Neuroendocrine changes in chronic cardiac failure

Numerous hormonal and neuroendocrine changes have been described in patients with chronic cardiac failure. These affect the balance of vasodilator and vasoconstrictor factors in favour of the latter, to the detriment of the circulation. Whether this is a reaction to central cardiac (haemodynamic) abnormalities, or is an integral part of the syndrome of heart failure, remains to be determined. Catecholamine levels are increased, especially in severe heart failure, and contribute to the vasoconstriction and probably also to lethal ventricular arrhythmias. The renin-angiotensin-aldosterone system (RAAS) is also activated, causing fluid retention and further vasoconstriction. In the earlier stages, some of this increase may be iatrogenic due to the use of loop diuretics or inhibitors of angiotensin converting enzyme, but there is evidence for independent RAAS activation in more severe grades of heart failure. The role of vasoconstrictor peptides such as neuropeptide Y and endothelin is briefly considered. Counterbalancing these are vasodilator peptides, in particular atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP). The possibility of therapeutic interventions to increase circulating natriuretic hormone levels is discussed.

Diffuse plane xanthomatosis associated with a monoclonal band displaying anti-smooth muscle antibody activity

We report a patient with diffuse planar xanthomatous lesions associated with a benign monoclonal gammopathy. This patient has a very high titre of anti-smooth muscle antibody (1:10,240), but normal liver function tests and a normal liver biopsy. The paraprotein band displays anti-smooth muscle antibody activity. There is no evidence of any other underlying disease process. The findings are consistent with a diagnosis of diffuse plane xanthomatosis, but the mechanism of xanthoma formation remains unclear.

Erythrocyte membrane fatty acid composition as a marker of dietary compliance in hyperlipidaemic subjects

Dietary intervention is the first treatment step in management of hyperlipidaemia, but there are few objective criteria of compliance. Whether intensive dietary intervention would produce a detectable change in erythrocyte membrane fatty acid composition which could be used as a marker of compliance was examined in 31 new hyperlipidaemic patients. Over a 6 month period, body mass index fell from 29.0 to 26.9 kg/m2 (P < 0.001) and total cholesterol by 19% from 8.16 to 6.58 mmol/l (P < 0.001). The energy derived from fat was reduced from 38.5% to 29.6% (P < 0.001), and the ratio of dietary polyunsaturated to saturated (P:S) fatty acids in the diet increased from 0.45 to 0.66 (P < 0.01). Small but significant changes were recorded in several red cell membrane fatty acids, and the P:S ratio increased from 0.91 to 1.13 (P < 0.001). It would appear, therefore, that red cell membrane changes parallel dietary changes and hence are a potential marker for compliance with dietary changes.

The effect of minimal exercise on fitness in elderly women after hip surgery

To determine the effect of minimal exercise on functional fitness following total hip replacement in elderly women, 20 women (13 exercisers, 7 controls) who had undergone unilateral or bilateral hip replacement surgery for primary osteoarthritis were studied. An exercise treadmill test with respiratory gas and blood lactate analyses, and a field test of walking speed on a measured course, were administered before and after a twice weekly exercise programme of three months' duration. Markers of cardiorespiratory fitness, including peak achieved oxygen uptake (VO2) and ventilatory and lactate thresholds were measured. Maximum self-selected walking speed was also measured over a flat course. Peak VO2 increased in the exercise group when compared to baseline (P < 0.05) but did not differ from the control group. The exercise group significantly improved their walking speed by 10.1% compared with non-exercising controls (1.41 vs 1.20 m/sec, P < 0.05), and increased VO2 at lactate threshold. The improvements occurred despite the twice weekly exercise sessions being below the recommended frequency of exercise for improving cardiorespiratory fitness. Minimal exercise in elderly women after hip surgery can substantially improve submaximal exercise capacity, as well as walking speed.

The effect of pH on the buccal and sublingual absorption of captopril

The effect of pH on the buccal and sublingual absorption of captopril was evaluated using in vitro techniques and human studies. Partitioning of captopril into n-octanol was lowest over the pH range 5 to 8 and highest at pH values 3, 4 and 9. Using the buccal absorption technique, the partitioning of captopril (2 mg) was examined in six healthy male volunteers from buffered solutions (pH 3, 4, 5, 6, 7, 8, and 9). Lowest buccal partitioning occurred at pH 3 while maximal buccal partitioning occurred at pH 7. These data clearly indicated that the buccal absorption of captopril pharmacokinetic and pharmacodynamic parameters were determined after administration of buffered sublingual captopril (pH 7, optimal hP for absorption as determined from the buccal partitioning data) and unbuffered sublingual captopril. The study was performed in eight healthy volunteers in a randomised single-blind cross-over fashion. The tmax for captopril was found to be approximately 11 minutes earlier after buffered versus unbuffered sublingual administration and AUC0-30 min increased by approximately 30% in the case of buffered captopril. Cpmas, AUC0-180 min and relative bioavailability did not differ between the buffered and unbuffered administration. Pharmacodynamic parameters (BP, heart rate and plasma renin activity) did not differ significantly between buffered and unbuffered sublingual administration. The increased rate of captopril absorption after buffered sublingual administration was small and is likely to offer little therapeutic advantage over conventional sublingual formulation.

The effect of probucol and vitamin E treatment on the oxidation of low-density lipoprotein and forearm vascular responses in humans

This study investigates the hypothesis that lipid soluble antioxidants may increase the resistance of low-density lipoprotein (LDL) to oxidation and also enhance vascular endothelial responses in humans. In a double-blind parallel group study, 24 hypercholesterolaemic patients already on treatment with simvastatin (20 mg day-1), were randomized to supplementary treatment with probucol (500 mg bd), vitamin E (400 IU daily) or placebo for 8 weeks. Mean serum cholesterol before antioxidant treatment was 7.00 mmol l-1. Resistance of LDL to oxidation by copper was increased by 830% in the probucol group and by 30% in the vitamin E group. However, thiobarbituric acid reacting substances in whole serum were not altered by either antioxidant. Probucol lowered HDL- and LDL-cholesterol levels and increased the QT interval. Forearm vascular responses, as measured by venous occlusion plethysmography, to acetylcholine, glyceryl trinitrate and NG-monomethyl-L-arginine, were not significantly changed by antioxidant treatment. Probucol has a major, and vitamin E a minor, effect on LDL resistance to oxidation but neither compound appears to alter forearm vascular responses in vivo.

Gas exchange responses to constant work rate exercise in chronic cardiac failure

OBJECTIVE

To examine the time course of changes in minute oxygen consumption and other gas exchange variables and heart rate during constant work rate exercise in patients with chronic cardiac failure.

DESIGN

Treadmill exercise with on line measurement of gas exchange and a target duration of 10 minutes.

SUBJECTS

Seven men in New York Heart Association class II, six in class III, and seven controls.

MAIN OUTCOME MEASURES

Gas exchange variables and heart rate were averaged for the final two minutes of exercise. Time constants were calculated for the increase in all variables.

RESULTS

Consumption of oxygen at the end of exercise (VO2) was similar in class II patients (mean (95% confidence interval (95% CI) 14.9 (13.6 to 16.1) ml kg-1 min-1), class III patients (13.2 (11.2 to 15.1) ml kg-1 min-1), and controls (13.3 (12.5 to 14.2) ml kg-1 min-1). The patients reached this VO2 more slowly with longer exponential time constants of 0.82 (0.59 to 1.04) min in class II and 1.19 (0.86 to 1.51) min in class III, than the 0.49 (0.35 to 0.64) min in the controls. Time constants of other gas exchange variables and heart rate were also longer in patients. By analysis of covariance, peak VO2 accounted for the between group difference in the time constant for VO2, suggesting that circulatory factors may be an important cause of the delayed kinetics.

CONCLUSIONS

A delayed rise in VO2 in response to exercise may be responsible for subnormal values of VO2 early in exercise in patients with chronic cardiac failure.

Ventilatory and heart rate responses after exercise in chronic cardiac failure

1. To determine if the recovery period after exercise is abnormal in chronic cardiac failure, we studied 15 patients with stable chronic cardiac failure, and 14 normal subjects during and after symptom-limited maximal treadmill exercise. 2. In patients, O2 consumption fell exponentially from 16.8 (13.7-20.0) ml min-1 kg-1 at peak exercise to 6.0 (5.2-6.7) ml min-1 kg-1 at 3 min of recovery and in control subjects it fell from 30.2 (27.0-33.5) ml min-1 kg-1 to 6.7 (5.9-7.4) ml min-1 kg-1 (mean and 95% confidence intervals). The associated decay constants were slower in patients [0.70 (0.58-0.83) min-1 versus 0.93 (0.81-1.05) min-1 in control subjects (P < 0.01, t-test)]. 3. CO2 consumption kinetics displayed similar abnormalities [(k: 0.55 (0.41-0.69) min-1 versus 0.71 (0.59-0.83) min-1, P < 0.05)] and heart rate kinetics showed a similar trend [(k: 0.53 (0.33-0.74) min-1 versus 0.76 (0.62-0.89) min-1, P = 0.08]. 4. We conclude that patients with cardiac failure recover more slowly from exercise than normal subjects, and that this may further impair their ability to perform exercise, with consequent effect on quality of life.

Variable patterns of atrial natriuretic peptide secretion in man

Peripheral circulating levels of atrial natriuretic peptide may exhibit short-term variation compatible with a pulsatile pattern of secretion. We obtained samples every 2 min for 90 min from the antecubital vein of 16 patients with chronic cardiac failure and 13 controls. Overall levels were higher in the patients (median and quartiles 230 (125,325) vs. 26 (16,48) ng l-1; P < 0.001). In both groups there was considerable variability, with 10 (2-12) peaks, 9 (7-15) troughs (both defined as > 2 SD from the mean) and 16 (13-18) pulses (defined by computer) during the sampling period in controls, and a similar number in patients. We then carried out simultaneous sampling in the pulmonary artery, femoral artery and peripheral vein in eight subjects with normal cardiac function and six patients with impaired function due to valvular heart disease. The pattern of variability was preserved in all three sites in both groups, suggesting intermittent secretion rather than variable breakdown of the peptide in the lung. No changes in right atrial pressure or heart rate were observed to coincide with the variations, but levels of the peptide in the pulmonary artery correlated with right atrial pressure in patients (r = 0.87; P < 0.05). The mechanism of such periodicity and its pathophysiological importance remain unknown.

Non-invasive measurement of cardiac output by a carbon dioxide rebreathing method at rest and during exercise

Cardiac output was measured in 11 patients undergoing routine cardiac catheterization using a carbon dioxide rebreathing technique and compared with cardiac output measured by direct Fick and thermodilution. The carbon dioxide rebreathing technique gave consistently lower values for cardiac output than the other two methods (mean difference -0.73, 95% CI -0.95 to -0.51 l.min-1 with the direct Fick and -0.72, 95% CI -1.19 to -0.26 l.min-1 with thermodilution). The direct Fick and thermodilution methods gave similar results (mean difference -0.08, 95% CI -0.32 to 0.16 l.min-1). Cardiac output was also measured in 10 healthy subjects at rest and during two steady-state levels of exercise using the carbon dioxide rebreathing technique. Measurements were made in triplicate on 3 separate days. The technique gave reproducible results between replicates at rest (coefficient of variation 9.1%) and became more reproducible on exercise (coefficients of variation 5.6% and 5.4% respectively at each exercise level). There was a good correlation between cardiac output and oxygen consumption (r = 0.98). The carbon dioxide rebreathing technique is a feasible non-invasive way of measuring cardiac output. It tends to underestimate cardiac output at rest but is reproducible and becomes more so on exercise which is where it should be of most value.

Anaerobic threshold in patients with chronic cardiac failure due to ischaemic heart disease

OBJECTIVES

Anaerobic threshold was measured to examine its relationship with venous lactate levels and the reproducibility of gas exchange methods.

METHODS

Twenty patients with chronic cardiac failure due to ischaemic heart disease underwent two successive treadmill tests with measurements of respiratory gas exchange.

RESULTS

An anaerobic threshold was demonstrated in 78 p. 100 of tests, by plotting either VE/VO2 or VCO2/VO2, and reproducibility between the two tests was satisfactory. Peripheral venous lactate levels did not increase from rest to the end of the exercise stage prior to the anaerobic threshold, but did increase significantly thereafter. Where an anaerobic threshold could be demonstrated, it was reproducible and correlated strongly with peak achieved VO2.

CONCLUSION

However, as measurement of anaerobic threshold requires exercise to 90 p. 100 maximum VO2, it may be preferable to continue until limiting symptoms, and use peak achieved VO2 as the end point. Anaerobic threshold is a reproducible measure of anaerobic exercise capacity.

Metabolic responses to graded exercise in chronic heart failure

To determine if exercise intolerance and fatigue in chronic heart failure could be exacerbated by an abnormal metabolic response to exercise, we studied 12 patients with stable chronic heart failure and 12 normal volunteers during symptom-limited maximal treadmill exercise. Peak VO2 was 17.2 (15.1-19.2) ml.kg-1 x min-1 in patients and 29.9 (26.3-33.5) in controls (mean and 95% confidence intervals; P < 0.0001, t-test). Overall, levels in peripheral venous blood of glucose, glycerol and free fatty acids were greater in patients, although the differences became less marked with increasing exercise intensity. Noradrenaline was elevated in patients at rest, but the peak exercise response was similar to controls. Responses of adrenaline, insulin and glucagon were similar in both groups. We conclude that depletion of the levels of circulating substrates is not contributory to exercise intolerance and fatigue in chronic heart failure. Greater levels of glycerol and free fatty acids may be mediated by excess sympathetic nervous system activity, reflected in elevated noradrenaline levels.

Stress responses after treatment of hypercholesterolaemia with simvastatin

In order to determine whether treatment of hyperlipidaemia with simvastatin impairs exercise stress responses and so may contribute to an excess of suicides and violent deaths, the effects of simvastatin 20 mg daily and placebo on exercise physiology were compared in 19 patients. After 6 weeks of treatment there was no evidence of reduced exercise capacity, or of reduced cortisol or catecholamine responses. It is concluded that treatment of hyperlipidaemia with an inhibitor of HMG-CoA reductase does not significantly modify stress responses, and so the explanation for a possible increase in non-cardiac mortality must be sought elsewhere.

Respiratory gas exchange and metabolic responses during exercise in McArdle's disease

During normal progressive exercise, the gas exchange anaerobic threshold occurs when CO2 production (VCO2) and ventilation (VE) increase so as to depart from a linear relationship to O2 consumption (VO2). This is thought to represent a gas exchange response to metabolic acidosis due to lactate accumulation. Patients with McArdle's disease have previously been reported to exhibit a steepened ventilatory response relative to VCO2, despite an inability to produce lactate. However, the VCO2 response has not been studied. We therefore investigated the VCO2-VO2 and VE-VO2 relationships in seven McArdle's disease patients and seven control subjects during symptom-limited maximal treadmill exercise. Analysis of gas exchange showed that whereas all control subjects had an easily identifiable anaerobic threshold, four of the patients had none and the other three displayed an attenuated threshold. The occurrence of the threshold in one patient was associated with a small rise in lactate and in another patient with an abrupt rise in leg discomfort, suggesting a pain response. Ammonia and the purine metabolite hypoxanthine were elevated during exercise in all patients, suggesting that ammonia may be a product of adenosine monophosphate degradation. Free fatty acid levels were also elevated, and a shift toward utilization of lipid may contribute to abnormal gas exchange responses. It is concluded that lactic acidosis contributes to the gas exchange anaerobic threshold but that other factors, such as discomfort, may be involved in the excess Ve seen during heavy exercise.

The prevalence of preferential nasal breathing in adults

The prevalence of preferential nasal breathing was studied in an awake adult population. One hundred and ninety-four people consented to gentle manual compression of the nostrils. They were advised to 'breathe in and out', but no further information regarding breathing was given to avoid influencing the patient. One hundred and eighty patients (92.8%) commenced immediate regular relaxed breathing. Fourteen patients (7.2%) had difficulty with oral breathing which ranged from irregular mouth breathing associated with distress to no spontaneous respiration. The prevalence of preferential nasal breathing was strongly associated with increasing age (chi 2 for trend, P = 0.007). In addition, a weakly significant association was demonstrated between a history of asthma and this phenomenon (P = 0.047). These findings suggest a tendency for the elderly person to revert to the infant pattern of obligate nasal breathing. Physicians should be aware of this possibility in the elderly patient, especially prior to any procedure which may induce nasal obstruction.

Management of hyperlipidaemia: guidelines of the British Hyperlipidaemia Association

There is considerable evidence to suggest that the identification and treatment of dyslipidaemia will reduce the risk of premature CHD, i.e. before the age of 65. Diagnosis of the cause of raised plasma lipid levels will enable appropriate decisions to be taken with regard to management. The cornerstone of treatment is nutritional counselling and attention to other major risk factors for CHD, particularly smoking and hypertension. For a small percentage of patients with severe hyperlipidaemia drug therapy is indicated. Appropriate drug choices need to be made based on the particular lipid abnormality to be treated. In general those patients with clinical vascular disease are treated more aggressively than those where the aim is primary prevention. More research is needed to determine individual risk more precisely and to allow proper targeting of therapy. Genetic factors, qualitative changes in lipoproteins, lipoprotein (a), fibrinogen, and other coagulation and thrombotic factors are likely to be important in individual risk assessment. There is no doubt that more information is needed from prospective studies of lipid-lowering therapy in terms of risk benefit for affected individuals. Hopefully the major studies currently underway will fill some of the gaps in our knowledge. Until then aggressive therapy with drugs should be reserved for those at highest risk where the benefit is likely to be greatest.

Rare apolipoprotein E variant identified in a patient with type III hyperlipidaemia

We report a rare apolipoprotein E variant in an Irish female with Type III hyperlipidaemia who has the phenotype E2E1 as determined by isoelectric focusing. Sequence analysis of the apolipoprotein E gene from the proband and from four other family members, using DNA amplified by the polymerase chain reaction, demonstrated the presence of a point mutation in the common epsilon 2 allele with a G-->A transition at nucleotide 3791. This was confirmed by digestion with the restriction endonuclease TaqI, which cuts at a new site within the apolipoprotein E gene, created by the base change. This mutation results in a substitution of aspartic acid for glycine at position 127 of the mature protein. We believe this to be the first description of this apolipoprotein E variant in a family from the British Isles. The mutation appears to be 'recessive' with respect to the expression of Type III hyperlipidaemia, although it may be somewhat more potent in this regard than the parent epsilon 2 allele. The Type III hyperlipidaemia is responsive to treatment with diet and gemfibrozil.

Effect of beta-adrenoceptor blockade on atrial natriuretic peptide levels during exercise in angina pectoris

The effects of epanolol (200 mg once daily) and diltiazem (60 mg three times daily) on the response of atrial natriuretic peptide (ANP) to exercise were investigated in a double-blind placebo-controlled crossover study in 16 patients with angina pectoris. Exercise tolerance as assessed by peak oxygen consumption was similar with all treatments. Peak heart rate (mean and 95% confidence intervals) was lower (P < 0.05) with epanolol (121 (115-130) beats min-1) than with diltiazem (137 (126-148) beats min-1) or placebo (141 (130-152) beats min-1). ANP did not change from resting values with placebo or diltiazem, but rose significantly (P < 0.05) with epanolol from 19.7 (13.0-29.8) pg ml-1 (geometric mean and 95% confidence intervals) during supine rest to 49.6 (33.7-73.0) pg ml-1 at peak exercise. Since ANP release is stimulated by atrial distension, patients with untreated angina may stop exercise before atrial dilatation occurs. With beta-adrenoceptor blockade, a reduction in peak heart rate may necessitate increased chamber volumes to maintain cardiac output, accounting for the rise in ANP.

The use of an exponential protocol for bicycle and treadmill exercise testing in patients with chronic cardiac failure

We have studied a standardized exercise protocol suitable for use with a treadmill or bicycle (STEEP protocol) and compared it with a modified Bruce treadmill protocol in a group of patients with chronic cardiac failure. The STEEP protocol has been previously validated in normal subjects. Exercise time (6.79 +/- 2.42 vs 5.34 +/- 1.95 min, P < 0.05) and peak VO2 (16.66 +/- 4.09 vs 15.01 +/- 3.72 ml.min-1.kg-1, P < 0.05) were greater with the STEEP treadmill compared with the bicycle protocol, but VO2 was very similar at equal exercise stages in both modalities. Heart rate and respiratory exchange ratio tended to be greater during bicycle exercise at equal stages. Exercise time was greater with the modified Bruce protocol (9.00 +/- 3.02 min, P < 0.05) than with either STEEP protocol, but peak VO2 (17.13 +/- 4.52 ml.min-1.kg-1) was similar to that obtained with the STEEP treadmill test. We conclude that the STEEP protocol may be used to test patients with chronic cardiac failure, and that exercise times relate well in both treadmill and bicycle. The protocol should prove useful in studies involving a wide range of exercise capacities or both bicycle and treadmill exercise.