James R. Bengtson

Prognostic Value of a Treadmill Exercise Score in Outpatients with Suspected Coronary Artery Disease

BACKGROUND The treadmill exercise test identifies patients with different degrees of risk of death from cardiovascular events. We devised a prognostic score, based on the results of treadmill exercise testing, that accurately predicts outcome among inpatients referred for cardiac catheterization. This study was designed to determine whether this score could also accurately predict prognosis in unselected outpatients. METHODS We prospectively studied 613 consecutive outpatients with suspected coronary disease who were referred for exercise testing between 1983 and 1985. Follow-up was 98 percent complete at four years. The treadmill score was calculated as follows: duration of exercise in minutes--(5 x the maximal ST-segment deviation during or after exercise, in millimeters)--(4 x the treadmill angina index). The numerical treadmill angina index was 0 for no angina, 1 for nonlimiting angina, and 2 for exercise-limiting angina. Treadmill scores ranged from -25 (indicating the highest risk) to +15 (indicating the lowest risk). RESULTS Predicted outcomes for the outpatients, based on their treadmill scores, agreed closely with the observed outcomes. The score accurately separated patients who subsequently died from those who lived for four years (area under the receiver-operating-characteristic curve = 0.849). The treadmill score was a better discriminator than the clinical data and was even more useful for outpatients than it had been for inpatients. Approximately two thirds of the outpatients had treadmill scores indicating low risk (greater than or equal to +5), reflecting longer exercise times and little or no ST-segment deviation, and their four-year survival rate was 99 percent (average annual mortality rate, 0.25 percent). Four percent of the outpatients had scores indicating high risk (less than -10), reflecting shorter exercise times and more severe ST-segment deviation; their four-year survival rate was 79 percent (average annual mortality rate, 5 percent). CONCLUSIONS The treadmill score is a useful and valid tool that can help clinicians determine prognosis and decide whether to refer outpatients with suspected coronary disease for cardiac catheterization. In this study, it was a better predictor of outcome than the clinical assessment.

An improved method for adjusting the QT interval for heart rate (the Framingham Heart Study)

Several formulas have been proposed to adjust the QT interval for heart rate, the most commonly used being the QT correction formula (QTc = QT/square root of RR) proposed in 1920 by Bazett. The QTc formula was derived from observations in only 39 young subjects. Recently, the adequacy of Bazetts formula has been questioned. To evaluate the heart rate QT association, the QT interval was measured on the initial baseline electrocardiogram of 5,018 subjects (2,239 men and 2,779 women) from the Framingham Heart Study with a mean age of 44 years (range 28 to 62). Persons with coronary artery disease were excluded. A linear regression model was developed for correcting QT according to RR cycle length. The large sample allowed for subdivision of the population into sex-specific deciles of RR intervals and for comparison of QT, Bazetts QTc and linear corrected QT (QTLC). The mean RR interval was 0.81 second (range 0.5 to 1.47) heart rate 74 beats/min (range 41 to 120), and mean QT was 0.35 second (range 0.24 to 0.49) in men and 0.36 second (range 0.26 to 0.48) in women. The linear regression model yielded a correction formula (for a reference RR interval of 1 second): QTLC = QT + 0.154 (1-RR) that applies for men and women. This equation corrects QT more reliably than the Bazetts formula, which overcorrects the QT interval at fast heart rates and undercorrects it at low heart rates. Lower and upper limits of normal QT values in relation to RR were generated.(ABSTRACT TRUNCATED AT 250 WORDS)

Restenosis after coronary angioplasty: An overview☆

Despite substantial basic and clinical efforts to address the problem of restenosis after percutaneous coronary intervention, effective preventive therapies have not yet been developed. Nevertheless, the accumulated information has provided much insight into the process of restenosis in addition to allowing standards to be developed for adequate clinical trials. The pathophysiology of restenosis increasingly appears to be distinct from that of primary atherosclerosis. Restenosis involves elastic recoil, incorporation of thrombus into the lesion and fibrocellular proliferation in varying degrees in different patients. Lack of an animal model that satisfactorily mimics restenosis is a major impediment to further understanding of the process. Clinical studies are hampered by difficulties in finding a single unifying definition of restenosis and by variable methods of reporting follow-up. Reporting of clinical outcomes of all patients in angiographic substudies would allow a more satisfactory interpretation of the results of clinical trials. Current noninvasive test results are not accurate enough to substitute for angiographic and clinical outcome data in intervention trials. In the majority of observational studies, only diabetes and unstable angina have emerged as consistently associated with restenosis; whereas most of the standard risk factors for atherosclerosis have a less consistent relation. Disappointingly, the new atherectomy and laser technologies have not affected restenosis rates. The one possible exception is coronary stenting, as a result of the larger luminal diameter achieved by the placement of the stent. In conclusion, although substantial continued effort is necessary to explore the basic aspects of cellular proliferation and mechanical alteration of atherosclerotic vessels, attention to the principles of clinical trials and observation are required to detect the impact of risk factors and interventions on the multifactorial problem of restenosis. Adequate sample sizes, collection of clinical and angiographic outcomes and factorial study designs hold promise for unraveling this important limitation of percutaneous intervention.

Prognosis in cardiogenic shock after acute myocardial infarction in the intervencional era

OBJECTIVES The purpose of this study is to describe the outcome in cardiogenic shock treated with aggressive reperfusion therapy and to identify factors predictive of in-hospital and long-term mortality. BACKGROUND Cardiogenic shock is the most common cause of death in patients admitted to the coronary care unit. Although studies have reported lower mortality rates in shock treated with angioplasty, few studies have described a cohort of patients with shock who were not selected because they were most likely to benefit from reperfusion therapy. METHODS A consecutive series of 200 patients admitted with acute myocardial infarction complicated by cardiogenic shock were studied. RESULTS The in-hospital mortality rate was 53%. Variables with significant univariable association with in-hospital death included patency of the infarct-related artery, patient age, lowest cardiac index, highest arteriovenous oxygen difference and left main coronary artery disease. The most important independent predictors of in-hospital death were patency of the infarct-related artery, cardiac index and peak creatine kinase, MB fraction. The mortality rate in patients with patent infarct-related arteries was 33% versus 75% in those with closed arteries and 84% in those in whom arterial patency was unknown. Patients who survived to hospital discharge were followed up for a median of 2 years, with a mortality rate of 18% after 1 year. The best descriptors of the relation between these variables and postdischarge mortality included age, peak creatine kinase, ejection fraction and patency of the infarct-related artery. CONCLUSIONS In a large consecutive series of patients with cardiogenic shock with complete follow-up, patency of the infarct-related artery was most strongly associated with in-hospital and long-term mortality. This finding supports an aggressive interventional strategy in patients with cardiogenic shock.

DURATION OF THE QT INTERVAL AND TOTAL AND CARDIOVASCULAR MORTALITY IN HEALTHY PERSONS (THE FRAMINGHAM HEART STUDY EXPERIENCE)

The baseline electrocardiograms of 5,125 original subjects of the Framingham Heart Study were measured to examine the relation of the QT interval corrected for heart rate (QTc) to risk of total mortality, sudden cardiac death, and death due to coronary artery disease over a 30-year follow-up period. Quintiles of QTc (seconds) less than or equal to 0.36, 0.36 to 0.38, 0.39 to 0.40, 0.41 to 0.43 and greater than or equal to 0.44 were studied in relation to these outcomes. There were no significant differences in the risk of total mortality, sudden cardiac death or death due to coronary artery disease according to QTc. A similar lack of significant association between QTc and these 3 outcomes was observed among all persons studied and in the 2 sexes after using a multiple regression analysis to control for several potentially confounding characteristics including age, gender, cigarette smoking, serum total cholesterol, systolic systemic blood pressure and Framingham relative weight. The results of this study fail to demonstrate an association between baseline QTc and overall mortality, and deaths due to sudden cardiac events or coronary artery disease in a large population-based cohort of essentially healthy persons in whom pathologic forms of QTc prolongation are uncommon.

Intraoperative transesophageal Doppler color flow imaging used to guide patient selection and operative treatment of ischemic mitral regurgitation.

BackgroundIntraoperative transesophageal Doppler color flow imaging (TDCF) affords the opportunity to assess mitral valve competency immediately before and after cardiopulmonary bypass (CPB). The purpose of this study was to assess the utility of TDCF to assist in the selection and operative treatment of ischemic mitral regurgitation (MR). Methods and ResultsTwo hundred forty-six patients undergoing surgery for ischemic heart disease were prospectively studied. All had preoperative cardiac catheterization. Catheterization and pre-CPB TDCF were discordant in their estimation of MR in 112 patients (46%). Compared with patients in whom both techniques agreed in estimation of MR, patients with discordance in MR were more likely to have had unstable clinical syndromes at the time of catheterization (79% versus 40%, p < 0.05) or to have received thrombolytics (16% versus 8%, p < 0.05). Pre-CPB TDCF resulted in a change in the operative plan with respect to the mitral valve in 27 patients (11%). Because less MR was found by TDCF than catheterization, 22 patients had only coronary bypass grafting when combined coronary bypass and mitral valve surgery had been planned. Because more MR was found by TDCF than catheterization, five patients had combined coronary bypass and mitral valve surgery when coronary bypass alone had been planned. Unsatisfactory results noted by TDCF following mitral valve surgery in five patients resulted in immediate corrective surgery. Cox regression analysis identified residual MR at the completion of surgery to be an important predictor of survival (X2=21.4) after surgery-more important than patient age (X2=8.3) or left ventricular ejection fraction (x2=5.3). ConclusionsThese results indicate that TDCF is useful in guiding patient selection and operative treatment of ischemic MR and that in such patients, intraoperative TDCF should be performed routinely.

Detection of restenosis after elective percutaneous transluminal coronary angioplasty using the exercise treadmill test

To determine the value of a 6-month exercise treadmill test for detecting restenosis after elective percutaneous transluminal coronary angioplasty (PTCA), 303 consecutive patients with successful PTCA and without a recent myocardial infarction were studied. Among the 228 patients without interval cardiac events, early repeat revascularization or contraindications to treadmill testing, 209 (92%) underwent follow-up angiography, and 200 also had a follow-up treadmill test and formed the study population. Restenosis (greater than or equal to 75% luminal diameter stenosis) occurred in 50 patients (25%). Five variables were individually associated with a higher risk of restenosis: recurrent angina (p = 0.0002), exercise-induced angina (p = 0.0001), a positive treadmill test (p = 0.008), more exercise ST deviation (p = 0.04) and a lower maximum exercise heart rate (p = 0.05). However, only exercise-induced angina (p = 0.002), recurrent angina (p = 0.01) and a positive treadmill test (p = 0.04) were independent predictors of restenosis. Using these 3 variables, patient subsets could be identified with restenosis rates ranging from 11 to 83%. The exercise treadmill test added independent information to symptom status about the risk of restenosis after elective PTCA. Nevertheless, 20% of patients with restenosis had neither recurrent angina nor exercise-induced ischemia at follow-up. For more accurate detection of restenosis, the exercise treadmill test must be supplemented by a more definitive test.

Relation of quantitative coronary lesion measurements to the development of exercise-induced ischemia assessed by exercise echocardiography

To assess the relation of quantitative measures of coronary stenoses to the development of exercise-induced regional wall motion abnormalities, 34 patients with isolated, single vessel coronary artery lesions and normal wall motion at rest underwent exercise echocardiography and quantitative angiography on the same day. Although all 11 patients with a visually estimated stenosis greater than or equal to 75% had an ischemic response and 10 (91%) of 11 patients with a less than or equal to 25% visually estimated stenosis had a normal response by exercise echocardiography, among 12 patients with a visually estimated stenosis of 50%, 6 (50%) had an ischemic response and 6 (50%) had a normal exercise echocardiogram. Quantitative measurements of stenosis severity distinguished patients with ischemic (group 1) from normal (group 2) exercise echocardiographic responses as follows: minimal luminal diameter (mm), group 1 1.0 +/- 0.4 versus group 2 1.7 +/- 0.4, p less than 0.0001; minimal cross-sectional area (mm2), group 1 0.9 +/- 0.6 versus group 2 2.5 +/- 1.1, p less than 0.0001; percent diameter stenosis, group 1 68.3 +/- 14.2 versus group 2 42.2 +/- 12.1, p less than 0.0001; and percent area stenosis, group 1 87.5 +/- 7.8 versus group 2 64.8 +/- 15.9, p less than 0.0001. These data validate the utility of exercise echocardiography by demonstrating that 1) coronary stenosis severity measured by quantitative angiography is closely related to wall motion abnormalities detected by exercise echocardiography, and 2) exercise echocardiography can be used as a noninvasive means to assess the physiologic significance of coronary artery lesions.

Exercise treadmill testing is a poor predictor of anatomic restenosis after angioplasty for acute myocardial infarction.

This study evaluated whether an exercise treadmill test could predict restenosis in 289 patients 6 months after a successful emergency angioplasty of the infarct-related artery for acute myocardial infarction. After excluding those with interim interventions (64), medical events (36), or medical contraindications to follow-up testing (25), both a treadmill test and a cardiac catheterization were completed in 144 patients, 88% of those eligible for this assessment. Four patients with left bundle branch block or pacemaker rhythm at the time of treadmill testing were also excluded from analysis. Of six follow-up clinical and treadmill variables examined by multivariable logistic regression analysis, only exercise ST deviation was independently correlated with restenosis at follow-up (chi 2 = 5, p = 0.02). The clinical diagnosis of angina at follow-up, although marginally related to restenosis when considered by itself (p = 0.04), did not add significant information once ST deviation was known. The sensitivity of ST deviation of 0.10 mV or greater for detecting restenosis was only 24% (13 of 55 patients), and the specificity was 88% (75 of 85 patients). The sensitivity of exercise-induced ST deviation for detection of restenosis was not affected by extent or severity of wall motion abnormalities at follow-up, by the timing of thrombolytic therapy or of angioplasty, or by the presence of collateral blood flow at the time of acute angiography. A second multivariable analysis evaluating the association of the same variables with number of vessels with significant coronary disease at the 6-month catheterization found an association with both exercise ST deviation (p = 0.003) and exercise duration (p = 0.04). Angina symptoms and exercise treadmill test results in this population had limited value for predicting anatomic restenosis 6 months after emergency angioplasty for acute myocardial infarction.

Effect of the degree of effort on exercise echocardiography for the detection of restenosis after coronary artery angioplasty.

To determine whether the accuracy of exercise echocardiography is affected by the degree of effort during exercise, we examined 101 patients who had 6 months earlier undergone successful coronary artery angioplasty, with resting and immediate postexercise echocardiography and same-day coronary angiography. A positive exercise echocardiographic response was defined as the development of a new or worsening wall motion abnormality postexercise, compared with resting wall motion. Significant coronary disease (greater than 50% diameter stenosis) was present in 48 patients, 38 of whom had single-vessel disease and 10 of whom had two-vessel disease. Exercise echocardiography correctly identified 32 patients with significant disease (sensitivity 67%) and 44 patients without significant disease (specificity 83%). The effect of the degree of exercise effort on the sensitivity and specificity of the test was evaluated by three criteria; (1) the percentage of maximum predicted heart rate (MHR), (2) the duration of exercise (DUR), and (3) the double product (DP). To determine the influence of the degree of effort upon sensitivity and specificity, the effort criteria were compared between patients with true positive (TP) tests to those with false negative tests (FN), and in patients with true negative (TN) tests compared with those with false positive (FP) tests. No significant differences were detected in MHR, DUR, or DP between TP versus FN patients or between TN versus FP patients. These results indicate that for symptom-limited exercise echocardiography in postangioplasty patients, neither sensitivity nor specificity is significantly affected by the degree of effort during exercise.