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Biomedical subjects

H Aström

Publications and source records attributed to H Aström.

At least 19 recordsLinked to original sources
PubMed1992

Ischaemic heart disease, skeletal muscle fibres and exercise capacity.

Twenty-eight male patients with ischaemic heart disease (IHD) performed OBLA (onset of blood lactate accumulation) exercise stress tests and had muscle biopsies taken from their vastus lateralis muscle the day before coronary bypass grafting. All 28 patients showed the same exercise performance pattern as compared to healthy sedentary, age-matched, controls: a low exercise intensity eliciting a blood lactate concentration of 2.0 mmol x l-1 (WOBLA), WOBLA corresponded to a high fraction (% WOBLA) of WSL (symptom limited or 'maximal' capacity), and a low peak blood lactate concentration. The high % WOBLA and low peak blood lactate indicated a reduced glycogenolytic capacity ('anaerobic' performance). Muscle fibre composition disclosed a high mean value of fast twitch (FT), type II or 'white' muscle fibres, as compared to sedentary healthy controls. This indicated that this patient group constituted an extreme subgroup of the age-matched population. The distorted muscle fibre composition in IHD could reflect both heredity as well as adaptation to physical inactivity, degenerative cytosolic properties, etc. Muscle and blood contents of a mitochondrial electron translocator and nonspecific radical scavenger, ubiquinone or coenzyme Q10(CoQ10), were low, which coincided with an elevated frequency of the fibre subgroup FT(c). The presence of the FT(c) fibre type is assumed to reflect histological trauma.

Adult↗
PubMed1992

Is blood pressure measurement with a standard cuff reliable?

This study compares blood pressures measured with a standard cuff (rubber bag 12 x 35 cm) with concomitantly measured intra-arterial pressures in 48 subjects. With the standard cuff, and using a diagnostic cut-off limit for diastolic hypertension of 90 mmHg, 15/48 patients were found to be hypertensive, whereas only 4/48 had intraarterial pressure above 90 mmHg. Thus, the specificity of the non-invasive method was only 75%. If higher diagnostic cut-off limits were used, e.g. 95 mmHg, specificity increased to 84%, and with lower cut-offs specificity was 63% for 85 mmHg and 52% for 80 mmHg. A specificity of only 75% is very poor for a method commonly used in screening examinations and may lead to considerable over-diagnosis of mild hypertension.

Adolescent↗
PubMed1992

Is DDD pacing superior to VVI,R? A study on cardiac sympathetic nerve activity and myocardial oxygen consumption at rest and during exercise.

Rate responsive ventricular pacing (VVI,R) has been demonstrated to equal atrial synchronous ventricular pacing (DDD) with regard to hemodynamics and exercise tolerance. Whether the two modes are also comparable, with regard to cardiac metabolic effects, is not yet clear. We assessed central hemodynamics, cardiac sympathetic nerve activity (cardiac norepinephrine overflow), and myocardial oxygen consumption in 16 patients treated with rate responsive atrial synchronous ventricular pacemakers (DDD,R) due to high degree AV block. The study was performed at rest and during supine exercise at two workloads (30 +/- 12 and 68 +/- 24 watts, respectively) during VDD and rate matched VVI pacing (VVIm). Ventricular rates at rest and during both workloads were almost identical. Cardiac output at rest tended to be higher in the VDD mode, due to a slightly higher stroke volume. Central pressures including right atrial pressure and pulmonary capillary wedge pressure were similar in the pacing modes. The coronary sinus blood flow, the coronary sinus arteriovenous oxygen difference, and the myocardial oxygen consumption did not differ between the two pacing modes. Cardiac norepinephrine overflow was similar in the two pacing modes, at rest or during exercise. Thus, we found no significant differences between VDD and VVIm pacing with regard to central hemodynamics, cardiac sympathetic nerve activity (cardiac norepinephrine overflow), or myocardial oxygen consumption either at rest or during moderate exercise.

Aged↗
PubMed1992

Acetylated alpha-tubulin in the pollen tube microtubules.

Three monoclonal alpha-tubulin antibodies YL 1/2 (Kilmartin et al., 1982), 6-11B-1 (Piperno and Fuller, 1985) and DM1A (Blose et al., 1984) were used in indirect immunofluorescence (IIF) microscopy of the microtubule (MT) cytoskeleton in tobacco (Nicotiana tabacum) pollen tubes. The majority of pollen tube MTs contain tyrosinated alpha-tubulin recognized by YL 1/2. Acetylated alpha-tubulin revealed by 6-11B-1 was detected in the generative cell and in the kinetochore fibers, in polar spindle regions, and in the cell plate of the phragmoplast during generative cell division. In addition, small fragments of acetylated microtubules were seen in the older parts of the pollen tube grown on a taxol medium. The interaction of pollen tube MTs with mAb 6-11B-1 suggested that acetylation of alpha-tubulin correlates well with the putative arrays of stable MTs.

Acetylation↗
PubMed1991

Exercise performance and beta-adrenergic blockade in patients with complete heart block treated with ventricular inhibited pacing.

The effect of beta-adrenergic blockade (propranolol) on exercise performance was studied in 15 patients (12 men and 3 women, mean age 70 years) with complete heart block treated with a ventricular-inhibited pacemaker (VVI). In a double-blind procedure, the patients were randomly given either 0.1 mg/kg of propranolol or saline solution i.v. before a first exercise test and vice versa before a second test. The interval between the tests was 24 hours. Nine patients were in sinus rhythm, 4 patients had atrial flutter, and 2 others had atrial fibrillation. The exercise capacity was on an average 11% lower with propranolol than with placebo (p less than 0.001). The most marked reductions (20 and 33%) were found in the two patients with atrial fibrillation. The atrial rate in patients with sinus rhythm was significantly lower with propranolol than placebo both at rest (68 vs. 83 beats/min, p less than 0.001) and at maximal work load (91 vs. 141 beats/min, p less than 0.001). The present findings show that beta blockade has negative effects on exercise capacity in patients with complete heart block treated with VVI pacemakers. This finding should be considered in the selection of drug treatment in patients with fixed rate pacing and concomitant hypertension and/or ischemic heart disease.

Aged↗
PubMed1991

Myocardial lactate dehydrogenase and its isoenzyme activities in transplanted human hearts.

Lactate dehydrogenase and its heart (H) and muscle (M) subunit activities were studied in right ventricular endomyocardial biopsies from eight transplanted human hearts and compared with five chronically failing hearts and six normal human hearts from brain-dead liver/kidney donors. Of the 17 transplant biopsies (taken 5-95 weeks postoperatively), only two showed histologic signs of chronic rejection: They were excluded from the group analysis. A higher proportion of the M subunit of lactate dehydrogenase (M%) was found in the transplanted and the chronically failing hearts than in the normal hearts, presumably reflecting increased myocardial anaerobic glycolytic stress. In the early post-transplantation period, M% was higher in the transplanted than in the chronically failing hearts. Thereafter M% gradually fell, but had not reached normal levels 1-2 years after transplantation. During that time it was similar to the values in the chronic-failure hearts. In the two biopsies with chronic rejection, M% was nearly twice as high as in contemporaneous biopsies showing mild or no rejection. Monitoring of enzymatic adaptation from endomyocardial biopsies may be of clinical interest.

Adolescent↗
PubMed1991

Psychophysical power functions of exercise limiting symptoms in coronary heart disease.

Thirty consecutive male patients with angiographically determined multivessel disease and ten healthy volunteers were subjected to a symptom limited exercise test with stepwise increments of 10 W every minute. Leg exertion, breathlessness, and chest pain were rated according to a category-ratio scale with 10 degrees and psychophysical power functions computed. Depending on whether chest pain was the limiting symptom, patients were subdivided into groups A (N = 20) and B (N = 10). Exercise capacity did not differ between groups A and B. Both groups terminated the exercise test at lower work loads and lower symptom intensities than the healthy volunteers. Psychophysical power functions were similar for leg exertion in the three groups while the growth of breathlessness was lower in group B. In group A the intensity of chest pain increased more rapidly than leg exertion or breathlessness. In conclusion, those patients with coronary heart disease interrupt the exercise test at lower ratings of leg exertion and breathlessness than healthy volunteers. The psychophysical power functions do not grow more rapidly for these sensory modalities in patients than in healthy volunteers.

Anxiety↗
PubMed1990

The reliability of auscultatory measurement of arterial blood pressure. A comparison of the standard and a new methodology.

In 48 individuals with a wide range of arm circumferences blood pressure measured indirectly with two different cuffs was compared to direct intraarterial measurements. The two cuffs were a standard size cuff (12 X 35 cm) and a newly developed cuff, containing three rubber bags of different sizes, which automatically selects the appropriately sized bag in relation to arm circumference (Tricuff, Pressure Group AB, Sweden). The Tricuff correctly placed 42 of the 43 patients in the "normotensive" range, ie, diastolic blood pressure less than 90 mm Hg, whereas the standard cuff put only 33 of 44 patients in this range (P less than .005). The discrepancy was not only due to the expected better performance in patients with obese arms, but also in the subgroup of patients with arms in the range 22 to 31 cm, in which group both cuffs would measure blood pressure with a 12 cm wide rubber bag. The number of correctly identified "normotensive" patients was noticeably higher with the Tricuff than with the standard cuff (30/31 v 25/32, P = .053). The better specificity of the new cuff thus offers an improvement over the standard cuff. There are several potential clinical advantages of this, mainly that the risk of erroneously labelling normotensive individuals as hypertensive is reduced.

Adolescent↗
PubMed1990

Effects of mental and physical stress on central haemodynamics and cardiac sympathetic nerve activity during QT interval-sensing rate-responsive and fixed rate ventricular inhibited pacing.

The effects of mental stress and dynamic exercise on central haemodynamic variables and cardiac sympathetic nerve activity were studied in 15 patients during both fixed rate ventricular-inhibited (VVI) and QT interval-sensing rate-responsive (TX) pacing. Haemodynamic measurements were made at rest, during a mental stress test and during supine exercise at 30 W. Cardiac sympathetic nerve activity was assessed by measuring the arterial and coronary sinus plasma concentrations of noradrenaline (NA) and adrenaline (ADR), the NA kinetics in arterial plasma (radiotracer infusion) and the overflow of NA into the coronary sinus. During exercise the paced ventricular rate increased by 47% with TX. TX provided a higher cardiac output than VVI despite a similar myocardial oxygen consumption and a lower level of cardiac sympathetic activity. Cardiac NA overflow based on 3H-NA extraction over the heart increased from 182 to 1046 pmol min-1 in the VVI mode (P less than 0.01) and from 178 to 793 pmol min-1 in the TX mode (P less than 0.001). The difference in cardiac NA overflow in response to exercise (P less than 0.05 by ANOVA) was not reflected in similar differences in arterial NA concentrations or spill over rates. During mental stress the ventricular rate increased in 12/14 patients. Noradrenaline overflow increased similarly in the two modes. Changes in cardiac NA overflow during mental stress and exercise were correlated with increases in TX pacing rate. This study confirms that both mental and physical stress cause significant changes in cardiac sympathetic nerve activity and central haemodynamic variables, and that the TX pacemaker responds by increasing its pacing rate in a physiological manner.

Aged↗
PubMed1989

The reliability of rate-pressure product as an index of myocardial oxygen consumption in atrial synchronized versus fixed rate ventricular pacing.

The product of heart rate and blood pressure was tested as an index of myocardial oxygen consumption (MVO2) and compared with directly determined MVO2 during ventricular demand (VVI) fixed rate pacing and atrial synchronized (VAT) pacing at rest and during exercise. Systolic brachial artery pressure, pulmonary wedge pressure and MVO2 were similar in the two pacing modes and showed similar response to exercise. The correlation between rate-pressure product and MVO2 was closer with VAT than with VVI pacing (r = 0.74 and r = 0.64, respectively), and the latter value was not improved by using the product of atrial rate and systolic pressure (r = 0.61). The rate-pressure product was significantly higher during VAT pacing compared to VVI during exercise, although MVO2 was similar. The similarity of MVO2 during exercise indicated some other contributory factor than heart rate in VVI pacing, probably increase of contractility and/or volume. Because such factors are not included in currently used indices of MVO2 assessments must be interpreted cautiously, particularly in cases of complete heart block with VVI pacing.

Aged↗
PubMed1988

A comparison of sympathoadrenal activity and cardiac performance at rest and during exercise in patients with ventricular demand or atrial synchronous pacing.

Cardiac sympathetic function was assessed by measuring the coronary sinus overflow of noradrenaline and dopamine at rest and during supine exercise in eight patients with high degree atrioventricular block treated with dual chamber pacemakers (DDD). Patients exercised (30-60 W) during both ventricular inhibited (VVI) and atrial synchronous (VAT) pacing. During exercise cardiac output increased less markedly in the VVI mode than in the VAT mode. The cardiac output response was entirely stroke volume dependent in the VVI mode and mainly heart rate dependent in the VAT mode. Coronary sinus noradrenaline concentrations were higher in the VVI mode at rest and during exercise. Noradrenaline overflow from the heart was enhanced during VVI pacing and increased from about 100 pmol/min (17 ng/min) at rest to 1087 pmol/min during exercise (60 W) in the VVI mode and 545 pmol/min in the VAT mode. Dopamine overflow from the heart was less than 5 pmol/at rest but increased 2-5 fold during exercise. Also arterial concentrations of catecholamine increased more during exercise in the VVI mode, but the differences between pacing modes were less pronounced. Circulating adrenaline seems to be of little importance for cardiac function under these conditions; in healthy individuals the arterial concentrations of adrenaline attained in this study have small effects. Cardiac noradrenaline overflow correlated with pulmonary capillary venous pressures and atrial rates in both pacing modes, indicating a relation between cardiac sympathetic activity and cardiac function. Enhanced cardiac release of noradrenaline may increase cardiac contractility and thereby partially compensate for the lack of heart rate responsiveness to exercise during VVI pacing.

Aged↗
PubMed1987

Prognosis and clinical follow-up of patients resuscitated from out-of hospital cardiac arrest.

A new organization has been formed in which ambulance personnel have been trained to recognize ventricular tachycardia and ventricular fibrillation (VF) and to defibrillate. Cardiac arrest (CA) occurred in 307 patients and 140 were defibrillated. Twenty-eight patients were resuscitated and admitted for further hospital care. A previous history of ischaemic heart disease was found in 24 patients. Twenty-two of the patients admitted were found to have VF, two asystole and four other rhythms. All 11 survivors regained circulation at the site of the CA. At the time of admission all but one of the patients were unconscious and one long-time survivor remained unconscious until the 5th day following admission. Seventeen patients died while still in hospital. In 16 cases a diagnosis of acute myocardial infarction was established, a further six had VF without evidence of acute myocardial infarction and six had other diagnoses. Ten out of the 11 survivors were still alive six months after discharge. Only one case of recurrent VF was seen during a median follow-up period of 16 months. Prolonged coma, especially in combination with convulsions, was associated with a poor prognosis, while early return of circulation was significantly more common among survivors. Ongoing medication with beta-blockers, a high QRS rate on admission and VF without proof of any acute myocardial infarction were also found to be more common in survivors.

Adult↗
PubMed1987

Myocardial demands of atrial-triggered versus fixed-rate ventricular pacing in patients with complete heart block.

Hemodynamics, myocardial oxygen consumption, and lactate concentration were determined by cardiac catheterization at rest and during exercise in eight patients treated with AV universal pacemakers (DDD) for high degree AV block. The pulse generator was alternately programmed in ventricular inhibited (VVI) or atrial synchronous (VAT) mode. During VVI pacing, the cardiac output rose between rest and exercise (4.3-7.6 L/min) due to increased stroke volume. VAT pacing gave significantly greater increase (4.5-8.8 L/min) which, as the stroke volume was unchanged, resulted from accelerated heart rate. The myocardial oxygen consumption and the coronary blood flow did not differ between VVI and VAT mode at rest or during exercise, nor did the modes make a difference in arterial systolic and pulmonary wedge pressures. These observations suggested that VAT pacing offers higher cardiac output than VVI pacing, but with similar demands on myocardial oxygen consumption.

Aged↗
PubMed1987

Mononitrates as monotherapy in the prophylactic treatment of angina pectoris.

This article reviews the results of double-blind comparative studies on the therapeutic use of isosorbide 5-mononitrate as monotherapy in the prophylaxis of angina pectoris. Isosorbide 5-mononitrate appears at least as effective as the same dosage of isosorbide dinitrate and is probably superior to the calcium antagonists. Recent data have shown that isosorbide 5-mononitrate in a controlled-release formulation given once daily has a significantly better antianginal effect than placebo without inducing the development of tolerance.

Angina Pectoris↗