Platelet function testing to predict hyporesponsiveness to clopidogrel in patients with chest pain seen in the emergency department.

BACKGROUND: A dual antiplatelet regimen has been shown to reduce the risk of major adverse cardiovascular events after percutaneous coronary intervention. However, there is little information available on inhibition of platelet aggregation in patients with a prior coronary stent presenting with chest pain. This study evaluated the prevalence of hyporesponsiveness to clopidogrel and factors associated with this in patients presenting to our emergency department with chest pain who had previously undergone coronary stent placement and were prescribed dual antiplatelet therapy. METHODS: Responsiveness to clopidogrel was evaluated in a cohort of 533 consecutive stented patients presenting to the emergency department with chest pain. P2Y12 reaction units (PRU) and percent P2Y12 inhibition with clopidogrel were measured in all patients. Of 533 patients, 221 (41.6%) had PRU ≥ 230. A multivariate logistic regression model was used to determine the relationship between hyporesponsiveness to clopidogrel (defined as PRU ≥ 230) and several potential risk factors, ie, gender, age, race, type 1 or type 2 diabetes, hypertension, smoking, chronic renal failure, and obesity. RESULTS: There was a greater risk of hyporesponsiveness in African Americans than in non-African American patients (adjusted odds ratio [OR] = 2.165), in patients with type 2 diabetes than in those without (adjusted OR = 2.109), and in women than in men (adjusted OR = 1.813), as well as a greater risk of hyporesponsiveness with increasing age (adjusted OR = 1.167 per decade). CONCLUSION: There was a high prevalence of hyporesponsiveness to clopidogrel in patients presenting with chest pain and a prior coronary stent. Non-insulin-dependent diabetes mellitus and African American race were the strongest predictors of hyporesponsiveness to clopidogrel, followed by gender and age.

Evolving role of platelet function testing in coronary artery interventions.

The substantial reduction in ischemic events provided by the dual antiplatelet regimen with aspirin and clopidogrel is well documented in patients with acute coronary syndrome and patients undergoing percutaneous coronary intervention. Recently the variable response to the antiplatelet agents has received considerable attention after several "boxed warnings" on clopidogrel. This led to intense controversy on pharmacokinetic, pharmacodynamic, and pharmacogenomic issues of antiplatelet drugs, especially clopidogrel. Research use of platelet function testing has been successfully validated in identifying new antiplatelet drugs like prasugrel and ticagrelor. These platelet function assays are no longer regarded just as a laboratory phenomenon but rather as tools that have been shown to predict mortality in several clinical trials. It is believed that suboptimal response to an antiplatelet regimen (pharmacodynamic effect) may be associated with cardiovascular, cerebrovascular, and peripheral arterial events. There has been intense controversy about this variable response of antiplatelet drugs and the role of platelet function testing to guide antiplatelet therapy. While the importance of routine platelet function testing may be uncertain, it may be useful in high-risk patients such as those with diabetes mellitus, diffuse three vessels coronary artery disease, left main stenosis, diffuse atherosclerotic disease, and those with chronic renal failure undergoing percutaneous coronary intervention. It could also be useful in patients with suspected pharmacodynamic interaction with other drugs to assure the adequacy of platelet inhibition. While we wait for definitive trials, a predictive prognostic algorithm is necessary to individualize antiplatelet therapy with P2Y12 inhibitors based on platelet function assays and genetic testing.

Understanding the application of stem cell therapy in cardiovascular diseases.

Throughout their lifetime, an individual may sustain many injuries and recover spontaneously over a period of time, without even realizing the injury in the first place. Wound healing occurs due to a proliferation of stem cells capable of restoring the injured tissue. The ability of adult stem cells to repair tissue is dependent upon the intrinsic ability of tissues to proliferate. The amazing capacity of embryonic stem cells to give rise to virtually any type of tissue has intensified the search for similar cell lineage in adults to treat various diseases including cardiovascular diseases. The ability to convert adult stem cells into pluripotent cells that resemble embryonic cells, and to transplant those in the desired organ for regenerative therapy is very attractive, and may offer the possibility of treating harmful disease-causing mutations. The race is on to find the best cells for treatment of cardiovascular disease. There is a need for the ideal stem cell, delivery strategies, myocardial retention, and time of administration in the ideal patient population. There are multiple modes of stem cell delivery to the heart with different cell retention rates that vary depending upon method and site of injection, such as intra coronary, intramyocardial or via coronary sinus. While there are crucial issues such as retention of stem cells, microvascular plugging, biodistribution, homing to myocardium, and various proapoptotic factors in the ischemic myocardium, the regenerative potential of stem cells offers an enormous impact on clinical applications in the management of cardiovascular diseases.

Cardiac risk stratification: role of the coronary calcium score.

Coronary artery calcium (CAC) is an integral part of atherosclerotic coronary heart disease (CHD). CHD is the leading cause of death in industrialized nations and there is a constant effort to develop preventative strategies. The emphasis is on risk stratification and primary risk prevention in asymptomatic patients to decrease cardiovascular mortality and morbidity. The Framingham Risk Score predicts CHD events only moderately well where family history is not included as a risk factor. There has been an exploration for new tests for better risk stratification and risk factor modification. While the Framingham Risk Score, European Systematic Coronary Risk Evaluation Project, and European Prospective Cardiovascular Munster study remain excellent tools for risk factor modification, the CAC score may have additional benefit in risk assessment. There have been several studies supporting the role of CAC score for prediction of myocardial infarction and cardiovascular mortality. It has been shown to have great scope in risk stratification of asymptomatic patients in the emergency room. Additionally, it may help in assessment of progression or regression of coronary artery disease. Furthermore, the CAC score may help differentiate ischemic from nonischemic cardiomyopathy.

Coronary computed tomographic angiography (CCTA) in community hospitals: "current and emerging role".

Coronary computed tomographic angiography (CCTA) is a rapidly evolving test for diagnosis of coronary artery disease. Although invasive coronary angiography is the gold standard for coronary artery disease (CAD), CCTA is an excellent noninvasive tool for evaluation of chest pain. There is ample evidence to support the cost-effective use of CCTA in the early triage process of patients presenting with chest pain in the emergency room. CCTA plays a critical role in the diagnosis of chest pain etiology as one of potentially fatal conditions, aortic dissection, pulmonary embolism, and myocardial infarction. This 'triple rule out' protocol is becoming an increasingly practicable and popular diagnostic tool in ERs across the country. In addition to a quick triage of chest pain patients, it may improve quality of care, decrease cost, and prevent medico-legal risk for missing potentially lethal conditions presenting as chest pain. CCTA is also helpful in the detection of subclinical and vulnerable coronary plaques. The major limitations for wide spread acceptance of this test include radiation exposure, motion artifacts, and its suboptimal imaging with increased body mass index.

The interaction between clopidogrel and proton pump inhibitors (PPI): is there any clinical relevance?

The potential interaction between clopidogrel and proton pump inhibitors (PPI) in patients with acute coronary syndrome (ACS) raises serious concerns for cardiologists. However, in patients on this combination of drugs, there is no conclusive evidence of an increase in adverse cardiovascular events. From pharmacologic and pharmacodynamic perspectives, there is a real interaction between clopidogrel and PPIs because of the competitive inhibition of CYP2C19 isoenzyme which is required for biotransformation of clopidogrel to its active metabolite. The consequent decrease in the availability of this active metabolite leads to attenuation of antiplatelet efficacy of clopidogrel. In several observational trials, it was shown that decreased antiplatelet effect of clopidogrel due to PPIs may translate into poor cardiovascular outcomes. However, an incomplete RCT (COGENT) and a post hoc analysis of two large trials (PRINCIPLE-TIMI 44 and TRITON-TIMI 38 trial) showed no significant adverse cardiovascular events with this combination. Caution is however needed in patients who are hypometabolizers of clopidogrel putting them at a higher risk of adverse coronary events. Since 3% of patients are likely to be hypometabolizers of clopidogrel, routine combination of clopidogrel and PPIs should be avoided. There is a heightened awareness of this interaction following multiple advisory warnings. At the same time, one should not withhold PPIs in patients who are at a high risk of developing gastrointestinal (GI) bleeding. In these patients, selected choices of PPI such as pantoprazole may be helpful and for low risk patients, serious consideration should be given to H(2) receptor antagonists or antacids. Therefore, while not compromising the cardioprotective effect of antiplatelet agents, the gastroprotective benefit of PPI should be strongly considered in patients who need both. Health care providers should remain alert to more outcome data. Future researchers will need to demonstrate the safety of coadministration of PPIs and clopidogrel and trials should be powered to detect major adverse cardiovascular events and facilitate risk stratification based on genetic polymorphism.

Aspirin and clopidogrel hyporesponsiveness and nonresponsiveness in patients with coronary artery stenting.

Patients undergoing coronary artery stenting receive an antiplatelet regimen to reduce the risk of antithrombotic complications. Current guidelines recommend the use of acetyl salicylic acid (aspirin) and clopidogrel as evidenced by large clinical trials. There has been a concern about variable responses of patients to aspirin and clopidogrel which may predispose them to subacute stent thrombosis or late stent thrombosis. Up to 25% of patients with acute myocardial infarction (AMI) undergoing percutaneous coronary intervention (PCI) were found to have hyporesponsiveness or resistance to clopidogrel which may predispose them to recurrent events. Dual antiplatelet regimen is a standard therapy in these patients and there is always a concern about variable responses to aspirin and clopidogrel predisposing them to acute coronary syndrome (ACS). Prevalence of this hyporesponsiveness or resistance may be due to noncompliance, genetic mutations, co-morbid situations and concomitant use of other drugs. This issue is of considerable importance in the era of coronary drug eluting stents when a long-term dual antiplatelet regimen is needed. This paper is a review for clinicians taking care of such patients with hyporesponsiveness or nonresponsiveness to dual antiplatelet regimen.

Thinking beyond low-density lipoprotein cholesterol: strategies to further reduce cardiovascular risk.

Several large statin trials and meta-analyses have demonstrated a reduction in low-density lipoprotein cholesterol (LDL-C) and cardiovascular morbidity and mortality. Some trials have also highlighted the significance of residual cardiovascular risk after treatment of LDL-C to target levels. This reflects the complex nature of residual cardiovascular risk. This residual risk is partially due to low HDL-C and high triglycerides (TG) despite achievement of LDL goals with statin therapy. The NCEP ATP III guidelines reported that low HDL-C is a significant and an independent risk factor for coronary heart disease (CHD) and is inversely related to CHD. Epidemiologic studies have also shown a similar inverse relationship of HDL-C with CHD. High-density lipoprotein cholesterol (HDL-C) may directly participate in the anti-atherogenic process by promoting efflux of cholesterol of the foam cells of atherogenic lesions. Many studies have demonstrated multiple anti-atherogenic actions of HDL-C and its role in promoting efflux of cholesterol from the foam cells. The residual risk by increased TG with or without low HDL-C can be assessed by calculating non-HDL-C and a reduction in TG results in decreased CHD.

Aortic valve sclerosis: is it a cardiovascular risk factor or a cardiac disease marker?

BACKGROUND: Aortic valve sclerosis, without stenosis, has been associated with an increased cardiovascular mortality and morbidity due to myocardial infarction. However, it is unclear whether it is a cardiovascular risk factor or a cardiac disease marker. The goal of our study is to evaluate the difference in the prevalence of cardiovascular disease and risk factors among patients with or without aortic sclerosis. METHODS: This observational study compared a group of 142 consecutive subjects with aortic valve sclerosis, assigned as group S, with a group of 101 subjects without aortic sclerosis, assigned as group C. Patients with bicuspid aortic valves and those with antegrade Doppler velocity across aortic valve leaflets exceeding 2.0 m/sec were excluded. RESULTS: Mean ages of groups S and C were 71 +/- 8, and 68.8 +/- 6 years, respectively (P value = not significant). The prevalence of smoking, diabetes, hypercholesterolemia, hypertension, pulse pressure, left ventricular diastolic dysfunction, atrial fibrillation, and stroke was not significantly different between the two groups. However, there was a significantly higher prevalence of left ventricular hypertrophy (P = 0.05), ventricular arrhythmias (P = 0.02), myocardial infarction (P = 0.04), and systolic heart failure (P = 0.04) in aortic sclerosis group. CONCLUSIONS: Aortic sclerosis is associated with a higher prevalence of left ventricular hypertrophy, ventricular arrhythmias, myocardial infarction, and systolic heart failure, while the prevalence of cardiovascular risk factors is not different between aortic sclerosis patients and controls. Hence, aortic sclerosis represents a cardiac disease marker useful for early identification of high-risk patients beyond cardiovascular risk factors rate.

Cardiac resynchronization therapy for CHF. The rewards and risks of biventricular pacing.

Patients with advanced heart failure continue to experience high morbidity and mortality despite recent progress made with the use of such drugs as beta-blockers and angiotensin-aldosterone inhibitors. Cardiac transplantation has severe limitations due to the short supply of organs and the ineligibility of most CHF patients for this therapy. Approved heart-assist devices are cumbersome and costly. Therefore, these devices are currently used mainly in tertiary care centers in a limited number of patients. CRT has been rapidly evolving as a viable and beneficial therapy that is universally applicable by percutaneous method in patients with moderate or severe heart failure. Its relative ease of use and cost-effectiveness make it an attractive option for patients with symptomatic heart failure. Therefore, more physicians are becoming aware of the low threshold for its use.

Modern surgical and interventional options for the management of heart failure.

Current standard drug therapy provides only palliative and symptomatic relief for patients with severe heart failure, but there is now a wide array of device applications that holds great promise for reducing the mortality and disability that result from heart failure. Patients with severe chronic and refractory heart failure should be considered for heart transplantation or mechanical circulatory supportwith a ventricular assist device. Newer surgical and interventional treatments are in continuous evolution.

Adaptive-outward and maladaptive-inward arterial remodeling measured by intravascular ultrasound in hyperhomocysteinemia and diabetes.

BACKGROUND: Coronary artery remodeling implies structural changes in the vessel wall in response to various pathophysiologic conditions. However, the classification of remodeling is unclear. We hypothesized that the adaptive, positive-outward remodeling is a reactive and compensatory response to the stress. The maladaptive negative-inward constrictive remodeling is a passive atherosclerotic condition in which the vessel becomes stiffer. METHODS: Patients with atherosclerotic lesions underwent intravascular ultrasound (IVUS) scans. The size of the vessels distal to and proximal to plaques were analyzed by IVUS. Diabetes was created in mice by an intraperitoneal injection of alloxan (65 mg/kg). To reduce remodeling, mice received ciglitazone, an agonist of peroxisome proliferators activated receptor-gamma (PPARgamma) in drinking water. After 8 weeks, atherosclerotic vessels were analyzed for collagen and elastin. RESULTS: IVUS data suggest an adaptive coronary arterial remodeling was a positive compensatory response to various pathologic stimuli; for example, with the deposition of atherosclerotic plaque, coronary arterial segments enlarged to maintain luminal area. This phenomenon was commonly observed during the initial phases of the development of atherosclerosis. However, negative coronary artery remodeling, or a decrease in vessel area with the formation of atherosclerotic plaque, was maladaptive and was associated with smoking, hypertension, hyperhomocysteinemia, diabetes mellitus, and also after percutaneous coronary interventions (restenosis). In diabetic mice, there was increased collagen and decreased elastin contents; however, treatment with ciglitazone ameliorated the decrease in elastin contents. CONCLUSION: Global enlargement of the coronary vascular tree occurs during pressure and volume overload associated with ventricular hypertrophic states such as athletic conditioning, hypertensive heart disease, and dilated cardiomyopathy. On the other hand, maladaptive coronary arterial remodeling occurs in patients with severe deconditioning, diabetes mellitus, after coronary artery bypass surgery, and in some instances, postintervention.

Post-transplantation lymphoproliferative disorder in heart and kidney transplant patients: a single-center experience.

BACKGROUND: Post-transplantation lymphoproliferative disorder (PTLD) after heart transplantation is a fatal complication, and standard treatment is either ineffective or too toxic. We have studied the incidence, clinical course, prognostic factors, and different treatment regimens pertaining to PTLD in 110 heart and 80 kidney transplant recipients. METHODS: Information was abstracted from chart review of 110 heart transplant recipients and 80 kidney transplant recipients between January 1989 and October 2002. We report 15 patients with PTLD, 6 patients received a heart transplant and 9 patients received a renal transplant. RESULTS: The overall incidence of PTLD was 8.9% (5.4% in heart and 13.7% in kidney transplant recipients). The average interval between transplantation and the diagnosis of PTLD in heart transplantation patients was 5.5 years, and their overall mean age was 44 years. The indications for transplantation were ischemic cardiomyopathy in 5 patients (1 patient received both heart and kidney transplants), glomerulonephritis in 6 patients, diabetes nephropathy in 2 patients, and polycystic disease in 2 patients. Six patients were diagnosed with early disease (<12 months), 7 with late onset (1 to 10 years), and 2 with very late onset (>10 years). Five patients had PTLD grade 2 (2 heart and 3 kidney transplants) and 10 patients had PTLD grade 3 (4 heart and 6 kidney transplants). Immunosuppressive treatment for PTLD patients consisted of cyclosporine, 73% (11/15); tacrolimus, 6.6% (1/15); prednisone, 100% (15/15); azathioprine, 80% (12/15); mycophenolate mofetil, 20% (3/15); murine monoclonal anti-human CD3 (OKT3), 7% (1/15); and anti-thymocyte globulin, 13% (2/15). PTLD developed in 11.5% of patients with primary Epstein-Barr virus infection and in 28.9% of patients with primary cytomegalovirus infection. Five patients received rituximab therapy, 5 had conventional chemotherapy, 3 had radiotherapy, 3 had reduction in immunosuppression, 2 had ganciclovir, 1 underwent surgery, and 1 patient died before receiving treatment. The mortality rate was 26.6%. The average interval between transplantation and the diagnosis of PTLD in heart transplant recipients was 5.5 years. The mortality rate was significantly higher in the control group than in the rituximab group. CONCLUSIONS: Caucasian race and male gender were independent risk factors for developing PTLD. Pretransplant cytomegalovirus seropositive status is a strong predictor of developing PTLD. Management of PTLD requires randomized controlled trials of various chemotherapeutic and antiviral drugs regimens. Treatment of PTLD with rituximab is a beneficial alternative with a favorable outcome. Patients in whom primary Epstein-Barr virus, cytomegalovirus, or hepatitis C infection develop after transplantation should be managed with heightened surveillance for the development of PTLD. Further randomized trials are needed to evaluate the efficacy of antiviral drugs, intravenous immunoglobulin, interferon, and prophylactic Epstein-Barr virus immunization strategies.

Evidence-based drug treatment of heart failure.

Modern management strategies have revolutionized the treatment of patients with acute and chronic heart failure (HF). Physicians should identify the risks and benefits of each drug or interventional option being considered for the treatment of HF. Inhibition of the neurohormonal axis with angiotensin converting enzyme (ACE) inhibitors and beta-blockers has significantly improved morbidity and mortality of patients with chronic HF. An aggressive approach targeted at improving hemodynamics and end-organ function is warranted during acute exacerbations or decompensated heart failure. Immediate recognition and management of potentially reversible causes and simultaneous initiation of supportive therapy to augment the cardiac output are key elements to the successful treatment of acute heart failure.

Pathology, prognosis, and prevention of heart failure.

Optimal management of patients with heart failure (HF) should be guided by thorough evaluation and use of functional classification and disease staging systems. Though the understanding of precise underlying pathophysiological mechanisms has increased dramatically in recent years, it is essential to continue the search for greater efficacy in preventing, controlling, and reversing this pathological state. Recent developments in the diagnosis and treatment of heart failure have improved prognosis in terms of both survival and morbidity due to re-hospitalization. The underutilization of medical and preventive therapies in patients with heart failure is a major public health issue, despite the recommendations of various evidence-based guide lines. Patient education and disease management programs have been shown to optimize HF-management by bridging the gap between evidence-based medicine and clinical practice, thereby, reducing hospitalization rate. This paper, the first in a series of three papers, will identify the pathology, prognosis and prevention of heart failure, while the paper to follow will discuss modern methods of interventional management.

Expression of matrix metalloproteinase activity in idiopathic dilated cardiomyopathy: a marker of cardiac dilatation.

BACKGROUND: Idiopathic dilated cardiomyopathy (DCM), ventricular systolic dysfunction and chamber dilatation are accompanied by architectural remodeling, wall thinning and cardiac myocyte slippage. Recent work has demonstrated an association between collagen degradation and an increased expression of matrix metalloproteinases (MMPs). Accordingly, we have sought to correlate (a) collagen degradation with MMP elevations and, (b) assay the neutralizing potential of a known inhibitor of MMP, tetracycline on MMPs in DCM. METHODS: Assessment of LV volume and shape by 2-D echocardiography was performed. Light microscopic assessment of histopathology in picrosirius red stained biopsy samples of 11 DCM patients and six post-transplant patients was performed. Zymographic estimation of MMP activity and influence of tetracycline on MMP activity was assessed. RESULTS: Small amount of interstitial collagen was noted in the control group, whereas in the DCM hearts, chamber dilatation was associated with areas of scanty myocyte necrosis, islands of excess collagen, and focal areas of absent or scanty collagen with intact myocytes. In cardiomyopathic tissue, collagenase activity was markedly elevated at 63% compared with 8% in post-transplant tissue. Tetracycline at a concentration of 285+/-10 microM (IC50) inhibited collagenase activity by 50% in cardiomyopathic tissue. CONCLUSIONS: Areas of focal interstitial collagen accumulation were accompanied by collagen fiber lysis and increased collagenase activity in dilated cardiomyopathy. This enhanced collagenolytic activity found in endomyocardial biopsy tissue was inhibited by tetracycline. The non-antibiotic property of tetracycline may be of potential value in the prevention of ventricular dilatation in idiopathic dilated cardiomyopathy.

Remodeling of coronary arteries in diabetic patients-an intravascular ultrasound study.

BACKGROUND: Coronary artery remodeling is a structural change in the vessel wall and typically in response to atherosclerotic plaque. The nature of coronary remodeling has been described in different clinical situations. However, remodeling characteristics of coronary arteries of diabetic patients have never been studied. HYPOTHESIS: We tested the hypothesis that positive remodeling of coronary artery in response to atherosclerotic plaque in diabetic patients would be less compared to nondiabetic patients. METHODS: Coronary intravascular ultrasound analysis of data in 26 consecutive patients (12 diabetic and 14 nondiabetic) was performed. Linear regression analyses of vessel area versus plaque area were carried out to establish a relation between the degree of plaque and the extent of remodeling in diabetic and nondiabetic groups. RESULTS: The positive remodeling quantified as the slope of the regression line was similar in both the groups (diabetic group 1.32 and nondiabetic group 0.80) when all segments with different plaque areas were considered (P > 0.05). However, the diabetic group had greater positive remodeling in segments with plaque area less than 55%, as the slope for diabetic group was 2.01 and nondiabetic group was 1.40 (P < 0.05). CONCLUSIONS: Both the diabetic and nondiabetic patients had positive remodeling in response to atherosclerotic plaque formation. Diabetics had greater positive remodeling in the early stages of atherosclerosis compared to nondiabetics, thus providing evidence against our hypothesis. The adverse clinical outcomes in diabetics may not be due to inadequate positive remodeling of coronary arteries as previously thought.

Echocardiography predicts adverse cardiac remodelling in heart failure.

Congestive heart failure remains a primary cause of cardiovascular-related events. Heart failure patients face two health care challenges. First, they are uncertain about their prognosis and second, they have an unpredictable clinical course with recurrent exacerbations of heart failure. The echocardiogram is an easily accessible bedside test without any associated procedural complications. Additionally, it provides a wealth of information about chamber size and function, valve integrity and the pericardial sac. In the present review, the most common echocardiographic predictors of impending cardiac events in congestive heart failure are described.

Role of transesophageal echocardiography in detecting implantable cardioverter defibrillator lead infection.

Implantable cardioverter defibrillator (ICD) lead infection is a rare condition with reported incidence of 0.2% to 16%. It usually presents with persistent bacteremia or fever of unknown origin and requires high clinical suspicion for diagnosis. Whenever ICD lead infection is suspected, transesophageal echocardiography is the diagnostic technique of choice for detection and characterization of the lesions. Lead infections are extremely difficult to manage conservatively and surgical removal of the entire defibrillator system is recommended along with antimicrobial therapy. We describe a case of recurrent staphylococci bacteremia due to an ICD lead infection in a patient with arrhythmogenic right ventricular dysplasia.