The dynamic relationship between "spontaneous" fluctuations in arterial blood pressure (BP) and heart rate (HR) is increasingly being used to provide an estimate of resting cardiac baroreflex sensitivity. Given the ease of use and clinical utility, spontaneous methods are now also being used to examine cardiac baroreflex sensitivity in distinct subject groups during various laboratory stressors and tasks encountered during daily life, such as physical activity. However, the utility of such spontaneous measures to estimate cardiac baroreflex function during exercise remains unclear, particularly when comparing groups. Therefore, we tested the ability of spontaneous indices to detect age-related differences in cardiac baroreflex function during dynamic exercise. Beat-to-beat HR and BP were measured in eighteen young (24±1 yr) and sixteen older (59±1 yr) healthy middle-aged subjects at rest and during steady-state leg cycling. Estimates of spontaneous cardiac baroreflex sensitivity using the sequence technique (G SEQ ) and low frequency transfer function gain (G TF ) were compared to the operating point (G OP ) and maximal gain (G MAX ) of the full carotid-cardiac baroreflex function curve. At rest G SEQ , G TF , G OP and G MAX were all significantly lower in older subjects. During moderate intensity steady-state exercise no differences were observed in G SEQ and G TF (0.26±0.03 older vs. 0.32±0.04 younger bpm/mmHg; P>0.05), whereas G OP and G MAX (−0.21±0.02 older vs. −0.39±0.03 younger bpm/mmHg; P<0.05) remained lower in older subjects. These data indicate that spontaneous measures of cardiac baroreflex sensitivity alone provide limited information when comparing age-groups during exercise making actual differences in baroreflex function difficult to identify.
Apical ballooning syndrome (ABS) is increasingly diagnosed in critical care settings. Widespread application of echocardiography and cardiac enzyme testing has increased its recognition. Our experience of 4 subjects illustrates the association of ABS with a wide spectrum of acute pulmonary disorders seen in critical care settings. All had ABS proven by normal coronary angiogram and subsequent normalization of left ventricular dysfunction. Bronchospasm due to chronic obstructive pulmonary disease exacerbation or cardiac failure warrants the use of beta agonists. ABS, on the other hand, being caused by excess sympathetic activity could potentially improve with beta blockade. Coexistence of ABS and pulmonary disease in critical-care settings presents unique therapeutic challenges and outcomes can be optimized by judicious use of available medical options.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.