A comorbid disease "worsens or impacts a primary disease," according to Taber's Cyclopedic Medical Dictionary. Hypertension, or high blood pressure, already carries such a high risk of stroke that complications from additional problems adds more medications, expense and stress to a dangerous disease. The Cleveland Clinic and the Baylor College of Medicine lists heart failure, heart attack, heart disease, recurrent strokes, diabetes and chronic kidney disease as comorbidities of hypertension.
Heart failure occurs when the heart cannot pump sufficient fluid out of the heart. In the early stages of heart failure, the heart compensates by increasing the force of contractions. One of hypertension's complications is an overabundance of fluid. When these two diseases combine, the heart eventually tires from the increased workload. It slowly weakens and then fails.
Over time, hypertension decreases the elasticity of the arteries. Arteries unable to expand and contract enough to supply the proper amount of blood to the heart deprive the heart of oxygen. Reduction of the oxygen supply results in tissue death and heart attack, according to Judith Schilling McCann in the book "Cardiovascular Care."
Heart disease results from a narrowing of the arteries due to plaque deposits that latch onto arterial walls. Constriction of the blood flow through the arteries escalates hypertension.
Hypertension already increases the risk of stroke. After the first stroke, approximately 23 percent of all strokes each year are recurrent strokes, according to the American Heart Association. Existing hypertension simply raises the odds.
The ravages of diabetes include artery damage in the form of atherosclerosis, states McCann. Atherosclerosis deposits cholesterol on the inside walls of the arteries in the same manner as heart disease and, again, narrows the blood vessels, which increases blood pressure.
Chronic Kidney Disease
The kidneys regulate the fluid levels in the body, which affects blood pressure. Chronic kidney disease requires dialysis, either daily or a few times per week, says McCann. Due to the kidney's compromised ability to make urine and eliminate fluid from the body, blood pressure rises until the next dialysis treatment.