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The configuration, time of onset, and duration of depressed ST segments during and after treadmill exercise testing were evaluated in 269 patients with angiographically proven coronary artery disease and 141 normal subjects. The test specificity was 93% and sensitivity 64%, the latter being influenced by the type of ST response; false-positive responses were rare with depressed, downsloping STs (1 of 123, 1%), occurred more frequently with horizontal ST depression (9 of 60, 15%), and occurred commonly with slowly upsloping STs (15 of 47, 32%). Depressed downsloping STs, ischemic changes appearing in the first 3 minutes of exercise, and those persisting past 8 minutes in recovery were associated with 91%, 86%, and 90% prevalences of two- to three-vessel or main left coronary disease, respectively. It is concluded that attention to configuration, time of onset, and duration of ischemic ST depression aids both in assessing the validity of exercise responses in diagnosing coronary artery disease and in delineating patients with advanced coronary obstruction.

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Papillary muscle infarction was produced in 16 mongrel dogs by placing sutures around the base of one of the papillary muscles. In addition, patchy infarction of the adjacent left ventricular wall was produced by placing an Ameroid constrictor around the appropriate coronary artery. Mitral insufficiency developed in 14 of these animals; it was severe in four and mild to moderate in ten. Mitral insufficiency was not produced by isolated infarction of a papillary muscle or by isolated infarction of the left ventricular wall. It is concluded that papillary muscle infarction alone does not lead to mitral regurgitation, but that papillary; muscle dysfunction acts in concert with left ventricular wall dyskinesia or dilatation to produce mitral valve incompetency.

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