Page 116 - Assessing right ventricular function and the pulmonary circulation in pulmonary hypertension Onno Anthonius Spruijt

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is insufficient. This technique has been successfully used in the study of the mechanisms of ventricular interdependency [33, 34]. These studies show that there is a left to right asynchrony in the peak of circumferential shortening, which is caused by RV overload and plays a role in the leftward septal bowing and thereby impairing LV filling (Figure 4). A relatively new technique to assess strain is feature tracking. The advantage of this technique is that there is no need to obtain additional sequences and strain analyses can be applied on standard short-axis images. Feature tracking has been validated for circumferential strain analyses [35].
Figure 4: Circumferential strain curves after the electrocardiographic R-wave for the septum, right and left ventricle in a patient with severe pulmonary hypertension. MRI myocardial tagging is used to calculate the circumferential strain. From this image it is clear that time to right ventricular peak shortening is delayed in comparison to the left ventricle. As a consequense leftward septal bowing occurs. Note that right ventricular contraction continues after pulmonary valve closure leading to the so called end-systolic right ventricular isovolumetric shortening (adapted from: [33])
• Finally, advances in MRI make it possible to visualize and measure coronary artery flow and perfusion. From animal studies it is known that RV coronary perfusion is not or little impeded in systole. By using MR-based coronary flow assessment it was shown that in patients with RV hypertrophy coronary arterial flow in systole is impeded, and in severe RV hypertrophy even total mean flow to the RV is reduced [36]. Whether this reduction of coronary blood flow per gram RV