A 68-year-old man receiving chemotherapy for colon cancer experienced the sudden onset of chest discomfort and shortness of breath. His blood pressure is 100/75 mm Hg and his heart rate is 105 beats/min. The physical examination is unremarkable except for swelling and tenderness in the left leg, which began about 3 days earlier. The ECG shows no changes suggestive of cardiac ischemia.
1. How are the patient's chest discomfort, shortness of breath, arterial hypotension, tachycardia, and left leg symptoms explained?
2. Is right ventricular pressure likely to be increased or decreased? Why?
3. Would intravenous infusion of additional fluids (such as blood or plasma) help the patient's arterial blood pressure?
1. The patient's symptoms are caused by pulmonary embolism. In this condition, a piece of blood clot located in a peripheral vein (in this case, a leg vein) breaks off and is carried through the right heart to a pulmonary artery where it lodges. Patients with certain medical problems, including cancer, have altered clotting mechanisms and are at risk of forming these clots. When this occurs, blood flow from the pulmonary artery to the left heart is obstructed (i.e., pulmonary vascular resistance increases), resulting in elevated pulmonary arterial pressure. The sudden rise in pressure causes distension of the artery, which may contribute to the sensation of chest discomfort. Increased pulmonary arterial pressure (pulmonary hypertension) leads to right heart failure. Because left atrial (and left ventricular) filling is reduced (as a result of lack of blood flow from the lungs), left-side cardiac output also falls. The fall in cardiac output causes a reflex increase in heart rate. The result is a combination of right- and left-side heart failure, producing the signs and symptoms seen in this patient.
2. The right ventricular pressure is likely to be increased because the blood clot in the pulmonary artery acts as a form of obstruction that raises the pulmonary artery resistance.
3. The problem here is increased afterload of the right ventricle caused by partial obstruction of the outflow tract. Because of this obstructed outflow, the diastolic volume of the right ventricle is already high. It is unlikely that infusing additional fluids into the veins will improve cardiac output because the extra filling of the right ventricle is unlikely to increase the force of contraction.
Brownell WH, Anderson FA Jr. Pulmonary embolism. In:
Gloviczki P, Yao JST, eds. Handbook of Venous Disorders:
Guidelines of the American Venous Forum. London: Chapman
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