Contents

  1. Background
  2. LV mass regression
  3. Topology of regional regression in wall thickness
  4. Tissue composition: ECV, cellular and matrix volumes
  5. Drivers of regional regression in wall thickness

Mavacamten MoA

\(\uparrow\) probability of \(SRX\) state

\(\downarrow\) rate of \(P_i\) release \(\rightarrow\) \(\downarrow\) ATPase activity

Clinical Effect

In obstructive HCM

  • Improves symptoms and increases \(pVO_2\)
  • \(\downarrow\) NT-proBNP, LV mass, LAVi

In non-obstructive HCM

  • Does not improve symptoms or \(pVO_2\)
  • \(\downarrow\) NT-proBNP, LV mass, LAVi

HCM is a regional disease

 

 

 

 

Study Design

Adults with HCM and:

  1. NYHA II or III
  2. \(Max\,LVOT\,gradient\geq 50 mmHg\), at rest or provocation
  3. \(LVEF \geq 55\%\)

Mavacamten started at \(2.5\,mg\)

Up-titrated according to LVOT gradient and symptoms.

Clinical follow-up monthly for first 3-4 months.

CMRs at baseline, 2 and 6 months.

Flow diagram

Baseline characteristics

Characteristic N = 351
Age 61 (11)
Sex
    female 12 (34%)
    male 23 (66%)
Ethnicity
    Asian or Asian British 8 (23%)
    Black, Black British, Caribbean or African 1 (2.9%)
    Mixed or multiple ethnic groups 1 (2.9%)
    White 22 (63%)
    Any other ethnic group 3 (8.6%)
Hypertension 10 (29%)
Diabetes Type 2 3 (8.6%)
Dyslipidaemia 3 (8.6%)
Smoking 0 (0%)
Atrial Fibrillation 6 (17%)
Stroke 1 (2.9%)
Family History of SCD 3 (9.1%)
Family History of Cardiomyopathy 0 (0%)
Gene Positive 11 (31%)
Gene Classification
    non pathogenic 0 (0%)
    VUS 4 (36%)
    pathogenic 5 (45%)
    likely pathogenic 2 (18%)
    likely non-pathogenic 0 (0%)
    not_applicable 0 (0%)
    missing 0 (0%)
Variant
     24 (69%)
    CSPR3 1 (2.9%)
    MYBPC3 5 (14%)
    MYH7 4 (11%)
    TNNI3 1 (2.9%)
NSVT 7 (22%)
CYP450 Metaboliser
    poor 1 (2.9%)
    intermediate 8 (23%)
    normal 13 (37%)
    rapid 11 (31%)
    ultrarapid 2 (5.7%)
Bisoprolol 22 (63%)
Verapamil 12 (35%)
CIED
    no 27 (77%)
    PPM 1 (2.9%)
    ICD_transvenous 4 (11%)
    ICD_subcut 2 (5.7%)
    CRTP 0 (0%)
    CRTD 0 (0%)
    ILR 1 (2.9%)
ICD indication
    prim_prevention 6 (100%)
    sec_prevention 0 (0%)
Haemoglobin 141 (17)
Haematocrit 0.42 (0.05)
White Cell Count 7.70 (2.37)
creat 86 (19)
eGFR_epi_2021 82 (16)
Urea 6.07 (1.67)
NT-proBNP 1,277 (1,397)
hs Troponin T 15 (8)
LVEDV Indexed (trabecular) 76 (14)
LVEF (trabecular) 78 (7)
LV Mass Indexed (trabecular) 112 (37)
rvedv_i 82 (13)
rvef 62 (11)
mapse_avg 13.18 (2.90)
LA Area Indexed 17.8 (4.7)
RA Area Indexed 11.6 (3.4)
Global Native T1 1,028 (42)
Global T2 49 (2)
Max LVOT gradient (mmHg) 102 (38)
1 Mean (SD); n (%)

Overall effect

NYHA Class

LVOT gradient

Baseline 2 Months 6 Months
LVOT grad (mmHg) 102 69 50
% change 32% 51%
p<0.001 p<0.001

NT-proBNP

Baseline 2 Months 6 Months
NT-proBNP (pg/mL) 758 344 180
% change 55% 76%
p<0.001 p<0.001

Mavacamten dose

Dose at 6 months (mg) N (%)
2.5 10 (31%)
5 16 (50%)
10 6 (19%)

LV Mass

LV Mass Regression

Baseline 2 Months 6 Months
LVMi (g/m2) 113 103 96
% change -8.8% -15%
p<0.001 p<0.001

Heterogeneous response

Response not fully captured by maximal wall thickness

Baseline 2 Months 6 Months
MWT (mm) 19 18 17.1
p<0.001 p<0.001
LVEDVi (mL/m2) 76 76 75.1

Topology of hypertrophy regression

Baseline regional hypertrophy

Regional regression

Regional regression at 2 months

Segment Baseline_Z Post_Z Delta_Z CI P_adj Sig N_Hyper_Base N_Norm Pct_Norm
Basal Ant 3.60 3.08 -0.52 (-0.95, -0.10) 0.001 *** 21 7 33%
Basal AntSep 4.27 3.61 -0.66 (-1.02, -0.31) 0.000 *** 22 6 27%
Basal InfSep 4.47 3.87 -0.60 (-0.98, -0.22) 0.000 *** 22 3 14%
Basal Inf 5.39 4.46 -0.93 (-1.51, -0.35) 0.000 *** 26 7 27%
Basal InfLat 2.16 1.07 -1.09 (-1.80, -0.39) 0.001 ** 9 6 67%
Basal AntLat 3.34 2.68 -0.66 (-1.17, -0.16) 0.000 *** 17 7 41%
Mid Ant 4.36 3.79 -0.57 (-1.16, 0.02) 0.000 *** 20 4 20%
Mid AntSep 4.08 3.43 -0.65 (-1.11, -0.19) 0.000 *** 18 5 28%
Mid InfSep 4.87 4.23 -0.64 (-1.12, -0.16) 0.000 *** 22 3 14%
Mid Inf 5.31 4.38 -0.93 (-1.51, -0.35) 0.000 *** 26 6 23%
Mid InfLat 3.23 1.87 -1.36 (-1.99, -0.72) 0.000 *** 14 7 50%
Mid AntLat 3.98 3.20 -0.78 (-1.37, -0.20) 0.000 *** 18 4 22%
Apical Ant 3.49 3.19 -0.30 (-0.84, 0.24) 0.001 *** 16 3 19%
Apical Sep 3.14 2.51 -0.63 (-1.29, 0.03) 0.003 ** 13 3 23%
Apical Inf 3.37 2.48 -0.89 (-1.60, -0.18) 0.000 *** 15 3 20%
Apical Lat 3.02 2.77 -0.25 (-0.79, 0.29) 0.001 *** 13 2 15%

Regional regression at 6 months

Segment Baseline_Z Post_Z Delta_Z CI P_adj Sig N_Hyper_Base N_Norm Pct_Norm
Basal Ant 3.60 2.83 -0.77 (-1.21, -0.33) 0.001 *** 20 7 35%
Basal AntSep 4.27 3.23 -1.04 (-1.42, -0.67) 0.000 *** 21 6 29%
Basal InfSep 4.47 3.31 -1.16 (-1.56, -0.76) 0.000 *** 20 6 30%
Basal Inf 5.39 3.61 -1.78 (-2.39, -1.18) 0.000 *** 22 7 32%
Basal InfLat 2.16 0.96 -1.20 (-1.94, -0.46) 0.001 ** 9 6 67%
Basal AntLat 3.34 2.34 -1.00 (-1.53, -0.48) 0.000 *** 17 8 47%
Mid Ant 4.36 3.10 -1.26 (-1.88, -0.64) 0.000 *** 19 6 32%
Mid AntSep 4.08 2.91 -1.18 (-1.65, -0.70) 0.000 *** 17 4 24%
Mid InfSep 4.87 3.55 -1.33 (-1.83, -0.82) 0.000 *** 20 5 25%
Mid Inf 5.31 3.61 -1.71 (-2.31, -1.10) 0.000 *** 23 8 35%
Mid InfLat 3.23 1.67 -1.56 (-2.23, -0.90) 0.000 *** 14 8 57%
Mid AntLat 3.98 2.67 -1.32 (-1.93, -0.70) 0.000 *** 16 5 31%
Apical Ant 3.49 2.52 -0.97 (-1.55, -0.40) 0.001 *** 13 4 31%
Apical Sep 3.14 2.13 -1.01 (-1.70, -0.31) 0.003 ** 11 5 45%
Apical Inf 3.37 2.02 -1.35 (-2.10, -0.60) 0.000 *** 12 6 50%
Apical Lat 3.02 2.05 -0.97 (-1.54, -0.40) 0.001 *** 11 5 45%

Do non-hypertrophied segments regress?

Defined as baseline z-score < 3

Compared to hypertrophied segments

Defined as baseline z-score >3

Tissue Composition

Conventional tissue characterisation measures

Baseline 6 Months
T1 (ms) 1028 1021 (NS)
T2 (ms) 49 49.3 (NS)
LGE (g) 12.8 10.7 (NS)
LGE (% of LVM) 11.6 11.4 (NS)

Regional baseline LGE

ECV fraction

Baseline 6 Months
ECV (%) 28.8 28.6 (NS)

No difference across segments

Cellular & Matrix Volume

\[ \begin{align} \text{Cellular Vol.} &= \frac{\text{LVM}_i}{1.055} \times (1 - \text{ECV}) \\[1em] \text{Matrix Vol.} &= \frac{\text{LVM}_i}{1.055} \times \text{ECV} \end{align} \]

Regression of Cellular & Matrix Volume

Baseline 6 Months p-value
Cellular volume 30.9 26.7 <0.001
Matrix volume 12.6 11 <0.001

What drives hypertrophy regression?

Do segments with a lot of LGE regress?

Here defined as > 50% enhanced area

record_id segment_name lge_pea wt_mm_baseline wt_mm_cmr2 delta_z
HH02 Mid Anterior 50.4 16.8 14.0 -2.7
HH03 Basal Anteroseptum 50.1 18.0 18.2 0.1
MHCM06 Basal Inferior 62.8 19.8 16.8 -2.6
MHCM06 Basal Anterior 57.1 14.9 14.6 -0.2
MHCM14 Mid Anteroseptum 59.7 29.5 21.2 -5.2
MHCM14 Mid Inferoseptum 52.7 30.1 20.7 -6.2
MHCM23 Mid Inferolateral 64.2 20.1 15.1 -5.5
MHCM23 Mid Anterior 57.6 22.0 20.1 -1.7
MHCM23 Mid Anterolateral 50.2 20.1 18.5 -1.7

Mean delta z-score: -2.85

95% CI -5.01 to -0.7

P = 0.0138

What drives reverse remodelling?

Linear Mixed Effects Model:

Random effects: intercept and slope for baseline z-score.

Conclusion

Thank you

Supplemental

Regional regression of Cell Volume

Segment Baseline CMR2 Delta Lower Upper P_Val Sig
1 30.64979 26.10763 -4.542154 -6.553534 -2.530775 1.269333e-04 ***
2 30.38893 25.82103 -4.567905 -6.486260 -2.649550 7.022208e-05 ***
3 31.16680 26.71115 -4.455651 -6.405322 -2.505979 1.120028e-04 ***
4 30.61707 26.80265 -3.814417 -5.917493 -1.711341 1.136745e-03 *
5 31.12135 26.97990 -4.141457 -6.329761 -1.953153 7.720340e-04 ***
6 31.72916 27.04550 -4.683663 -6.728937 -2.638389 1.093029e-04 ***
7 30.83176 25.93268 -4.899080 -7.038289 -2.759872 1.222145e-04 ***
8 30.67890 26.08010 -4.598801 -6.724719 -2.472883 2.237167e-04 ***
9 30.85193 26.11540 -4.736530 -6.718763 -2.754297 7.810059e-05 ***
10 31.22928 26.58548 -4.643799 -6.773320 -2.514279 2.097054e-04 ***
11 31.65179 26.75740 -4.894381 -6.920580 -2.868183 7.065887e-05 ***
12 31.54261 26.31388 -5.228734 -7.199154 -3.258313 2.322199e-05 ***
13 31.11877 26.03088 -5.087894 -7.046260 -3.129528 2.449826e-05 ***
14 30.93117 26.60223 -4.328942 -6.042774 -2.615111 3.536829e-05 ***
15 31.24273 26.29616 -4.946578 -6.963845 -2.929310 4.976545e-05 ***
16 30.96388 26.34040 -4.623482 -6.522039 -2.724925 5.412365e-05 ***
Contrast Est. SE P-val
Septum - Inferior −0.308 0.180 0.318
Septum - Anterior 0.193 0.180 0.706
Septum - Lateral −0.447 0.156 0.022
Inferior - Anterior 0.501 0.201 0.063
Inferior - Lateral −0.139 0.180 0.866
Anterior - Lateral −0.640 0.180 0.002

Regional regression of Matrix Volume

Segment Baseline CMR2 Delta Lower Upper P_Val Sig
1 13.14903 11.46544 -1.683589 -2.484649 -0.88252891 2.805517e-04 ***
2 13.40988 11.75837 -1.651512 -2.565334 -0.73769096 1.183321e-03 *
3 12.63202 10.86025 -1.771763 -2.541411 -1.00211365 1.051335e-04 ***
4 13.18175 10.75813 -2.423614 -3.132993 -1.71423460 6.192978e-07 ***
5 12.67746 10.59032 -2.087136 -2.928832 -1.24544048 4.335353e-05 ***
6 12.06966 10.53041 -1.539249 -2.228000 -0.85049811 1.460265e-04 ***
7 12.94800 11.35170 -1.596299 -2.417062 -0.77553632 6.705049e-04 ***
8 13.11106 11.17724 -1.933823 -2.725103 -1.14254332 6.527289e-05 ***
9 12.93566 11.16203 -1.773631 -2.668355 -0.87890659 5.554829e-04 ***
10 12.54999 10.70350 -1.846485 -2.521882 -1.17108761 1.779285e-05 ***
11 12.13676 10.53019 -1.606571 -2.463538 -0.74960431 9.114019e-04 ***
12 12.24630 10.96921 -1.277089 -2.237164 -0.31701328 1.183959e-02 *
13 12.68004 11.53972 -1.140319 -2.213922 -0.06671516 3.845356e-02 *
14 12.86765 10.98789 -1.879757 -2.977944 -0.78156933 1.867079e-03 *
15 12.55608 11.28200 -1.274079 -2.529050 -0.01910786 4.690668e-02 *
16 12.83493 11.24273 -1.592199 -2.811444 -0.37295472 1.296667e-02 *
Contrast Est. SE P-val
Septum - Inferior 0.308 0.180 0.318
Septum - Anterior −0.193 0.180 0.706
Septum - Lateral 0.447 0.156 0.022
Inferior - Anterior −0.501 0.201 0.063
Inferior - Lateral 0.139 0.180 0.866
Anterior - Lateral 0.640 0.180 0.002

Mass & LVOT at 6 months

Relationship with NT-proBNP

Part 2

Does ECV influence hypertrophy regression?

Independent of reduction in LVOT gradient

NT-proBNP (linear axis)

Why this is not regression to the mean

1/ Random error scales with size

Segments with absolute WT in mm would have regressed more.

2/ ANCOVA

If a septal segment and an inferior segment started at the exact baseline Z-score, would they end up equal?

No, the septum would end-up significantly thicker:

Linear mixed model fit by REML. t-tests use Satterthwaite's method [
lmerModLmerTest]
Formula: cmr2 ~ baseline + region + (1 | record_id)
   Data: df_ancova

REML criterion at convergence: 470.7

Scaled residuals: 
     Min       1Q   Median       3Q      Max 
-2.43308 -0.56016 -0.04212  0.54723  2.30726 

Random effects:
 Groups    Name        Variance Std.Dev.
 record_id (Intercept) 1.3011   1.1407  
 Residual              0.4381   0.6619  
Number of obs: 186, groups:  record_id, 31

Fixed effects:
              Estimate Std. Error        df t value Pr(>|t|)    
(Intercept)   -0.26483    0.31443  66.54916  -0.842  0.40265    
baseline       0.71283    0.04344 131.86913  16.411  < 2e-16 ***
regionSeptum   0.31733    0.10817 163.73348   2.934  0.00383 ** 
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Correlation of Fixed Effects:
            (Intr) baseln
baseline    -0.710       
regionSeptm -0.426  0.307

3/ Direct comparison

Compared 2 competing models to predict % change in absolute wall thickness in mm: baseline mm vs baseline z-score.

[1] "AIC for MM Model:  3662.4"
[1] "AIC for Z Model:   3586.6"

4/ Magnitude of the effect

RTM typically accounts for small corrections, e.g. test-retest variability of 5-10%

We observe very large reductions in z-scores, 2 to 3.

3.2/ Individual model output

Linear mixed model fit by REML. t-tests use Satterthwaite's method [
lmerModLmerTest]
Formula: pct_change ~ wt_mm_baseline + (1 | record_id)
   Data: df_currency

REML criterion at convergence: 3654.4

Scaled residuals: 
    Min      1Q  Median      3Q     Max 
-3.7134 -0.5232 -0.0301  0.5649  3.2861 

Random effects:
 Groups    Name        Variance Std.Dev.
 record_id (Intercept) 70.33    8.386   
 Residual              83.66    9.147   
Number of obs: 492, groups:  record_id, 31

Fixed effects:
               Estimate Std. Error       df t value Pr(>|t|)    
(Intercept)     -1.8316     2.2838 110.7480  -0.802    0.424    
wt_mm_baseline  -0.6140     0.1208 489.6540  -5.083  5.3e-07 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Correlation of Fixed Effects:
            (Intr)
wt_mm_basln -0.730
Linear mixed model fit by REML. t-tests use Satterthwaite's method [
lmerModLmerTest]
Formula: pct_change ~ z_score_baseline + (1 | record_id)
   Data: df_currency

REML criterion at convergence: 3578.6

Scaled residuals: 
    Min      1Q  Median      3Q     Max 
-3.4322 -0.5653 -0.0154  0.5687  3.3123 

Random effects:
 Groups    Name        Variance Std.Dev.
 record_id (Intercept) 76.61    8.753   
 Residual              70.83    8.416   
Number of obs: 492, groups:  record_id, 31

Fixed effects:
                 Estimate Std. Error       df t value Pr(>|t|)    
(Intercept)       -1.3887     1.8255  43.7965  -0.761    0.451    
z_score_baseline  -2.3229     0.2206 450.0816 -10.528   <2e-16 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Correlation of Fixed Effects:
            (Intr)
z_scor_bsln -0.464