Studies on ergometer exercise testing. II. Effect of previous myocardial infarction, digoxin, and beta-blockade on exercise electrocardiography

Chest Pain Units: Management of Special Populations

Chest pain units provide an important alternative to traditional hospital admission for patients who present to the emergency department with symptoms compatible with acute coronary syndrome and a normal or inconclusive initial evaluation. Although patient subgroups such as women, diabetics, those with established coronary artery disease,and those with symptoms related to stimulant use present unique challenges,management in a chest pain unit appears to be appropriate in these populations. Judicious application of accelerated diagnostic protocols and current testing methods can promote safe, accurate, and cost-effective risk stratification of special populations to identify patients who can be safely discharged and patients who require hospital admission for further evaluation.

A new criterion combining ST/HR slope and deltaST/deltaHR index for detection of coronary artery disease in patients on digoxin therapy

We evaluated the clinical value of a new index combining deltaST/delta heart rate (HR) index and ST/HR slope for diagnosing coronary artery disease (CAD) in patients on digoxin therapy. Exercise treadmill tests were performed by 72 patients on digoxin therapy. Simple HR-adjusted indexes of ST-segment depression during exercise (deltaST/deltaHR index) and the decline calculated from the final 12 data points relating ST-segment depression to HR (ST/HR slope) were determined. A new index was obtained by subtracting the deltaST/deltaHR index from the ST/HR slope. On thallium scintigraphy, 37 of the 72 patients showed reversible perfusion defects related to the diseased coronary artery. The new index derived from this ST-HR relation was 4.1 +/- 3.6 microV/beats/min in the ischemic group and 1.3 +/- 1.0 microV/beats/min in the group of patients without ischemia (p <0.0001). An ST-HR relation > or = 1.5 was found in 33 of the 37 patients in the ischemic group, and in 7 of the 35 patients without ischemia (p <0.0001). The sensitivity of this criterion for prediction of myocardial ischemia was 89%, the specificity was 80%, and the predictive accuracy was 85%. Thus, this new ST-HR index is useful for detecting CAD in patients on digoxin therapy.

Effects of digitalis, anti-anginal drugs and arterial hypertension on the relationships between exercise ECG and angiocardiographic variables and on the diagnostic accuracy of exercise ECG in patients with coronary heart disease

We have previously found a statistically significant correlation between some exercise ECG variables and angiocardiographic scores used to evaluate the extent and type of coronary heart disease (CHD). In the present study we examined the effects of digitalis, beta-adrenergic blockers, slow release nitrates, calcium channel blockers, presence of arterial hypertension (AHT), and angiocardiographic changes on the exercise ECG variables. The effects of drugs and AHT were small as compared to the effects of the angiocardiographically detected pathological changes caused by the CHD. Sensitivity and specificity of the exercise ECG ST criteria in identifying patients with an angiocardiographic criterion indicating coronary insufficiency were not much different in the whole group and in the subsets with AHT or medication with digitalis and anti-anginal drugs.

Relationships between exercise ECG and angiocardiographic indices of coronary insufficiency and myocardial fibrosis in coronary heart disease

Patients with coronary heart disease were examined with exercise ECG and angiocardiography. Maximum work capacity expressed as a percentage of the predicted normal exercise tolerance (Wmax%) was significantly associated with the angiocardiographic score of the myocardial mass subserved by obstructed coronary arteries (MCOS). Variables related to myocardial fibrosis (MF) such as post infarction ECG signs, the left ventricular wall motion score (LVMS) and the ejection fraction of the left ventricle (LVEF) correlated significantly as did variables related to reversible myocardial ischaemia or coronary insufficiency (CI), such as ST depression during exercise (STdepr), ST/W and ST/HR indices, effort angina (EA/W) index, the extent of collaterals (CollS), and 'MCOS-LVMS'. MF variables correlated weakly with CI variables. Wmax% covariated with the variables related to both CI and MF, and most closely with MCOS. Discrepancies between results of exercise ECG and angiocardiography have to some extent been overcome by comparing appropriate parameters.