Respiratory muscle weakness and inefficient ventilation in heart failure due to light-chain amyloidosis

Background. Cardiac involvement in light-chain amyloidosis (AL) frequently results in heart failure with dyspnoea. In heart failure due to ischemic or idiopathic etiology, respiratory muscle dysfunction and ventilatory inefficiency contribute to symptoms and are independent prognostic predictors. However, in patients with AL, respiratory muscle function has not been elucidated. Methods. In 46 consecutive male patients with AL, lung function, maximal inspiratory (Pi(max)) and expiratory (Pe(max)) mouth occlusion pressures, cardiopulmonary exercise testing, echocardiography, and cardiac biomarkers were prospectively studied. Results. Pi(max) and Pe(max) were reduced, P-0.1 did not differ between controls and AL. Pi(max) and Pe(max) were reduced in AL with congestive heart failure compared with asymptomatic patients (median (range) 5.4 (2.3-12.4) kPa vs 10.4 (6.5-14.0) kPa; p<0.05). Respiratory muscle weakness occurred in systolic and diastolic LV dysfunction. Pi(max) was associated with peak exercise oxygen uptake, respiratory inefficiency, wall thickness, and N-terminal pro-brain natriuretic peptide. Conclusions. Respiratory muscle dysfunction and ventilatory inefficiency correlates well with intraventricular septum thickness and peak oxygen uptake and are present even in patients with diastolic dysfunction. Respiratory muscle dysfunction might contribute to dyspnea and exercise limitation and appears to represent a marker of cardiac impairment even in diastolic heart failure. Further studies of Pi(max) as a potential non-invasive prognostic marker are needed.