**1.4 Detection of dysfunction of the microcirculation**

As already mentioned, myocardial blush grade as assessed in the catheterization laboratory evaluates the function of the microcirculation.

Extent of resolution of ST-segment elevation after primary angioplasty is an adequate indicator of the function of the microcirculation and myocardial perfusion.

Measurement of coronary flow velocities using Doppler wire and pressure recordings to assess severity of coronary artery stenoses are invasive procedures in addition to other disadvantages (Iliceto et al 1991; Erbel et al, 1991; Kozakova et al, 1994; Donohue et al, 1993; Miller et al, 1994; Di Carli et al, 1995).

Trans-esophageal echocardiography visualizes only the proximal coronary arteries and Doppler sampling is feasible in less than 70% of patients (Joye et al, 1994; Kern et al 1995; Abizaid et al, 1998).

Recent technologic advances in trans-thoracic echocardiography made Doppler sampling of coronary artery velocities possible (Voci et al, 1998; Caiati et al, 1999; Hildick-Smith et al, 2000; Higashiue et al, 2001; Pizzuto et al, 2001; Takeuchi et al, 2001). Contrast agents may enhance the detection rate of coronary velocities (Abizaid et al, 1998; Caiati et al, 1999), however, an experienced operator is essential.

Sampling of blood velocities in the left anterior descending coronary artery is successful almost in all patients. The advantages of Doppler sampling of coronary artery blood velocities is that it is non-invasive and can be repeated easily in the coronary care unit. As we demonstrated recently using transthoracic Doppler, the function of the microcirculation is dynamic and changes after primary angioplasty (Sharif et al, 2008; 2010). After primary coronary intervention in acute myocardial infraction the microcircirculation may improve or deteriorate. Therefore, transthoracic Doppler sampling of coronary artery velocities is even more important than other methods for the evaluation of the function of coronary microcirculation.
