Cardiovascular Changes in Normal Pregnancy

Physiologic Basis

• The American College of Cardiology/American Heart Association (ACC/AHA) guidelines state that a normal pregnant woman's physical examination may include a louder than normal first heart sound with prominent splitting, due to hemodynamic changes of pregnancy, including a 50% increase in circulating blood volume, increased cardiac output, increased stroke volume, and heart rate elevation 1, 2, 3, 4
• The ACC/AHA guidelines describe the expected cardiovascular changes in normal pregnancy, including increased cardiac output peaking between mid-second and third trimesters, and increased stroke volume and heart rate (10-20 bpm elevation) 1, 2
• A hyperkinetic precordial impulse is a normal finding in pregnancy, according to the ACC/AHA guidelines 1, 2, 3, 4

Normal Cardiac Findings

• Physiologically split S2 (which may widen and appear fixed in later pregnancy) is a normal finding in pregnancy, as described by the ACC/AHA guidelines 1, 2, 3, 4
• Third heart sounds (S3) are present in most patients during pregnancy, according to the ACC/AHA guidelines 1, 2, 3, 4
• A soft grade 1-2 midsystolic murmur at mid to upper left sternal edge is a normal finding in pregnancy, as described by the ACC/AHA guidelines 1, 2, 3, 4
• Continuous murmurs (venous hum or mammary souffle) are normal findings in pregnancy, according to the ACC/AHA guidelines 1, 2, 3, 4

Concerning Features

• Diastolic murmurs are unusual in normal pregnancy and would require further evaluation, as stated by the ACC/AHA guidelines 1, 2, 3, 4
• New symptoms (dyspnea beyond normal pregnancy, chest pain, syncope) would warrant reevaluation 2
• Signs of heart failure would require further evaluation 2
• Known structural heart disease requiring monitoring per guidelines would warrant further evaluation 1, 3, 4

Physiologic Murmur of Pregnancy

Clinical Presentation and Diagnosis

• The American College of Cardiology recommends that grade 1-2 midsystolic murmurs in asymptomatic young adults with otherwise normal cardiac examination typically do not require extensive workup 5, 6
• The absence of symptoms in a 26-year-old woman at 30 weeks gestation strongly favors a benign etiology, such as a physiologic murmur of pregnancy 5, 6
• Congenital aortic stenosis severe enough to cause a murmur would almost certainly have been diagnosed before age 26, especially in a woman who has reached 30 weeks of pregnancy without symptoms 7
• Significant aortic stenosis causes symptoms during pregnancy due to the fixed cardiac output state being unable to meet increased hemodynamic demands 7

Management Approach

• The American College of Cardiology/American Heart Association guidelines specifically note that innocent murmurs are especially common in high-output states such as pregnancy, and extensive workup is not necessary for grade 1-2 midsystolic murmurs in asymptomatic young adults with otherwise normal cardiac examination 5, 6
• Echocardiography would be warranted if any of the following were present: grade 3 or greater intensity murmur, any diastolic murmur, symptoms such as dyspnea or chest pain, or abnormal dynamic auscultation 5, 6
• The American College of Cardiology recommends that mitral stenosis, which produces a diastolic murmur, and tricuspid stenosis, which is exceedingly rare and also produces a diastolic murmur, be considered in the differential diagnosis 5