Left ventricular function during exercise testing and training

The Effect of a Hyperdynamic Circulation on Tissue Doppler Values: A Simulation in Young Adults during Exercise

Left ventricular tissue Doppler imaging (TDI) velocities are used to monitor systolic and diastolic function, but it is not known how these may change in a hyperdynamic circulation, as often occurs in anesthesia and critical care medicine. Twenty-six healthy young volunteers were recruited and left ventricular systolic and diastolic tissue Doppler velocities measured at rest, light exercise, strenuous exercise, and recovery (10 minutes after exercise). At rest, TDI velocities significantly decreased from base to apex (P < .001). Within basal, mid, and apical sections, systolic and diastolic peak velocities differed between segments (P < .05), except for systolic middle (P = .094) and late diastolic apical velocities (P = .257). Basal septal velocities differed from basal lateral, for systolic (P = .041) but not diastolic peak values. Inferobasal radial values differed from basal lateral values for both systolic and diastolic velocities (P < .05). Both systolic and diastolic TDI velocities increased significantly in all segments in a proportionate manner with a hyperdynamic circulation.

Effect of Warm-Up on Cycle Time Trial Performance

PURPOSE

This study was designed to determine the effect of warm-up on 3-km cycling time trial (TT) performance, and the influence of accelerated VO(2) kinetics on such effect.

METHODS

Eight well-trained road cyclists, habituated to 3-km time trials, performed randomly ordered 3-km TT after a) no warm-up (NWU), b) easy warm-up (EWU) (15 min comprised of 5-min segments at 70, 80, and 90% of ventilatory threshold (VT) followed by 2 min of rest), or c) hard warm-up (HWU) (15 min comprised of 5-min segments at 70, 80, and 90% VT, plus 3 min at the respiratory compensation threshold (RCT) followed by 6 min of rest). VO(2) and power output (SRM), aerobic and anaerobic energy contributions, and VO(2) kinetics (mean response time to 63% of the VO(2) observed at 2 km) were determined throughout each TT.

RESULTS

Three-kilometer TT performance was (P < 0.05) improved for both EWU (266.8 +/- 12.0 s) (-2.8%) and HWU (267.3 +/- 10.4 s) (-2.6%) versus NWU (274.4 +/- 12.1 s). The gain in performance was predominantly during the first 1000 m in both EWU (48% of gain) and HWU (53% of gain). This reflected a higher power output during the first 1000 m in both EWU (384 W) and HWU warm-up (386 W) versus NWU (344 W) trials. The mean response time was faster in both EWU (45 +/- 10 s) and HWU (41 +/- 12 s) versus NWU (52 +/- 13 s) trials. There were no differences in anaerobic power output during the trials, but aerobic power output during the first 1000 m was larger during both EWU (203 W) and HWU (208 W) versus NWU (163 W) trials.

CONCLUSIONS

During endurance events of intermediate duration (4-5 min), performance is enhanced by warm-up irrespective of warm-up intensity. The improved performance is related to an acceleration of VO(2) kinetics.

Attenuated cardiovascular reserve during prolonged submaximal cycle exercise in healthy older subjects

OBJECTIVE

The goal of this study was to determine the effect of age on the hemodynamic response to prolonged submaximal aerobic exercise in healthy volunteers.

BACKGROUND

Reductions in peak work rate, heart rate (HR), and left ventricular (LV) emptying but higher blood pressure (BP) and systemic vascular resistance occur in healthy older versus younger humans during short bursts of graded maximal aerobic exercise. However, the effect of aging on the cardiovascular response to prolonged exercise at submaximal work rates typical of daily aerobic activities remains unknown.

METHODS

We evaluated cardiovascular performance throughout prolonged submaximal upright cycle ergometry in 40 carefully screened healthy untrained volunteers, 8 men and 12 women <50 years old, mean = 37 +/- 8 years (younger), and 10 men and 10 women >/=50 years old, mean = 66 +/- 9 years (older), during upright cycle exercise at 70% of peak cycle oxygen consumption (VO(2)) to exhaustion or a maximum of 120 min. Cardiac volumes were acquired by gated blood pool scans with (99m)Tc at rest and every 10 min throughout exercise.

RESULTS

Duration of exercise was similar in younger ([81 +/- 28 min] versus older [71+/- 29 min] subjects, p = NS). At 10 min of exercise in the steady state, older subjects demonstrated lower VO(2) (1.1 +/- 0.2 l/min vs. 1.3 +/- 0.3 l/min) and lower HR (118 +/- 17 vs. 135 +/- 11 beats/min, p < 0.001) but larger end-diastolic (80 +/- 11 ml/m(2) vs. 73 +/- 8 ml/m(2), p = 0.03) and end-systolic volume index (ESVI) 20 +/- 6 ml/m(2) vs. 17 +/- 4 ml/m(2), p < 0.05) than younger ones. Between 10 min and exercise termination, with VO(2) held constant in both groups, increases in HR (14.0 +/- 12.4 beats/min vs. 5.9 +/- 11.5 beats/min, p = 0.04), cardiac index (1.6 +/- 1.0 l/min/m(2) vs. 0.8 +/- 1.1 l/min/m(2), p = 0.03), and LV ejection fraction (7.1 +/- 4.0% vs. 2.9 +/- 4.4%, p = 0.003) were greater in younger than older subjects, respectively, as was the reduction in ESVI (-5.1 +/- 3.0 ml/m(2) vs. -1.8 +/- 3.3 ml/m(2), p = 0.002), despite similar declines in systolic BP (-12.3 +/- 6.3 mm Hg vs. -12.1 +/- 15.0 mm Hg, p = NS).

CONCLUSIONS

Thus, age-associated deficits in chronotropic and LV systolic reserve performance occur during prolonged submaximal upright cycle ergometry, analogous to those observed during graded maximal exercise.

Hemodynamic responses during aerobic and resistance exercise

PURPOSE

Resistance training has become an accepted part of cardiac rehabilitation programs. Because of the potential for a high afterload to have a negative impact on left ventricular function, there has been concern regarding the safety of resistance training for patients with congestive heart failure.

METHODS

This study addressed this concern by studying 12 healthy volunteers, 12 patients with stable coronary artery disease, and 12 patients with stable congestive heart failure during upright cycling at 90% of ventilatory threshold, and during one set of 10 repeated leg presses, shoulder presses, and biceps curls at 60% to 70% of 1-repetition maximum. Left ventricular function was measured by echocardiography.

RESULTS

The pattern of changes in heart rate, blood pressure, left ventricular ejection fraction, wall thickness, and left ventricular internal diameters was similar across all three groups of subjects, although there were large differences in absolute values. Despite elevations in diastolic and mean arterial pressures during resistance exercise, there was no evidence of significant rest-to-exercise deterioration in left ventricular function during leg press (ejection fraction, 60%-59%, 56%-55%, and 38%-37%), shoulder press (66%-65%, 59%-53%, and 38%-35%), or biceps curls (63%-58%, 53%-54%, and 35%-36%), as compared with cycle ergometry (63%-69%, 51%-57%, and 35%-42%) in the healthy control subjects, the patients with coronary artery disease, and the patients with congestive heart failure, respectively.

CONCLUSIONS

Left ventricular function remains stable during moderate-intensity resistance exercise, even in patients with congestive heart failure, suggesting that this form of exercise therapy can be used safely in rehabilitation programs.

Short-term physical training improves vasodilatory capacity in cardiac patients

There have been no previous studies that clearly demonstrate the effects of training on the relation between exercise capacity and vasodilatory capacity in skeletal muscle. This study was performed to clarify the effects of short-term, moderate-intensity physical training on exercise tolerance and vasodilatory capacity in cardiac patients. We studied 21 patients after acute myocardial infarction, coronary artery bypass grafting, or valve replacement. Each patient performed symptom-limited incremental exercise tests before and after a 2-week training program of moderate-intensity exercise. A cycle ergometer was used for both the training and exercise tests. Blood pressure measurement and respiratory gas analysis were continuously performed during the tests. Cardiac output was also measured using a dye-dilution method at rest and every 2 minutes during incremental exercise. Reactive hyperemic calf blood flow was measured at rest. After the training program, the subjects attained a significant decrease in systemic vessel resistance and significant increases in oxygen uptake and cardiac output at peak exercise. Changes in reactive hyperemic calf blood flow were significantly correlated with the changes in cardiac output, systemic vascular resistance, and the kinetics of oxygen uptake during warm-up exercise. By improving the peripheral vasodilatory capacity in these patients, short-term, moderate-intensity physical training was found to improve the cardiovascular adaptation not only at peak exercise, but also during the onset of exercise.

Physical activity and exercise training prescriptions for patients

The dominant outcome from exercise prescription is an increase in various markers of exercise capacity. A very large group of studies have demonstrated that the VO2max is increased in response to exercise performed according to well-accepted principles of exercise prescription. Other markers of exercise capacity, such as the VT, also improve substantially following exercise training. Finally, improvement in exercise capacity is generally related to improved quality of life, particularly in patients with exercise capacity limited by various disease processes. Beyond the specific physiologic gains from training, exercise contributes to a better overall clinical outcome. Although there are few data conclusively demonstrating that exercise independently causes favorable changes in other risk factors, it should be recognized that exercise can contribute indirectly to modulation of other risk factors. Exercise represents positive health advice. Since most of our other recommendations to patients are in the nature of negative advice (e.g., don't smoke, don't eat high-fat foods), and since people are infamous for ignoring negative advice, the value of using a positive recommendation that may indirectly lead the patient to discontinue bad behaviors can hardly be overstated.

Thallium gated SPECT: relation between immediate post-stress evolution of ejection fraction and severity of perfusion pattern

BACKGROUND AND AIMS

A significant decrease of left ventricular ejection fraction (LVEF) at stress has been reported with 99Tc(m) gated single-photon emission computed tomography (gSPECT) in severe myocardial stunning up to 1 h after exercise. This study was designed to show whether 201Tl gSPECT can measure LVEF evolution from rest to stress in routine examination and give additional information to perfusion interpretation since acquisition starts immediately after stress test.

METHODS

Post-exercise and rest 201Tl gSPECT were performed in 187 patients with suspected coronary artery disease. Myocardial perfusion was quantified by 20-segment analysis. Patients were divided into four groups according to their summed perfusion score, reversibility rate and electrocardiographic findings, i.e. in order of severity: I = normal perfusion, II = fixed defect owing to a myocardial infarction, III = full reversible ischaemia, and IV = partial reversible ischaemia. LVEF was calculated by Germano's automatic algorithm.

RESULTS

Normal subjects (n = 29) and infarcted patients (n = 34) showed a significant LVEF increase between rest and stress, +7 +/- 9% and +5 +/- 7% respectively. In full reversible ischaemic patients (n = 46), stress LVEF showed no increase (+1 +/- 8%) and this group was statistically different from both group I and group II. Furthermore, when ischaemia was partially reversible (n = 31), LVEF decreased significantly (-3 +/- 8%), particularly when exercise tests were abnormal (-4 +/- 8%). Group IV was statistically different from groups I and II.

CONCLUSIONS

Good agreement exists between the severity of ischaemic perfusion pattern and LVEF degradation at stress, which is consistent with previously published data using 99Tc(m) gSPECT. Additionally, the use of 201Tl for immediate post-exercise imaging allows the observation of a physiological LVEF increase in normal and infarcted patients.

Hemodynamic and thermal responses to a 30-minute constant-workload aerobic exercise in middle- or old-aged patients with cardiovascular diseases

The aim of the present investigation was to compare the hemodynamic and thermal responses to a 30-min aerobic exercise between middle- or old-aged patients with normal left ventricular function and those with left ventricular dysfunction. Constant-load sitting ergometer exercise of approximately 90% of the subject's oxygen uptake (VO2) at the anaerobic threshold for 30 min was conducted in 21 patients with left ventricular dysfunction (61+/-10 years, left ventricular ejection fraction (LVEF) 35+/-7%) and 24 patients with normal left ventricular function (59+/-9 years, LVEF 71+/-7%). Heart rate (HR), blood pressure, deep temperatures in the forehead and thigh, and forearm skin blood flow (SkBF) were measured every minute, and cardiac output (CO) and stroke volume (SV) were determined every 10 min with the dye-dilution technique during the exercise. Patients of both groups exhibited a progressive elevation in each temperature and an increase in SkBF during the exercise. Although the VO2 and CO remained stable, almost the same magnitude of decrease in SV as increase in HR was seen after the 10th min of exercise in both groups. The magnitude of the decrease in SV was greater in old-aged than middle-aged patients with left ventricular dysfunction. Thus, the downward drift in SV during a 30-min constant-load aerobic exercise might not be influenced by left ventricular function, but intensified by aging in patients with left ventricular dysfunction.

Left ventricular function during interval and steady state exercise

PURPOSE

Interval training (INT) is a commonly used method of exercise training in both athletic and clinical populations. Although we generally understand left ventricular (LV) function during steady state (SS) exercise, there are no data regarding LV function during INT.

METHODS

We studied eight healthy, physically active volunteers during upright cycle ergometry during 15 min of both SS and INT, at the same average power output (90% individual anaerobic threshold), using first pass radionuclide ventriculography. During INT (60s/60s), measures of LV function were made during work (220 W) after 4 and 12 min and during recovery (120 W) after 7 and 15 min. These were compared with the average of four temporally matched measures made during SS (170 W).

RESULTS

During INT, LV ejection fraction increased from rest (67 +/- 6%) to 77 +/- 5, 80 +/- 5, 77 +/- 5 and 79 +/- 4% after 4, 7, 12, and 15 min, respectively. During SS, LV ejection fraction was not significantly different at rest (70 +/- 4%) or during exercise (76 +/- 4, 79 +/- 4, 80 +/- 3, and 81 +/- 3%) after 4, 7, 12, and 15 min, respectively. Other measures of LV function (HR, BP, LV volumes, cardiac output, systemic vascular resistance, peak emptying, and filling rates) were likewise similar during temporally matched measurements during INT and SS.

CONCLUSIONS

Although there were the expected transitions of ejection fraction with work and recovery, the overall hemodynamic picture during INT was very similar to SS. These data suggest that LV function during INT is not substantially different to that during SS.

Comparison of left ventricular function during interval versus steady-state exercise training in patients with chronic congestive heart failure

This study sought to assess the safety of interval exercise training in patients with chronic congestive heart failure (CHF) with respect to left ventricular (LV) function. For effective rehabilitation in CHF, both aerobic capacity and muscle strength need to be improved. We have previously demonstrated in both coronary artery bypass surgery and patients with CHF that interval exercise training (IET) offers advantages over steady-state exercise training (SSET). However, because LV function during IET has not yet been studied, the safety of this method in CHF remains unclear. To assess LV function during IET and SSET, at the same average power output, 11 patients with stable CHF were compared with 9 stable coronary patients with minimal LV dysfunction (control group). Using first-pass radionuclide ventriculography, changes in LV function were assessed during work versus recovery phases, at temporally matched times between the fifth and sixteenth minute of IET and SSET. In CHF during IET, there were no significant variations in the parameters measured during work and/or recovery phases. During the course of both IET and SSET, there was a significant increase in LV ejection fraction (5 vs 4 U; p <0.05 each), accompanied by increased heart rate (6 vs 8 beats/min; p <0.05 each) and cardiac output (2.4 vs 1.8 L/min; p <0.01 and p <0.05). In CHF, the magnitude of change in LV ejection fraction during IET was similar to that seen in controls. Both LV ejection fraction and the clinical status in patients with CHF remained stable during IET. Because IET appears to be as safe as SSET with respect to LV function, IET can be recommended for exercise training in CHF to apply higher peripheral exercise stimuli and with no greater LV stress than during SSET.

The heart rate performance curve and left ventricular function during exercise in patients after myocardial infarction

PURPOSE

The aim of the study was to investigate the heart rate turn point (HRTP) in the time course of the heart rate performance curve (HRPC) in patients after myocardial infarction, and the relationship between the HRTP, the left ventricular function, and the second lactate turn point (LTP2).

METHODS

We studied the degree and the direction of the HRPC and the left ventricular ejection fraction (LVEF) in 49 male patients 57 +/- 8 d after their first posterior wall infarction (MI). An incremental cycle ergometer test was performed and three phases of energy supply were defined (I: aerobic; II: aerobic-anaerobic transition; III: anaerobic) via blood lactate LA concentration. HRTP and LVEF-turn points (LVEFTP) were assessed by linear turn point analysis. The degree and direction of the deflection of HRPC were described as factor k (k > 0.1: downward deflection; -0.1 < k < 0.1: linear time curse; k < -0.1: upward deflection). The LVEF was determined by RNA. The difference between Pmax and LTP2 was calculated for LVEF (delta LVEF).

RESULTS

An HRTP could be found in 44 and a LVEFTP in 47 cases. The HRTP occurred at 85 +/- 17 Watt (W), which correlated (r = 0.95; P < 0.001) with the LTP2 (84 +/- 17 W) and the LVEFTP (84 +/- 17 W, r = 0.93; P < 0.001). From LTP2 to Pmax a significant decrease in LVEF was found. There was a correlation between the percentage of HRmax at the HRTP and k (r = 0.70), as well as delta LVEF (r = 0.56).

CONCLUSIONS

To prevent myocardial overloading, it seems to be useful to determine the HRTP, which indicate the workload where LVEF decreases.

Physiological and pathological aspects of exercise left ventricular function

Measures of left ventricular function during exercise provide information that is more accurate than the exercise ECG in the diagnosis of coronary artery disease, supportive of the data provided by myocardial perfusion studies, and of great prognostic significance. We review basic methods for evaluating left ventricular function during exercise and responses to various types of exercise, including incremental exercise and exercise training conditions. Additionally, we review changes in both incremental exercise test responses and responses to training in various pathological conditions. Case reports are included to illustrate the utility of measuring left ventricular function during exercise.

Highland mountain hiking and coronary artery disease: exercise tolerance and effects on left ventricular function

Physical exercise has become a well-established concept in the secondary prevention of coronary artery disease. We investigated the exercise requirements of extensive highland mountain hiking (8.7 km, 470 m to 1220 m over sea level, average incline 8.5%, mean walking velocity < 3 km x h-1) in 11 regularly exercising male patients with history of MI and stable coronary artery disease (CAD; mean age +/- SD:61.0 +/- 3.9 yr) and 9 age-matched male healthy controls (CO; mean age +/- SD:61.2 +/- 5.0 yr). All subjects underwent continuous ECG monitoring; arterial blood pressure and blood lactate concentrations were measured several times during mountain hiking. Before and after exercise, cardiac dimensions and functions were assessed by two-dimensional echocardiography and Doppler echocardiography. The mean exercise levels for heart rate and blood lactate were compared with the corresponding data of a multistage upright cycle ergometry. Clinical manifestations of coronary insufficiency, left ventricular myocardial dysfunction, or cardiac arrhythmias > Lown IIIb were not observed in any case. No significant differences in left atrial and left ventricular dimensions and no changes in systolic left ventricular function compared with the preexercise values were found after the mountain hike tour. Doppler echocardiography demonstrated significant changes in diastolic left ventricular function in CAD, but not in CO. The peak exercise intensity during mountain hiking was equivalent to a workload of 100-125 W (1.25-1.5 W x kg-1 body weight) in a multistage upright cycle ergometry. Extensive highland mountain hiking may be a low risk alternative within the outpatient rehabilitation program for secondary prevention of CAD for MI patients with a cycle ergometric exercise tolerance > 1.5 W x kg-1 body weight.