Multistage analysis of exercise radionuclide angiography in coronary artery disease

Rate of change of left ventricular ejection fraction during exercise is superior to the peak ejection fraction for predicting functionally significant coronary artery disease

OBJECTIVE

To detect and characterise rapid temporal changes in the left ventricular response to exercise in patients with ischaemic heart disease and to relate these changes to the functional severity of coronary artery disease.

BACKGROUND

The gamma camera does not allow the detection of rapid changes in cardiac function during exercise radionuclide ventriculography, the monitoring of which may improve the assessment of patients with ischaemic heart disease.

METHODS

A miniature nuclear probe (Cardioscint) was used to monitor continuously left ventricular function during exercise in 31 patients who had coronary angiography for suspected coronary artery disease. A coronary angiographic jeopardy score was calculated for each patient.

RESULTS

The coronary jeopardy score ranged from 0 to 12 (median 4). Ejection fraction fell significantly during exercise from 46% to 34%. Patients were divided into two groups based on the response of their ejection fraction to exercise. In 14 patients (group I), the peak change in ejection fraction coincided with the end of exercise, whereas in the other 17 patients (group II) the peak change in ejection fraction occurred before the end of exercise, resulting in a brief plateau. The peak change in ejection fraction and the time to its occurrence were independent predictors of coronary jeopardy (r = -0.59, p < 0.001 for peak change and r = -0.69, p < 0.001 for time to that change). The rate of change in ejection fraction was the strongest predictor of coronary jeopardy (r = -0.81, p < 0.001). In group I the peak change in ejection fraction was a poor predictor severity of coronary disease (r = -0.28, NS), whereas the time to peak and the rate of change in ejection fraction were good predictors (r = -0.65 and r = -0.73, p < 0.01). In group II the peak, the time to the peak, and the rate of change in ejection fraction were good predictors of coronary jeopardy (r = -0.75, r = -0.61, and r = -0.83, p < 0.01).

CONCLUSION

The rate of change of ejection fraction during exercise can be assessed by continuous monitoring of left ventricular function with the nuclear probe, and is the best predictor of functionally significant coronary artery disease.

Quantitative phase analysis in the assessment of coronary artery disease

The phase image in radionuclide ventriculography shows the timing of ventricular contraction and is valuable in the detection of abnormalities induced by coronary artery disease. The image is usually interpreted subjectively, and in the present study a histogram of left ventricular phase values was used to make interpretation more objective. The left ventricular ejection fraction and the standard deviation, skewness, and kurtosis of the phase histogram were measured at rest, during isometric exercise, and during the final two stages of maximal dynamic exercise in 25 controls and 27 patients with coronary artery disease without previous infarction. The ejection fraction and the standard deviation of the phase had the same predictive accuracy for the presence of disease when measured during the penultimate stage of dynamic exercise (89%) as during the final stage, but their accuracy was lower during maximal exercise (77%) because of motion artefact at high exercise levels. Skewness and kurtosis of the histogram were of no value for the detection of disease, and isometric exercise was of only limited value. It is concluded that the phase histogram provides an objective measurement of the synchronicity of left ventricular contraction and can increase sensitivity for the detection of abnormality. Data should be acquired at all stages of dynamic exercise, and the penultimate stage should be used if there is any doubt about the validity of the final stage.

Limitations in the interpretation of rest-exercise ejection fraction changes after early thrombolytic therapy during acute myocardial infarction

The effect of exercise on left ventricular wall motion in the infarct and noninfarct regions, and their contribution to the global ejection fraction response to exercise was evaluated in 24 patients studied at least 2 weeks following thrombolytic therapy for acute myocardial infarction. To achieve this goal, a nonstandard protocol was used: contrast ventriculography was performed at rest and immediately following 3 minutes of supine bicycle exercise at 50 watts. Wall motion in the infarct and noninfarct regions was measured using the centerline method. The global ejection fraction response to exercise correlated poorly with the exercise response of motion in the infarct region (r = 0.38). In 15 of the 24 patients, the function of the infarct and noninfarct regions changed in opposing directions, and in only 8 (53%) of these did the global ejection fraction response follow the exercise response of motion in the infarct region. The motion of the noninfarct region was the predominant influence on the ejection fraction response in the other 7 patients. Subgroup analysis revealed that the global ejection fraction response was more dependent on the response of motion in the anterior wall (r = 0.71, p less than 0.001) than in the inferior wall (r = 0.16), regardless of infarct location. The regional wall motion response to exercise also better distinguished reperfused from nonreperfused patients than did the ejection fraction response. These results indicate that the global ejection fraction response to exercise may be an unreliable indicator of the functional status of the infarct region.(ABSTRACT TRUNCATED AT 250 WORDS)