Multiple in vivo full-thickness myocardial biopsies by freeze-clamping

A technique was developed to permit multiple large biopsies of the in vivo myocardium to measure certain metabolites (ATP, CP, myocardial glycogen, lactate) with minimal chance of ventricular fibrillation or severe alterations in the heart's ability to maintain BP. Adult pigs with normal hearts (n = 9) as well as with hypertrophy (n = 5) created by aortic banding 3-4 months prior were anesthetized, intubated, and ventilated. After a sternotomy, the pericardium was opened and the epicardial surface was cleared of any adhesions. Biopsies were taken from the distal to proximal end of the heart. A suture (3-O Prolene) was placed in a figure-eight pattern in the area to be biopsied. A piece of the myocardium (50-100 mg) was grasped using a pair of narrow dressing forceps and frozen in liquid nitrogen. When the sample was completely frozen, a No. 11 scalpel blade, held at a 90 degrees angle to the epicardium throughout the cut, was used to carve out the full thickness biopsy. The sample was placed immediately in liquid nitrogen. The myocardial defect was repaired by using the previously placed suture buttressed with pieces of subcutaneous fat to prevent tearing the epicardial surface. This in vivo biopsy method has negligible complications and can be repeated or taught with constant reliability.