Electrical Changes in Resting, Exercise, and Holter Electrocardiography in Fabry Cardiomyopathy.

Background: In Fabry cardiomyopathy, little is known about the interaction between its key feature of myocardial replacement fibrosis and changes in resting, Holter, and exercise electrocardiography (-ECG).

Methods And Results: Resting ECG, 24-h Holter ECG, and exercise ECG were performed in 95 patients (50 women) with Fabry disease, staged using cardiac magnetic resonance imaging to measure left ventricular fibrosis. With resting ECG, T alterations were seen in patients with cardiac fibrosis, while time intervals and rhythm were unchanged (except for a longer QRS duration in patients with severe fibrosis). All patients with severe fibrosis showed T inversion, ST alteration, or both. With Holter ECG, maximum and minimum heart rate did not differ with fibrosis severity. Patients without fibrotic tissue showed less ventricular premature beats (VPB) (median 5/24 h) compared to those with mild (median 11/24 h) or severe fibrosis (median 115/24 h; P < 0.05, respectively). Fibrosis was a strong predictor of VPB burden (r  = 0.5; P < 0.001). During exercise, patients with severe fibrosis had the least increase in systolic blood pressure (sBP) (47 ± 22 mmHg vs. 62 ± 25 mmHg, P < 0.05) and the lowest maximum heart rate (113 ± 18/min; P < 0.05). Patients with mild fibrosis had a high sBP during exercise (198 ± 37 mmHg; P < 0.05). Decreased diastolic blood pressure (>10 mmHg) occurred in some patients with no (3/41) or mild fibrosis (3/34) but not in patients with severe fibrosis (0/20; P < 0.01).

Conclusions: Our data suggest that cardiac replacement fibrosis is responsible for repolarization abnormalities on resting ECG and increased VPB with Holter ECG. During exercise ECG, advanced cardiomyopathy is characterized by chronotropic incompetence with limitations on blood pressure and heart rate increase.