The stroke volume index (SVi) appears to have greater prognostic accuracy for mortality in transthyretin amyloid cardiomyopathy (ATTR-CM) than traditional echocardiographic indexes, according to a study recently published in the Journal of Cardiovascular Medicine.
The findings align with the results of previous studies showing that SVi is a superior prognostic marker for patients with heart failure secondary to other conditions.
What is ATTR-CM?
Transthyretin amyloidosis cardiomyopathy (ATTR-CM) is a rare progressive disease of the heart muscle that leads to congestive heart failure. It occurs when the transthyretin protein produced by the liver is unstable. Symptoms include fatigue; shortness of breath; irregular heart rate or palpitations; swelling of the legs, ankles and stomach; brain fog; wheezing; and dizziness. It often goes underdiagnosed because of a lack of awareness and knowledge of the disease. There is currently no cure for ATTR-CM.
SVi was superior to left ventricular ejection fraction (LVEF), myocardial contraction fraction (MCF) and global longitudinal strain (GLS) for prognostication in patients with TTR amyloidosis, the study authors said.
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The SVi is a measure that lets physicians determine how well the heart pumps blood. It adjusts the amount of blood ejected in each pump to the patient’s size to produce more accurate results. Values below 35 ml/ml could indicate the heart is not pumping enough blood and could lead to more aggressive therapeutic measures.
The authors aimed to assess SVi’s prognostic accuracy in patients with ATTR-CM, as the tool has proven to have excellent prognostic value in patients with other forms of heart failure.
“This prospective study aimed to evaluate the role of SVi in predicting mortality and heart failure hospitalizations in patients with cardiac amyloidosis, comparing it to other parameters of left ventricular performance,” the authors said.
The study included data from 115 patients with a confirmed ATTR-CM diagnosis. The objective was to correlate mortality and hospitalization frequency with echocardiographic markers such as LVEF, GLS and SVi.
After 16 months of follow-up, there were 29 deaths and 19 hospitalizations. Results showed that SVi was superior to LVEF and GLS for predicting ATTR-CM complications and risk of death.
The results enabled the authors to establish a 35 ml/ml cut-off value for SVi; below this level, the risk of death and complications associated with ATTR-CM heart failure increases significantly.
The 0.96 hazard ratio calculated by the authors indicated that each unit increase in the SVi leads to a 4% risk of death and hospitalization due to heart failure exacerbation. The association remained significant even after adjusting for the New York Heart Association (NYHA) stage, mitral valve disease presence and disease-modifying therapy, the authors said.
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