While the heart size maintains a constant proportion to body size, heart function parameters, such as heart rate and cardiac output, show a more complex scaling pattern. How these phenomena affect the long-axis left ventricular (LV) function is unknown. We studied 10 mice, 15 rats, 6 rabbits, 8 mongrel dogs and 38 human volunteers. Doppler tissue echocardiography data were postprocessed to reconstruct mitral annulus ( . β values of the relationship between MA peak systolic velocity and LV end-diastolic volume and mass were 0.096 ± 0.012 and 0.100 ± 0.013, respectively (P < 0.0001 versus 0). Finally, β values of the relationship between the long-to-short axis displacement ratio and LV end-diastolic volume and mass were 0.077 ± 0.017 and 0.086 ± 0.019 (P < 0.0001 versus 0). We conclude that MA velocity, displacement, and long-to-short axis displacement ratio scale allometrically to heart size. This reduces the relative long-axis contribution to heart function in small mammals.

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Objectives:Patients with peripheral artery disease have walking impairment, greater thrombotic risk, and are often treated with exercise training. We sought to determine the effect of a 3-month-long exercise program on clot strength among patients with peripheral artery disease and intermittent claudication.Methods:Twenty-three symptomatic peripheral artery disease patients were randomly assigned to a walking exercise program or to an attention control group who performed light resistance exercise. We investigated the effect of exercise training on clot strength and time to clot formation was assessed by thromboelastography.Results:After 3 months of exercise, clot strength (maximal amplitude) and time to clot formation (R) did not change significantly from baseline, even after improvements in claudication onset time (p < 0.01) and peak walking time (p < 0.05). Furthermore, changes in clot formation parameters were not significantly different between groups. Among the 10 individuals demonstrating a reduction in clot strength (reduced maximal amplitude), one was a smoker (10%) compared to 9 of 13 non-responders (69%) whose maximal amplitude was unchanged or increased (p = 0.0097).Conclusion:In this ancillary study, a 12-week walking program improved ambulatory function in peripheral artery disease patients with claudication, but does not modify clot strength or time to clot formation. Larger studies are needed to confirm these hypothesis generating findings and to determine whether a different amount or type of exercise may induce a change in clotting in this patient population.

Peripheral artery disease (PAD) is associated with exercise impairment and greater thrombotic risk. We investigated if clot formation and platelet aggregation assessed by thromboelastography and light-transmission aggregometry correlate with the severity of symptomatic PAD assessed by ambulatory function measures. We studied 40 symptomatic PAD patients in whom severity of disease was assessed using ankle brachial index, peak walking time, claudication onset time, peak oxygen uptake, daily ambulatory activity and walking impairment questionnaire (WIQ) scores. Clot strength correlated negatively with peak oxygen uptake, peak walking time and WIQ distance and stair-climbing scores. Time to clot formation did not correlate with exercise parameters. Platelet aggregation was negatively correlated with WIQ distance score, and was positively correlated with peak walking time and peak oxygen uptake. In conclusion, clot strength and platelet aggregation correlated with objective and self-perceived ambulatory measures. PAD patients with more severe walking impairment may be likely to form stronger clots.