The effect of autoantibody against M2-muscarinic acetylcholine receptor in peripartum cardiomyopathy patients on digoxin additional to standard treatment

Background: To evaluate the effects of autoantibodies against the M2-muscarinic receptor (anti-M2-R) on digoxin additional to standard treatment in peripartum cardiomyopathy (PPCM) patients. Methods: 86 PPCM patients were separated into anti-M2-R negative or positive group according to the anti-M2-R reactivity. All the patients received digoxin additional to standard treatment regimen. Echocardiography was performed at baseline and after 5 years treatment. Serum digoxin concentration (SDC) were performed every 3 to 6 months. All-cause mortality, cardiovascular mortality and re-hospitalization for heart failure were compared after 5 years of follow-up. Results: There were 82 patients completed the final data analysis, including 38 in the anti-M2-R (+) group and 44 in the anti-M2-R (-) group. The heart rate of the positive group was higher than that of the negative group at baseline (102.3 ± 6.3 vs. 95.9 ± 6.8, p < 0.001). The initial SDC of patients in the positive group was higher than that of patients in the negative group with the same dose of digoxin (1.21 ± 0.41 vs. 0.73 ± 0.16 ng/mL, p < 0.001). Patients in the anti-M2-R (-) group had better tolerance to metoprolol and digoxin (p < 0.05). All the PPCM patients showed prominent improvement in cardiac function, especially in the anti-M2-R (-) group. Re-hospitalization for heart failure was decreased in the negative group, but not of all-cause or cardiovascular mortality. Conclusions: Patients negative for anti-M2-R showed better tolerance to metoprolol and digoxin. Anti-M2-R maybe a predictor for vagus nerve overactivation and is associated with poor response to digoxin treatment in PPCM patients.