Brage Høyem Amundsen

Non-invasive imaging methods like echocardiography and magnetic resonance imaging (MRI) are very valuable in longitudinal follow-up studies of cardiac function in small animals. To be able to compare results from studies using different methods, and explain possible differences, it is important to know the agreement between these methods. As both self-gated high-field MRI and high-frequency echocardiography (hf-echo) M-mode are potential methods for evaluation of left ventricular (LV) function in healthy mice, our aim was to assess the agreement between these two methods. Fifteen healthy female C57BL/6J mice underwent both self-gated MRI and hf-echo during the same session of light isoflurane anaesthesia. LV dimensions were estimated offline, and agreement between the methods and reproducibility for the two methods assessed using Bland–Altman methods. In summary, hf-echo M-mode had better inter-observer repeatability than self-gated MRI for all measured parameters. Compared with hf-echo, systolic posterior wall thicknesses were significantly higher when measured by MRI, while diastolic anterior wall thicknesses were found to be significantly smaller. MRI measurements of diastolic LV diameter were also higher using MRI, resulting in larger fractional shortening values compared with the values obtained by hf-echo. In conclusion, hf-echo M-mode is easy to apply, has high temporal and spatial resolution, and good reproducibility. Self-gated MRI might be advantageous in cases of abnormal LV geometry and heterogeneous regional myocardial function, especially with improvements in spatial resolution. The moderate agreement between the methods must be taken into account when comparing studies using the two modalities.

Maximal strength training with a focus on maximal mobilization of force in the concentric phase improves endurance performance that employs a large muscle mass. However, this has not been studied during work with a small muscle mass, which does not challenge convective oxygen supply. We therefore randomized 23 adult females with no arm-training history to either one-arm maximal strength training or a control group. The training group performed five sets of five repetitions of dynamic arm curls against a near-maximal load, 3 days a week for 8 weeks. This training increased maximal strength by 75% and improved rate of force development during both strength and endurance exercise, suggesting that each arm curl became more efficient. This coincided with a 17–18% reduction in oxygen cost at standardized submaximal workloads (work economy), and a 21% higher peak oxygen uptake and 30% higher peak load during maximal arm endurance exercise. Blood flow assessed by Doppler ultrasound in the axillary artery supplying the working biceps brachii and brachialis muscles could not explain the training-induced adaptations. These data suggest that maximal strength training improved work economy and endurance performance in the skeletal muscle, and that these effects are independent of convective oxygen supply.

Objectives. Previous reports suggest that left myocardial ventricular function changes during the course of a subarachnoid haemorrhage. The aim of this study was to evaluate left myocardial ventricular function with tissue Doppler echocardiography at two time points during the acute phase of a subarachnoid haemorrhage. Design. Eighteen consecutive patients (median 52 years, range 33–74) with spontaneous subarachnoid haemorrhage and no history of heart disease were examined at 1–5 days and at 6–11 days following ictus. Eighteen control subjects were included for comparison (52 years, 32–72). Results. Tissue Doppler indices of left ventricular contractility were higher in patients than in controls at both examinations (pConclusion. In patients with subarachnoid haemorrhage, systolic and diastolic function is increased compared to healthy controls, suggesting a hyperdynamic and hypervolemic circulation.

Aims The aim of this feasibility study was to compare systolic and diastolic left ventricular (LV) function during upright bicycle exercise in patients with chronic myocardial infarction (MI). Methods and results Eighteen patients with first-time MI and no signs of heart failure at rest underwent upright bicycle exercise at 25, 50, and 75 W, and were compared with 18 age-matched controls. Systolic (S′) and early (E′) mitral annular velocities and early mitral filling velocity (E) were measured at each stage. LV ejection fraction was lower in the MI group (46 vs. 54%, P < 0.01), while end-diastolic volumes were similar. S′ was lower in the MI patients, but increased during exercise in both groups. E′ was similar at rest, but increased in the control group only. Early mitral filling (E) increased in both groups, thus the E/E′ ratio increased during exercise in the MI group only. Heart rate was similar in both groups. Conclusions Upright exercise echocardiography is feasible and can unmask early diastolic dysfunction and increased LV filling pressures in patients with small prior MIs.

Compare four different echocardiographic methods, based on tissue Doppler imaging (TDI) and speckle tracking (ST) separately or combined, for long-axis strain and strain rate (SR) measurements, using magnetic resonance imaging (MRI) tagging as a reference. In 21 subjects (10 with myocardial infarction) peak systolic strain and systolic and early diastolic SR were measured by four different echo methods: (i) two-dimensional (2D) strain (B-mode); (ii) ST (custom software) of segment end-points (B-mode); (iii) similar to (ii), but combining ST with tissue Doppler tracking; (iv) strain from tissue Doppler velocity gradients (VG). Agreement with MRI tagging was better for strain than for SR. Ninety-five per cent limits of agreement were wider for the TDI-VG method, and 2D strain showed negative bias compared with MRI tagging and the other echo methods. Reproducibility was better for 2D strain than for MRI tagging and the other echo methods. ST alone or combined with TDI seems to be suitable for automated measurements of regional myocardial deformation. The study gives important information on the strengths and weaknesses of the different methods, which is important for further development to increase accuracy and applicability.

Objective. To study the effect of aerobic treadmill exercise training with different intensity on left ventricular (LV) function in patients with stable coronary artery disease, using Strain Rate- and Tissue Doppler Imaging. Design. Seventeen patients were randomly assigned to either moderate (50–60% of peak oxygen uptake (VO_2peak)) or high intensity exercise (80–90% of VO_2peak) for 10 weeks. Results. The increase of VO_2peak was significantly higher (p=0.01) in the high intensity group (17 vs. 8%). Mean LV early diastolic strain rate increased in the high, but not in the moderate, intensity group. For systolic strain rate or mitral annular velocities there were no change after training in either group. Conclusions. Aerobic treadmill exercise improves early diastolic relaxation in patients with stable coronary artery disease, measured by the mean LV early diastolic strain rate.

Physical activity and exercise training are effective in prevention, treatment and rehabilitation of cardiovascular disease, but the dose-response relationship is insufficiently documented. The manuscript is based on existing guidelines and searches in Pubmed for the period 1990-2006. Exercise training improves maximum oxygen consumption and prognosis in patients with cardiovascular disease. A single weekly bout of exercise reduces mortality from stroke and ischemic heart disease, but larger doses may provide additional protection. In patients with coronary heart disease, high intensity exercise seems to be more effective in improving maximal oxygen consumption than moderate exercise, but it is not known if such exercise is also more effective in improving survival. Further studies are also required to establish the safety of such exercise. Exercise has few contraindications, but patients should be screened in advance with an exercise-ECG. Future studies should to a larger extent include female, elderly and high-risk patients, and be precise in prescribing and reporting exercise intensity, duration and frequency. Maximum oxygen consumption is an accurate measure of cardiovascular fitness and a strong and independent prognostic marker for survival, both in patients and healthy subjects.