Normal and Abnormal Findings from Exercise Stress ECG, Post-Exercise Echocardiography and Angiography Studies in a Series of Hypertensive and Normotensive Individuals
The purpose of this investigation was to compare the frequencies of normal and abnormal findings from exercise electrocardiography (ECG), post-exercise echocardiography (ECHO) and angiography studies in a series of hypertensive and normotensive individuals who underwent diagnostic testing. Data for the ECG and ECHO were obtained simultaneously and the angiography was performed either before or following the exercise stress test. Thirty-seven cases were included in this retrospective study. Records were excluded if patients had: history of myocardial infarction; valvular heart disease; ECG evidence of abnormal Q waves, left ventricular hypertrophy (LVH) with abnormal ST/T wave pattern, or left bundle branch block (LBBB); medications that would alter blood pressure responses or ECG interpretation, technically uninterpretable records; or failure to attain 85% of age-adjusted maximal heart rates during the exercise tests. Subjects were defined as hypertensive (HYP) if at least two of the following criteria were met: 1) SBP ≥ 140 mmHg or DBP ≥ 90 mmHg; 2) current use of antihypertensive medications; or 3) history of hypertension. Normotensive subjects (NORM) were defined as absence of the above criteria. Data for the ECG and ECHO variables were obtained simultaneously in association with treadmill exercise studies. In each test, ECG measures were taken at peak exercise while the ECHO data were taken within 90 seconds immediately post exercise to obtain images. ECG response was considered abnormal if the ST shifted ≥ .1 mV from baseline at J₆₀ , while the ECHO response was considered abnormal when new or worsening of pre-existing wall motion abnormalities was observed. The 2-D ECHO's were recorded with the subject in the left lateral decubitus position, and parasternal long- and short-axis apical two and four chamber views were recorded for qualitative determination of wall motion abnormalities. Eleven of the 37 subjects also underwent angiography. Chi-square analysis demonstrated that high blood pressure status did not increase the frequency of abnormal test results for the ECHO (Χ²= 0.00009, DF = 1, p>.05), the exercise ECG (Χ²= 0.07, DF = 1, p>.05) nor for the angiography (Χ²= 0.69, DF = 1, p>.05). These results indicate that resting blood pressure does not influence the occurrence of abnormal vs normal ECG and ECHO findings nor angiography findings between hypertensive and normotensive subjects. There was also no significant differences between the ECG and ECHO in the occurrence of abnormal findings for NORM subjects (Χ²=2.43E-015, DF = 1, p>.05) nor HYP subjects (Χ²=0.13, DF = 1, p>.05). The ECHO showed 80% true-positive findings and the ECG showed 60% compared to the angiography. Both the ECG and ECHO had the same percentage of true-negatives (33%) compared to the angiography results. Since there was a higher percentage of ECHO true-positive results compared to the angiography then the ECG, this may indicate that the ECHO is comparable to the angiography findings and may be a better predictor in determining disease than the ECG. However, these data warrant further evaluation studies.