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Biomedical subjects

H Mølgaard

Publications and source records attributed to H Mølgaard.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1994

Spectral components of short-term RR interval variability in healthy subjects and effects of risk factors.

Cardiac neural control can be estimated by frequency domain characterization of RR interval variations. This technique may become a clinical tool, as autonomic dysfunction is involved in the pathophysiology of sudden cardiac death. The study was designed to investigate 24-h cardiac autonomic control in 104 healthy subjects aged 40-77 years and to evaluate the impact of gender, age, smoking and physical training level. The sympathovagal balance was evaluated by spectral analysis of RR interval oscillations. The square-root of power of the high- (HF; 0.15-0.40) and low-frequency (LF; 0.04-0.15 Hz) bands were considered indexes of the vagal function and of the sympathovagal interaction, respectively. In addition, the precise centre frequency of the LF and HF oscillations was determined. The vagal mediated respiratory-dependent HF oscillation exhibited a clear circadian variation, and obtained the highest power values during sleep. The centre frequency was significantly lower during sleep (0.26 Hz vs 0.28 Hz), probably due to a slower respiratory frequency at night. Values for vagal tone were higher in physically trained subjects throughout the 24-h, and decreased by 13% for every 10-year increase in age; it was also reduced in smokers. The amplitude of the LF oscillation exhibited no clear diurnal variation. The mean LF/HF ratio was 3.1. LF power was much higher in males, was reduced by 15% per 10 year increase in age, and was lower in sedentary and smoking subjects, throughout the 24-h. The mean centre frequency of this component was reduced with advancing age (0.08 to 0.06 Hz from age 40 to 80 years). LF and HF power correlated positively, (r = 0.68), and 46% and 16% of the interindividual variation in LF and HF power, respectively, was explained by the four factors (gender, age, smoking, physical activity). Thus gender, age smoking and physical training level have a significant impact on the power and centre frequency of the HF and LF components. These effects must be addressed in investigations on autonomic balance.

Adult↗
PubMed1993

[Fatal hemostatic complications following erroneous thrombolytic therapy in patients with suspected acute myocardial infarction].

This report describes the fate of two young men wrongly treated with thrombolysis for suspected myocardial infarction. Both had electrocardiographic changes upon admission. Correct diagnoses of aortic dissection and haemorrhagic pericarditis was obtained within a few hours, but, due to the prolonged disturbance of haemostasis, appropriate therapy could not be instituted, and outcome was fatal for both patients. These cases underline the importance of rigid ST criteria, and procedures for neutralization of thrombolysis are proposed.

Adult↗
PubMed1993

[The 24-hour heart rate variability. An important predictor of sudden death after myocardial infarction].

The activity of the cardiac autonomic nervous system can be estimated by measurement of beat to beat variations in heart rate-heart rate variability (HRV). In survivors after myocardial infarction, reduced 24-hour HRV, is an independent predictor of mortality/sudden cardiac death. The attenuated HRV is presumed to indicate reduced vagal function and concomitant high sympathetic activity. In experimental studies, this combination reduces the threshold for inducing malignant tachyarrhythmias, and is very probably a clinically important factor for the evolution of ventricular arrhythmias. Measurement of HRV in ordinary 24-hour ECG recordings can, together with other non-invasive measurements, stratify arrhythmic risk in survivors of myocardial infarction.

Arrhythmias, Cardiac↗
PubMed1992

Atrial fibrillation and flutter after coronary artery bypass surgery: epidemiology, risk factors and preventive trials.

Atrial fibrillation and atrial flutter are common arrhythmias after coronary artery bypass grafting. Although the consequences of the arrhythmia are generally not life-threatening, it constitutes a major clinical problem often requiring conversion to sinus rhythm. Atrial fibrillation or flutter can result in hypotension, heart failure, pneumonia, and stroke. This article reviews the literature on epidemiology, electrophysiology, risk factors, and preventive trials. The major conclusions are: (1) In patients undergoing coronary artery bypass surgery, the incidence of postoperative atrial fibrillation or flutter is 20-30%, the peak incidence being on the second or third postoperative day. (2) The strongest independent preoperative predictor for atrial fibrillation or flutter is the patients' age. (3) Intra-atrial conduction delay recorded pre and peroperatively may predict development of atrial fibrillation. (4) Peroperative inducibility of atrial fibrillation by pacing the right atrium may identify patients at risk for postoperative atrial fibrillation. (5) Development of postoperative atrial fibrillation or flutter has not been associated with peroperative or postoperative events. (6) The specificity and sensitivity of age and other possible relevant factors for prediction of atrial fibrillation or flutter after coronary artery bypass grafting is low. (7) No effective prophylactic regimen has yet been established.

Adrenergic beta-Antagonists↗
PubMed1992

Fatal haemostatic complications due to thrombolytic therapy in patients falsely diagnosed as acute myocardial infarction.

This report describes the fate of two young men wrongly treated with thrombolysis for suspected myocardial infarction. Both had electrocardiographic changes upon admission. Correct diagnosis of aortic dissection and haemorrhagic pericarditis was obtained within a few hours, but due to the prolonged disturbance of haemostasis, appropriate therapy could not be instituted, and outcome was fatal for both patients. These cases underline the importance of rigid ST criteria, and procedures for neutralization of thrombolysis are proposed.

Adult↗
PubMed1992

Association of 24-h cardiac parasympathetic activity and degree of nephropathy in IDDM patients.

In insulin-dependent diabetic patients, nephropathy is a predictor of mortality and coronary heart disease. Impaired cardiac vagal function is an important factor in the pathophysiology of sudden cardiac death in coronary heart disease. Autonomic neuropathy in diabetes in particular involves vagal function. Bedside tests and 24-h measurements of cardiac parasympathetic activity were compared in 37 insulin-dependent diabetic patients, and the relationship between 24-h vagal activity and degree of nephropathy was investigated. Nephropathy was classified according to urinary albumin excretion as normoalbuminuria, incipient, and overt nephropathy. Mean age (approximately 30 yr) was not different among groups. The 24-h measurements of parasympathetic activity appeared more sensitive than bedside tests, as 33% of patients without cardiac autonomic neuropathy in bedside tests had 24-h vagal activity values below the 95% confidence limits of 14 healthy control subjects. Patients with incipient or overt nephropathy had significantly lower mean values for vagal activity during both wake and sleep time than healthy control subjects. Increasing degree of nephropathy was associated significantly with increasing attenuation of 24-h vagal activity (P less than 0.001). The covariation of degree of neuropathy and nephropathy may suggest common pathogenetic mechanisms. The reduced 24-h vagal activity, even in the early stages of nephropathy, could be an important risk factor for cardiac death in insulin-dependent diabetic patients.

Adult↗
PubMed1991

Circadian variation and influence of risk factors on heart rate variability in healthy subjects.

Quantification of variations in instantaneous heart rate (HR) can be used to evaluate cardiac autonomic function. A 24-hour standard deviation of all normal RR intervals less than 50 ms in survivors of myocardial infarction has been shown to be an independent marker of adverse prognosis. Twenty-four-hour HR variability in 140 healthy subjects aged 40 to 77 years was determined as (1) standard deviation, and (2) percentage of successive RR interval differences greater than 6%--an index of parasympathetic activity. The 24-hour standard deviation varied between 68 and 261 ms (median 139). Range for index of parasympathetic activity was 0.1 to 29.6% (median 4.4). Twenty percent of the interindividual variation in HR variability was explained by impact of risk factors. Standard deviation was uninfluenced by age, whereas parasympathetic activity decreased by increasing age. High physical training level was independently associated with significantly higher standard deviation (and parasympathetic activity) values during both day and night. Hourly figures of standard deviation decreased during the night, whereas parasympathetic activity increased and peaked early morning. Standard deviation values as low as those reported in high-risk patients were not observed, but comparable low values for, and lack of diurnal variation in, parasympathetic activity were seen in healthy subjects also. In conclusion, risk factors and, in particular, the physical training level have impact on 24-hour HR variability in healthy subjects. This may prove valuable for modification of cardiac autonomic activity in patients.

Adult↗
PubMed1991

Attenuated 24-h heart rate variability in apparently healthy subjects, subsequently suffering sudden cardiac death.

Attenuated cardiac parasympathetic activity appear to be an important risk factor contributing to sudden cardiac death in subjects with overt coronary disease but its predictive value in otherwise healthy normal subjects is not known. We have for 8 years followed 260 apparently healthy adult subjects who underwent Holter monitoring. Twelve died, 14 developed ischaemic heart disease and four suffered sudden cardiac death. A healthy control subject was matched, along with other risk factors, for each case. In each subject 24-h heart rate variability was calculated as the deviation of all normal R-R intervals from mean R-R (SD) and the percentage of successive R-R interval differences exceeding 6% (%DIF6%)--this was used as an index of cardiac parasympathetic activity. There were no significant differences in heart rate variability between the cases developing problems and controls. In the sudden cardiac death victims, however, there was a clear trend towards lower heart rate variability. In them waketime mean SD was 73 ms versus 85 ms for cases and controls respectively (p = 0.08), and for sleeptime 61 ms versus 76 ms (p = 0.07). Compared to normal limits for heart rate variability obtained in 140 subjects that remained healthy for 8 years, figures for both SD and %DIF6% in sudden cardiac death subjects were at or below 95% confidence limits. The results indicate that altered autonomic balance may contribute to sudden cardiac death even in apparently healthy subjects. Subjects with a low 24-h heart rate variability on Holter monitoring may be predicted at an early stage of being at greater risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Evaluation of the Reynolds Pathfinder II system for 24 h heart rate variability analysis.

Heart rate variability (HRV) in 24-h Holter recordings is normally determined using commercially available Holter equipment. However, short-term speed variations in tape-based Holter systems have not been thoroughly investigated and recommendations for speed control are vague. In this study, overall accuracy and precision of RR interval measurement was assessed for two types of tape recorder replayed on the same Reynolds Pathfinder II system. Artificial QRS complexes spaced at exact intervals were recorded simultaneously by the two recorders. In addition, records of 118 healthy subjects were evaluated for false-positive normal-normal intervals. During replay, digital output from the pathfinder was processed by a locally developed personal computer-based HRV system. Using the recorded crystal generated timing track (TT) for speed control and the TT dependent speed surveyor (SS), set to allow speed errors up to +/- 3.1%, mean RR per 5 min.h-1.24 h-1, for test tapes, corresponded exactly to true RR, for both recorders. Beat-to-beat variation, for 1000 ms test intervals, calculated as standard deviation (SD) and root mean square of successive differences (RMSSD) was 3 ms, 3 ms versus 5 ms, and 8 ms for Oxford and Tracker tapes respectively. No difference between sequential intervals exceeded +/- 10 ms versus +/- 20 ms for Oxford and Tracker respectively. Reproducibility of mean RR and HRV parameters for patient records, expressed as a coefficient of variation, was 0.1-1.7%. False positive normal-normal intervals greater than 2.3 s, due to artifacts, were found in 99 of 118 records, and these increased mean SD and RMSSD values significantly, whereas percent successive RR interval differences greater than 50 ms were unaffected. A crystal generated TT (60/16 Hz) and an SS allowing a maximum error of +/- 3.1%, together correct speed during recording and replay to a degree that is acceptable for HRV analysis. A simple estimate of HRV counts of successive RR interval differences greater than 50 ms is a reliable parameter as it is relatively insensitive to artifact.

Electrocardiography, Ambulatory↗
PubMed1990

[Lowest heart rate and pauses in adults with healthy hearts].

The lowest heart rate measured in a one minute period (HRmin) and prevalence of pauses, was determined with eight years interval, in two 24 hour Holter Monitorings, in 183 persistently healthy adults aged 40 to 85 years. For the individual, HRmin is a stable parameter, but the level depends on sex, smoking and physical activity habits. Independently of age, HRmin less than 40 beats per minute and pauses greater than or equal to 2.0 seconds are rare events, and should be considered abnormal.

Adult↗