NUR5203 Module 1 pathophysiology case analysis example

The Heart That Could Not Fill: Tracing a Malignant Pericardial Effusion to Cardiac Tamponade, From Pericardial Pressure to Pulsus Paradoxus

Student Name

American College of Education

NUR5203: Advanced Pathophysiology and Health Assessment

Module 1 Assignment

Instructor Name

January 11, 2028

The Case

The case is a composite drawn from the author's work as a clinical instructor on a medical oncology unit. A 61-year-old man with metastatic adenocarcinoma of the lung was admitted with two weeks of increasing breathlessness, which he and his family attributed to his cancer. On admission his blood pressure was 112/78 mm Hg and his heart rate 104. By the evening of his second day his blood pressure had fallen to 94/80 mm Hg and his heart rate had risen to 124. He could not lie flat, his neck veins were distended to the angle of the jaw while he sat upright, and his heart sounds were difficult to hear. His lungs, however, were clear. A student assigned to him reported the vital signs and added that the patient was probably getting worse because of his lung cancer. An echocardiogram later that night showed a large pericardial effusion with collapse of the right atrium and right ventricle in diastole, and pericardiocentesis removed 850 mL of bloody fluid, after which his blood pressure rose to 118/76 mm Hg.

The Normal Pericardium

The pericardium is a two-layered sac. Its inner visceral layer lies on the heart's surface, and its outer parietal layer is fibrous and relatively stiff. Between them lies a thin film of fluid, normally 15 to 50 mL, that allows the heart to move with little friction. Because the fibrous layer stretches only a little, the relationship between the volume inside the sac and the pressure inside it is not linear. Spodick (2003) describes the pericardial pressure-volume curve as flat at first, so that small additions of fluid barely raise pressure, and then abruptly steep, so that once the sac's reserve volume is used up, each further addition raises pressure sharply.

The rate at which fluid collects matters as much as the amount. When fluid accumulates over weeks, as it often does with malignancy, the pericardium stretches slowly and can accommodate a liter or more before pressure rises steeply. When fluid collects in minutes, as after trauma or cardiac perforation, as little as 100 to 200 mL can produce tamponade. The case patient's slowly growing malignant effusion explains how 850 mL could accumulate before his circulation failed.

From Pressure to Failing Output

Tamponade begins when the pressure inside the pericardium rises to equal the pressure inside the heart's chambers during filling. The heart fills only when the pressure inside a chamber is lower than the pressure of the blood arriving to fill it, and the chambers' ability to expand depends on the pressure surrounding them. As intrapericardial pressure climbs, it first matches and then compresses the thin-walled right atrium and right ventricle, the chambers with the lowest filling pressures, which is why the echocardiogram showed right-sided collapse in diastole. Eventually the pressures in all four chambers during diastole rise toward the intrapericardial pressure and become nearly equal, a hallmark of tamponade (Spodick, 2003).

With less room to fill, each chamber receives less blood, stroke volume falls and cardiac output declines. The body compensates as it does for any fall in output. Baroreceptors sense falling arterial pressure and increase sympathetic activity, which raises the heart rate and constricts peripheral arteries and veins. The rising heart rate maintains cardiac output for a time despite smaller stroke volumes, and vasoconstriction maintains blood pressure. The case patient's heart rate of 124 was the compensation working. The tachycardia was not a sign that the patient was getting worse from his cancer; it was the heart buying time against a pressure it could not overcome. When compensation is exhausted, blood pressure falls and organ perfusion fails, which is why tamponade is an emergency.

Each Finding and Its Cause

Pulsus paradoxus. Normally, systolic pressure falls slightly, by less than 10 mm Hg, during inspiration. In tamponade the fall is exaggerated. During inspiration, falling pressure in the chest draws more blood into the right ventricle. Because the pericardium cannot expand, the right ventricle can enlarge only by pushing the septum toward the left ventricle, which then fills less and ejects less, so systolic pressure falls further with each breath. This competition between the ventricles for a fixed space is called ventricular interdependence. The case patient's narrow pulse pressure of 14 mm Hg reflected his small stroke volume, and a manual measurement that evening found a pulsus paradoxus of 22 mm Hg. In a systematic review, pulsus paradoxus was present in about 82% of patients with tamponade, and among patients known to have an effusion, a pulsus paradoxus greater than 10 mm Hg raised the likelihood of tamponade while one of 10 mm Hg or less made it very unlikely (Roy et al., 2007).

Jugular venous distension. Blood returning to the right heart meets high pressure and backs up into the veins, distending the jugular veins. The same review found elevated jugular venous pressure in about three quarters of patients with tamponade, so its absence does not rule the condition out.

Muffled heart sounds. Fluid between the heart and the chest wall dampens the transmission of sound. Muffled sounds, low blood pressure and distended neck veins together form Beck's triad, which is most typical of acute tamponade and often incomplete in slowly developing effusions.

Dyspnea with clear lungs. Almost all patients with tamponade are short of breath, yet their lungs are usually clear, because the problem is not fluid in the lungs but a heart that cannot fill. The combination is itself a clue: breathlessness, distended neck veins and hypotension with clear lung fields should turn a nurse's attention to the pericardium. Current guidelines recommend echocardiography to confirm the diagnosis and urgent drainage when tamponade is present (Adler et al., 2015).

What Students Need to Be Taught

The case holds three teaching points for prelicensure students. First, a finding that does not fit the working explanation deserves attention. The student explained the patient's decline by his cancer and did not notice that clear lungs, distended neck veins and a narrowing pulse pressure did not fit a worsening lung problem. Students should be taught to ask whether every finding fits their explanation. Second, pulsus paradoxus is a skill, not a fact. It must be measured with a manual cuff, deflating slowly and noting the pressure at which sounds are first heard during expiration only and then throughout the breathing cycle. It should be demonstrated and practiced. Third, compensation hides severity. A normal blood pressure with a rising heart rate is not reassuring in a patient with a known effusion, and students should learn to read the heart rate and pulse pressure together as signs of how hard the body is working. In the author's clinical group, the case now anchors a post-conference on findings that do not fit, and the next module applies the same approach to a respiratory emergency.

References

Adler, Y., Charron, P., Imazio, M., Badano, L., Barón-Esquivias, G., Bogaert, J., Brucato, A., Gueret, P., Klingel, K., Lionis, C., Maisch, B., Mayosi, B., Pavie, A., Ristić, A. D., Sabaté Tenas, M., Seferovic, P., Swedberg, K., Tomkowski, W., & ESC Scientific Document Group. (2015). 2015 ESC guidelines for the diagnosis and management of pericardial diseases. European Heart Journal, 36(42), 2921-2964. https://doi.org/10.1093/eurheartj/ehv318

Roy, C. L., Minor, M. A., Brookhart, M. A., & Choudhry, N. K. (2007). Does this patient with a pericardial effusion have cardiac tamponade? JAMA, 297(16), 1810-1818. https://doi.org/10.1001/jama.297.16.1810

Spodick, D. H. (2003). Acute cardiac tamponade. New England Journal of Medicine, 349(7), 684-690. https://doi.org/10.1056/NEJMra022643