The incidence of renal artery stenosis in the patients referred for coronary artery bypass grafting.

Multivessel coronary disease or peripheral arterial disease is the clinical clue to diagnosis of renal artery stenosis (RAS). RAS is considered equivalent to coronary artery disease in terms of cardiovascular risk. In this study, we evaluated the incidence of RAS in the patients who were proposed to undergo coronary artery bypass grafting (CABG). Diagnostic evaluations of coronary arteriography and renal artery angiography were performed during the same procedure; the patients who were proposed for CABG in terms of CAD anatomy and clinical manifestation were enrolled. RAS was evaluated and a diameter stenosis of ≥50% was considered as significant RAS; significant RAS patients were divided into five groups. The five groups of RAS were as follows: (1) unilateral RAS ≥50-70%, (2) unilateral RAS ≥70%, (3) bilateral RAS ≥50-70%, (4) one-renal-artery stenosis ≥50-70%, contralateral RAS ≥70%, and (5) bilateral renal artery stenosis ≥70%. A total of 151 patients were enrolled, and RAS (≥50% stenosis in either or both renal arteries) was identified in 47.02% (71/151) patients. Unilateral RAS ≥50-70% was identified in 16.6% (25/151) patients, unilateral RAS ≥70% in 4.6% (7/151) patients, bilateral RAS ≥50-70% in 7.9% (12/151) patients, one-renal-artery stenosis ≥50-70% and contralateral RAS ≥70% in 7.9% (12/151) patients, and bilateral RAS ≥70% was in 9.9%(15/151) patients. The incidence of RAS was 29.03% (18/62) in patients aged ≤60 years, 60% (36/60) in patients aged >60 and ≤70 years, and 58.62% (17/29) in patients aged >70 years. The incidence of RAS was significantly higher in patients aged >60 - ≤70, and >70 years than patients aged ≤60 years (P = 0.001 and P = 0.007, respectively). There was a trend that the incidence of RAS in patients with hypertension [HTN, 50.40% (64/127)] was higher than those without HTN (29.17%, 7/24), with P = 0.056. The incidence of RAS was 47.02% in patients who were proposed for CABG; bilateral RAS of ≥70% was 9.9%. Older age and HTN were associated with RAS in patients who were referred for CABG. This study indicates that the incidence of RAS was high in the patients referred for CABG, and the renal function should be taken care of.

Introduction

Renal artery stenosis (RAS) usually refers to a disease of the large extra-renal arterial vessels and most frequently is caused by atherosclerotic obstructions. Arterial hypertension (HTN), progressive renal failure, flash pulmonary edema, and multivessel coronary disease are clinical manifestations of RAS requiring intervention and treatment and may be resolved by revascularization therapy. In the past, RAS was underrecognized, underdiagnosed, and undertreated. With improved noninvasive imaging techniques such as magnetic resonance imaging angiography, computed tomography angiography, and high-resolution renal duplex sonography, the diagnosis is currently more frequently established.[1]

Atherosclerosis accounts for approximately 90% of cases with RAS and most commonly involves the origin and the proximal third of the main renal artery. In fact, ostial RAS can be considered as a combined disease of the aorta and the renal artery, rather than an isolated problem of the renal arteries. The prevalence of atherosclerotic RAS increases with age, male gender, and traditional cardiovascular risk factors (HTN, diabetes, smoking, dyslipidemia, in particular aortoiliac occlusive disease).[2] However, the true prevalence of atherosclerotic RAS in unselected patients is unknown. In hypertensive patients population, a significant RAS is observed in less than 5% of the patients,[2] whereas a prevalence of up to 12% has been reported in patients with coronary artery disease undergoing cardiac catheterization[3] and up to 40% in patients with peripheral artery disease (PAD).[4] Undoubtedly, atherosclerotic RAS is a progressive disease, as more than half of the patients exhibit an increasing degree of stenosis within 5 years after diagnosis,[5] and one out of five patients with a critical stenosis suffers renal atrophy and renal failure during this period.[1] This study was done to evaluate the incidence of RAS in the candidates for coronary artery bypass grafting (CABG).

Materials and Methods

From July 2008 to March 2010, diagnostic coronary and renal angiography were performed in patients with proven or suspected coronary artery disease during the same procedure; patients who were considered as candidates for CABG on the basis of CAD anatomy and clinical manifestation were enrolled.

Laboratory test was performed in all patients after admission, including blood and urine routine tests, chest X-ray, electrocardiography (ECG), ultrasonic cardiography (UCG), and ultrasonography for liver and kidney. Dynamic electrocardiography (DCG) and multislice spiral computed tomography (MSCT; GE Inc.) were carried out in some of the patients. Patients were selected for CAG on the basis of symptoms and the results of noninvasive investigations. Written informed consent was obtained from all patients and their family members. The exclusion criteria included severe heart dysfunction, severe cardiac arrhythmia, patients with psychopathic diseases, severe other organ diseases apart from heart diseases, known hemorrhagic diathesis, and serum creatinine ≥ 1.5 mg/dl; patients with ST segment elevation myocardial infarction(STEMI) received primary percutaneous coronary intervention.

CABG was recommended for patients with significant left main coronary disease; patients with diffuse three-vessel disease, especially the patients with abnormal left ventricular function (left ventricular ejection fraction <50%); patients with significant left main coronary artery equivalent CAD (≥70% diameter stenosis of both the proximal left anterior descending and circumflex arteries); patients with two-vessel disease with significant disease in proximal left anterior descending, and either abnormal left ventricular function (left ventricular ejection fraction <50%) or demonstrable ischemia on noninvasive testing. In patients with previous PTCA, CABG was recommended for recurrent stenosis associated with a large area of viable myocardium or high-risk criteria on noninvasive testing. CABG early post-STEMI was recommended if the CAD anatomy was unsuitable for PCI and persistent pain; CABG was proposed if the CAD anatomy was unsuitable for PCI depending on disease severity in patients with UA/NSTEMI.[67]

A catheter was guided to cannulate the renal artery and positioned by the vertebrae and intrarenal arterial digital substraction angiography was performed. RAS was measured manually and was defined as narrowing of the appropriate lumen by ≥50%. Patients were divided into five groups as follows: (1) unilateral RAS ≥50–70%, (2) unilateral RAS ≥70%, (3) bilateral RAS ≥50–70%, (4) one-renal-artery stenosis ≥50–70%, contralateral RAS ≥70%, and (5) bilateral RAS ≥70%.

Statistical analysis was performed using SPSS 11.5. Data were expressed as percentage or mean ± standard deviation (SD). Differences in the incidence of RAS were tested by the Chi-square or Fisher's exact test. A P-value <0.05 was considered significant.

Results

A total of 151 patients were enrolled, and their clinical characteristics are shown in Table 1.

Table 1

Baseline characteristics

Atherosclerotic renovascular stenosis (ARVS, ≥50% stenosis in either or both renal arteries) was identified in 47.02% (71/151) patients, whereas no significant ARVS was identified in 53.0% (80/151) patients. Other disease characteristics are shown in Table 2. RAS involving the ostium of one or both renal arteries was seen in 69% cases (49/71); the main stem stenosis of the unilateral or bilateral renal artery was seen in 26.76% (19/71) patients, and that of the branch in 4.23% (3/71) patients. Focal RAS (concentric RAS) involving at least one vessel was found in 56.34% (40/71) cases; aneurysm was found in 1 case.

Table 2

The incidence of renal artery stenosis in the patients proposed for CABG

The incidence of RAS was 29.03% (18/62) in patients aged ≤60 years, 60% (36/60) in patients aged ≤70 and >60 years, and 58.62% (17/29) in patients aged >70 years. The incidence of RAS was significantly higher in patients aged >60, ≤70, and >70 years than patients aged ≤60 years (P = 0.001 and P = 0.007, respectively). There was a statistically significant difference between the patients with MI [30.67% (23/75)] and without MI [47.37% (36/76)] in the incidence of RAS (P = 0.035). There was a trend that the incidence of RAS in patients with HTN [50.40% (64/127)] was higher than in those without HTN [29.17% (7/24); P = 0.056)]. The incidence of RAS was similar in patients with diabetes [53.71% (29/54)] and without diabetes [43.30% (42/97); P = 0.22]. The incidence of RAS was 60% (18/30) and 43.8% (53/121) in patients with and without cerebral infarction (P = 0.112; Table 3).

Table 3

The risk factors for renal artery stenosis in the patients proposed for CABG

Discussion

In autopsy studies, RAS has been found in 4–50% of patients, with a markedly increased prevalence among individuals who were older than 60 years (16.4% vs. 5.5%). In contrast, significant atherosclerotic renovascular disease (ARVD) has been shown in patients who underwent aortic angiography; RAS has been reported in 38% of patients with aortic aneurysm, 33% in those with aortic occlusive disease, and 39% in those with lower limb occlusive disease.[8]

Most recent studies describe a prevalence of RAS of 14–29% in individuals with coronary artery stenosis and 10% in individuals with normal coronary arteries.[89] Atherosclerotic RAS is one aspect of a multiterritory (systemic) atherosclerotic disease. This concept is supported by the observations that atherosclerotic RAS is identified in approximately 12% of the subjects undergoing coronary angiography[1011] and 26% of the subjects investigated for PAD.[12] Renal ischemia resulting from ARAS has two important sequelae: (1) systemic HTN (frequently requiring multiple antihypertensive agents) placing the individual at considerably increased risk of stroke, MI,[13] and mortality; and (2) renal atrophy and nephron loss (a strong correlation between the degree of ARAS and the risk of renal atrophy, P = 0.009).[14] ARAS is therefore a cause of both HTN and renal insufficiency. The latter is coupled with an increased risk of progression to end-stage renal disease.[13] As a result, ARAS is the underlying disease in 10–40% of the patients entering dialysis programs.[15]

The prevalence of RAS has yet not been evaluated completely; one of the reasons was the lack of noninvasive and valid screening procedures for this purpose. Despite the risks of contrast nephropathy and atheroembolic renal disease, arteriography has been considered to be the gold standard diagnostic test. The prevalence and the severity of RAS in patients who underwent cardiac catheterization and were deemed to be at risk for RAS on clinical or laboratory criteria have also been examined. Patients who exhibited at least one of four predefined selection criteria (severe HTN, unexplained CKD, acute pulmonary edema with HTN, or severe atherosclerosis) underwent diagnostic renal angiography. Renal angiography was diagnostic in 837 patients. Evident ARVD was present in 39% of the population, with 50% RAS in 14.3% and severe stenosis (70%) in 7.3% patients.[16]

ARAS is probably underdiagnosed despite a substantial prevalence in patients with vascular disease.[17] ARAS is commonly found by chance during angiography for other reasons.[18] The frequency of ARAS increased in proportion with the number of stenotic coronary arteries; the incidence of ARAS was 10%, 15.8%, and 18.1% in patients with single-vessel, two-vessel, and three-vessel CHD, respectively. It infers that treatment of vascular risk factors would result in better management of the widespread atherosclerotic disease in this high-risk population.

The role of “screening” renal angiogram during coronary angiography continues to be debated vigorously. Arguments in favor of “drive by” angiography include the following:

RAS is a prevalent comorbid condition in cardiologic practice, because the risk factors for CAD and ARVD are identical. The renal angiogram followed with angioplasty/stent deployment of ostial renal artery lesions can be performed effectively with equipment adapted for coronary interventions.[19]

In patients who undergo cardiac catheterization, RAS is an independent risk factor for mortality, which correlates with the severity of the ARVD.[20]

RAS causes or aggravates HTN and/or interferes with its treatment, which has a negative impact on the primary and secondary prevention of coronary heart disease.[19]

CKD from ischemic renal disease impairs the outcome of coronary artery bypass grafting and percutaneous interventions.[19]

Our study was to examine the incidence of RAS in the patients proposed for CABG and found that the incidence of RAS was very high in this group. The higher incidence was associated with more patients with multivessel coronary disease. Aging, three-vessel coronary disease, and HTN are the powerful predictors of the ARVD.

Several limitations of the study deserve attention. Being a single-center observational study may be a limitation. Most importantly, the number of cases in the study was small. The study only examined the anatomic demonstration of the lesions in the renal arteries, without the functional examination of such lesions. The renal function was not impaired in the all patients; HTN can be targeted to the criteria level safely and effectively with antihypertensive drugs in all patients. Clinical outcomes after CABG are needed to be further studied in these patients. However, the results show the incidence of RAS of the patients proposed for CABG in our real clinical practice.

Conclusion

The incidence of RAS was 47.02% in patients who underwent CABG. Older age and HTN were associated with RAS.