This chapter defines and explains how to identify the associated electrocardiogram (EKG) changes for: pneumothorax, pleural effusion, dextrocardia pericardial, effusion infiltrative, cardiomyopathy, and pericarditis dilated cardiomyopathy hypertrophic, cardiomyopathy chronic, obstructive lung disease (COPD) and athlete’s heart. It describes possible EKG changes associated with: postoperative patients and cancer patients. Drug effects and toxicities, electrolyte imbalances, trauma, pericardial diseases, lung disease, cancer, cardiomyopathies, and systemic diseases are conditions that can cause specific changes on the EKG. A pneumothorax occurs when air seeps into the pleural space. The air interferes with the negative pressure in the pleural space and causes the lung to collapse. The air in the pleural space pushes the heart away from the chest wall and, since air is a poor conductor of electricity, it makes the waveforms on the EKG smaller. A pleural effusion is another condition that causes smaller waveforms on the EKG.