Assessment of the effect of endurance training on left ventricular relaxation with magnetic resonance imaging

Effects of a low-volume aerobic-type interval exercise on VO2max and cardiac mass

PURPOSE

The aim of this study was to compare the effects of time-efficient, low-volume interval exercises on cardiorespiratory capacity and left ventricular (LV) mass with traditional continuous exercise in sedentary adults.

METHODS

Forty-two healthy but sedentary male subjects (age 26.5 ± 6.2 yr) participated in an 8-wk, five times per week, supervised exercise intervention. They were randomly assigned to one of three exercise protocols: sprint interval training (SIT, 5 min, 100 kcal), high-intensity interval aerobic training (HIAT, 13 min, 180 kcal), and continuous aerobic training (CAT, 40 min, 360 kcal). Cardiorespiratory capacity (V˙O2max) and LV mass (3T-MRI) were measured preintervention and postintervention.

RESULTS

We observed significant (P < 0.01) increases in V˙O2max in all three groups, and the effect of the HIAT was the greatest of the three (SIT, 16.7% ± 11.6%; HIAT, 22.5% ± 12.2%; CAT, 10.0% ± 8.9%; P = 0.01). There were significant changes in LV mass, stroke volume (SV), and resting HR in both the SIT (LV mass, 6.5% ± 8.3%; SV, 5.3% ± 8.3%; HR, -7.3% ± 11.1%; all P < 0.05) and HIAT (LV mass, 8.0% ± 8.3%; SV, 12.1% ± 9.8%; HR, -12.7% ± 12.2%; all P < 0.01) but not in the CAT (LV mass, 2.5% ± 10.1%; SV, 3.6% ± 6.6%; HR, -2.2% ± 13.3%; all P > 0.05).

CONCLUSIONS

Our study revealed that V˙O2max improvement with the HIAT was greater than with the CAT despite the HIAT being performed with a far lower volume and in far less time than the CAT. This suggests that the HIAT has potential as a time-efficient training mode to improve V˙O2max in sedentary adults.

Exercise-induced interstitial pulmonary edema at sea-level in young and old healthy humans

We asked whether aged adults are more susceptible to exercise-induced pulmonary edema relative to younger individuals. Lung diffusing capacity for carbon monoxide (DLCO), alveolar-capillary membrane conductance (Dm) and pulmonary-capillary blood volume (Vc) were measured before and after exhaustive discontinuous incremental exercise in 10 young (YNG; 27±3 years) and 10 old (OLD; 69±5 years) males. In YNG subjects, Dm increased (11±7%, P=0.031), Vc decreased (-10±9%, P=0.01) and DLCO was unchanged (30.5±4.1 vs. 29.7±2.9mL/min/mmHg, P=0.44) pre- to post-exercise. In OLD subjects, DLCO and Dm increased (11±14%, P=0.042; 16±14%, P=0.025) but Vc was unchanged (58±23 vs. 56±23mL, P=0.570) pre- to post-exercise. Group-mean Dm/Vc was greater after vs. before exercise in the YNG and OLD subjects. However, Dm/Vc was lower post-exercise in 2 of the 10 YNG (-7±4%) and 2 of the 10 OLD subjects (-10±5%). These data suggest that exercise decreases interstitial lung fluid in most YNG and OLD subjects, with a small number exhibiting evidence for exercise-induced pulmonary edema.

Short-term exercise training improves the cardiovascular response to exercise in the postural orthostatic tachycardia syndrome

Recent studies have suggested the presence of cardiac atrophy as a key component of the pathogenesis of the postural orthostatic tachycardia syndrome (POTS), similar to physical deconditioning. It has also been shown that exercise intolerance is associated with a reduced stroke volume (SV) in POTS, and that the high heart rate (HR) observed at rest and during exercise in these patients is due to this low SV. We tested the hypotheses that (a) circulatory control during exercise is normal in POTS; and (b) that physical ‘reconditioning' with exercise training improves exercise performance in patients with POTS. Nineteen (18 women) POTS patients completed a 3 month training programme. Cardiovascular responses during maximal exercise testing were assessed in the upright position before and after training. Resting left ventricular diastolic function was evaluated by Doppler echocardiography. Results were compared with those of 10 well-matched healthy sedentary controls. A lower SV resulted in a higher HR in POTS at any given oxygen uptake (V(O(2))) during exercise while the cardiac output (Q(c))-V(O(2)) relationship was normal. V(O(2peak)) was lower in POTS than controls (26.1 ± 1.0 (SEM) vs. 36.3 ± 0.9 ml kg-1 min-1; P < 0.001) due to a lower peak SV (65 ± 3 vs. 80 ± 5 ml; P = 0.009). After training in POTS, HR became lower at any given due to increased SV without changes in the – relationship. V(O(2peak)) increased by 11% (P < 0.001) due to increased peak SV (P = 0.021) and was proportional to total blood volume. Peak HR was similar, but HR recovery from exercise was faster after training than before training (P = 0.036 for training and 0.009 for interaction). Resting diastolic function was mostly normal in POTS before training, though diastolic suction was impaired (P = 0.023). There were no changes in any Doppler index after training. These results suggest that short-term exercise training improves physical fitness and cardiovascular responses during exercise in patients with POTS.

The pulmonary circulation and exercise responses in the elderly

Aging is associated with a progressive deterioration in the structure and function of the pulmonary circulation. Remodeling of the pulmonary vasculature occurs from maturity to senescence that is characterized by an increase in pulmonary vascular stiffness, pulmonary vascular pressures, and pulmonary vascular resistance along with increased heterogeneity of alveolar ventilation and pulmonary perfusion and decreased pulmonary capillary blood volume and membrane diffusing capacity that is consistent with a reduction in alveolar-capillary surface area. In theory, the aforementioned age-related changes in the pulmonary circulation may conspire to make elderly individuals more susceptible to gas exchange abnormalities during exercise. However, despite the erosion in ventilatory reserve with aging, the healthy older adult appears able to maintain alveolar ventilation at a level that allows maintenance of arterial blood gases within normal limits, even during heavy exercise. This ability to maintain adequate gas exchange likely occurs because age-related reductions in the maximal metabolic demand of exercise occur at a rate equal to or greater than the rate of deterioration in ventilatory reserve. A more prominent aspect of aging is the loss of lung elastic recoil that is associated with a modest reduction in the expiratory boundary of the maximal flow-volume envelope. This in turn increases the severity of expiratory airflow limitation and induces dynamic lung hyperinflation during exercise. The consequences of this age-associated decrease in elastic recoil on the pulmonary circulation are speculative, but an age-associated decline in elastic recoil may influence pulmonary vascular resistance and cardiac output, in addition to its impact on the work and oxygen cost of breathing.

Improved ejection fraction after exercise training in obesity is accompanied by reduced cardiac lipid content

CONTEXT

Skeletal muscle and cardiac lipid accumulation are associated with diminished insulin sensitivity and cardiac function, respectively. In skeletal muscle, physical activity paradoxically increases fat accumulation, despite improvement in insulin sensitivity. Whether cardiac muscle responds similarly remains unknown.

OBJECTIVE

The objective of the study was to investigate cardiac lipid content and cardiac function after a 12-wk training program.

DESIGN

This was an intervention study with pre/postmeasurements.

SETTING

The study was conducted at Maastricht University Medical Center.

PARTICIPANTS

Participants included 14 healthy, male overweight/obese subjects (age 58.4 +/- 0.9 yr, body mass index 29.9 +/- 0.01 kg/m(2)).

INTERVENTION

Intervention included a supervised 12-wk training program with three sessions per week (endurance and strength training).

MAIN OUTCOME MEASURES

Maximal whole-body oxygen uptake, fasting plasma parameters, systolic function (by CINE-magnetic resonance imaging), and cardiac lipid content (by proton magnetic resonance spectroscopy) were measured.

RESULTS

Maximal whole-body oxygen uptake increased (from 2559 +/- 131 to 2702 +/- 124 ml/min after training, P = 0.05). Plasma concentrations of glucose decreased (from 6.3 +/- 0.2 to 5.7 +/- 0.2 mmol/liter, P < 0.001); plasma triacylglycerols and (free) fatty acids did not change. Also, body weight (from 94.2 +/- 3.6 to 92.9 +/- 3.6 kg, P = 0.10) and fat percentage (from 33.6 +/- 1.7 to 32.5 +/- 2.0%, P = 0.14) was unchanged. Left ventricular ejection fraction improved (from 52.2 +/- 1.3 to 54.2 +/- 1.2%, P = 0.02), and cardiac lipid content in the septum was decreased after training (0.99 +/- 0.15 to 0.54 +/- 0.04%, P = 0.02).

CONCLUSIONS

Twelve weeks of endurance/strength training significantly reduced cardiac lipid content in overweight subjects and was paralleled by improved ejection fraction. This is in line with a lipotoxic action of (excess) cardiac lipids on cardiac function, although a causal relationship cannot be derived from this study. Further research is needed to clarify the clinical relevance of cardiac lipid content in the etiology of cardiovascular complications.

Physical activity and physiological cardiac remodelling in a community setting: the Multi-Ethnic Study of Atherosclerosis (MESA)

OBJECTIVE

To evaluate the association of physical activity with left ventricular structure and function in the general population in a community setting.

DESIGN

Cross-sectional study.

SETTING

The Multi-Ethnic Study of Atherosclerosis (MESA), a population-based study of subclinical atherosclerosis.

PARTICIPANTS

A multiethnic sample of 4992 participants (aged 45-84 years; 52% female) free of clinically apparent cardiovascular disease.

INTERVENTIONS

Physical activity induces beneficial physiological cardiac remodelling in a cross-sectional study of non-athlete individuals.

MAIN OUTCOME MEASURES

Left ventricular mass, volumes and function were assessed by cardiac magnetic resonance imaging. Physical activity, defined as intentional exercise and total moderate and vigorous physical activity, was assessed by a standard semiquantitative questionnaire.

RESULTS

Left ventricular mass and end-diastolic volume were positively associated with physical activity (eg, 1.4 g/m(2) (women) and 3.1 g/m(2) (men) greater left ventricular mass in the highest category of intentional exercise compared with individuals reporting no intentional exercise; p = 0.05 and p<0.001, respectively). Relationships were non-linear, with stronger positive associations at lower levels of physical activity (test for non-linearity; p = 0.02 and p = 0.03, respectively). Cardiac output and ejection fraction were unchanged with increased physical activity levels. Resting heart rate was lower in women and men with higher physical activity levels (eg, -2.6 beats/minute lower resting heart rate in the highest category of intentional exercise compared with individuals reporting no intentional exercise; p<0.001).

CONCLUSIONS

In a community-based population free of clinically apparent cardiovascular disease, higher physical activity levels were associated with proportionally greater left ventricular mass and end-diastolic volume and lower resting heart rate.

Influence of 12 weeks of jogging on magnetic resonance-determined left ventricular characteristics in previously sedentary subjects free of cardiovascular disease

Hypertrophy of the left ventricle is a diagnostic dilemma in subjects who engage in regular endurance exercise. We studied prospectively whether endurance training in previously sedentary young and middle-aged men and women can alter left ventricular (LV) characteristics. We recruited 33 healthy young and middle-aged subjects (18 women, 15 men, ages 21 to 59 years) to undergo 12 weeks of home-based brisk walking and jogging at a target heart rate > or =120 beats/min for > or =30 minutes 3 times a week. LV characteristics were measured by cine magnetic resonance imaging. Training intensity as estimated by heart rate correlated positively with the increase in LV myocardial area (r = 0.51, p = 0.005) in the 28 men and women completing the study. In the 13 men and women who trained with heart rate of > or =120 beats/min, LV myocardial area was larger after than before training (17.7 +/- 2.9 vs 16.8 +/- 2.8 cm(2), p <0.05). Moreover, in these subjects LV myocardial area increased more (5.5 +/- 9.0% vs -3.0 +/- 5.0%) than in the 15 men and women who trained at a lower intensity (p <0.05). LV end-systolic and end-diastolic area and ejection fraction did not change significantly. In conclusion, moderate-to-vigorous endurance training at moderate volumes does not influence LV end-diastolic volume or ejection fraction, but has a minor influence on LV hypertrophy in previously sedentary young and middle-aged men and women.

Myocardial function in patients with Shwachman-Diamond syndrome: aspects to consider before stem cell transplantation

BACKGROUND

Early studies have suggested increased risk of fatal cardiac complications in infants with Shwachman-Diamond syndrome (SDS), an inherited bone marrow failure syndrome. Patients undergoing stem cell transplantation (STC) have appeared susceptible to organ toxicity, including cardiac involvement.

PROCEDURE

This study assessed anatomical and functional features of the heart in SDS. Eight patients (mean age 24.1 years, range 7-37 years, seven males) with SDS and confirmed SBDS mutations were prospectively assessed for cardiac anatomy, myocardial wall properties, and systolic and diastolic function. The study protocol included conventional echocardiography (n = 8) complemented by exercise Tissue-Doppler echocardiography (n = 7), and by MRI (n = 6).

RESULTS

No abnormalities in cardiac anatomy or function were observed in baseline clinical assessment, EKG, or conventional echocardiographic and MRI measurements. Myocardial structure and left ventricular (LV) mass were normal. The maximum isovolumic acceleration (IVA) value during exercise in Tissue-Doppler was significantly lower (P < 0.001), and the right ventricular (RV) ejection fraction (P = 0.02) and peak filling rate (PFR, P = 0.008) at rest in MRI were higher in patients.

CONCLUSIONS

Children and young adults with SDS and mutations in SBDS had normal cardiac anatomy and myocardial structure. Subtle RV diastolic function alterations at rest and depressed LV contractility during exercise were observed. Further studies are warranted to evaluate the clinical importance of these findings.