الفهرس 
Myocardial Ischaemia Despite AngiographicallyOnly 14 pages are availabe for public view
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Abstract
Thirty percent of patients undergoing coronary arteriography because of chest pain are found to have normal epicardial coronary arteries. The unnecessary risk of cardiac catheterization and considerable coasts can be avoided when some of those patients are filtered probably by the appropriate non-invasive diagnostic tests.
This study aimed at evaluating the accuracy of mostly used non-invasive diagnostic tools (exercise electrocardiography, radionuclide myocardial perfusion scintigraphy and dipyridamole stress echocardiography) in view of the recent knowledge and updates including the recently evolved tissue Doppler imaging modality as an integral part of stress echocardiography examination.
Twenty-five subjects with normal coronary arteriographies (NC group) were compared to another age matching group of twenty-five patients that have 50% or more stenotic lesions in at least one coronary artery (CAD group). Patients with cardiomyopathy, myocardial infarction, bundle branch block, hypertension with left ventricular hypertrophy, left ventricular systolic dysfunction and cardiac valve diseases were excluded.
Dipyridamole stress 2-D echocardiography as well as baseline and low-dose (0.56 gm/kg) mitral flow and tissue Doppler quadrilateral mitral annular velocities were recorded and analyzed for all cases of the study. Treadmill exercise electrocardiograms and radionuclide myocardial perfusion scans were also obtained and analyzed for all cases of NC group and for 21 and 20 respectively in CAD group.
Exercise electrocardiography showed 86% sensitivity and 54% specificity in the diagnosis of coronary artery disease in our study. Despite its low specificity, exercise testing gains its popularity from being widely available, cheap and easily performed. In subsets of patients, exercise testing is of limited value due to higher probability to have false positive results as in bundle branch block, left ventricular hypertrophy, female gender, digitalis and other drug therapy. Despite of excluding most of these factors in our study, 46% of our normal coronaries group cases had such a result for which they have been referred for coronary arteriography.
Radionuclide myocardial perfusion scintigraphy is reported to have superior accuracy compared to exercise ECG in the diagnosis of coronary artery disease. It is also indicated in a subset of patients that can’t exercise or have high probability to get inconclusive results. In concordance to the published data, our study showed 95% sensitivity and 80% specificity for radionuclide myocardial perfusion scintigraphy. However, 20% of our NC group had perfusion defects that could be due to absorption artifacts or can be related to microvascular angina reported to be the cause in a subset of patients known as “syndrome x”.
Dipyridamole-atropine stress 2-D echocardiography in our study had similar sensitivity (96%), but higher specificity (100%) compared to radionuclide myoscan. Dipyridamole stress echocardiography is reported in a large scale of studies to have the highest specificity compared to other diagnostic tests for the diagnosis of coronary artery disease. The use of second harmonic imaging available in all recent echocardiographic machines is reported to increase the accuracy of endocardial border delineation during stress echocardiography resulting in more sensitivity.
Tissue Doppler imaging is a recently evolved new echocardiographic tool that provided new aspects in cardiac diagnosis. Mitral annulus tissue Doppler velocities have become an integral part of any echocardiography examination. Left ventricular diastolic function is accurately evaluated from the relation of mitral flow velocities (Ev and Av) to mitral annulus tissue Doppler velocities (Ea and Aa). Other studies reported that invasively measured left ventricular filling pressure correlates accurately to that derived from echocardiography obtained E/Ea ratio. The systolic annular velocity (Sa) is also reported to add more accuracy identifying viable myocardium during stress echocardiography.
In this study, systolic annulus velocity was similar in both groups at baseline but became significantly higher in NC group compared to CAD group after low-dose dipyridamole infusion in the four aspects of the mitral annulus (P = 0.38, 0.016, 0.015 and 0.001 for septal, lateral, inferior and anterior respectively).
Diastolic function as assessed by mitral flow velocities only (Ev and Av) in response to low-dose (0.56 mg/kg) dipyridamole infusion did not show any difference between NC and CAD groups. When regional diastolic function was considered relating mitral flow and tissue Doppler velocities of the septal (Esa and Asa), lateral (Ela and Ala), inferior (Eia and Aia) and anterior (Eaa and Aaa) mitral annulus aspects, the NC group had better diastolic function compared to CAD group. Ev/Esa in NC group was significantly (p < 0.03) lower than CAD group indicating significantly higher left ventricular filling pressure in patients with coronary artery disease in response to dipyridamole.
Our findings confirm that cardiac catheterization can be confidently avoided in a considerable number of patients with chest pain if they are properly evaluated non-invasively. Exercise ECG, stress myocardial perfusion scans and stress echocardiography provide non-invasive, less coasty, commonly available and excellent graded accurate filters before coronary arteriography is indicated for chest pain evaluation. Mitral flow and mitral annulus tissue Doppler velocities are promising parameters that may add more details for stress echocardiography resulting in more diagnostic confidence.