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At least 757 records · Page 42Linked to original sources
PubMed1979

Comparison of physiological responses to hypoxia at high altitudes between highlanders and lowlanders.

This report deals with the differences and changes of physiological functions of the highlanders and the lowlanders at different altitudes during the period when the Chinese Mountaineering Team was climbing up and reached the peak of Qomolangma Feng. In a period of relaxation, there are no significant changes in ventilatory responsiveness to hypercapnia, electrocardiogram and electroencephalogram between highlanders and lowlanders with the changes at different altitudes. At 5,000 m a.s.l., however, electrocardiogram and the result of cardiac ventricular functional test show significant differences after the subjects are physically loaded. Those whose electrocardiogram readings show unusual changes, and whose cardiac ventricular functional tests show their physiological functions at low degree after physical activities at the altitude of 5,000 m, have a climbing ability hardly below 6,500 m, while those who have reached the altitudes above 8,200 m have no unusual changes in electrocardiogram, and the results of cardiac ventricular functional tests show that their physiological functions are at high degree.

Acclimatization↗
PubMed2000

Evaluation of diastolic dysfunction and repolarization dispersion in Behcet's disease.

Behcet's disease is a generalized chronic inflammatory disease characterized by genital, ocular, and cardiovascular involvement. Recently, left ventricular diastolic dysfunction, ventricular arrhythmia and sudden cardiac death have been documented in Behcet's disease. From January 1996 to May 1998, we investigated left ventricular systolic and diastolic function, valvular heart disease, ischemic heart disease and repolarization dispersion in 71 cases, 40 men and 31 women (mean age, 36.8+/-10.3 years) with Behcet's disease. All of the results were compared with the control group of 33 men and 22 women (mean age, 37.9+/-9.6 years). Exercise stress test or myocardial perfusion scintigraphy was performed for the documentation of ischemia. All the patients and the controls were recorded by M-mode, 2-D and Doppler echocardiography. Ventricular wall thickness, valvular apparatus, left ventricular systolic and diastolic parameters were evaluated. Repolarization dispersion parameters were calculated as the difference between maximal and minimal values of QT from 12-lead electrocardiogram recording at baseline, immediate and end of recovery from the exercise stress tests. The measured parameters were compared with the control group by using statistical methods. In the Behcet's group of 22 patients (31%) E/A ratio was <1. In the control group of five cases (10%) E/A ratio was <1 (P=0.003). In the Behcet's group isovolumic relaxation time (IRT) and mitral deceleration time (MDT) were longer than the control group (P=0.002, P=0.041, respectively). A mean QT of 368+/-30 ms and mean QT dispersion of 73+/-14 ms in the patient group compared with a mean QT of 395+/-39 ms and mean QT dispersion of 38+/-12 ms in the controls. There was no statistical difference between the mean QT values of the patient and control groups however, ventricular dispersion parameters in the Behcet's patients were longer than in the controls (P<0.001). There was also statistical significance for the QT dispersion between the Behcet's patients with and without diastolic dysfunction (P<0.01). In conclusion, the study reveals that the patients with Behcet's disease have a high incidence of increased diastolic dysfunction and repolarization dispersion. A positive correlation may exist between diastolic dysfunction and QT dispersion.

Adult↗
PubMed1976

Force-velocity-length relations in man expressed by a single hemodynamic expression: the ejection rate of change of power at peak tension.

An attempt was made to develop a hemodynamic indicator of pump function that relates to the contractile characteristics of cardiac muscle. The ejection rate of change of power has ideal characteristics for this purpose. It is firmly based upon theories of fluid dynamics and its derivation is free of assumptions related to heart structure and function. It is measured as p dQ/dt + Q dp/dt, where p = pressure and Q = flow. When measured at peak tension, the ejection rate of change of power was (12.3 +/- 0.8) X 10(8) dynes cm sec-2 in 11 patients with abnormal ventricular performance (P less than 0.001). Studies in dogs showed no effect of preload or afterload. This suggests a relation to characteristics of muscle fibers, which was shown. If one assumes a thin wall sphere, the ejection rate of change of power at peak tension reduces to the following function of tension (T), fiber length (2 pi r), and rate of shortening (2 pi dr/dt): d(power)/dt = 8 pi T](dr/dt)2 + r d2r/dt2[. Thus, the contractile characteristics of muscle fibers (force, velocity and tension) are related in an uncomplicated fashion by a single and highly discriminating hemodynamic indicator of ventricular performance, the ejection rate of change of ventricular power measured at peak tension.

Animals↗
PubMedDate not supplied

Reverse "U" aortotomy for aortic valve replacement after previous coronary artery bypass grafting.

The presence of patent vein grafts on the proximal aorta may give technical difficulties during exposure to aortic valve replacement after previous coronary artery bypass operations. A tongue or reverse "U" shape aortotomy allows excellent exposure of the aortic valve and antegrade cardioplegic administration without mobilizing vein grafts. This approach may facilitate uni- or bidirectional aortic root enlargement in patients with small aortic root.

Aorta↗
PubMed1977

Physiological responses to prompt and sustained squatting. Measurement by systolic time intervals.

Ten healthy men, ages 22 to 35, were studied non-invasively standing (control), at the onset of squatting ('prompt squat'), and at two minutes of squatting. Squatting produced decreases in heart rate, isovolumic contraction time, pre-ejection period, and pulse transmission time from onset of depolarisation to the first heart sound, left ventricular ejection time, and the ejection time index. These results of systolic time intervals are consistent with the bradycardia and increased ventricular filling induced by squatting. Major changes from control measurements were found at the onset of squatting, showing the impact of prompt squat of left ventricular performance.

Adult↗
PubMed2002

Early changes and rules of cardiac function and hemodynamics in rabbits with experimental myocardial contusion.

OBJECTIVE: To study changes and rules of the left ventricular functions in rabbits with myocardial contusion through parallel functional analysis by using echocardiography combined with cardiac catheter intervention. METHODS: Thirty healthy rabbits were selected and impacted to make moderate or severe myocardial contusion by BIM-II biomedical impact machine. The changes of hemodynamics and cardiac systolic and diastolic functions were respectively observed before injury and 1, 4, 8 and 24 hours after injury. RESULTS: After myocardial contusion, the heart rate, systolic pressure, diastolic pressure and mean arterial pressure of rabbits decreased remarkably at 1-4 hours. The left ventricular end systolic pressure (LVESP), the maximum increasing rate of the left intraventricular pressure (+dp/dtmax), isovolumic pressure (IP) and the maximum systolic velocity of the left ventricle (Vmax) also decreased markedly. And then these parameters recovered to the level of preinjury at 8-24 hours. The left ventricular end-diastolic pressure (LVEDP), the rate of the left intraventricular pressure (-dp/dtmax) and the decreasing time constant of the left intraventricular pressure (T) increased remarkably 1 hour after myocardial contusion, and did not decrease until 8 hours after myocardial contusion. Detection by echocardiography showed that ejection fraction of the left ventricle markedly decreased at 24 hours after myocardial contusion, while the systolic volume decreased obviously as early as 1 hour after myocardial contusion, at 4-8 hours it recovered a little and again decreased at 24 hours. The end systolic volume and end diastolic volume increased after myocardial contusion, but statistical significance was only seen at 8 hours after myocardial contusion. CONCLUSIONS: Cardiac functions of the left and right ventricles are markedly injured after myocardial contusion with disorders of the left ventricle diastolic function and of the right ventricle systolic function as the dominant injury. While the systolic function of the left ventricle can recover. Echocardiography shows clinical importance in detection of early injuries of cardiac functions.

Animals↗
PubMedDate not supplied

[Temporal analysis of cardiac frequency variability in basal condition in elderly chagasic subjects in indeterminate form in endemic área].

With the aim of evaluating the cardiac autonomic function in elderly chagasic patients living in an endemic area, we evaluated, by using computadorized heart rate variability, 28 elderly chagasic with the indeterminate form, 28 elderly non chagasic and 28 young healthy control. In all patients we performed conventional electrocardiogram, radiological investigation of thorax, and with contrast of esophagus and colons and echodopplercardiogram. Non chagasic patients did not perform only the exams with contrast. The systolic ventricular function was preserved in all subjects. There was no statistically significant difference between the groups with regard to mean duration of RR intervals. Considering the variance, standard deviation, variation coefficient and pNN50 there was statistically significant difference between the young and elderly groups but no difference was found when the analysis was performed in each one separately for these temporal indexes. We conclude that, in basal condition, the groups of elderly chagasic and no chagasic subjects did not differ as much as the cardiac autonomic modulation in time domain.

Adult↗
PubMed1991

[Cardiovascular tolerance to tianeptine].

The cardiovascular effects of tianeptine were assessed by a specific placebo-controlled trial in healthy volunteers and by heart rate, blood pressure and electrocardiogram data analyses in five studies enrolling depressed patients. In two of these studies the effects of tianeptine were compared to those of amitriptyline. The three other studies were performed as open, long-term trials (up to one-year treatment) in large populations of patients (more than 3,300 patients). The findings show that tianeptine does not modify heart rate, blood pressure, conduction or ventricular function. Tianeptine was well tolerated in depressed patients and induced no significant changes at the current dosage in treatment periods from three-months to one-year even in elderly patients, patients with cardiovascular abnormalities or alcoholic patients. Fewer cases of orthostatic hypotension were observed than with other antidepressants. Suicide attempts with tianeptine overdosage did not lead to death due to cardiovascular complications.

Antidepressive Agents, Tricyclic↗
PubMed1994

Effect of beta-blockade on baroreflex sensitivity and cardiovascular autonomic function tests in patients with coronary artery disease.

We wished to assess the effects of beta-blockade on baroreflex sensitivity and standard tests of integrity of autonomic nervous function in patients with coronary artery disease, and to determine whether the effects of lipophilic (metoprolol) and hydrophilic (atenolol) beta-blockers differ. Beta-blocking drugs increase spontaneous heart rate variability in healthy subjects and in patients with coronary heart disease, but little is known about their effects on baroreflex sensitivity and heart-rate based tests of autonomic integrity. In a randomly allocated double-blind crossover study with three 2-week treatment periods, metoprolol CR 200 mg once a day, or atenolol 100 mg once a day, or placebo once a day, were administered to 18 male patients with stable coronary artery disease. Baroreflex sensitivity was determined from the natural baroreflex challenge of Valsalva strain. Heart rate reactions to standard stimuli were measured. No significant differences were found between the effects of atenolol and metoprolol. Beta-blockade did not significantly affect the baroreflex sensitivity, but it diminished the Valsalva ratio significantly (P < 0.001). The difference between maximum and minimum heart rate during hyperventilation was also significantly lower during beta-blockade. The heart rate response to standing up and the ratio of maximum to minimum heart rate during deep breathing were not influenced by beta-blockade. Discontinuation of beta-blockade seems to be unnecessary for reliable determination of baroreflex sensitivity in patients with coronary artery disease, when the natural pressure challenge of Valsalva strain is sued. Both hydrophilic and lipophilic bet-blockers interfere with certain diagnostic tests of autonomic nervous function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗