The relationship between carotid blood-flow velocity and the left ventricular area during acute regional ischemia

Abstract

Objective: Myocardial contractility can be described by the relationship between blood-flow velocity in the carotid artery and the left ventricular cross-sectional area. The authors investigated whether critical myocardial ischemia influences the derived contractility index, E'(es).

Design: A prospective animal study.

Setting: A university research laboratory.

Participants: Eleven Göttinger minipigs.

Interventions: Within the closed-chest model, the authors placed a U-shaped 8-MHz miniature Doppler probe around the left internal carotid artery and inserted a combined pressure-conductance catheter into the left ventricular cavity via the right internal carotid artery. A balloon occlusion catheter was placed into the inferior caval vein from a femoral vein and acquired transthoracic-view echocardiographic images. An active coronary perfusion catheter was positioned in the proximal left circumflex coronary (LCx) artery. The LCx bed was perfused with blood from the contralateral femoral artery by using a high-precision-output roller pump.

Measurements and main results: Stage analysis during normal perfusion revealed evidence for the following function: E'(es) = 0.066 + 0.121 E(es) (R = 0.96, R(2) = 0.92, and p < 0.0001), which agrees with previously determined equations. Under ischemic conditions, the relationship changed to E'(es) = 0.048 + 0.196.E(es) (R = 0.83, R(2) = 0.69, and p < 0.0001). The limits of precision to detect changes in contractility by E'(es) increased from 16% to 45%; the bias did not notably deviate from zero. The indexes of mechanical dyssynchrony (mechanical dyssynchrony and internal flow fraction) derived from conductance catheter measurements increased significantly.

Conclusion: The ability of E'(es) to indicate contractility during acute reduced coronary blood flow is limited.