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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cigarette smoking is the most preventable cause of cardiovascular morbidity and mortality. Smoking has been associated with a two-to fourfold increased risk of coronary heart disease, a greater than 70% excess rate of death from coronary heart disease, and an elevated risk of sudden death. These risks are compounded in the presence of hypertension, hypercholesterolemia, glucose intolerance, and diabetes, all of which exhibit a synergistic effect with smoking. The relationship between smoking and the risk of peripheral vascular disease has also been well documented. Smokers account for approximately 70% of patients with atherosclerosis obliterans and virtually all those with thromboangiitis obliterans. An association between smoking and cerebrovascular disease remains a matter of debate, although a higher risk of stoke and stroke-related mortality has been observed in smokers than in nonsmokers. Smoking has also been implicated in the development of cor pulmonale, but a direct association with congestive heart failure has not been established. Nicotine and carbon monoxide appear to play major roles in the cardiovascular effects of smoking. Both components adversely alter the myocardial oxygen supply/demand ratio and have been shown to produce endothelial injury, leading to the development of atherosclerotic plaque. Adverse effects on the lipid profile have been noted as well, but the relationship between these changes and the risk of cardiovascular disease remains to be confirmed. Notably, smoking cessation results in a dramatic reduction in the risk of mortality from both coronary heart disease and stroke. In light of the fact that the incidence of smoking has declined primarily among educated sectors of the U.S. population, future efforts must focus on providing effective education, including smoking cessation techniques, to the less-educated groups.
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PMID:Smoking and cardiovascular disease. 149 5

The cardiovascular effect of sham-feeding was measured in seven healthy non-obese human subjects by the Fick principle using the carbon dioxide rebreathing method. The subjects were resting in the sitting position and were exposed to the sight and smell but not the taste of a breakfast meal. Cardiac output decreased significantly from a mean value of 4.0 1 min-1 to 3.5 1 min-1 during sham-feeding (Friedman, P = 0.004). The cardiac output returned to basal values in all seven subjects when the sensory stimulus was removed. The decrease in cardiac output was due to a decreased stroke volume, whereas heart rate and blood pressure did not change. The mechanism of the decrease in cardiac output during sham-feeding remains to be established.
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PMID:Sham-feeding decreases cardiac output in normal subjects. 150 65

The purpose of this study was to examine cardiovascular responses during arm exercise in paraplegics compared to a well-matched control group. A group of 11 male paraplegics (P) with complete spinal cord-lesions between T6 and T12 and 11 male control subjects (C), matched for physical activity, sport participation and age performed maximal arm-cranking exercise and submaximal exercise at 20%, 40% and 60% of the maximal load for each individual. Cardiac output (Qc) was determined by the CO2 rebreathing method. Maximal oxygen uptake was significantly lower and maximal heart rate (fc) was significantly higher in P compared to C. At the same oxygen uptakes no significant differences were observed in Qc between P and C; however, stroke volume (SV) was significantly lower and fc significantly higher in P than in C. The lower SV in P could be explained by an impaired redistribution of blood and, therefore, a reduced ventricular filling pressure, due to pooling of venous blood caused by inactivity of the skeletal muscle pump in the legs and lack of sympathetic vasoconstriction below the lesion. In conclusion, in P maximal performance appears to have been limited by a smaller active muscle mass and a lower SV despite the higher fc,max. During submaximal exercise, however, this lower SV was compensated for by a higher fc and, thus at the same submaximal oxygen uptake, Qc was similar to that in the control group.
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PMID:Cardiovascular responses in paraplegic subjects during arm exercise. 150 43

The respiratory and circulatory activities of patients who underwent carotid body resection (CBR) more than two decades ago were reviewed. No significant ventilatory response to continuous hypoxia was observed. However, in response to stimulation of peripheral chemoreceptors, transient hyperventilation occurred before hypoxemic blood arrived at the central nervous system (single-breath test), which indicated the presence of weak peripheral chemosensitivity. Because of this slight residual peripheral chemosensitivity, which was found shortly after the operation and apparently remained more or less unchanged for greater than 20 years, peripheral chemoreceptor activity, which has been reported in other animal species, does not seem to have returned. Delayed hypoxic hyperventilation reported in dogs and cats with CBR was not observed. Hypoxia significantly depressed the ventilatory response to CO2, but the delayed ventilatory depression with time that has been demonstrated in normal subjects did not occur. In our circulatory studies, hypoxia augmented the heart rate and slightly depressed the stroke volume and total peripheral resistance in the systemic circulation but induced no appreciable changes in arterial blood pressure or cardiac output. We used these results to partition the relative contributions to the overall circulatory response of carotid body stimulation, pulmonary inflation, and other modifying influences. From these calculations, it was inferred that the carotid body reflex plays a dominant role in vascular activities whereas the pulmonary inflation reflex dominates in cardiac activities in humans.
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PMID:Respiratory and circulatory activities in carotid body-resected humans. 150 55

Combined high frequency ventilation (CHFV) with 8 mmHg (1.0 kPa) continuous positive airway pressure (CPAP) and without CPAP (CHFV0) were compared to each other, and to continuous positive pressure ventilation (CPPV) with 8 mmHg (1.0 kPa) CPAP in pigs with oleic acid induced lung injury. The respiratory rate was 15 min-1 and the high frequency (HF) rate 360 min-1. Arterial carbon dioxide tension (PaCO2) was adjusted to 5 kPa and 25% oxygen was used. After CHFV, CPAP was briefly discontinued to allow the establishment of CHFV0 in order to examine the cardiovascular and pulmonary effects of combined high frequency ventilation alone. Mean arterial oxygen tension (PaO2) was 15.8 +/- 3.9 kPa during CPPV, 15.5 + 3.2 kPa during CHFV and 13.2 +/- 5.1 kPa during CHFV0 (ns). The peak airway pressure and the pericardiac pressure were lowest during CHFV0. CHFV provoked significant cardiovascular depression (mean arterial pressure, stroke index, left and right ventricle stroke work index). When compared to CPPV, a non-significant trend towards improved cardiovascular function was found during CHFV0. With similar mean airway pressures (during CHFV0) or the same CPAP (during CHFV) as during CPPV, no further improvement in oxygenation due to HF waves was found. Airway pressure was the major factor causing alterations in cardiovascular function, not the ventilation technique.
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PMID:The effect of combined high frequency ventilation with and without continuous positive airway pressure in experimental lung injury. 151 32

The purpose of this study was to compare the cardiovascular capacities of individuals with Down syndrome (DS) to individuals without Down syndrome who are mentally retarded. Sixteen young adults with DS and 16 individuals without DS (12 males and 4 females, respectively), all with mild/moderate mental retardation, participated in this study. Peak VO2 (absolute and relative), VE (1.min-1), heart rate (HR, b.min-1), and RER (VCO2/VO2) were determined by exercise tests utilizing a treadmill (TM) and Schwinn Air-Dyne ergometer (SAE). The best test result was chosen from the TM and SAE tests and used for statistical comparisons. Cardiac output (Q, 1.min-1) was measured while standing quietly and while walking at 3 mph, 0% grade, using the CO2 rebreathing method for 11 (9 males and 2 females) subjects from each group. Arteriovenous oxygen differences (a-v O2), cardiac index (QI), and stroke volume (SV) were calculated from VO2, Q, HR, and body surface area. Peripheral vascular resistance (PVR), left ventricular work index (LVWI), and left ventricular stroke work index (LVSWI) were calculated from mean arterial pressure, Q, QI, and stroke volume index. Results showed that individuals without DS had statistically significant (P less than 0.01) higher mean peak VO2 (35.6 vs 24.6 ml.kg-1.min-1; 2567 vs 1683 ml.min-1), VE (89.3 vs 59.2 1/min-1), and HR (179 vs 159 b.min-1) than individuals with DS, respectively. No differences in RER were seen between the groups. No differences were seen in cardiovascular parameters measured while quietly standing.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The cardiovascular capacities of adults with Down syndrome: a comparative study. 153 23

The purpose of this study was to determine the neural output of pulmonary stretch receptors (PSRs) in response to conditions that, in previous studies (J. Appl. Physiol. 65: 179-186, 1988 and Respir. Physiol. 80: 307-322, 1990), produced apnea in anesthetized cats. These conditions included changes in airway pressure (Paw; 2 or 6 cmH2O), stroke or tidal volume (1-4 ml/kg), frequency [conventional mechanical ventilation (CMV) vs. high-frequency ventilation (HFV) at 10, 15, and 20 Hz], and levels of inspired CO2 (0, 2, and 5%). These data were needed to assess properly the specific contribution of the PSRs to the apnea found with certain combinations of the above variables. Each PSR was subjected to HFV over a range of mechanical and chemical settings, and its activity was recorded. PSRs exhibited continuous activity associated with pump stroke in 11 of 12 fibers tested. PSRs fired more rapidly when mean Paw was 6 cmH2O [45.3 +/- 0.8 (SE) impulses/s] than when it was 2 cmH2O (31.7 +/- 0.9 impulses/s, P = 0.0001). At both pressures, PSR activity increased as the volume of inflation, or tidal volume, was increased from 1 to 4 ml/kg. At Paw of 2 cmH2O, the number of impulses per second for HFV was not different from that for CMV (averaged over the respiratory cycle), under conditions previously demonstrated as apneogenic for both modes of ventilation. Therefore the absolute amount of information being sent to the brain stem processing centers via PSRs during HFV did not differ from that during CMV. Thus any PSR contribution to HFV-induced apnea must have been the result of changes in the pattern of the signal or the central nervous system's processing of it rather than an increase in the amount of inhibitory afferent signal.
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PMID:Quantitative evaluation of pulmonary stretch receptor activity during high-frequency ventilation. 156 65

We report the successful collection of a large quantity of human resting pulmonary function data on the SLS-1 mission. Preliminary analysis suggests that cardiac stroke volumes are high on orbit, and that an adaptive reduction takes at least several days, and in fact may still be in progress after 9 days on orbit. It also suggests that pulmonary capillary blood volumes are high, and remain high on orbit, but that the pulmonary interstitium is not significantly impacted. The data further suggest that the known large gravitational gradients of lung function have only a modest influence on single breath tests such as the SBN washout. They account for only approximately 25% of the phase III slope of nitrogen, on vital capacity SBN washouts. These gradients are only a moderate source of the cardiogenic oscillations seen in argon (bolus gas) and nitrogen (resident gas), on such tests. They may have a greater role in generating the normal CO2 oscillations, as here the phase relationship to argon and nitrogen reverses in microgravity, at least at mid exhalation in those subjects studied to date. Microgravity may become a useful tool in establishing the nature of the non-gravitational mechanisms that can now be seen to play such a large part in the generation of intra-breath gradients and oscillations of expired gas concentration. Analysis of microgravity multibreath nitrogen washouts, single breath washouts from more physiological pre-inspiratory volumes, both using our existing SLS-1 data, and data from the upcoming D-2 and SLS-2 missions, should be very fruitful in this regard.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Pulmonary function in microgravity. 158 53

The effect of moderate heat stress on cardiac performance during sustained moderate physical work was evaluated in men greater than or equal to 6 weeks after a cardiac event. Subjects (n = 10) performed upright leg cycle ergometer exercise at approximately 50% of peak oxygen uptake for up to 60 minutes in warm (30.0 +/- 0.9 degrees C) and thermoneutral (21.5 +/- 0.3 degrees C) environments. Cardiac output (carbon dioxide rebreathing method), left ventricular ejection fraction and relative left ventricular end-diastolic volume (portable nuclear VEST monitor) were periodically determined. In both environments, heart rate increased (p less than 0.05), stroke volume decreased (p less than 0.05), and cardiac output remained unchanged with exercise time. In the warmer environment, heart rate was increased (p less than 0.05) and stroke volume tended to be decreased (p less than 0.08), with no difference in cardiac output. In both environments, left ventricular ejection fraction did not change from minute 6 to 60 of exercise, whereas relative left ventricular end-diastolic volume decreased (p less than 0.05) with exercise time. Arterial blood pressure was unchanged from minute 6 to 60 in the warm environment. Arrhythmias were not altered by exercise time or environment, and no subjects had evidence of myocardial ischemia. The data indicate that although heart rate increased and stroke volume and relative left ventricular end-diastolic volume decreased with exercise time, cardiac output and left ventricular ejection fraction remained unchanged in both thermoneutral and warm environments.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cardiac response to combined moderate heat and exercise in men with coronary artery disease. 162 5

Blood flow velocity in the basal intracranial arteries can be reliably recorded using transcranial Doppler (TCD) ultrasonography. The utility of Doppler ultrasound in detecting stenosis of arteries has therefore been extended to include the intracranial basal arteries. This has been useful in detecting intracranial stenosis from a variety of causes including atherosclerosis and vasospasm induced by subarachnoid hemorrhage. Changes in cerebral hemodynamics during significantly increased intracranial pressure have also been detected, and have been useful in warning of compromise of the cerebral circulation in head injury. The assessment of the final hemodynamic effects of occlusive disease on the middle cerebral artery can be studied using the CO2 reactivity test. This offers additional diagnostic information in these patients. The direct detection of intracranial microemboli using TCD is also now possible and this has implications in the management of patients with stroke and transient ischemic attacks. Continuous monitoring of the middle cerebral artery velocity has been useful in indicating relative blood flow changes through this artery under certain specific circumstances. By providing continuous information on relative blood flow changes, the dynamics of the cerebral circulation can be studied in more detail. This has allowed the assessment of cerebral autoregulation, as well as blood flow changes, due to changes in cortical activity induced by visual stimulation. Further research on the dynamics of the human cerebral circulation will be possible using this technology.
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PMID:Transcranial Doppler: clinical and experimental uses. 162 39


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