plasma ANP, and inadequate responses of plasma AVP, PRA, and plasma aldosterone to hypotension.

Ambulatory blood pressure monitoring and cardiovascular function tests in multiple system atrophy

Cardiovascular tests (CT) of autonomic function and non-invasive ambulatory blood pressure (BP) and heart rate (HR) monitoring were performed in 17 patients with multiple system atrophy (MSA) (mean age 61 +/- 9 years) and in 12 healthy subjects matched for sex and age. CT showed severe autonomic dysfunction with orthostatic hypertension (OH) in eight patients with MSA (47%) (Group I). The remaining nine out of the 17 patients didn't show BP abnormalities during CT but an impaired HR reflex response was found (Group II). BP monitoring showed a reversed circadian BP rhythm in Group I with higher night-time than day-time values, a blunted circadian BP pattern in Group II and a normal day-night BP reduction in controls. Day-night HR reduction was poor in Group II and absent in Group I. Post-prandial hypotension was evaluated after a standard meal. In Group I systolic/diastolic BP fell within 30 minutes after meal (from 135 +/- 16/89 +/- 13 to 118 +/- 17/73 +/- 12 mmHg; p < 0.05) and after two hours had not returned to basal levels. In Group II a reduction of only systolic BP was found within 45 minutes after meal and persisted for one hour. OH clinically identifies a subgroup of MSA patients with a more severe BP dysregulation characterized by severe post-prandial hypotension and reversed circadian BP rhythm. CT and ambulatory BP monitoring are useful tools in identifying early stage of cardiovascular autonomic impairment.

Predictors of the pressor response to the clinic visit in essential hypertensives with and without diabetes mellitus

Predictive models for the pressor response to the outpatient clinic visit (PRC) in essential hypertensives with and without diabetes are proposed. The hypotheses are derived from previous studies about the univariate correlates of this response. PRC was measured with ambulatory monitors. Twenty-four hour blood pressures and average PRCs were similar in the two groups. Diabetics had faster 24-h heart rates, decreased heart rate variability, a broader range of PRCs and more depressor responders. PRC of nondiabetics correlated with duration of hypertension and was dependent on race; the predictive model had R2 of 0.19. In contrast, PRC of diabetics exhibited correlations with age, weight, BP and blood glucose and the model had R2 of 0.71. The data suggest that: diabetics had autonomic dysfunction, that their PRC can be modelled with predictors that are accepted correlates of autonomic neuropathy, and that these predictors attenuated PRC or its buffering. If these results were confirmed by prospective application of the model to a larger group of patients, 'true' blood pressures could be estimated by subtraction of predicted PRC from office blood pressures in diabetic, but not in nondiabetic, hypertensive patients.

Circadian rhythmicity of heart rate and QTc interval in diabetic autonomic neuropathy: implications for the mechanism of sudden death

Patients with diabetic autonomic neuropathy (DAN) exhibit decreased heart rate variability (HRV) and are prone to sudden death. When HRV was used as an index of DAN, the circadian rhythmicity of heart rate and QT intervals was studied in 17 patients with diabetes who had varying degrees of DAN and 13 healthy control subjects. Heart rate and QT and QTc intervals for all subjects were found to exhibit a significant circadian periodicity. Heart rate was lowest and QT and QTc intervals were longest between midnight and 6:00 AM; heart rate increased and QT and QTc intervals shortened in the hours after waking. The diabetic group with more severe autonomic neuropathy (DAN+, HRV = 76 +/- 20 msec, n = 7) had significantly higher heart rate and shorter QT and QTc intervals compared with the diabetic group without autonomic neuropathy (DAN-, HRV = 120 +/- 13 msec, n = 10) or healthy control subjects (CT, HRV = 119 +/- 26 msec, n = 13). Twenty-four-hour mean heart rate was 90 +/- 7 beats/min (range, 79 to 98 beats/min) for DAN+, 77 +/- 8 beats/min (range, 64 to 86 beats/min) for DAN- (DAN+ vs DAN-; p = 0.005), and 74 +/- 7 beats/min (range, 64 to 80 beats/min) for CT (DAN+ vs CT; p = 0.0004). Mean 24-hour QTc was 391 +/- 13 msec (range, 387 to 399) msec for DAN+, 417 +/- 19 msec (range, 413 to 425 msec) for DAN- (DAN+ vs DAN-; p = 0.01), and 412 +/- 28 msec (range, 408 to 419 msec) for CT (DAN+ vs CT; p = 0.09).(ABSTRACT TRUNCATED AT 250 WORDS)

Ambulatory blood pressure in patients with Parkinson's disease without and with orthostatic hypotension

Non-invasive ambulatory recordings of blood pressure and heart rate were performed using a Spacelabs device during day and night periods in patients with Parkinson's disease with (n = 19) or without orthostatic hypotension (n = 19). In patients with orthostatic hypotension, the average systolic and diastolic blood pressure during the night (137 +/- 5/80 +/- 3 mmHg) was higher (p less than 0.05) than during the day period (121 +/- 3/76 +/- 2 mmHg). In patients without orthostatic hypotension, a decrease in blood pressure was recorded during the nocturnal period. In patients with orthostatic hypotension, the blood pressure variability was higher (p less than 0.05) during the day (systolic: 14.6 +/- 1.3%; diastolic: 16.5 +/- 1.0%) than during the night (systolic: 9.1 +/- 0.8%; diastolic: 10.8 +/- 1.1%). The blood pressure load (percentage of values above 140/90 mmHg) during the night was significantly higher than during the day for both systolic (41.2 +/- 8.1 vs. 19.6 +/- 4.7%) and diastolic blood pressure (24.9 +/- 6.9 vs. 16.3 +/- 4.9%). There was a decrease in heart rate in both groups during the night. A fall of 25 mmHg or more in systolic blood pressure after meals occurred in ten patients with orthostatic hypotension and in one patient without orthostatic hypotension. These results indicate that orthostatic hypotension in Parkinson's disease is associated with specific modifications of ambulatory blood pressure including loss of circadian rhythm of blood pressure, increased diurnal blood pressure variability and post-prandial hypotension.

The epidemiology of resting heart rate in a national sample of men and women: associations with hypertension, coronary heart disease, blood pressure, and other cardiovascular risk factors

Few reports have been published on the epidemiology of heart rate in general populations including women and blacks. In the first cycle of the National Health Examination Survey, resting heart rate was significantly higher in women than in men at each age in both races. Age and race were inconsistently related to heart rate, black men having slightly lower rates than white men at ages 18 to 34. The product of heart rate and mean blood pressure was consistently highest in black women. Heart rate was associated with obesity, waist girth, and waist-to-hip girth ratio in men under 55 years and with blood pressure and post-load serum glucose in all groups. Sex differences at each age were larger (6 to 14 beats/min) when adjusted for multiple variables. Multivariate linear regression analysis confirmed the independent associations of heart rate with blood pressure and serum glucose. After controlling for other risk factors, prevalent hypertensive subjects had higher heart rates than normotensive individuals in all groups. Further research is needed to elucidate mechanisms of the associations of resting heart rate with sex, risk factors, coronary heart disease, and mortality.

Influence of acute hyperglycemia on left ventricular function in diabetics assessed by echocardiography

Myocardial dysfunction in diabetes mellitus is reversed by proper correction of metabolic changes. To assess the role of hyperglycemia on cardiac dysfunction, 50 g of dextrose were intravenously infused to 15 subjects with stable type 2 diabetes. Echocardiographic measurements were made at 0, 60, 120, 180, and 240 minutes. In spite of the high levels of blood glucose reached in diabetics, left ventricular ejection fraction, fractional shortening, and stroke volume did not experience significant changes. Moreover, cardiac output significantly (p less than 0.01) increased in diabetics secondary to an increase in heart rate. No cardiac changes were noticed in 7 healthy subjects studied in a similar fashion. However, their induced hyperglycemia was not as elevated as in the diabetic patients. These results suggest that acute induced hyperglycemia per se does not appear to impair left ventricular contractility in diabetics at resting conditions.

Ambulatory monitoring of the ST segment in diabetic men with and without peripheral neuropathy

To assess whether myocardial ischaemia is more common in diabetic patients with neuropathy, 24-hour ambulatory monitoring of the ST segment was performed on 27 diabetic men without peripheral neuropathy and in 28 with neuropathy. The patients were matched for age 54 +/- 7 years (mean +/- SD) versus 54 +/- 7 years and for duration of diabetes (16 +/- 9 years versus 16 +/- 12 years). None had clinical evidence of heart disease. Episodes of ST segment depression were seen during ambulatory monitoring in 12 diabetics (22%) but were not more common in patients with peripheral neuropathy. Four of the 13 diabetics with autonomic neuropathy had ST depression during ambulatory monitoring. During a median follow-up period of 50 months, four patients developed clinical heart disease. Three of these patients had shown ST depression during ambulatory monitoring. ST depression during ambulatory monitoring is common in diabetic men without cardiac symptoms but is not related to the presence of peripheral neuropathy. Diabetics with ST depression during ambulatory monitoring are at increased risk of developing heart disease in subsequent years.