Exploring the effects of mavacamten through hemodynamic force analysis in patients with obstructive hypertrophic cardiomyopathy
Authors: Milazzo A , Zocchi C , Del Franco A , Panichella G , Garofalo M , Fanizzi A I , Ragagnin M , Pieroni M , Zampieri M , Emdin M , Chan R H , Pedrizzetti G , Olivotto I 
Published: October 2024

Abstract

Introduction
Mavacamten is a first-in-class allosteric myosin inhibitor effective in relieving left ventricular (LV) outflow tract obstruction in patients with obstructive hypertrophic cardiomyopathy (oHCM). To date, however, its effect on cardiac mechanics is still unclear.
Hemodynamic force (HDF) analysis represents the fluid dynamics correlate of deformation imaging, showing a greater sensitivity in detecting early mechanical abnormalities or response to treatment [1].

Purpose
To explore the in vivo effect of mavacamten on cardiac mechanics in patients with HCM after a 3 year-treatment, using HDF analysis.

Methods
LV HDF analysis was performed in 6 patients with oHCM (representing a cohort of the MAVA-LTE study) at baseline and after 3 years of treatment. Apical 4-, 2-, and 3-chamber echocardiographic views were analysed using a dedicated and sofisticated software. Base-apex forces (where positive deflections represent a force directed from the apex to the base of LV, whilst negative ones are directed toward the LV apex) were assessed in terms of timing indexed to cardiac cycle duration.
HDF curves from the 6 patients treated with macavamten were compared to those obtained from oHCM patients (n=20), non-obstructive HCM (noHCM) patients (n=20), and healthy controls (n=22).

Results
Figure 1 shows a different pattern of transition between diastole and systole in HCM patients compared to controls. Specifically, HCM patients exhibited an earlier onset of the systolic phase, expressed as a fusion of late diastolic deceleration and systolic thrust. This was numerically represented as a decrease in diastolic-systolic transition time, which is 0.22 [0.20-0.24] for oHCM, 0.23 [0.21-0.25] for noHCM and 0.26 [0.26-0.30] for controls (p ≤0.001 for control vs oHCM, p ≤0.01 for control vs noHCM). Additionally, HCM patients showed an increased rate of force generation. The time to systolic peak (i.e., time interval from the onset of systole to the maximum force) was reduced in HCM patients compared to controls, and was shorter in oHCM than in noHCM patients (0.13 [0.11-0.15] vs 0.16 [0.14-0.17], p ≤0.01), thus reflecting an increased clinotropism in HCM. After 3 years of mavacamten treatment, the diastolic-systolic transition time and the time to systolic peak returned to a level similar to that of healthy controls (0.30 [0.27-0.30] in mavacamten group vs 0.26 [0.26-0.30], p &gt;0.05, and 0.21 [0.20-0.22] vs 0.19[0.17-0.20], p=0.04, respectively) (Figure 2).

Conclusion
HDF analysis reveals that mavacamten affects the duration of transition from diastole to systole and prolongs time from the onset to the peak in systole. These findings may explain the removal of the mechanical coupling substrate responsible for the systolic anterior movement of mitralic leaflets and the subsequent resolution of LV outflow tract obstruction by mavacamten.Distribution of time parameters