Effects Of Age And Conditioning Status On Rest And Exercise Cardiac Performance

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Effective arterial elastance (EA) is a measure of the net arterial load imposed on the heart that integrates the effects of heart rate(HR), peripheral vascular resistance(PVR), and total arterial compliance(TAC) and is a modulator of cardiac performance. To what extent the change in EA during exercise impacts on cardiac performance and aerobic capacity is unknown. We examined EA and its relationship with cardiovascular performance in 352 healthy subjects (Chantler et al. 2012). Subjects underwent rest and exercise gated scans to measure cardiac volumes and to derive EAend-systolic pressure/stroke volume index(SV), PVRMAP/(SV*HR), and TAC(SV/pulse pressure). EA varied with exercise intensity: the EA between rest and peak exercise along with its determinants, differed among individuals and ranged from -44% to +149%, and was independent of age and sex. Individuals were separated into 3 groups based on their EAI. Individuals with the largest increase in EA(group 3;EA0.98 mmHg.m2/ml) had the smallest reduction in PVR, the greatest reduction in TAC and a similar increase in HR vs. group 1(EA<0.22 mmHg.m2/ml). Furthermore, group 3 had a reduction in end-diastolic volume, and a blunted increase in SV(80%), and cardiac output(27%), during exercise vs. group 1. Despite limitations in the Frank-Starling mechanism and cardiac function, peak aerobic capacity did not differ by group because arterial-venous oxygen difference was greater in group 3 vs. 1. Thus the change in arterial load during exercise has important effects on the Frank-Starling mechanism and cardiac performance but not on exercise capacity. These findings provide interesting insights into the dynamic cardiovascular alterations during exercise. Another study (Marine et al. 2013) sought to determine the clinical predictors and prognostic significance of exercise-induced nonsustained ventricular tachycardia (NSVT) in a large population of asymptomatic volunteers. Subjects in the BLSA (Baltimore Longitudinal Study of Aging) free of known cardiovascular disease who completed at least 1 symptom-limited exercise treadmill test between 1977 and 2001 were included. NSVT episodes were characterized by QRS morphology, duration, and rate. Subjects underwent follow-up clinical evaluation every 2 years. The 2,099 subjects (mean age: 52 years; 52.2% male) underwent a mean of 2.7 exercise tests, in which 79 (3.7%) developed NSVT with exercise on at least 1 test. The median duration of NSVT was 3 beats (5 beats in 84%), and the median rate was 175 beats/min. Subjects with (vs. without) NSVT were older (67 12 years vs. 51 17 years, p < 0.0001) and more likely to be male (80% vs. 51%, p < 0.0001) and to have baseline electrocardiographic abnormalities (50% vs. 17%, p < 0.0001) or ischemic ST-segment changes with exercise (20% vs. 10%, p 1/4 0.004). Over a mean follow-up of 13.5 7.7 years, 518 deaths (24.6%) occurred. After multivariable adjustment for age, sex, and coronary risk factors, exercise-induced NSVT was not significantly associated with total mortality (hazard ratio: 1.30; 95% confidence interval: 0.89 to 1.90; p 1/4 0.17). Exercise-induced NSVT occurred in nearly 4% of this asymptomatic adult cohort. This finding increased with age and was more common in men. After adjustment for clinical variables, exercise-induced NSVT did not independently increase the risk of total mortality. It is unclear whether subcutaneous and visceral fat are differentially correlated to the decline in left ventricular (LV) diastolic function with aging. A study (Canepa et al. 2013) sought to examine the hypothesis that age-related changes in the regional fat distribution account for changes in LV diastolic function and to explore potential mediators of this association. In a cross-sectional study, we evaluated 843 participants of the Baltimore Longitudinal Study of Aging with echocardiogram, dual-energy X-ray absorptiometry (DEXA), abdominal computed tomography (CT) and blood tests performed at the same visit. LV diastolic function was assessed by parameters of LV relaxation (E/A ratio, Em and Em/Am ratio) and LV filling pressures (E/Em ratio). Total body fat was computed by DEXA, while visceral and subcutaneous fat were determined from abdominal CT. In multivariate models adjusted for demographics, cardiovascular risk factors, antihypertensive medications, physical activity and LV mass, both visceral and subcutaneous fat were associated with LV diastolic dysfunction. When both measures of adiposity were simultaneously included in the same model, only visceral fat was significantly associated with LV diastolic dysfunction. Triglycerides and sex-hormone binding globulin, but not adiponectin and leptin, were found to be significant mediators of the relationship between visceral fat and LV diastolic function, explaining 2847% of the association. Bootstrapping analyses confirmed the significance of these findings. Conclusions: Increased visceral adiposity is associated with LV diastolic dysfunction, possibly through a metabolic pathway involving blood lipids and ectopic fat accumulation rather than adipokines. Arterial aging may link cardiovascular risk to white coat hypertension (WCH). A study (Sung et al. 2013) investigated the role of arterial aging in the white coat effect, defined as the difference between office and 24-hour ambulatory systolic blood pressures, and to compare WCH with prehypertension (PH) with respect to target organ damage and long-term cardiovascular mortality. A total of 1257 never-been-treated volunteer subjects from a community-based survey were studied. WCH and PH were defined by office and 24-hour ambulatory blood pressures. Left ventricular mass index, carotid intima-media thickness, estimated glomerular filtration rate, carotid-femoral pulse wave velocity, carotid augmentation index, amplitude of the reflection pressure wave, and 15-year cardiovascular mortality were determined. Subjects with WCH were significantly older and had greater body mass index, blood pressure values, intima-media thickness, carotid-femoral pulse wave velocity, augmentation index, amplitude of the backward pressure wave, and a lower estimated glomerular filtration rate than PH. Amplitude of the backward pressure wave was the most important independent correlate of the white coat effect in multivariate analysis (model r2=0.451; partial r2/model r2=90.5%). WCH had significantly greater cardiovascular mortality than PH (hazard ratio, 2.94; 95% confidence interval, 1.097.91), after accounting for age, sex, body mass index, smoking, fasting plasma glucose, and total cholesterol/high-density lipoprotein-cholesterol ratio. Further adjustment of the model for amplitude of the backward pressure wave eliminated the statistical significance of the WCH effect. In conclusion, the white coat effect is mainly caused by arterial aging. WCH carries higher risk for cardiovascular mortality than PH, probably via enhanced wave reflections that accompany arterial aging.