Safety and potential benefits of low dose diamorphine during exercise in patients with chronic heart failure.

Despite major advances in the past two decades in drugs to improve the prognosis of patients with chronic heart failure (CHF), the quality of life of these patients is still quite poor. Patients with congestive heart failure are limited by exertional dyspnoea, which persists even after resolution of pulmonary oedema. The origin of the dyspnoea is complex. Among the many potential explanations proffered, a major unexplained manifestation is the exaggerated ventilatory response to exercise, characterised by a steeper slope relating minute ventilation (VE) to carbon dioxide production—the VE–V~CO2 regression slope. Diamorphine and morphine have been used as standard treatment to alleviate the distressing symptoms of dyspnoea in patients presenting with acute left ventricular failure. The haemodynamic and other effects of diamorphine and morphine are relatively well known in this condition. 3 It is unclear whether the respiratory depressant effects of diamorphine are detrimental or beneficial to patients with CHF, especially during exercise. We have therefore conducted an exploratory prospective randomised, double blind, placebo controlled trial to test the hypotheses that low dose diamorphine is safe and improves the ventilatory responses to exercise, thereby enhancing the aerobic exercise capacity of patients with CHF.