We sought to describe responses to the 6-min walk test (6MWT) in healthy Canadian adults in order to facilitate interpretation of its results in patient populations. Seventy-seven healthy Canadians aged 45 to 85 years (65 ± 11 years, 40 females) completed this study. During a single visit, three 6MWTs were undertaken. The main outcome measure was 6-min walk distance (6MWD). Age, gender, height, and weight were recorded. In 61 (79%) participants, cardiorespiratory variables were collected during the third 6MWT using a calibrated portable gas analysis system. The 6MWD increased between the first and second test (615 ± 96 to 639 ± 98 m; p
The purpose of this study was to examine the pulse wave velocity, aortic augmentation index corrected for heart rate 75 (AIx@75), and central systolic and diastolic blood pressure during 24-hour monitoring in normotensive volunteers. Overall, 467 subjects (206 men and 261 women) were recruited in this study. Participants were excluded from the study if they were less than 19 years of age, had blood test abnormalities, had a body mass index greater than 2 7.5 kg/m(2), had impaired glucose tolerance, or had hypotension or hypertension. Ambulatory blood pressure monitoring (ABPM) with the BPLab(®) device was performed in each subject. ABPM waveforms were analyzed using the special automatic Vasotens(®) algorithm, which allows the calculation of pulse wave velocity, AIx@75, central systolic and diastolic blood pressure for "24-hour", "awake", and "asleep" periods. Circadian rhythms and sex differences in these indexes were identified. Pending further validation in prospective outcome-based studies, our data may be used as preliminary diagnostic values for the BPLab ABPM additional index in adult subjects.
In 1962, a simplified method of transvenously inserting an intracardiac electrode and implanting the whole pacemaker system under local anaesthesia was reported from the Karolinska Hospital in Stockholm. This simplified method has been universally adopted and pacemakers are now probably implanted too freely in many places. In the Stockholm area pacemakers are implanted half as frequently as in the rest of Sweden and as often as in the United Kingdom.
Since beta2-adrenergic receptors are important regulators of blood pressure, genetic variation in this receptor could explain risk of elevated blood pressure in selected individuals. We tested the hypothesis that Gly16Arg, Gln27Glu, and Thr164Ile in the beta2-adrenergic receptor gene associated with elevated blood pressure.
We genotyped 9185 individuals from the adult Danish general population.
Allele frequencies of 16Arg, 27Glu, and 164Ile were 0.38, 0.44, and 0.01, respectively. Among women never treated with antihypertensive medication those heterozygous for Thr164Ile versus non-carriers had increased diastolic blood pressure (P=0.02). Women heterozygous for Thr164Ile versus non-carriers had an odds ratio for elevated blood pressure of 1.93 (95% CI: 1.30-2.86). Finally, women double heterozygous for Thr164Ile and Gln27Glu or Gly16Arg versus non-carriers at all 3 loci had an odds ratio for elevated blood pressure of 2.49 (1.28-4.85) or 3.19 (1.46-6.97). In men, blood pressure was not influenced by this genetic variation.
In women Thr164Ile heterozygosity is associated with increased diastolic blood pressure, and represent a risk factor for elevated blood pressure in women in the general population. This was most pronounced in those women also heterozygous for Gln27Glu or Gly16Arg.
OBJECTIVES: The purpose of this research was to study possible abnormalities in the beat to beat complexity of heart rate dynamics in patients with a previous myocardial infarction. BACKGROUND: Analysis of approximate entropy of time series data provides information on the complexity of both deterministic and random processes. It has been proposed that regularity or loss of complexity of RR interval dynamics may be related to pathologic states, but this hypothesis has not been well tested in cardiovascular disorders. METHODS: Approximate entropy and conventional time and frequency domain measures of RR interval variability were compared between 40 healthy subjects with no evidence of heart disease and 40 patients with coronary artery disease and a previous Q wave myocardial infarction. The groups were matched with respect to age, and cardiac medication was discontinued in the patients with coronary artery disease before the 24-h electrocardiographic recordings. RESULTS: Approximate entropy was significantly higher in the postinfarction patients (1.21 +/- 0.18 [mean +/- SD]) than in the healthy subjects (1.05 +/- 0.11, p
Abnormalities in beat-to-beat dynamics of heart rate before the spontaneous onset of life-threatening ventricular tachyarrhythmias in patients with prior myocardial infarction.
BACKGROUND: Beat-to-beat analysis of RR intervals can reveal patterns of heart-rate dynamics, which are not easily detected by summary measures of heart-rate variability. This study was designed to test the hypothesis that alterations in RR-interval dynamics occur before the spontaneous onset of ventricular tachyarrhythmias (VT). METHODS AND RESULTS: Ambulatory ECG recordings from 15 patients with prior myocardial infarction (MI) who had spontaneous episodes of sustained VT during the recording and VT inducible by programmed electrical stimulation (VT group) were analyzed by plotting each RR interval of a sinus beat as a function of the previous one (Poincaré plot). Poincaré plots were also generated for 30 post-MI patients who had no history of spontaneous VT events and no inducible VT (MI control subjects) and for 30 age-matched subjects without heart disease (normal control subjects). The MI control subjects and VT group were matched with respect to age and severity of underlying heart disease. All the healthy subjects and MI control subjects showed fan-shaped Poincaré plots characterized by an increased next-interval difference for long RR intervals relative to short ones. All the VT patients had abnormal plots: 9 with a complex pattern, 3 ball-shaped, and 3 torpedo-shaped. Quantitative analysis of the Poincare plots showed the SD of the long-term RR-interval variability (SD2) to be smaller in all VT patients (52+/-14 ms; range, 31 to 75 ms) than in MI control subjects (110+/-24 ms; range, 78 to 179 ms, P
The matter under studies was the way accelerated senescence of armed conflicts participants with brain injuries depends on alcohol addiction developed after the injuries and on dysfunction of neurohumoral regulation of heart activity. It has been established that the posttraumatic alcohol addiction considerably activates the processes of accelerated senescence and lipid peroxidation connected with it, depresses the system of antioxidant protection and enhances the progress of dysfunctions in neurohumoral regulation of heart activity.
The hemodynamic and metabolic effects of acetate were studied in rats in vivo and in the isolated perfused heart. Hemodynamic parameters, myocardial phosphagens, inorganic phosphate, and adenosine were measured in vivo. Acetate uptake, coronary flow, O2 consumption, parameters of the cellular energy state, and hypoxanthine compounds and their washout were measured in heart perfusion experiments. Heart rate (HR), cardiac output, and the peak derivative of the left ventricular pressure rise (dP/dtmax) increased significantly during acetate infusion in vivo, but mean arterial pressure, systolic arterial pressure, and systemic vascular resistance decreased. Heart muscle ATP concentrations decreased after 7 min of acetate infusion. In vivo cardiac work load (HR.(peak left ventricular pressure] showed a positive correlation with tissue adenosine concentration and a negative correlation with phosphorylation potential. Acetate uptake in the perfused hearts was about 2.5 mumol/min per gram wet weight. Acetate perfusion increased O2 consumption and coronary flow concomitantly with a decrease in tissue ATP concentration. Tissue AMP and perfusate effluent adenosine concentration and adenosine output increased significantly, perfusate adenosine showing a non-linear positive correlation with coronary flow. The results demonstrate that acetate induces considerable changes in hemodynamics and metabolism in the heart.
BACKGROUND AND AIMS: We aimed to replicate the previously observed association between acetylcholine receptor subtype M2 (CHRM2) gene polymorphisms and heart rate recovery (HRR) after exercise in patients with a recent acute myocardial infarction (AMI) and assess the prognostic significance of CHRM2 gene variants after AMI. METHODS: HRR was determined as the difference between maximal heart rate and heart rate at 1 minute after the symptom-limited bicycle exercise test in 192 post-AMI patients. Genetic variants at the CHRM2 locus in intron 5 (rs324640) and the 3'-UTR of exon 6 (rs8191992) were assessed. RESULTS: The rs324640 C/C and rs8191992 A/A homozygotes had more than a 3-fold risk of being in the lowest HRR quartile (
