Relation of peak creatine kinase levels during acute myocardial infarction to presence or absence of previous manifestations of myocardial ischemia (angina pectoris or healed myocardial infarction)

Dyslipidemia and progression of cardiovascular calcification (CVC) in patients with end-stage renal disease (ESRD)

Dyslipidemia and progression of cardiovascular calcification (CVC) in patients with end-stage renal disease (ESRD). Cardiovascular calcification (CVC) is commonly encountered both in the general population as well as in patients with end-stage renal disease (ESRD). The etiology of CVC in patients with ESRD is multifactorial. Despite that, current debate remains narrowly focused on the role of calcium loading from calcium-based phosphate binders (CBPB) in the pathogenesis and progression of CVC. Yet, the alleged link between these binders and CVC has not been substantiated in well-designed controlled trials. In contrast, the purported role of sevelamer, a non-calcium-based phosphate binder, in slowing the progression of CVC in dialysis patients has attracted widespread attention. The beneficial effect of sevelamer on progression of calcification was thought to be due to lower calcium loading during its use. However, an alternative and possibly more likely mechanism involves sevelamer-induced lowering of LDL cholesterol. In this context, previous studies in individuals with normal renal function have documented amelioration of coronary artery calcification (CAC) with reduction of LDL-cholesterol by treatment with HMG-CoA reductase inhibitors (statins). Given that CAC is a well-accepted marker of atherosclerosis, and that high plasma cholesterol concentration is one of the main risk factors for atherosclerosis, then it is not unreasonable to suspect that CAC may be halted or even reversed by lowering of LDL cholesterol level with statin therapy. Unfortunately, the effect of lowering the LDL-cholesterol level on CAC has not been studied in patients with ESRD. Therefore, conclusions about this important topic should await the results of well-designed clinical studies that control for all factors potentially implicated in the CVC burden of patients with ESRD. In this review, I will discuss the role of various potential mechanisms involved in the pathogenesis of CVC in patients with ESRD, and emphasize the role of dyslipidemia and its treatment in this important clinical entity.

Detection of subclinical cardiovascular disease: the emerging role of electron beam computed tomography

BACKGROUND

Although extraordinary advances have been made in the management of advanced coronary artery disease, little progress has been made in its prevention. Traditional screening methods utilizing risk factor profiles and exercise treadmill tests have failed to identify populations who will subsequently have coronary events with a high degree of predictive accuracy.

METHODS

We review the pathobiologic basis and clinical utility of electron beam computed tomography (EBCT) to detect coronary artery calcium as a screening tool for subclinical coronary artery disease. Because EBCT is able to perform subsecond imaging of the heart, it can detect and quantitate coronary artery calcium with a high degree of precision. Coronary artery calcium is a marker of complex atherosclerosis.

RESULTS

Over 4,000 asymptomatic patients in several series have been studied with EBCT and followed prospectively for an average of 42 months (range 37-72 months). A positive scan is associated with a risk ratio for future coronary events of 8.7 (95% confidence interval 2.67 to 28.13). These data indicate that EBCT has the ability to detect subclinical coronary artery disease and predict future coronary events better than any previous existing method or technology.

CONCLUSION

EBCT coronary artery screening may prove to be a valuable adjunct to the traditional methods for the detection of subclinical coronary artery disease and to identify those who would benefit from focused preventive therapies.

Prodromal angina limits infarct size. A role for ischemic preconditioning

BACKGROUND

In the experimental setting, it has been demonstrated that preconditioning myocardium before prolonged occlusion with brief ischemic episodes affords substantial protection to the cells by delaying lethal injury, thereby limiting infarct size. Whether the same occurs in humans remains unknown.

METHODS AND RESULTS

This study was undertaken to determine whether new-onset prodromal angina, defined as chest pain episodes limited to the 24 hours before myocardial infarction, is the clinical correlate of the ischemic preconditioning phenomenon. Twenty-five patients with their first anterior myocardial infarction treated with thrombolysis (recombinant tissue plasminogen activator [r-TPA], 100 mg/3 hours) were retrospectively included in the study because they met the following criteria: (1) < 120 minutes from onset of symptoms to reperfusion therapy, (2) < 90 minutes from the beginning of thrombolytic therapy to reperfusion (defined as rapid ST elevation reduction > 50%), (3) a patient infarct-related coronary artery with TIMI 3 flow and complete absence of collateral circulation to the infarct related artery (assessed at 24 +/- 5 days), and (4) the presence of new-onset prodromal angina, ie, typical chest pain episodes occurring at rest within 24 hours or, alternatively, a complete absence of symptoms before onset of infarction. Therefore, on the basis of their clinical status before infarction, the patients were divided into two groups: group 1, 13 patients without prodromal angina, and group 2, 12 patients with prodromal angina. Despite no difference in time to treatment (81 +/- 19 versus 75 +/- 21 minutes in group 1 and group 2, respectively; P = NS) and time to reperfusion (58 +/- 34 versus 46 +/- 24 minutes; P = NS), the peak of CKMB release was markedly lower in group 2 (86.3 +/- 66 versus 192.3 +/- 108.3 IU/L; P < .01). In addition, although both groups were comparable in terms of area at risk (amount of myocardium beyond the infarct-related stenosis; 15.1 +/- 4.6 versus 13.7 +/- 4.6 hypokinetic segments in group 1 and group 2, respectively, P = NS), the final infarct size (11 +/- 7.5 versus 5.6 +/- 4 hypokinetic segments, P < .04) was smaller in group 2. Thus, the limitation of the infarct size was significantly greater in group 2 (69% versus 36%; P < .05), and this represents an additional 33% reduction (95% confidence intervals, 7.1% to 58.9%; P = .01) in the group of patients with prodromal angina. Also, the third index, that is, the ECG, showed a favorable trend toward a lesser number of Q waves and a higher sigma R waves, although the values did not reach statistical significance.

CONCLUSIONS

Despite a similar area at risk, patients with new-onset prodromal angina showed a significantly smaller infarct size compared with patients without prodromal symptoms. Since the two groups had similar times to reperfusion and no evidence of collateral circulation to the infarct related artery, the protection afforded by angina in group 2 patients might be explained by the occurrence of ischemic preconditioning.

Influence of coronary collateral vessels on myocardial infarct size in humans. Results of phase I thrombolysis in myocardial infarction (TIMI) trial. The TIMI Investigators

BACKGROUND

The influence of coronary collateral vessels on infarct size in humans remains controversial, partly because no previous study has examined the impact of collaterals present at the onset of acute myocardial infarction on infarct size.

METHODS AND RESULTS

The present study used the data base of the Thrombolysis in Myocardial Infarction (TIMI) Phase I trial to correlate the presence or absence of angiographically documented collaterals in the initial hours of myocardial infarct evolution with the size of the infarct as assessed by serial measurements of serum creatine kinase (CK). To avoid the confounding effects of reperfusion on enzymatic estimates of infarct size, this report is limited to those 125 patients who failed to recanalize at 90 minutes after administration of tissue plasminogen activator or streptokinase. Patients with angiographically documented collaterals (group A, n = 51) had significantly lower values of peak serum CK than patients without collaterals (group B, n = 74) (1,877 +/- 216 versus 2,661 +/- 212 IU/l, respectively [mean +/- SEM], p = 0.004). Similarly, CK-derived infarct size estimates were significantly lower in group A than in group B (20.6 +/- 2.5 versus 31.4 +/- 2.8 CK gram equivalents, p = 0.001). The infarct size observed in patients with collaterals was less for anterior infarctions as well as for infarctions of other locations; thus, the beneficial effects of collaterals were independent of the site of the infarct. In 65 of the 125 patients who failed to reperfuse, left ventricular ejection fraction (LVEF) was assessed by contrast ventriculography both at initial cardiac catheterization (before thrombolytic therapy) and at hospital discharge. Among the patients who had both studies, global LVEF tended to increase from pretreatment to hospital discharge in group A (from 50.6 +/- 1.8% to 53.4 +/- 1.8%, p = 0.10) but decreased in group B patients (from 50.3 +/- 1.8% to 47.8 +/- 1.7%, p = 0.02). At hospital discharge, global LVEF was greater in patients with coronary collaterals (53.5 +/- 1.7% versus 49.6 +/- 1.7%, p = 0.01).

CONCLUSIONS

The results demonstrate that, in patients in whom thrombolytic therapy fails to induce reperfusion, the presence of coronary collateral vessels at the onset of myocardial infarction is associated with limitation of infarct size as assessed enzymatically and with improved ventricular function on discharge as assessed by LVEF.

Early detection of acute myocardial infarction in patients presenting with chest pain and nondiagnostic ECGs: serial CK-MB sampling in the emergency department

STUDY OBJECTIVES

Patients presenting to the emergency department with chest discomfort are a difficult problem for emergency physicians. Nearly 50% of patients with acute myocardial infarction (AMI) will initially have nondiagnostic ECGs on ED presentation. The purpose of this study was to determine if patients with AMI having nondiagnostic ECGs could be identified using new immunochemical assays for serial CK-MB sampling in the ED.

DESIGN

Chest pain patients, more than 30 years old, with pain not caused by trauma or explained by radiographic findings, were eligible for the study. Serial serum samples were drawn on ED presentation (zero hours) and three hours after presentation, then analyzed for CK-MB using four immunochemical methods and electrophoresis. Standard World Health Organization criteria were used to establish the diagnosis of AMI, including new Q-wave formation or elevation of standard in-hospital serum cardiac enzyme markers.

SETTING

A tertiary cardiac care community hospital.

MEASUREMENTS AND MAIN RESULTS

The serum from 183 patients hospitalized for possible ischemic chest pain was collected and analyzed. Thirty-one of 183 patients (17%) were found to have AMI by standard in-hospital criteria. Sixteen of the 31 patients (52%) with AMI had nondiagnostic ECGs on presentation. Immunochemical determination of serial CK-MB levels provided a sensitive and specific method for detecting AMI in patients within three hours after ED presentation compared with standard electrophoresis. The four immunochemical methods demonstrated a range in sensitivity from 50% to 62.1% on ED presentation versus 92% to 96.7% three hours later. The immunochemical tests demonstrated specificities ranging from 83.0% to 96.4% at three hours, with three of the four tests having specificities of 92% or greater. Electrophoresis had a sensitivity of 34.5% on ED presentation, increasing to 76.9% at three hours, with a specificity of 98.6%.

CONCLUSIONS

Immunochemical CK-MB methods allowed rapid, sensitive detection of AMI in the ED. Early detection of AMI offers many potential advantages to the emergency physician. Early detection of AMI, while the patient is in the ED, could direct disposition of this potentially unstable patient to an intensive care setting. Such information may prevent the ED discharge of patients with AMI having nondiagnostic ECGs. The diagnosis of AMI within a six-hour period after symptom onset may allow thrombolytic therapy to be given to patients with AMI not having diagnostic ECGs. This study served as a pilot trial for a multicenter study of the Emergency Medicine Cardiac Research Group, which is currently ongoing.

Comparison of the natural history of new onset and exacerbated chronic ischemic heart disease. The Chest Pain Study Group

To compare the natural history of patients with new onset ischemic heart disease with that of patients with exacerbations of chronic ischemic heart disease, short- and long-term outcomes of 3,465 emergency room patients with acute ischemic heart disease at four community and three university hospitals were evaluated. Acute myocardial infarction was diagnosed in 598 (33%) of the 1,835 patients with a prior history of infarction or angina and 934 (57%) of the 1,630 without such a history (p less than 0.001). Patients with new onset ischemic heart disease with acute myocardial infarction were more likely than patients with infarction and exacerbated chronic ischemic heart disease to have Q wave infarction (57% versus 36%) and to receive thrombolytic therapy (11% versus 5%); they also had higher maximal creatine kinase levels (1,088 +/- 1,299 versus 733 +/- 906 U/liter) (p less than 0.0001 for all three). After adjustment for differences in clinical presentation and initial triage, patients with new onset ischemic heart disease with acute myocardial infarction were less likely than the comparison group to have congestive complications (odds ratio 0.63, 95% confidence interval 0.47 to 0.84, p less than 0.01) but not less likely to have arrhythmic, ischemic or overall complications. Among patients with angina without acute myocardial infarction, patients with new onset ischemic heart disease were less likely to have recurrent ischemic pain and congestive heart failure. In multivariate analysis of long-term follow-up data on 457 patients from one hospital, patients with new onset ischemic heart disease had better cardiovascular survival rates.(ABSTRACT TRUNCATED AT 250 WORDS)