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- Computed tomography
- heart failure
- peripheral vascular disease
- pulmonary arterial hypertension
- venous thromboemboli
Pulmonary arterial hypertension (PAH) causes morbidity and mortality in both paediatric and adult age ranges. It tends to be progressive but its symptoms can respond, in many cases, to drug treatments that have gained clinical acceptance in the past decade. A CT approach to the quantification of peripheral pulmonary arterial pruning in PAH has been reported by Moledina and colleagues1 in this journal (see page 1245). This is considered here in relation to more established methods for monitoring the severity and prognostic implications of PAH.
Although PAH may not initially be associated with noticeable symptoms, it tends to result in shortness of breath and limitation of everyday activities that involve moderate exertion.2 For assessing and monitoring the severity of the condition, the 6 min walk test is widely used.3 4 Limitation of the distance that a patient is able to walk on the flat in 6 min reflects a combination of pathophysiological factors: increased pulmonary vascular resistance and its effect on pulmonary perfusion, elevation of pulmonary arterial and right ventricular pressures and any resultant deterioration in right ventricular contractile function. The diastolic filling and the subsequent contractile function of the left ventricle may then be compromised by both the presence of a dilated, high pressure right ventricle adjacent to it in the pericardial space and by limitation of pulmonary venous return. There is a consequent reduction in cardiac output and its responsiveness to exercise. The 6 min walk test has the advantages of simplicity, inexpensiveness and sensitivity to change, particularly when supervised serially by the same experienced staff. Treadmill cardiopulmonary exercise testing, if necessary modified to be sensitive to changes in relatively modest levels of exercise, is also a safe, objective measure of exercise capacity,5 6 with oxygen uptake and ventilatory efficiency …