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Abstract
Cardiac amyloidosis is a cause of diastolic heart failure in which ejection fraction (EF) remains “normal” despite progression of disease. The myocardial contraction fraction (MCF) is an index of myocardial function, defined as stroke volume (SV) over myocardial volume (MV). We hypothesized that MCF would be superior to EF, the conventional measure of left ventricular function, in predicting survival among patients with cardiac amyloidosis. Sixty-six subjects (mean age = 67 ± 12 years; 20% women) with cardiac amyloidosis (34 with light-chain amyloid and 32 with transthyretin amyloid) underwent two-dimensional echocardiography to determine left ventricular structure and function. Cox proportional hazard modeling was used to determine the association of MCF and EF with survival. Over a mean follow-up of 1.86 ± 1.78 years (range 0.03–7.36 years), 37 subjects (56.1%) died. Mean EF of the study population was 51 ± 13%. There was no significant difference in EF between patients who survived the study period and those who died (54 ± 11% versus 49 ± 14%; p = 0.1196) while there was a significant difference in MCF (35 ± 19% versus 23 ± 10%, p = 0.0065). Using Cox proportional hazards modeling, MCF was associated with death (HR = 0.953, 95% CI of 0.932–0.984, p = 0.0031) while EF was not (HR = 0.991, 95% CI of 0.968–1.014, p = 0.4320). In a multivariate model, amyloid light-chain (AL) amyloid type was an independent risk predictor of death with a HR of 2.841 (95% CI of 1.214–6.648, p = 0.0161) along with a MCF < 30 with a HR of 2.567 (95% CI of 1.197–5.508, p = 0.0155), which was driven by a higher risk in AL subjects with a MCF < 30, HR of 3.39 (95% CI of 1.20–9.55, p = 0.021) than TTR subjects with a MCF < 30, HR of 1.26 (95% CI of 0.36–3.28, p = 0.87). In conclusion, MCF, a novel measure of myocardial chamber function, is superior to EF in predicting overall survival among patients with AL cardiac amyloidosis.
Declaration of interest
Dr Maurer received grant funding from the NIA (K24 AG 036778).
