Associations between perfusion defects, tissue changes and myocardial deformation in hypertrophic cardiomyopathy, uncovered by a cardiac magnetic resonance segmental analysis

Microvascular dysfunction is an often overlooked feature of hypertrophic cardiomyopathy (HCM). Our aim was to assess the association between microvascular dysfunction, wall thickness, tissue characteristics and myocardial deformation in HCM patients, by analyzing individual myocardial segments. Prospective assessment including cardiac magnetic resonance to assess wall thickness, T1 and T2 mapping, extracellular volume, late gadolinium enhancement (LGE) and stress perfusion. Results were stratified according to the 16 American Heart Association segments. Seventy-five patients were recruited (1200 segments), 63% male, mean age 54.6±14.8 years, maximal wall thickness of 20.22±4.6 mm. Among the 424 segments (35%) with perfusion defects, 24% had defects only in the endocardial layer and 12% in both endocardial and epicardial layers. Perfusion defects were more often detected in hypertrophied segments (64%). Among the 660 segments with normal wall thickness, 19% presented perfusion defects. Independently of wall thickness, segments with perfusion defects had a higher T1 (β-estimate 30.28, p<0.001), extracelluar volume (β-estimate 1.50, p<0.001) and T2 (β-estimate 0.73, p<0.001) and had late gadolinium enhancement more frequently (odds ratio 4.16, p<0.001). Higher values of circumferential strain (lower deformation) and lower values of radial strain were found in segments with perfusion defects (β-estimate 2.76, p<0.001; and β-estimate -10.39, p<0.001, circumferential and radial strain, respectively). While microvascular dysfunction was more prevalent in more hypertrophied segments, it also had a major presence in segments without hypertrophy. In this segmental analysis, we found an association between the presence of ischemia and tissue abnormalities, replacement fibrosis as well as impaired strain, independently of the segmental wall thickness. A disfunção microvascular é uma característica frequentemente subestimada da miocardiopatia hipertrófica (MCH). O objetivo do estudo foi avaliar a associação entre disfunção microvascular, espessura da parede (EP), características tecidulares e deformação miocárdica na MCH, analisando os segmentos miocárdicos individualmente. Estudo prospetivo incluindo ressonância magnética cardíaca para avaliação de EP, T1 e T2 mapping, volume extracelular (VEC), realce tardio (RT) e estudo de perfusão, estratificados de acordo com os 16 segmentos da American Heart Association. Foram recrutados 75 doentes (1.200 segmentos), 63% do sexo masculino, idade média 54,6±14,8 anos e EP máxima de 20,22±4,6 mm. Dentro dos 424 segmentos (35%) com defeitos de perfusão, 24% apresentaram defeitos apenas no endocárdio e 12% apresentaram defeitos tanto no endocárdio como no epicárdio. Os defeitos de perfusão foram detetados maioritariamente nos segmentos hipertrofiados (64%). Dentro dos 660 segmentos com EP normal, 19% apresentaram defeitos de perfusão. Independentemente da EP, os segmentos com defeitos de perfusão apresentaram maior elevação de T1 (β-estimate 30,28, p<0,001), VEC (β-estimate 1,50, p<0,001) e T2 (β-estimate 0,73, p<0,001) e RT com maior frequência (OR 4,16, p<0,001). Os segmentos com defeitos de perfusão apresentaram valores mais elevados de strain circunferencial (menor deformação) (β-estimate 2,76, p<0,001) e valores mais reduzidos de strain radial (β-estimate -10,39, p<0,001). Embora a disfunção microvascular tenha sido mais prevalente nos segmentos mais hipertrofiados, esta estava significativamente presente em segmentos sem hipertrofia. Nesta análise segmentar revelamos uma associação entre a presença de isquémia e características tecidulares, fibrose de substituição e strain anormal, independentemente da espessura da parede.