An interesting article showing the connection between berberine and congestive heart failure. Note the importance of a good quality supplement in order to achieve relevant blood levels. Here is a portion of the abstract from the study:

It has been reported that berberine is valuable for long-term treatment of ventricular premature beats (VPBs) and leads to a decrease in mortality for patients with congestive heart failure (CHF). In order to improve its therapeutic value and reduce its side effects, it is necessary to study the relationship between its activity and plasma concentration in patients with CHF. Patients with CHF were treated with conventional therapy for 2 weeks. Immediately after the data from a dynamic electrocardiogram (DCG) and left ventricular ejection fraction (LVEF) were obtained, 1.2 g/day of oral berberine was given. After 2 weeks of berberine therapy, the DCG data and LVEF were reassessed and the plasma berberine concentration was measured by HPLC. Plasma samples were pretreated by extraction with chloroform. The decrease in frequency and complexity of VPBs and the increase in LVEF in patients with plasma berberine concentrations higher than 0.11 mg/L (n = 31, group B) were more significant than at concentrations lower than 0.11 mg/L (p < 0.01 vs p < 0.05).

Xiangji et al, Relationship between the clinical effects of berberine on severe congestive heart failure and its concentration in plasma studied by HPLC, Biomed. Chromatogr. 13: 442–444 (1999)