A 32-year-old woman comes to the office for preconception medical evaluation. She feels well, reports no health issues, and has had regular menstruations. The patient is an elite long-distance swimmer and recently retired from professional career of 10 years. She still continues to practice swimming regularly. The patient does not use tobacco, alcohol, or illicit drugs. Blood pressure is 114/66 mm Hg and pulse is 60/min. Physical examination shows no abnormalities. Compared to a person of similar age and sex with sedentary lifestyle, which of the following cardiac changes are most likely present in this patient?

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11ec160b_3ca0_dffc_9249_7510c1be066b_MD0001_00 Resting cardiac output is approximately 5 L/min and commonly increases to 15 or 20 L/min with exercise. Highly trained endurance athletes with the characteristic cardiovascular adaptations of athlete's heart can often increase their cardiac output up to 35 or 40 L/min. Maximum heart rate does not significantly increase in highly trained athletes; therefore, the increased maximum cardiac output is primarily due to increased stroke volume (cardiac output = stroke volume x heart rate). To meet the metabolic demands of frequent and intense endurance training (eg, long-distance swimming) the body gradually increases both red blood cell mass and plasma volume to increase oxygen carrying capacity. In addition, skeletal muscles develop increased arteriolar and capillary density, which improves oxygen uptake and also causes overall reduced systemic vascular resistance (SVR). Both the increased blood volume and reduced SVR contribute to increased cardiac venous return (ie, preload), which places increased volume load on the left ventricle. In response, the left ventricle undergoes eccentric hypertrophy to increase left ventricular cavity size and improve diastolic filling capacity. The resulting increase in end-diastolic volume capacity is the primary driver of the marked increase in stroke volume that occurs with endurance training (a training-induced increase in myocardial contractility also somewhat contributes). Because end-diastolic volume and stroke volume are both proportionally increased, left ventricular ejection fraction is mostly unchanged. The right ventricle also undergoes similar cavity enlargement to support the increase in maximum cardiac output. Educational objective: With endurance training, the physiologic changes of athlete's heart allow for increased maximum cardiac output via an increase in stroke volume. The left ventricle undergoes eccentric hypertrophy to increase left ventricular cavity size and improve diastolic filling capacity. The resulting increase in end-diastolic volume capacity allows for increased stroke volume and cardiac output. Because end-diastolic volume and stroke volume are both proportionally increased, left ventricular ejection fraction is mostly unchanged. __________ References: Cardiovascular adaptations to exercise training. (http://www.ncbi.nlm.nih.gov/pubmed/26756625)

A 32-Year-Old Woman Comes to the Office for Preconception Medical