Analysis of methodology for measurement of intramyocardial pressure.

We critically evaluated the major techniques for measurement of intramyocardial pressure (IMP) (closed, perfusion, open, microtransducer). Each technique demonstrates a gradient in systolic IMP increasing with depth from the epicardium. The estimated magnitude of this gradient varies with the technique employed. Indirect methods (closed, perfusion) estimate a higher value for the systolic IMP gradient. The open and microtransducer methods, which measure a direct hydrostatic pressure within the myocardium, are less invasive and reflect more reliably the magnitude of IMP. The results for the open and microtransducer methods were comparable and indicate that normalized systolic IMP increases linearly from the epicardium. In the inner half of the myocardium systolic IMP approaches the level of systolic LVP and in the subendocardial layer it exceeds the systolic LVP by about 8%. A reverse IMP gradient occurred in late diastole ranging from 5 mmHg in the subendocardial region to 25 mmHg in the subepicardium.