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H Mølgaard

Publications and source records attributed to H Mølgaard.

At least 19 recordsLinked to original sources
PubMed2001

Reproducibility of QT parameters derived from 24-hour ambulatory ECG recordings in healthy subjects.

AIM: To estimate the reproducibility of QT parameters derived from 24-hour ambulatory ECG recordings. METHOD: Ten healthy volunteers aged 25 to 41 years participated. In two 24-hour ambulatory ECG recordings obtained 1 day apart, the QT interval was measured manually at stable heart rates in approximately 16 periods during daytime and 6 periods during nighttime. The association between the QT and RR interval was described by linear regression for day and nighttime separately and the following QT parameters were calculated: the QT interval at heart rate 60 beats/min during daytime (QT(60)day), slope(day), slope(night), and the difference in QT(60) between day and nighttime (DeltaQT(60)). The QT parameters were assessed four times for each participant to discriminate method inaccuracy from day to day variation. The reproducibility was estimated as the coefficient of repeatability, the relative error, and the ratio between within-subject variability and between-subject variability. RESULTS: The coefficient of repeatability, the relative error and the ratio, respectively, were 19 ms, 1.8% and 0.5 for QT(60)day, 0.076, 21% and 0.68 for slope(day), 0.116, 43% and 1.37 for slope(night), and 37 ms, 325% and 1.19 for DeltaQT(60) when estimating the overall day to day reproducibility. Inaccuracy of QT measurement accounted for approximately 40% of this variation, whereas the error caused by selecting segments was small. CONCLUSION: QT(60)day has a high reproducibility and may with advantage replace the conventional QT interval measured on a resting ECG. To assess QT dynamics, the slope of the regression line during daytime is suitable and the short term reproducibility acceptable for clinical trials. Regarding slope(night) and DeltaQT(60), the variation is high and the parameters should be used with caution.

Adult↗
PubMed1999

Heart rate variability in obesity and the effect of weight loss.

To investigate the effects of obesity and weight loss on cardiovascular autonomic function, we examined 28 obese patients referred for weight-reducing gastroplasty, 24 obese patients who received dietary recommendations, and 28 lean subjects. Body weight, blood pressure, and 24-hour urinary norepinephrine excretion were measured, and time and frequency domain indexes of heart rate variability (HRV) were obtained from 24-hour Holter recordings. A measure of long-term HRV, the SD of all normal RR intervals (SDANN), was used as an index of sympathetic activity and the high-frequency (HF) component of the frequency domain, reflecting short-term HRV, as an estimate of vagal activity. All 3 study groups were investigated at baseline, and the 2 obese groups were reexamined at 1-year follow-up. Obese patients had higher blood pressure, higher urinary norepinephrine excretion, and attenuated SDANN and HF values than lean subjects (p <0.01). Obese patients treated with surgery had a mean weight loss of 32 kg (28%), whereas the obese group treated with dietary recommendations remained weight stable (p <0.001). At follow-up the weight-loss group displayed decreases in blood pressure and norepinephrine excretion and showed increments in SDANN and HF values. These changes were significantly greater than those observed in the obese control group (p <0.05). Our findings suggest that obese patients have increased sympathetic activity and a withdrawal of vagal activity and that these autonomic disturbances improve after weight loss.

Adult↗
PubMed1998

Increased left ventricular systolic function in insulin dependent diabetic patients with normal albumin excretion.

Alterations in cardiovascular function may be an aetiological factor for the development of microalbuminuria in patients with insulin-dependent diabetes mellitus. We studied cardiac function with echocardiography in relation to the degree of albuminuria in 27 insulin-dependent diabetes mellitus patients and 13 healthy subjects. Patients were grouped according to urinary albumin excretion: <20 microg x min(-1) (normoalbuminuric), and 20 to 200 microg x min(-1) (microalbuminuric). None were or had been treated with cardiovascular drugs. The normoalbuminuric patients had a higher heart rate, mean velocity of circumferential shortening, stroke velocity index (a measure of contractility), and aortic peak velocity than controls. No difference in diastolic function was present. In the microalbuminuric group, the stroke velocity index was comparable to values observed in healthy subjects. The increased systolic performance (heart rate and contractility) may contribute to the renal hyperperfusion and glomerular hyperfiltration observed in insulin-dependent diabetes mellitus patients before the development of micro- and in turn macroalbuminuria. The possible cause effect mechanisms should be further studied, as preventive medical treatment of the hypercontractile heart is possible. In conclusion, cardiac contractility is increased in insulin-dependent diabetes mellitus patients with normoalbuminuria and returns to levels observed in healthy subjects when microalbuminuria develops.

Adult↗
PubMed1996

[Atrial fibrillation after coronary artery bypass surgery. The significance of preoperative vagus modulation and ectopic atrial activity].

To investigate the impact of pre-operative autonomic balance and atrial ectopic activity on the risk of atrial fibrillation or flutter after aorto-coronary artery bypass surgery 24-hour Holter monitoring was analyzed in 102 patients before coronary artery bypass grafting. Index for vagal tone was calculated as % successive RR-interval differences > 6%. Twenty-nine (28%) of the 102 patients developed atrial fibrillation or flutter. Independent predictors (90% confidence interval) of postoperative atrial fibrillation or flutter were identified by logistic regression analysis: the independent predictors were older age, relative risk 1.07/year (1.02-1.12), vagal index < 10%, relative risk 4.50 (1.40-14.5), > or= 10 ectopic supraventricular beats/24 hour, relative risk 3.03 (1.05-8.72), and one or more event of non-sustained supraventricular tachycardia, relative risk 3.02 (1.11-8.22). Thus, age of the patient, attenuated preoperative cardiac vagal modulation, ectopic supraventricular beats, and paroxysmal non-sustained supraventricular tachycardia are independent risk factors for the development of atrial fibrillation or flutter after coronary artery bypass surgery.

Atrial Fibrillation↗
PubMed1996

Effect of residual noise level on reproducibility of the signal-averaged ECG.

Late potentials are detected at various noise levels in clinical studies. The aim of this study was to assess the effect of residual noise level on the reproducibility of the signal-averaged electrocardiogram (ECG). Two consecutive raw 15-minute ECG from each of 188 patients with coronary artery disease were digitized and stored on optical discs. Each raw ECG was analyzed by two signal-averaging procedures to noise level 0.2 microV or 0.4 microV. Standard time-domain parameters were measured: QRS duration (SA-QRS), late potential (LP) duration, and root-mean-square voltage of the terminal 40 ms of the filtered QRS (RMS40). The SA-QRS was prolonged by 12 +/- 14 ms by the reduction in noise level from 0.4 microV to 0.2 microV, LP duration was prolonged by 10 +/- 10 ms, and RMS40 was reduced by 19 +/- 22 microV. The temporal variation of the measured SA-QRS from ECG1 to ECG2 was significantly lower at noise level 0.2 microV (9 +/- 13 ms) than at noise level 0.4 microV (13 +/- 14 ms) (P < .001). The LP duration was also more stable at noise level 0.2 microV than at noise level 0.4 microV (0.5 +/- 11 ms vs 2 +/- 13 ms, P < .05). The presence of any two of three abnormal parameters (SA-QRS > 120 ms, RMS40 < 25 microV, LP duration > 40 ms) was used as the criterion for the presence of LPs. At noise level 0.4 microV, the proportion of patients with diagnosed LPs in ECG1 was 25% and at noise level 0.2 microV it was 62%. At noise level 0.4 microV, 20% were reclassified from LP-negative in ECG1 to LP-positive in ECG2, and 7% were reclassified from LP-positive in ECG1 to LP-negative in ECG2. At noise level 0.2 microV, 20% were reclassified from LP-negative in ECG1 to LP-positive in ECG2, and 9% were reclassified from LP-positive in ECG1 to LP-negative in ECG2. It was concluded that (1) the diagnosis of LPs is significantly dependent on the extent of noise reduction by signal averaging: and (2) the numerical reproducibility of signal-averaged QRS duration and LP duration is lower at noise level 0.4 microV then at noise level 0.2 microV; and the diagnostic reproducibility of LPs is similar at both noise levels.

Aged↗
PubMed1996

Noise in the signal-averaged electrocardiogram and accuracy for identification of patients with sustained monomorphic ventricular tachycardia after myocardial infarction.

Late potentials are detected at various noise levels in clinical studies. The aim of this study was, in a case-control design, to assess the effect of residual noise level on the identification of patients with sustained monomorphic ventricular tachycardia after myocardial infarction. Electrocardiograms from 16 patients with prior myocardial infarction and documented sustained monomorphic ventricular tachycardia and 41 patients with prior myocardial infarction and without ventricular tachycardia, were analysed by two signal averaging procedures to noise level 0.2 and 0.4 muV. Standard time domain parameters were measured. Two definitions of late potential were analysed: (1) if any two of the following criteria were present (signal-averaged QRS duration > 120 ms, late potential duration > 40 ms, and root-mean-square voltage of the terminal 40 ms of the filtered QRS < 25 muV); or (2) if the signal-averaged QRS duration > or = 120 ms. Overall the signal-averaged electrocardiogram performed better at noise level 0.4 muV compared to noise level 0.2 muV with respect to identification of patients with or without ventricular tachycardia after myocardial infarction. Reducing noise level from 0.4 to 0.2 muV increased the sensitivity, but the consequence was a substantial decrease in specificity. Our data indicate that when a high sensitivity is the goal, the definition based only on signal-averaged QRS duration > or = 120 ms should be applied; sensitivity was 88% and specificity 59% at noise level 0.4 muV. If a high specificity is the goal, the definition should be based on the definition with two abnormal parameters; sensitivity was 69% and specificity 68% at noise level 0.4 muV.

Adult↗
PubMed1995

Atrial ectopic activity and atrial fibrillation/flutter after coronary artery bypass surgery. A case-base study controlling for confounding from age, beta-blocker treatment, and time distance from operation.

To evaluate the impact of ectopic atrial activity and cardiac autonomic function for development of atrial fibrillation or flutter we studied 128 consecutive patients undergoing elective coronary artery bypass grafting. The patients were Holter monitored during a 96-h postoperative period. Autonomic balance was estimated by heart rate variability measurement. Thirty-eight (30%) patients developed sustained atrial fibrillation or flutter. Holter recordings were analyzed in a case-base design matching for age, beta-blocker treatment, and time elapsed after the operation. The number of supraventricular ectopic beats/h was increased (P < 0.01) in the case group during each of the last 7 h before onset of atrial fibrillation or flutter. Episodes of supraventricular tachycardia 62% vs. 26%; cases vs. controls (P = 0.007), episodes of non-sustained atrial fibrillation 29% vs. 0% (P = 0.0009), and episodes of non-sustained atrial flutter 15% vs. 0% (P = 0.05) were significant predictors of atrial fibrillation or flutter. Mean heart rate/h was increased in each of the 24 h preceding the arrhythmia. However, indexes of autonomic heart function did not differ significantly between groups. Patients developing atrial fibrillation or flutter after coronary artery bypass surgery present 'warning' atrial arrhythmias: numerous supraventricular ectopic beats, paroxysmal supraventricular tachycardia, and episodes of nonsustained atrial fibrillation and flutter.

Adrenergic beta-Antagonists↗
PubMed1995

Premature atrial beat eliciting atrial fibrillation after coronary artery bypass grafting.

Of patients undergoing coronary artery bypass grafting 30% develop atrial fibrillation (AF) or flutter. To determine if AF is initiated from the right or left atrium, atrial electrograms were continuously recorded in patients undergoing this procedure. In addition, to study whether the prematurity index of premature atrial contractions (PACs) eliciting AF differs from PACs not provoking AF, the distribution of prematurity indices was evaluated from R-R interval analysis. The right and left atrial recording electrodes were first activated by the ectopic beat provoking AF in six and eight patients, respectively. The prematurity index of the PAC eliciting AF was located in the middle (in half of the patients) or to the left of the median distribution of prematurity indices. The variability in activation of the atrial electrodes suggests that the PAC provoking AF can have its origin in the right, the septal, or the left region of the atrium. The initiation of AF depends on the prematurity index of the PAC.

Atrial Fibrillation↗
PubMed1995

Autonomic balance in patients with angina and a normal coronary angiogram.

The pathophysiology of angina pectoris in patients with a normal coronary angiogram is not clear. Furthermore, the pathophysiological impact of ST changes in syndrome X is controversial. The purpose of this study was to investigate cardiac autonomic function, by measuring 24 h heart rate variability, in patients with and without electrocardiographic evidence of ischaemia during exercise. Thirty-two patients with angina pectoris, a normal coronary angiogram, echocardiogram, hyperventilation test and gastro-oesophageal investigation were studied. Fourteen healthy subjects served as controls. Fifteen patients had significant ST segment depression during stress testing, whereas 17 had no electrocardiographic signs of ischaemia. Heart rate variability was calculated as (1) mean RR = mean of all normal RR intervals, (2) the difference in mean RR level between when awake and when asleep (mean RR wake-sleep)-a tentative index of sympathetic activation, (3) the standard deviation (SD)-a broad band measure of autonomic balance, and (4) a percentage of successive RR interval differences > or = 6% (pNN6%)-an index of vagal modulation. The coronary vascular resistance was measured at rest and during pacing. Mean RR and autonomic indexes did not differ between patients with a positive exercise test and controls (831/884 ms; 24 h SD 125/134 ms; pNN6% 6.715.4%, respectively). Patients with a normal exercise test had shorter mean RR (758 ms vs 844 ms; P < 0.05) and significantly reduced 24-h SD (103 ms vs 134 ms; P < 0.05) than controls, whereas values for vagal index (6.5% vs 5.4%) did not differ from healthy controls. Mean RR wake-sleep also tended to be lower in patients with a normal exercise test (-125 ms vs -173 ms) compared to controls (P < 0.1). Patients with a positive exercise test had a significantly attenuated reduction in coronary vascular resistance during pacing in comparison to patients with a normal exercise test (-0.131 -0.26 mmHg x min. ml-1; P < 0.05). The findings suggest the occurrence of general elevated sympathetic activation in angina patients with a normal exercise test. Patients with a positive exercise test exhibited no signs of autonomic dysfunction although these patients had altered coronary vascular resistance indicating microvascular angina. This supports the suggestion that patients with a normal exercise test constitute an independent pathophysiological entity.

Adult↗
PubMed1995

Low vagal tone and supraventricular ectopic activity predict atrial fibrillation and flutter after coronary artery bypass grafting.

To investigate the impact of pre-operative autonomic balance and atrial ectopic activity on the risk of atrial fibrillation or flutter after aorto-coronary artery bypass surgery 24-h Holter monitoring was analysed in 102 patients before coronary artery bypass grafting. Index for vagal tone was calculated as % successive RR interval differences > 6%. Twenty-nine (28%) of the 102 patients developed atrial fibrillation or flutter. Independent predictors (90% confidence interval) of postoperative atrial fibrillation or flutter were identified by logistic regression analysis: the independent predictors were older age, relative risk 1.07.year-1 (1.02-1.12), vagal index < 10%, relative risk 4.50 (1.40-14.5), > or = 10 ectopic supraventricular beats . 24 h-1, relative risk 3.03 (1.05-8.72), and one or more events of non-sustained supraventricular tachycardia, relative risk 3.02 (1.11-8.22). Thus, age of the patient, attenuated pre-operative cardiac vagal modulation, ectopic supraventricular beats, and paroxysmal non-sustained supraventricular tachycardia are independent risk factors for the development of atrial fibrillation or flutter after coronary artery bypass surgery.

Adrenergic beta-Antagonists↗
PubMed1995

Hemodynamic predictors of atrial fibrillation or flutter after coronary artery bypass grafting.

The cumulated incidence of atrial fibrillation or flutter after coronary artery bypass grafting is 30%. The causes of these arrhythmias have not yet been sufficiently identified. We therefore undertook the present study to analyze the possible association of hemodynamic function during the various phases of coronary artery bypass grafting and the later development of atrial fibrillation/flutter. Hemodynamic function was measured with a pulmonary artery catheter in 120 consecutive patients undergoing elective coronary artery bypass surgery. Thirty-five (29%) of the patients developed atrial fibrillation/flutter. Logistic regression analysis identified independent predictors of atrial fibrillation/flutter. After induction of general anesthesia, the relative risk (95% confidence interval) of older age was 1.09/year (1.03-1.16), and the reduction in relative risk by an increase in left ventricular stroke work was 0.96/gm (0.93-0.99). After weaning from the extracorporeal circulation the independent significant predictors were age, relative risk 1.07/year (1.01-1.13), and increased central venous pressure, relative risk 1.12/mm Hg (1.00-1.26). At the time of admission to the intensive care unit, the relative risk of age was 1.10/year (1.03-1.18), and the relative risk of an increased central venous pressure was 1.26/mm Hg (1.06-1.49). However, the best prediction model (prediction after induction of general anesthesia) only provided a median predicted probability of atrial fibrillation/flutter of 0.37 for the patients who had atrial fibrillation/flutter, and a median predicted probability of atrial fibrillation/flutter of 0.20 for the patients without these arrhythmias. We identified possible hemodynamic predictors of atrial fibrillation/flutter after coronary bypass surgery, but the use of a risk stratification for development of atrial fibrillation/flutter based on hemodynamic function cannot be recommended.

Age Factors↗
PubMed1994

[Left ventricular hypertrophy in patients with aortic stenosis. A comparison between electrocardiography and echocardiography].

Using echocardiography (ECHO) as the reference method, the aim of this study was to determine the sensitivity, specificity, and predictive value of the electrocardiogram (ECG) in detection of left ventricular hypertrophy (LVH) in patients with aortic stenosis. Forty-one patients, 18 men and 23 women aged 25-80 years (mean 49 years) with uncomplicated aortic stenosis were studied. ECG-LVH was estimated by standard fixed voltage criteria. ECHO-LVH was defined according to left ventricular mass (LV mass) calculated by the Penn method. In the total material, the correlation between ECG-LVH and ECHO-mass was poor (r = 0.56, p < 0.05). The sensitivity and specificity of the ECG was respectively 50% and 100%. The positive predictive value of the ECG in detection of LVH was high (100%). We conclude that the sensitivity of the ECG in detection of LV hypertrophy is unsatisfactorily low. Accordingly, it is recommended that echocardiography be performed in all patients suspected of aortic stenosis.

Adult↗
PubMed1994

[Late ventricular potentials after myocardial infarction].

Late potentials in the QRS complex can be detected with signal-averaged electrocardiography and are associated with delayed and disorganized ventricular activation. This article reviews the technique, describes the pathophysiological basis of late potentials, and assesses the prognostic value of late potentials for subsequent development of ventricular tachyarrhythmias and sudden cardiac death in postmyocardial infarction patients.

Age Factors↗
PubMed1994

Early recognition of autonomic dysfunction in microalbuminuria: significance for cardiovascular mortality in diabetes mellitus?

The appearance of microalbuminuria in diabetic patients predicts development of macroalbuminuria and coronary heart disease. Autonomic dysfunction in ischaemic heart disease is related to an increased incidence of arrhythmic deaths. To assess sympathovagal balance in relation to microalbuminuria we performed 24-h spectral analysis of RR interval oscillations in 37 insulin-dependent diabetic patients. Patients were divided according to urinary albumin excretion as normo-(< 20 micrograms/min) (n = 12), micro-(> 20 and < 200 micrograms/min) (n = 14) and macro-albuminuria (> 200 micrograms/min) (n = 11). None had symptoms or signs of ischaemic heart disease at clinical examination or during stress testing. Fourteen matched healthy subjects served as controls. Overall RR interval variability was calculated as the 24-h standard deviation. The square root of power of the low-frequency (0.04-0.15 Hz) and high-frequency (0.15-0.40 Hz) component were considered indices of the sympathovagal interaction and vagal function, respectively. Patients with micro and macroalbuminuria had, compared to control subjects, significantly reduced 24-h standard deviation, a much smaller day/night difference in mean RR level and a significantly reduced amplitude of the low frequency and high frequency oscillations, which were even more reduced in macroalbuminuria. The differences in vagal function were also present after correction for mean RR level, and differences in physical training level and smoking. Insulin-dependent diabetic patients who develop microalbuminuria have significantly impaired vagal function and abnormal sympathovagal interaction, which is further deranged in macroalbuminuria. This early autonomic dysfunction may later contribute to a increased risk for sudden cardiac death.

Adult↗