Impact of accelerating resting heart rate in transthyretin cardiac amyloidosis on functional and hemodynamic echocardiographic parameters

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Introduction Transthyretin cardiac amyloidosis (ATTR-CM) involvement leads to diastolic heart failure and to decrease cardiac output through reduction of stroke volume and heart rate. There is a question about the impact of increasing heart rate in paced patients will improve or decrease cardiac output through reducing the LV filling time. Objective Acceleration of resting HR could improve cardiac output, hemodynamic echocardiographic parameters and the ability to perform an exercise. Method 39 ATTR-CA patients followed in the reference center, with symptomatic heart failure (NYHA II), having a resting HR < 70/min and a cardiac pacemaker were prospectively and consecutively included. A clinical examination, a 6-min walk test (6MWT), an echocardiography (TTE) with measurement of left systolic (cardiac output, LVEF, strain), diastolic function (E/E’), and asynchrony were initially performed and then during the acceleration by10 bpm increments of the heart rate (between 70 bpm and 90 bpm). The primary endpoint was defined as the optimal HR which increases CO of more than 20% without alteration of other hemodynamic parameters and thus after 5 min at the optimal heart rate a new 6MWT was performed. Results CO increased from 3.8 L/min (±SD) at baseline to 4.6(±SD) 4.9(±SD) and decrease at 4.7(±SD) respectively at 70, 80 and 90 bpm. 27 (69.2%) patients improved their CO of more ≥ 20% and their other hemodynamic parameters of whom the best hemodynamic improvement was observed at 70 bpm for 19 (70.4%) and at 80 bpm for 8 (29.6%). In responders, CO improved progressively from 26% at 70 bpm to 31% at 80 bpm. In non-responders, CO improved of 13% at 70 bpm and 21% at 80 bpm therefore patients altered their LVEF, Strain value, diastolic filling pressure or right ventricle function . In both sinus rhythm or in atrial fibrillation patients, cardiac output increases of around 20% at 70 bpm and 28% at 80 bpm from the baseline value. The mean 6MWT distance was extended by 15 (±SD) meters independently of the increase of cardiac output. Conclusion Acute increase of HR rest at 70 bpm improved the hemodynamic of ATTR-CM paced patients without impairing their diastolic function. Clinical and hemodynamic impact of long-term increase of rest heart rate needs to be assessed.

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