Repeatability of treadmill exercise ejection fraction and wall motion using technetium 99m-labeled sestamibi first-pass radionuclide ventriculography

Bacterial antibodies were studied in acute, intermediate and convalescent phase sera (mean duration from first to last sample 36 days) of 121 children hospitalized for acute lower respiratory tract infection. Antibody responses were observed in 45% of all cases and in 29% of the 21 children < 1 year old. A total of 15 responses to Streptococcus pneumoniae (pneumolysin), 20 to Haemophilus influenzae, 9 to Moraxella catarrhalis, 3 to chlamydiae and 8 to Mycoplasma pneumoniae were found. In 79 patients with 4 consecutive samples available, 52% of the 31 responses were measurable within 5 days from admission. Overall the responses were not associated with upper respiratory tract bacterial findings or acute otitis media. Significantly more responses were found in the 121 children with acute lower respiratory tract infection than in healthy controls (P < 0.007). We conclude that bacterial antibody assays provide a useful tool in the study of the etiology of acute lower respiratory tract infection in young children, even if the interval between paired serum samples is short.     

Physiological model of CO2 output during incremental exercise

In this study, a physiological model to explain the pathway of CO2 output during incremental exercise was examined by referring to experimental data. Since CO2 output (VCO2) shows multiple correlations with mixed venous CO2 pressure (PvCO2) and arterial CO2 pressure (PaCO2), the increase in the difference between PvCO2 and PaCO2 was considered to be involved in the increase in VCO2. In order to better understand the influence of CO2 pressure, VCO2 was divided into the expiratory CO2 phase (non-lactic VCO2), which was unrelated to lactic acid increase and the expiratory CO2 phase (excess VCO2), which was related to lactic acid increase. As a result, the non-lactic VCO2 significantly correlated to PvCO2. When non-lactic VCO2 was zero, the value of PvCO2 was 43.7 mmHg. This was higher than the resting PaCO2 value. On the other hand, as PaCO2 showed an almost constant value in the low load phase and showed a low value in the high load phase, it was believed that the low value of PaCO2 was related to the excess VCO2 that appeared in the high load phase. The CO2 excess, which was obtained by adding excess VCO2 in terms of the lapse of exercise time, correlated significantly with an increase in lactate in the blood. Based on the results, a model was constructed to illustrate the pathway of CO2 output. The key points of the model were as follows: (1) the use of the blood CO2 dissociation curve as the vector to transport CO2 from tissue to lungs, (2) the standard value of PaCO2 was established in order to divide non-lactic VCO2 and excess VCO2, (3) the dextroversion of the blood CO2 dissociation curve due to lactic acid was connected to excess VCO2, and (4) a decrease in PaCO2 was related to excess VCO2 derived from tissue.     

Predicting severe ischemic events after uncomplicated myocardial infarction by exercise testing and rest and exercise radionuclide ventriculography

BACKGROUND: In 183 patients with uncomplicated myocardial infarction, exercise-induced angina, ST segment depression, decrease in ejection fraction, or inadequate increase in systolic blood pressure and low exercise tolerance were significantly associated with 4-year incidence of hard ischemic events. METHODS AND RESULTS: Only the onset of both ST segment depression and a decrease in left ventricular ejection fraction with exercise was an independent predictor. ST segment depression and decrease in left ventricular ejection fraction had low sensitivity (61% and 70%) and specificity (56% and 51%) for hard ischemic events, but specificity increased to 78% when both were present. During medical therapy, 22 of 53 patients with both ST segment depression and a decrease in left ventricular ejection fraction with exercise had an ischemic event (i.e., 48.1% 4-year probability on Kaplan-Meier analysis vs 19.2% in the remaining 130 patients [p < 0.0005]). CONCLUSIONS: Even if no single variable, derived from exercise testing, is a highly sensitive and specific predictor, specificity increases to a clinically relevant level by combining ST segment depression and a decrease in left ventricular ejection fraction with exercise, and in this way patients with recent infarction may be selected for coronary arteriography.     

The importance of adequate exercise in the detection of coronary heart disease by radionuclide ventriculography

Rest and exercise radionuclide ventriculograms were obtained on 77 symptomatic patients without prior documented coronary artery disease (CAD). Coronary artery disease was present by angiograms in 48. Radionuclide ventriculography (RNV) was abnormal in 41 patients (overall sensitivity 85%). In 29 patients with normal coronary arteries, RNV was normal in 24 (specificity 83%). To determine if the exercise level affects sensitivity, the studies were graded for adequacy of exercise. It was considered adequate if patients developed (a) chest pain, or (b) ST segment depression of at least 1 mm, or (c) if they achieved a pressure rate produce greater than 250. Among the 48 patients with coronary artery disease, 35 achieved adequate exercise. Thirty-three had an abnormal RNV (sensitivity 94%). In 13 patients who failed to achieve adequate exercise, RNV was abnormal in eight (sensitivity of only 62%). Some patients with coronary artery disease may have a normal ventricular response at inadequate levels of stress.     

Simple method to estimate cardiac output using first-pass data on RI angiography

In order to estimate cardiac output (CO) without using data equilibrium state, a simple index (cardiac output index, COI) was developed from the first-pass data as a ratio of the integrated radioactivity on the right ventricle to the total injected radioactivity. COI was well correlated with CO calculated by the conventional Stewart-Hamilton method (r = 0.894, p < 0.01), and thus, CO could be readily estimated from COI. This index might be useful to estimate CO since it can be obtained even with the agents which distribute to organs.     

Impedance cardiography accurately measures cardiac output during exercise in children with cystic fibrosis

Pro-inflammatory cytokines produced in the central nervous system (CNS) have been suggested to have a role in the anorexia and cachexia of disease. In the present study, the effects of chronic exposure of the CNS to interleukin-1beta (IL-1beta) on several indicators of cachexia were studied. Rats were prepared with an intracerebroventricular (i.c.v.) cannula and an osmotic minipump that delivered vehicle or 1.56 ng/h recombinant murine IL-1beta for 4 days. Food intake and body weight were determined daily during the 4-day infusion period and plasma IL-6 and corticosterone concentrations were determined from plasma collected postinfusion. Chronic i.c.v. infusion of IL-1beta resulted in a chronic reduction in food intake. Rats infused i.c.v. with IL-1beta ate less food each day compared to vehicle controls and, at the end of the 4-day infusion period, consumed an average of 17.2 g less. Intracerebroventricular infusion of IL-1beta also caused an immediate and substantial loss of body weight that was sustained throughout the infusion period. In addition, rats infused with IL-1beta had plasma levels of IL-6 double those of vehicle controls (401 pg/ml vs. 185 pg/ml). Plasma corticosterone concentrations were similar between treatments. These results suggest that chronic exposure of the CNS to cytokines such as IL-1beta may be sufficient to induce anorexia and cachexia.     

First-pass radionuclide angiography during bicycle and treadmill exercise

BACKGROUND: Treadmill testing is usually preferred over cycle ergometry because of the greater sensitivity in diagnosing coronary artery disease. Treadmill testing has only recently been used with radionuclide angiography (RNA) because patient motion makes RNA imaging difficult. In this study we evaluate the comparability of treadmill and cycle exercise RNA with a dual isotope motion correction technique. METHODS AND RESULTS: Volunteer patients (n = 27) performed first-pass RNA during maximal exercise using both cycle ergometer and treadmill. Exercise capacity was greater during treadmill exercise (8.1 +/- 2.4 vs 7.5 +/- 2.2 METs). Twenty-three of 27 treadmill and all cycle ergometer exercise studies were technically adequate. Maximal heart rate was greater during treadmill exercise (150 +/- 24 vs 143 +/- 25 beats * min-l), however, systolic blood pressure was greater during cycle ergometry (174 +/- 23 vs 188 +/- 25 mmHg), resulting in no difference in heart rate times systolic blood pressure (25.7 +/- 7.2 vs 26.9 +/- 6.0). There were no differences between treadmill and cycle ergometer for peak exercise left ventricular ejection fraction (56% +/- 13% vs 57% +/- 14%) (r = 0.89). Calculated left ventricular end-diastolic volume was not different at rest (183 +/- 42 ml vs 176 +/- 44 ml) but differed significantly at peak exercise (282 +/- 75 ml vs 231 +/- 60 ml). The clinical impression, based on wall motion and left ventricular ejection fraction was very similar between treadmill and cycle ergometer. CONCLUSION: Treadmill exercise RNA is feasible, with about 85% of studies likely to be technically adequate. The overall clinical results are very similar to cycle exercise RNA, although the ordinarily expected advantages of treadmill exercise were largely absent.     

Prospective evaluation of viable myocardium by quantitative dipyridamole-thallium-201 scintigraphy and radionuclide ventriculography

Improvement of myocardial function is a major goal of coronary revascularization. Considerable interest remains in the preoperative identification of viable myocardium. We examined 26 consecutive patients with left ventricular dysfunction undergoing coronary artery bypass grafting. Serial dipyridamole-thallium imaging and radionuclide ventriculography was performed preoperatively and postoperatively. The relationship between preoperative and postoperative thallium perfusion and segmental wall motion was analyzed. The mean preoperative ejection fraction was 32 +/- 9 (21 to 51%) and increased to 41 +/- 12 (17 to 67%) postoperatively (p > 0.01). Seventy-seven percent of patients improved their global ejection fraction postoperatively by > 5%. Thallium perfusion improved postoperatively in 84% of reversible defects vs 63% of partially reversible defects and 35% of fixed defects. Segments with either reversible or partially reversible thallium defects showed an improved postoperative wall motion in 71% and 68%, respectively. Postoperative wall motion improved in 43% of fixed defects. Overall, 67% of hypokinetic segments showed improved postoperative wall motion while only 29% of akinetic or dyskinetic segments improved postoperatively. Preoperative thallium redistribution coupled with preserved wall motion was predictive of improvement in wall motion was predictive of improvement in wall motion postoperatively and indirectly indicates myocardial viability. However, 43% of fixed defects also showed improved postoperative wall motion. A significant improvement in global ejection fraction was found and could be predicted by a linear regression analysis utilizing clinical and thallium parameters.     

The differing prognostic utility of exercise radionuclide ventriculography in coronary artery disease patients with and without prior myocardial infarction

Previous studies have documented the prognostic utility of left ventricular ejection fraction response to exercise primarily in populations without prior myocardial infarction. We undertook a study to assess the prognostic utility of exercise left ventricular ejection fraction and segmental wall motion response during exercise radionuclide ventriculography in coronary artery disease patients with and without prior myocardial infarction. METHODS: We examined the comparative prognostic utility of left ventricular ejection fraction and segmental wall motion response during upright bicycle exercise radionuclide ventriculography in 419 coronary artery disease patients with (n = 217) and without (n = 202) prior myocardial infarction using univariate and multivariate hierarchical regression analyses. RESULTS: During an average followup period of 61 months, 96 patients (23%) suffered cardiac events, including 55/217 (25%) of the patients with prior myocardial infarction and 41/200 (21%) of the patients without prior myocardial infarction (p = ns). Both cumulative Kaplan-Meier survival analyses and stepwise hierarchical Cox survival analyses demonstrated that peak left ventricular ejection fraction < 55% was a significant predictor of cardiac events in patients without prior myocardial infarction (p = 0.04), whereas an exercise wall motion worsening score > or = 2 was a significant predictor in patients with a prior myocardial infarction (p = 0.0001). CONCLUSIONS: The prognostic utility of exercise radionuclide ventriculography variables differ according to the presence or absence of prior myocardial infarction. Global function, assessed by peak left ventricular ejection fraction, adds the greatest prognostic information in patients without prior myocardial infarction, whereas regional function, assessed by exercise wall motion worsening, is the best predictor among patients with prior myocardial infarction.     

Blood lactate concentrations during incremental exercise in subjects with sickle cell trait

The need for lateral release or "venting" of the A2 and A4 pulleys either to facilitate repair of the flexor tendon(s) or to allow free gliding of the repair(s) was examined in 126 consecutive zone 2 flexor tendon injuries within the tendon sheath and distal to the distal edge of the A2 pulley (zones 2A and 2B of Tang's classification) in which at least one flexor tendon had been completely divided. This study showed that 81 (64%) of these repairs required venting of one or the other pulley. It was necessary to vent the A4 pulley between 10 and 100% of its length in 71 (56%) of the fingers and to vent the distal edge of the A2 pulley by 4 to 10 mm in 10 (8%) of the fingers.     

Muscle oxygenation during incremental arm and leg exercise in men and women

The purpose of this study was to compare the rates of muscle deoxygenation in the exercising muscles during incremental arm cranking and leg cycling exercise in healthy men and women. Fifteen men and 10 women completed arm cranking and leg cycling tests to exhaustion in separate sessions in a counterbalanced order. Cardiorespiratory measurements were monitored using an automated metabolic cart interfaced with an electrocardiogram. Tissue absorbency was recorded continuously at 760 nm and 850 nm during incremental exercise and 6 min of recovery, with a near infrared spectrometer interfaced with a computer. Muscle oxygenation was calculated from the tissue absorbency measurements at 30%, 45%, 60%, 75% and 90% of peak oxygen uptake (VO2) during each exercise mode and is expressed as a percentage of the maximal range observed during exercise and recovery (%Mox). Exponential regression analysis indicated significant inverse relationships (P < 0.01) between %Mox and absolute VO2 during arm cranking and leg cycling in men (multiple R = -0.96 and -0.99, respectively) and women (R = -0.94 and -0.99, respectively). No significant interaction was observed for the %Mox between the two exercise modes and between the two genders. The rate of muscle deoxygenation per litre of VO2 was 31.1% and 26.4% during arm cranking and leg cycling, respectively, in men, and 26.3% and 37.4% respectively, in women. It was concluded that the rate of decline in %Mox for a given increase in VO2 between 30% and 90% of the peak VO2 was independent of exercise mode and gender.     

Physiological effects of variations in spontaneously chosen crank rate during incremental upper-body exercise

The aims of the present study were: first, to assess the interindividual variations of a spontaneously chosen crank rate (SCCR) in relation to the power developed during an incremental upper body exercise on an arm ergometer set at a constant power regime, and second, to compare heart rate (HR) responses, expired minute ventilation (V[E]) and oxygen consumption (VO2) when the pedal rates were chosen spontaneously (T[SCCR]) or set at +/- 10% of the freely chosen rates (T[+10%] and T[-10%], respectively). The mean pedal rate values were linearly related (P < 0.01) with the power developed during arm cranking (r = 0.96), although large variations of pedalling rate strategies were observed between subjects. Maximal power (MP) and time to exhaustion values were significantly higher (P < 0.05) during T(SCCR) than during T(+10%) and T(-10%). Peak VO2 values were significantly higher (P < 0.05) in T(+10%) than in T(SCCR) and T(-10%). The increase in HR, V(E), and VO2 mean values, in relation to the increase in the power developed, was significantly higher (P < 0.05) when the pedal rate was set at plus 10% of the SCCR (T[+/-10%]) than in the two other conditions. The findings of the present study suggest that the use of an electromagnetically braked ergometer, which automatically adjusts the resistance component to maintain a constant work rate, should be used in order to achieve the highest MP values during an incremental upper body exercise. A 10% increase of the SCCR should be used in order to provide the highest peak VO2 value.     

Evaluation of right ventricular systolic pressure during incremental exercise by Doppler echocardiography in adults with atrial septal defect

STUDY OBJECTIVES: Pulmonary hypertension is the most important complication in patients with atrial septal defect (ASD), but its role in limiting exercise has not been examined. This study sought to evaluate exercise performance in adults with ASD and determine the contribution of elevated pulmonary artery pressure in limiting exercise capacity. DESIGN: We used Doppler echocardiography during exercise in 10 adults (aged 34 to 70 years) with isolated ASD (New York Heart Association class I, II) and an equal number of matched control subjects. Incremental exercise was performed on an electrically braked upright cycle ergometer. Expired gases and VE were measured breath-by-breath. Two-dimensional and Doppler echocardiographic images were obtained at rest prior to exercise to determine ASD size, stroke volume (SV), shunt ratio (Qp:Qs), right ventricular outflow tract (RVOT) size, and right ventricular systolic pressure at rest (RVSPr). Doppler echocardiography was repeated at peak exercise to measure right ventricular systolic pressure during exercise (RVSPex). RESULTS: Resting echocardiography revealed that RVOT was larger (21+/-4 vs 35+/-8 mm, mean+/-SD; p=0.0009) and RVSPr tended to be higher (17+/-8 vs 31+/-8 mm Hg; p=0.08) in ASD; however, left ventricular SV was not different (64+/-23 vs 58+/-23 mL; p>0.05), compared with control subjects. Despite normal resting left ventricular function, ASD patients had a significant reduction in maximum oxygen uptake (VO2max) (22.9+/-5.4 vs 17.3+/-4.2 mL/kg/min; p=0.005). RVSPex was higher (19+/-8 vs 51+/-10 mm Hg; p=0.001) and the mean RVSP-VO2 slope (1+/-2 vs 18+/-3 mm Hg/L/min; p=0.003) and intercept (17+/-4 vs 27+/-4 mm Hg; p=0.05) were higher in the ASD group. VO2max correlated inversely with both RVSPr (r=-0.69; p=0.007) and RVSPex (r=-0.67; p=0.01). CONCLUSION: These findings suggest that adults with ASD have reduced exercise performance, which may be associated with an abnormal increase in pulmonary artery pressure during exercise.     

Effect of step duration during incremental exercise on breathing pattern and mouth occlusion pressure

We compared the effects of two step durations on breathing pattern, mouth occlusion pressure and "effective" impedance of the respiratory system during incremental exercise. Nine normal subjects (mean age: 27.8+/-1.21 years) performed two incremental exercise tests in randomized order: one test with step increments every 1 min 30s and the other, every 4 min. After a warm-up at 25 W for the 1 min 30 s test, the power was increased by 50 W from 50 W to exhaustion. During the last minute at each power, we measured ventilation (VE), tidal volume (VT), breathing frequency (fR), inspiratory and expiratory time (TI and TE), total time of the respiratory cycle (TTOT), TI/TTOT, mean inspiratory flow (VT/TI), mouth occlusion pressure (P0.1), "effective" impedance of the respiratory system (P0.1/(VT/ TI)) and venous blood lactate concentration ([La]). Our result showed that at maximal exercise the power was significantly higher (p < 0.01) and [La] lower (p < 0.01) in the 1 min 30 s test. At 100, 150 and 200 W, the 4 min test showed significantly higher oxygen uptake (VO2), carbon dioxide output (VCO2), VE, P0.1, fR, VT/TI and HR (p <0.001) and significantly lower TI, TE and TTOT (p<0.01). [La] was significantly higher at 150 W (p<0.05) and 200 W (p<0.001). At the same VCO2, P0.1 was not significantly different between the two tests, whereas VE showed a tendency to be higher (p = 0.08) and P0.1/(VT/TI) was significantly lower during the 4 min test. In conclusion, this study allowed us to quantify the difference in inspiratory neuromuscular output and ventilatory response between 1 min 30s and 4 min tests and showed that different step durations alter the relationship between inspiratory neuromuscular output and mean inspiratory flow.     

Blood-gas measurements adjusted for temperature at three sites during incremental exercise in the horse

Rectal temperature (Tre) is often used to adjust measurements of blood gases, but these adjusted measurements may not approximate temperatures during intense exercise at main sites of gas exchange: muscle and lung. To evaluate differences in blood gases between sites, temperatures (T) were measured with thermocouples in the rectum (re), in mixed venous blood (v), in gluteal muscle (mu), and on the skin (sk) in seven Arabian horses as they underwent an incremental exercise test on a treadmill. Blood samples were drawn from the carotid artery and pulmonary artery (mixed venous) 30 s before each increase in speed and during recovery. Blood gases and pH were measured at 37 degreesC, and all variables were adjusted to Tre, Tv, and Tmu. Adjusted variables during exercise and recovery were significantly different from each other at the three sites. Linear and polynomial equations described the time course of venous temperature and from Tre and Tsk during exercise and from Tsk during recovery. Interpretation of changes in muscle metabolism and gas exchanges based on blood-gas measurements is improved if they are adjusted appropriately to Tmu or Tv, which may be predicted from Tsk in addition to Tre during strenuous exercise and from Tsk during recovery.     

Comparison of impedance cardiography with indirect Fick (CO2) method of measuring cardiac output in healthy children during exercise

Shortened hospital stays have decreased women's access to postpartum nursing care. Providers and payers together must address clinical and cost issues to develop a model of maternity care that covers the postpartum period. A short-stay maternity program was developed in 1989 by Professional Nurse Associates, Inc., in conjunction with Kaiser Permanente. The program includes prenatal preparation of families, a brief hospital stay, postpartum home visits, and postvisit case management. Readmission rates or mothers and newborns in the program have been less than 1%. The program has saved about $1 million a year since 1991, and consumer satisfaction has been measured at 99%.     

Effect of exercise on cardiac output and distribution of uterine blood flow in pregnant ewes

This study was designed to determine what effect physical training has on heart rate and stroke volume responses to exercise stress and to determine if exercise altered the distribution of uterine blood flow. Measurements were made in ten pregnant ewes at rest and immediately following exercise on a treadmill. Five ewes underwent physical training for 3 wk prior to measurement. An increase in heart rate with no change in stroke volume was observed following exercise in both trained and untrained ewes. Total uterine blood flow was not changed following exercise, but distribution was altered in favor of the placenta. Blood flow was evenly distributed within the placenta before and after exercise. The redistribution of flow to the placenta that occurs after exercise. tphe redistribution of flow to the placenta that occurs after exercise might represent a compensatory mechanism for the fetus.     

Errors in the measurement of cardiac output by thermodilution

Cardiac output (CO) determination by thermodilution, which was introduced by Fegler in 1954, has gained wide acceptance in clinical medicine and animal experiments because it has several advantages over other methods with respect to simplicity, accuracy, reproducibility, repeated measurements at short intervals, and because there is no need for blood withdrawal. However, errors in determination of CO by thermodilution may be introduced by technical factors and the patients' pathological conditions. The current review summarizes these issues and provides our recommendations, based on the medical literature published between 1954-1992. To obtain more reproducible and accurate CO values by thermodilution, one should make several determinations (1) by using 10 ml injectate at room temperature for adults and 0.15 ml.kg-1 injectate for infants and children; (2) at evenly spaced intervals of the ventilation cycle; (3) when rapid intravenous fluid administration is discontinued; (4) by observing thermodilution curves so that baseline pulmonary artery temperature drift or the existence of intra- and extracardiac shunts are noticed. Finally, CO determination by thermodilution may be unreliable or impossible in patients with low CO states and tricuspid or pulmonary regurgitation. Since non-invasive CO monitoring has not replaced CO determination by thermodilution, intimate knowledge of this method is crucial for anaesthetists to prevent errors in the management of patients.