Effect of Infarct Site on Diastolic Time During Exercise: Statistical Analysis

Effect of Infarct Site on Diastolic Time During Exercise: Statistical AnalysisCoronary Arteriography and Ventriculography
Coronary arteriography was performed within 1 week prior to the exercise test. Coronary artery lesions with 70 percent or more reduction in diameter were considered to be obstructive. Each patient was classified as having one, two, or three-vessel disease, but patients with multivessel disease were not included in this study. Regional left ventricular wall motion abnormalities were assessed by biplane ventriculography. Analysis of the left ventricular wall was performed with seven segments (anterobasal, anterolateral, apical, diaphragmatic, posterobasal, septal, and posterolateral) according to the American Heart Association committee report and the number of segments with wall motion abnormalities were calculated. Patients with mitral regurgitation were not included in this study.
Radionuclide Angiography
Radionuclide angiography was performed within 3 days of the bicycle exercise test. Left ventricular end-diastolic and end-systolic volumes were determined by the first-pass method with a computerized multicrystal camera (Baird-Atomic System-77) in the anterior projection. Left ventricular ejection fraction was determined from the background-corrected representative cardiac cycle as follows: (end-diastolic counts minus end-systolic counts)/end-diastolic counts x 100. Left ventricular end-diastolic volume was calculated by the area-length method of Dodge and associates, with the ellipse of revolution modified for the single anterior plane projection as 0.85 x A2/L, where A is the area obtained by planimetry, and L is the longest diameter measured from the aortic valve to the apex of the left ventricle. The reliability and reproducibility of this method have been reported.
Thallium 201 Scintigraphy
Single-photon emission computed tomography was performed 1 to 2 weeks after the bicycle exercise test to evaluate a residual ischemic region. A bicycle ergometer was employed for graded exercise testing with 25-W increments every 3 min, and the ECG was continuously monitored during exercise and recovery period. A standard 12-lead ECG also was recorded at rest, at peak exercise, and 4 min into the recovery period; 111 mEq of thallium 201 was injected intravenously at the last minute and tomograms were obtained within 10 min on the completion of exercise and 4 h after initial tracer injection (redistribution scintigraphy). A large field-of-view gamma camera with a high-resolution parallel-hole collimater (Toshiba GCA-601E) was rotated 180° around the long axis. Thirty-six views every 5° were obtained for 25 s from the 45° left posterior oblique to the 45° right anterior oblique angle. After correction for nonuniformity and center of rotation, images were reconstructed into long- and short-axis cuts. Thallium studies were visually interpreted by two independent observers blinded to the clinical and angiographic data. Each view was separated into five segments as anterior, lateral, posterior, inferior, and intraventricular septum. Thallium uptake in each of the five segments was classified as normal=0, possibly reduced =1, reduced = 2, and absent = 3. A score change of at least 2 between exercise and redistribution images was considered a transient defect, whereas scores 2 and 3 in both images were defined as necrotic areas.
Linear and nonlinear regression models were derived for the QS2-HR and DT-HR relationships in each studied group. The two regression lines were then analyzed for equality of intercept and slope with analysis of covariance. Repeated measures of analysis of variance were used to compare the values during exercise. Statistical significance was accepted at the 95 percent confidence level (p<0.05). The results were expressed as the mean ± SD.

This entry was posted in Cardiology and tagged anterior inferior, coronary arteries, ejection fraction, norepinephrine, pulmonary artery.