A 42-year-old man comes to the emergency department due to fatigue and exertional dyspnea. Over the last 2 weeks his symptoms have progressively worsened to the point that he can no longer walk across his living room without becoming short of breath. He is admitted to the hospital but dies suddenly despite aggressive treatment. An autopsy is performed, and a cross-section of his heart is shown in the image below.
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This patient's symptoms were most likely caused by which of the following mechanisms?
Causes of nonvalvular heart failure | ||||
Ventricular wall thickness | Ventricular cavity size | Contractile function | Diastolic function | |
Ischemic heart disease | Normal or ↓ | ↑ | ↓ | Normal or ↓** |
Dilated cardiomyopathy* | ||||
Hypertensive heart disease | ↑ | ↓ | Normal | ↓ |
Hypertrophic cardiomyopathy* | ↑ (septal) | ↓ | Normal or ↑ | ↓ |
Restrictive cardiomyopathy* | Normal or ↑ | Normal or ↓ | Normal | ↓ |
*Cardiomyopathies involve intrinsic myocardial dysfunction. Myocardial disease caused by external factors (eg, coronary artery disease, hypertension, valvular dysfunction) is not classified as cardiomyopathy. **Although ventricular compliance is increased, diastolic dysfunction can result from elevated filling pressures. | ||||
The gross specimen of this patient's heart demonstrates left ventricular (LV) cavity enlargement consistent with eccentric hypertrophy, which is initially an adaptive mechanism that allows the LV to maintain cardiac output in the setting of increasing volume overload. Multiple disease processes can lead to eccentric hypertrophy, including ischemic heart disease, certain types of valvular disease (ie, aortic regurgitation, mitral regurgitation), and primary myocardial dysfunction (eg, due to viral infection, chronic alcohol abuse, inherited disease) manifesting as dilated cardiomyopathy.
Eventually, progressive eccentric enlargement of the LV becomes maladaptive with overwhelming wall stress leading to decreased ventricular contractility. The reduced cardiac output leads to decompensated heart failure manifesting with fatigue, dyspnea, orthopnea, and peripheral edema. The structural changes to the LV also increase the risk of ventricular arrhythmia (ie, ventricular tachycardia, ventricular fibrillation), a potential cause of sudden cardiac death in these patients.
(Choice B) Dynamic LV outflow tract (LVOT) obstruction can be seen in hypertrophic cardiomyopathy as the degree of LVOT obstruction varies with changes in LV blood volume. Maneuvers or clinical conditions that decrease LV blood volume (eg, Valsalva strain phase, dehydration) exacerbate the obstruction, whereas those that increase LV blood volume (eg, squatting) lessen or may resolve the obstruction.
(Choices C and E) Poor ventricular wall compliance leads to impaired LV filling (diastolic dysfunction). This most commonly occurs as the initial manifestation of hypertensive heart disease with pressure overload leading to concentric LV hypertrophy with thickened LV walls and a small LV cavity. Poor LV wall compliance is also typically present in restrictive cardiomyopathy, severe aortic stenosis, and hypertrophic cardiomyopathy.
(Choice D) Increased pulmonary vascular resistance can cause right heart failure due to pulmonary hypertension. There is initially right ventricular wall thickening eventually leading to right ventricular cavity enlargement as contractile function begins to fail. This patient's right ventricular wall thickness and cavity size appear normal.
Educational objective:
Dilation of the left ventricular cavity commonly occurs in response to systolic dysfunction (eg, ischemic heart disease, dilated cardiomyopathy) or certain types of valvular disease (ie, aortic regurgitation, mitral regurgitation). Chronic volume overload causes progressive eccentric hypertrophy that eventually leads to reduced ventricular contractility and decompensated heart failure.