Value of 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) gated SPECT for the detection of silent myocardial ischemia in hemodialysis patients: clinical variables associated with abnormal test results

C-reactive Protein: Repeated Measurements will Improve Dialysis Patient Care

Systemic inflammation is a common feature in the uremic phenotype and associates with poor outcomes. The awareness regarding the importance of inflammation assessment in chronic kidney disease (CKD) patients has risen in recent years, and despite the development of novel biomarkers, C-reactive protein (CRP) is still the most measured inflammatory parameter. Notwithstanding, the possible weak points of CRP determination, this biomarker has demonstrated being useful both for guidance in clinical practice and for risk estimation. In addition, regular determination of CRP among dialysis patients has been associated with better outcomes in different dialysis facilities. Because persistent inflammation may be a silent reflection of various pathophysiologic alterations in CKD, it is crucial that inflammatory markers are regularly monitored and therapeutic attempts be made to target this inflammation.

Association between plasma homocysteine and myocardial SPECT abnormalities in patients referred for suspected myocardial ischaemia

Background

Elevated plasma homocysteine level has emerged as a relatively newly recognised risk factor for coronary artery disease (CAD). However, reduction of plasma homocysteine levels in large prospective studies did not appear to reduce the risk for subsequent cardiac events. In this study, we investigated the association between plasma homocysteine levels and quantitative indices of myocardial perfusion SPECT imaging in patients referred for myocardial ischaemia.

Methods

Quantitative myocardial perfusion SPECT indices were obtained for 120 patients who were recruited for the study. All patients underwent a two-day rest–stress myocardial perfusion imaging. Plasma venous sampling was done on all patients after an overnight fast. Of the 120 participants (mean age 56 years, 53% males), 33% had elevated plasma homocysteine levels. The plasma homocysteine level was then compared to the results of imaging and other known risk factors.

Results

After adjustment for traditional risk factors of coronary artery disease, patients with elevated homocysteine levels had a significantly higher mean summed stress score (SSS) (11.3 vs 6.9, p = 0.02) than patients with a normal homocysteine level. This was true for both single- and multivessel disease. Also, patients with elevated homocysteine levels had a higher stress end-systolic volume (SESV) (137 vs 105 ml, p = 0.03) and lower post-stress left ventricular ejection fraction (SEF) (54 vs 64%, p = 0.02). The patients with elevated plasma homocysteine levels also had a significantly lower mean body mass index (BMI) (26.6 vs 30.6 kg/m², p = 0.002). There was a significant relationship between the total number of known risk factors in a patient with CAD and the proportion of patients presenting with elevated plasma homocysteine levels (p = 0.03). Also, the extent of infarct, as measured by the summed rest score (SRS), was more closely correlated with an elevated homocysteine level than with the degree of ischaemia.

Conclusion

There was a correlation between plasma homocysteine level and the presence and extent of myocardial perfusion abnormalities in patients with established coronary artery disease, in particular those with multiple risk factors and multi-vessel infarction.

Left atrial volume index is a predictor of silent myocardial ischemia in high-risk patients with end-stage renal disease

Silent myocardial ischemia is highly prevalent in patients with end-stage renal disease (ESRD), and is associated with poor cardiovascular outcomes. However, the criteria for coronary artery disease screening remain unclear in asymptomatic patients. The goal of this study was to evaluate whether baseline echocardiographic parameters can predict myocardial ischemia in asymptomatic patients with ESRD. We investigated 259 high-risk asymptomatic patients with ESRD who underwent both echocardiography and myocardial perfusion single-photon emission computed tomography at the initiation of dialysis. We defined the presence of myocardial ischemia as a reversible or fixed perfusion defect. Silent myocardial ischemia was found in 99 (38.2 %) high-risk asymptomatic patients with ESRD at the initiation of dialysis. In patients with myocardial ischemia, left ventricular (LV) end systolic volume index, LV mass index, left atrial volume index (LAVI), and the ratio of early mitral inflow velocity to peak mitral annulus velocity were significantly higher, and LV ejection fraction was significantly lower, than those without myocardial ischemia. Multivariate analysis showed that LAVI, LV ejection fraction, and regional wall motion abnormalities were independently associated with the presence of silent myocardial ischemia. Severe (LA) enlargement was independently associated with the presence of silent myocardial ischemia (odds ratio 1.97; 95 % confidence interval 1.08-3.57; p = 0.026). LA enlargement is a potential marker for identifying patients with ESRD at high risk of silent myocardial ischemia.

Predictors of cardiovascular events in hemodialysis patients after stress myocardial perfusion imaging

Cardiovascular prognosis in patients under normal stress myocardial perfusion images (MPI) is generally excellent. However, this is not true for patients with chronic kidney disease (CKD) treated by hemodialysis. This study evaluated prognostic factors of adverse cardiovascular events in hemodialysis patients in whom stress MPI was performed. Pharmacological stress MPI was performed in 88 hemodialysis patients, and we retrospectively followed-up for 26 months. Cardiovascular events included cardiac death, nonfatal myocardial infarction, and unstable angina. Cardiovascular events occurred in 16 patients (18%). Univariate Cox regression analysis revealed that peripheral artery disease (PAD) and parameters of stress MPI were significant predictors of cardiovascular events. Multivariate Cox regression analysis revealed that only PAD (hazard ratio=6.54; P=0.002), and abnormal stress MPI (hazard ratio=8.26; P=0.008) were independent and significant predictors of cardiovascular events. Kaplan-Meier analysis showed better prognosis in patients with normal stress MPI than in patients with abnormal stress MPI (P<0.001, log-rank test). However, in patients with normal stress MPI, cardiovascular events occurred in 10 of the 76 patients (13%). Among patients with normal stress MPI, Kaplan-Meier analysis showed that patients with no PAD had better prognosis than patients with PAD (P=0.001, log-rank test). In hemodialysis patients, both PAD and stress MPI were powerful cardiovascular predictors. Normal stress MPI alone cannot guarantee good prognosis in terms of cardiovascular events. Consideration of PAD may improve the predictive value of stress MPI in some patients.

Patients with end-stage renal disease: optimal diagnostic and prognostic performance of myocardial gated-SPECT, initial results

PURPOSE

We investigated the role of Tc-99m sestamibi myocardial perfusion gated single photon emission computed tomography (GSPECT) in identifying those patients with end-stage renal disease (ESRD) in whom optimal diagnosis of coronary artery disease and prediction of cardiac events (CEs) could be achieved.

METHODS

This was a prospective study that included 41 asymptomatic ESRD patients who had been undergoing hemodialysis for 12 months or less (22 men and 19 women) with restricted selection criteria (asymptomatic traditional risk). Tc-99m sestamibi GSPECT was carried out for all patients, whereas coronary angiography (Cath) was carried out only for abnormal GSPECT patients, with a 2-year follow-up for CEs. Twenty individuals matched for age, sex, and BMI formed the control group.

RESULTS

Of the 41 ESRD patients, 13 showed abnormal GSPECT [11/13 with myocardial perfusion defects and left ventricular dysfunction in concordance with Cath and 2/13 with only left ventricular dysfunction (i.e. stunning)] compared with 1/20 in the control group. None of the patients with negative results experienced CEs (negative predictive value 100%); these patients had a 2-year CE-free survival rate of 100% compared with 46% for patients with positive results on GSPECT (P<0.0001; seven GSPECT-positive patients developed CEs during their follow-up). Patients with positive results were more frequently male (P<0.001), were significantly older (P=0.01), and had highly sensitive C-reactive protein levels (P=0.002). Abnormal GSPECT was the only independent predictor of CEs (95% confidence interval, 7.1-46.7; hazard ratio, 46.1; P<0.001).

CONCLUSION

GSPECT exhibited optimum performance for coronary artery disease detection and risk stratification in asymptomatic ESRD patients during their first year of regular hemodialysis who were selected according to our modification of the traditional risk category. This may help in selecting suitable candidates for Cath, revascularization, and future renal transplantation.

Cardiac testing for coronary artery disease in potential kidney transplant recipients

BACKGROUND

Patients with chronic kidney disease (CKD) are at increased risk of coronary artery disease (CAD) and adverse cardiac events. Screening for CAD is therefore an important part of preoperative evaluation for kidney transplant candidates. There is significant interest in the role of non-invasive cardiac investigations and their ability to identify patients at high risk of CAD. 

OBJECTIVES

We investigated the accuracy of non-invasive cardiac screening tests compared with coronary angiography to detect CAD in patients who are potential kidney transplant recipients.

SEARCH METHODS

MEDLINE and EMBASE searches (inception to November 2010) were performed to identify studies that assessed the diagnostic accuracy of non-invasive screening tests, using coronary angiography as the reference standard. We also conducted citation tracking via Web of Science and handsearched reference lists of identified primary studies and review articles.  

SELECTION CRITERIA

We included in this review all diagnostic cross sectional, cohort and randomised studies of test accuracy that compared the results of any cardiac test with coronary angiography (the reference standard) relating to patients considered as potential candidates for kidney transplantation or kidney-pancreas transplantation at the time diagnostic tests were performed. 

DATA COLLECTION AND ANALYSIS

We used a hierarchical modelling strategy to produce summary receiver operating characteristic (SROC) curves, and pooled estimates of sensitivity and specificity. Sensitivity analyses to determine test accuracy were performed if only studies that had full verification or applied a threshold of ≥ 70% stenosis on coronary angiography for the diagnosis of significant CAD were included.

MAIN RESULTS

The following screening investigations included in the meta-analysis were: dobutamine stress echocardiography (DSE) (13 studies), myocardial perfusion scintigraphy (MPS) (nine studies), echocardiography (three studies), exercise stress electrocardiography (two studies), resting electrocardiography (three studies), and one study each of electron beam computed tomography (EBCT), exercise ventriculography, carotid intimal media thickness (CIMT) and digital subtraction fluorography (DSF). Sufficient studies were present to allow hierarchical summary receiver operating characteristic (HSROC) analysis for DSE and MPS. When including all available studies, both DSE and MPS had moderate sensitivity and specificity in detecting coronary artery stenosis in patients who are kidney transplant candidates [DSE (13 studies) - pooled sensitivity 0.79 (95% CI 0.67 to 0.88), pooled specificity 0.89 (95% CI 0.81 to 0.94); MPS (nine studies) - pooled sensitivity 0.74 (95% CI 0.54 to 0.87), pooled specificity 0.70 (95% CI 0.51 to 0.84)]. When limiting to studies which defined coronary artery stenosis using a reference threshold of ≥ 70% stenosis on coronary angiography, there was little change in these pooled estimates of accuracy [DSE (9 studies) - pooled sensitivity 0.76 (95% CI 0.60 to 0.87), specificity 0.88 (95% CI 0.78 to 0.94); MPS (7 studies) - pooled sensitivity 0.67 (95% CI 0.48 to 0.82), pooled specificity 0.77 (95% CI 0.61 to 0.88)]. There was evidence that DSE had improved accuracy over MPS (P = 0.02) when all studies were included in the analysis, but this was not significant when we excluded studies which did not avoid partial verification or use a reference standard threshold of ≥70% stenosis (P = 0.09).  

AUTHORS' CONCLUSIONS

DSE may perform better than MPS but additional studies directly comparing these cardiac screening tests are needed. Absence of significant CAD may not necessarily correlate with cardiac-event free survival following transplantation. Further research should focus on assessing the ability of functional tests to predict postoperative outcome.

Should we screen for coronary artery disease in asymptomatic chronic dialysis patients?

The hemodialysis population is characterized by a high prevalence of 'asymptomatic' coronary artery disease (CAD), which should be interpreted differently from asymptomatic disease in the general population. A hemodynamically significant stenosis may not become clinically apparent owing to impaired exercise tolerance and autonomic neuropathy. The continuous presence of silent ischemia may cause heart failure, arrhythmias, and sudden death. Whether revascularization of an asymptomatic dialysis patient improves outcome remains a moot point, although several observational studies and one small RCT suggest a benefit. It can therefore be defended to screen asymptomatic dialysis patients for CAD. A number of noninvasive screening tests are available, but none has proved equally practical and reliable in the dialysis population as in the general population. Myocardial perfusion scintigraphy (MPS) before and after a pharmacological stress such as dipyridamole can reveal both ischemia and myocardial scarring. When compared with coronary angiography, low sensitivities were reported and attributed to impaired vasodilation to dipyridamole in dialysis patients. A more likely explanation is that not every anatomical stenosis will lead to impaired coronary blood flow on MPS. Numerous studies have shown an incremental prognostic value of dipyridamole-MPS over clinical data for prediction of adverse cardiac events, in some studies even over coronary angiography. Pending the availability of high-quality evidence, in our opinion asymptomatic dialysis patients could undergo dipyridamole-MPS, followed by coronary angiography in case of an abnormal scan. This combined physiological and anatomical evaluation of the coronary circulation allows us to determine which coronary stenosis is clinically relevant and therefore should be revascularized.

Factors related to silent myocardial damage in hemodialysis patients

BACKGROUND

Both traditional and non-traditional risk factors play a role for the development of cardiovascular disease in hemodialysis patients. However, a specific relationship between these risk factors and silent myocardial damage is unknown.

METHODS

Demographic, anthropometric, clinical, and laboratory data were collected. Silent myocardial damage was defined by elevated cardiac troponin I values above cutoff values.

RESULTS

In total, 113 hemodialysis patients were included. Cardiac troponin I concentrations were below cutoff value (<2.3 ng/mL) in 103 (91.2%) patients (Group 1), whereas 10 (8.8%) patients had elevated concentrations (Group 2). Group 1 patients had higher levels of hemoglobin (p = 0.002) and high-density lipoprotein cholesterol (p = 0.002) and lower C-reactive protein (p = 0.003) and tumor necrosis factor-alpha (p = 0.005) levels, as well as less incidence of left ventricular hypertrophy (p = 0.045), when compared to Group 2 patients. Diabetes mellitus (Beta = +0.160, p = 0.021), left ventricular hypertrophy (Beta = +0.247, p < 0.0001), uncontrolled blood pressure (Beta = +0.170, p = 0.016), normalized protein equivalent of total nitrogen appearance (Beta = -0.230, p = 0.001), hemoglobin (Beta = -0.302, p < 0.0001), and tumor necrosis factor-alpha (Beta = +0.506, p < 0.0001) were found to be independently associated with cardiac troponin I levels in multiple linear regression analysis.

CONCLUSIONS

Both traditional and non-traditional risk factors are related with silent myocardial damage, which is considered to an antecedent of major cardiovascular events. Hemodialysis patients, even when asymptomatic, must be closely followed up for the presence of these risk factors.

A risk score to predict silent myocardial ischemia in patients with coronary artery disease under aspirin therapy presenting with upper gastrointestinal hemorrhage

BACKGROUND

Silent myocardial ischemia (SMI) is a relatively common complication in patients with coronary artery disease (CAD) under aspirin therapy presenting with upper gastrointestinal hemorrhage (UGIH).

AIM

This study was conducted to develop and prospectively validate a risk prediction score to identify SMI in patients undergoing aspirin therapy for CAD presenting with UGIH in the emergency department (ED).

METHODS

This was a 2-phase noninterventional study. In the derivation phase, adults with CAD under aspirin therapy (100 mg once daily) presenting to the ED with UGIH were retrospectively recruited. By multiple logistic regression analysis, we derived a risk score from 224 patients that predicts the patients' risk of SMI. In the validation phase, we prospectively validated this score using receiver operating characteristic curves with data from 110 patients. We also developed a fast-track screening procedure from this score.

RESULTS

There were 56 patients (25.0%) and 29 patients (26.4%) with SMI in the derivation and validation sets, respectively. Independent multivariate predictors of SMI were age of older than 75 years, severity of CAD, systolic blood pressure of less than 110 mm Hg, diastolic blood pressure of less than 85 mm Hg, hematocrit of less than 30%, and blood urea nitrogen-creatinine ratio of more than 30. The area under receiver operating characteristic curve for the rule was 0.93 in the derivation set and 0.96 in the validation set. At the cutoff value of 5 points or higher, the sensitivity and specificity of the fast-track screening procedure for SMI were 96.6% and 86.4%, respectively. The positive and negative predictive values were 71.8% and 98.6%, respectively.

CONCLUSIONS

This simple risk prediction score is easily calculated and is based on rapidly available clinical and laboratory data in the ED. It can be used to stratify patients undergoing aspirin therapy for CAD presenting with UGIH by risk of SMI.