Cardiac therapy devices in the form of pacemakers and/or defibrillators including one or more leads with electrodes implanted in a vein in a posterior position in combination with one or more leads with electrodes implanted in an anterior position. The posterior position may be chosen from one or more of the azygos, hemiazygos, accessory hemiazygos, or posterior intercostal veins. The anterior position may be chosen from the internal thoracic vein, an anterior intercostal vein, or an anterior subcutaneous location. In other examples, sensors are placed for use by a cardiac monitoring or therapy system in one or more of the internal thoracic vein, the azygos vein, the hemiazygos vein, the accessory hemiazygos vein, and/or an anterior or posterior intercostal vein.