Evaluation of left ventricular performance in menopausal women.

The incidence of ischemic heart disease is well documented in the literature in post menopausal women but the degree of deterioration of left ventricular performance in estrogen deficient state in women is not very clear. The present study was conducted to find the left ventricular performance by recording systolic time intervals (STIs) in 50 post menopausal women having either natural or surgical menopause and that was compared with 25 premenopausal controls. There was significant (P<0.01) increase in QS2-I, PEP-I and PEP/LVET ratio but significant (P<0.01) decrease in LVETI in surgical menopause group whereas the natural menopause group showed less increase in QS2-I (P<0.05), PEP/LVET ratio (P<0.01) and decrease (P<0.01) in LVET-1. Thus, the performance of left ventricle is more affected in surgical menopause group as compared to natural menopause group. The ventricular dysfunction was observed by STIs prior to the appearance of clinical signs and symptoms.

Effects of breath holding in air on cardiac responses in man / 体力科学

Healthy male subjects were asked to hold their breath in air at the tidal inspiratory level, and time-dependent changes in mean values of several parameters of cardiovascular function were studied. The heart rate increased abruptly after the beginning of breath-holding and then decreased slightly with time. The stroke volume (SV) remained significantly low until the end of breath-holding, so that the cardiac output was decreased in parallel. With regard to the systolic time interval, the totai eiectromechanical systole and the left-ventricular systolic time (LVET) were not significantly changed, whereas the pre-ejection period (PEP) was markedly prolonged. Therefore, ratios of PEP/LVET and SV/LVET were increased and decreased with time, respectively. As the systolic, and in particular the diastolic blood pressures were elevated, the pulse pressure was reduced. Ratios of the diastolic and systolic times in relation to the heart rate at rest, during breath-holding and during recovery after breath-holding were all proved to be described by a single regression curve. However, the ratios obtained for cycling exercise at various heart rates showed a marked shift above the curve. These results clearly indicate that cardiac performance is lowered during breath-holding in air.

Circulatory responses to sudden strenuous exercise. A study by mechanocardiographic method / 体力科学

A study was conducted for further investigation of the mechanism of notch formation of heart rate (HR) in sudden strenuous exercise (SSE), and rapid increase in stroke volume (SV) right after SSE which were the questions arised in the prior experiment.<BR>Six healthy male students volunteered for the study. A bicycle ergometer was prepared for SSE. The intensity and duration of SSE were 100%VO<SUB>2</SUB>max and 1 min, respectively. Warming-up consisting of 80%VO<SUB>2</SUB>max for 5 min, preceeded SSE. The interval between SSE and warming-up varied from 5 to 30 min. A control experiment was also conducted without warming-up.<BR>The main results obtained were as follows :<BR>1) Diastolic time (DT) temporarily elongated when a notch of HR was formed at the early stage of SSE. Warming-up prevented this formation. No notch was observed throughout total electromechanical systolic time (QS<SUB>2</SUB>), left ventricular ejection time (LVET) or preejection time (PEP) .<BR>2) DT was prolonged immediately after SSE, while LVET, PEPi (PEP index, Weissler's equation) were shortened. PEP/LVET did not change in the initial stage of the recovery period, while electrical systolic time (QT) and QS<SUB>2</SUB> shortend and QT/QS<SUB>2</SUB> increased temporarily.<BR>These results suggest the following conclusions :<BR>1) Notch formation observed in heart rate is due to the temporary extension of DT at the early stage of SSE.<BR>2) Decrease in afterload may be the main cause for the rapid increase in stroke volume after SSE, though other factors such as increase in preload, myocardial contractility and sympathetic tone should also be considered.

Comparisons of left ventricular systolic and diastolic times in exercise between trained and untrained men / 体力科学

The systolic time intervals (STI's) and the diastolic time (DT) as functions of the RR interval during exercise were proved to be described by cubic regression equations that converge to the origin of the coordinates. Using the equations, we compared I) the systolic time and DT of trained and untrained men, and II) examined the relations between parameters of STI's. I) Forty healthy male subjects aged 19-22 years old were divided into three groups, i, e., 8 long distance runners (group LD), 16 men with relatively high fitness (group A) and 16 men with relatively low fitness (group B) . They performed submaximal exercise test using a cycle ergometer for measuring the time of electromechanical systole (QS<SUB>2</SUB>) and DT. After test, maximal exercise test was conducted to determine the maximal heart rate (HRmax) in each subject. Means±SD of the minimum QS<SUB>2</SUB> and the minimum DT of the 40 subjects predicted from the regression equations at the HRmax were 209.7±12.5 and 108.2±15.6 ms, their ratio being about 2: 1. The QS<SUB>2</SUB> was significantly shorter, whereas DT was longer in the group LD than in the groups A and B at the HR of more than 120 bpm. II) Ten healthy male subjects aged 19-22 years old performed submaximal exercise to clarify the relations between any two of QS<SUB>2</SUB>, the left ventricular ejection time (LVET) and the preejection period (PEP) at the same HR: there were positive and negative significant correlations between QS<SUB>2</SUB> and LVET, and between LVET and PEP, respectively, at the HR of more than 100 bpm. These results reveal that, when the HR is increased in exercise, the left ventricular systolic time (QS<SUB>2</SUB>) is shortened while the diastolic time is lengthened for the subjects trained as long distance runners. The shortening of the systolic time is mainly caused by shortening of LVET. The changes in the systolic and diastolic times suggest that contractility of cardiac muscle is enhanced during exercise of above moderate intensity after an extensive period of the aerobic training.

Changes in systolic and diastolic time intervals during prolonged exercise. (Part 3) / 体力科学

A study was undertaken to elucidate the mechanism responsible for the specific changes in systolic time intervals (STIs), diastolic time (DT) and the ratio of total electromechanical systole to DT (QS<SUB>2</SUB>/DT), which were observed during prolonged exercise<SUP>17, 19)</SUP> Sixteen healthy male students performed short-term incremental maximal exercise and 40-min submaximal exercise with a work load requiring 65% of maximal oxygen consumption on a bicycle ergo-meter, Heart rate (HR), stroke volume (SV), blood pressure (BP), STIs and DT were calculated from electrocardiogram, phonocardiogram, derivative of ear densitogram, impedance cardiogram and finger arterial pressure wave.<BR>1) During the short-term exercise, STIs, DT and QS<SUB>2</SUB>/DT changed rectilinearly in accordance with increased HR, whereas they changed in a specific zigzag pattern during the prolonged exercise.<BR>2) During the prolonged exercise, SV and BP were lower than those during the short-term exercise, except for SV between 1 and 2 min after the start of the exercise. From 2 min onwards, left ventricular ejection time (LVET), QS<SUB>2</SUB> and QS<SUB>2</SUB>/DT became smaller than those during the short-term exercise.<BR>3) Differences between the measured values of LVET, pre-ejection period (PEP) and PEP/LVET and those predicted by multiple regression equations during the prolonged exercise were smaller than those during the short-term exercise.<BR>From these findings, it was concluded that the specific changes observed in STIs, DT and QS<SUB>2</SUB>/DT during prolonged exercise are produced by decrease of SV and BP in the early stage, and probably influenced by a decrease in myocardial contractility in the late stage.

Changes in systolic and diastolic time intervals during prolonged exercise. (Part 2) / 体力科学

A study was undertaken to determine whether the specific change in the ratio of systolic to diastolic time (QS<SUB>2</SUB>/DT) observed during prolonged exercise<SUP>17)</SUP> is dependent on HR or elapsed time, and also to elucidate the possible relationship between change in QS<SUB>2</SUB>/DT and distance-running performance. Twelve male distance runners were divided into two groups, a high- (HP Group) and a low-performance (LP Group) group, according to their 10, 000-meter running performance. They performed 60-min exercise on a bicycle ergometer at a work load controlled so as to keep the HR at 150 bpm. HR, systolic time intervals (STIs) and DT were calculated from electrocardiogram, phonocardiogram and the derivative of ear densitogram.<BR>In the time course of QS<SUB>2</SUB>/DT, two crests were formed at 2 and 15 min after the start of exercise, and also two troughs were formed at 10 and 20 min. Some of these troughs and crests formed even when HR was kept constant. Patterns of change in QS<SUB>2</SUB>, DT, QS<SUB>2</SUB>/DT and other parameters were similar in the two groups. However, the absolute values of the parameters differed. QS<SUB>2</SUB>, left ventricular ejection time (LVET) and QS<SUB>2</SUB>/DT in the HP Group were lower than those in the LP Group, whereas DT in the HP Group was longer than that in the LP Group.<BR>From these findings, it was concluded that the specific change seen in QS<SUB>2</SUB>/DT during prolonged exercise is dependent not on the HR level but on elapsed time. The changes in STIs and DT during prolonged exercise are thus influenced by the distance-running performance of the subjects.