The effects of aging after coronary arterial bypass grafting on the regulation of cardiac output during upright exercise

We examined the effects of age on cardiac performance and the mechanisms that regulate cardiac output during upright exercise in patients free of myocardial ischemia after coronary revascularization. There were 90 subjects, aged 36 to 75 years, of whom 27 were greater than or equal to 60 years. There were no age-related changes in resting heart rate, systolic blood pressure, left ventricular end-diastolic volume index, left ventricular end-systolic volume index, stroke volume index, cardiac index and left ventricular ejection fraction. There were, however, age-related changes in exercise capacity (y = 20 - 0.21x, r = -0.52, P less than 0.001); exercise heart rate (y = 185 - 1x, r = -0.42, P less than 0.001); exercise end-systolic volume index (y = 11 + 0.46x, r = 0.28, P less than 0.01) and exercise ejection fraction (y = 81 - 0.31x, r = -0.28, P less than 0.01). In a subgroup of 54 patients with comparable exercise workload (27 aged less than 60 and 27 greater than or equal to 60 years), the age-related differences in exercise end-systolic volume index, exercise ejection fraction and exercise cardiac index were not observed, but the exercise heart rate was still higher in the younger patients (y = 168 - 0.76x, r = -0.34, P less than 0.01). Thus, age modifies the compensatory mechanisms that regulate the cardiac output during exercise. Young and old patients alike show increases in end-diastolic volume and ejection fraction to maintain exercise cardiac output. The higher exercise heart rate in the younger subjects suggests a decrease in cardiac responsiveness to adrenergic stimulation associated with aging.     

Left ventricular ejection fraction changes during recovery from treadmill exercise: A preliminary report of a new method for detecting coronary artery disease

To test the value of combining treadmill exercise with radionuclide angiography for detecting exercise-induced left ventricular dysfunction, ejection fractions were calculated at rest, peak supine bicycle exercise, and during three supine post-treadmill recovery periods (2-4 min, recovery 1; 4-6 min, recovery 2; 8-10 min, recovery 3) in ten coronary artery disease patients and eight normal subjects. Both the normal subjects and coronary artery disease patients had normal resting ejection fractions (>0.50). In the normal subjects the mean ejection fraction increased significantly (p<0.005) from rest (0.61 ± 0.03) to peak supine bicycle exercise (0.71 ± 0.04), and the mean ejection fraction also remained significantly higher (p<0.005) at rest than during 10 min post-treadmill exercise. However, the coronary artery disease patients did not significantly change the mean ejection fraction from rest (0.59±0.06) to peak supine bicycle exercise (0.55±0.08), and the average ejection fraction during each one of the post-treadmill recovery periods was not significantly different from rest. At the third recovery period all the normals but no coronary artery disease patients had higher ejection fraction than the resting ejection fraction. We thus conclude that the magnitude of change in ejection fraction from rest to 8-10 min post-treadmill exercise in patients with normal resting ejection fraction may be helpful in identifying those with coronary disease.     

Predictors of the variation of the ejection fraction during exercise in patients with and without coronary heart disease

The aim of this study was to determine the factors influencing the different response of the ejection fraction (EF) of the left ventricle at exercise observed in patients with and without significant coronary heart disease. We have studied 98 patients referred for coronary angiography (82 men, 16 women), of whom 49 patients had a previous myocardial infarction and 71 patients had significant coronary heart disease. Exercise testing was performed and combined with a cardiac blood pool imaging at equilibrium. The variation of the EF between rest and peak exercise (delta EF) was measured. Twelve clinical, exercise-related, isotopic, and coronary arteriographic variables were examined in a linear univariate and statistical analysis. In the univariate regression, seven variables were significant regressors on the delta EF. In the multivariate regression, only four variables were significant regressors on the delta EF. Three independent predictors were found: the rate-pressure product, the ST depression, and the occurrence of a previous myocardial infarction. These three independent predictors reflect the myocardial functional reserve.     

运动试验T波正常化对冠心病诊断价值分析

目的对照平板运动试验与冠状动脉造影结果,探讨T波正常化在诊断冠心病中的价值。方法选择符合标准的84例患者行平板运动试验和冠状动脉造影,观察运动试验引起的T波正常化与冠状动脉造影阳性之间的关系,并分别与运动试验阳性、阴性的冠状动脉造影结果相对比。结果84例中T波正常化11例,其中冠造阳性7例,运动试验阳性53例,其中冠造阳性34例;运动试验阴性20例,其中冠造阳性5例。结论T波正常化者冠造阳性率63.6%,与传统运动试验阳性标准相比较无显著性差异,所以可以将T波正常化作为运动试验阳性的新指标。     

Influence of nebivolol on the cardiovascular hemodynamics during postural changes and isometric exercise

Nebivolol (R67555), a drug with beta 1 receptor antagonizing properties, was administered once daily (5 mg) for 7 days in 10 healthy volunteers. The hemodynamic parameters were measured noninvasively during postural changes (supine, sitting, standing) and during isometric handgrip at 50% maximal voluntary contraction, before and 3, 8, and 23 hours after the first nebivolol intake of 5 mg; the same measurements were done 23 hours after the last intake. Nebivolol lowered arterial blood pressure acutely and chronically due to a decrease in heart rate and cardiac output. The stroke volume seemed to be preserved, while the total peripheral vascular resistance did not change. Nebivolol did not change the orthostatic responses, except that the absolute value was lowered. Nebivolol was unable to prevent the blood pressure increase during isometric handgrip. However, this blood pressure increase was obtained by an increase in the total peripheral vascular resistance and not by an increase in the cardiac output, as observed during control measurements before nebivolol intake.     

Cardiorespiratory and sensory responses to exercise in well-controlled asthmatics

Objectives: The purpose of this study was to evaluate detailed ventilatory, cardiovascular and sensory responses to cycle exercise in sedentary patients with well-controlled asthma and healthy controls. Methods: Subjects included sedentary patients meeting criteria for well-controlled asthma (n?=?14), and healthy age- and activity-matched controls (n?=?14). Visit 1 included screening for eligibility, medical history, anthropometrics, physical activity assessment, and pre- and post-bronchodilator spirometry. Visit 2 included spirometry and a symptom limited incremental cycle exercise test. Detailed ventilatory, cardiovascular and sensory responses were measured at rest and throughout exercise. Results: Asthmatics and controls were well matched for age, body mass index and physical activity levels. Baseline forced expiratory volume in 1?second (FEV₁) was similar between asthmatics and controls (98?±?10 versus 95?±?9% predicted, respectively, p?>?0.05). No significant differences were observed between asthmatics and controls for maximal oxygen uptake (31.8?±?5.6 versus 30.6?±?5.9?ml/kg/min, respectively, p?>?0.05) and power output (134?±?35 versus 144?±?32?W, respectively, p?>?0.05). Minute ventilation (V_E) relative to maximum voluntary ventilation (V_E/MVV) was similar between groups at maximal exercise with no subjects showing evidence of ventilatory limitation. Asthmatics and controls achieved similar age-predicted maximum heart rates (92?±?7 versus 93?±?8% predicted, respectively, p?>?0.05). Ratings of perceived breathing discomfort and leg fatigue were not different between groups throughout exercise. Conclusions: The results of this study indicate that sedentary patients with well-controlled asthma have preserved sensory and cardiorespiratory responses to exercise with no evidence of exercise impairment or ventilatory limitation.     

Assessment of right and left ventricular volumes during upright exercise in normal men

Ventricular volumes were measured in 10 normal subjects by usingtwo independent methods: the stroke volume was obtained by theFick principle and the ejection fraction by multigated radionuclideangiography. Data were collected at rest in the supine and uprightpositions and during an upright exercise test, which includedthree levels of increasing severity. The left and right ventricular end-diastolic volumes (EDV) weremaximal in the supine posture (respectively 183 and 260 ml);at rest both were significantly lower in the upright position(158 and 220 ml). At maximal exercise, the ventricular end-diastolicvolumes were similar (left EDV=147 ml) or slightly lower (rightEDV= 178 ml) than at rest in the upright position. During uprightexercise, the end-systolic volumes (ESV) gradually decreased(P<0.001) from 56 to 34 ml (left ESV) and from 118 to 64ml (right ESV); simultaneously, the left ventricular ejectionfraction (EF) increased from 64 to 77% (P<0.001) and theright ventricular EF increased from 47 to 64% (P<0.001). Since during exercise in the upright position, the end-diastolicvolumes are unchanged or tend to decrease, a Frank-Starlingmechanism cannot be called upon; the cardiac response to uprightexercise is thus mainly based on an increased venous returnand on an increase in myocardial contractility reflected bythe increase in ejection fraction and the decrease in end-systolicvolumes. The methods used in the present study can provide referencevalues for the measurement of absolute ventricular volumes duringexercise by gated equilibrium radionuclide angiography.     

Long-term follow-up by exercise radionuclide angiography of patients after valve replacement for aortic regurgitation

The long-term effects of valve replacement for chronic isolated aortic regurgitation as assessed by first-pass exercise radionuclide angiography have never been reported. We studied 20 males and 5 females before, 15 months postoperatively, and from 29 to 109 (mean 62 +/- 21) months following valve replacement with exercise radionuclide angiography. Mean peak heart rate did not change for the three studies. Peak systolic blood pressure decreased from 201 +/- 42 mmHg to 185 +/- 24 mmHg at 15 months and further declined to 177 +/- 32 mmHg by the long-term study (p less than 0.03). The mean resting left ventricular ejection fraction improved from 44 +/- 15% preoperatively to 57 +/- 18% at 15 months (p less than 0.002) with no further improvement by the long-term evaluation. The postexercise ejection fraction improved from 42 +/- 13% preoperatively to 61 +/- 21% at 15 months (p less than 0.002) also with no change by the long-term study. The duration of exercise improved from 9.7 +/- 4.6 min to 11.9 +/- 3.4 min (p less than 0.03) at 15 months with no additional improvement long term. Improvement in resting and postexercise ejection fraction and in exercise duration is maximal at 15 months. Accuracy and cost containment suggest that assessment of the maximal change in ejection fraction by exercise radionuclide angiography after aortic valve replacement in asymptomatic patients be limited to the 15-month interval.     

Current review of exercise testing: application and interpretation

Exercise testing has changed dramatically in scope over the past 50 years. While initially used to assess functional capacity, it is now also utilized to detect the presence and severity of coronary artery disease (CAD), to evaluate postmyocardial infarction patients at risk for future cardiac events, to screen certain asymptomatic populations for CAD, and to evaluate dysrhythmias, peripheral vascular disease, and lung disease. Dynamic exercise in continuous multistage protocols is most popularly employed because of the more easily measured workload. The safety of exercise testing, its contraindications and termination end points are summarized. The sensitivity of exercise testing ranges between 60 and 70% while specificity has been reported between 85 and 90%. Both sensitivity and specificity are enhanced through use of radionuclide exercise thallium imaging and ventricular angiography.     

运动负荷核素心肌灌注显像对冠心病的诊断价值

目的探讨运动负荷核素心肌灌注显像对冠心病的诊断价值。方法对117例疑有冠心病者,以冠状动脉造影（CAG）结果作为诊断标准,进行心电图平板活动试验和运动负荷核素心肌灌注断层显像两种检查,并将结果行对比分析。结果与CAG结果比较,心电图平板活动试验诊断冠心病的敏感性为60%,特异性为73%;运动负荷核素心肌灌注显像诊断冠心病的敏感性为87%,特异性为69%。结论运动负荷核素心肌灌注显像与心电图平板活动试验比较,敏感性高,特异性相近,对冠心病的无创性诊断具有重要价值。     

Rest and exercise electrocardiograms and radionuclides in patients presenting for cardiac rehabilitation

The rest and exercise ECG, ²⁰¹thallium myocardial scintigram (²⁰¹T1), and radionuclide ventriculography are noninvasive procedures which can be used to evaluate myocardial damage and ischemia. To compare these procedures and to obtain baseline information, 85 male patients with coronary heart disease were evaluated prior to beginning an exercise program. Findings at rest included Q waves or bundle branch block in 54%; 47% had ²⁰¹T1 redistribution defects and 33% an abnormal ejection fraction (EF). Of the 39 patients with normal ECGs, 31 had no ²⁰¹T1 defects and only 1 of these 31 (3%) had an abnormal EF. Abnormal EF or ²⁰¹T1 redistribution defects did not occur in patients without a history of myocardial infarction. Abnormal resting EF occurred in 63% of patients with abnormal versus 7% of those with normal ²⁰¹T1 redistribution scans. Exercise test results included an abnormal ST-segment response in 80%, an abnormal EF response in 65%, and a ²⁰¹T1 ischemic defect in 37%. Twenty patients had exercise-induced ST elevation, and this phenomenon was more related to ventricular aneurysms than to ischemia. ²⁰¹Thallium imaging, radionuclide ventriculography, and the ECG provide results regarding myocardial damage that agree by more than chance, while the exercise-induced ST-segment changes did not agree with the radionuclide indications of exercise-induced ischemia.     

Central hemodynamic responses during serial exercise tests in heart failure patients using implantable hemodynamic monitors

INTRODUCTION: Exercise testing is commonly used in patients with congestive heart failure for diagnostic and prognostic purposes. Such testing may be even more valuable if invasive hemodynamics are acquired. However, this will make the test more complex and expensive and only provides information from isolated moments. We studied serial exercise tests in heart failure patients with implanted hemodynamic monitors allowing recording of central hemodynamics. METHODS: Twenty-one NYHA Class II-III heart failure patients underwent maximal exercise tests and submaximal bike or 6-min hall walk tests to quantify their hemodynamic responses and to study the feasibility of conducting exercise tests in patients with such devices. RESULTS: Patients were followed for 2-3 years with serial exercise tests. During maximal tests (n=70), heart rate increased by 52+/-19 bpm while S(v)O(2) decreased by 35+/-10% saturation units. RV systolic and diastolic pressure increased 29+/-11 and 11+/-6 mmHg, respectively, while pulmonary artery diastolic pressure increased 21+/-8 mmHg. Submaximal bike (n=196) and hall walk tests (n=172) resulted in S(v)O(2) changes of 80 and 91% of the maximal tests, while RV pressures ranged from 72 to 79% of maximal responses. CONCLUSIONS: An added potential value of implantable hemodynamic monitors in heart failure patients may be to quantitatively determine the true hemodynamic profile during standard non-invasive clinical exercise tests and to compare that to hemodynamic effects of regular exercise during daily living. It would be of interest to study whether such information could improve the ability to predict changes in a patient's clinical condition and to improve tailoring patient management.     

Hemodynamic and antianginal effects during rest and exercise of intravenous isradipine, a new dihydropyridine calcium antagonist

In an open randomized study, hemodynamic and antianginal effects of nifedipine and the new dihydropyridine derivative isradipine were compared in patients with stable, angiographically confirmed coronary heart disease. Right heart hemodynamics, systemic arterial blood pressure, ECG, and drug plasma concentrations were measured before medication at rest and exercise, after infusions of increasing doses at rest, and again after treatment at rest and exercise. A linear relationship between serum concentrations and cumulated dosages was obtained for both drugs. At rest, both drugs significantly increased cardiac output and heart rate. The reduction of arterial blood pressure was significantly greater after isradipine (systolic from 148 +/- 3 to 104 +/- 3 mmHg; diastolic from 90 +/- 4 to 58 +/- 2 mmHg) than after nifedipine (systolic 149 +/- 6 to 125 +/- 4 mmHg; diastolic 92 +/- 4 to 76 +/- 3 mmHg). The minimal effective plasma level of isradipine regarding blood pressure reduction was estimated at 5 ng/ml (nifedipine: 10-25 ng/ml). During exercise both medications significantly reduced mean pulmonary artery pressure (isradipine: 40 +/- 3 to 20 +/- 1 mmHg, nifedipine: 37 +/- 4 to 22 +/- 1 mmHg), pulmonary artery wedge pressure (isradipine: 23 +/- 3 to 10 +/- 1 mmHg, nifedipine 24 +/- 3 to 14 +/- 1 mmHg), and diastolic arterial pressure (isradipine: 103 +/- 3 to 73 +/- 4 mmHg, nifedipine: 99 +/- 3 to 91 +/- 2 mmHg), whereas systolic pressure was reduced by only isradipine (189 +/- 4 to 147 +/- 5 mmHg). Neither medication significantly changed electrocardiographic ST depression during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diagnostic utility of metabolic exercise testing in a patient with cardiovascular disease

Disproportionate exercise limitation in patients with cardiovascular disease is a common problem faced by clinical cardiologists and other physicians. Symptoms may be attributed to psychological factors or hypothetical pathophysiological mechanisms that are difficult to confirm clinically. This case report describes how the use of metabolic exercise testing in a 28 year old woman with morphologically and haemodynamically mild hypertrophic cardiomyopathy and severe exercise limitation led to the diagnosis of an alternative cause for the patient's symptoms, namely a primary disturbance of the mitochondrial respiratory chain probably caused by a nuclear encoded gene defect.     

Physical responses to different modes of interval exercise in patients with chronic heart failure--application to exercise training

METHOD: In exercise training with chronic heart failure patients, workingmuscles should be stressed with high intensity stimuli withoutcausing cardiac overstraining. This is possible using intervalmethod exercise. In this study, three interval exercise modeswith different ratios of work/recovery phases (30/60 s, 15/60s and 10/60 s) and different work rates were compared duringcycle ergometer exercise in heart failure patients. Work ratefor the three interval modes was 50% (30/60 s), 70% (15/60 s)and 80% (10/60 s) of the maximum achieved during a steep ramptest (increments of 25 w/l0s) corresponding to 71, 98 and 111watts on average. Metabolic and cardiac responses to the threeinterval exercises were then examined including catecholaminelevels and perceived exertion. Parameters measured during intervalexercise were compared with an intensity level of 75% peak VO₂,determined during an ordinary ramp exercise test (incrementsof l2·5 W. min^–1). RESULTS: () (1) In all three interval modes, VO₂, ventilation and lactate did not increase significantlyduring the course of exercise. Mean values during the last workphase were between 754 ± 30 and 803 ± 46 ml. min^–1for VO₂, between 26 ± 3 and 28 ± 11. min^–1for ventilation and between 1·24 ±0·14and l·29 ± 0·10 mmol.1^–1 for lactate.(2) In mode 10/60 s, heart rate and systolic blood pressureincreased significantly (82 ± 485 ± 4 beats. min^–1;124 ± 5134 ± 5 mmHg; P<0·05 each), whilein mode 15/60 s catecholamines increased significantly (norepinephrine0·804 ± 0·0891·135 ± 0·094nmol. 1^–1; P<0·008; epinephrine 0·136± 0·012 0 193 ± 0·019 nmol. 1^–1;P<0·005). (3) In all three modes, rating of leg fatigueand dyspnoea increased significantly during exercise but remainedwithin the range of values considered ‘very light to fairlylight’ on the Borg scale. (4) Compared to an intensitylevel of 75% peak VO₂, work rate durrng interval work phaseswas between 143 and 221%, while cardiac stress (rate-pressureproduct) was significantly lower (83–88%). CONCLUSION: All three interval modes resulted in physical response in anacceptable range of values, and thus can be recommended.     

Influence of nifedipine on left ventricular dysfunction at rest and during exercise

In order to determine the acute hemodynamic effect of nifedipineat rest and during a standardized supine bicycle exercise test(3 min, 50 W), 14 patients with left ventricular dysfunctionwere studied before and 60 min after taking 30 mg nifedipinesublingually. At rest (R) and during exercise (E), nifedipine produced a significantincrease in left ventricular systolic performance in terms ofstroke volume index (R: 33±6 to 38±4 ml/m², P<0.005;E: 32±5 to 37±6 ml/m², P<0.005) and cardiacindex (R: 2.9±0.4 to 3.6±0.5 l/min/m², P<0.001;E: 4.1±0.7 to 4.9±0.9 l/min/m², P<0.001) dueto a marked reduction in systemic vascular resistance (R: 1517±246to 1129±247 dynes s cm^–5, P<0.001; E: 1170±176to 908±129 dynes s cm^–5, P< 0.01). Pulmonary artery pressures did not change at rest, but droppedsignificantly during exercise, probably due to a shift in theleft ventricular pressure-volume relationship. The findingsof this study indicate that acute hemodynamic improvement canbe achieved by the sublingual use of nifedipine both at restand during exercise in patients with left ventricular dysfunction.Because the hemodynamic response in individual subjects mayvary, careful clinical observation or hemodynamic control isrecommended.     

平板运动试验与冠状动脉造影结果的对照分析

目的:评价平板运动试验在冠心病诊断中的价值。方法:选择262例1月内同时行冠状动脉造影及平板运动试验检查的患者,将这两种检查结果进行对比分析。结果:运动试验诊断冠心病的敏感性60.42％(58/96)、特异性69.88％(116/166)、精确度66.41％(174/262)。在运动时间、运动贮量(最大METs)、峰值血压等方面,冠状动脉造影阳性组与冠状动脉造影阴性组差异明显(P<0.05),双支以上冠脉病变组与单支冠脉病变组对比亦有显著差异(P<0.05)。双支以上病变组平板运动试验阳性率高于单支病变组(P<0.05)。结论:平板运动试验是目前诊断冠心病较理想的非创伤性检查方法,通过多项指标综合判断可以初步推测病变程度。     

高通气综合征患者运动通气应答的研究

目的探讨高通气综合征(HVS)患者的运动通气应答。方法16例HVS患者和18名健康志愿者进行负荷连续递增的运动心肺功能试验,观察整个试验过程中气体交换指标和通气方式。结果①静息初始(t=0min)HVS患者的潮气末二氧化碳分压(PetCO2)、二氧化碳通气当量(·VE/·VCO2)、潮气量(VT)和呼吸频率(f)与对照组比较,差异无统计学意义(P>0.05);静息结束时(t=5min)和最大运动时,HVS患者的上述指标与对照组比较,差异有统计学意义(P<0.05)。②HVS患者的最大氧耗量(V.O2max)、最大运动功率(Wmax)和最大氧脉搏(O2pulsemax)与对照组比较,差异无统计学意义(P>0.05);最大运动时的Borg指数(Borgmax)、呼气末肺容量(EELV)和吸气末肺容量占肺总量百分比(EILV/TLC%)与对照组比较,差异有统计学意义(P<0.05)。③运动恢复期,HVS患者PetCO2恢复曲线的斜率(S-PetCO2)低于对照组,差异有统计学意义(P<0.01)。结论HVS患者在心肺运动试验中呈现高通气状态,采取小潮气量、快呼吸频率和低肺容量位的通气方式。