Predicting atrial fibrillation risk in hypertrophic cardiomyopathy patients: Left atrial phasic function and strain mechanics

Figures

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  Figure 1. Left atrial strain analysis. Following the R-wave with onset of ventricular systole, there is apical movement of mitral valve apparatus and enlargement of the left atrium corresponding with reservoir strain (Ɛs). In early diastole, there is emptying of the left atrium corresponding with the E-wave and conduit strain (Ɛe). Finally, atrial contraction corresponding to the A-wave is represented as booster strain (Ɛa). As demonstrated, the strain values are lower in patients with hypertrophic cardiomyopathy with atrial fibrillation, compared to those without atrial fibrillation, and this pattern is more prominent in booster function (Ɛa; 5.76 vs 11.41, P < 0.001).

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  Figure 2. Left atrial (LA) mechanics. Following the R-wave with onset of ventricular systole, there is apical movement of the mitral valve apparatus and enlargement of the left atrium (peak positive wave) corresponding with reservoir strain rate (SRs). In early diastole, there is emptying of the left atrium (peak early negative wave) corresponding with conduit strain rate (SRe). Finally, atrial contraction occurs, represented as a peak late negative wave corresponding with booster strain rate (SRa). The strain rate values are lower in patients with atrial fibrillation. Peak late negative strain rate (SRa), which corresponds to LA booster function, is significantly lower (SRa; –0.32 vs –1.11, P < 0.001). However, there is no significant difference in the peak early negative strain rate which corresponds to the LA conduit function (SRe; –0.71 vs –0.65, P = 0.418).

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  Figure 3. A time-volume curve; LAVmax, maximal left atrial (LA) volume at left ventricular (LV) end-systole; LAV pre-A is the LA volume at LV diastole before LA contraction; LAV minimum is the minimal LA volume at LV end-diastole, demonstrating higher volumes in all 3 phases of LA function in patients with hypertrophic cardiomyopathy with atrial fibrillation. Although the volumes appear to rise and fall in parallel, the differences in strain and strain rate are better demonstrated in Figure 2, due to differences in starting and emptying volumes.

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  Figure 4. Kaplan–Meier curve demonstrating time to event for patients with hypertrophic cardiomyopathy using total left atrial ejection fraction (LAEF). The multivariate logistic regression showed that the lower the left atrial ejection fraction, the greater the possibility of developing atrial fibrillation in the future. The LAEF cutoff for developing atrial fibrillation in this study was 36.5%.

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  Figure 5. Kaplan–Meier curve demonstrating time to event for patients with hypertrophic cardiomyopathy using left atrial (LA) booster strain. The multivariate logistic regression showed that the lower the LA booster strain, the greater the possibility of developing atrial fibrillation in the future. The LA booster strain cutoff for developing atrial fibrillation in this study was 7.6%.