Effects of XXXX and reperfusion on cardiac cycle-dependent variation of myocardial ultrasonic backscatter.

@entity235 @entity1563 @entity63
We have recently reported a systematic variation in integrated ultrasonic backscatter throughout the cardiac cycle in @entity235 hearts. This study was performed to determine whether the pattern of such variation is modified systematically by @entity63 . Measurements of integrated ultrasonic backscatter in selected regions of normal, @entity63 , and reperfused hearts were compared in view of known differences in systolic function of myocardium in each of these regions. Integrated ultrasonic backscatter (3-7 MHz) gated to the first derivative of left ventricular pressure was measured at the apex, midwall, and base in 10 @entity235 and at the apex before and during transient @entity63 and reperfusion in four @entity235 . Quantitative integrated ultrasonic backscatter was referenced to a steel reflector. Cyclic variation of integrated ultrasonic backscatter was greatest at the apex [peak to trough variation 5.5 +/- 0.9 dB (mean +/- SE)] with the maximum near end diastole (-52.9 +/- 0.9 dB) and minimum near end systole (-58.4 +/- 1.0 dB). Variation at the apex (5.5 +/- 0.9 dB) and the midwall (4.3 +/- 0.8 dB) was greater than at the base (0.5 +/- 1.0 dB) (P less than 0.01 for either region compared with base). Left anterior descending @entity1563 for 10 minutes in four of 10 @entity235 reduced variation at the apex to 0.4 +/- 1.5 dB (P less than 0.02 compared with preocclusion). Reperfusion for 2 hours restored apical cyclic variation to 3.9 +/- 1.7 dB, i.e., to values not significantly different from those before occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)
