CC Cardiol Croat Cardiologia Croatica Cardiol. Croat. 1848-543X 1848-5448 Croatian Cardiac Society CC 2023 18_5-6_168-9 10.15836/ccar2023.168 Extended Abstract Assessment of diastolic dysfunction markers in hypertrophic cardiomyopathy patients with 4D flow magnetic resonance imaging and Doppler echocardiography https://orcid.org/0000-0002-7865-1108LončarićFilip12* https://orcid.org/0000-0003-1349-2457FerezXabier Morales3 https://orcid.org/0000-0003-0438-8244DelsoGaspar4 https://orcid.org/0000-0002-1718-2424Garcia-AlvarezAna24 https://orcid.org/0000-0003-0087-7489TenaJordi Mill3 https://orcid.org/0000-0003-3539-6917DoltraAdelina24 https://orcid.org/0000-0003-1300-4732SitgesMarta24 https://orcid.org/0000-0002-5125-6132CamaraOscar3 https://orcid.org/0000-0003-3130-6937BijnensBart3 University Hospital Centre Zagreb, University of Zagreb School of Medicine, Zagreb, Croatia August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Barcelona, Spain Universitat Pompeu Fabra, Department of information technologies and communication, Simulation, Imaging and Modelling for Biomedical Systems, Barcelona, Spain Cardiovascular Institut, Hospital Clínic, University of Barcelona, Barcelona, Spain ADDRESS FOR CORRESPONDENCE: Filip Lončarić, Klinički bolnički centar Zagreb, Kišpatićeva 12, HR-10000 Zagreb, Croatia. / Phone: +385-91-2220-480 / E-mail: loncaric.filip@gmail.com 042023 18 5-6 168 169 26032023 29032023 2023 Croatian Cardiac Society KEYWORDS: 4D Flowmagnetic resonance imagingechocardiographyhypertrophic cardiomiopathy

Introduction: Transthoracic echocardiography (TTE) is the gold standard in the assessment of diastolic dysfunction, however, measurement of diastolic markers such as the pulmonary vein (PV) inflow velocities is often challenging. 4D flow cardiac magnetic resonance imaging (CMR) enables quantification of velocities in any target volume without the constraints faced by TTE. We explored the use of 4D flow CMR in generating Doppler-like velocity spectrograms of mitral and PV inflow and comparing them to actual echo-based pulsed-wave (PW) Doppler velocity curves.

Patients and Methods: A total of 6 HCM patients were included (P1-6). TTE was performed with a GE E95 system. Mitral and PV inflow PW Doppler was performed in the apical 4-chamber view by placing the sample volume at the level of the leaflet tips and at the inflow of the PV. The CMR data was acquired through a GE SIGNA Architect 3.0T scanner. The left atrium (LA), ventricle and outflow tract (LVOT) were segmented from a 4D flow phase contrast angiogram. The sample volume of PW Doppler was imitated using spheres of 4 mm radius placed in the same positions as in TTE. Velocities were projected in the direction typically captured by the echo transducer generating Doppler-like images. The duration of the pulmonary Ar and the mitral A wave was measured using both methods.

Results: Figure 1 shows volumetric renderings of velocity at mid-systole. Compared to P1 and P2, P3-6 present an accelerated LVOT flow due to obstruction caused by systolic anterior motion, causing posterolateral mitral regurgitation disrupting LA hemodynamics. Figure 2 demonstrates the mitral and pulmonary inflow patterns obtained with TTE and CMR. Peak velocities and the duration of the A/Ar waves were comparable when quantified using both modalities (Table 1). Ar wave duration could be quantified in all CMR studies, showing heterogeneity between the four PVs, whereas AR could be measured in only 3/6 of the echo studies.

Volumetric rendering of the 4D flow MRI velocity fields mid-systole, including arrows pointing in the direction of the blood flow. A clear LVOT obstruction can be observed in patients 3-6 caused by systolic anterior motion. The distinctive rotational flow pattern in the LA is a consequence of the mitral regurgitation jet.

The synthetic 4D flow derived PW Doppler velocity curves alongside the authentic PW Doppler. The sample volume for the PV acquisitions was located in the right superior PV, while the mitral valve profiles were extracted from the leaflet tips.

 AR and A wave duration measurements performed from cardiac magnetic resonance and transthoracic echocardiography images, respectively.
Patient 1 2 3 (AF noA wave) 4 5 6
Ar Duration RS-4D (ms) 198 136 – 188 180 260
RI-4D (ms) 168 97 – 229 193 200
LS-4D (ms) 168 58 – 229 138 260
LI-4D (ms) 137 233 – 313 346 421
RS-Echo (ms) 185 206 – – 220 –
Mitral A Duration MV-4D (ms) 150 191 – 123 136 158
MV-Echo (ms) 145 181 – 140 156 166
RS - right superior PV; RI – right inferior PV; LS – left superior PV; LI – left inferior PV

Conclusion: 4D CMR shows potential for blood flow assessment previously feasible only via TTE. CMR could provide a more reproducible assessment of PV inflow velocities, relevant in assessing diastolic function, and potentially reveal new insights about LA hemodynamics.