Ole May

Prevalence and prediction of silent ischaemia in diabetes mellitus: a population-based study

OBJECTIVES The aim of the study was to estimate the prevalence of silent ischaemia in diabetic subjects in the population, to compare the prevalence of silent ischaemia in diabetics and non-diabetics and to attempt to predict the presence of silent ischaemia in diabetic subjects. METHODS A random sample of 120 users of insulin and 120 users of oral hypoglycaemic agents aged 40-75 years living in the Danish municipality of Horsens were asked to participate in the study. Corresponding to the youngest half of the sample two non-diabetic controls were randomly selected from the Central Population Register. ST-depression of horizontal or descending character of at least 0.1 mV measured 80 ms after the J-point on either exercise ECG or Holter ECG was considered indicative of myocardial ischaemia. Angina pectoris was considered present if the Rose questionnaire was positive, or chest pain was registered simultaneously with ECG evidence of ischaemia. Individuals with ischaemia, but without angina pectoris, were defined as persons with silent ischaemia. RESULTS Seventy-four percent of the invited group were included. The observed prevalence of silent ischaemia in diabetics was 13.5% (95% CI = 8.5-19.8%). No association was found between silent ischaemia and gender (P = 0.83) or diabetes type (P = 0.67). In the group of diabetics who had controls, the prevalence was 11.4%, and among the controls the prevalence was 6.4% (OR = 1.87, one-sided P = 0.079). Systolic blood pressure was highly predictive of silent ischaemia in the diabetic subjects (P = 0.005). No predictive value could be shown for other variables. CONCLUSION This is the first population-based study of silent ischaemia in diabetes. The prevalence of silent ischaemia in diabetic subjects was 13.5%. The frequency of silent ischaemia did not differ significantly between diabetics and non-diabetics. Systolic blood pressure was predictive of silent ischaemia in diabetes.

Increased QT dispersion in patients with insulin-dependent diabetes mellitus

AIM To compare the QT dispersion in unselected patients with insulin-dependent diabetes mellitus to non-diabetic control subjects and to assess the association between the QT dispersion and cardiac autonomic neuropathy, ischaemic heart disease, blood pressure level and nephropathy. METHODS 42 patients with insulin-dependent diabetes mellitus and 80 control subjects aged 40-57 years participated. The QT interval was measured in a resting 12-lead electrocardiogram (ECG) and the QT dispersion defined as the difference between the maximum and minimum QT interval. Bazetts formula was used to correct for heart rate (QTc). The degree of cardiac autonomic neuropathy was assessed by five function tests and ischaemic heart disease was defined by a previous myocardial infarction, ECG abnormalities or a positive exercise test. RESULTS Compared to control subjects, diabetic patients had a longer QTc interval (433 vs. 416 ms; P=0.002) and a higher QT dispersion (36 vs. 30 ms; P=0.02). In the diabetic group, the QTc interval was prolonged in patients with autonomic neuropathy (449 vs. 420 ms; P=0.007) and the QT dispersion was increased in patients with ischaemic heart disease (51 vs. 33 ms; P=0.004). No association was found to urinary albumin excretion rate or blood pressure. CONCLUSION The QT dispersion as well as the QTc interval is increased in patients with insulin-dependent diabetes mellitus. The association between QT dispersion and ischaemic heart disease indicates that abnormalities in cardiac repolarisation may be caused by complications to diabetes rather than diabetes in itself.

Assessing cardiovascular autonomic neuropathy in diabetes mellitus: How many tests to use?

The aim was to evaluate the relative importance of an established battery of five function tests used in the assessment of cardiovascular autonomic neuropathy (CAN) in diabetes employing spectral analysis of heart rate variability (HRV) as the reference test. In a population-based sample of 178 diabetic persons and 194 non-diabetic controls, five function tests (E/I ratio, Valsalva, 30:15 ratio, Orthostatic-BP, and sustained Handgrip) and power spectral analysis of a 24-h Holter recording were carried out. The high-frequency power during nighttime (LnHF(NIGHT)) was taken to express the parasympathetic function and the daytime low-frequency power (LnLF(DAY)) to express the sympathetic function. The readings were log transformation when appropriate, age-corrected, and standardized to units of standard deviation. Combinations of the three mainly parasympathetic tests and the two mainly sympathetic tests were computed by averaging the standardized readings. A high value of the mean sum of squares in LnHF(NIGHT) or LnLF(DAY) - explained in regression analysis - was assumed to represent the better test or combination of tests. The three parasympathetic function tests each correlated significantly to LnHF(NIGHT). The E/I ratio had a correlation to LnHF(NIGHT) similar to the combination of the three parasympathetic tests and the combination of all five function tests, whereas Valsalva and 30:15 ratio had a significantly poorer association. Sustained Handgrip-correlated significantly poorer to LnLF(DAY) compared to Orthostatic BP and the combination of the two sympathetic tests explained a significantly smaller part of the variation in LnLF(DAY) and LnHF(NIGHT) than did the combination of all five tests. This study indicates that: (1) no information is gained by adding the sympathetic function tests to the parasympathetic tests, (2) the most informative test is the E/I ratio, (3) and knowledge about the degree of CAN as defined by reduced HRV is not significantly increased when the four other function tests assessed are added to the E/I ratio.

The Diurnal Variation in Blood Pressure should be Calculated from Individually Defined Day and Night Times

The aim of this study was to compare the nocturnal fall in BP parameters calculated from individually defined periods of day and night to values computed from collectively fixed day/night definitions. Day and night periods were defined according to 3 different methods: (i) the individually defined time of getting up and going to bed obtained from participant diaries (MethodIND); (ii) the mean time of rising and retiring in the group (MethodMEAN); and (iii) a daytime period from 07.00-22.00 h as recommended by The Scientific Committee (Method722). The ambulatory BP was recorded every 30 min over 24 h. One hundred and eighty-seven persons aged 40-66 years participated. With MethodIND, the BP load, systolic, diastolic and mean BPs were higher in the daytime and lower in the night-time compared to the results using Method722 and MethodMEAN. The nocturnal BP fall using MethodIND was larger than the fall calculated from every possible fixed division in the period from 3 h before till 3 h after the group mean time of getting up and going to bed (p < 0.001). The lowest frequency of non-dipping, defined as a nightly fall in systolic and diastolic BP below 10%, was observed using MethodIND (10%). Compared to MethodIND, 11% were misclassified as non-dippers by Method722 and 8% by MethodMEAN. We conclude that the diurnal blood pressure variation based on individually defined periods of day and night is larger than the variation based on any collectively fixed day/night definition. It is recommended that assessment of the nocturnal change in BP be based on individually defined periods of day and night.

Simple function tests for autonomic neuropathy have a higher predictive value on all-cause mortality in diabetes compared to 24-h heart rate variability☆

AIM To compare the long-term predictive power of heart rate variability (HRV) based on 24 h ECG recordings with a battery of simple autonomic function tests with regard to all-cause mortality in diabetic individuals. METHODS 240 diabetic persons were randomly selected from the diabetic population. A 24-h ECG was obtained and analysed on the Pathfinder 700. In the RR Tools Program time domain and frequency domain parameters were computed. Five function tests were conducted: Valsalva ratio, heart rate response to standing (30:15 ratio), expiration/inspiration ratio (E/I ratio), orthostatic blood pressure response (Ortho BP), and increase in diastolic blood pressure during sustained handgrip. RESULTS 178 patients agreed to participate and 136 patients who completed all 5 function tests and had an acceptable ECG recording were included in the analyses. 64 individuals (47%) died during the 15½ year follow-up. Using Cox proportional hazard analyses correcting for age and gender we found that among the HRV parameters only the power in the low frequency band (LF) had an independent predictive value on all-cause mortality (p=0.0002). Multivariate analysis of the five function tests showed that Valsalva (p=0.002), 30:15 ratio (p=0.037), and handgrip (p=0.037) were independent predictors of death. When finally the independent predictors among the function tests and the HRV parameters were assessed in the same model, no significant value could be shown for LF power (p=0.44). CONCLUSION The study indicates that simple autonomic function tests are superior to HRV based on 24-h ECG recordings in predicting all-cause mortality in the diabetic population.

Bias of QT Dispersion

Background: Prolonged QT dispersion (QID) is associated with an increased risk of arrhythmic death but its accuracy varies substantially between otherwise similar studies. This study describes a new type of bias that can explain some of these differences.

A comparison of the diagnostic value of 2D strain stress echocardiography, myocardial perfusion scintigraphy, and Duke treadmill score in patients suspected of coronary artery disease.

Preinvasive risk stratification is recommended in patients suspected of coronary artery disease (CAD). Stress echocardiography (SE), myocardial perfusion scintigraphy (MPS), and exercise test are the dominant methods of choice. Vasodilator SE is fast and induces only minor increase in heart rate. The diagnostic value of the absolute stress–rest difference in endocardial global longitudinal strain (ΔeGLS) and wall motion (ΔWMI) from adenosine SE was compared to summed stress score (SSS) from MPS and Duke treadmill score (DTS) from exercise test, using quantitative invasive coronary angiography (ICA) as the reference.

Enhanced external counterpulsation – Effect on angina pectoris, QoL and exercise capacity after 1 year

Abstract Enhanced external counterpulsation (EECP) is a new therapy offered to patients with refractory angina pectoris (AP). Purpose. To assess the effect of EECP on AP, quality of life (QoL) and exercise capacity in a design starting with a control period to avoid the influence of regression-towards-the-mean. Methods. Patients were examined two months before EECP, just before, just after, and three and 12 months after EECP. EECP was given for 1 h 5 days a week in 7 weeks. Three sets of pneumatic cuffs were mounted on the lower extremities and inflated sequentially in diastole to 260 mm Hg. Results. 50 patients were included (male 72%, mean age: 62.5 years). Mean daily AP attacks were reduced during EECP from 2.7 to 0.9 (p < 0.005) and the Canadian Cardiovascular Society classification was reduced by at least 1 class in 82% just after EECP, 79% 3 months and 76% 12 months after EECP (p < 0.0002). Generic (SF36) and disease-specific QoL (Seattle AP questionnaire) improved just after, 3 and 12 months after compared with that before EECP. There was a significant improvement in exercise capacity and exercise-induced chest pain just after, three and 12 months after EECP (p < 0.02). No change was detected during the control period. Conclusions. EECP improves generic and disease-specific QoL, angina intensity and exercise capacity in at least 12 months.

Reproducibility of Minimum, Maximum and Median QT Intervals in the 12‐Lead Resting ECG

Background: Heterogeneity in the recovery of ventricular refractory periods is an important factor in the development of ventricular arrhythmia. The QT dispersion (QTD) is increasingly used to measure this heterogeneity but its clinical value is limited due to methodological problems. QTD is defined as the maximum minus the minimum QT intervals that are suspected to be the least reproducible of the QT measurements.

Stress-only myocardial perfusion scintigraphy: a prospective study on the accuracy and observer agreement with quantitative coronary angiography as the gold standard

Objective Patients with normal stress perfusion have an excellent prognosis. Prospective studies on the diagnostic accuracy of stress-only scans with contemporary, independent examinations as gold standards are lacking. Patients and methods A total of 109 patients with typical angina and no previous coronary artery disease underwent a 2-day stress (exercise)/rest, gated, and attenuation-corrected (AC), 99m-technetium-sestamibi perfusion study, followed by invasive coronary angiography. The stress datasets were evaluated twice by four physicians with two different training levels (expert and novice): familiar and unfamiliar with AC. The two experts also made a consensus reading of the integrated stress-rest datasets. The consensus reading and quantitative data from the invasive coronary angiography were applied as reference methods. Results The sensitivity/specificity were 0.92–1.00/0.73–0.90 (reference: expert consensus reading), 0.93–0.96/0.63–0.82 (reference: ≥1 stenosis>70%), and 0.75–0.88/0.70–0.88 (reference: ≥1 stenosis>50%). The four readers showed a high and fairly equal sensitivity independent of their familiarity with AC. The expert familiar with AC had the highest specificity independent of the reference method. The intraobserver and interobserver agreements on the stress-only readings were good (readers without AC experience) to excellent (readers with AC experience). Conclusion AC stress-only images yielded a high sensitivity independent of the training level and experience with AC of the nuclear physician, whereas the specificity correlated positively with both. Interobserver and intraobserver agreements tended to be the best for physicians with AC experience.