Pulmonary hypertension and heart failure : physiological markers assessed by cardiovascular magnetic resonance

Pulmonary hypertension (PH) is clinically and physiologically associated with heart failure, both with reduced and preserved ejection fraction (HFrEF and HFpEF). In HFpEF, the most likely underlying pathophysiological mechanism is an impairment of left ventricular relaxation named diastolic dysfunction. The close relationship between PH, diastolic dysfunction, and heart failure makes it difficult to clearly distinguish between them in clinical practice. Given the challenges around screening and diagnosis of both PH and diastolic dysfunction, better diagnostic tools are needed to complement the existing ones. Cardiovascular magnetic resonance (CMR) is considered the most accurate imaging modality in the assessment of myocardial anatomy and function. Furthermore, CMR offers the possibility of qualitatively and quantitatively assess blood flow in large and medium vessels. Constant technical innovations push to further develop the current clinical capabilities of CMR and enable better and faster diagnosis of cardiovascular diseases.

In this thesis, we aimed to expand the current clinical capabilities of CMR in the diagnosis of pulmonary hypertension and diastolic dysfunction, which are not routinely assessed with this imaging modality. In Study I, we investigated the effect of body position in pulmonary blood flow distribution and documented a new variable, termed pulmonary vascular distensibility reserve, possibly related to left atrial pressure. In Study II, we found that CMR has a higher diagnostic yield than echocardiography for estimation of elevated pulmonary artery pressure. In Study III, CMR estimation of pulmonary artery pressure showed very good agreement with invasively measured pressure, and better sensitivity and accuracy than echocardiography. In Study IV, we developed a high temporal resolution CMR method to measure transmitral blood and myocardial tissue velocities, which had good agreement with echocardiography. Lastly, in Study V, we found that a comprehensive CMR method to diagnose and grade diastolic dysfunction showed very good agreement with echocardiography. These results suggest that novel and established CMR-based methods can diagnose pulmonary hypertension and diastolic dysfunction. Therefore, CMR may one day play an important role in the diagnostic investigation of these pathologies.

List of scientific papers

I. Wieslander B, Ramos JG, Ax M, Petersson J, Ugander M. (2019). Supine, prone, right and left gravitational effects on human pulmonary vascular physiology. J Cardiovasc Magn Reson. 2019 Nov 11; 21(1):69.
https://doi.org/10.1186/s12968-019-0577-9

II. Ramos JG, Fyrdahl A, Wieslander B, Reiter G, Reiter U, Jin N, Maret E, Eriksson M, Caidahl K, Sörensson P, Sigfridsson A, Ugander M. Cardiovascular magnetic resonance 4D flow analysis has a higher diagnostic yield than Doppler echocardiography for detecting increased pulmonary artery pressure. BMC Medical Imaging. 2020 Mar 6; 20(1):28.
https://doi.org/10.1186/s12880-020-00428-9

III. Ramos JG, Wieslander B, Fyrdahl A, Reiter G, Reiter U, Jin N, Skott V, Melin M, Sundblad P, Sigfridsson A, Ugander M. Detecting pulmonary hypertension by cardiovascular magnetic resonance four-dimensional flow analysis or echocardiography – comparison with catheterization. [Manuscript]

IV. Fyrdahl A, Ramos JG, Eriksson MJ, Caidahl K, Ugander M, Sigfridsson A. Sector-wise golden-angle (SWIG) phase contrast with high temporal resolution for evaluation of left ventricular diastolic dysfunction. Magn Reson Med. 2020 Apr; 83(4):1310-1321.
https://doi.org/10.1002/mrm.28018

V. Ramos JG, Fyrdahl A, Wieslander B, Reiter G, Reiter U, Jin N, Maret E, Eriksson M, Caidahl K, Sörensson P, Sigfridsson A, Ugander M. Comprehensive CMR diastolic dysfunction grading shows very good agreement compared to echocardiography. [Manuscript]