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In heart transplant (HTx) recipients, there has been reluctance to recommend high-intensity interval training (HIIT) due to denervation and chronotropic impairment of the heart. We compared the effects of 12 weeks' HIIT versus continued moderate exercise (CON) on exercise capacity and chronotropic response in stable HTx recipients >12 months after transplantation in a randomized crossover trial. The study was completed by 16 HTx recipients (mean age 52 years, 75% males). Baseline peak oxygen uptake (VO 2peak ) was 22.9 mL/kg/min. HIIT increased VO 2peak by 4.9 AE 2.7 mL/min/kg (17%) and CON by 2.6 AE 2.2 mL/ kg/min (10%) (significantly higher in HIIT; p < 0.001). During HIIT, systolic blood pressure decreased significantly (p ¼ 0.037) with no significant change in CON (p ¼ 0.241; between group difference p ¼ 0.027). Peak heart rate (HR peak ) increased significantly by 4.3 beats per minute (p ¼ 0.014) after HIIT with no significant change in CON (p ¼ 0.34; between group difference p ¼ 0.027). Heart rate recovery (HR recovery ) improved in both groups with a trend toward greater improvement after HIIT. The 5-month washout showed a significant loss of improvement. HIIT was well tolerated, had a superior effect on oxygen uptake, and led to an unexpected increase in HR peak accompanied by a faster HR recovery . This indicates that the benefits of HIIT are partly a result of improved chronotropic response.Abbreviations: absolute VO 2peak , peak oxygen uptake (mL/min); bpm, beats per minute; CON, continued moderate exercise; DBP, diastolic blood pressure; HIIT, high-intensity interval training; HR, heart rate; HR peak , peak heart rate; HR recovery , heart rate recovery; HR reserve , heart rate reserve; HR rest , resting heart rate; HTx, heart transplant; RER, respiratory exchange ratio; SBP, systolic blood pressure; SET, strength and endurance training; VO 2peak , peak oxygen uptake (mL/min/kg)

In this group of heart failure patients, VO2 peak was correlated with CFR, E/e', and s' but not with traditional measures of systolic function. CFR remained associated with VO2 peak independently of diastolic and systolic function and is likely to be a limiting factor in functional capacity of heart failure patients.

BackgroundInsulin resistance has been linked to exercise intolerance in heart failure patients. The aim of this study was to assess the potential role of coronary flow reserve (CFR), endothelial function and arterial stiffness in explaining this linkage.Methods39 patients with LVEF < 35% (median LV ejection fraction (LVEF) 31 (interquartile range (IQ) 26–34), 23/39 of ischemic origin) underwent echocardiography with measurement of CFR. Peak coronary flow velocity (CFV) was measured in the LAD and coronary flow reserve was calculated as the ratio between CFV at rest and during a 2 minutes adenosine infusion. All patients performed a maximal symptom limited exercise test with measurement of peak oxygen uptake (VO2peak), digital measurement of endothelial function and arterial stiffness (augmentation index), dual X-ray absorptiometry scan (DEXA) for body composition and insulin sensitivity by a 2 hr hyperinsulinemic (40 mU/min/m2) isoglycemic clamp.ResultsFat free mass adjusted insulin sensitivity was significantly correlated to VO2peak (r = 0.43, p = 0.007). Median CFR was 1.77 (IQ 1.26-2.42) and was correlated to insulin sensitivity (r 0.43, p = 0.008). CFR (r = 0.48, p = 0.002), and arterial stiffness (r = −0.35, p = 0.04) were correlated to VO2peak whereas endothelial function and LVEF were not (all p > 0.15). In multivariable linear regression adjusting for age, CFR remained independently associated with VO2peak (standardized coefficient (SC) 1.98, p = 0.05) whereas insulin sensitivity (SC 1.75, p = 0.09) and arterial stiffness (SC −1.17, p = 0.29) were no longer associated with VO2peak.ConclusionsThe study confirms that insulin resistance is associated with exercise intolerance in heart failure patients and suggests that this is partly through reduced CFR. This is the first study to our knowledge that shows an association between CFR and exercise capacity in heart failure patients and links the relationship between insulin resistance and exercise capacity to CFR.

The study does not support a role of diastolic dysfunction in the limited exercise capacity of HTx recipients and suggests that in these patients peripheral factors are of greater importance.

Lifelong endurance running was not found to be associated with major attenuation of the age-related decline in diastolic function at rest or during exercise.

Coronary flow reserve measured noninvasively predicts cardiopulmonary fitness independently of resting systolic and diastolic function in CAD patients, indicating that cardiac output during maximal exercise is dependent on the ability of the coronary circulation to adapt to the higher metabolic demands of the myocardium.

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: To assess the beneficial and harmful effects of antibiotics for the secondary prevention of coronary heart disease. As a secondary objective, we plan to assess the effects of individual types of antibiotics for the secondary prevention of coronary heart disease.