A 68-year-old male with a past medical history of coronary artery disease and myocardial infarction requiring three drug-eluting stents presents to the Emergency Department with exertional chest pain. He describes the pain as substernal pressure, without radiation. After his past stents, he attended cardiac rehab and he now walks a few miles per week for exercise. He does not have pain at rest, but over the past months is only able to walk a few minutes when he notices the chest pain with mild dyspnea. The pain resolves when he sits down for a few minutes. He is not able to walk more than half a mile without having significant pain. He feels this is similar to the pain he had before his stents were placed. His ECG is unchanged. His last ECG exercise stress test was 10 years ago, before his stent placements. In evaluating his pain, which of the following is the most appropriate test?
Correct Answer: C
There are numerous tests to assess cardiac perfusion. The patient in the question has a pattern of stable angina and has a history of prior revascularizations. Per the 2012 AHA/ACC guidelines for stable ischemic heart disease, the patient should proceed to nuclear imaging. The next step is to have a cardiac imaging study. The patient is able to exercise to some capacity; however, he has had prior revascularizations, therefore an imaging study would be the most appropriate. Had he not had prior revascularizations and were he able to exercise, an ECG stress test would be appropriate. A rest transthoracic echocardiogram would not provide information about myocardial perfusion. Cardiac MRI is being evaluated as a tool to evaluate myocardial perfusion in patients with ischemic heart disease but is not the test of choice currently.
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A 79-year-old female with a past medical history of rheumatoid arthritis, heart failure with reduced ejection fraction (EF 30%), and severe pulmonary hypertension presents to the Emergency Department with fever and dysuria. Vitals on arrival are notable for:
She has cool extremities, crackles, and significant lower extremity edema. Urinalysis shows significant pyuria with positive nitrite and leukocyte esterase, and significant bacteriuria, and she is started on broad spectrum antibiotics. Laboratory studies are also notable for an NT-proBNP elevated to three times of recent baseline. She is placed on oxygen and her MAP rise to 66 on three vasopressors. Echocardiogram shows a similar EF, with estimated RVSP is 92 mm Hg. Her peripheral O2 venous saturation is 93% on 4 L of nasal cannula. The intensivist decides to place a PAC via the right internal jugular vein. Due to her medical history, which among the following complications is she at the GREATEST risk for?
Correct Answer: D
The PAC is a tool that can be used to provide more information about a patient’s hemodynamics by measuring the central venous, right ventricle, pulmonary artery, and pulmonary capillary wedge pressures. Using thermodilution, the PAC can also be used to estimate the cardiac output, and this value can be used to calculate both systemic and pulmonary vascular resistances; measurement of the oxygen saturation in the pulmonary artery (mixed venous saturation) can also be used to infer cardiac output. PACs have very discrete clinical scenarios in which they can be helpful. Notably the ESCAPE trial in 2005 found that PAC placement did not improve outcomes or mortality in patients hospitalized with heart failure. However the trial was designed to exclude patients in shock (cardiogenic or mixed), in whom PAC placement may be needed urgently. In this patient with mixed septic and cardiogenic shock phenotypes, PAC might help assess type of shock and guide therapy.
There are many complications that can arise from PAC placement. The patient’s pulmonary hypertension puts her at risk for pulmonary artery rupture, a rare but severe and often fatal complication of PAC placements. Though the other choices are also possible complications, they are less likely associated with this patient’s medical history. Thromboembolism is more common in patients with a predisposing thrombophilia or suspicion for atrial clots that could be dislodged by the PAC. Complete heart block is a risk factor for patients with underlying conduction disease (typically a LBBB, which could progress to complete heart block if there was injury to the right-sided conduction system during PAC placement). Misplacement of the catheter into the LA could happen in a patient with a patent foramen ovale or an atrial septal defect.
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A 70-year-old female with a past medical history of iron-deficiency anemia, pulmonary hypertension, and diastolic heart failure presents to the Emergency Department with fever and productive cough. She has also noticed a 10 lb weight gain in the last 2 weeks. Vitals on presentation are notable for:
Her laboratory test results are notable for an NT-proBNP three times her baseline and a WBC count of 11,000 cells/µL. She is immediately started on broad spectrum antibiotics and transferred to the ICU for mixed shock. Her MAPs remain in the 50s, and she is started on pressor support with limited improvement. Her oxygenation remains poor, and she is intubated for hypoxemic respiratory failure and sedated with propofol. The decision is made to place a pulmonary artery catheter to further guide management. In interpreting her pulmonary artery catheter readings, which of the following in her presentation would lead to an INCREASE in her measured mixed venous oxygen saturation?
The oxygen saturation in the pulmonary artery is called mixed venous oxygen saturation and is measured using a pulmonary artery catheter. It is influenced by oxygen delivered to the tissue and the oxygen extracted by the tissues. Any physiologic parameter that increases the body’s metabolic rate increases tissue oxygen consumption and thereby decreases the mixed venous oxygen saturation. Thus fever and tachycardia decreases mixed venous oxygenation. Oxygen delivery to the tissues is affected by cardiac output, hemoglobin, and oxygen content of arterial blood. Anemia reduces peripheral tissue oxygen delivery and as a result decreases mixed venous oxygen saturation. Sedation with propofol reduces the body’s metabolic rate and thereby decreases tissue oxygen consumption, causing an increase in mixed venous oxygen saturation.
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