Exercise stress tests for detection and evaluation of pulmonary hypertension

The use of an exercise stress test in the diagnosis or evaluation of pulmonary hypertension rests on the assumption that multipoint mean pulmonary artery pressure (mPpa)–flow (Q) plots are superior to isolated pulmonary vascular resistance determinations for the evaluation of the functional state of the pulmonary circulation. A multipoint mPpa–Q relationship is best described by a linear approximation and, as such, characterized by an extrapolated pressure intercept and by a slope. Both are dependent on the method used to increase flow. The slope is higher and the pressure intercept lower when exercise is used to increase flow, rather than unilateral pulmonary artery balloon occlusion or low-dose dobutamine. This is because of exercise-induced pulmonary vasoconstriction. The steepest slopes, i.e. the highest pressures at a given flow, are obtained by resistive exercise (handgrip) when compared with dynamic exercise (cycling) because of systemic vascular resistance and intrathoracic pressure changes. Since systolic, diastolic, and mean pulmonary artery pressures are tightly correlated and since in experienced hands, systolic pulmonary artery pressures and cardiac output are reliably measured using Doppler echocardiography, mPpa–Q lines can be obtained non-invasively. The exercise stress test for non-invasive diagnosis of pulmonary hypertension may be particularly useful for the detection of early disease and for more accurate quantification of pulmonary vascular changes induced by disease progression and/or therapeutic interventions.