Abnormal Coronary Flow Velocity Reserve and Decreased Myocardial Contractile Reserve Are Main Factors in Relation to Physical Exercise Capacity in Cardiac Amyloidosis

Abstract

The aim of the present study was to evaluate the clinical importance of echocardiographic coronary flow velocity reserve (CFVR), resting and exercise left ventricular global longitudinal strain (LVGLS), and myocardial work efficiency (MWE) in patients with cardiac amyloidosis (CA). The study population comprised 69 subjects: group A, 27 patients with CA confirmed by endomyocardial biopsy (CA positive); group B, 42 healthy control subjects. The amyloid phenotype in group A was as follows: patients with wild-type transthyretin-related amyloidosis (n=10), carriers of the Danish familial transthyretin amyloidosis mutation with cardiac involvement (n=5), and patients with amyloid light chain amyloidosis with cardiac involvement (n=12). All subjects underwent comprehensive echocardiographic evaluation during rest and during symptom-limited, semisupine exercise testing. Furthermore, CFVR was assessed using Doppler echocardiography. Patients with CA had significantly lower CFVR (1.7±0.6 vs 3.9±0.8, P<.0001), MWE (1.9±1.0 vs 3.0±0.7, P<.0001), and LVGLS magnitude (11% [10%-14%] vs 20% [18%-21%], P<.0001) than control subjects. Patients with CA showed severely reduced deformation and efficiency reserve compared with control subjects (ΔLVGLS 0.9±2.8% vs 5.6±2.3%, P<.0001; ΔMWE 2.5±2.8 vs 8.8±2.6, P<.0001). In patients with CA, a strong relation was seen between physical capacity by the metabolic equivalent of tasks test and CFVR (r=0.55, P<.01), peak exercise LVGLS (r=0.64, P<.0001), and peak exercise MWE (r=0.60, P<.01). Patients with CA had a profound lack of CFVR and longitudinal myocardial deformation reserve compared with healthy control subjects. Both parameters were significantly associated with exercise capacity and may prove useful for evaluating cardiac performance in patients with CA.