A 36-year-old female patient complains about general weakness, edemata of her face and hands, rapid fatigability during walking, difficult deglutition, cardiac irregularities. These symptoms turned up 11 days after 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 micromole/h-l, aldolase - 9,2 IU/l, creatine phosphokinase - 2,5 micromole P/g-l. What method of study would be the most specific?