Myocardial Work in Nonobstructive Hypertrophic Cardiomyopathy: Implications for Outcome

Abstract

Background: Noninvasive left ventricular (LV) pressure-strain loop analysis is emerging as a new echocardiographic method to evaluate LV function, integrating longitudinal strain by speckle-tracking analysis and sphygmomanometrically measured blood pressure to estimate myocardial work. The aims of this study were (1) to describe global and segmental myocardial work in patients with hypertrophic cardiomyopathy (HCM), (2) to assess the correlation between myocardial work and other echocardiographic parameters, and (3) to evaluate the association of myocardial work with adverse outcomes.

Methods: One hundred ten patients with nonobstructive HCM (mean age, 55 ± 15 years; 66% men), with different phenotypes (apical, concentric, and septal hypertrophy), and 35 age- and sex-matched healthy control subjects were included. The following myocardial work indices were included: myocardial work index, constructive work (CW), wasted work, and cardiac efficiency. The combined end point included all-cause mortality, heart transplantation, heart failure hospitalization, aborted sudden cardiac death, and appropriate implantable cardioverter-defibrillator therapy.

Results: Mean global CW (1,722 ± 602 vs 2,274 ± 574 mm Hg%, P < .001), global cardiac efficiency (93% [89%-95%] vs 96% [96%-97%], P < .001), and global MWI (1,534 ± 551 vs 1,929 ± 473 mm Hg%) were significantly reduced, while global wasted work (104 mm Hg% [66-137 mm Hg%] vs 71 mm Hg% [49-92 mm Hg%], P < .001) was increased in patients with HCM compared with control subjects. Segmental impairment in CW colocalized with maximal wall thickness (HCM phenotype), and global CW correlated with LV wall thickness (r = -0.41, P < .001), diastolic function (r = -0.27, P = .001), and QRS duration (r = -0.28, P = .001). Patients with global CW > 1,730 mm Hg% (the median value) experienced better event-free survival than those with global CW < 1,730 mm Hg% (P < .001).

Conclusions: Myocardial work, assessed noninvasively using echocardiography and blood pressure measurement, is reduced in patients with nonobstructive HCM; it correlates with maximum LV wall thickness and is significantly associated with a worse long-term outcome.

Keywords: Echocardiography; Hypertrophic cardiomyopathy; Left ventricular pressure-strain loop; Myocardial work.