Product of Heart Rate and First Heart Sound Amplitude as an Index of Myocardial Metabolic Stress During Graded Exercise

Abstract

The threshold or "breakpoint" phenomenon that occurs in AT and DP during a graded exercise test is related to increased plasma catecholamine level. 10-12 The rapid rise in plasma catecholamine level also causes an increase in myocardial oxygen demand (MOD) by increasing both HR and SBP. Furthermore, animal studies have shown that following adrenaline injection, the recorded amplitude of the first heart sound (AHS1) exhibits a similar increase to that of the early systolic wave of the first derivative of left ventricular pressure (LVdP/dtmax), a major determinant of MOD. 1 Several studies have also reported continuous measurement of AHS1 during a graded exercise test. 13-16 Thus, if AHS1 accurately reflects LVdP/dtmax, it may be used in place of SBP for the calculation of DP.he anaerobic threshold (AT), determined by the lactate threshold (LT) or non-invasively from ventilatory responses is widely used for assessing aerobic capacity and optimizing training intensity. 1-4 Tanaka et al showed that the double product (DP; ie, the product of heart rate [HR] and systolic blood pressure [SBP]) increases more steeply above the LT, and has a breakpoint (DPBP) that is associated with the LT. 5 The DPBP occurs at a similar intensity to that of the LT and the AT in healthy subjects as well as patients with coronary artery disease (CAD). 6-8 Further, aerobic exercise training increases oxygen consumption (V O2) at the DPBP similar to the training response to the AT. 9 Thus, DPBP, which is easier to obtain than AT and the LT, appears to be an appropriate surrogate for LT. Background: The double product (DP) breakpoint of heart rate (HR) and systolic blood pressure has been identified as coincident with anaerobic threshold (AT), but there are no simple methods for measuring cardiac metabolic stress (CMS) during an exercise test. It was hypothesized that the DP of HR and the amplitude of the first heart sound (AHS1) (DP-AHS1) would reflect CMS, and thus, the breakpoint in the DP-AHS1 (DPBP-AHS1) could be an alternative method for determining AT.

Estimation of Anaerobic Threshold, a Classical Index Drawing Renewed Attention, by New Methods Without Respiratory Gas Measurements

“…12 They also noted that the breakpoint in DP-AHS1 strongly correlated with the AT and peak V O2 in their subjects. 12 Agostoni et al proposed that a failure to detect AT in heart failure patients is associated with a reduced peak V O2, and that an indeterminable AT itself has an independent prognostic role.…”

“…12 They also noted that the breakpoint in DP-AHS1 strongly correlated with the AT and peak V O2 in their subjects. 12 Agostoni et al proposed that a failure to detect AT in heart failure patients is associated with a reduced peak V O2, and that an indeterminable AT itself has an independent prognostic role. 7 It would be helpful, however, to detect the anaerobic (or lactate) threshold even in patients with severe heart failure, for the purpose of obtaining a valuable CPX index and prescribing optimal exercise intensity for cardiac rehabilitation.…”

Association between cardiorespiratory fitness, physical activity, and cognitive function in Japanese community-dwelling elderly adults

“…For such reasons, the aerobic fitness of elderly people has rarely been measured on a community basis. Heart sounds during an exercise stress test have been reported to approximate the anaerobic threshold (AT) and lactate threshold (LT) 22) . Evaluation of aerobic capacity using heart sounds is noninvasive, inexpensive, and has no special environmental restrictions; this type of evaluation is therefore considered to be appropriate and useful as a measurement method for elderly people in a communitybased investigation.…”

Muscle Weakness Is Associated With an Increase of Left Ventricular Mass Through Excessive Blood Pressure Elevation During Exercise in Patients With Hypertension

“…8) Skeletal muscles are known to accumulate metabolites such as lactic acid during exercise. 9) These metabolites stimulate the rostral ventrolateral medulla, which is the center of the sympathetic system, via metabolite-sensitive receptors in skeletal muscle, thereby enhancing sympathetic activity. 9) Inactive and weak skeletal muscles are reported to enhance sympathetic activity during exercise more than active and powerful muscles, because those muscles release more metabolites.…”

“…9) These metabolites stimulate the rostral ventrolateral medulla, which is the center of the sympathetic system, via metabolite-sensitive receptors in skeletal muscle, thereby enhancing sympathetic activity. 9) Inactive and weak skeletal muscles are reported to enhance sympathetic activity during exercise more than active and powerful muscles, because those muscles release more metabolites. 10,11) Arterial stiffness varies based on autonomic and metabolic conditions during exercise, the change in which is evaluated as functional arterial stiffness.…”