Proteinuria versus albuminuria in 24-hour urine collection: prevalence and clinical outcome in non-hypoxemic adult patients with congenital heart disease.

Congenital heart disease (CHD) patients, especially cyanotic ones, usually have renal function impairment. However, little information exists in non-cyanotic CHD patients. The objective of this study is to determine renal failure in non-hypoxemic CHD patients by measuring the amount of protein and albumin released in urine over a 24-hour period and determining the glomerular filtration rate (GFR). Prospective study of consecutive outpatient non-hypoxemic CHD patients followed up in a single tertiary referral hospital. Demographic, clinical, blood test and 24-hour urine collection were recorded. 264 CHD patients, 22 (18-343) years old and 160 (61%) males, were followed up during 9.2 (5.9-11.1) years. 137 (52%), 96 (36%) and 31 (18%) CHD patients had mild, moderate, and great anatomical CHD defects. 44 (17%) and 32 (12%) CHD patients showed proteinuria (≥ 150 mg/24 hours) and albuminuria (> 30 mg/24 hours) respectively. 35 out of 44 (79%) CHD patients with proteinuria (≥ 150 mg/24 hours) showed normal to mild albuminuria levels (< 30 mg/24 hours). Variables associated with proteinuria were male sex, body mass index, auricular fibrillation/flutter, arterial hypertension, diabetes mellitus and being under angiotensin-converting enzyme (ACE) inhibitor and an angiotensin receptor blocker (ARB), loop diuretics or anti-aldosterone treatment. Major adverse cardiovascular events (MACE), defined as cardiovascular and non-cardiovascular deaths, stroke, myocardial infarction and heart failure requiring hospitalization, occurred in 16 (6%) patients during the follow up time. Multivariate Cox regression analysis showed that older patients, patients with a great CHD complexity and patients with proteinuria [6.99 (1.90-24.74), P=0.003] had a significant higher risk of MACE. Proteinuria is frequent among non-hypoxemic CHD patients and occurs mostly in those with a GFR above 60 ml/min/1.73 m and normal to mild albuminuria levels. Having proteinuria, but not albuminuria, was independently associated with a worse outcome.