In this study two new indexes that measure the upward and downward slopes of the QRS complex are proposed to quantify variations in the depolarization period due to induced ischemia during percutaneous transluminal coronary angioplasty. Our results show that QRS slopes turn out to be substantially less steep during artery occlusion, being this effect more manifested for the downward slope than for the upward one. Comparing the proposed indexes with a previously reported index that quantifies the energy of the high-frequency QRS signal (150-250 Hz), it is shown that the ability of the slope indexes for ischemia detection is clearly superior. When comparing with the conventional ST level, enhanced performance of the proposed indexes is only found in some leads. It can be concluded that diminution of QRS slopes can be used as an additional tool, alternative to HF-QRS content, to ST deviation when diagnosing ischemia