Microalbuminuria and tubular proteinuria as risk predictors of cardiovascular morbidity and mortality in essential hypertension: final results of a prospective long-term study (MARPLE Study)*

Abstract

To evaluate the impact of microalbuminuria (MAU) or tubular proteinuria (TPU) on cardiovascular and cerebrovascular events and all-cause mortality, and to assess whether a normalization of MAU and/or TPU induced by angiotensin-converting enzyme-inhibitor-based antihypertensive treatment with ramipril improves cerebrovascular prognosis in essential hypertensive patients without diabetes mellitus. A prospective, controlled, multicenter study was performed involving 3529 hypertensive participants (average follow-up 42.5 months). Ramipril was the basic antihypertensive medication. Proteinuria analysis (albumin, alpha 1-microglobulin, SDS electrophoresis) was performed by quantitative measurement every year. Ambulatory blood pressure monitoring was performed once yearly. The main outcome determined was cardiovascular and cerebrovascular events and all-cause mortality. In patients with TPU and/or MAU, the risk for endpoints increased significantly compared with normal (TPU, 30.0%; MAU, 54.7%; MAU + TPU, 64.0%; macroproteinuria, 74.4%). A change of protein excretion either from pathologic to normal or from normal to pathologic showed a clear trend to correlate with cerebrovascular endpoints (P = 0.056 and P = 0.055). Normal protein excretion at baseline and during follow-up indicated a significantly better prognosis than pathologic proteinuria at baseline and during follow-up. (P < 0.0001). TPU normalized in 31.9%, MAU in 30.6%, MAU + TPU in 29.3%, and macroproteinuria in 10.2% of patients. A total of 445 (25.4%) patients with normal protein excretion developed pathologic proteinuria during follow-up. In non-diabetic hypertensive patients, MAU as well as TPU increases the incidence of cardiovascular events. Normalization of MAU, TPU or macroproteinuria during angiotensin-converting enzyme-inhibitor-based treatment correlates with a reduction of cardiovascular events. Beyond blood pressure control, normalization of MAU and TPU should be considered as a further therapeutic goal. There is a need for further studies to optimize treatment if proteinuria is unresponsive to angiotensin-converting enzyme inhibitors.