NR 507 Week 3 Heart Failure Mechanism Analysis Example

From Infarcted Myocardium to Bilateral Crackles: A Mechanism Analysis of Decompensated Heart Failure With Reduced Ejection Fraction

[Author Name]

College of Nursing, Chamberlain University

NR 507 Advanced Pathophysiology

Week 3 Assignment

[Faculty Name]

August 11, 2026

The patient in this paper is a composite written as a model document. No real person or record is described.

The Case: Ten Days of Weight Gain in a 62-Year-Old Man With an Ejection Fraction of 30 Percent

A 62-year-old man with ischemic cardiomyopathy comes to a primary care clinic because his home scale has climbed from 88.0 kg to 94.4 kg in ten days. He had an anterior myocardial infarction four years ago, and an echocardiogram five months ago showed a left ventricular ejection fraction of 30 percent with a dilated left ventricle. He now sleeps on three pillows rather than one, has woken twice this week gasping about two hours after falling asleep, and becomes short of breath after roughly 20 meters on flat ground, where a month ago he walked four blocks. His torsemide ran out two weeks ago and was not refilled, and he reports eating canned soup most evenings.

On examination the blood pressure is 104/68 mm Hg, giving a pulse pressure of 36 mm Hg, the heart rate is 98 beats per minute and regular, the respiratory rate is 22 breaths per minute, and oxygen saturation is 93 percent on room air. Jugular venous pressure measures 12 cm of water at 45 degrees, and pressure over the right upper quadrant raises it further. An S3 gallop is audible at the apex with the bell in the left lateral position. Crackles are heard from the bases to the mid-lung fields bilaterally. Pitting edema is 3+ to mid-shin, and the liver edge is palpable 3 cm below the costal margin and tender.

Laboratory and imaging data complete the picture. N-terminal pro-B-type natriuretic peptide is 4,800 pg/mL against a stable outpatient value of 900 pg/mL six months ago. Serum sodium is 132 mmol/L, potassium 4.2 mmol/L, and creatinine 1.6 mg/dL against a baseline of 1.1 mg/dL, giving an estimated glomerular filtration rate of 44 mL/min/1.73 m2. The chest radiograph shows upper lobe vascular redistribution, Kerley B lines and small bilateral pleural effusions. The question this paper answers is not what to call the syndrome, which is plain, but how one infarct four years ago produces this exact set of findings in this exact order.

The Mechanism: Lost Contractile Tissue, Then Compensation That Turns on the Heart

The sequence starts with tissue that no longer contracts. Coronary occlusion four years ago killed a segment of anterior wall myocardium, and because adult cardiac myocytes do not regenerate in meaningful numbers, the infarcted region healed as noncontractile collagen scar. The ventricle that remains cannot generate the same stroke volume at any given end-diastolic volume, so the ejection fraction falls to 30 percent and cardiac output falls with it. Arterial baroreceptors in the carotid sinus and aortic arch sense the reduced stretch of a poorly filled arterial tree. What follows is not a disease process invented by the failing heart; it is the body's ordinary response to hemorrhage or dehydration, switched on permanently in a setting where it cannot help.

Baroreceptor unloading releases the brake on sympathetic outflow. Circulating norepinephrine rises, beta-1 stimulation raises heart rate and the contractility of surviving myocytes, and alpha-1 stimulation constricts arterioles to defend perfusion pressure and constricts veins to shift blood from the venous reservoir back toward the heart. Each of these buys minutes and costs years. Faster rates shorten diastole, which is when coronary perfusion occurs, so the surviving myocardium works harder on a smaller supply. Higher afterload from arteriolar constriction opposes ejection from a ventricle that is already failing to eject. Sustained catecholamine exposure is directly toxic to myocytes and drives apoptosis, which subtracts still more contractile tissue.

Reduced renal perfusion and beta-1 stimulation of juxtaglomerular cells together trigger renin release, and the renin-angiotensin-aldosterone system amplifies everything the sympathetic system began. Angiotensin II constricts arterioles, stimulates thirst, and increases proximal tubular sodium reabsorption. Aldosterone drives sodium and water reabsorption in the distal nephron and collecting duct, and it also promotes fibrosis in the myocardium and vasculature. Low arterial filling triggers nonosmotic release of antidiuretic hormone, so free water is retained out of proportion to sodium. The kidney behaves as though the patient is bleeding, retaining salt and water into a circulation that is already overfilled.

Retained volume meets a ventricle that can no longer use it. On a normal Frank-Starling curve, added preload stretches sarcomeres and increases stroke volume. In a dilated failing ventricle the curve is flattened, so additional volume raises end-diastolic pressure without raising output. Chronic volume and pressure overload also remodel the chamber: myocytes elongate, the cavity dilates eccentrically, wall stress rises by the law of Laplace as the radius grows, and the geometry that results ejects less efficiently than the one it replaced. Stretched atrial and ventricular myocardium releases natriuretic peptides, a counter-regulatory signal that promotes sodium excretion and vasodilation but is overwhelmed by the systems opposing it.

Where the Mechanism Becomes This Patient's Findings

The 6.4 kg gained in ten days is close to 6.4 liters of retained fluid, and it is the direct output of the sodium retention described above, accelerated by two weeks without a loop diuretic and by an evening sodium load. Rising left ventricular end-diastolic pressure transmits backward to the left atrium and the pulmonary veins. When pulmonary capillary hydrostatic pressure exceeds plasma oncotic pressure, Starling forces at the capillary membrane favor filtration into the interstitium, and once lymphatic drainage is exceeded, fluid enters the alveoli. The crackles heard to the mid-lung fields are small airways and alveoli popping open against that fluid; the tachypnea and the saturation of 93 percent follow from impaired diffusion and ventilation-perfusion mismatch.

Position explains the rest of the respiratory history. Lying flat returns roughly 500 mL of blood from the splanchnic bed and legs to the thorax, and a ventricle on a flat Starling curve converts that preload into pressure rather than output, so the patient needs three pillows to stay comfortable. Waking two hours into sleep, gasping, follows the same physics with a delay: interstitial fluid from the legs is reabsorbed slowly through the night, sympathetic tone falls during sleep, and the accumulated volume finally exceeds what the left ventricle can hold at a tolerable pressure. The S3 gallop is the sound of rapid early diastolic filling striking a dilated, poorly compliant chamber.

The right side of the circulation carries the same pressure with its own signs. Sustained pulmonary venous congestion raises pulmonary arterial pressure, which is afterload for the right ventricle, and a right ventricle working against it eventually dilates and fails as well. Systemic venous pressure then rises, which is what the jugular venous pressure of 12 cm of water measures directly, and what the positive hepatojugular response confirms when abdominal pressure delivers extra volume the right heart cannot accept. The tender liver edge is hepatic congestion. The 3+ dependent edema is the same Starling imbalance seen in the lungs, occurring in tissue where gravity raises capillary hydrostatic pressure most.

The laboratory values report on the neurohormonal state rather than on any separate disease. Sodium of 132 mmol/L reflects antidiuretic hormone driven free water retention, so this hyponatremia is dilutional and marks how strongly the compensations are switched on. Creatinine of 1.6 mg/dL rises from both directions: forward flow to the glomerulus is reduced, and venous congestion raises renal interstitial and venous pressure, which lowers the net filtration gradient. N-terminal pro-B-type natriuretic peptide of 4,800 pg/mL is a wall stress readout, which is why it tracks decompensation rather than diagnosis. Read this way, the standard drug classes for this syndrome are recognizable as blockade of the compensations, not as symptom control.

References

American Heart Association. (2023). Types of heart failure. https://www.heart.org

Centers for Disease Control and Prevention. (2024). Heart failure. U.S. Department of Health and Human Services. https://www.cdc.gov/heart-disease/

Hall, J. E., & Hall, M. E. (2021). Guyton and Hall textbook of medical physiology (14th ed.). Elsevier.

Heidenreich, P. A., Bozkurt, B., Aguilar, D., Allen, L. A., Byun, J. J., Colvin, M. M., Deswal, A., Drazner, M. H., Dunlay, S. M., Evers, L. R., Fang, J. C., Fedson, S. E., Fonarow, G. C., Hayek, S. S., Hernandez, A. F., Khazanie, P., Kittleson, M. M., Lee, C. S., Link, M. S., ... Yancy, C. W. (2022). 2022 AHA/ACC/HFSA guideline for the management of heart failure: A report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation, 145(18), e895-e1032. https://doi.org/10.1161/CIR.0000000000001063

National Heart, Lung, and Blood Institute. (2022). Heart failure. U.S. Department of Health and Human Services, National Institutes of Health. https://www.nhlbi.nih.gov

Rogers, J. L. (Ed.). (2023). McCance and Huether's pathophysiology: The biologic basis for disease in adults and children (9th ed.). Elsevier.