Viability of hypokinetic segments: Influence of tethering from adjacent segments

Hypokinetic myocardium is presumed to be reversibly dysfunctional. However, hypokinetic segments do not necessarily improve after revascularization since their outcome can be influenced by tethering effects of adjacent myocardium. To assess whether hypokinetic segments improve following revascularization, 24 patients underwent resting and dobutamine stress echocardiography (DSE), with a total of 420 (20 per patient) myocardial segments studied pre- and postrevascularization. One hundred fifty-five hypokinetic segments were identified prerevascularization. Postrevascularization, only 57% of these segments improved in wall motion, while 43% showed no improvement or worsening of wall motion. Low dose (5-10 μg/kg/min) DSE identified correctly 57 (65%) of 88 segments that improved, and falsely predicted improvement in 26 (39%) of 67 segments that ultimately did not improve postrevascularization. Of the hypokinetic segments that did not improve, 90% were adjacent to at least one severely hypokinetic or akinetic segment as compared with 73% of the segments that improved following revascularization (P = 0.009). Sixty-five percent of all true positive DSE responses were adjacent to at least one akinetic or severely hypokinetic segment, while 87% of all false negative DSE responses were adjacent to at least one akinetic or severely hypokinetic segment (P = 0.03). In conclusion, myocardial segments found to be hypokinetic do not necessarily improve after revascularization. This may be related to tethering influences of adjacent segments, which have a contrasting level of function.