There are many medical conditions that lead to worsening CHF and these underlying conditions contribute to a significant and potentially life-threatening loss of cardiac function. Some of these are conditions that lead to abnormal cardiac contraction and/or relaxation (e.g., coronary arterial disease, hypertension, diabetes, drug or alcohol toxicity); conditions that lead to volume or pressure overload (mitral or tricuspid valve regurgitation, hyperthyroidism); and conditions that limit ventricle filling (e.g., mitral or tricuspid valve stenosis). However, many patients have a condition of dilated cardiomyopathy, an abnormality of the heart muscle wall in which the walls of the heart become stretched and weakened, with no easily identifiable cause. Any risk factor may cause CHF, but combinations dramatically increase the risk of developing CHF.