Graeme Carrick-Ranson

Impact of lifelong exercise "dose" on left ventricular compliance and distensibility.

BACKGROUNDnSedentary aging has deleterious effects on the cardiovascular system, including decreased left ventricular compliance and distensibility (LVCD). Conversely, Masters level athletes, who train intensively throughout adulthood, retain youthful LVCD.nnnOBJECTIVESnThe purpose of this study was to test the hypothesis that preservation of LVCD may be possible with moderate lifelong exercise training.nnnMETHODSnHealthy seniors (nxa0= 102) were recruited from predefined populations, screened for lifelong patterns of exercise training, and stratified into 4 groups: sedentary (<2 sessions/week); casual (2 to 3 sessions/week); committed (4 to 5 sessions/week); and competitive Masters level athletes (6 to 7 sessions/week). Right heart catheterization and echocardiography were performed while preload was manipulated using lower body negative pressure and rapid saline infusion to define LV pressure-volume relationships and Frank-Starling curves.nnnRESULTSnPeak oxygen uptake and LV mass increased with escalating doses of lifelong exercise, with little change in systolic function. At baseline, LV distensibility was greater in committed (21%) and competitive (36%) exercisers than in sedentary subjects. Group LV stiffness constants (sedentary: 0.062 ± 0.039; casual: 0.079 ± 0.052; committed: 0.055 ± 0.033; and competitive: 0.035 ± 0.033) revealed: 1) increased stiffness in sedentary subjects compared to competitive athletes, whereas lifelong casual exercise had no effect; and 2) greater compliance in committed exercisers than in sedentary or casual exercisers.nnnCONCLUSIONSnLow doses of casual, lifelong exercise do not prevent the decreased compliance and distensibility observed with healthy, sedentary aging. In contrast, 4 to 5 exercise sessions/week throughout adulthood prevent most of these age-related changes. As LV stiffening has been implicated in the pathophysiology of many cardiovascular conditions affecting the elderly, this dose of exercise training may have important implications for prevention of cardiovascular disease.

Effect of ageing on left ventricular compliance and distensibility in healthy sedentary humans

Key pointsu2002 •u2002 Healthy sedentary ageing leads to stiffening of the heart; however, when this process occurs during ageing has been unknown. •u2002 In this study, 70 healthy sedentary subjects were stratified into four groups: ‘young’– G21−34: 21–34 years; ‘early middle‐age’– G35−49: 35–49 years; ‘late middle‐age’– G50−64: 50–64 years; and ‘seniors’– G≥65: ≥65 years. •u2002 Invasive catheter measurements showed a substantially greater left ventricular (LV) compliance (more flexible/less stiff) in G21−34 than G50−64 and G≥65. •u2002 Although LV chamber compliance in G50−64 and G≥65 appeared identical, pressure–volume curves were shifted leftward, exhibiting a smaller volume for any given pressure with increasing age. •u2002 Our results suggest that LV stiffening with ageing occurs during the transition between youth and middle‐age and becomes manifest between the ages of 50–64; LV volume contraction and remodelling follow in the senior years. Early–late middle age thus may represent a ‘sweet spot’ when interventions to prevent stiff ageing hearts may be most effective.

Effect of healthy aging on left ventricular relaxation and diastolic suction.

Doppler ultrasound measures of left ventricular (LV) active relaxation and diastolic suction are slowed with healthy aging. It is unclear to what extent these changes are related to alterations in intrinsic LV properties and/or cardiovascular loading conditions. Seventy carefully screened individuals (38 female, 32 male) aged 21-77 were recruited into four age groups (young: <35; early middle age: 35-49; late middle age: 50-64 and seniors: ≥65 yr). Pulmonary capillary wedge pressure (PCWP), stroke volume, LV end-diastolic volume, and Doppler measures of LV diastolic filling were collected at multiple loading conditions, including supine baseline, lower body negative pressure to reduce LV filling, and saline infusion to increase LV filling. LV mass, supine PCWP, and heart rate were not affected significantly by aging. Measures of LV relaxation, including isovolumic relaxation time and the time constant of isovolumic pressure decay increased progressively, whereas peak early mitral annular longitudinal velocity decreased with advancing age (P < 0.001). The propagation velocity of early mitral inflow, a noninvasive measure of LV suction, decreased with aging with the greatest reduction in seniors (P < 0.001). Age-related differences in LV relaxation and diastolic suction were not attenuated significantly when PCWP was increased in older subjects or reduced in the younger subjects. There is an early slowing of LV relaxation and diastolic suction beginning in early middle age, with the greatest reduction observed in seniors. Because age-related differences in LV dynamic diastolic filling parameters were not diminished significantly with significant changes in LV loading conditions, a decline in ventricular relaxation is likely responsible for the alterations in LV diastolic filling with senescence.

The Effect of Age-related Differences in Body Size and Composition on Cardiovascular Determinants of VO2max

BACKGROUNDnA reduction in maximal stroke volume (SVmax) and total blood volume (TBV) has been hypothesized to contribute to the decline in maximal oxygen uptake (VO2max) with healthy aging. However, these variables have rarely been collected simultaneously in a board age range to support or refute this hypothesis. It is also unclear to what extent scaling size-related cardiovascular determinants of VO2max affects the interpretation of age-related differences.nnnMETHODSnA retrospective analysis of VO2max, maximal cardiac output (QCmax), TBV, and body composition including fat-free mass (FFM) in 95 (51% M) healthy adults ranging from 19-86 years.nnnRESULTSnAbsolute and indexed VO2max, QCmax, and maximal heart rate decreased in both sexes with age (p ≤ .031). SVmax declined with age when scaled to total body mass or body surface area (p ≤ .047) but not when expressed in absolute levels (p = .120) or relative to FFM (p = .464). Absolute and indexed TBVs (mL/kg; mL/m(2)) were not significantly affected by age but increased with age in both sexes when scaled to FFM (p ≤ .013). A lower arteriovenous oxygen difference (a-vO2diff) contributed to the reduction in VO2max with age in treadmill exercisers (p = .004) but not in the entire cohort (p = .128).nnnCONCLUSIONnThese results suggest (a) a reduction in absolute SVmax, and TBV do not contribute substantially to the age-related reduction in VO2max, which instead results from a smaller QCmax due to a lower maximal heart rate, and (b) body composition scaling methods should be used to accurately describe the effect of aging on physical function and cardiovascular variables.

The effect of exercise training on left ventricular relaxation and diastolic suction at rest and during orthostatic stress after bed rest

•u2002 What is the central question of this study? A smaller upright stroke volume contributes significantly to orthostatic intolerance after bed rest. The role of slowed left ventricular relaxation and diastolic suction on stroke volume during orthostatic stress after bed rest has not been previously reported. It is also unclear whether these changes are influenced by exercise training while in bed. •u2002 What is the main finding and its importance? The reduction in left ventricular mass, volumes and Doppler parameters of relaxation and diastolic suction were greater with sedentary bed rest compared with those of subjects who performed exercise training while in bed. When left ventricular filling pressure was restored to prebed‐rest levels, Doppler parameters were also restored, suggesting that stroke volume after bed rest is more influenced by cardiac remodelling and changes in loading conditions rather than intrinsic ventricular properties.

Effects of pericardial constraint and ventricular interaction on left ventricular hemodynamics in the unloaded heart

Pericardial constraint and ventricular interaction influence left ventricular (LV) performance when preload is high. However, it is unclear if these constraining forces modulate LV filling when the heart is unloaded, such as during upright posture, in humans. Fifty healthy individuals underwent right heart catheterization to measure pulmonary capillary wedge (PCWP) and right atrial pressure (RAP). To evaluate the effects of pericardial constraint on hemodynamics, transmural filling pressure (LVTMP) was defined as PCWP-RAP. Beat-to-beat blood pressure (BP) waveforms were recorded, and stroke volume (SV) was derived from the Modelflow method. After measurements at -30 mmHg lower body negative pressure (LBNP), which approximates the upright position, LBNP was released, and beat-to-beat measurements were performed for 15 heartbeats. At -30 mmHg LBNP, RAP and PCWP were significantly decreased. During the first six beats of LBNP release, heart rate (HR) was unchanged, while BP increased from the fourth beat. RAP increased faster than PCWP resulting in an acute decrease in LVTMP from the fourth beat. A corresponding drop in SV by 3% was observed with no change in pulse pressure. From the 7th to 15th beats, LVTMP and SV increased steadily, followed by a decreased HR due to the baroreflex. A decreased TMP, but not PCWP, caused a transient drop in SV with no changes in HR or pulse pressure during LBNP release. These results suggest that the pericardium constrains LV filling during LBNP release, enough to cause a small but significant drop of SV, even at low cardiac filling pressure in healthy humans.

Heart rate recovery after maximal exercise is blunted in hypertensive seniors

Abnormal heart rate recovery (HRR) after maximal exercise may indicate autonomic dysfunction and is a predictor for cardiovascular mortality. HRR is attenuated with aging and in middle-age hypertensive patients, but it is unknown whether HRR is attenuated in older-age adults with hypertension. This study compared HRR among 16 unmedicated stage 1 hypertensive (HTN) participants [nine men/seven women; 68 ± 5 (SD) yr; awake ambulatory blood pressure (BP) 149 ± 10/87 ± 7 mmHg] and 16 normotensive [control (CON)] participants (nine men/seven women; 67 ± 5 yr; 122 ± 4/72 ± 5 mmHg). HR, BP, oxygen uptake (V̇o2), cardiac output (Qc), and stroke volume (SV) were measured at rest, at two steady-state work rates, and graded exercise to peak during maximal treadmill exercise. During 6 min of seated recovery, the change in HR (ΔHR) was obtained every minute and BP every 2 min. In addition, HRR and R-R interval (RRI) recovery kinetics were analyzed using a monoexponential function, and the indexes (HRRI and RRII) were calculated. Maximum V̇o2, HR, Qc, and SV responses during exercise were not different between groups. ΔHR was significantly different (P < 0.001) between the HTN group (26 ± 8) and the CON group (36 ± 12 beats/min) after 1 min of recovery but less convincing at 2 min (P = 0.055). BP recovery was similar between groups. HRRI was significantly lower (P = 0.016), and there was a trend of lower RRII (P = 0.066) in the HTN group compared with the CON group. These results show that in older-age adults, HRR is attenuated further with the presence of hypertension, which may be attributable to an impairment of autonomic function.