A 36-year-old female patient complains of general weakness, edemata of her face and hands, rapid fatiguability during walking, difficult deglutition, cardiac irregularities. These symptoms turned up 11 days after a holiday at the seaside. Objectively: face erythema, edema of shin muscles. Heart sounds are muffled, AP is 100/70 mm Hg. In blood: ASAT activity is 0,95 millimole/h-l, ALAT - 1,3 millimole/h-l, aldolase - 9,2 IU/l, creatine phosphokinase - 2,5 millimole P/g-l. What method of study would be the most specific?