Echocardiography/Doppler for the evaluation of coronary artery function, left ventricular function and the relationship between early diastolic and systolic function

Two specific areas of development in echocardiography are assessment of left ventricular (LV) diastolic function and myocardial ischemia. This thesis describes echocardiographic methodology in these two areas. In the first study, two new echocardiographic methods, the early diastolic flow propagation velocity (Vp) and the early diastolic atrioventricular plane downward slope (EDS), were tested as diastolic parameters. Both Vp and EDS were found to have limited value as single parameters for the assessment of diastolic LV function, due to a poor capacity to discriminate between normal diastolic function and various degrees of diastolic dysfunction. In studies II and III, we examined the relationship between the early diastolic parameters, Vp and EDS, and LV systolic function. This relationship was found to be stronger than the relationship between these early diastolic parameters and overall LV diastolic function, assessed using traditional Doppler evaluation. The findings in these two studies are supportive of an alternative definition of systole and diastole, where systole also includes the early diastolic relaxation and rapid LV filling phase. The fourth and fifth studies investigated the accuracy and clinical feasibility of two contrast echocardiography methods in patients admitted due to acute coronary syndrome. Study IV explored a non-invasive method of measuring the coronary flow reserve in the left anterior descending coronary artery (LAD), using high-resolution colour Doppler and contrast echocardiography before and during adenosine infusion. The method was highly accurate and feasible in this clinical setting, having a negative predictive value of 100 %. It could, therefore, be an alternative to coronary angiography in specific clinical situations where a stenosis in the LAD region is important to rule out. The final study of this thesis tested the feasibility of the new real-time myocardial contrast echocardiographic perfusion technique (RTP) in the clinical bedside setting. The RTP investigation was performed prior to coronary angiography and demonstrated good accuracy for the assessment of significant stenosis in the three main coronary vessels. In summary, this thesis suggests that Vp and EDS are of limited value for the assessment of overall LV diastolic function, perhaps due to heterogeneity of diastole and a close relationship between LV early diastolic filling and systolic function. Echocardiographic evaluation of myocardial ischemia using RTP and high-resolution colour Doppler is feasible and accurate in the coronary care unit.