Myocardial Oxygen Consumption and Efficiency in Patients With Cardiac Amyloidosis

Abstract

Background This study evaluated myocardial oxygen consumption (MVO 2 ) and myocardial external efficiency (MEE) in patients with cardiac amyloidosis (CA). Furthermore, we compared MEE and MVO 2 in subjects with light chain amyloidosis versus transthyretin (ATTR) amyloidosis. Methods and Results The study population comprised 40 subjects: 25 patients with confirmed CA and 15 control subjects. All subjects underwent an 11 C‐acetate positron emission tomography. Furthermore, the CA patients underwent comprehensive echocardiography and right heart catheterization during a symptom‐limited, semi‐supine exercise test. MEE was calculated from 11 C‐acetate positron emission tomography as the ratio of left ventricular (LV) stroke work and the energy equivalent of MVO 2 . Myocardial work efficiency was calculated as echocardiography‐derived work pressure product divided by three‐dimensional LV mass. CA patients had significantly lower LV‐ejection fraction (54±13% versus 63±4%, P <0.05) and LV‐global longitudinal strain (LVGLS) (12±4% versus 19±2%, P <0.0001) and a more restrictive filling pattern (E/e′‐ratio 18 [12–25] versus 8 [7–9], P <0.0001) than controls. MEE was severely reduced (13±5% versus 22±5%, P <0.0001) whereas total MVO 2 was higher (18±6 mL/min versus 13±3 mL/min, P <0.01) in CA patients than controls. MEE decreased with increasing New York Heart Association symptom burden ( P <0.0001). We found a good relationship between MEE and peak exercise systolic performance (LVGLS: R 2 =0.60, P <0.0001; myocardial work efficiency: R 2 =0.48, P <0.0001; cardiac index: R 2 =0.52, P <0.0001) and between MEE and myocardial blood flow ( R 2 =0.44, P <0.0001). Conclusion Myocardial oxidative metabolism is disturbed in CA patients with increased total MVO 2 and reduced MEE. MEE correlated significantly with echocardiographic derived systolic parameters such as myocardial work efficiency and LVGLS that might be used as surrogate MEE markers.

Myocardial work in hypertensive patients with and without diabetes: An echocardiographic study

“…This method has been used in patients with heart failure and prediction of response to cardiac resynchronization therapy, as well as in patients with confirmed or suspected coronary artery disease 6‐9 . Clemmensen et al 10 reported significant correlation between echocardiography‐derived myocardial work and myocardial external efficiency evaluated by positron emission tomography in patients with cardiac amyloidosis, which supports use of echocardiography in evaluation of myocardial work and confirms that cardiac catheterization is not the only adequate method for assessment of myocardial work.…”

JCS 2020 Guideline on Diagnosis and Treatment of Cardiac Amyloidosis

“…309,330 Moreover, it has been reported that differences in strain values between LV apex and basal increased by using exercise stress echocardiography, and this difference in strain values was related to symptoms in patients with CA (e.g., NYHA class, metabolic equivalents at peak exercise, maximum V O2). 331 Apical sparing is observed both in patients with ATTR amyloidosis and in those with AL amyloidosis. However, the strain value at the LV apex in patients with ATTR amyloidosis has been shown to be lower than that in patients with AL amyloidosis.…”

Diagnostic and Prognostic Values of Cardiopulmonary Exercise Testing in Cardiac Amyloidosis

“…The link between impaired exercise capacity and central hemodynamic alterations has been extensively studied in patients with CA ( 9 – 12 ). Typically, CA is predominantly considered a diastolic disease caused by increased myocardial stiffness and restrictive heart wall chamber behavior ( 9 ).…”

“…Typically, CA is predominantly considered a diastolic disease caused by increased myocardial stiffness and restrictive heart wall chamber behavior ( 9 ). Recent studies have also underlined a profound lack of myocardial contractile reserve and coronary flow velocity reserve ( 10 – 12 ). A blunt increase in stroke volume during exercise has been attributed to this decreased contractile reserve, rather than changes in preload and afterload ( 10 ).…”