Chapter 99

Patients with cardiovascular disease (CVD) have a high prevalence of chronic kidney disease (CKD), and information about patient kidney function should be included in clinical decision making to arrive at realistic assessments of CVD risk, to reduce the risk of acute kidney injury (AKI) associated with diagnostic and therapeutic interventions, and to adjust medications to account for altered renal pharmacokinetics. Conversely, patients with CKD are at increased risk of both common cardiovascular diseases, including hypertension, coronary artery disease, heart failure, peripheral vascular disease, arrhythmias, and sudden death, and for less common heart diseases, including pericarditis and catheter-related endocarditis.

There is extensive evidence that impaired kidney function is under-detected among the general population, hospitalized patients, high-risk patients, and patients with CVD under medical care.1-4 Cardiology patients are particularly at risk from unrecognized kidney disease because of the extraordinarily high prevalence of impaired kidney function among these patients. The reasons for the low levels of detection and awareness of CKD among clinical populations are unclear, but, as will be discussed later, increase the risk of avoidable errors in clinical decision making and management of patients with CVD.

### Chronic Kidney Disease

CKD is defined by the persistence for ≥3 months of structural and/or functional abnormalities of the kidney.5 The time component of the definition accounts for nonsustained AKI; temporary physiologic abnormalities associated with medications, changes in volume status, or cardiac function; and for laboratory variation and error.

Structural abnormalities that define CKD include albuminuria, abnormal urinary sediment, and positive renal imaging tests. There is near universal agreement that urinary albumin excretion is the preferred screening test for CKD and is best measured by a calculated albumin-to-creatinine ratio (ACR) from a first voided urine specimen.6 Microalbuminuria is defined as an ACR of 30 to 300 mg/g, and anything above this level is macroalbuminuria.

The relationship between serum creatinine (Scr) and the glomerular filtration rate (GFR) is nonlinear, and substantial differences in GFR may be observed for the same Scr among individuals of differing sex, age and race. This often misleads clinicians about the presence and extent of impaired kidney function. Table 99–1 illustrates that the same Scr levels are associated with clinically important differences in levels of kidney function.7 This table underscores the importance of routine reporting by the laboratory of creatinine-based, multivariable equation estimate of GFR or, particularly for the purpose of renal drug dosing, the Cockcroft-Gault equation.8

Table 99–1. Serum Creatinine Levels Can Be Misleading Regarding the Degree of Impaired Kidney Function

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