ORIGINAL ARTICLE
Print ISSN 1738-5520 / On-line ISSN 1738-5555
Copyright ⓒ 2008 The Korean Society of Cardiology
Korean Circ J 2008;38:301-304
The Estimated Glomerular Filtration Rate With Using
the Mayo Clinic Quadratic Equation as a New Predictor
for Developing Contrast Induced Nephropathy
in Patients With Angina Pectoris
Ung Kim, MD, Young-Jo Kim, MD, Won-Jae Lee, MD, Sang-Hee Lee, MD,
Geu-Ru Hong, MD, Jong-Seon Park, MD, Dong-Gu Shin, MD and Bong-Sup Shim, MD
Cardiology Division, Department of Internal Medicine, Yeungnam University Medical Center, Daegu, Korea
ABSTRACT
Background and Objectives: The Mayo clinic quadratic (MCQ) glomerular filtration rate (GFR) equation accurately estimates the GFR when the presence of kidney disease is unknown. The aim of this study is to evaluate
the usefulness of the MCQ GFR equation for predicting contrast-induced nephropathy (CIN) in patients with
angina pectoris and who are undergoing coronary angiography (CAG) or percutaneous coronary intervention
(PCI). Subjects and Methods: One hundred seven patients diagnosed with stable or unstable angina and who
had normal serum creatinine levels (SCr <1.5 mg/dL) were enrolled. The MCQ GFRs, corresponding to before
and 48 hours post CAG and/or PCI were calculated using the SCr as a previously described protocol. CIN was
defined as a 25% elevation in the SCr or an absolute increase of 0.5 mg/dL (44 μmol/L). Results: Overall, CIN
occurred in 14 (13.1%) patients. CIN developed in 4 (57.1%) patients who had an estimated MCQ GFR less
than 60 mL/min/1.73 m2 and in 10 (10%) patients who had a GFR over 60 mL/min/1.73 m2 (p=0.005). On
univariate analysis, CIN was associated with the baseline MCQ GFR (p=0.001), the C-reactive protein (CRP)
level (p=0.001), the volume of contrast agent (p=0.005), the left ventricular ejection fraction (p=0.001) and the
low density lipoprotein cholesterol level (p=0.030). On multivariate analysis, a baseline MCQ GFR ≤60 mL/min/
1.73 m2 [odds ratio (OR)=2.0, p=0.001], the volume of contrast agent ≥250 mL (OR 17.1, p=0.002), a CRP
level ≥0.5 mg/dL (OR 4.7, p=0.037) and a left ventricular ejection fraction ≤40% (OR 1.7, p=0.020) were the
independent risk factors for CIN. Conclusion: The pre-coronary angiography MCQ GFR is a useful predictor
for the development of CIN. Strong preventive strategies are needed to avoid developing CIN in these high-risk
patients. (Korean Circ J 2008;38:301-304)
KEY WORDS: Glomerular filtration rate; Contrast media; Coronary angiography.
cause of hospital-acquired acute renal failure, accounting for 12% of such cases.1-3) Thus, it is very important
to estimate the renal function before procedures to avoid
CIN. The Mayo clinic quadratic (MCQ) glomerular filtration rate (GFR) equation accurately estimates the GFR
when the presence of kidney disease is unknown.4) The
aim of this study is to evaluate the usefulness of the MCQ
GFR equation for predicting CIN in patients with angina pectoris and who are undergoing coronary angiography (CAG) and/or percutaneous coronary intervention (PCI).
Introduction
Contrast-induced nephropathy (CIN) is a recognized
complication of coronary diagnostic and interventional
procedures that require parenteral administration of
contrast. The development of CIN has been associated
with increased in-hospital morbidity, long-term morbidity and mortality, prolonged hospitalization and
long-term renal impairment. CIN is the third leading
Received: February 14, 2008
Revision Received: March 6, 2008
Accepted: March 27, 2008
Correspondence: Young-Jo Kim, MD, Cardiology Division, Department of
Internal Medicine, Yeungnam University Medical Center, 317-1 Daemyeong-dong, Nam-gu, Daegu 705-717, Korea
Tel: 82-53-620-3313, Fax: 82-53-621-3310
E-mail: [email protected]
Subjects and Methods
Study population
Between December, 2006 and July, 2007, 107 con301
302·Estimated GFR in Contrast Induced Nephropathy
secutive patients who were diagnosed with stable or unstable angina and they had a normal serum creatinine
level (SCr <1.5 mg/dL) were enrolled in this study. The
patients with acute myocardial infarction and/or cardiogenic shock were excluded. CIN was defined as an
absolute increase in the serum creatinine concentration >0.5 mg/dL (>44 μmol/L) or the serum creatinine level was 25% above the baseline within 48 hours
after contrast administration.5-9)
Procedures and sample collection
All the patients underwent CAG and/or PCI by standard techniques. After informed consent was obtained,
all the procedures were done at the operator’s discretion.
The same contrast agent (Iobitridol, Xenetix®, 35 g iodine/100 mL) was used during all the procedures. Before and 48 hours after CAG and/or PCI, blood samples
were drawn and the levels of the following chemical
markers were assessed; blood urea nitrogen (BUN), SCr,
Hemoglobin (Hb), C-reactive protein (CRP), creatine
kinase MB (CK-MB) and the total cholesterol (TC) and
low density lipoprotein cholesterol (LDL-C) levels.
The post-procedure chemical values, including those
for SCr, were measured at 48 hours in all the patients,
and the estimated glomerular filtration rate (e-GFR)
using the MCQ equation and the SCr acquired from
the data were determined and compared. The MCQ
equation was used as previously described [MCQ=exp
{1.911+5.249/SCr-2.114/SCr2-0.00686*age (years)-0.205
(if female)} ].4)10)
Statistical analysis
The continuous data are expressed as means±SDs
and the categorical variables are expressed as frequencies. Continuous variables were assessed using Student’s
t-test. Categorical variables were compared with Chisquare statistics. A p<0.05 was considered significant.
A multivariate logistic regression model was applied,
and it included all the potential confounding variables.
The analyses were conducted using SPSS 13.0 for Windows (Chicago, Illinois, USA).
nificantly higher levels of LDL-C, CRP and a lower left
ventricular ejection fraction (LVEF). In addition, Group
1 received a higher volume of the contrast agent during
PCI than Group 2 (Table 1).
Comparison of laboratory variables and
the estimated glomerular filtration rate
Although the mean BUN level in Group 1 was higher
pre-PCI, the SCr was not different between the groups.
After PCI, both values were increased. The e-GFR, as
calculated with using the MCQ equation, was lower in
Group 1 than in Group 2 before PCI, and after PCI, the
e-GFR was decreased more in Group 1 than in Group 2
(Fig. 1) (Table 2). The CK-MB values were not significantly different after PCI. CIN developed in 10 patients (10%) with an eGFR >60 mL/min/1.73 m2 (100
patients) but CIN developed in 4 patients (57.1%) who
had an GFR ≤60 mL/min/1.73 m2 (a total of 7 patients had an GFR ≤60 mL/min/1.73 m2) (Fig. 2).
Independent risk factors for contrast induced
nephropathy on multivariate analysis
On the univariate analysis, CIN was associated with
the baseline MCQ GFR (p=0.001), the CRP level (p=
0.001), the volume of contrast agent (p=0.005), the left
Table 1. Baseline characteristics of the two groups
Age (yrs)
Group 1
(n=14)
65±8
Group 2
(n=93)
64±9
0.592
Male (%)
7 (50).1
52 (55.9)
0.776
63±10
0.565
p
Body weight (kg)
61.8±11
Height (cm)
161±11
162±8
0.742
AC (cm)
90.9±10
90.1±10
0.786
Body mass index
23.5±2.8
24.1±2.9
0.393
Diabetes mellitus (%)
5 (35.7)
32 (34.4)
1.000
Hypertension (%)
5 (35.7)
50 (53.8)
0.258
Previous history (%)
0
06 (6.6)0
0.280
MI
CVA
3 (21.4)
08 (8.8)0
0.153
PCI
1 (7.1)0
10 (11).0
0.350
CABG
1 (7.1)0
0
0.177
Results
Diagnosis (%)
Stable
9 (64).0
The Incidence of contrast induced nephropathy
and the baseline characteristics
Of the total 107 patients, 14 patients (13.1%) developed CIN. Groups 1 (n=14) and 2 (n=93) were defined as patients who either developed or didn’t develop
CIN, respectively, at 48 hrs after PCI. The proportions
of patient baseline characteristics such as age, sex, body
weight, height, abdominal circumferences, diabetes mellitus and hypertension were not different significantly
between the groups. Also, previous history between two
groups was not significantly different. Group 1 had sig-
Unstable
5 (36).1
30 (33).0
13.2±1.6
13.3±1.3
0.916
187.4±37
180±37
0.979
Hemoglobin (mg/dL)
TC (mg/dL)
LDL-C (mg/dL)
CRP (mg/dL)
LVEF (%)
0.694
63 (67).0
129±28
109±32
0.026
0.93±0.92
0.24±0.22
0.001
53±12
61±10
0.005
Contrast amount (mL)
254±103
182±88
0.007
AC: abdominal circumference, CVA: cerebrovascular accident, MI:
myocardial infarction, PCI: percutaneous coronary intervention,
CABG: coronary artery bypass graft, TC: total cholesterol, LDL-C:
low density lipoprotein cholesterol, CRP: C-reactive protein, LVEF:
left ventricular ejection fraction
Ung Kim, et al.·303
e-GFR mL/min/1.73 m2
100
Pre-PCI
80
Post-PCI
92.1
Table 3. The univariate analysis data and the independent risk
factors for CIN on multivariate analysis
86
On univariate analysis
74.9
p=0.027
57.7
60
40
p=0.001
20
p=0.850
CIN (+)
CIN (-)
Fig. 1. Differences between the groups for the e-GFR as calculated by using the MCQ equation. The mean e-GFR of Group 1,
which corresponded to the patient who developed CIN, was significantly lower after PCI as compared to that of Group 2, which
corresponded to patients who did not. e-GFR: estimated glomerular filtration rate, MCQ: Mayo clinic quadratic, CIN: contrastinduced nephropathy, PCl: percutaneous coronary intervention.
Group 1
(n=14)
Group 2
(n=93)
p
Pre-PCI
22.2±11.2
16.0±5.3
0.001
Post-PCI
25.0±17.4
16.6±6.9
0.001
Pre-PCI
1.3±0.7
0.98±0.64
0.096
Post-PCI
1.9±1.1
0.91±0.26
0.001
1.1±0.4
0.8±0.5
0.156
Blood urea nitrogen (mg/dL)
Creatinine (mg/dL)
CK-MB (mg/dL)
Post-PCI
0.8±0.5
1.2±0.8
0.373
Pre-PCI: pre percutaneous coronary intervention, CK-MB: creatine kinase MB, Post-PCI: post percutaneous coronary intervention
p=0.005
CIN 10 (10%)
0.001
0.005
Low-density lipoprotein cholesterol level
0.030
0.001
Significance
OR
LVEF ≤40%
0.020
1.7
Baseline e-GFR ≤60 mL/min/1.73 m2
CRP ≥0.5 mg/dL
0.001
2.0
0.037
4.7
Contrast agent volume ≥250 mL
0.002
17.1
CIN: contrast-induced nephropathy, e-GFR: estimated glomerular
filtration rate using the Mayo clinic quadratic equation, CRP: Creactive protein, LVEF: left ventricular ejection fraction, OR: odds
ratio
Discussion
Table 2. Laboratory variables of the two groups
MCQ GFR >60
(n=100)
0.001
Contrast agent volume ≥250 mL
LVEF ≤40%
On multivariate analysis
0
Pre-PCI
p
Baseline e-GFR ≤60 mL/min/1.73 m2
CRP level
CIN 4 (57.1%)
MCQ GFR ≤60
(n=7)
Fig. 2. Development of CIN according to the e-GFR level 60
2
2
mL/min/1.73 m . The e-GFR level ≤60 mL/min/1.73 m is associated with a higher rate of developing CIN. CIN: contrast induced nephropathy, e-GFR: estimated glomerular filtration rate,
MCQ: Mayo clinic quadratic.
ventricular ejection fraction (p=0.001) and the LDL-C
level (p=0.030).
On multivariate analysis, the following variables remained the significant independent risk factors for
CIN: an LVEF ≤40% [odds ratio (OR) 1.7, p=0.020],
CRP ≥0.5 mg/dL (OR 4.7, p=0.037), a volume of
contrast agent ≥250 mL (OR 17.1, p=0.002) and the
baseline e-GFR using the MCQ equation ≤60 mL/
min/1.73 m2 (OR 2.0, p=0.001) (Table 3).
CIN is associated with significant economic and clinical consequences, including prolonged hospitalization,
the requirement for dialysis and an increased risk of
death.11)
The known risk factors for CIN after PCI include the
use of an intraaortic balloon pump, an age >75, diabetes,
heart failure, a history of pulmonary edema, the volume
of contrast medium, a SCr level >1.5 mg/dL and an
estimated GFR <60 mL/min/1.73 m2.2)12) In addition,
the risk is increased in a situation of a deficiency of
effective body fluid. The mechanism of CIN is due to
the change of the renal hemodynamics and direct injury
of the epithelial cell of the renal tubules,13)14) and it is
closely associated with reactive oxygen species, as determined via animal experiments.
In 2002, the National Kidney Foundation (NKF) proposed a uniform system to classify patients with chronic
kidney disease (CKD) based on the estimated GFR.15)
The NKF recommended to use the Cockcroft and Gault formula (CG)16) and modification of diet in the
renal disease (MDRD)17) formulas.
However, although the equations have been established and validated for patients with renal insufficiency,4)10) there are drawbacks to the use of these equations; CG overestimates the GFR and MDRD underestimates a high GFR. These limitations recently led to
developing a new MCQ equation that is based on the
results from both healthy subjects and CKD subjects.10)
The incidence of CIN development in this study was
13.1%, which was similar to the previous study. This is
the first study to show the usefulness of e-GFR with using the MCQ equation for predicting CIN in Koreans.
Our study demonstrated that CIN is a frequent complication after CAG and/or PCI, the e-GFR calculated
using the MCQ equation is an independent risk factor
304·Estimated GFR in Contrast Induced Nephropathy
of CIN and an e-GFR <60 mL/min/1.73 m2 is associated with a higher rate of CIN. The calculation of eGFR using this method can be beneficial for predicting clinical events, and the independent CIN risk factors
are a LVEF ≤40%, a CRP level ≥0.5 mg/dL, a volume
of contrast agent ≥250 mL and a baseline e-GFR ≤60
mL/min/1.73 m2. Of course, the amount of contrast
used for procedures was most important for predicting
CIN in this study, so better efforts for reducing the
amount of dye used during the procedure are needed.
Other than this important factor, the patients’ independent risk factors, like the factors found in this study,
may require preventive strategies such as intravenous
saline therapy, low osmolar contrast medium and intravenous sodium bicarbonate and N-acetylcysteine.11)12)18)
Our study has some limitations. First, it included a
small population that was admitted to a single center.
Second, there was no direct comparison with the results
associated with the use of the MDRD equation, which
is a limitation that precluded determining which method
is superior (this limitation is rendered less relevant by
the mentioned drawbacks of the MDRD equation estimations).
In conclusion, pre-coronary angiographic MCQ GFR
is a useful predictor for developing CIN. Strong preventive strategies are needed to avoid developing CIN
in the high risk patients.
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