Central versus peripheral cardiovascular limitation to exercise: the role of two-modality testing

Uncertainty arises when physiological findings indicate a cardiovascular limitation but the limiting constituents within the cardiovascular system cannot be identified.

It was the aim of this study to investigate the value of two-modality exercise testing to assess effort intolerance when the cause remains obscure despite standard exercise testing.

A second modality maximal exercise test to fatigue, using either upper extremity or supine exercise, was performed following a nonconclusive standard sitting ergometry. Six patients (4 males) with a mean age of 56 +/- 22 years with severe exercise intolerance were enrolled in the study.

In 4 of the patients, arm exercise capacity exceeded leg capacity, indicating peripheral limitation. In 1 of these patients, hemoglobin saturation decreased markedly only during sitting exercise while it remained normal during arm exercise, indicating a unique, iatrogenic abnormality. In another patient, supine leg exercise capacity exceeded sitting capacity, indicating peripheral venous limitation, and in an additional patient, leg capacity exceeded arm capacity pointing towards a central abnormality. In all 6 patients, the second modality test highlighted the correct diagnosis.

Arm exercise that is added to a standard leg exercise may distinguish between central circulatory and peripheral vascular lower extremity limitation. Supine posture augments venous return to the heart and is useful when preload may be limiting. These modes of exercise may be added to a standard sitting or upright test in order to differentiate between central cardiovascular versus peripheral vascular (arterial or venous) causes of exercise limitation.