Thomas M Stokke1, Nina E Hasselberg2, Marit K Smedsrud3, Sebastian I Sarvari2, Kristina H Haugaa2, Otto A Smiseth1, Thor Edvardsen1, Espen W Remme4. 1. Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Center for Cardiological Innovation, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Institute for Surgical Research, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway. 2. Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Center for Cardiological Innovation, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Institute for Surgical Research, Oslo University Hospital, Rikshospitalet, Oslo, Norway. 3. Center for Cardiological Innovation, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Institute for Surgical Research, Oslo University Hospital, Rikshospitalet, Oslo, Norway. 4. Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Center for Cardiological Innovation, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Institute for Surgical Research, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway. Electronic address: espen.remme@medisin.uio.no.
Abstract
BACKGROUND: Preserved left ventricular (LV) ejection fraction (EF) and reduced myocardial strain are reported in patients with hypertrophic cardiomyopathy, ischemic heart disease, diabetes mellitus, and more. OBJECTIVES: The authors performed a combined mathematical and echocardiographic study to understand the inconsistencies between EF and strains. METHODS: An analytical equation showing the relationship between EF and the 4 parameters, global longitudinal strain (GLS), global circumferential strain (GCS), wall thickness, and short-axis diameter, was derived from an elliptical LV model. The equation was validated by measuring the 4 parameters by echocardiography in 100 subjects with EF ranging from 16% to 72% and comparing model-predicted EF with measured EF. The effect of the different parameters on EF was explored in the model and compared with findings in the patients. RESULTS: Calculated EF had very good agreement with measured EF (r = 0.95). The model showed that GCS contributes more than twice as much to EF than GLS. A significant reduction of GLS could be compensated by a small increase of GCS or wall thickness or reduced diameter. The model further demonstrated how EF can be maintained in ventricles with increased wall thickness or reduced diameter, despite reductions in both longitudinal and circumferential shortening. This was consistent with similar EF in 20 control subjects and 20 hypertrophic cardiomyopathy patients with increased wall thickness and reductions in both circumferential and longitudinal shortening (all p < 0.01). CONCLUSIONS: Reduced deformation despite preserved EF can be explained through geometric factors. Due to geometric confounders, strain better reflects systolic function in patients with preserved EF.
BACKGROUND: Preserved left ventricular (LV) ejection fraction (EF) and reduced myocardial strain are reported in patients with hypertrophic cardiomyopathy, ischemic heart disease, diabetes mellitus, and more. OBJECTIVES: The authors performed a combined mathematical and echocardiographic study to understand the inconsistencies between EF and strains. METHODS: An analytical equation showing the relationship between EF and the 4 parameters, global longitudinal strain (GLS), global circumferential strain (GCS), wall thickness, and short-axis diameter, was derived from an elliptical LV model. The equation was validated by measuring the 4 parameters by echocardiography in 100 subjects with EF ranging from 16% to 72% and comparing model-predicted EF with measured EF. The effect of the different parameters on EF was explored in the model and compared with findings in the patients. RESULTS: Calculated EF had very good agreement with measured EF (r = 0.95). The model showed that GCS contributes more than twice as much to EF than GLS. A significant reduction of GLS could be compensated by a small increase of GCS or wall thickness or reduced diameter. The model further demonstrated how EF can be maintained in ventricles with increased wall thickness or reduced diameter, despite reductions in both longitudinal and circumferential shortening. This was consistent with similar EF in 20 control subjects and 20 hypertrophic cardiomyopathypatients with increased wall thickness and reductions in both circumferential and longitudinal shortening (all p < 0.01). CONCLUSIONS: Reduced deformation despite preserved EF can be explained through geometric factors. Due to geometric confounders, strain better reflects systolic function in patients with preserved EF.
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