Strain-gauge arch recordings from an acutely ischemic area of the left ventricle.

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Abstract
In open-chest dog preparations, occlusion of the anterior descending coronary artery was instituted for 2 min. intervals at 9 consecutive occasions allowing time for recovery between each instance of occlusion. Strain-gauge arch recordings of systolic tension (ST) from the muscle area of this arterial supply were continuously monitored and, in the recovery intervals, the distance between the feet of the attached arch were successively separated by a distance of about 10% of the original length of the muscle segment using a micrometer screw attachment. At 0 stretch, the ST tracings were inverted during ischemia, and with progressive stretch the inverted trace diminished, recording no defection at 40% stretch. With further stretch, the recordings during ischemia increased in an upright direction and, at 80% stretch, the amplitude of the upright deflection was twice that of the intervening control periods. During ischemia at 80% stretch, deep myocardial incisions perpendicular to the long axis of the arch increased and parallel incisions grossly reduced the upright deflections.