In a 1999 article published in the journal American Journal of Clinical Nutrition, the findings were that:

High quality Hawthorn is another herb used for improving blood flow. The leaves, fruit, and flowers of the Chinese hawthorn (Crataegus pinnatifida) are widely used in Europe for improving the pumping capacity of the heart and for treating angina. Patients with chronic heart disease who were given 600 mg/d of a hawthorn extract had lower blood pressure and heart rates, and less shortness of breath, when exercising as compared with subjects not receiving hawthorn (37).

Health-promoting properties of common herbs 12 Winston J Craig
American Journal of Clinical Nutrition, Vol. 70, No. 3, 491S-499S, September 1999.

Furthermore, a study by the German Federal Ministry of Health found that the ingredients of Alistrol gently increases the strength of the heart, normalizes rhythm, and benefits circulation within the heart itself by dilating the coronary arteries. In Germany, many extracts and medicinal preparations use these ingredients alone or in combination with other herbs.

These results are important, because they imply that Alistrol's effect were not just a one-time-only 'chemical reaction' comparable to that achieved by prescription remedies. Something else must have been going on here - perhaps some positive change at a deeper physiological level.