A method for improving the cardiac output of a patient who is suffering from pulseless electrical activity or shock and yet still displays some myocardial wall motion including sensing myocardial activity to determine the presence of residual left ventricular pump function having a contraction or ejection phase and a filling or relaxation phase. The substrate may be a sapphire substrate that has a template layer of GaN grown on it. Respective nitride spacer elements overlying the dielectric layer are formed at each vertical sidewall. As a consequence, both surfaces of the semiconductor module can be cooled by a single coolant tube with a uniform pinching force.