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The Cardiac Physical Examination in Pregnancy
The many physiologic changes that occur in pregnancy are reflected in the cardiac physical examination. In this chapter, we note changes the practitioner should expect and the timing of those changes, with respect to respiratory rate and pattern, chest wall, lung sounds, pulse, blood pressure, jugular venous pressure, apical impulse, heart sounds, murmurs, and extremities.
Respiratory Rate and Pattern
Although minute ventilation increases in pregnancy, the change is mainly caused by an increase in tidal volume; respiratory rate does not change. The increase in tidal volume is caused by an increase in both inspiratory and ventilatory drive and is achieved chiefly by greater displacement of the rib cage.
Chest Wall
During pregnancy, the enlarging uterus increases the end-expiratory abdominal pressure, displacing the diaphragm upward by as much as 4 cm. Diaphragmatic excursion is not impaired and actually increases by up to 2 cm. The chest height becomes shorter, but the other thoracic dimensions increase, which serves to maintain constant lung capacity. During pregnancy, the thoracic cage has been reported to increase in circumference by 5 to 7 cm, and the chest diameter can increase by 2 cm. Flaring of the ribs, such that the subcostal angle increases from an average of 68 degrees to an average of 103 degrees (at term), also occurs.
Lung Sounds
The lung sounds in pregnancy remain unchanged. The presences of rales, rhonchi, or wheezes should alert the clinician to pathology.
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