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[Dr. Shapiro] This is Dr. Samantha Shapiro, executive editor of Harrison's Principles of Internal Medicine. Harrison's Podclass is brought to you by McGraw Hill's AccessMedicine, the online medical resource that delivers the latest trusted content from the best minds in medicine. And now onto the episode.
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[Dr. Handy] Hi everyone, welcome back to Harrison's Podclass. We're your co-hosts. I'm Dr. Cathy Handy.
[Dr. Wiener] And I'm Dr. Charlie Wiener, and we're joining you from the Johns Hopkins School of Medicine.
[Dr. Handy] Welcome to episode 109, a 28-year-old female with worsening dyspnea on exertion.
[Dr. Wiener] Okay, Cathy. Today's patient is a 28-year-old woman who's being seen in primary care clinic and reports worsening dyspnea on exertion over the last six months. She works as a high school teacher and she's noticed that while walking upstairs or uphill, she needs to rest more often than was usual. She reports no prior medical issues, she takes no medications. She uses alcohol only socially and does not use cigarettes or illicit drugs. Her family history is notable for both parents smoking extensively, she and her siblings were exposed to secondhand smoke. On physical examination, her vital signs are normal, including an oxygen saturation of 98% on room air. Her lung examination is normal. Her cardiac examination is unremarkable, except for she has a wide split second heart sound that does not vary with respiration. And I congratulate you on your good exam. There are no murmurs, rubs, or gallops. The rest of her physical examination is normal. What are you thinking and what are your next steps?
[Dr. Handy] Well, before we do that, just to clarify some of the historical information. So you said she doesn't smoke, but it sounds like has heavy exposure to secondhand smoke. And I'd also want to know if she uses oral contraceptives because of the risk of chronic pulmonary emboli, you mentioned she's a young woman. And I also want to know if she has any episodic triggers for her dyspnea besides exercise that may lead me to think about asthma.
[Dr. Wiener] She is sexually active, but she uses an intrauterine device and has never used oral contraceptives. She reports no history suggestive of reactive airways and says her only trigger for dyspnea is exercise, and as I mentioned, specifically walking up hills or stairs.
[Dr. Handy] All right, that's helpful. I'm less concerned about asthma but will still want to rule out thromboembolic disease. This can go in many directions but given her history of worsening exercise tolerance and the main finding it sounds like on exam was that fixed split S2, so I'm going to want to do some more cardiac and pulmonary testing because I'm thinking about cardiac and pulmonary issues, such as chronic pulmonary emboli, pulmonary arterial hypertension, myocardial or valvular dysfunction, or congenital heart disease, again, because she is still rather young. Let's get pulmonary function tests, a contrast CT, and then also an echocardiogram.
[Dr. Wiener] Okay, so her pulmonary function tests show normal spirometry and normal lung volumes. Her diffusion capacity is actually slightly elevated at 115% predicted. Her contrast CT shows no evidence of acute or chronic pulmonary emboli, but her right ventricle is dilated. The echocardiogram confirms the right ventricular dilation, and it also shows an atrial septal defect with left-to-right shunting on Doppler studies. The question's going to ask, if untreated, which of the following is a complication of her atrial septal defect? And the options are A. coronary artery disease; option B. is left ventricular systolic dysfunction; option C. is pulmonic stenosis; option D. is systemic hypertension; and option. E is systemic hypoxemia.
[Dr. Handy] Well, the answer is E. systemic hypoxemia but first, let's talk about atrial septal defects for a bit. This is one of those diagnoses that, if picked up early, is very treatable, but if left untreated, may be devastating for patients.
[Dr. Wiener] Okay, but first, aren't ASDs or atrial septal defects unusual to present as an adult?
[Dr. Handy] No, and that's exactly part of the point. So ASDs are a common congenital cardiac defect. Now, remember that normally, the left atrial pressure is greater than the right atrial pressure. So in the presence of a communication between the atria, blood will flow from the left to the right atrium, a so-called left-to-right shunt. The magnitude of the shunt will be based on relative resistance, pressures, propulsion, and flow patterns. Patients with large ASDs often present in childhood. However, many smaller ASDs are not discovered until adult life.
[Dr. Wiener] Why not?
[Dr. Handy] Well, because the symptoms manifest when they start to develop pulmonary hypertension and right ventricular dilation. While the mechanisms are not totally clear, the relative increased flow and shear in the pulmonary circulation leads to eventual pulmonary hypertension. And as patients age, factors like diabetes, systemic hypertension, and atherosclerosis can contribute to decreased compliance of the left-sided cardiac chambers and contribute to increased left-to-right shunting and eventual symptoms. So while our patient is presenting in her 20s, you still have to think about this diagnosis in even older adults.
[Dr. Wiener] You mentioned the abnormal S2. Is that typical, and are there ECG findings?
[Dr. Handy] Yes, the classical physical finding of an ASD with left-to-right shunting is a wide, fixed splitting of the second heart sound, which is due to prolonged RV ejection and increased PA capacitance, which in turn, delays the pulmonary valvular closure. The ECG commonly displays an incomplete right bundle branch block.
[Dr. Wiener] Great, so we still have to use our stethoscopes, I guess.
[DR. Handy] Yeah, definitely.
[Dr. Wiener] Well, the question mentioned systemic hypoxemia, but you've not mentioned that at all. Why not?
[Dr. Handy] Yeah, so that's key. So early on in the ASD, as I mentioned, the shunt is left-to-right, that's normally oxygenated blood from the left atrium is entering the right atrium, but the majority of the normally oxygenated blood goes into the left ventricle and the systemic circulation, so the patient's not hypoxemic early in the disease. It's only when the pulmonary hypertension worsens and the right ventricle fails that the right atrial pressure will elevate and be higher than the left atrial pressure. At that point, the shunt reverses and the patient develops a right-to-left shunt, so that deoxygenated blood from the right side of the heart is now entering systemic circulation. That reversal of shunt from left-to-right now becoming right-to-left shunt with the resulting hypoxemia is termed Eisenmenger physiology, and unfortunately, at that point, the disease has progressed and is very severe.
[Dr. Wiener] Can the atrial septal defect be closed if found early?
[Dr. Handy] Yeah, definitely. Right heart dilation in the setting of an unrepaired ASD is considered a risk factor for progression towards symptomatic right heart failure, atrial arrhythmias, and potential development of pulmonary arterial hypertension, if not already present. Therefore, a patient with an ASD and right heart dilation, particularly with symptoms, should be considered for ASD closure. Pulmonary vascular disease leading to pulmonary hypertension develops in up to 10% of patients with unrepaired ASDs, and these patients should be seen in a clinic that specializes in pulmonary hypertension.
[Dr. Wiener] Okay, so you've explained how, if untreated and progressive, how the ASD may lead to systemic hypoxemia or Eisenmenger physiology. I assume that the other options are not complications of an untreated ASD?
[Dr. Handy] Yes, so remember that the left ventricle, at least early in the disease, is actually relatively underfilled, so systolic heart failure is unlikely until maybe very late in the disease course. Similarly, systemic hypotension is more likely than systemic hypertension. Pulmonic stenosis is associated with Tetralogy of Fallot, which often has a ventricular septal defect, not an atrial septal defect like our patient had. And I'm not aware of an association between ASDs and coronary artery disease.
[Dr. Wiener] Great, so the teaching point of today's case is that an atrial septal defect or an ASD, when small, may present in adulthood with insidious symptoms, such as dyspnea on exertion or palpitations. You should think about this diagnosis in a patient with pulmonary hypertension or right ventricular dilation because early treatment may avoid the devastating complications, such as Eisenmenger physiology.
[Dr. Handy] And you can learn more about this in Harrison's chapter on congenital heart disease in the adult.
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[Dr. Shapiro] Thanks for listening to Harrison's Podclass. You can listen to this episode and more on AccessMedicine.com, which includes the complete Harrison's Principles of Internal Medicine text, Harrison's Review Questions, which complement and expand upon the questions in this episode, and much more. AccessMedicine.com may already be available to you via your academic institution. Check it out!
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