Cardiopulmonary exercise testing for evaluation of a randomized exercise training intervention following aortic valve replacement

Aortic valve surgery is the definitive treatment for aortic stenosis (AS). No specific recommendation is available on how exercise training should be conducted and evaluated after aortic valve replacement (AVR). This study aimed to examine the effect of aerobic exercise training on exercise capacity following AVR. In addition to our primary outcome variable, peak oxygen uptake (peakVO₂), the effect on submaximal cardiopulmonary variables including oxygen uptake kinetics (tau), oxygen uptake efficiency slope (OUES) and ventilatory efficiency (VE/VCO₂ slope) was evaluated. Following AVR due to AS, 12 patients were randomized to either a group receiving 12 weeks of supervised aerobic exercise training (EX) or a control group (CON). Exercise capacity was assessed by a maximal cardiopulmonary exercise test (CPET). There was a significant increase in peak load (+28%, P = 0·031) and in peakVO₂ (+23%, P = 0·031) in EX, corresponding to an increase in achieved percentage of predicted peakVO₂ from 88 to 104% (P = 0·031). For submaximal variables, there were only non‐statistically significant trends in improvement between CPETs in EX. In CON, there were no significant differences in any maximal or submaximal variable between CPETs. We conclude that 12 weeks of supervised aerobic exercise training induces significant adaptations in cardiopulmonary function following AVR, especially in regard to maximal variables including peakVO₂. In addition, we provide novel data on the effect on several submaximal variables following exercise training in this group of patients.     

Measurement of physical work capacity in patients with chronic aortic regurgitation: a potential improvement in patient management

Background: Timing of surgery in aortic regurgitation (AR) is important. Exercise testing is recommended upon uncertainty about functional limitations but reports on cardiopulmonary exercise testing (CPET) in populations with pure chronic AR are scarce. Method: Twenty‐eight patients referred for surgery because of chronic AR (13 in NYHA I, 10 in NYHA II and five in NYHA III) were tested by CPET pre‐ and 6 months postoperatively. Echocardiography, with measurement of left ventricular ejection fraction (LVEF), diameters (LVED, LVES) and volumes (LVEDV, LVESV) was also performed. Results: The patients had normal LVEF pre‐ and postoperatively. LV diameters and volumes diminished significantly postoperatively (LVED from 67 to 57, LVES from 49 to 41 mm; P < 0·001). The majority of the patients had a ‘low’ physical work capacity, none of them performed better than ‘average’ according to Åstrand’s classification preoperatively and there was no significant postoperative improvement. The mean peak oxygen uptake () was 25 ml kg^?1 min^?1 both pre‐ and postoperatively, and six of the 28 patients had a of less than 20 ml kg^?1 min^?1. was not significantly related to NYHA class. Conclusion: LVEF, diameters and volumes at rest did not fulfil the criteria for surgery in most of our AR patients, of whom 46% were asymptomatic. However, many had a remarkably low work capacity, which was neither improved 6 months postoperatively nor correlated to echocardiographic LV dimensions. CPET predicted the postoperative work capacity and may, therefore, be a useful complement for timing of surgery in patients with chronic AR.     

Day‐to‐day variation in oxygen consumption at submaximal loads during ergometer cycling by adolescents

The day‐to‐day variation in oxygen consumption (V˙O₂) during ergometer cycling by 20 healthy adolescents, 10 females and 10 males, was measured using indirect calorimetry. The two sets of measurements were performed on two consecutive days. Great care was taken to minimize possible disturbing factors. Cycling started at 50 and 100 W for female and male adolescents, respectively. The load was increased at a rate of 5 W 30 s^?1. In order to reach steady state, the load was kept constant for 3·5 min twice during the cycling session, at 100 and 130 W for the females and at 130 and 160 W for the males. Cycling continued until exhaustion. The maximal loads were 196 W (mean) and 271 W (mean) for females and males, respectively. At the maximal loads the day‐to‐day variation (±2 SD) in oxygen consumption (V˙O₂) was ±330 ml min^?1 for females and 390 ml min^?1 for males. At the submaximal loads the day‐to‐day variation in heart rate (HR) was 9·3 beats min^?1 (±2 SD) (coefficient of variation, CV=3·4% at 130 W) for both sexes. The day‐to‐day variation in oxygen consumption (V˙O₂) was ±199 ml min^?1 (±2 SD) at the different submaximal loads and did not differ between female and male adolescents (CV=5·7% at 130 W). This natural day‐to‐day variation must be taken into consideration when using a submaximal ergometer cycling test for the evaluation of physical capacity in the two sexes.     

Simultaneous quantification of myocardial perfusion,oxidative metabolism,cardiac efficiency and pump function at rest and during supine bicycle exercise using 1‐11C‐acetate PET – a pilot study

Background: PET using 1‐¹¹C‐acetate (ACE‐PET) applied at rest is used for measuring absolute myocardial blood flow (MBF) and oxidative metabolic rate (k_mono). We evaluated the feasibility of quantitative ACE‐PET during exercise. Methods: Five endurance athletes underwent dynamic PET scanning at rest and during supine bicycle stress. Exercise was maintained at a workload of 120 Watt for 17 min. The rate‐pressure product (RPP) was recorded repeatedly. MBF, k_mono in left (LV) and right (RV) ventricular wall, cardiac output (CO), cardiac efficiency and a lung uptake value reflecting left heart diastolic pressures were calculated from the PET data using previously validated models. Results: MBF increased from 0·71 ± 0·17 to 2·48 ± 0·25 ml min^?1 per ml, LV‐k_mono from 0·050 ± 0·005 to 0·146 ± 0·021 min^?1, RV‐k_mono from 0·023 + 0·006 to 0·087 + 0·014 min^‐1, RPP from 4·7 ± 0·8 to 13·2 ± 1·4 mmHg × min^?1 × 10³ and Cardiac Output from 5·2 ± 1·1 to 12·3 ± 1·2 l min ^?1 (all P < 0·001). Cardiac efficiency was unchanged (P = 0·99). Lung uptake decreased from 1·1 ± 0·2 to 0·6 ± 0·1 ml g^?1 (P < 0·001). Discussion: A number of important parameters related to cardiac function can be quantified non‐invasively and simultaneously with a short scanning protocol during steady state supine bicycling. This might open up new opportunities for studies of the integrated cardiac physiology in health and early asymptomatic disease.     

Intensity of Nordic Walking in young females with different peak O2 consumption

The purpose of this cross‐sectional study was to determine the physiological reaction to the different intensity Nordic Walking exercise in young females with different aerobic capacity values. Twenty‐eight 19–24‐year‐old female university students participated in the study. Their peak O₂ consumption (VO₂ peak kg^?1) and individual ventilatory threshold (IVT) were measured using a continuous incremental protocol until volitional exhaustion on treadmill. The subjects were analysed as a whole group (n = 28) and were also divided into three groups based on the measured VO₂ peak kg^?1 (Difference between groups is 1 SD) as follows: 1. >46 ml min^?1 kg^?1 (n = 8), 2. 41–46 ml min^?1 kg^?1 (n = 12) and 3. <41 ml min^?1 kg^?1 (n = 8). The second test consisted of four times 1 km Nordic Walking with increasing speed on the 200 m indoor track, performed as a continuous study (Step 1 – slow walking, Step 2 – usual speed walking, Step 3 – faster speed walking and Step 4 – maximal speed walking). During the walking test expired gas was sampled breath‐by‐breath and heart rate (HR) was recorded continuously. Ratings of perceived exertion (RPE) were asked using the Borg RPE scale separately for every 1 km of the walking test. No significant differences emerged between groups in HR of IVT (172·4 ± 10·3–176·4 ± 4·9 beats min^?1) or maximal HR (190·1 ± 7·3–191·6 ± 7·8 beats min^?1) during the treadmill test. During maximal speed walking the speed (7·4 ± 0·4–7·5 ± 0·6 km h^?1) and O₂ consumption (30·4 ± 3·9–34·0 ± 4·5 ml min^?1 kg^?1) were relatively similar between groups (P > 0·05). However, during maximal speed walking, the O₂ consumption in the second and third groups was similar with the IVT (94·9 ± 17·5% and 99·4 ± 15·5%, respectively) but in the first group it was only 75·5 ± 8·0% from IVT. Mean HR during the maximal speed walking was in the first group 151·6 ± 12·5 beats min^?1, in the second (169·7 ± 10·3 beats min^?1) and the third (173·1 ± 15·8 beats min^?1) groups it was comparable with the calculated IVT level. The Borg RPE was very low in every group (11·9 ± 2·0–14·4 ± 2·3) and the relationship with VO₂and HR was not significant during maximal speed Nordic Walking. In summary, the present study indicated that walking is an acceptable exercise for young females independent of their initial VO₂ peak level. However, females with low initial VO₂ peak can be recommended to exercise with the subjective ‘faster speed walking’. In contrast, females with high initial VO₂ peak should exercise with maximal speed.     

Measurement of cardiac output with non-invasive Aesculon impedance versus thermodilution

Background: This study compared the non‐invasive thoracic electrical bioimpedance Aesculon^® technique (TEB_Aesculon) with thermodilution (TD) to evaluate whether TEB_Aesculon may offer a reliable means for estimating cardiac output (CO) in humans. Material and method: Cardiac output was measured with TD and TEB_Aesculon in 33 patients, with a mean age ± SEM of 59 ± 2·7 years, that underwent right heart catheterization for clinical investigation of pulmonary hypertension or severe heart failure. Four to five CO measurements were performed with each technique simultaneously in 33 patients at rest, 11 during exercise and seven during NO inhalation. Result: Cardiac output correlated poorly between TEB_Aesculon and TD at rest (r = 0·46, P<0·001), during exercise (r = 0·35, P<0·013) and NO inhalation (r = 0·41, P<0·017). CO was higher for TEB_Aesculon than TD with 0·86 ± 0·14 l min^?1 at rest (P<0·001) and 2·95 ± 0·69 l min^?1 during exercise (P<0·003), but similar during NO inhalation, with a tendency (P<0·079) to be 0·44 ± 0·19 l min^?1 higher for TEB_Aesculon than TD. CO increased from rest to exercise for TEB_Aesculon and TD with 6·11 ± 0·6 l min^?1 (P<0·001) and 3·91 ± 0·36 l min^?1 (P<0·001), respectively; an increase that was higher (P<0·002) for TEB_Aesculon than TD. During NO inhalation, compared to rest, CO decreased for TEB_Aesculon with 0·62 ± 0·11 l min^?1 (P<0·002), but not significantly for TD with 0·21 ± 0·12 l min^?1 (P<0·11). Bland–Altman analysis showed a poor agreement between TEB_Aesculon and TD. Conclusion: TEB_Aesculon overestimated CO compared to TD with ～17% at rest and ～34% during exercise, but the techniques showed similar results during NO inhalation. CO, furthermore, correlated poorly between TEB_Aesculon and TD. TEB_Aesculon may at present not replace TD for reliable CO measurements in humans.     

The effect of different exercise‐testing protocols on atrial natriuretic peptide

The aim of this study was to examine and to compare alterations in the secretion of atrial natriuretic peptide (ANP) during different exercise‐testing protocols in moderately trained men. Fifteen healthy male physical education students were studied (mean age 22·3 ± 2·5 years, training experience 12·3 ± 2·5 years, height 1·80 ± 0·06 m, weight 77·4 ± 8·2 kg). Participants performed an initial graded maximal exercise testing on a treadmill for the determination of VO_2max (duration 7·45–9·3 min and VO_2max 55·05 ± 3·13 ml kg^?1 min^?1) and were examined with active recovery (AR), passive recovery (PR) and continuous running (CR) in random order. Blood samples for plasma ANP concentration were taken at rest (baseline measurement), immediately after the end of exercise as well as after 30 min in passive recovery time (PRT). The plasma ANP concentration was determined by radioimmunoassay (RIA). The results showed that ANP plasma values increased significantly from the rest period to maximal values. In the short‐term graded maximal exercise testing the ANP plasma values increased by 56·2% (44·8 ± 10·4 pg ml^?1 versus 102·3 ± 31·3 pg ml^?1, P<0.001) and in the CR testing the ANP levels increased by 29·2% (44·8 ± 10·4 pg ml^?1 versus 63·3 ± 19·8 pg ml^?1, P<0.001) compared to the baseline measurement. Moreover, the values of ANP decreased significantly (range 46·4–51·2%, P<0.001) in PRT after the end of the four different exercise modes. However, no significant difference was evident when ANP values at rest and after AR and PR were compared. It is concluded that the exercise testing protocol may affect the plasma ANP concentrations. Particularly, short‐term maximal exercise significantly increases ANP values, while the intermittent exercise form of active and passive recovery decreases ANP concentrations.     

Calculation algorithms alter the breath‐by‐breath gas exchange values when abrupt changes in ventilation occur

The automatic metabolic units calculate breath‐by‐breath gas exchange from the expiratory data only, applying an algorithm (‘expiration‐only’ algorithm) that neglects the changes in the lung gas stores. These last are theoretically taken into account by a recently proposed algorithm, based on an alternative view of the respiratory cycle (‘alternative respiratory cycle’ algorithm). The performance of the two algorithms was investigated where changes in the lung gas stores were induced by abrupt increases in ventilation above the physiological demand. Oxygen, carbon dioxide fractions and ventilatory flow were recorded at the mouth in 15 healthy subjects during quiet breathing and during 20‐s hyperventilation manoeuvres performed at 5‐min intervals in resting conditions. Oxygen uptakes and carbon dioxide exhalations were calculated throughout the acquisition periods by the two algorithms. Average ventilation amounted to 6·1 ± 1·4 l min^?1 during quiet breathing and increased to 41·8 ± 27·2 l min^?1 during the manoeuvres (P<0·01). During quiet breathing, the two algorithms provided overlapping gas exchange data and noise. Conversely, during hyperventilation, the ‘alternative respiratory cycle’ algorithm provided significantly lower gas exchange data as compared to the values yielded by the ‘expiration‐only’ algorithm. For the first breath of hyperventilation, the average values provided by the two algorithms amounted to 0·37 ± 0·34 l min^?1 versus 0·96 ± 0·73 l min^?1 for O₂ uptake and 0·45 ± 0·36 l min^?1 versus 0·80 ± 0·58 l min^?1 for exhaled CO₂ (P<0·001 for both). When abrupt increases in ventilation occurred, such as those arising from a deep breath, the ‘alternative respiratory cycle’ algorithm was able to halve the artefactual gas exchange values as compared to the ‘expiration‐only’ approach.     

Autonomic nervous function at rest in aerobically trained and untrained oldermen

Therelationship between aerobictraining, vagal influence on the heart and ageing was examined by assessing aerobic fitness andresting heart rate variability in trained and untrained older men. Subjects were 11 trained cyclistsand runners (mean age=6±61·6 years) and 11 untrained, age-matchedmen (mean age=66±1·2 years). Heart rate variability testing involvedsubjects lying supine for 25 min during which subjects’ breathing was paced andmonitored (7·5 breaths min^?1). Heart rate variability was assessedthrough time series analysis (HRV_ts) of the interbeat interval. Results indicated thattrained older men (3·55±0·21 l min^?1) hadsignificantly (P<0·05) greater VO _2maxthan that of control subjects (2·35±0·15 l min^?1).Also, trained older men (52±1·8 beats min^?1) hadsignificantly (P<0·05) lower supine resting heart rate than that of controlsubjects (65±4·2 beats min^?1). HRV_ts at highfrequencies was greater for trained men (5·98±0·22) than for untrainedmen (5·23±0·32). These data suggest that regular aerobic exercise inolder men is associated with greater levels of HRV_ts at rest.     

Inert gas rebreathing: the effect of haemoglobin based pulmonary shunt flow correction on the accuracy of cardiac output measurements in clinical practice

Background: Cardiac output (CO) is an important cardiac parameter, however its determination is difficult in clinical routine. Non‐invasive inert gas rebreathing (IGR) measurements yielded promising results in recent studies. It directly measures pulmonary blood flow (PBF) which equals CO in absence of significant pulmonary shunt flow (Q_S). A reliable shunt correction requiring the haemoglobin concentration (c_Hb) as only value to be entered manually has been implemented. Therefore, the aim of the study was to evaluate the effect of various approaches to Q_S correction on the accuracy of IGR. Methods: Cardiac output determined by cardiac magnetic resonance imaging (CMR) served as reference values. The data was analysed in four groups: PBF without correcting for Q_S (group A), shunt correction using the patients’ individual c_Hb values (group B), a fixed standard c_Hb of 14·0 g dl^?1 (group C) and a gender‐adapted standard c_Hb for male (15·0 g dl^?1) and female (13·5 g dl^?1) probands each (group D). Results: 147 patients were analysed. Mean CO_CMR was 5·2 ± 1·4 l min^?1, mean CO_IGR was 4·8 ± 1·3 l min^?1 in group A, 5·1 ± 1·3 in group B, 5·1 ± 1·3 l min^?1 in group C and 5·1 ± 1·4 l min^?1 in group D. The accuracy in group A (mean bias 0·5 ± 1·1 l min^?1) was significantly lower as compared to groups B, C and D (0·1 ± 1·1 l min^?1; P<0·01). Conclusion: IGR allows a reliable non‐invasive determination of CO. Since PBF significantly increased the measurement bias, shunt correction should always be applied. A fixed c_Hb of 14·0 g dl^?1 can be used for both genders if the exact c_Hb value is not known. Nevertheless, the individual value should be used if any possible.     

Assessment of left ventricular systolic function using tissue Doppler imaging in children after successful repair of aortic coarctation

Aim: Assessment of left ventricular systolic function in children after the successful repair of aortic coarctation using tissue Doppler imaging (TDI). Methods: The study group consisted of 32 patients (mean age 12·0 ± 4·2 years) after the aortic coarctation repair. The TDI parameters and the conventional echocardiographic endocardial and midwall indices of the left ventricular systolic function were analysed and compared with the results obtained from 34 healthy children. Results: The systolic mitral annulus motion velocity, systolic myocardial velocity of the medial segment of the left ventricular septal wall, left ventricular strain and Strain Rate (SR) in the study group were significantly higher than in the control group, respectively: 6·92 ± 0·75 cm s^?1 versus 6·45 ± 0·83 cm s^?1; 5·82 ± 1·03 cm s^?1 versus 5·08 ± 1·11 cm s^?1; ?28·67 ± 6·04% versus ?22·53 ± 6·44% and ?3·20 ± 0·76 s^?1 versus ?2·39 ± 0·49 s^?1. Except midwall shortening fraction the conventional endocardial and midwall echocardiographic indices in the study group were significantly higher in comparison to the healthy controls. The left ventricular systolic meridional fibre stress and end‐systolic circumferential wall stress did not differ between the examined groups. There were no differences of the TDI or conventional parameters between hypertensive and normotensive patients. Conclusions: Left ventricular systolic performance in children after the surgical repair of aortic coarctation reveals tendency to rise in late follow‐up despite a satisfactory result after surgery. Higher systolic strain and SR in children treated due to coarctation of the aorta may suggest the increased preserved left ventricular performance despite normalization of afterload.     

Commonly used reference values underestimate oxygen uptake in healthy, 50‐year‐old Swedish women

Cardiopulmonary exercise testing (CPET) is the gold standard among clinical exercise tests. It combines a conventional stress test with measurement of oxygen uptake (V_O2) and CO₂ production. No validated Swedish reference values exist, and reference values in women are generally understudied. Moreover, the importance of achieved respiratory exchange ratio (RER) and the significance of breathing reserve (BR) at peak exercise in healthy individuals are poorly understood. We compared V_O2 at maximal load (peakV_O2) and anaerobic threshold (V_O2@AT) in healthy Swedish individuals with commonly used reference values, taking gender into account. Further, we analysed maximal workload and peakV_O2 with regard to peak RER and BR. In all, 181 healthy, 50‐year‐old individuals (91 women) performed CPET. PeakV_O2 was best predicted using Jones et al. (100·5%). Furthermore, underestimation of peakV_O2 in women was found for all studied reference values (P<0·001) and was largest for Hansen‐Wasserman: women had 115% of predicted peakV_O2, while men had 103%. PeakV_O2 was similar in subjects with peak RER of 1–1·1 and RER > 1·1 (2 328·7 versus 2 176·7 ml min^?1, P = 0·11). Lower BR (≤30%) related to significantly higher peakV_O2 (P<0·001). In conclusion, peakV_O2 was best predicted by Jones. All studied reference values underestimated oxygen uptake in women. No evidence for demanding RER > 1·1 in healthy individuals was found. A lowered BR is probably a normal response to higher workloads in healthy individuals.     

Perfusion heterogeneity does not explain excess muscle oxygen uptake during variable intensity exercise

The association between muscle oxygen uptake (VO₂) and perfusion or perfusion heterogeneity (relative dispersion, RD) was studied in eight healthy male subjects during intermittent isometric (1 s on, 2 s off) one‐legged knee‐extension exercise at variable intensities using positron emission tomography and a‐v blood sampling. Resistance during the first 6 min of exercise was 50% of maximal isometric voluntary contraction force (MVC) (HI‐1), followed by 6 min at 10% MVC (LOW) and finishing with 6 min at 50% MVC (HI‐2). Muscle perfusion and O₂ delivery during HI‐1 (26 ± 5 and 5·4 ± 1·0 ml 100 g^?1 min^?1) and HI‐2 (28 ± 4 and 5·8 ± 0·7 ml 100 g^?1 min^?1) were similar, but both were higher (P<0·01) than during LOW (15 ± 3 and 3·0 ± 0·6 ml 100 g^?1 min^?1). Muscle VO₂ was also higher during both HI workloads (HI‐1 3·3 ± 0·4 and HI‐2 4·1 ± 0·6 ml 100 g^?1 min^?1) than LOW (1·4 ± 0·4 ml 100 g^?1 min^?1; P<0·01) and 25% higher during HI‐2 than HI‐1 (P<0·05). O₂ extraction was higher during HI workloads (HI‐1 62 ± 7 and HI‐2 70 ± 7%) than LOW (45 ± 8%; P<0·01). O₂ extraction tended to be higher (P = 0·08) during HI‐2 when compared to HI‐1. Perfusion was less heterogeneous (P<0·05) during HI workloads when compared to LOW with no difference between HI workloads. Thus, during one‐legged knee‐extension exercise at variable intensities, skeletal muscle perfusion and O₂ delivery are unchanged between high‐intensity workloads, whereas muscle VO₂ is increased during the second high‐intensity workload. Perfusion heterogeneity cannot explain this discrepancy between O₂ delivery and uptake. We propose that the excess muscle VO₂ during the second high‐intensity workload is derived from working muscle cells.     

Less pronounced reverse left ventricular remodeling in patients with bicuspid aortic stenosis treated with transcatheter aortic valve replacement compared to tricuspid aortic stenosis

To compare reverse left ventricular (LV) remodeling after transcatheter aortic valve replacement (TAVR) between patients with bicuspid aortic valve (BAV) and tricuspid aortic valve (TAV). We retrospectively reviewed data of patients with at least two serial echocardiographic follow-ups (1, 3, 6 months and 1 year) post-TAVR. A total of 116 patients were identified. BAV morphology was documented in 67 patients. LV mass index (LVMi) at baseline was not significantly different between the TAV and BAV group (178.0?±?6.9 vs. 166.3?±?6.4 g/m², P?=?0.14). Reverse LV remodeling was observed in both BAV and TAV patients, but the reduction of LVMi from baseline was significantly more pronounced in TAV patients compared with BAV patients from 6 months post-TAVR (??56.3?±?8.1 vs. ??30.0?±?4.7 g/m², P?<?0.01 at 6-month follow-up; ??60.6?±?7.6 vs. ??37.9?±?6.2 g/m², P?=?0.02 at 1-year follow-up). EDV value changes during follow-up were similar between patient with TAV and BAV. There were no significant differences in the proportions of patients with more than mild PVL or new permanent pacemaker between TAV and BAV morphology throughout the follow-up. Patients with bicuspid morphology might experience less pronounced reverse LV remodeling post-TAVR than patients with tricuspid morphology.     

Non‐invasive measurement of cardiac output by Finometer in patients with cirrhosis

The Finometer measures haemodynamic parameters including cardiac output (CO) using non‐invasive volume‐clamp techniques. The aim of this study was to determine the accuracy of the Finometer in hyperdynamic cirrhotic patients using an invasive indicator dilution technique as control. CO was measured in twenty‐three patients referred for invasive measurements of the hepatic venous pressure gradient on suspicion of cirrhosis. Invasive measurements of CO were performed using indicator dilution technique (CO_I) and simultaneous measurements of CO were recorded with the Finometer (CO_F). In six patients, measurements of CO were performed with invasive technique and the Finometer both before and after β‐blockade using 80 mg of propranolol and the changes in CO (ΔCO_I and ΔCO_F respectively) were calculated to evaluate the Finometers ability to detect relative changes in CO. Mean CO_I was 6·1 ± 1·6 [3·9;9·7] l min^?1 (mean ± SD [range]) compared to mean CO_F of 7·2 ± 2·3 [3·1;11·9] l min^?1. There was a mean difference between CO_F and CO_I of 1·0 ± 1·8 [?2·1;4·0] l min^?1 and 95% confidence interval of [0·2;1·8], P<0·001. In patients with measurements before and after β‐blockade, mean ΔCO_I was 1·6 ± 1·4 [?0·1;3·3] l min^?1 compared to mean ΔCO_F of 1·9 ± 1·3 [0·4;3·8] l min^?1. Mean difference between ΔCO_F and ΔCO_I was 0·3 ± 0·3 [?0·2;0·7] l min^?1 with a 95% confidence interval of [?0·1;0·6], P = 0·11. Compared with invasive measurements, the Finometer can be used to measure changes in CO, whereas absolute measurements are associated with higher variation in patients with cirrhosis. The Finometer seems useful for repeated determinations such as in studies of effect of pharmacotherapy.     

Aortic Elastic Properties of Patients with Neurocardiogenic Syncope

Objective: Neurocardiogenic syncope (NCS) is a common clinical problem; however, hemodynamic mechanism is not clearly understood. Aim of the present study was to investigate aortic elastic parameters of patients with NCS provoked by head‐up tilt test. Material and Method: We conducted a prospective study of 40 cases referred to our institution for head‐up tilt testing. Group I constituted as 22 patients who developed mixed response and were enrolled for analysis. Hemodynamic data were compared with subjects of negative head‐up tilt test (Group II). Aorta‐diastolic and aorta‐systolic diameters, aortic strain, aortic distensibility, aortic elastic modulus, and aortic stiffness index were calculated from transthoracic echocardiographically derived diameters of thoracic aorta. Results: Aortic distensibility (mean ± SD; 2.7 ± 1.2 cm²× dyn^?1× 10^?6 vs 4.0 ± 1.2 cm²× dyn^?1× 10^?6, P = 0,003) and aortic strain index (mean ± SD; 7.0 ± 1.8% vs 8.7 ± 2.9%, P = 0.042) were lower, and aortic stiffness index (mean ± SD; 27.6 ± 10.9 vs 20.9 ± 6.18, P = 0.035) and aortic elastic modulus (mean ± SD; 0.94 ± 0.7 cm²× dyn^?1× 10^?6 vs 0.49 ± 0.1 cm²× dyn^?1× 10^?6, P = 0.009) were higher in patients in Group I compared with those in Group II. There was no difference between two groups for following clinical variables: aorta‐diastolic and aorta‐systolic diameters, systolic and diastolic blood pressure, pulse pressure, E/A, weight, height, and body mass index. Conclusions: Findings of this study have shown that elastic properties of aorta are impaired in patients with NCS. The data suggest that increase in aortic stiffness might be one of the determinants responsible for NCS. This proposal of novel link should be confirmed in further studies.     

Acute resistance exercise using free weights on aortic wave reflection characteristics

Aortic wave reflection characteristics such as the augmentation index (AIx), wasted left ventricular pressure energy (ΔE_w) and aortic haemodynamics, such as aortic systolic blood pressure (ASBP), strongly predict cardiovascular events. The effects of acute resistance exercise (ARE) using free‐weight exercises on these characteristics are unknown. Therefore, we sought to determine the effects of acute free‐weight resistance exercise on aortic wave reflection characteristics and aortic haemodynamics in resistance‐trained individuals. Fifteen young, healthy resistance‐trained (9 ± 3 years) individuals performed two randomized sessions consisting of an acute bout of free‐weight resistance exercise (ARE) or a quiet control (CON). The ARE consisted of three sets of 10 repetitions at 75% one repetition maximum for squat, bench press and deadlift. In CON, the participants rested in the supine position for 30 min. Measurements were made at baseline before sessions and 10 min after sessions. A two‐way ANOVA was used to compare the effects of condition across time. There were no significant interactions for aortic or brachial blood pressures. Compared to rest, there were significant increases in augmentation pressure (rest: 5·7 ± 3·0 mmHg; recovery: 10·4 ± 5·7 mmHg, P = 0·002), AIx (rest: 116·8 ± 4·2%; recovery: 123·2 ± 8·4%, P = 0·002), AIx normalized at 75 bpm (rest: 5·2 ± 7·6%; recovery: 27·3 ± 13·2%, P<0·0001), ΔE_w (rest: 1215 ± 674 dynes s cm^?2; recovery: 2096 ± 1182 dynes s cm^?2, P = 0·008), and there was a significant decrease in transit time of the reflected wave (rest: 150·7 ± 5·8 ms; recovery 145·5 ± 5·6 ms, P<0·001) during recovery from ARE compared to CON. These data suggest that ARE using free‐weight exercises may have no effect on aortic and brachial blood pressure but may significantly alter aortic wave reflection characteristics.     

Circulatory response to single circuit weight and walking training sessions of similar energy cost in middle‐aged overweight females

The aim of this study was to compare circulatory responses to circuit weight (CWT) and aerobic walking training sessions of similar energy cost in middle‐aged overweight females. Thirty‐three middle‐aged pre‐menopausal females participated in the experiment. They were divided into overweight (n=18, 36·2 ± 6·3 years, 166·3 ± 8·0 cm, 83·5 ± 9·7 kg, BMI 30·2 ± 3·1 kg m^–2) and non‐overweight control (n=15, 34·1 ± 6·3 years, 165·0 ± 5·6 cm, 61·6 ± 5·0 kg, BMI 22·7 ± 1·5 kg m^–2) groups. Individual physical working capacity (PWC) was measured using the cycle ergometer test (calculated at the level of predicted HR_max (205 – ½ age). A CWT session consisted of leg extension, bench press, sit‐ups and leg press exercises. The subjects performed four circuits at the maximal possible speed, using a work‐to‐rest ratio of 60 s. Blood pressure (BP) was measured during every rest period between the exercises, and the heart rate (HR) was recorded continuously during the whole CWT programme. During the walking training session, the subjects walked as fast as possible on the indoor track. The total energy cost of the walking training session was the same as during the CWT session, approximately 270 kcal, and was controlled by a CALTRAC accelerometer. HR and BP were measured every 5 min during the walking training session. The PWC index was significantly (P<0·05) higher in the overweight group in comparison with the control females (215·4 ± 76·1 and 187·9 ± 42·4 W, respectively). The resting BP was normal in both groups (<140/90 mmHg). HR was between 120 and 140 beats min^–1 during CWT and walking sessions. There were no differences in BP during both training sessions in overweight and control subjects. It was concluded that both CWT and walking training sessions were acceptable forms of physical activity to increase cardiovascular fitness in middle‐aged overweight and normal body weight females.     

Increased serum angiotensin converting enzyme activity in type T insulin—dependent diabetes mellitus: its relation to metabolic control and diabetic complications

Abstract. Serum angiotensin-converting enzyme (ACE) was measured in 150 insulin-dependent diabetes mellitus (IDDM) patients and 72 healthy subjects by radioassay, using [³H]-hippuryl-glycyl-glycine as a substrate. Mean (SD) serum ACE activity in diabetic patients was 120 ± 33 nmol ml^?1 min^?1 (range 46–215) and was significantly increased by 56% compared to control values (77 ± 23 nmol ml^?1 min^?1, range 46–125, P < 0·001). ACE activity > 125 nmol ml^?1 min^?1 was observed in 60 of 150 IDDM patients. 96 IDDM patients were normoalbuminuric (< 22 mg 24 h^?1) and 49 patients were micro- or macroalbuminuric (range 22–6010 mg 24 h^?1). Micro- and macroalbuminuric IDDM patients were found to have significantly greater ACE activity values than normoalbuminuric patients (128 ± 36 vs. 115 ± 30 nmol ml^?1 min^?1, P = 0·025). Metabolically well-controlled IDDM patients (glycosylated haemoglobin ≤ 8%) had lower ACE activity values than the patients with glycosylated haemoglobin greater than 8% (109 ± 20 vs. 127 ± 32 nmol ml^?1 min^?1, P < 0·02). A significant correlation between degree of metabolic control and ACE activity was found (r = 0.435, P < 0·001) so that an increase in one glycosylated quartile unit is accompanied by an increase in ACE activity of 10·5 nmol ml^?1 min^?1. Thus ACE activity in the serum of IDDM patients was increased by 56% in 40% of the patients. It was increased in IDDM patients without complications and in patients with retinopathy or nephropathy. In diabetic patients with nephropathy, ACE activity was greater than in diabetic patients without nephropathy. ACE activity was positively correlated with metabolic control. The role of increased ACE activity in the development of diabetic nephropathy remains to be established.