Use of Biomarkers to Predict Readmission for Congestive Heart Failure

Acute decompensated heart failure (ADHF) is a major reason for repeated hospitalizations. Identifying those patients with ADHF at risk for readmission is critical so that preventive interventions can be implemented. Biomarkers such as B-type natriuretic peptide (BNP), high-sensitivity troponin I, and galectin-3 (Gal-3) assessed at discharge may be useful, although their role in predicting short-term readmission is not well defined in the literature. We enrolled and had follow-up data for 101 participants admitted to our facility from April 2013 to March 2015 with a primary diagnosis of ADHF. Gal-3, high-sensitivity troponin I, and BNP were obtained within 48 hours before hospital discharge after management of ADHF. Gal-3 was assessed using 2 commercially available assays. We compared subjects who were and were not readmitted. Discharge BNP was found to be a significant predictor of 30- and 60-day readmission (area under the curve [AUC] 0.69 [p = 0.046], AUC 0.7 [p = 0.005], respectively). The addition of Gal-3 to discharge BNP provided significantly improved prediction of 60-day readmission. Gal-3 alone was found to be a significant predictor of 60-day readmission in patients with preserved ejection fraction (AUC 0.85, p <0.001). The net reclassification improvement was 55.2 (p = 0.037). Using multivariate analysis, for every 100 pg/L BNP increase, the probability of readmission increased by approximately 10%, and for every 1-ng/ml Gal-3 increase, the probability further increased 8%. A statistically significant net reclassification improvement was not found on examination of 30-day readmission. In conclusion, measurement of both Gal-3 and BNP at hospital discharge provides significant prediction of hospital readmission within 60 days. When combined, the prediction of readmission is significantly improved.

Short- and Long-term Biologic Variability of Galectin-3 and Other Cardiac Biomarkers in Patients with Stable Heart Failure and Healthy Adults

BACKGROUND

Galectin-3 (Gal-3) has been suggested as a prognostic biomarker in heart failure (HF) patients that may better reflect disease progression than traditional markers, including B-type natriuretic peptide (BNP) and cardiac troponins. To fully establish the utility of any biomarker in HF, its biologic variability must be characterized.

METHODS

To assess biologic variability, 59 patients were prospectively recruited, including 23 male and 16 female patients with stable HF and 10 male and 10 female healthy individuals. Gal-3, BNP, and high-sensitivity cardiac troponin I (hs-cTnI) were assayed at 5 time points within a 3-week period to assess short-term biologic variability. Long-term (3-month) biologic variability was assessed with samples collected at enrollment and after 4, 8, and 12 weeks.

RESULTS

Among healthy individuals, mean short-term biologic variability, expressed as intraindividual CV (CVI), was 4.5% for Gal-3, 29.0% for BNP, and 14.5% for hs-cTnI; long-term biologic variability was 5.5% for Gal-3, 34.7% for BNP, and 14.7% for hs-cTnI. In stable HF patients, mean short-term biologic variability was 7.1% for Gal-3, 22.5% for BNP, and 8.5% for hs-cTnI, and mean long-term biologic variability was 7.7% for Gal-3, 27.6% for BNP, and 9.6% for hs-cTnI.

CONCLUSIONS

The finding that Gal-3 has minimal intraindividual biological variability adds to its potential as a useful biomarker in HF patients.

Impact on Patient Management and Outcome of Switching between 2 Contemporary Sensitive Cardiac Troponin Assays

BACKGROUND

Myocardial infarction is characterized by an increase of cardiac troponin I (cTnI) above the 99th percentile of a reference population. Our hospital switched from 1 contemporary cTnI assay to another and observed a doubling of cTnI results above the assays' respective 99th percentile cutoffs. We investigated the potential impact on inpatient management and outcomes.

METHODS

We performed a retrospective cohort study of 45 498 individuals with ≥1 cTnI result between January 2013 and June 2014. The Dimension cTnI assay was used in 2013; the Abbott Architect cTnI assay was used in 2014.

RESULTS

Before switching cTnI assays, 19.2% (4742/30 872) of patients had at least 1 of the first 3 cTnIs above the 99th percentile (0.07 μg/L). After switching to the Architect cTnI assay, 31.4% (4034/14 626) of patients had at least 1 cTnI above the 99th percentile (0.03 μg/L). This increase was due to the difference in the assays' 99th percentile cutoffs. Having an increased cTnI reported on the Architect assay that would not have been reported as such on the Dimension assay (0.03–0.06 μg/L) correlated with increased inpatient mortality, length of stay, non–ST elevation myocardial infarction diagnosis, therapeutic heparin use, and percutaneous coronary intervention, relative to individuals with cTnI &lt;0.03 μg/L.

CONCLUSIONS

The changes observed in patient outcomes and management were likely due to the increased sensitivity and lower 99th percentile cutoff of the Architect assay. It is important to recognize the potential impact that differences in sensitivity and assay configuration may have on patient management.

Executive dysfunction and depressive symptoms associated with reduced participation of people with severe congestive heart failure

OBJECTIVE

We investigated participation levels and relationships among cognition, depression, and participation for people with severe congestive heart failure (CHF).

METHOD

People with severe CHF (New York Heart Association Class III or IV) awaiting heart transplantation (N = 27) completed standardized tests of cognition and self-report measures of executive dysfunction, depressive symptoms, and participation.

RESULTS

Possible depression (64%) and cognitive impairment (15%-59%) were prevalent. Participants reported significant reductions in participation across all activity domains since CHF diagnosis (ps < .001). Worse executive dysfunction and depressive symptoms were associated with reduced participation and together accounted for 35%-46% of the variance in participation (ps < .01).

CONCLUSION

Participation restrictions associated with CHF are not limited to physically demanding activities and are significantly associated with executive dysfunction and depression. Cardiac rehabilitation should address cognitive and psychological functioning in the context of all life situations instead of focusing solely on physical function and disability.

Acute decompensated heart failure: contemporary medical management

Hospitalizations for acute decompensated heart failure are increasing in the United States. Moreover, the prevalence of heart failure is increasing consequent to an increased number of older individuals, as well as to improvement in therapies for coronary artery disease and sudden cardiac death that have enabled patients to live longer with cardiovascular disease. The main treatment goals in the hospitalized patient with heart failure are to restore euvolemia and to minimize adverse events. Common in-hospital treatments include intravenous diuretics, vasodilators, and inotropic agents. Novel pharmaceutical agents have shown promise in the treatment of acute decompensated heart failure and may simplify the treatment and reduce the morbidity associated with the disease. This review summarizes the contemporary management of patients with acute decompensated heart failure.

Should UNOS Status 2 Patients Undergo Transplantation?

BACKGROUND

With recent improvements in medical and device therapy, the benefit of cardiac transplantation for UNOS Status 2 patients has been questioned. No randomized trial has been performed to compare transplantation versus contemporary medical therapy.

METHODS

Between January 1996 and December 2003, 203 patients were listed at our institution for heart transplantation as UNOS Status 2. We performed a retrospective review to determine outcomes in these patients.

RESULTS

Demographics of this cohort revealed a mean age of 52 years, female sex in 28%, and ischemic etiology in 47%. Eighty-one patients (40%) had an implantable cardiac defibrillator. A total of 64 patients (32%) had to be upgraded in their UNOS status, with 9 requiring a left ventricular assist device. Of the entire group, 95 (47%) underwent transplantation at a mean time of 303 days, 45 (22%) died while waiting at a mean time of 397 days, and 24 (12%) were removed from the waiting list due to deterioration in medical condition such that transplantation was no longer an option. The remaining patients continue to wait or have been removed from consideration due to improved condition. Survival at 1- and 3-years postlisting was 94% and 87% for patients who received transplants compared to 81% and 57% for patients who did not receive transplants (P < .01).

CONCLUSION

A significant number of patients listed as Status 2 are upgraded in UNOS status or die while on the waiting list. Early and midterm survival is significantly better with transplantation. Identification of variables associated with deterioration may allow for better risk stratification in the future. At this point, transplantation offers the best outcome.

Prospective comparison of ventilatory equivalent versus peak oxygen consumption in predicting outcomes of patients with heart failure

In patients with heart failure (HF), peak exercise oxygen consumption (VO2) is an important prognostic tool on which critical clinical decisions are made. However, recent retrospective data have suggested that ventilatory equivalent (VE = ventilation [liters per minute]/VO2 [liters per minute]) may be a stronger predictor of outcomes than VO2 in patients with HF on modern medical therapies. We prospectively collected baseline demographics, cardiovascular history, hemodynamics, and exercise ventilatory data from 221 consecutive patients with HF who underwent treadmill exercise VO2 testing. The composite primary end point was death or heart transplantation. Mean follow-up was 508 days, during which 27 events occurred (13 deaths and 14 transplantations). One-year event-free survival was 88% (n = 104 with 1-year follow-up). Mean age was 49 years, 68% were men, 84% were taking beta blockers, 82% were taking angiotensin-converting enzyme inhibitors, and 21% had an implantable cardioverter-defibrillator. Mean VO2 was 16 +/- 5 ml/kg/min. Mean VE was 47.4 +/- 15.2. Univariate predictors of events included lower VO2 (p <0.0001), higher heart rate at rest (p = 0.05), and presence of an implantable cardioverter-defibrillator (p = 0.024). Higher VE (p = 0.10) and lower maximum systolic blood pressure (p = 0.09) were of borderline significance. Age, gender, HF etiology or severity, and other ventilatory parameters were not significant predictors. Multivariate models that incorporated VE, VO2, or their combination confirmed VO2 as an independent predictor of event-free survival (p < or =0.0002); VE did not independently predict outcomes. Other independent predictors were higher heart rate at rest (p < or =0.02) and presence of an implantable cardioverter-defibrillator (p < or =0.04). In conclusion, peak VO2, but not VE, predicts clinical outcomes of patients with HF who are treated with contemporary medical therapies.

Effect of antecedent systemic hypertension on subsequent left ventricular dilation after acute myocardial infarction (from the Survival and Ventricular Enlargement trial)

Whether antecedent systemic hypertension influences the risk of subsequent left ventricular (LV) dilation in patients after an acute myocardial infarction with LV systolic dysfunction is unclear. We assessed echocardiographic evidence of ventricular remodeling from baseline (mean +/- SD 11 +/- 3 days) to 2 years after an acute myocardial infarction in 122 hypertensive (defined as a history of treated hypertension, baseline systolic blood pressure > or =140 or baseline diastolic blood pressure > or =90 mm Hg) and 334 nonhypertensive patients in the Survival and Ventricular Enlargement echocardiographic substudy. Compared with nonhypertensives, baseline heart size, defined as the sum of the average short- and long-axis LV cavity areas, was similar (70.1 +/- 11.9 vs 68.8 +/- 11.2 cm(2), p = 0.33 at end-diastole; 50.1 +/- 11.3 vs 48.8 +/- 10.8 cm(2), p = 0.31 at end-systole), but short-axis LV myocardial area (24.7 +/- 4.3 vs 25.7 +/- 5.0 cm(2), p = 0.043) and wall thickness (1.15 +/- 0.16 vs 1.21 +/- 0.17 cm, p = 0.004) at end-diastole were greater among hypertensives. The myocardial infarct segment lengths were similar in the 2 groups (p = 0.22). Although LV cavity areas increased significantly in the 2 groups from baseline to 2 years (p < or =0.001), the increase was significantly greater in hypertensives than in nonhypertensives (+5.6 +/- 11.5 vs +2.2 +/- 10.7 cm(2), p = 0.005 at end-diastole; +6.23 +/- 12.75 vs +2.94 +/- 11.4 cm(2), p = 0.012 at end-systole). There was no concomitant difference in the change in LV myocardial area or LV wall thickness between the 2 groups (p >0.30). After adjusting for known confounders, antecedent hypertension was associated with a doubling of the risk of LV dilation (50.8% vs 37.7%, odds ratio 2.09, 95% confidence interval 1.27 to 3.45, p = 0.004). This association was not modified by diabetes mellitus, myocardial infarct segment length, or captopril use (all p values for interaction >0.10). We conclude that antecedent hypertension is associated with subsequent LV dilation in patients after acute myocardial infarction with LV systolic dysfunction.

Alcohol consumption and prognosis in patients with left ventricular systolic dysfunction after a myocardial infarction

OBJECTIVES

We assessed the influence of alcohol intake on the development of symptomatic heart failure (HF) in patients with left ventricular (LV) dysfunction after a myocardial infarction (MI).

BACKGROUND

In contrast to protection from coronary heart disease, alcohol consumption has been linked to cardiodepressant effects and has been considered contraindicated in patients with HF.

METHODS

The Survival And Ventricular Enlargement (SAVE) trial randomized 2231 patients with a LV ejection fraction (EF) <40% following MI to an angiotensin-converting enzyme inhibitor or placebo. Patients were classified as nondrinkers, light-to-moderate drinkers (1 to 10 drinks/week), or heavy drinkers (>10 drinks/week) based on alcohol consumption reported at baseline. The primary outcome was hospitalization for HF or need for an open-label angiotensin-converting enzyme inhibitor. Analyses were repeated using alcohol consumption reported three months after MI.

RESULTS

Nondrinkers were older and had more comorbidities than light-to-moderate and heavy drinkers. In univariate analyses, baseline light-to-moderate alcohol intake was associated with a lower incidence of HF compared with nondrinkers (hazard ratio [HR] 0.71; 95% confidence interval [CI] 0.57 to 0.87), whereas heavy drinking was not (HR 0.91; 95% CI 0.67 to 1.23). After adjustment for baseline differences, light-to-moderate baseline alcohol consumption no longer significantly influenced the development of HF (light-to-moderate drinkers HR 0.93; 95% CI 0.75 to 1.17; heavy drinkers HR 1.25; 95% CI 0.91 to 1.72). Alcohol consumption reported three months after the MI similarly did not modify the risk of adverse outcome.

CONCLUSIONS

In patients with LV dysfunction after an MI, light-to-moderate alcohol intake either at baseline or following MI did not alter the risk for the development of HF requiring hospitalization or an open-label angiotensin-converting enzyme inhibitor.

Survival of patients removed from the heart transplant waiting list

OBJECTIVE

End-stage heart failure has been associated with high mortality in the absence of transplantation. We evaluated the outcome of patients receiving optimal medical therapy who were removed from the cardiac transplant waiting list to determine survival and predictors of mortality.

METHODS

We performed a retrospective review of 27 patients removed from the cardiac transplant waiting list from 1999 to 2001 at our institution.

RESULTS

Mean age was 53 +/- 11 years; 16 of the patients were male. Status was IB in 3 cases and II in 24. Median time on the list was 32 months, and median follow-up was 2.9 years. Patients were removed from the transplant list because of either clinical improvement (group A, n = 18) or deterioration (group B, n = 9). In group A, 13 patients had improved functional status and 10 were in New York Heart Association class 1 or 2; 16 had improved echocardiographic left ventricular function. Survivals at 3 years were 100% in group A and 44% in group B (P <.01).

CONCLUSION

Patients with end-stage heart failure who have clinical response to medical therapy have excellent 3-year survival. These data suggest the necessity of close evaluation of patients waiting for transplantation, with a low threshold for inactivation if persistent clinical improvement is observed.

Timing of cardiac transplantation in patients with heart failure receiving β-adrenergic blockers

BACKGROUND

Previous work shows that patients with heart failure patients who have peak oxygen consumption (VO2 peak) >14 ml/kg/min do not derive a survival benefit from cardiac transplantation. However, this was shown before beta-blocker therapy for patients with systolic heart failure became common, and beta-blockers improve survival in patients with heart failure without changing VO(2) peak. Our purpose was to re-evaluate the utility of VO(2) peak >14 ml/kg/min as an indicator of the need for cardiac transplantation in patients with heart failure who are taking beta-blockers.

METHODS

Actuarial, hemodynamic, and exercise ventilatory data were collected from 540 patients with heart failure, 256 of whom were taking beta-blockers. We tracked death and cardiac transplantation. We stratified the percentage of patients event-free 1 and 3 years after VO(2) peak study by their VO(2) peak and beta-blocker status, and compared 1- and 3-year post-transplant survival (United Network of Organ Sharing [UNOS] data). We also compared total mortality for the patients with heart failure as stratified by beta-blocker stats and VO(2) peak (excluding the 42 who underwent transplantation) with UNOS post-transplant survival.

RESULTS

Patients with heart failure who were receiving beta-blockers and whose VO(2) peak was > or =12 ml/kg/min had greater 1- and 3-year event-free survival rates (95% confidence intervals, 92.6%-96.6% and 85.8%-96.0%) than did post-transplant patients (83.9%-86.3% and 75.4%-76.6%). However, in patients with heart failure not taking beta-blockers, VO(2) peak <14 ml/kg/min was associated with worse 3-year survival (38.9 - 62.1%) than that for post-transplant patients. Excluding the 42 patients with heart failure in our study who underwent transplantation and then evaluating survival of the remaining patients with heart failure (not event-free survival) did not substantially change these results.

CONCLUSIONS

Patients with heart failure who are receiving beta-blockers do not derive a survival advantage at 1 and 3 years after cardiac transplantation if VO(2) peak is > or =12 ml/kg/min. Patients not taking beta-blockers whose VO(2) peak is <14 ml/kg/min have superior survival with cardiac transplantation.

The effect of beta-adrenergic blockers on the prognostic value of peak exercise oxygen uptake in patients with heart failure

OBJECTIVES

Our aim was to determine the effect of beta-adrenergic blockade on the prognostic value of peak oxygen consumption testing in patients with heart failure.

BACKGROUND

Peak oxygen consumption has been shown to be a useful prognostic tool in patients with heart failure. However, studies demonstrating the utility of peak oxygen consumption were conducted before beta-blocker therapy became widespread. Thus, our objective was to determine the effect of beta-blockers on the prognostic value of peak oxygen consumption in patients with heart failure.

METHODS

Actuarial, anthropomorphic, hemodynamic and exercise ventilatory data were collected from 369 patients with heart failure. Death and orthotopic heart transplants were the events tracked. Patients were divided into those taking beta-blockers and those not taking them. Event-free survival days were calculated.

RESULTS

One hundred ninety-nine patients on beta-blockers and 170 not on beta-blockers were studied. There were 40 orthotopic heart transplants and 82 deaths during follow-up. Peak oxygen consumption (milliliters per kilogram per minute) trended toward being an independent predictor of event-free survival (p = 0.055). In patients on and not on beta-blockers, a peak oxygen consumption of >14 ml/kg.min was associated with a 1-year event rate of approximately half of that associated with a peak oxygen consumption </=14 ml/kg x min. However, for every level of peak oxygen consumption, the event rate was lower in the group taking beta-blockers.

CONCLUSIONS

Beta-blocker status does not change the predictive power of peak oxygen consumption in patients with heart failure, but beta-blocker status is important to consider when using peak oxygen consumption to predict event-free survival in patients with heart failure.

Effect of mibefradil, a T-type calcium channel blocker, on morbidity and mortality in moderate to severe congestive heart failure: the MACH-1 study. Mortality Assessment in Congestive Heart Failure Trial

BACKGROUND

Calcium antagonists have proved disappointing in long-term congestive heart failure (CHF) studies. Mibefradil, a new calcium antagonist that selectively blocks T-type calcium channels, has been shown to be an effective antihypertensive, antianginal, and anti-ischemic agent, and because of its different mechanism of action, it may be beneficial as adjunct therapy in CHF patients.

METHODS AND RESULTS

This multicenter, randomized, double-blind study compared mibefradil with placebo as adjunct to usual therapy in 2590 CHF patients (NYHA class II to IV; left ventricular fraction <35%). The initial 50-mg daily dose of mibefradil was uptitrated to 100 mg after 1 month and continued up to 3 years. Patients were monitored at 1 week; 1, 2, and 3 months; and every 3 months thereafter. All-cause mortality, cardiovascular mortality, and cardiovascular morbidity/mortality were analyzed by use of the log-rank test (alpha=0.05). Substudies included exercise tolerance, plasma hormone and cytokines, echocardiography, and quality of life. Total mortality was similar between mibefradil- and placebo-treated patients (P=0.151). The 14% increased risk of mortality with mibefradil in the first 3 months was not statistically significant (P=0.093). Treatment groups had similar cardiovascular mortality (P=0.246), cardiovascular morbidity/mortality (P=0.783), and reasons for death or hospitalization. Patients comedicated with mibefradil and antiarrhythmics (class I or III), including amiodarone, had a significantly increased risk of death. Substudies demonstrated no significant differences between treatments.

CONCLUSIONS

When used as adjunct therapy, mibefradil did not affect the usual outcome of CHF. The potential interaction with antiarrhythmic drugs, especially amiodarone, and drugs associated with torsade de pointes may have contributed to poor outcomes early in the study.

Sphygmomanometrically determined pulse pressure is a powerful independent predictor of recurrent events after myocardial infarction in patients with impaired left ventricular function. SAVE investigators. Survival and Ventricular Enlargement

BACKGROUND

There is increasing evidence of a link between conduit vessel stiffness and cardiovascular events, although the association has never been tested in a large post-myocardial infarction patient population.

METHODS AND RESULTS

We evaluated the relationship between baseline pulse pressure, measured by sphygmomanometry 3 to 16 days after myocardial infarction, and subsequent adverse clinical events in the 2231 patients enrolled in the SAVE Trial. Increased pulse pressure was associated with increased age, left ventricular ejection fraction, female sex, history of prior infarction, diabetes, and hypertension and use of digoxin and calcium channel blockers. Over a 42-month period, there were 503 deaths, 422 cardiovascular deaths, and 303 myocardial infarctions. Pulse pressure was significantly related to each of these end points as a univariate predictor. In a multivariate analysis, pulse pressure remained a significant predictor of total mortality (relative risk, 1.08 per 10 mm Hg increment in pulse pressure; 95% CI, 1.00 to 1.17; P<.05) and recurrent myocardial infarction (relative risk, 1.12; 95% CI, 1.01 to 1.23; P<.05) after control for age; left ventricular ejection fraction; mean arterial pressure; sex; treatment arm (captopril or placebo); smoking history; history of prior myocardial infarction, diabetes, or hypertension; and treatment with beta-blockers, calcium channel blockers, digoxin, aspirin, or thrombolytic therapy.

CONCLUSIONS

These data provide strong evidence for a link between pulse pressure, which is related to conduit vessel stiffness, and subsequent cardiovascular events after myocardial infarction in patients with left ventricular dysfunction.

Superiority of C-11 acetate compared with F-18 fluorodeoxyglucose in predicting myocardial functional recovery by positron emission tomography in patients with acute myocardial infarction

In patients with chronic coronary artery disease, preservation of myocardial oxidative metabolism measured by positron emission tomography (PET) with 11C-acetate is a more accurate predictor of subsequent myocardial functional recovery than is maintenance of glucose metabolism estimated with 18F-fluorodeoxyglucose. However, whether measurements of myocardial oxidative metabolism are more accurate than measurements of glucose metabolism in predicting functional recovery in patients with recent myocardial infarction is unknown. Myocardial oxidative metabolism was measured within 10 days of infarction in 19 patients by analysis of the rate of myocardial clearance of 11C-acetate. Metabolism of glucose was assessed by analysis of the uptake of 18F-fluorodeoxyglucose. Criteria for prediction of the recovery of function based on measurements of oxidative metabolism and glucose metabolism were compared. Threshold criteria with 11C-acetate exhibited superior positive and negative predictive values (89% and 73%, respectively) compared with the criteria of 18F-fluorodeoxyglucose (65% and 57%, respectively) (p <0.025). In addition, the magnitude of functional recovery after revascularization correlated with the severity of the metabolic abnormality present initially. In patients with recent myocardial infarction, the extent of functional recovery can be predicted accurately by measurement of regional oxidative metabolism by PET with 11C-acetate, and these measurements are superior to those of 18-fluorodeoxyglucose.

Comparative sensitivity of cardiac troponin I and lactate dehydrogenase isoenzymes for diagnosing acute myocardial infarction

Criteria for the retrospective diagnosis of acute myocardial infarction rely heavily on increases in lactate dehydrogenase (LD) isoenzymes. However, increases of LD isoenzyme activities are not specific for myocardial injury. Recently, increased concentrations of cardiac troponin I (cTnI) have been shown to be highly specific for myocardial damage and to have sensitivity comparable with that of creatine kinase MB isoenzyme for detecting cardiac injury. Furthermore, increases of cTnI persist in plasma for at least several days. The present study was designed to determine the relative sensitivities of cTnI and LD isoenzymes over time for the diagnosis of infarction. The results indicate that cTnI values are at least as sensitive as LD isoenzymes: 90% of patients with myocardial infarction had above-normal concentrations of cTnI on the 4th day after admission to the coronary care unit. Criteria based on cTnI should improve the accuracy of retrospective diagnoses of acute myocardial infarction.

Comparative sensitivity of cardiac troponin I and lactate dehydrogenase isoenzymes for diagnosing acute myocardial infarction

Criteria for the retrospective diagnosis of acute myocardial infarction rely heavily on increases in lactate dehydrogenase (LD) isoenzymes. However, increases of LD isoenzyme activities are not specific for myocardial injury. Recently, increased concentrations of cardiac troponin I (cTnI) have been shown to be highly specific for myocardial damage and to have sensitivity comparable with that of creatine kinase MB isoenzyme for detecting cardiac injury. Furthermore, increases of cTnI persist in plasma for at least several days. The present study was designed to determine the relative sensitivities of cTnI and LD isoenzymes over time for the diagnosis of infarction. The results indicate that cTnI values are at least as sensitive as LD isoenzymes: 90% of patients with myocardial infarction had above-normal concentrations of cTnI on the 4th day after admission to the coronary care unit. Criteria based on cTnI should improve the accuracy of retrospective diagnoses of acute myocardial infarction.

The role of transthoracic echocardiography in the management of patients seen in an outpatient cardiology clinic

Transthoracic two-dimensional (2D) Doppler echocardiography may provide new or additional information in patients, but it is often not known whether the results alter the treatment plan. We investigated whether results of clinically indicated 2D echocardiography were different from the physician's clinical examination or led to changes in management in 200 consecutive outpatients seen in a university-based clinic. A questionnaire was completed by the physician regarding physical findings and treatment plan before 2D echocardiography was performed. After results were known, the physician was asked to report any differences compared with clinical examination or changes in patient management. Most patients (83%) were studied to evaluate left ventricular (LV) or valvular function. 2D echocardiography confirmed clinical assessment in 182 patients (one inadequate 2D echocardiogram) and disclosed a new diagnosis in 17. 2D echocardiography provided additional information, not expected from clinical assessment or history, in 94 patients. Clinical assessment, compared with 2D echocardiography, was concordant in 154 (77%) of 199 patients with regard to LV systolic function but in only 22 (50%) of 44 with valve disease. Alterations in management based on results of 2D echocardiography were instituted in 73 patients (36%), most often manifested by changes in pharmacologic therapy (n = 45; 62%). Results of 2D echocardiography obviated the need for further cardiac evaluation, surgery, or procedures in 30 patients, avoiding additional patient charges of $125,754.00. In contrast, results of 2D echocardiography led to the need for further evaluation, surgery, or procedures in 32 patients, resulting in additional patient charges of $70,860.00. In conclusion, 2D echocardiography provides new or additional information that results in changes in management strategy in one third of patients, and 2D echocardiography offers relative cost savings by avoiding additional procedures.

Delineation of myocardial stunning and hibernation by positron emission tomography in advanced coronary artery disease

With positron emission tomography, the resting flow abnormalities underlying reversible left ventricular dysfunction in 17 patients with chronic coronary artery disease were delineated. The level of flow in reversible dysfuncTional segments (i.e., those demonstrating improvement after revascularization) was markedly variable, ranging from 0.32 to 1.25 ml/gm/min. In 20 of these segments, flow was preserved, whereas in 12 segments, flow was reduced, when compared with that in, age-matched controls. Preservation of flow was associated with preservation of myocardial oxygen consumption and no alterations in myocardial substrate use. In contrast, a reduction in flow resulted in a decrease myocardial oxygen consumption and an increase in myocardial glucose use. Thus resting reversible left ventricular dysfunction in patients with chronic coronary artery disease can reflect a diversity of resting flow abnormalities. Moreover, myocardial perfusion at rest is frequently within normal limits, suggesting that the reversible mechanical dysfunction in these patients is attributable to intermittent myocardial stunning and not hibernation.

Assessment of myocardial fatty acid metabolism with 1-11C-palmitate

The myocardium has the capacity to utilize a variety of metabolic substrates, including long-chain fatty acids, ketone bodies, glucose, lactate, and amino acids. Under most conditions long-chain fatty acids constitute the major myocardial energy source. Imaging of long-chain fatty acids can be accomplished with carbon 11-labeled palmitate (1-11C-palmitate) and positron emission tomography. Imaging can be performed in either static or dynamic modes. In normal subjects accumulation of the tracer is homogeneous throughout the heart. In patients with myocardial infarction, distinct defects in accumulation are seen. In dilated cardiomyopathy, uptake is spatially heterogeneous. Clearance of 1-11C-palmitate in normal myocardium is biexponential and homogeneous throughout the heart. Administration of glucose, or feeding, decreases uptake of the tracer into the early rapid turnover pool and decreases clearance of the tracer from that pool. In normal myocardium atrial pacing increases the rate of clearance; in ischemic myocardium the degree of increased clearance is attenuated. In patients with cardiomyopathy caused by long-chain fatty acid coenzyme A dehydrogenase deficiency, 1-11C-palmitate clearance is diminished compared with total myocardial oxygen consumption traced with carbon 11-labeled acetate. Thus positron emission tomography with 1-11C-palmitate permits assessment of patients with ischemic heart disease and cardiomyopathy of diverse causes, providing insights into both pathophysiologic mechanisms and the effectiveness of various therapeutic interventions.

Comparison of carbon-11-acetate with fluorine-18-fluorodeoxyglucose for delineating viable myocardium by positron emission tomography

OBJECTIVES

This study was designed to determine in patients with advanced coronary disease whether prediction of recovery of mechanical function after coronary revascularization could be accomplished more effectively by positron emission tomography (PET) with carbon-11 (11C)-acetate than by PET with fluorine-18 (18F)-fluorodeoxyglucose.

BACKGROUND

Results of previous studies have demonstrated that preservation of myocardial oxidative metabolism (measured by PET with 11C-acetate) is necessary for recovery of systolic function after coronary revascularization.

METHODS

Myocardial oxidative metabolism was quantified before revascularization in 34 patients by the analysis of the rate of myocardial clearance of 11C-acetate. Metabolism of glucose was assessed by analysis of uptake of 18F-fluorodeoxyglucose. Receiver operating characteristic curves for predicting functional recovery were derived for the measurements of oxidative metabolism and glucose metabolism. In addition, criteria for prediction of recovery of function based on measurements of oxidative metabolism and glucose metabolism were developed and compared.

RESULTS

Analysis of receiver operating characteristic curves indicated that estimates of oxidative metabolism were more robust in predicting functional recovery than were estimates of glucose metabolism (p < 0.02). Moreover, threshold criteria with 11C-acetate exhibited superior positive and negative predictive values (67% and 89%, respectively) than did the criteria with 18F-fluorodeoxyglucose (52% and 81%, respectively), p < 0.01. In segments with initially severe dysfunction, estimates of oxidative metabolism tended to be more robust than estimates of glucose metabolism in predicting functional recovery. Moreover, in such segments, the threshold criteria with 11C-acetate tended to exhibit superior positive and negative predictive values (85% and 87%, respectively) than did the criteria with 18F-fluorodeoxyglucose (72% and 82%, respectively), although statistical significance was not achieved.

CONCLUSIONS

In patients with advanced coronary artery disease, the extent to which functional recovery can be anticipated after coronary revascularization can be delineated accurately by quantification of regional oxidative metabolism by PET with 11C-acetate.

A comparison of management patterns after acute myocardial infarction in Canada and the United States. The SAVE investigators

BACKGROUND

There are major differences in the organization of the health care systems in Canada and the United States. We hypothesized that these differences may be accompanied by differences in patient care.

METHODS

To test our hypothesis, we compared the treatment patterns for patients with acute myocardial infarction in 19 Canadian and 93 United States hospitals participating in the Survival and Ventricular Enlargement (SAVE) study, which tested the effectiveness of captopril in this population of patients after a myocardial infarction.

RESULTS

In Canada, 51 percent of the patients admitted to a participating coronary care unit had acute myocardial infarctions, as compared with only 35 percent in the United States (P < 0.001). Despite the similar clinical characteristics of the 1573 U.S. patients and 658 Canadian patients participating in the study, coronary arteriography was more commonly performed in the United States than in Canada (in 68 percent vs. 35 percent, P < 0.001), as were revascularization procedures before randomization (31 percent vs. 12 percent, P < 0.001). During an average follow-up of 42 months, these procedures were also performed more commonly in the United States than in Canada. These differences were not associated with any apparent difference in mortality (22 percent in Canada and 23 percent in the United States) or rate of reinfarction (14 percent in Canada and 13 percent in the United States), but there was a higher incidence of activity-limiting angina in Canada than in the United States (33 percent vs. 27 percent, P < 0.007).

CONCLUSIONS

The threshold for the admission of patients to a coronary care unit or for the use of invasive diagnostic and therapeutic interventions in the early and late periods after an infarction is higher in Canada than in the United States. This is not associated with any apparent difference in the rate of reinfarction or survival, but is associated with a higher frequency of activity-limiting angina.

Dobutamine stress echocardiography predicts surgical outcome in patients with an aortic aneurysm and peripheral vascular disease

OBJECTIVES

This study was conducted to assess the utility of dobutamine stress echocardiography for determining the presence of significant coronary artery disease and for predicting surgical outcome and long-term prognosis in patients scheduled to undergo peripheral vascular or aortic aneurysm surgery.

BACKGROUND

Assessment of coronary artery disease in patients scheduled to undergo peripheral vascular surgery can avoid perioperative complications.

METHODS

Dobutamine stress echocardiography was performed in 98 consecutive patients scheduled to undergo aortic or peripheral vascular surgery. Intravenous dobutamine was infused in a graded fashion, with two-dimensional digital echocardiographic monitoring of ventricular function and segmental wall motion. Group 1 (n = 70) consisted of patients who exhibited a normal response to dobutamine infusion (negative dobutamine study); group 2 (n = 23) comprised those patients with an abnormal response to dobutamine, characterized by the development of new or worsening wall motion abnormalities at rest, indicating the presence of myocardial ischemia (positive dobutamine study). Five patients with an inconclusive dobutamine study (because of inadequate heart rate) were excluded from analysis.

RESULTS

No major adverse effects occurred with testing in any patient. Sixty-eight of 70 patients with a negative study had peripheral vascular or aortic surgery performed without perioperative cardiac events (2 patients refused surgery). Nineteen of 23 patients with a positive study underwent coronary angiography and all had > 50% lumen narrowing in one or more major coronary artery distributions; 13 underwent coronary artery bypass grafting or angioplasty before peripheral vascular or aortic surgery and all had an uneventful perioperative period. Four of the 10 patients from group 2 who did not undergo coronary revascularization had a perioperative cardiac event (myocardial infarction in 2, an ischemic episode requiring urgent coronary bypass grafting in 1 and congestive heart failure in 1).

CONCLUSIONS

Positive and negative dobutamine study results are significant predictors of the presence or absence of perioperative events (20% vs. 0%, p = 0.003). A positive test warrants coronary angiography and further medical or surgical intervention, or both, but a negative test indicates a low likelihood of perioperative cardiac complications of aortic or peripheral vascular surgery. During the long-term follow-up period in this study (group 1 mean, 24 months; group 2 mean, 15 months), two patients (3%) from group 1 and three (15%) from group 2 developed cardiac complications (p = 0.038). Thus, dobutamine stress echocardiography is safe and can predict surgical outcome in patients undergoing aortic aneurysm repair or surgery for occlusive disease of the peripheral arteries. In addition, a negative test result is a strong predictor of decreased perioperative and long-term cardiac morbidity and mortality.

Persistence of coronary vasodilator responsivity after cardiac transplantation

Accelerated graft atherosclerosis is a major cause of death after cardiac transplantation. Although its detection currently requires surveillance angiography, loss of vasodilator responsivity may precede obstructive lesions and be detectable by noninvasive assessment of myocardial perfusion. Thirty-five allograft recipients were studied an average of 31 +/- 19 (mean +/- SD) months after transplantation. All were free from angiographically definable macrovascular obstructive coronary artery lesions. Nutritive myocardial perfusion at rest, estimated in absolute terms by positron emission tomography with oxygen-15 water averaged 1.63 +/- 0.51 ml/g/min in patients and was greater than that in 26 healthy volunteers (1.17 +/- 0.33 ml/g/min, p < 0.001). The increase correlated with increased cardiac work at rest in transplant recipients with arterial hypertension and tachycardia. Peak myocardial perfusion induced by intravenous administration of dipyridamole was normal in the transplant recipients (3.49 +/- 1.70 ml/g/min compared with 3.60 +/- 1.41 ml/g/min in volunteers). Because of the high flow at rest, myocardial perfusion reserve (the ratio of hyperemic flow to flow at rest) was diminished (2.3 +/- 1.2 compared with 3.3 +/- 1.5 in volunteers, p < 0.005). These results indicate that the responsivity to vasodilator stimulation is well preserved in transplant recipients devoid of macroscopic coronary arterial lesions obviating detection of early vascular dysfunction in individual subjects. Positron emission tomography may be useful, however, in quantifying the magnitude of the increase in flow at rest secondary to increased cardiac work--a potentially remedial cause of accelerated coronary vascular disease induced by high shear force activation of platelets in the coronary bed, and in detecting impaired perfusion once macrovascular vascular disease is extant.

Effect of captopril on mortality and morbidity in patients with left ventricular dysfunction after myocardial infarction. Results of the survival and ventricular enlargement trial. The SAVE Investigators

BACKGROUND

Left ventricular dilatation and dysfunction after myocardial infarction are major predictors of death. In experimental and clinical studies, longterm therapy with the angiotensin-converting--enzyme inhibitor captopril attenuated ventricular dilatation and remodeling. We investigated whether captopril could reduce morbidity and mortality in patients with left ventricular dysfunction after a myocardial infarction.

METHODS

Within 3 to 16 days after myocardial infarction, 2231 patients with ejection fractions of 40 percent or less but without overt heart failure or symptoms of myocardial ischemia were randomly assigned to receive doubleblind treatment with either placebo (1116 patients) or captopril (1115 patients) and were followed for an average of 42 months.

RESULTS

Mortality from all causes was significantly reduced in the captopril group (228 deaths, or 20 percent) as compared with the placebo group (275 deaths, or 25 percent); the reduction in risk was 19 percent (95 percent confidence interval, 3 to 32 percent; P = 0.019). In addition, the incidence of both fatal and nonfatal major cardiovascular events was consistently reduced in the captopril group. The reduction in risk was 21 percent (95 percent confidence interval, 5 to 35 percent; P = 0.014) for death from cardiovascular causes, 37 percent (95 percent confidence interval, 20 to 50 percent; P less than 0.001) for the development of severe heart failure, 22 percent (95 percent confidence interval, 4 to 37 percent; P = 0.019) for congestive heart failure requiring hospitalization, and 25 percent (95 percent confidence interval, 5 to 40 percent; P = 0.015) for recurrent myocardial infarction.

CONCLUSIONS

In patients with asymptomatic left ventricular dysfunction after myocardial infarction, long-term administration of captopril was associated with an improvement in survival and reduced morbidity and mortality due to major cardiovascular events. These benefits were observed in patients who received thrombolytic therapy, aspirin, or beta-blockers, as well as those who did not, suggesting that treatment with captopril leads to additional improvement in outcome among selected survivors of myocardial infarction.

Functional recovery after coronary revascularization for chronic coronary artery disease is dependent on maintenance of oxidative metabolism

OBJECTIVES

This study was performed to define the importance of maintenance of oxidative metabolism as a descriptor and determinant of functional recovery after revascularization in patients with left ventricular dysfunction attributable to chronic coronary artery disease.

BACKGROUND

Although myocardial accumulation of 18F-fluorodeoxyglucose indicates the presence of tissue that is metabolically active, it may not identify those metabolic processes required for restoration of myocardial contractility. Experimental studies suggest that, under conditions of ischemia and reperfusion, maintenance of myocardial oxidative metabolism is an important metabolic determinant of the capacity for functional recovery.

METHODS

In 16 patients positron emission tomography was performed to characterize myocardial perfusion (with H(2)15O), oxidative metabolism (with 11C-acetate) and utilization of glucose (with 18F-fluorodeoxyglucose). Dysfunctional but viable myocardium was differentiated from nonviable myocardium on the basis of assessments of regional function before and after coronary revascularization. To define the importance of coronary revascularization on myocardial perfusion and metabolism, tomography was repeated in 11 patients after revascularization.

RESULTS

Before revascularization, perfusion in 24 dysfunctional but viable myocardial segments and 29 nonviable segments averaged 79% and 74%, respectively, of that in 42 normal myocardial segments (both p less than 0.01). Dysfunctional but viable myocardium exhibited oxidative metabolism comparable to that in normal myocardium. In contrast, in nonviable myocardium, oxidative metabolism was only 66% of that in normal (p less than 0.01) and 69% of that in reversibly dysfunctional myocardium (p less than 0.003). Regional utilization of glucose normalized to regional perfusion in dysfunctional but viable myocardium was greater than that in normal myocardium (p less than 0.01). However, in both reversibly and persistently dysfunctional myocardium, utilization of glucose normalized to relative perfusion was markedly variable.

CONCLUSIONS

The results indicate that preservation of oxidative metabolism is a necessary condition for recovery of function after coronary recanalization in patients with chronic coronary artery disease. Consequently, approaches that measure myocardial oxygen consumption, such as dynamic positron emission tomography with 11C-acetate, should facilitate the identification of those patients most likely to benefit from coronary revascularization.

Dependence of recovery of contractile function on maintenance of oxidative metabolism after myocardial infarction

This study was performed to define the importance of maintenance of oxidative metabolism as a descriptor and determinant of the potential for functional recovery after revascularization in patients with recent myocardial infarction. In 11 patients (mean interval after infarction 6 days; 5 patients given thrombolytic therapy), positron emission tomography (PET) was performed to characterize myocardial perfusion (with oxygen-15-labeled water), glucose utilization (with fluorine-18-fluorodeoxyglucose) and oxidative metabolism (with carbon-11-acetate). Dysfunctional but viable myocardium was differentiated from nonviable myocardium by assessments of regional function before and after coronary revascularization. The impact of coronary revascularization on regional myocardial perfusion and metabolism was assessed in nine patients in whom tomography was repeated after revascularization. Before revascularization, dysfunctional but viable myocardium (19 segments) and nonviable myocardium (10 segments) exhibited relative perfusion equivalent to 74% and 63% of that of normal myocardium (33 segments), respectively (p less than 0.02). Dysfunctional but viable myocardium exhibited oxidative metabolism equivalent to 74% of that of normal myocardium (p less than 0.02). In contrast, in nonviable myocardium, oxidative metabolism was only 45% of that seen in normal (p less than 0.02) and 60% of that in reversibly dysfunctional myocardium (p less than 0.003). Regional glucose utilization (normalized to regional perfusion) in dysfunctional but viable myocardium was higher than that in normal myocardium (p less than 0.02). Nonviable myocardium exhibited lower levels of glucose utilization than did normal tissue (p less than 0.02). However, in both reversibly and persistently dysfunctional myocardium utilization of glucose normalized to relative perfusion was markedly variable.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive delineation of the effects of moderate aging on myocardial perfusion

Aging is accompanied by a decline in many aspects of cardiovascular function but little is known regarding its influence on myocardial perfusion. Eleven young adults (mean age 25 +/- 4 (s.d.) yr) and 15 older adults (mean age 55 +/- 9 yr) without history or symptoms of cardiovascular disease were studied using H2 15O and positron emission tomography under resting conditions and following administration of intravenous dipyridamole. Myocardial perfusion at rest was similar in the older and younger subjects, averaging 1.17 +/- 0.35 and 1.16 +/- 0.32 ml/g/min, respectively (p = ns). Following dipyridamole, peak myocardial perfusion was blunted in the older subjects, averaging 3.12 +/- 1.09 ml/g/min compared with 4.25 +/- 1.54 ml/g/min in the young adults (p = 0.044). Accordingly, present standards for normal perfusion responses to intravenous dipyridamole may require adjustment for age.

Metabolic imaging of patients with cardiomyopathy

The cardiomyopathies comprise a diverse group of illnesses that can be characterized functionally by several techniques. However, the delineation of derangements of regional perfusion and metabolism have been accomplished only relatively recently with positron emission tomography (PET). Regional myocardial accumulation and clearance of 11C-palmitate, the primary myocardial substrate under most conditions, demonstrate marked spatial heterogeneity when studied under fasting conditions or with glucose loading. PET with 11C-palmitate permits the noninvasive differentiation of patients with nonischemic from ischemic dilated cardiomyopathy, since patients with ischemic cardiomyopathy demonstrate large zones of intensely depressed accumulation of 11C-palmitate, probably reflecting prior infarction. Patients with hypertrophic cardiomyopathy and Duchenne's muscular dystrophy demonstrate relatively unique patterns of myocardial abnormalities of perfusion and metabolism. The availability of new tracers and techniques for the evaluation of myocardial metabolism (11C-acetate), perfusion (H2(15)O), and autonomic tone (11-C-hydroxyephedrine) should facilitate further understanding of the pathogenesis of the cardiomyopathies.

Sex differences in the management of coronary artery disease. Survival and Ventricular Enlargement Investigators

BACKGROUND

Despite the fact that coronary artery disease is the leading cause of death among women, previous studies have suggested that physicians are less likely to pursue an aggressive approach to coronary artery disease in women than in men. To define this issue further, we compared the care previously received by men and women who were enrolled in a large postinfarction intervention trial.

METHODS

We assessed the nature and severity of anginal symptoms and the use of antianginal and antiischemic interventions before enrollment in the 1842 men and 389 women with left ventricular ejection fractions less than or equal to 40 percent after an acute myocardial infarction who were randomized in the Survival and Ventricular Enlargement trial.

RESULTS

Before their index infarction, women were as likely as men to have had angina and to have been treated with antianginal drugs. However, despite reports by women of symptoms consistent with greater functional disability from angina, fewer women had undergone cardiac catheterization (15.4 percent of women vs. 27.3 percent of men, P less than 0.001) or coronary bypass surgery (5.9 percent of women vs. 12.7 percent of men, P less than 0.001). When these differences were adjusted for important covariates, men were still twice as likely to undergo an invasive cardiac procedure as women, but bypass surgery was performed with equal frequency among the men and women who did undergo cardiac catheterization.

CONCLUSIONS

Physicians pursue a less aggressive management approach to coronary disease in women than in men, despite greater cardiac disability in women.

Selection bias in the use of thrombolytic therapy in acute myocardial infarction. The SAVE Investigators

OBJECTIVE

To determine whether clinical selection for thrombolytic therapy for acute myocardial infarction results in a skewed population for subsequent adverse cardiovascular events.

DESIGN

A comparison of the clinical features of the patients in the Survival and Ventricular Enlargement Study who either had or had not received thrombolytic therapy was conducted in both univariate and multiple logistic regression analyses.

SETTING

Hospitalized patients experiencing acute myocardial infarction from 112 broadly representative, private, academic, and government hospitals in the United States and Canada.

PATIENTS

All patients in the Survival and Ventricular Enlargement Study had had a recent myocardial infarction (less than 16 days) and had a left ventricular ejection fraction of 40% or less.

INTERVENTION

Thrombolytic therapy was administered to 733 patients and was not given to 1498.

MAIN OUTCOME MEASURES

The comparisons with respect to use of thrombolytic therapy were formulated after the completion of enrollment and indicated that the majority of patients did not receive thrombolytic therapy.

RESULTS

The 1498 (67.1%) patients who did not receive thrombolytic therapy were at higher risk (older age, lower functional capacity, greater likelihood of a history of prior myocardial infarction, angina, diabetes, and hypertension) for subsequent cardiovascular events and, as anticipated, were more likely to have concomitant gastrointestinal and neurological diseases. A multiple logistic regression analysis indicated that older age, prior myocardial infarction, impaired functional status, employment status, diabetes, and neurological diseases were predictors of use of thrombolytic therapy.

CONCLUSION

Although the Survival and Ventricular Enlargement Study population was selected for left ventricular dysfunction, the majority of patients who currently are judged clinically as unsuitable for thrombolytic therapy have a higher risk for adverse cardiovascular events.

Myocardial uptake of carbon-11-acetate as an indirect estimate of regional myocardial blood flow

The rate of clearance of myocardial carbon-11 (11C) activity (after the administration of 11C-acetate) has been shown to correlate closely with myocardial oxygen consumption. In the present study, we hypothesized that regional net myocardial uptake of 11C-acetate, which reflects primarily delivery and extraction of tracer, would be markedly flow-dependent and potentially useful as an indirect index of regional myocardial blood flow. In 22 patients with stable coronary artery disease, the regional distribution of early net uptake of 11C-acetate was correlated with estimates of regional myocardial blood flow assessed with oxygen-15-water. The myocardial images of 11C-acetate uptake were of high quality. The correlation between the two approaches was close (r = 0.88) and not affected by the metabolic state of the tissue. Thus, in patients with stable coronary artery disease, under resting conditions, direct estimates of myocardial oxygen consumption in relation to the level of delivery of tracer to the tissue can now be obtained by PET with use of a single radiopharmaceutical, 11C-acetate. This approach may prove particularly useful in streamlining clinical protocols designed to assess myocardial oxygen consumption.

Three-dimensional functional images of myocardial oxygen consumption from positron tomography

Images from positron emission tomography (PET) are usually presented as transaxial slices portraying tissue radioactivity. Studies can be difficult to interpret from transaxial images, and the temporal changes in tissue tracer concentrations which permit quantitative determinations of metabolism and perfusion are not displayed. We have developed a method to give quantitatively accurate three-dimensional images of myocardial oxygen consumption from serial images of the myocardial washout of carbon-11-acetate. Following i.v. bolus injection, data are collected for 20-30 min. The time-activity curves for each pixel in the transaxial slices are fit to a monoexponential function to determine the washout rate, which is directly related to the rate of myocardial oxygen utilization. Thus, functional images of myocardial oxygen consumption are produced for all seven slices of PET data. A previously developed method is then used to generate realistic and quantitatively accurate three-dimensional images.

Nonuniformity in myocardial accumulation of fluorine-18-fluorodeoxyglucose in normal fasted humans

In initial studies using fluorine-18-fluorodeoxyglucose (FDG) in normal fasted subjects, we observed disparities in the regional myocardial accumulation of this tracer. Accordingly, we systematically evaluated regional myocardial FDG accumulation in comparison with regional myocardial perfusion assessed with oxygen-15-water and oxidative metabolism assessed with carbon-11-acetate in nine normal subjects (four studied after a 5-hr fast and five studied both fasted and following glucose loading). Under fasting conditions, myocardial accumulation of FDG in the septum and anterior wall averaged 80% of that in the lateral and posterior walls (p less than 0.03). In contrast, after glucose loading the regional distribution of myocardial FDG accumulation became more homogeneous. Regional myocardial perfusion, oxidative metabolism, and accumulation of carbon-11-acetate were homogeneous under both conditions. Thus, under fasting conditions there are regional variations in myocardial accumulation of FDG, which are visually apparent, are not associated with concomitant changes in oxidative metabolism or perfusion, and cannot be attributed to partial-volume effects. This significant heterogeneity may limit the specificity of PET with FDG for detecting myocardial ischemia in fasting subjects.

Increased myocardial perfusion at rest and diminished perfusion reserve in patients with angina and angiographically normal coronary arteries

Angiographically normal coronary arteries are found in a substantial number of patients evaluated for angina pectoris. One third to one half of such patients demonstrate abnormalities of myocardial perfusion or metabolism when evaluated with invasive techniques. This study was designed to determine whether angina in such patients is attributable to abnormalities of perfusion at rest, maximal perfusion or vasodilator reserve and whether any identified abnormalities were global or regional in nature. Positron emission tomography was performed with oxygen-15-labeled water (H2(15)O) and oxygen-15-labeled carbon monoxide (C15O) before and after intravenous dipyridamole to assess regional myocardial perfusion and perfusion reserve in absolute terms in 16 normal subjects and 17 patients with chest pain and angiographically normal coronary arteries. Eight of the 17 patients had a myocardial perfusion reserve less than 2.5 (the lower limit of normal in studies with positron emission tomography, as well as with other techniques) and 9 of 17 patients had a normal response. In the patients with an impaired perfusion reserve, perfusion at rest was significantly higher than that measured in normal subjects (1.61 +/- 0.38 versus 1.25 +/- 0.28 ml/g per min, p less than 0.02) and maximal flow and perfusion reserve were significantly reduced (2.26 +/- 0.92 versus 4.62 +/- 1.58 ml/g per min and 1.4 +/- 0.5 versus 3.8 +/- 1.1, respectively; p less than 0.001 for both comparisons). Abnormalities of perfusion and perfusion reserve were spatially homogeneous without detectable regional disparities. Thus, nearly half of patients with chest pain and normal coronary arteries have abnormalities of myocardial perfusion that are detectable noninvasively with positron emission tomography and H2(15)O.

Augmented myocardial perfusion reserve after coronary angioplasty quantified by positron emission tomography with H2(15)O

Effects of coronary angioplasty on myocardial flow reserve have been difficult to characterize noninvasively because conventional imaging techniques cannot quantitate blood flow in absolute terms. The effects of coronary angioplasty on myocardial perfusion and perfusion reserve were delineated with positron emission tomography and oxygen-15-labeled water (H2(15)O) in 13 patients before and after single vessel angioplasty. In 11 patients, angioplasty was successful (minimal cross-sectional area increased from 0.60 +/- 0.59 to 3.45 +/- 1.09 mm2, p less than 0.001). In these patients, regional H2(15)O radioactivity (the ratio of nutritional perfusion in regions distal to the stenosis compared with regions supplied by angiographically normal arteries) at rest before angioplasty was 55 +/- 22% of peak myocardial radioactivity and did not increase significantly afterward (70 +/- 16%, p = NS). However, after administration of intravenous dipyridamole, hyperemic perfusion in regions distal to a stenosis averaged only 39 +/- 18% of peak myocardial counts before angioplasty, but increased to 66 +/- 22% after angioplasty (p less than 0.02). Perfusion reserve in the two patients in whom angioplasty was angiographically unsuccessful showed no change. Quantitative estimates of perfusion in absolute rather than relative terms were obtained with positron emission tomographic data from seven of the patients with successful angioplasty. At rest, perfusion in regions distal to a stenosis was not different from the values in regions supplied by normal coronary arteries (1.54 +/- 0.54 compared with 1.46 +/- 0.38 ml/g per min, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Mild heart failure: diagnosis and treatment

CHF afflicts 15 million persons worldwide despite advances made in its diagnosis and treatment. A thorough physical examination and basic, noninvasive evaluation are essential for establishing the diagnosis of heart failure and for designing an optimal, individualized treatment regimen. Although digitalis and diuretics continue to be used commonly for the treatment of CHF of all severities, the use of vasodilators and ACE inhibitors has increased dramatically, as they are used more widely and earlier in the course of the illness. Because the RAA system contributes significantly to the altered cardiovascular hemodynamics and symptomatology characteristic of heart failure, the ACE inhibitors provide a rational approach to therapy for many patients. Results of controlled clinical trials have shown that selected vasodilators and ACE inhibitors can improve survival in patients with CHF and that patients receiving ACE inhibitors show sustained improvement in clinical class, exercise tolerance, and hemodynamics. Thus the therapeutic spectrum available to the clinician dealing with patients with CHF has broadened substantively over the past decade.

Noninvasive estimation of regional myocardial oxygen consumption by positron emission tomography with carbon-11 acetate in patients with myocardial infarction

We previously demonstrated in experimental studies that myocardial oxygen consumption (MVO2) can be estimated noninvasively with positron emission tomography (PET) from analysis of the myocardial turnover rate constant (k) after administration of carbon-11 (11C) acetate. To determine regional k in healthy human subjects and to estimate alterations in MVO2 accompanying myocardial ischemia, we administered [11C]acetate to five healthy human volunteers and to six patients with myocardial infarction. Extraction of [11C]acetate by the myocardium was avid and clearance from the blood-pool rapid yielding myocardial images of excellent quality. Regional k was homogeneous in myocardium of healthy volunteers (coefficient variation = 11%). In patients, k in regions remote from the area of infarction was not different from values in myocardium of healthy human volunteers (0.061 +/- 0.025 compared with 0.057 +/- 0.008 min-1). In contrast, MVO2 in the center of the infarct region was only 6% of that in remote regions (p less than 0.01). In four patients studied within 48 hr of infarction and again more than seven days after the acute event, regional k and MVO2 did not change. The approach developed should facilitate evaluation of the efficacy of interventions designed to enhance recovery of jeopardized myocardium and permit estimation of regional MVO2 and metabolic reserve underlying cardiac disease of diverse etiologies.

Assessment of myocardial oxidative metabolic reserve with positron emission tomography and carbon-11 acetate

We have previously demonstrated that positron emission tomography (PET) with [11C]acetate allows noninvasive regional quantification of myocardial oxidative metabolism. To assess the metabolic response of normal myocardium to increased work (oxidative metabolic reserve), clearance of myocardial 11C activity after administration of [11C]acetate i.v. was measured with PET in seven normal subjects at rest and during dobutamine infusion. At rest, clearance of 11C was monoexponential and homogeneous. The rate constant of the first phase of 11C clearance, k1, averaged 0.054 +/- 0.014 min-1 at a rate-pressure produce (RPP) of 7329 +/- 1445 mmHg X bpm. During dobutamine infusion, RPP increased by an average of 141% to 17,493 +/- 3582 mm Hg Z bpm. Clearance of 11C became biexponential and remained homogeneous. k1 averaged 0.198 +/- 0.043 min-1 with a mean coefficient of variation of 16%.. k1 and RPP correlated closely (r = 0.91; p less than 0.001), and the slope of the k1/RPP relation remained consistent in all subjects (1.48 +/- 0.42). These findings suggest that PET with [11C]acetate and dobutamine stress may provide a promising approach for evaluation of regional myocardial oxidative metabolic reserve in patients with cardiac diseases of diverse etiologies and for assessment of the efficacy of interventions designed to enhance the recovery of metabolically comprised myocardium.

Enzymatic estimation of the extent of irreversible myocardial injury early after reperfusion

To determine whether the extent of infarction can be estimated enzymatically soon after reperfusion, the rate of increase of creatine kinase (CK) activity in plasma early after coronary recanalization was compared with infarct size in 18 dogs and 10 patients. In dogs, reperfusion was initiated 2 to 4 hours after coronary occlusion. CK activity was measured in serial plasma samples and infarct size was assessed histochemically at 24 hours. A substantial and consistent fraction of the total CK appearing in plasma over 24 hours (cumulative CK) appeared in plasma soon after reperfusion, i.e., 21 +/- 2% (SE) within 30 minutes and 38 +/- 3% within 1 hour. The rate of increase of plasma CK activity correlated closely with infarct size when CK release was measured during the first 30 minutes (r = 0.92) or 60 minutes (r = 0.92) after reperfusion (n = 18). Similarly, in patients the rate of increase of CK activity measured within 2.5 hours of the time of reperfusion was closely related to infarct size delineated by positron emission tomography 1 to 2 weeks later (r = 0.93). Thus the rate of appearance of CK in plasma early after reperfusion reflects the extent of irreversible injury ultimately sustained and provides a criterion likely to be useful for prospective identification of patients at high risk after coronary recanalization.