[Cardiovascular changes during pregnancy].

Cardiovascular alterations during pregnancy are characterized by an increased vascular volume, cardiac output, and heart rate, with a marked fall in vascular resistance. Cardiac output is about 40-50% higher during the third trimester. Even higher values of cardiac output are observed during uterine contractions in labor. In general, arterial blood pressure remains unaffected or demonstrates some tendency toward lower diastolic pressure. The higher blood volume is associated with a slight increase in left ventricular dimensions. Left ventricular contraction force and its first derivative remain unchanged. Many symptoms and findings during pregnancy are caused by the described changes, such as dyspnea on exertion, presyncope due to pressure on the inferior vena cava resulting in a decreased venous return to the heart, prominent jugular venous pulsation, leg edema, and ejection murmurs over the aorta and pulmonary artery. Paroxysmal nocturnal dyspnea, anginal chest pain, syncopy, anasarca, and diastolic heart murmurs require further evaluation.