International journal of cardiology
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Randomized Controlled Trial Comparative Study Clinical Trial
Heart rate variability after acute myocardial infarction in patients treated with atenolol and metoprolol.
Heart rate variability (HRV) reflects autonomous activity that influences the heart. It has been shown that HRV is depressed during acute myocardial infarction (AMI) and that it recovers with time. Beta-blockers reduce mortality after AMI and changes in sympathico-vagal activity have been suggested to be of importance. Under certain animal experimental conditions, metoprolol has been reported to increase vagal tone more than atenolol, which could have clinical implications. The purpose of the present study was to compare the effects of atenolol and metoprolol treatments on HRV during 6 weeks after AMI and to follow the post MI changes in HRV in patients on betablockers. ⋯ There was no evidence of more increased vagal tone with metoprolol compared to atenolol as has been suggested from animal models. In patients also on chronic treatment with beta blockers, an increase of HRV was seen during the first weeks post MI.
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Previous reports that subjects with anxiety symptoms are at higher risk of sudden death may imply that anxiety induces stable sympathetic hyperactivity. To address this subject, in persons with and without anxiety symptoms, we evaluated autonomic nervous system activity by power spectral analysis of heart-rate and arterial-pressure variability at baseline (rest) and after sympathetic stress (tilt). The 117 subjects selected (56 men and 61 women, age range 23-87 years) were subdivided by questionnaire into three groups: 49 subjects (mean age 55.8+/-2.8 years) had no anxiety symptoms; 36 (mean age 56.8+/-3.6 years) had one anxiety symptom; and 32 (mean age 55.0+/-2.9 years) had two or more anxiety symptoms. ⋯ Recordings of resting systolic arterial pressure variability showed that the group with two or more anxiety symptoms had significantly higher LF power (P<0.05) than symptomless controls. Our findings suggest that persons with high anxiety scores have baseline cardiac sympathetic hyperactivity. They also have low heart-rate variability, possibly explaining their susceptibility to sudden cardiac death.
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Though calcium plays an important role in a number of biologic processes related to the pathogenesis of atherosclerosis, the relationship of serum calcium and phosphorus levels with the angiographic severity of coronary artery disease (CAD) is not known. We retrospectively studied 376 stable patients (age range 31-86 years, mean 59.2 +/- 10.5 years; 68% males) undergoing routine coronary angiography and related the angiographic severity of CAD with the serum levels of total and corrected calcium, phosphorus, albumin, total protein and bicarbonate. The primary variable studied was the number of vessels with haemodynamically significant disease. ⋯ Multiple regression analysis using age, sex, smoking, diabetes, hypertension, hyperlipidaemia, ethnicity and family history, in addition to serum calcium, phosphorus and albumin levels as the predictor variables, showed that serum albumin has an independent negative and serum phosphorus has an independent positive association with the angiographic severity of CAD (P = 0.04 and 0.003, respectively; n = 294). Serum phosphorus level also showed highly significant positive associations with the presence of total or subtotal occlusion and with most severe stenosis observed on angiography. A moderate change in the serum level of albumin or phosphorus confers a risk similar to that associated with smoking, as estimated by the odds ratios.
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Randomized Controlled Trial Comparative Study Clinical Trial
Sympathetic inhibition with clonidine improves autonomic balance in congestive heart failure.
In this double-blind, placebo-controlled crossover study, we examined the effect of transdermal clonidine (given for 5 days) on autonomic control in 14 patients with mild to moderate congestive heart failure by heart rate variability analysis. Compared with placebo, clonidine increased the 24-h mean R-R interval from 718+/-110 to 811+/-117 ms (P<0.01), increased the S. D. of all normal RR intervals (SDNN) from 60.8+/-18.5 to 80.9+/-21.4 ms (P<0.01), the S. ⋯ Changes in heart rate variability measures after clonidine administration were positively related to changes in plasma norepinephrine level. These results indicate that suppressing the sympathetic nervous system by clonidine improves autonomic balance in patients with congestive heart failure. But whether such restoration of the autonomic control has a beneficial effect on the long-term management of these patients still needs further investigation.