Assessment of Pulmonary Blood Flow in Heart Failure. Using Novel and Non-invasive Diagnostic Methods

Abstract: In heart failure (HF), the heart is unable to pump effectively in order to satisfy the demands of the body. The elevated filling pressure seen in HF leads to accumulation of fluid in the lungs, i.e pulmonary congestion. While investigation with chest X-ray is recommended, it has limitations in detecting pulmonary congestion. Ventilation/perfusion single-photon emission computed tomography (V/P SPECT), i.e tomographic lung scintigraphy, is a promising method to diagnose and quantify pulmonary congestion in HF but needs to be validated by invasive right-heart catheterization. The variation of the blood volume in the pulmonary circulation measured by magnetic resonance imaging (MRI) may also have the potential to quantify the severity of HF.The general aim of this thesis was to develop and validate new non-invasive methods to diagnose and quantify pulmonary congestion and variation of the pulmonary blood flow in patients with HF, as well as to follow-uppulmonary congestion.Paper I revealed that the degree of pulmonary congestion in HF could be diagnosed and quantified using V/P SPECT. It was validated with right-heart catheterization. V/P SPECT was more accurate than chest X-ray in diagnosing pulmonary congestion in HF.In Paper II V/P SPECT showed that the pulmonary perfusion pattern was improved and that V/P SPECT could be used to follow treatment effect after heart transplantation in patients with HF and quantify the degree of pulmonarycongestion. It was validated with right-heart catheterization.Paper III demonstrated that V/P SPECT could be used to follow treatment effect and assess the degree of pulmonary congestion in patients with HF after receiving cardiac resynchronization therapy (CRT). V/P SPECT was associated with improvement in patients’ symptoms.Paper IV showed that the pulmonary blood volume variation differed between patients with HF and healthy controls. In patients with HF, approximately 40% of the variation could be explained by the left ventricular longitudinal contribution to stroke volume and the phase shift between the in- and outflow to the pulmonary circulation. The remaining variation (60%) likely occur on a small vessel level.In summary, pulmonary congestion in HF is difficult to quantify objectively. The non-invasive methods V/P SPECT and MRI might add complementary information in the diagnosis of HF. V/P SPECT can be used to follow treatment effects after heart transplantation and CRT and may have a role in avoiding invasive right-heart catheterization in selected cases and aid in treatment decision.