Peak exercise oxygen uptake and left ventricular systolic and diastolic function and arterial mechanics in healthy young men

Echocardiography can be used to estimate myocardial contractility by the assessment of the circumferential end-systolic stress-corrected left ventricular (LV) fractional shortening measured at midwall level (stress-corrected MWS). Whether stress-corrected MWS at rest predicts exercise peak oxygen uptake (peak O₂) is unknown. Also, it is not known whether the propagation rate of the early LV filling wave (E wave propagation rate, _p), a new pre-load insensitive index of LV diastolic function, and echocardiographically assessed indices of arterial stiffness correlate to peak O₂. Accordingly, we performed echocardiographic studies and exercise tests with respiratory gas analysis in 15 young healthy male subjects (mean age 27 years, range 18–36). Neither stress-corrected-MWS (r=0.20, P=NS) nor ejection fraction (r=–0.05, P=NS) correlated significantly with peak O₂. Adjustment for age and resting heart rate had no effect on the results. In separate multiple regression models adjusting for standard covariates (age, LV size and heart rate), peak O₂ correlated with _p (beta=0.98, P<0.01), as well as with E/A (beta=0.85, P<0.01), and with the isovolumic relaxation time (indicator of LV relaxation) (beta=–0.59, P<0.05). Arterial stiffness indices showed no significant relation to peak O₂. We conclude that in young healthy male subjects, resting myocardial contractility and arterial stiffness are not significant correlates of peak O₂, whereas LV diastolic function, and in particular _p, influences the variability of peak O₂.     

Plasma adrenocorticotrophin and cortisol responses to acute hypoxia at rest and during exercise

Summary Plasma adrenocorticotrophin (ACTH) and cortisol (F) concentrations were studied in six male subjects under normoxic (N) and acute hypoxic (H) conditions (altitude 3000 m) in a hypobaric chamber. Comparisons were made at rest, at 15, 30, and 60 min of exercise (65% ), and after a 10 min recovery period. Mean (±SE) resting plasma ACTH levels were significantly higher in H (18.6±5.7 pmol · l^–1) than in N (9.6±1.6 pmol · l^–1) but no difference in resting plasma cortisol was observed between the two conditions. Both plasma ACTH and F concentrations were significantly increased at 60 min of exercise and during the recovery period under normoxic conditions. Hypoxia did not affect the ACTH response to exercise but reduced cortisol elevation. The changes in plasma cortisol concentration from rest to exercise were significantly correlated to ACTH under normoxic (r=0.89,p<0.001) but not under hypoxic (r=0.43, NS) conditions. Plasma lactate concentration was higher at the end of exercise in hypoxia (p<0.01), and no correlation existed between plasma lactate and ACTH levels. These observations provide further evidence that at sea level the increase in plasma cortisol levels during exercise is the result of ACTH-induced steroidogenesis. The responses observed at rest and during exercise in hypoxia suggest that adrenal sensitivity for ACTH may be altered.     

急进高原后男性官兵心功能的变化及其与AMS的关系

目的:评价驻平原官兵急进高原前后心功能的变化情况并探讨其与急性高山病(AMS)的关系。方法:采用超声心动图评价42名健康青年男性官兵进入高原前及快速进入高原后(3 658 m,3 d)的心脏功能,同时观察心率、血压和血氧饱和度等生理指标的变化,以及进入高原后AMS的发病情况。结果:与进入高原前相比,青年男性官兵急进高原后,左房收缩末期内径和左室舒张末期内径显著减小,右房收缩末期内径显著减小,右室流出道和肺动脉内径显著增宽,射血分数显著增大,心输出量显著增多,肺动脉收缩压及平均肺动脉压显著增高,二尖瓣E峰流速显著降低(P0.05)。进入高原后,42人中有15人发生AMS(AMS组),27人未发病(non-AMS组)。比较2组官兵在平原的心功能发现,AMS组的主动脉窦部内径和左室舒张末期内径显著小于non-AMS组,肺动脉收缩压显著高于non-AMS组。比较2组官兵进入高原后的心功能发现,AMS组左房收缩末期内径显著小于nonAMS组(P0.05)。AMS评分与进入高原前的心输出量呈显著负相关性(r=-0.3814,P0.05)。结论:青年男性官兵从平原快速进入高原后,右心功能受损合并左心功能代偿;在平原运用超声心动图进行肺动脉收缩压及心输出量的检查有助于AMS易感人群的筛选。     

二维超声心动图和M型超声心动图评价左心室扩大患者左心室收缩功能的对比研究

目的评价二维超声心动图（2DE）法和M型超声心动图（ME）法测量心瓣膜病中重度二尖瓣和（或）主动脉瓣反流（VR）、扩张型心肌病（DCM）和缺血性心肌病（ICM）患者左心室收缩功能相关指标的一致性及其影响因素。方法用2DE和ME同时测量100例左心室扩大患者（VR35例、DCM32例和ICM33例）的左心室舒张末期内径（LVEDD）、左心室舒张末期容积（LVEDV）和左心室射血分数（LVEF）,分别记为LVEDD2DE、LVEDDME、LVEDV2DE、LVEDVME、LVEF2DE和LVEFME。结果①患者的LVEDD2DE与LVEDDME、LVEDV2DE与LVEDVME差异有统计学意义,LVEF2DE与LVEFME差异无统计学意义,且具有良好的相关性,r=0．869;②组内比较：3组的LVEDD2DE与LVEDDME差异均有统计学意义,VR组LVEDV2DE与LVEDVME差异无统计学意义,其他两组差异有统计学意义,3组的LVEF2DE与LVEFME差异无统计学意义;③组间比较：LVEDD2DE在DCM组与ICM组之间差异有统计学意义,在VR组与ICM组之间差异也有统计学意义,LVEDDME、LVEDV2DE。和LVEDVME有相同的结果,LVEF2DE在3组间差异均有统计学意义,LVEFME在3组间差异也均有统计学意义,2DE和ME法均得到LVEDVVR≈LVEDVDCM〉LVEDVICM和LVEFDCM〈LVEFICM〈LVEFVR的一致结论;④按LVEDD2DE分为〈80mm大左心室组和≥80mm巨大左心室组,两组的LVEDV2DE与LVEDVME差异有统计学意义,LVER2DE与LVEFME各组差异无统计学意义。结论二维法和M型超声评价VR、DCM和ICM患者左心室收缩功能的指标中LVEF一致性较好．较少受左心室形状及节段性室壁运动异常的影响。2DE和ME均得出VR组与DCM组左心室增大的程度相近．但LVEF减低的程度却不同．而ICM组左心室增大的程度小于前两组。但LVEF却较VR组减低明显。     

Functional changes in left ventricular hypertrophy: diagnosis of impaired diastolic function in patients with hypertension

Summary Left ventricular hypertrophy is usually associated with impaired left ventricular diastolic function which can be characterised by an altered pressure volume relationship. Since diastolic flow velocities are closely related to the difference in pressure between the left atrium and left ventricle, parameters of diastolic function can be determined by Doppler echocardiography. However, the pressure difference is additionally influenced by factors which have no relation to left ventricular diastolic function. These include preload, afterload, inotropy, heart rate and left ventricular systolic function. Despite these limitations, Doppler echocardiography is a valuable tool to diagnose therapeutic effects on diastolic function in patients with left ventricular hypertrophy.     

Non‐invasive assessment of cardiac output during exercise in healthy young humans: comparison between Modelflow method and Doppler echocardiography method

Aims: The Modelflow method can estimate cardiac output from arterial blood pressure waveforms using a three‐element model of aortic input impedance (aortic characteristic impedance, arterial compliance, and systemic vascular resistance). We tested the reliability of a non‐invasive cardiac output estimation during submaximal exercise using the Modelflow method from finger arterial pressure waveforms collected by Portapres in healthy young humans. Methods: The Doppler echocardiography method was used as a reference method. Sixteen healthy young subjects (nine males and seven females) performed a multi‐stage cycle ergometer exercise at an intensity corresponding to 70, 90, 110 and 130% of their individual ventilatory threshold for 2 min each. The simultaneous estimation of cardiac output (15 s averaged data) using the Modelflow and Doppler echocardiography methods was performed at rest and during exercise. Results and Conclusion: The Modelflow‐estimated cardiac output correlated significantly with the simultaneous estimates by the Doppler method in all subjects (r = 0.87, P < 0.0001) and the SE of estimation was 1.93 L min^?1. Correlation coefficients in each subject ranged from 0.91 to 0.98. Although the Modelflow method overestimated cardiac output, the errors between two estimates were not significantly different among the exercise levels. These results suggest that the Modelflow method using Portapres could provide a reliable estimation of the relative change in cardiac output non‐invasively and continuously during submaximal exercise in healthy young humans, at least in terms of the relative changes in cardiac output.     

The effect of acute hypoxia on left ventricular function during exercise

The effect of acute hypoxia on the human left ventricular function during exercise was evaluated by 2D and Doppler echocardiography on 11 healthy male college students. Each subject completed 6-min moderate intensity (100 W) supine cycling exercises in normoxia and hypoxia, respectively. The concentration of inspired O₂ was adjusted to keep arterial hemoglobin O₂ concentration (SpO₂) at 88–92% during hypoxia. Doppler indices obtained were compared between normoxia and hypoxia. The left ventricular myocardial diastolic function was increased during exercise in hypoxia compared with normoxia. The peak velocity of early filling wave increased at rest (P < 0.05) and during exercise (P < 0.05 at second minute, and P < 0.01 at sixth minute) in hypoxia. The heart rate (P < 0.01) and cardiac output (P < 0.001) were elevated markedly at rest during hypoxia. The left ventricular systolic function variables, such as stroke volume, ejection fraction, and end-systolic volume were relatively unaltered during hypoxia compared with normoxia. The results suggest that acute hypoxia increases the left ventricular myocardial diastolic function during moderate intensity supine cycling exercise without affecting the systolic function.     

应用二尖瓣环运动速度和时间指标评价冠心病患者左室整体舒张功能

目的：应用脉冲多普勒组织成像（DTI）定量分析并比较心绞痛与心肌梗死（心梗）患者二尖瓣环长轴方向上舒张运动速度和时间变化，探讨其评价左室整体舒张功能异常的价值。方法：冠心病心绞痛组16例、心梗组34例、对照组16例。记录二尖瓣环侧壁、间隔、前壁和下壁的运动频谱。测量舒张早、晚期峰值运动速度及其比值，舒张早期波开始时间、达峰时间和局部等容舒张时间，并计算4个位点的均值，分别以Em、Am、Em/Am、QEm、TEm和IVRTm表示。结果：心绞痛组和心梗组Em和Em/Am显著低于对照组（P<0.01），心梗组Em又低于心绞痛组（P<0.01）；心绞痛组和心梗组QEm、TEm及IVRTm显著长于对照组（P<0.01或P<0.05），心梗组IVRTm又长于心绞痛组（P<0.01）；IVRTm与Em呈显著负相关（r=-0.64, P<0.01）。结论：脉冲DTI所测Em、Em/Am、QEm、TEm及IVRTm均可反映冠心病患者左室整体舒张功能异常，Em和IVRTm尚可反映心肌缺血损害的严重程度。     

Left ventricular performance during prolonged exercise and early recovery in healthy subjects

The effect of semi-supine long lasting exercise to exhaustion [61 (SD 10) min] on left ventricular systolic performance was studied by echocardiography in 16 young healthy volunteers. During the incremental phase of exercise, the ejection fraction increased from 65.2 (SD 4.1)% to 80.1 (SD 4.8)% (P<0.0001), then it levelled off up to the end of exercise [81.7 (SD 4.4)%,P<0.0001 vs rest]. During recovery, the ejection fraction rapidly and steadily decreased to a value similar to that at rest [66.1 (SD 5.0)%, n.s.). A similar pattern was shown by the systolic blood pressure/end-systolic volume coefficient, which rose from 3.2 (SD 0.8) mmHg · ml^–1 to 7.5 (SD 2.7) mmHg · ml^–1 (P < 0.0001) in the initial phase and subsequently did not change until the end of exercise [7.0 (SD 2.2) mmHg · ml^–1,P<0.0001 vs rest], to fall sharply after the cessation of exercise [2.9 (SD 1.1) mmHg · ml^–1 at the 10th min, n.s. vs rest]. Exercise and recovery indices of left ventricular performance were not correlated with exercise duration, maximal heart rate and increase in free fatty acids. The present results indicated that, after the initial increase, left ventricular performance remained elevated during prolonged high intensity exercise and that conclusions on exercise cardiac performance drawn from postexercise data can be misleading.     

Shape of the left ventricle and its computer modelling

A simple computer program was made to draw different left ventricle shapes in order to support the theory of elongation and to get a visual presentation of the shape of the left ventricle. Experimental data, obtained from echocardiography and Simpson's rule, were used for this program. The results yielded different shapes under different physiological circumstances, indicating the sensitivity of the method. It was concluded that these figures (shapes) support the use of elongation as a shape index.     

Influence of sildenafil on lung diffusion during exposure to acute hypoxia at rest and during exercise in healthy humans

We sought to determine the influence of sildenafil on the diffusing capacity of the lungs for carbon monoxide (DL_CO) and the components of DL_CO (pulmonary capillary blood volume V _c, and alveolar–capillary membrane conductance D _M) at rest and following exercise with normoxia and hypoxia. This double-blind placebo-controlled, cross-over study included 14 healthy subjects (age = 33 ± 11 years, ht = 181 ± 8 cm, weight = 85 ± 14 kg, BMI = 26 ± 3 kg/m², peak normoxic VO₂ = 36 ± 6 ml/kg, mean ± SD). Subjects were randomized to placebo or 100 mg sildenafil 1 h prior to entering a hypoxic tent with an FiO₂ of 12.5% for 90 min. DLCO, V _c, and D _M were assessed at rest, every 3 min during exercise, at peak exercise, and 10 and 30 min post exercise. Sildenafil attenuated the elevation in PAP at rest and during recovery with exposure to hypoxia, but pulmonary arterial pressure immediately post exercise was not different between sildenafil and placebo. Systemic O₂ saturation and VO_2peak did not differ between the two conditions. DL_CO was not different between groups at any time point. V _C was higher with exercise in the placebo group, and the difference in D _M between sildenafil and placebo was significant only when corrected for changes in V _c (D _M/V _c = 0.57 ± 0.29 vs. 0.41 ± 0.16, P = 0.04). These results suggest no effect of sildenafil on DLCO, but an improvement in D _M when corrected for changes in V _c during short-term hypoxic exposure with exercise.     

Analog simulation of two clinical conditions: (1) acute left ventricle failure; (2) exercise in patient with aortic stenosis

A computer analysis of an equivalent electronic circuit is developed. Thus it is possible to simulate the human cardiovascular system, its negative feedback loops (including the control of venous tone, of myocardial contractility, and of heart rate) and negative intrathoracic pressure. If the simulated cardiovascular system is acted upon by various disturbances their consequences can be studied in detail. The consequences of two disturbances are studied by simulation: (i) acute left ventricular failure and (ii) exercise (decreased peripheral resistance) in aortic stenosis. However, prior to the simulation of the latter, a relatively complex condition, two additional procedures are implemented, i.e. simulations of (iii) increased sympathetic tone and of (iv) aortic stenosis are performed. Simulation of exercise (decreased peripheral resistance) in aortic stenosis is also compared with data observed in patients. Results show that, by using the present equivalent circuit, conditions described above can be qualitatively and to some extent quantitatively well simulated.     

Specific function and morphology of the right ventricle of the heart during ischemic injury of the left ventricle

Focal ischemia of the left ventricular myocardium was modeled by surgical ligation of the descending branch of the left coronary artery at the junction of the lower and middle thirds of this artery in anesthetized rabbits. Contractility and morphological characteristics of the right ventricular myocardium were evaluated 24, 72, and 120 h after treatment. Significant morphofunctional changes in the right ventricle manifested in the development of severe extracellular edema and increase in the area of damaged and destroyed myofibrils. However, the actual and maximum intraventricular pressure remained unchanged under these conditions. The degree of cardiomyocyte apoptosis increased on day 1, but returned to normal in the follow-up period. Our study demonstrated high sensitivity of the right ventricle to left ventricular dysfunction and early activation of compensatory mechanisms. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 145, No. 4, pp. 392–394, April, 2008     

Influence of hypoxic ventilatory response on arterial O2 saturation during maximal exercise in acute hypoxia

The aim of this study was to evaluate the influence of peripheral chemosensitivity estimated by hypoxic ventilatory response (HVR) on arterial oxygen saturation (S _aO₂) during maximal exercise in acute hypoxia. A group of 16 healthy men performed maximal exercise in two conditions of partial pressure of inspired oxygen (P _IO₂/149 and 70 mm Hg, 19.8 and 9.3 kPa). Measurements of maximal oxygen uptake ( ) andS _aO₂ using an ear-oximeter were carried out in both conditions ofP _IO₂. The HVR was measured at rest by progressive isocapnic hypoxia and evaluated by the slope of the linear regression between the ventilatory flow ( ) and theS _aO₂ ( ). The absolute value of HVR (in litres per minute per percentage saturation per kilogram) was correlated to maximal expired (r = 0.85,P < 0.001), ventilatory equivalent for CO₂ (r = 0.83,P < 0.001) andS _aO₂ (r = 0.60,P < 0.05) determined during maximal exercise in hypoxia: a significant decrease in (37%) andS _aO₂ (32%) forP _IO₂ of 70 mm Hg (9.3 Pa) was observed (P < 0.001). The correlation between the decline of and arterial oxygen desaturation failed to reach statistical significance (r = 0.47, P = 0.1). The present findings indicated that the peripheral ventilatory chemosensitivity contributed to the interindividual variability of andS _aO₂ during maximal exercise in acute hypoxia.     

Static morphometric bases for CT identification and evaluation of the outflow chamber of the left ventricle. Preliminary study in formalin-fixed heart

Summary A static morphometric study of the outflow chamber of the left venticle (OCLV) was investigated in a series of 10 formalin-fixed hearts. A spatial reconstruction of the shape and the volume of the OCLV was carried out by means of a Somaton Plus TR4 Tomodensitometer (Siemens). The technic allows evaluation of the surface of the aortic and the mitral orifices and visualization of the three-dimensional OCLV and LV morphology, as well as calculation of their volumes. The limits of the technic in the dynamic study of the OCLV are presented.

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Bases morphométriques statiques d'identification et d'évaluation de la chambre de chasse du ventricule gauche par tomodensitométrie. Etude préliminaire sur le coeur formolé

Résumé Les auteurs présentent sur une série de 10 coeurs formolés une étude statique morphométrique de la chambre de chasse du ventricule gauche (CCVG). La reconstruction spatiale de la forme et du volume de la CCVG est réalisée grâce au Scanner Somaton Plus (Siemens). La technique permet d'évaluer la surface des orifices aortique et mitral, de visualiser la morphologie tridimensionnelle du VG et de la CCVG et de calculer leur volume. Les auteurs souligenent les limites de la technique présentée dans l'étude dynamique de la CCVG.

     

Coronary arterial territories of the left ventricle: Extension and exclusivity

Summary Ninety human hearts obtained from autopsies were used. The methods applied were post-mortem angiography, dissection and the construction of an arterial map by segments, according to the classification of Selvester et al. It was shown that the arteries which have the greatest extension are the anterior interventricular and circumflex aa., while irrigation by the right coronary artery is only moderate, except in the segments of the inferior wall. Differences in the perfusion territories of the main coronary arteries and between the patterns of arterial irrigation of the left ventricle (segmental pattern and grouped pattern) were found. Finally, we define risk groups on the basis of the proportion of the ventricular mass irrigated by each artery, which are of practical interest from the clinical, prognostic and therapeutic points of view.

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Territoires artériels coronaires du ventricule gauche : extension et caractère exclusif

Résumé 90 coeurs humains issus d'autopsies ont été utilisés. Les méthodes utilisées furent l'angiographie post-mortem, la dissection et la cartographie artérielle par segments, selon la classification de Selvester et al. De l'ensemble de la série, on peut conclure que les artères qui ont la plus grande extension sont l'a. interventriculaire antérieure et l'a. circonflexe, tandis qu'elle est modérée pour l'a. coronaire droite, sauf dans les segments de la paroi inférieure. Des différences ont été trouvées dans les territoires de perfusion des artères coronaires principales, entre les types d'irrigation artérielle du ventricule gauche (type segmentaire et type groupé). Finalement, nous définissons des groupes à risques sur la base de la proportion de masse ventriculaire irriguée par chaque artère, ce qui pourrait être d'un intérêt pratique du point de vue clinique, pronostique et thérapeutique.

     

实时三维超声心动图和组织多普勒评价扩张型心肌病左心室舒张早期同步性的相关性研究

目的 比较实时三维超声心动图和组织多普勒显像在分析正常人和扩张型心肌病(DCM)患者的左心室舒张早期同步性的临床价值.方法 选取37例DCM患者(DCM组),其中男性25例,女性12例;年龄46～87岁,平均年龄65.4岁(标准差10.0岁).健康志愿者27例(对照组),其中男性19例,女性8例;年龄50～72岁,平均年龄60.3岁(标准差9.7岁).同时进行实时三维超声心动图和组织多普勒检查,测定舒张早期二尖瓣频谱蜂值与二尖瓣环速度峰值之比(E/E')、收缩末期到二尖瓣开放图像时的舒张容积占整个舒张容积的比值(EDV早/EDV)、收缩末期到二尖瓣开放图像时的时间占整个心动周期的比值(T早/T),左心室16节段、12节段心肌舒张早期容积的时间标准差(Tedv 16-SD、Tedv 12-SD)及左心室12节段的组织速率舒张峰值时间的标准差(Te 12-SD),计算舒张早期容积的时间最大差值(Tedv-Dif),评价左心室舒张早期同步性.结果 DCM组舒张功能明显减低,E/E'、EDV早/EDV、T早/T显著大于对照组(P＜0.05).DCM组Te 12-SD、Tedv 16-SD、Tedv 12-SD均明显大于对照组(均P＜0.01).Tedv 16-SD、Tedv 12-SD与Te 12-SD的相关性分别为r=0.879和r=0.773(均P＜0.01);Tedv 16-Dif、Tedv 12-Dif与Te 12-Dif的相关性分别为r=0.850和r=0.718(均P＜0.01).结论 实时三维超声心动图和组织多普勒两种方法均能够评价左心室舒张早期同步性,两种方法的评价结果具有很好的相关性.     

Doppler echocardiographic analysis of diastolic left ventricular function in dialysis patients and its relation to intradialytic hypotension

Summary Doppler echocardiography was used to evaluate left ventricular relaxation and filling in 20 patients on chronic maintenance hemodialysis. In comparison with 11 normal controls hemodialysed patients showed a marked prolongation of isovolumic relaxation period (83±23 ms vs 67±11 ms,P<0.01). Peak velocity of early diastolic filling was similar in both groups, but peak velocity of late ventricular filling due to atrial contraction was substantially increased in dialysis patients (66±23 cm/s vs 37±7 cm/s,P<0.01) and the ratio late to early peak velocity was significantly enlarged (0.97±0.35 vs 0.58±0.19,P<0.01). Although left ventricular mass index, as determined by Echo, was markedly increased in dialysis patients, no significant correlation was found between ventricular mass and indexes of diastolic function. When patients were divided into two groups on the basis of development of hypotension during dialysis clinical and echocardiographic characteristics were similar, although patients with dialysis hypotension (n=9) were significantly older (53±9 years) than normotensiv patients (n=11, 42±14 years,P<0.05). Indexes of diastolic function showed a great overlap between the two groups, but ratio late to early peak velocity was significantly greater in patients with intradialytic hypotension (1.13±0.35 vs 0.83±0.32,P<0.05). It is concluded that dialysis patients exhibit significant alterations of left ventricular relaxation and diastolic filling as assessed by Doppler echocardiography which might be independent of left ventricular hypertrophy. Impaired diastolic function might contribute to intradialytic hypotension.Abbreviations DEF deceleration of early diastolic flow - IVRP isovolumic relaxation period - peakA peak velocity of late left ventricular filling - peakE peak velocity of early left ventricular filling